;;; mh-search  ---  MH-Search mode

;; Copyright (C) 1993, 1995, 2001-2020 Free Software Foundation, Inc.

;; Author: Indexed search by Satyaki Das <satyaki@theforce.stanford.edu>
;; Maintainer: Bill Wohler <wohler@newt.com>
;; Keywords: mail
;; See: mh-e.el

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Mode used to compose search criteria.

;;  (1) The following search engines are supported:
;;        swish++
;;        swish-e
;;        mairix
;;        namazu
;;        pick
;;        grep

;;  (2) To use this package, you first have to build an index. Please
;;      read the documentation for `mh-search' to get started. That
;;      documentation will direct you to the specific instructions for
;;      your particular searcher.

;;; Change Log:

;;; Code:

(require 'mh-e)

(require 'gnus-util)
(require 'imenu)

(defvar mh-searcher nil
  "Cached value of chosen search program.")

(defvar mh-search-function nil
  "Function which executes the search program.")

(defvar mh-search-next-result-function nil
  "Function to parse the next line of output.
Expected to return a list of three strings: name of the folder,
message number, and optionally the match.")

(defvar mh-search-regexp-builder nil
  "Function used to construct search regexp.")

(defvar mh-index-folder "+mhe-index"
  "Folder that contains the folders resulting from the index searches.")

(defvar mh-flists-results-folder "sequence"
  "Subfolder for `mh-index-folder' where flists output is placed.")

(defvar mh-flists-sequence)

(defvar mh-flists-called-flag nil)



;;; MH-Folder Commands

;;;###mh-autoload
(defun mh-search (folder search-regexp
                         &optional redo-search-flag window-config)
  "Search your MH mail.

This command helps you find messages in your entire corpus of
mail. You can search for messages to or from a particular person
or about a particular subject. In fact, you can also search for
messages containing selected strings in any arbitrary header
field or any string found within the messages.

Out of the box, MH-E uses \"pick\" to find messages. With a
little extra effort, you can set an indexing program which
rewards you with extremely quick results. The drawback is that
sometimes the index does not contain the words you're looking
for. You can still use \"pick\" in these situations.

You are prompted for the FOLDER to search. This can be \"all\" to
search all folders. Note that the search works recursively on the
listed folder.

Next, an MH-Search buffer appears where you can enter search
criteria SEARCH-REGEXP.

     From:
     To:
     Cc:
     Date:
     Subject:
     --------

Edit this template by entering your search criteria in an
appropriate header field that is already there, or create a new
field yourself. If the string you're looking for could be
anywhere in a message, then place the string underneath the row
of dashes.

As an example, let's say that we want to find messages from
Ginnean about horseback riding in the Kosciusko National
Park (Australia) during January, 1994. Normally we would start
with a broad search and narrow it down if necessary to produce a
manageable amount of data, but we'll cut to the chase and create
a fairly restrictive set of criteria as follows:\\<mh-search-mode-map>

     From: ginnean
     To:
     Cc:
     Date: Jan 1994
     Subject:
     --------
     horse
     kosciusko

As with MH-Letter mode, MH-Search provides commands like
\\[mh-to-field] to help you fill in the blanks.\\<mh-folder-mode-map>

If you find that you do the same thing over and over when editing
the search template, you may wish to bind some shortcuts to keys.
This can be done with the variable `mh-search-mode-hook', which is
called when \\[mh-search] is run on a new pattern.\\<mh-search-mode-map>

To perform the search, type \\[mh-index-do-search].

Sometimes you're searching for text that is either not indexed,
or hasn't been indexed yet. In this case you can override the
default method with the pick method by running the command
\\[mh-pick-do-search].

The messages that are found are put in a temporary sub-folder of
\"+mhe-index\" and are displayed in an MH-Folder buffer. This
buffer is special because it displays messages from multiple
folders; each set of messages from a given folder has a heading
with the folder name.\\<mh-folder-mode-map>

The appearance of the heading can be modified by customizing the
face `mh-search-folder'. You can jump back and forth between the
headings using the commands \\[mh-index-next-folder] and
\\[mh-index-previous-folder].

In addition, the command \\[mh-index-visit-folder] can be used to
visit the folder of the message at point. Initially, only the
messages that matched the search criteria are displayed in the
folder. While the temporary buffer has its own set of message
numbers, the actual messages numbers are shown in the visited
folder. Thus, the command \\[mh-index-visit-folder] is useful to
find the actual message number of an interesting message, or to
view surrounding messages with the command \\[mh-rescan-folder].

Because this folder is temporary, you'll probably get in the
habit of killing it when you're done with \\[mh-kill-folder].

You can regenerate the results by running this command with a
prefix argument REDO-SEARCH-FLAG.

Note: This command uses an \"X-MHE-Checksum:\" header field to
cache the MD5 checksum of a message. This means that if an
incoming message already contains an \"X-MHE-Checksum:\" field,
that message might not be found by this command. The following
\"procmail\" recipe avoids this problem by renaming the existing
header field:

     :0 wf
     | formail -R \"X-MHE-Checksum\" \"X-Old-MHE-Checksum\"

Configuring Indexed Searches

The command \\[mh-search] runs the command defined by the option
`mh-search-program'. The default value is \"Auto-detect\" which
means that MH-E will automatically choose one of \"swish++\",
\"swish-e\", \"mairix\", \"namazu\", \"pick\" and \"grep\" in
that order. If, for example, you have both \"swish++\" and
\"mairix\" installed and you want to use \"mairix\", then you can
set this option to \"mairix\".

The documentation for the following commands describe how to set
up the various indexing programs to use with MH-E.

    - `mh-swish++-execute-search'
    - `mh-swish-execute-search'
    - `mh-mairix-execute-search'
    - `mh-namazu-execute-search'
    - `mh-pick-execute-search'
    - `mh-grep-execute-search'

In a program, if FOLDER is \"+\" or nil, then mail in all folders
are searched. Optional argument WINDOW-CONFIG stores the window
configuration that will be restored after the user quits the
folder containing the index search results."
  (interactive
   (list (progn
           (mh-find-path)
           ;; Yes, we do want to call mh-search-choose every time in case the
           ;; user has switched the searcher manually.
           (unless (mh-search-choose (and current-prefix-arg
                                          mh-index-previous-search
                                          (cadr mh-index-previous-search)))
             (error "No search program found"))
           (or (and current-prefix-arg mh-index-sequence-search-flag)
               (and current-prefix-arg (car mh-index-previous-search))
               (mh-prompt-for-folder "Search" "+" nil "all" t)))
         (or (and current-prefix-arg (caddr mh-index-previous-search))
             mh-search-regexp-builder
             (read-string (format "%s regexp: "
                                  (upcase-initials (symbol-name mh-searcher)))))
         current-prefix-arg
         (if (and (not (and current-prefix-arg
                            (caddr mh-index-previous-search)))
                  mh-search-regexp-builder)
             (current-window-configuration)
           nil)))
  (cl-block mh-search
    ;; Redoing a sequence search?
    (when (and redo-search-flag mh-index-data mh-index-sequence-search-flag
               (not mh-flists-called-flag))
      (let ((mh-flists-called-flag t))
        (apply #'mh-index-sequenced-messages mh-index-previous-search))
      (cl-return-from mh-search))
    ;; We have fancy query parsing.
    (when (symbolp search-regexp)
      (mh-search-folder folder window-config)
      (cl-return-from mh-search))
    ;; Begin search proper.
    (mh-checksum-choose)
    (let ((result-count 0)
          (old-window-config (or window-config mh-previous-window-config))
          (previous-search mh-index-previous-search)
          (index-folder (format "%s/%s" mh-index-folder
                                (mh-index-generate-pretty-name search-regexp))))
      ;; Create a new folder for the search results or recreate the old one...
      (if (and redo-search-flag mh-index-previous-search)
          (let ((buffer-name (buffer-name (current-buffer))))
            (mh-process-or-undo-commands buffer-name)
            (save-excursion (mh-exec-cmd-quiet nil "rmf" buffer-name))
            (mh-exec-cmd-quiet nil "folder" "-create" "-fast" buffer-name)
            (setq index-folder buffer-name))
        (setq index-folder (mh-index-new-folder index-folder search-regexp)))

      (let ((folder-path (format "%s%s" mh-user-path (substring folder 1)))
            (folder-results-map (make-hash-table :test #'equal))
            (origin-map (make-hash-table :test #'equal)))
        ;; Run search program...
        (message "Executing %s... " mh-searcher)
        (funcall mh-search-function folder-path search-regexp)

        ;; Parse searcher output.
        (message "Processing %s output... " mh-searcher)
        (goto-char (point-min))
        (cl-loop for next-result = (funcall mh-search-next-result-function)
                 while next-result
                 do (unless (eq next-result 'error)
                      (unless (gethash (car next-result) folder-results-map)
                        (setf (gethash (car next-result) folder-results-map)
                              (make-hash-table :test #'equal)))
                      (setf (gethash (cadr next-result)
                                     (gethash (car next-result) folder-results-map))
                            t)))

        ;; Copy the search results over.
        (maphash #'(lambda (folder msgs)
                     (let ((cur (car (mh-translate-range folder "cur")))
                           (msgs (sort (cl-loop
                                        for msg being the hash-keys of msgs
                                        collect msg)
                                       #'<)))
                       (mh-exec-cmd "refile" msgs "-src" folder
                                    "-link" index-folder)
                       ;; Restore cur to old value, that refile changed
                       (when cur
                         (mh-exec-cmd-quiet nil "mark" folder "-add" "-zero"
                                            "-sequence"
                                            "cur" (format "%s" cur)))
                       (cl-loop for msg in msgs
                                do (cl-incf result-count)
                                (setf (gethash result-count origin-map)
                                      (cons folder msg)))))
                 folder-results-map)

        ;; Vist the results folder.
        (mh-visit-folder index-folder () (list folder-results-map origin-map))

        (goto-char (point-min))
        (forward-line)
        (mh-update-sequences)
        (mh-recenter nil)

        ;; Update the speedbar, if needed.
        (when (mh-speed-flists-active-p)
          (mh-speed-flists t mh-current-folder))

        ;; Maintain history.
        (when (or (and redo-search-flag previous-search) window-config)
          (setq mh-previous-window-config old-window-config))
        (setq mh-index-previous-search (list folder mh-searcher search-regexp))

        ;; Write out data to disk.
        (unless mh-flists-called-flag (mh-index-write-data))

        (message "%s found %s matches in %s folders"
                 (upcase-initials (symbol-name mh-searcher))
                 (cl-loop for msg-hash being the hash-values of mh-index-data
                          sum (hash-table-count msg-hash))
                 (cl-loop for msg-hash being the hash-values of mh-index-data
                          count (> (hash-table-count msg-hash) 0)))))))

;; Shush compiler.
(mh-do-in-xemacs
  (defvar pick-folder))                    ;FIXME: Why?

(defun mh-search-folder (folder window-config)
  "Search FOLDER for messages matching a pattern.

In a program, argument WINDOW-CONFIG is the current window
configuration and is used when the search folder is dismissed."
  (interactive (list (mh-prompt-for-folder "Search" mh-current-folder nil nil t)
                     (current-window-configuration)))
  ;; FIXME: `pick-folder' is unused!
  (let ((pick-folder (if (equal folder "+") mh-current-folder folder)))
    (switch-to-buffer-other-window "search-pattern")
    (if (or (zerop (buffer-size))
            (not (y-or-n-p "Reuse pattern? ")))
        (mh-make-pick-template)
      (message ""))
    (mh-make-local-vars 'mh-current-folder folder
                        'mh-previous-window-config window-config)
    (message "%s" (substitute-command-keys
                   (concat "Type \\[mh-index-do-search] to search messages, "
                           "\\[mh-pick-do-search] to use pick, "
                           "\\[mh-help] for help")))))

(defun mh-make-pick-template ()
  "Initialize the current buffer with a template for a pick pattern."
  (let ((inhibit-read-only t)) (erase-buffer))
  (insert "From: \n"
          "To: \n"
          "Cc: \n"
          "Date: \n"
          "Subject: \n"
          "---------\n")
  (mh-search-mode)
  (goto-char (point-min))
  (dotimes (i 5)
    (add-text-properties (point) (1+ (point)) '(front-sticky t))
    (add-text-properties (- (mh-line-end-position) 2)
                         (1- (mh-line-end-position))
                         '(rear-nonsticky t))
    (add-text-properties (point) (1- (mh-line-end-position)) '(read-only t))
    (forward-line))
  (add-text-properties (point) (1+ (point)) '(front-sticky t))
  (add-text-properties (point) (1- (mh-line-end-position)) '(read-only t))
  (goto-char (point-max)))

;; Sequence Searches

;;;###mh-autoload
(defun mh-index-new-messages (folders)
  "Display unseen messages.

If you use a program such as \"procmail\" to use \"rcvstore\" to file
your incoming mail automatically, you can display new, unseen,
messages using this command. All messages in the \"unseen\"
sequence from the folders in `mh-new-messages-folders' are
listed.

With a prefix argument, enter a space-separated list of FOLDERS,
or nothing to search all folders."
  (interactive
   (list (if current-prefix-arg
             (split-string (read-string "Search folder(s) (default all): "))
           mh-new-messages-folders)))
  (mh-index-sequenced-messages folders mh-unseen-seq))

;;;###mh-autoload
(defun mh-index-ticked-messages (folders)
  "Display ticked messages.

All messages in `mh-tick-seq' from the folders in
`mh-ticked-messages-folders' are listed.

With a prefix argument, enter a space-separated list of FOLDERS,
or nothing to search all folders."
  (interactive
   (list (if current-prefix-arg
             (split-string (read-string "Search folder(s) (default all): "))
           mh-ticked-messages-folders)))
  (mh-index-sequenced-messages folders mh-tick-seq))

(defvar mh-mairix-folder)
(defvar mh-flists-search-folders)

;;;###mh-autoload
(defun mh-index-sequenced-messages (folders sequence)
  "Display messages in any sequence.

All messages from the FOLDERS in `mh-new-messages-folders' in the
SEQUENCE you provide are listed. With a prefix argument, enter a
space-separated list of folders at the prompt, or nothing to
search all folders."
  (interactive
   (list (if current-prefix-arg
             (split-string (read-string "Search folder(s) (default all): "))
           mh-new-messages-folders)
         (mh-read-seq-default "Search" nil)))
  (unless sequence (setq sequence mh-unseen-seq))
  (let* ((mh-flists-search-folders folders)
         (mh-flists-sequence sequence)
         (mh-flists-called-flag t)
         (mh-searcher 'flists)
         (mh-search-function 'mh-flists-execute)
         (mh-search-next-result-function 'mh-mairix-next-result)
         (mh-mairix-folder mh-user-path)
         (mh-search-regexp-builder nil)
         (new-folder (format "%s/%s/%s" mh-index-folder
                             mh-flists-results-folder sequence))
         (window-config (if (equal new-folder mh-current-folder)
                            mh-previous-window-config
                          (current-window-configuration)))
         (redo-flag nil)
         message)
    (cond ((buffer-live-p (get-buffer new-folder))
           ;; The destination folder is being visited. Trick `mh-search'
           ;; into thinking that the folder resulted from a previous search.
           (set-buffer new-folder)
           (setq mh-index-previous-search (list folders mh-searcher sequence))
           (setq redo-flag t))
          ((mh-folder-exists-p new-folder)
           ;; Folder exists but we don't have it open. That means they are
           ;; stale results from an old flists search. Clear it out.
           (mh-exec-cmd-quiet nil "rmf" new-folder)))
    (setq message (mh-search "+" mh-flists-results-folder
                             redo-flag window-config)
          mh-index-sequence-search-flag t
          mh-index-previous-search (list folders mh-searcher sequence))
    (mh-index-write-data)
    (when (stringp message) (message "%s" message))))

(defvar mh-flists-search-folders)

(defun mh-flists-execute (&rest ignored)
  "Execute flists.
Search for messages belonging to `mh-flists-sequence' in the
folders specified by `mh-flists-search-folders'. If
`mh-recursive-folders-flag' is t, then the folders are searched
recursively. All arguments are IGNORED."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (unless (executable-find "sh")
    (error "Didn't find sh"))
  (with-temp-buffer
    (let ((seq (symbol-name mh-flists-sequence)))
      (insert "for folder in `" (expand-file-name "flists" mh-progs) " "
              (cond ((eq mh-flists-search-folders t)
                     (mh-quote-for-shell mh-inbox))
                    ((eq mh-flists-search-folders nil) "")
                    ((listp mh-flists-search-folders)
                     (cl-loop for folder in mh-flists-search-folders
                              concat
                              (concat " " (mh-quote-for-shell folder)))))
              (if mh-recursive-folders-flag " -recurse" "")
              " -sequence " seq " -noshowzero -fast` ; do\n"
              (expand-file-name "mhpath" mh-progs) " \"+$folder\" " seq "\n"
              "done\n"))
    (call-process-region
     (point-min) (point-max) "sh" nil (get-buffer mh-temp-index-buffer))))

;; Navigation

;;;###mh-autoload
(defun mh-index-next-folder (&optional backward-flag)
  "Jump to the next folder marker.

With non-nil optional argument BACKWARD-FLAG, jump to the previous
group of results."
  (interactive "P")
  (if (null mh-index-data)
      (message "Only applicable in an MH-E index search buffer")
    (let ((point (point)))
      (forward-line (if backward-flag 0 1))
      (cond ((if backward-flag
                 (re-search-backward "^\\+" (point-min) t)
               (re-search-forward "^\\+" (point-max) t))
             (beginning-of-line))
            ((and (if backward-flag
                      (goto-char (point-max))
                    (goto-char (point-min)))
                  nil))
            ((if backward-flag
                 (re-search-backward "^\\+" (point-min) t)
               (re-search-forward "^\\+" (point-max) t))
             (beginning-of-line))
            (t (goto-char point))))))

;;;###mh-autoload
(defun mh-index-previous-folder ()
  "Jump to the previous folder marker."
  (interactive)
  (mh-index-next-folder t))

;;;###mh-autoload
(defun mh-index-visit-folder ()
  "Visit original folder from where the message at point was found."
  (interactive)
  (unless mh-index-data
    (error "Not in an index folder"))
  (let (folder msg)
    (save-excursion
      (cond ((and (bolp) (eolp))
             (ignore-errors (forward-line -1))
             (setq msg (mh-get-msg-num t)))
            ((equal (char-after (mh-line-beginning-position)) ?+)
             (setq folder (buffer-substring-no-properties
                           (mh-line-beginning-position)
                           (mh-line-end-position))))
            (t (setq msg (mh-get-msg-num t)))))
    (when (not folder)
      (setq folder (car (gethash (gethash msg mh-index-msg-checksum-map)
                                 mh-index-checksum-origin-map))))
    (when (or (not (get-buffer folder))
              (y-or-n-p (format "Reuse buffer displaying %s? " folder)))
      (mh-visit-folder
       folder (cl-loop
               for x being the hash-keys of (gethash folder mh-index-data)
               when (mh-msg-exists-p x folder) collect x)))))



;;; Search Menu

(easy-menu-define
  mh-pick-menu mh-search-mode-map "Menu for MH-E Search"
  '("Search"
    ["Perform Search"       mh-index-do-search t]
    ["Search with pick"     mh-pick-do-search t]))



;;; MH-Search Keys

;; If this changes, modify mh-search-mode-help-messages accordingly, below.
(gnus-define-keys  mh-search-mode-map
  "\C-c?"               mh-help
  "\C-c\C-c"            mh-index-do-search
  "\C-c\C-p"            mh-pick-do-search
  "\C-c\C-f\C-b"        mh-to-field
  "\C-c\C-f\C-c"        mh-to-field
  "\C-c\C-f\C-m"        mh-to-field
  "\C-c\C-f\C-s"        mh-to-field
  "\C-c\C-f\C-t"        mh-to-field
  "\C-c\C-fb"           mh-to-field
  "\C-c\C-fc"           mh-to-field
  "\C-c\C-fm"           mh-to-field
  "\C-c\C-fs"           mh-to-field
  "\C-c\C-ft"           mh-to-field)



;;; MH-Search Help Messages

;; Group messages logically, more or less.
(defvar mh-search-mode-help-messages
  '((nil
     "Perform search:   \\[mh-index-do-search]\n"
     "Search with pick: \\[mh-pick-do-search]\n\n"
     "Move to a field by typing C-c C-f C-<field>\n"
     "where <field> is the first letter of the desired field\n"
     "(except for From: which uses \"m\")."))
  "Key binding cheat sheet.

This is an associative array which is used to show the most common
commands. The key is a prefix char. The value is one or more strings
which are concatenated together and displayed in the minibuffer if ?
is pressed after the prefix character. The special key nil is used to
display the non-prefixed commands.

The substitutions described in `substitute-command-keys' are performed
as well.")



;;; MH-Search Mode

(put 'mh-search-mode 'mode-class 'special)

(define-derived-mode mh-search-mode fundamental-mode "MH-Search"
  "Mode for creating search templates in MH-E.\\<mh-search-mode-map>

Edit this template by entering your search criteria in an
appropriate header field that is already there, or create a new
field yourself. If the string you're looking for could be
anywhere in a message, then place the string underneath the row
of dashes.

To perform the search, type \\[mh-index-do-search].

Sometimes you're searching for text that is either not indexed,
or hasn't been indexed yet. In this case you can override the
default method with the pick method by running the command
\\[mh-pick-do-search].

The hook `mh-search-mode-hook' is called upon entry to this mode.

\\{mh-search-mode-map}"

  (easy-menu-add mh-pick-menu)
  (mh-set-help mh-search-mode-help-messages))



;;; MH-Search Commands

(defun mh-index-do-search (&optional searcher)
  "Find messages using `mh-search-program'.
If optional argument SEARCHER is present, use it instead of
`mh-search-program'."
  (interactive)
  (unless (mh-search-choose searcher) (error "No search program found"))
  (let* ((regexp-list (mh-pick-parse-search-buffer))
         (pattern (funcall mh-search-regexp-builder regexp-list)))
    (if pattern
        (mh-search mh-current-folder pattern nil mh-previous-window-config)
      (error "No search terms"))))

(defun mh-pick-do-search ()
  "Find messages using \"pick\".

Uses the pick method described in `mh-pick-execute-search'."
  (interactive)
  (mh-index-do-search 'pick))

(defun mh-pick-parse-search-buffer ()
  "Parse the search buffer contents.
The function returns an alist. The car of each element is either
the header name to search in or nil to search the whole message.
The cdr of the element is the pattern to search."
  (save-excursion
    (let ((pattern-list ())
          (in-body-flag nil)
          start begin)
      (goto-char (point-min))
      (while (not (eobp))
        (if (search-forward "--------" (mh-line-end-position) t)
            (setq in-body-flag t)
          (beginning-of-line)
          (setq begin (point))
          (setq start (if in-body-flag
                          (point)
                        (search-forward ":" (mh-line-end-position) t)
                        (point)))
          (push (cons (and (not in-body-flag)
                           (intern (downcase
                                    (buffer-substring-no-properties
                                     begin (1- start)))))
                      (mh-index-parse-search-regexp
                       (buffer-substring-no-properties
                        start (mh-line-end-position))))
                pattern-list))
        (forward-line))
      pattern-list)))

(defun mh-index-parse-search-regexp (input-string)
  "Construct parse tree for INPUT-STRING.
All occurrences of &, |, ! and ~ in INPUT-STRING are replaced by
AND, OR and NOT as appropriate. Then the resulting string is
parsed."
  (let (input)
    (with-temp-buffer
      (insert input-string)
      ;; replace tabs
      (mh-replace-string "\t" " ")
      ;; synonyms of AND
      (mh-replace-string " AND " " and ")
      (mh-replace-string "&" " and ")
      (mh-replace-string " -and " " and ")
      ;; synonyms of OR
      (mh-replace-string " OR " " or ")
      (mh-replace-string "|" " or ")
      (mh-replace-string " -or " " or ")
      ;; synonyms of NOT
      (mh-replace-string " NOT " " not ")
      (mh-replace-string "!" " not ")
      (mh-replace-string "~" " not ")
      (mh-replace-string " -not " " not ")
      ;; synonyms of left brace
      (mh-replace-string "(" " ( ")
      (mh-replace-string " -lbrace " " ( ")
      ;; synonyms of right brace
      (mh-replace-string ")" " ) ")
      (mh-replace-string " -rbrace " " ) ")
      ;; get the normalized input
      (setq input (format "( %s )" (buffer-substring (point-min) (point-max)))))

    (let ((tokens (mh-index-add-implicit-ops (split-string input)))
          (op-stack ())
          (operand-stack ())
          oper1)
      (dolist (token tokens)
        (cond ((equal token "(") (push 'paren op-stack))
              ((equal token "not") (push 'not op-stack))
              ((equal token "or") (push 'or op-stack))
              ((equal token "and") (push 'and op-stack))
              ((equal token ")")
               (cl-multiple-value-setq (op-stack operand-stack)
                 (cl-values-list (mh-index-evaluate op-stack operand-stack)))
               (when (eq (car op-stack) 'not)
                 (setq op-stack (cdr op-stack))
                 (push `(not ,(pop operand-stack)) operand-stack))
               (when (eq (car op-stack) 'and)
                 (setq op-stack (cdr op-stack))
                 (setq oper1 (pop operand-stack))
                 (push `(and ,(pop operand-stack) ,oper1) operand-stack)))
              ((eq (car op-stack) 'not)
               (setq op-stack (cdr op-stack))
               (push `(not ,token) operand-stack)
               (when (eq (car op-stack) 'and)
                 (setq op-stack (cdr op-stack))
                 (setq oper1 (pop operand-stack))
                 (push `(and ,(pop operand-stack) ,oper1) operand-stack)))
              ((eq (car op-stack) 'and)
               (setq op-stack (cdr op-stack))
               (push `(and ,(pop operand-stack) ,token) operand-stack))
              (t (push token operand-stack))))
      (prog1 (pop operand-stack)
        (when (or op-stack operand-stack)
          (error "Invalid regexp: %s" input))))))

(defun mh-index-add-implicit-ops (tokens)
  "Add implicit operators in the list TOKENS."
  (let ((result ())
        (literal-seen nil)
        current)
    (while tokens
      (setq current (pop tokens))
      (cond ((or (equal current ")") (equal current "and") (equal current "or"))
             (setq literal-seen nil)
             (push current result))
            ((and literal-seen
                  (push "and" result)
                  (setq literal-seen nil)
                  nil))
            (t
             (push current result)
             (unless (or (equal current "(") (equal current "not"))
               (setq literal-seen t)))))
    (nreverse result)))

(defun mh-index-evaluate (op-stack operand-stack)
  "Read expression till starting paren based on OP-STACK and OPERAND-STACK."
  (cl-block mh-index-evaluate
    (let (op oper1)
      (while op-stack
        (setq op (pop op-stack))
        (cond ((eq op 'paren)
               (cl-return-from mh-index-evaluate (list op-stack operand-stack)))
              ((eq op 'not)
               (push `(not ,(pop operand-stack)) operand-stack))
              ((or (eq op 'and) (eq op 'or))
               (setq oper1 (pop operand-stack))
               (push `(,op ,(pop operand-stack) ,oper1) operand-stack))))
      (error "Ran out of tokens"))))



;;; Indexing Functions

;; Support different search programs
(defvar mh-search-choices
  '((swish++
     mh-swish++-binary mh-swish++-execute-search mh-swish++-next-result
     mh-swish++-regexp-builder)
    (swish
     mh-swish-binary mh-swish-execute-search mh-swish-next-result nil)
    (mairix
     mh-mairix-binary mh-mairix-execute-search mh-mairix-next-result
     mh-mairix-regexp-builder)
    (namazu
     mh-namazu-binary mh-namazu-execute-search mh-namazu-next-result nil)
    (pick
     mh-pick-binary mh-pick-execute-search mh-pick-next-result
     mh-pick-regexp-builder)
    (grep
     mh-grep-binary mh-grep-execute-search mh-grep-next-result nil))
  "List of possible searcher choices.")

(defun mh-search-choose (&optional searcher)
  "Choose a searching function.
The side-effects of this function are that the variables
`mh-searcher', `mh-search-function', and
`mh-search-next-result-function' are set according to the first
searcher in `mh-search-choices' present on the system. If
optional argument SEARCHER is present, use it instead of
`mh-search-program'."
  (cl-block nil
    (let ((program-alist (cond (searcher
                                (list (assoc searcher mh-search-choices)))
                               (mh-search-program
                                (list
                                 (assoc mh-search-program mh-search-choices)))
                               (t mh-search-choices))))
      (while program-alist
        (let* ((current (pop program-alist))
               (executable (symbol-value (cadr current))))
          (when executable
            (setq mh-searcher (car current))
            (setq mh-search-function (nth 2 current))
            (setq mh-search-next-result-function (nth 3 current))
            (setq mh-search-regexp-builder (nth 4 current))
            (cl-return mh-searcher))))
      nil)))

;;; Swish++

(defvar mh-swish++-binary (or (executable-find "search++")
                              (executable-find "search")))
(defvar mh-swish++-directory ".swish++")
(defvar mh-swish-folder nil)

(defun mh-swish++-execute-search (folder-path search-regexp)
  "Execute swish++.

In the examples below, replace \"/home/user/Mail\" with the path to
your MH directory.

First create the directory \"/home/user/Mail/.swish++\". Then create
the file \"/home/user/Mail/.swish++/swish++.conf\" with the following
contents:

     IncludeMeta         Bcc Cc Comments Content-Description From Keywords
     IncludeMeta         Newsgroups Resent-To Subject To
     IncludeMeta         Message-Id References In-Reply-To
     IncludeFile         Mail    *
     IndexFile           /home/user/Mail/.swish++/swish++.index

Use the following command line to generate the swish index. Run
this daily from cron:

     find /home/user/Mail -path /home/user/Mail/mhe-index -prune \\
                          -o -path /home/user/Mail/.swish++ -prune \\
                          -o -name \"[0-9]*\" -print \\
         | index -c /home/user/Mail/.swish++/swish++.conf -

This command does not index the folders that hold the results of your
searches in \"+mhe-index\" since they tend to be ephemeral and the
original messages are indexed anyway.

On some systems (Debian GNU/Linux, for example), use \"index++\"
instead of \"index\".

In a program, FOLDER-PATH is the directory in which SEARCH-REGEXP is
used to search."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (unless mh-swish++-binary
    (error "Set `mh-swish++-binary' appropriately"))
  (call-process mh-swish++-binary nil '(t nil) nil
                "-m" "10000"
                (format "-i%s%s/swish++.index"
                        mh-user-path mh-swish++-directory)
                search-regexp)
  (goto-char (point-min))
  (setq mh-swish-folder
        (let ((last-char (substring folder-path (1- (length folder-path)))))
          (if (equal last-char "/")
              folder-path
            (format "%s/" folder-path)))))

(defalias 'mh-swish++-next-result 'mh-swish-next-result)

(defun mh-swish++-regexp-builder (regexp-list)
  "Generate query for swish++.
REGEXP-LIST is an alist of fields and values."
  (let ((regexp ""))
    (dolist (elem regexp-list)
      (when (cdr elem)
        (setq regexp (concat regexp " and "
                             (if (car elem) "(" "")
                             (if (car elem) (symbol-name (car elem)) "")
                             (if (car elem) " = " "")
                             (mh-swish++-print-regexp (cdr elem))
                             (if (car elem) ")" "")))))
    (substring regexp 4)))

(defun mh-swish++-print-regexp (expr)
  "Return infix expression corresponding to EXPR."
  (cond ((atom expr) (format "%s" expr))
        ((eq (car expr) 'not)
         (format "(not %s)" (mh-swish++-print-regexp (cadr expr))))
        (t (format "(%s %s %s)" (mh-swish++-print-regexp (cadr expr))
                   (symbol-name (car expr))
                   (mh-swish++-print-regexp (caddr expr))))))

;;; Swish

(defvar mh-swish-binary (executable-find "swish-e"))
(defvar mh-swish-directory ".swish")

(defun mh-swish-execute-search (folder-path search-regexp)
  "Execute swish-e.

In the examples below, replace \"/home/user/Mail\" with the path
to your MH directory.

First create the directory \"/home/user/Mail/.swish\". Then
create the file \"/home/user/Mail/.swish/config\" with the
following contents:

     DefaultContents TXT*
     IndexDir /home/user/Mail
     IndexFile /home/user/Mail/.swish/index
     IndexName \"Mail Index\"
     IndexDescription \"Mail Index\"
     IndexPointer \"http://nowhere\"
     IndexAdmin \"nobody\"
     #MetaNames automatic
     IndexReport 3
     FollowSymLinks no
     UseStemming no
     IgnoreTotalWordCountWhenRanking yes
     WordCharacters abcdefghijklmnopqrstuvwxyz0123456789-
     BeginCharacters abcdefghijklmnopqrstuvwxyz
     EndCharacters abcdefghijklmnopqrstuvwxyz0123456789
     IgnoreLimit 50 1000
     IndexComments 0
     FileRules filename contains \\D
     FileRules pathname contains /home/user/Mail/.swish
     FileRules pathname contains /home/user/Mail/mhe-index

This configuration does not index the folders that hold the
results of your searches in \"+mhe-index\" since they tend to be
ephemeral and the original messages are indexed anyway.

If there are any directories you would like to ignore, append
lines like the following to \"config\":

     FileRules pathname contains /home/user/Mail/scripts

Use the following command line to generate the swish index. Run
this daily from cron:

         swish-e -c /home/user/Mail/.swish/config

In a program, FOLDER-PATH is the directory in which SEARCH-REGEXP
is used to search."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (unless mh-swish-binary
    (error "Set `mh-swish-binary' appropriately"))
  (call-process mh-swish-binary nil '(t nil) nil
                "-w" search-regexp
                "-f" (format "%s%s/index" mh-user-path mh-swish-directory))
  (goto-char (point-min))
  (setq mh-swish-folder
        (let ((last-char (substring folder-path (1- (length folder-path)))))
          (if (equal last-char "/")
              folder-path
            (format "%s/" folder-path)))))

(defun mh-swish-next-result ()
  "Get the next result from swish output."
  (prog1
      (cl-block nil
        (when (or (eobp) (equal (char-after (point)) ?.))
          (cl-return nil))
        (when (equal (char-after (point)) ?#)
          (cl-return 'error))
        (let* ((start (search-forward " " (mh-line-end-position) t))
               (end (search-forward " " (mh-line-end-position) t)))
          (unless (and start end)
            (cl-return 'error))
          (setq end (1- end))
          (unless (file-exists-p (buffer-substring-no-properties start end))
            (cl-return 'error))
          (unless (search-backward "/" start t)
            (cl-return 'error))
          (list (let* ((s (buffer-substring-no-properties start (1+ (point)))))
                  (unless (string-match mh-swish-folder s)
                    (cl-return 'error))
                  (if (and (string-match mh-user-path s)
                           (< (match-end 0) (1- (length s))))
                      (format "+%s"
                              (substring s (match-end 0) (1- (length s))))
                    (cl-return 'error)))
                (let* ((s (buffer-substring-no-properties (1+ (point)) end))
                       (n (ignore-errors (string-to-number s))))
                  (or n (cl-return 'error)))
                nil)))
    (forward-line)))

;;; Mairix

(defvar mh-mairix-binary (executable-find "mairix"))
(defvar mh-mairix-directory ".mairix")
(defvar mh-mairix-folder nil)

(defun mh-mairix-execute-search (folder-path search-regexp-list)
  "Execute mairix.

In the examples below, replace \"/home/user/Mail\" with the path
to your MH directory.

First create the directory \"/home/user/Mail/.mairix\". Then
create the file \"/home/user/Mail/.mairix/config\" with the
following contents:

     base=/home/user/Mail

     # List of folders that should be indexed. 3 dots at the end means there
     # are subfolders within the folder
     mh=archive...:inbox:drafts:news:sent:trash

     vfolder_format=mh
     database=/home/user/Mail/.mairix/database

Use the following command line to generate the mairix index. Run
this daily from cron:

     mairix -f /home/user/Mail/.mairix/config

In a program, FOLDER-PATH is the directory in which
SEARCH-REGEXP-LIST is used to search."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (unless mh-mairix-binary
    (error "Set `mh-mairix-binary' appropriately"))
  (apply #'call-process mh-mairix-binary nil '(t nil) nil
         "-r" "-f" (format "%s%s/config" mh-user-path mh-mairix-directory)
         search-regexp-list)
  (goto-char (point-min))
  (setq mh-mairix-folder
        (let ((last-char (substring folder-path (1- (length folder-path)))))
          (if (equal last-char "/")
              folder-path
            (format "%s/" folder-path)))))

(defun mh-mairix-next-result ()
  "Return next result from mairix output."
  (prog1
      (cl-block nil
        (when (or (eobp) (and (bolp) (eolp)))
          (cl-return nil))
        (unless (eq (char-after) ?/)
          (cl-return 'error))
        (let ((start (point))
              end msg-start)
          (setq end (mh-line-end-position))
          (unless (search-forward mh-mairix-folder end t)
            (cl-return 'error))
          (goto-char (match-beginning 0))
          (unless (equal (point) start)
            (cl-return 'error))
          (goto-char end)
          (unless (search-backward "/" start t)
            (cl-return 'error))
          (setq msg-start (1+ (point)))
          (goto-char start)
          (unless (search-forward mh-user-path end t)
            (cl-return 'error))
          (list (format "+%s" (buffer-substring-no-properties
                               (point) (1- msg-start)))
                (string-to-number
                 (buffer-substring-no-properties msg-start end))
                nil)))
    (forward-line)))

(defun mh-mairix-regexp-builder (regexp-list)
  "Generate query for mairix.
REGEXP-LIST is an alist of fields and values."
  (let ((result ()))
    (dolist (pair regexp-list)
      (when (cdr pair)
        (push
         (concat
          (cond ((eq (car pair) 'to) "t:")
                ((eq (car pair) 'from) "f:")
                ((eq (car pair) 'cc) "c:")
                ((eq (car pair) 'to-or-cc) "tc:")
                ((eq (car pair) 'address) "a:")
                ((eq (car pair) 'subject) "s:")
                ((eq (car pair) 'subject-or-body) "bs:")
                ((eq (car pair) 'date) "d:")
                ((eq (car pair) 'message-id) "m:")
                ((eq (car pair) 'message-body) "b:")
                ((eq (car pair) 'message-size) "z:")
                ((eq (car pair) 'message-attachment-name) "n:")
                ((eq (car pair) 'message-flags) "F:")
                (t ""))
          (let ((sop (cdr (mh-mairix-convert-to-sop* (cdr pair))))
                (final ""))
            (dolist (conjunct sop)
              (let ((expr-list (cdr conjunct))
                    (expr-string ""))
                (dolist (e expr-list)
                  (setq expr-string (concat expr-string ","
                                            (if (atom e) "" "~")
                                            (if (atom e) e (cadr e)))))
                (setq final (concat final "/" (substring expr-string 1)))))
            (substring final 1)))
         result)))
    result))

(defun mh-mairix-convert-to-sop* (expr)
  "Convert EXPR to sum of product form."
  (cond ((atom expr) `(or (and ,expr)))
        ((eq (car expr) 'or)
         (cons 'or
               (cl-loop for e in (mapcar #'mh-mairix-convert-to-sop* (cdr expr))
                        append (cdr e))))
        ((eq (car expr) 'and)
         (let ((conjuncts (mapcar #'mh-mairix-convert-to-sop* (cdr expr)))
               result next-factor)
           (setq result (pop conjuncts))
           (while conjuncts
             (setq next-factor (pop conjuncts))
             (setq result (let ((res ()))
                            (dolist (t1 (cdr result))
                              (dolist (t2 (cdr next-factor))
                                (push `(and ,@(cdr t1) ,@(cdr t2)) res)))
                            (cons 'or res))))
           result))
        ((atom (cadr expr)) `(or (and ,expr)))
        ((eq (caadr expr) 'not) (mh-mairix-convert-to-sop* (cadadr expr)))
        ((eq (caadr expr) 'and) (mh-mairix-convert-to-sop*
                                 `(or ,@(mapcar #'(lambda (x) `(not ,x))
                                                (cdadr expr)))))
        ((eq (caadr expr) 'or) (mh-mairix-convert-to-sop*
                                `(and ,@(mapcar #'(lambda (x) `(not ,x))
                                                (cdadr expr)))))
        (t (error "Unreachable: %s" expr))))

;;; Namazu

(defvar mh-namazu-binary (executable-find "namazu"))
(defvar mh-namazu-directory ".namazu")
(defvar mh-namazu-folder nil)

(defun mh-namazu-execute-search (folder-path search-regexp)
  "Execute namazu.

In the examples below, replace \"/home/user/Mail\" with the path to
your MH directory.

First create the directory \"/home/user/Mail/.namazu\". Then create
the file \"/home/user/Mail/.namazu/mknmzrc\" with the following
contents:

     package conf;  # Don't remove this line!
     $ADDRESS = \\='user@localhost\\=';
     $ALLOW_FILE = \"[0-9]*\";
     $EXCLUDE_PATH = \"^/home/user/Mail/(mhe-index|spam)\";

This configuration does not index the folders that hold the results of
your searches in \"+mhe-index\" since they tend to be ephemeral and
the original messages are indexed anyway.

Use the following command line to generate the namazu index. Run this
daily from cron:

     mknmz -f /home/user/Mail/.namazu/mknmzrc -O /home/user/Mail/.namazu \\
           -q /home/user/Mail

In a program, FOLDER-PATH is the directory in which SEARCH-REGEXP
is used to search."
  (let ((namazu-index-directory
         (format "%s%s" mh-user-path mh-namazu-directory)))
    (unless (file-exists-p namazu-index-directory)
      (error "Namazu directory %s not present" namazu-index-directory))
    (unless (executable-find mh-namazu-binary)
      (error "Set `mh-namazu-binary' appropriately"))
    (set-buffer (get-buffer-create mh-temp-index-buffer))
    (erase-buffer)
    (call-process mh-namazu-binary nil '(t nil) nil
                  "-alR" search-regexp namazu-index-directory)
    (goto-char (point-min))
    (setq mh-namazu-folder
          (let ((last (substring folder-path (1- (length folder-path)))))
            (if (equal last "/")
                folder-path
              (format "%s/" folder-path))))))

(defun mh-namazu-next-result ()
  "Get the next result from namazu output."
  (prog1
      (cl-block nil
        (when (eobp) (cl-return nil))
        (let ((file-name (buffer-substring-no-properties
                          (point) (mh-line-end-position))))
          (unless (equal (string-match mh-namazu-folder file-name) 0)
            (cl-return 'error))
          (unless (file-exists-p file-name)
            (cl-return 'error))
          (string-match mh-user-path file-name)
          (let* ((folder/msg (substring file-name (match-end 0)))
                 (mark (mh-search-from-end ?/ folder/msg)))
            (unless mark (cl-return 'error))
            (list (format "+%s" (substring folder/msg 0 mark))
                  (let ((n (ignore-errors (string-to-number
                                           (substring folder/msg (1+ mark))))))
                    (or n (cl-return 'error)))
                  nil))))
    (forward-line)))

;;; Pick

(defvar mh-index-pick-folder)
(defvar mh-pick-binary "pick")
(defconst mh-pick-single-dash  '(cc date from subject to)
  "Search components that are supported by single-dash option in pick.")

(defun mh-pick-execute-search (folder-path search-regexp)
  "Execute pick.

Read \"pick(1)\" or the section Finding Messages with pick in the
MH book to find out more about how to enter the criteria (see URL
`http://www.ics.uci.edu/~mh/book/mh/finpic.htm').

In a program, FOLDER-PATH is the directory in which SEARCH-REGEXP
is used to search."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (let ((folders
         (mh-folder-list (substring folder-path (length mh-user-path)))))
    (cl-loop for folder in folders do
             (setq folder (concat "+" folder))
             (insert folder "\n")
             (apply #'call-process (expand-file-name "pick" mh-progs)
                    nil '(t nil) nil folder "-list" search-regexp)))
  (goto-char (point-min)))

(defun mh-pick-next-result ()
  "Return the next pick search result."
  (prog1
      (cl-block nil
        (when (eobp) (cl-return nil))
        (when (search-forward-regexp "^\\+" (mh-line-end-position) t)
          (setq mh-index-pick-folder
                (buffer-substring-no-properties (mh-line-beginning-position)
                                                (mh-line-end-position)))
          (cl-return 'error))
        (unless (search-forward-regexp "^[1-9][0-9]*$" (mh-line-end-position) t)
          (cl-return 'error))
        (list mh-index-pick-folder
              (string-to-number
               (buffer-substring-no-properties (mh-line-beginning-position)
                                               (mh-line-end-position)))
              nil))
    (forward-line)))

;; All implementations of pick have special options -cc, -date, -from and
;; -subject that allow searching for corresponding components. Any other
;; component is searched using option --COMPNAME, for example: `pick
;; --x-mailer mh-e'. Mailutils "pick" supports this option using a certain
;; kludge, but it prefers the following syntax for this purpose:
;; "--component=COMPNAME --pattern=PATTERN".
;;                                           -- Sergey Poznyakoff, Aug 2003
(defun mh-pick-regexp-builder (pattern-list)
  "Generate pick search expression from PATTERN-LIST."
  (let ((result ()))
    (dolist (pattern pattern-list)
      (when (cdr pattern)
        (setq result `(,@result "-and" "-lbrace"
                       ,@(mh-pick-construct-regexp
                          (if (and (mh-variant-p 'gnu-mh) (car pattern))
                              (format "--pattern=%s" (cdr pattern))
                            (cdr pattern))
                          (if (car pattern)
                              (cond
                               ((mh-variant-p 'gnu-mh)
                                (format "--component=%s" (car pattern)))
                               ((member (car pattern) mh-pick-single-dash)
                                (format "-%s" (car pattern)))
                               (t
                                (format "--%s" (car pattern))))
                            "-search"))
                       "-rbrace"))))
    (cdr result)))

(defun mh-pick-construct-regexp (expr component)
  "Construct pick compatible expression corresponding to EXPR.
COMPONENT is the component to search."
  (cond ((atom expr) (list component expr))
        ((eq (car expr) 'and)
         `("-lbrace" ,@(mh-pick-construct-regexp (cadr expr) component) "-and"
           ,@(mh-pick-construct-regexp (caddr expr) component) "-rbrace"))
        ((eq (car expr) 'or)
         `("-lbrace" ,@(mh-pick-construct-regexp (cadr expr) component) "-or"
           ,@(mh-pick-construct-regexp (caddr expr) component) "-rbrace"))
        ((eq (car expr) 'not)
         `("-lbrace" "-not" ,@(mh-pick-construct-regexp (cadr expr) component)
           "-rbrace"))
        (t (error "Unknown operator %s seen" (car expr)))))

;;; Grep

(defvar mh-grep-binary (executable-find "grep"))

(defun mh-grep-execute-search (folder-path search-regexp)
  "Execute grep.

Unlike the other search methods, this method does not use the
MH-Search buffer. Instead, you simply enter a regular expression
in the minibuffer. For help in constructing regular expressions,
see your man page for \"grep\".

In a program, FOLDER-PATH is the directory in which SEARCH-REGEXP
is used to search."
  (set-buffer (get-buffer-create mh-temp-index-buffer))
  (erase-buffer)
  (call-process mh-grep-binary nil '(t nil) nil
                "-i" "-r" search-regexp folder-path)
  (goto-char (point-min)))

(defun mh-grep-next-result ()
  "Read the next result.
Parse it and return the message folder, message index and the
match. If no other matches left then return nil. If the current
record is invalid return `error'."
  (prog1
      (cl-block nil
        (when (eobp)
          (cl-return nil))
        (let ((eol-pos (mh-line-end-position))
              (bol-pos (mh-line-beginning-position))
              folder-start msg-end)
          (goto-char bol-pos)
          (unless (search-forward mh-user-path eol-pos t)
            (cl-return 'error))
          (setq folder-start (point))
          (unless (search-forward ":" eol-pos t)
            (cl-return 'error))
          (let ((match (buffer-substring-no-properties (point) eol-pos)))
            (forward-char -1)
            (setq msg-end (point))
            (unless (search-backward "/" folder-start t)
              (cl-return 'error))
            (list (format "+%s" (buffer-substring-no-properties
                                 folder-start (point)))
                  (let ((n (ignore-errors (string-to-number
                                           (buffer-substring-no-properties
                                            (1+ (point)) msg-end)))))
                    (or n (cl-return 'error)))
                  match))))
    (forward-line)))



;;; Folder Utilities

;;;###mh-autoload
(defun mh-index-group-by-folder ()
  "Partition the messages based on source folder.
Returns an alist with the folder names in the car and the cdr
being the list of messages originally from that folder."
  (save-excursion
    (goto-char (point-min))
    (let ((result-table (make-hash-table :test #'equal)))
      (cl-loop for msg being the hash-keys of mh-index-msg-checksum-map
               do (push msg (gethash (car (gethash
                                           (gethash msg
                                                    mh-index-msg-checksum-map)
                                           mh-index-checksum-origin-map))
                                     result-table)))
      (cl-loop for x being the hash-keys of result-table
               collect (cons x (nreverse (gethash x result-table)))))))

;;;###mh-autoload
(defun mh-index-insert-folder-headers ()
  "Annotate the search results with original folder names."
  (let ((cur-msg (mh-get-msg-num nil))
        (old-buffer-modified-flag (buffer-modified-p))
        (buffer-read-only nil)
        current-folder last-folder)
    (goto-char (point-min))
    (while (not (eobp))
      (setq current-folder (car (gethash (gethash (mh-get-msg-num nil)
                                                  mh-index-msg-checksum-map)
                                         mh-index-checksum-origin-map)))
      (when (and current-folder (not (equal current-folder last-folder)))
        (insert (if last-folder "\n" "") current-folder "\n")
        (setq last-folder current-folder))
      (forward-line))
    (when cur-msg
      (mh-notate-cur)
      (mh-goto-msg cur-msg t))
    (set-buffer-modified-p old-buffer-modified-flag))
  (mh-index-create-imenu-index))

;;;###mh-autoload
(defun mh-index-delete-folder-headers ()
  "Delete the folder headers."
  (let ((cur-msg (mh-get-msg-num nil))
        (old-buffer-modified-flag (buffer-modified-p))
        (buffer-read-only nil))
    (while (and (not cur-msg) (not (eobp)))
      (forward-line)
      (setq cur-msg (mh-get-msg-num nil)))
    (goto-char (point-min))
    (while (not (eobp))
      (if (or (char-equal (char-after) ?+) (char-equal (char-after) 10))
          (delete-region (point) (progn (forward-line) (point)))
        (forward-line)))
    (when cur-msg (mh-goto-msg cur-msg t t))
    (set-buffer-modified-p old-buffer-modified-flag)))

(eval-and-compile (mh-require 'which-func nil t))

;; Shush compiler.
(defvar which-func-mode)                ; < Emacs 22, XEmacs

;;;###mh-autoload
(defun mh-index-create-imenu-index ()
  "Create alist of folder names and positions in index folder buffers."
  (save-excursion
    (if (boundp 'which-func-mode)
        (setq which-func-mode t))
    (let ((alist ()))
      (goto-char (point-min))
      (while (re-search-forward "^\\+" nil t)
        (save-excursion
          (beginning-of-line)
          (push (cons (buffer-substring-no-properties
                       (point) (mh-line-end-position))
                      (point-marker))
                alist)))
      (setq imenu--index-alist (nreverse alist)))))

;;;###mh-autoload
(defun mh-search-p ()
  "Non-nil means that this folder was generated by searching."
  mh-index-data)

(defvar mh-speed-flists-inhibit-flag)

;;;###mh-autoload
(defun mh-index-execute-commands ()
  "Perform the outstanding operations on the actual messages.
The copies in the searched folder are then deleted, refiled,
blacklisted and whitelisted to get the desired result. Before
processing the messages we make sure that the message is
identical to the one that the user has marked in the index
buffer."
  (save-excursion
    (let ((folders ())
          (mh-speed-flists-inhibit-flag t))
      (maphash
       (lambda (folder msgs)
         (push folder folders)
         (if (not (get-buffer folder))
             ;; If source folder not open, just delete the messages...
             (apply #'mh-exec-cmd "rmm" folder (mh-coalesce-msg-list msgs))
           ;; Otherwise delete the messages in the source buffer...
           (with-current-buffer folder
             (let ((old-refile-list mh-refile-list)
                   (old-delete-list mh-delete-list)
                   (old-blacklist mh-blacklist)
                   (old-whitelist mh-whitelist))
               (setq mh-refile-list nil
                     mh-delete-list msgs
                     mh-blacklist nil
                     mh-whitelist nil)
               (unwind-protect (mh-execute-commands)
                 (setq mh-refile-list
                       (mapcar (lambda (x)
                                 (cons (car x)
                                       (cl-loop for y in (cdr x)
                                                unless (memq y msgs)
                                                collect y)))
                               old-refile-list)
                       mh-delete-list
                       (cl-loop for x in old-delete-list
                                unless (memq x msgs) collect x)
                       mh-blacklist
                       (cl-loop for x in old-blacklist
                                unless (memq x msgs) collect x)
                       mh-whitelist
                       (cl-loop for x in old-whitelist
                                unless (memq x msgs) collect x))
                 (mh-set-folder-modified-p (mh-outstanding-commands-p))
                 (when (mh-outstanding-commands-p)
                   (mh-notate-deleted-and-refiled)))))))
       (mh-index-matching-source-msgs (append (cl-loop for x in mh-refile-list
                                                       append (cdr x))
                                              mh-delete-list
                                              mh-blacklist
                                              mh-whitelist)
                                      t))
      folders)))

(defun mh-index-generate-pretty-name (string)
  "Given STRING generate a name which is suitable for use as a folder name.
White space from the beginning and end are removed. All spaces in
the name are replaced with underscores and all / are replaced
with $. If STRING is longer than 20 it is truncated too. STRING
could be a list of strings in which case they are concatenated to
construct the base name."
  (with-temp-buffer
    (if (stringp string)
        (insert string)
      (when (car string) (insert (car string)))
      (dolist (s (cdr string))
        (insert "_" s)))
    (setq string (mh-replace-string "-lbrace" " "))
    (setq string (mh-replace-string "-rbrace" " "))
    (setq string (mh-replace-string "-search" " "))
    (subst-char-in-region (point-min) (point-max) ?\( ?  t)
    (subst-char-in-region (point-min) (point-max) ?\) ?  t)
    (subst-char-in-region (point-min) (point-max) ?- ?  t)
    (goto-char (point-min))
    (while (and (not (eobp)) (memq (char-after) '(?  ?\t ?\n ?\r ?_)))
      (delete-char 1))
    (goto-char (point-max))
    (while (and (not (bobp)) (memq (char-before) '(?  ?\t ?\n ?\r ?_)))
      (delete-char -1))
    (subst-char-in-region (point-min) (point-max) ?  ?_ t)
    (subst-char-in-region (point-min) (point-max) ?\t ?_ t)
    (subst-char-in-region (point-min) (point-max) ?\n ?_ t)
    (subst-char-in-region (point-min) (point-max) ?\r ?_ t)
    (subst-char-in-region (point-min) (point-max) ?/ ?$ t)
    (let ((out (truncate-string-to-width (buffer-string) 20)))
      (cond ((eq mh-searcher 'flists)
             (format "%s/%s" mh-flists-results-folder mh-flists-sequence))
            ((equal out mh-flists-results-folder) (concat out "1"))
            (t out)))))

(defun mh-folder-exists-p (folder)
  "Check if FOLDER exists."
  (and (mh-folder-name-p folder)
       (save-excursion
         (with-temp-buffer
           (mh-exec-cmd-output "folder" nil "-fast" "-nocreate" folder)
           (goto-char (point-min))
           ;; Strip + from folder; use optional + in regexp.
           (looking-at (format "+?%s" (substring folder 1)))))))

(defun mh-msg-exists-p (msg folder)
  "Check if MSG exists in FOLDER."
  (file-exists-p (format "%s%s/%s" mh-user-path (substring folder 1) msg)))

(defun mh-index-new-folder (name search-regexp)
  "Return a folder name based on NAME for search results of SEARCH-REGEXP.

If folder NAME already exists and was generated for the same
SEARCH-REGEXP then it is reused.

Otherwise if the folder NAME was generated from a different
search then check if NAME-2 can be used. Otherwise try NAME-3.
This is repeated till we find a new folder name.

If the folder returned doesn't exist then it is created."
  (unless (mh-folder-name-p name)
    (error "The argument should be a valid MH folder name"))
  (let ((chosen-name
         (cl-loop for i from 1
                  for candidate = (if (equal i 1) name (format "%s-%s" name i))
                  when (or (not (mh-folder-exists-p candidate))
                           (equal (mh-index-folder-search-regexp candidate)
                                  search-regexp))
                  return candidate)))
    ;; Do pending refiles/deletes...
    (when (get-buffer chosen-name)
      (mh-process-or-undo-commands chosen-name))
    ;; Recreate folder...
    (save-excursion (mh-exec-cmd-quiet nil "rmf" chosen-name))
    (mh-exec-cmd-quiet nil "folder" "-create" "-fast" chosen-name)
    (mh-remove-from-sub-folders-cache chosen-name)
    (when (boundp 'mh-speed-folder-map)
      (mh-speed-add-folder chosen-name))
    chosen-name))

(defun mh-index-folder-search-regexp (folder)
  "If FOLDER was created by an index search, return the search regexp.
Return nil if FOLDER doesn't exist or the .mhe_index file is
garbled."
  (ignore-errors
    (with-temp-buffer
      (insert-file-contents
       (format "%s%s/%s" mh-user-path (substring folder 1) mh-index-data-file))
      (goto-char (point-min))
      (forward-list 3)
      (cadr (read (current-buffer))))))



;;; Sequence Support

;;;###mh-autoload
(defun mh-index-create-sequences ()
  "Mirror sequences present in source folders in index folder."
  (let ((seq-hash (make-hash-table :test #'equal))
        (seq-list ()))
    (cl-loop for folder being the hash-keys of mh-index-data
             do (setf (gethash folder seq-hash)
                      (mh-create-sequence-map
                       (mh-read-folder-sequences folder nil))))
    (dolist (msg (mh-translate-range mh-current-folder "all"))
      (let* ((checksum (gethash msg mh-index-msg-checksum-map))
             (pair (gethash checksum mh-index-checksum-origin-map))
             (ofolder (car pair))
             (omsg (cdr pair)))
        (cl-loop for seq in (ignore-errors
                              (gethash omsg (gethash ofolder seq-hash)))
                 do (if (assoc seq seq-list)
                        (push msg (cdr (assoc seq seq-list)))
                      (push (list seq msg) seq-list)))))
    (cl-loop for seq in seq-list
             do (apply #'mh-exec-cmd "mark" mh-current-folder
                       "-sequence" (symbol-name (car seq)) "-add"
                       (mapcar #'(lambda (x) (format "%s" x)) (cdr seq))))))

;;;###mh-autoload
(defun mh-create-sequence-map (seq-list)
  "Return a map from msg number to list of sequences in which it is present.
SEQ-LIST is an assoc list whose keys are sequence names and whose
cdr is the list of messages in that sequence."
  (cl-loop with map = (make-hash-table)
           for seq in seq-list
           when (and (not (memq (car seq) (mh-unpropagated-sequences)))
                     (mh-valid-seq-p (car seq)))
           do (cl-loop for msg in (cdr seq)
                       do (push (car seq) (gethash msg map)))
           finally return map))

;;;###mh-autoload
(defun mh-index-add-to-sequence (seq msgs)
  "Add to SEQ the messages in the list MSGS.
This function updates the source folder sequences. Also makes an
attempt to update the source folder buffer if we have it open."
  ;; Don't need to do anything for cur
  (save-excursion
    (when (and (not (memq seq (mh-unpropagated-sequences)))
               (mh-valid-seq-p seq))
      (let ((folders ())
            (mh-speed-flists-inhibit-flag t))
        (maphash (lambda (folder msgs)
                   (push folder folders)
                   ;; Add messages to sequence in source folder...
                   (apply #'mh-exec-cmd-quiet nil "mark" folder
                          "-add" "-nozero" "-sequence" (symbol-name seq)
                          (mapcar (lambda (x) (format "%s" x))
                                  (mh-coalesce-msg-list msgs)))
                   ;; Update source folder buffer if we have it open...
                   (when (get-buffer folder)
                     (with-current-buffer folder
                       (mh-put-msg-in-seq msgs seq))))
                 (mh-index-matching-source-msgs msgs))
        folders))))

;;;###mh-autoload
(defun mh-index-delete-from-sequence (seq msgs)
  "Delete from SEQ the messages in MSGS.
This function updates the source folder sequences. Also makes an
attempt to update the source folder buffer if present."
  (save-excursion
    (when (and (not (memq seq (mh-unpropagated-sequences)))
               (mh-valid-seq-p seq))
      (let ((folders ())
            (mh-speed-flists-inhibit-flag t))
        (maphash (lambda (folder msgs)
                   (push folder folders)
                   ;; Remove messages from sequence in source folder...
                   (apply #'mh-exec-cmd-quiet nil "mark" folder
                          "-del" "-nozero" "-sequence" (symbol-name seq)
                          (mapcar (lambda (x) (format "%s" x))
                                  (mh-coalesce-msg-list msgs)))
                   ;; Update source folder buffer if we have it open...
                   (when (get-buffer folder)
                     (with-current-buffer folder
                       (mh-delete-msg-from-seq msgs seq t))))
                 (mh-index-matching-source-msgs msgs))
        folders))))

(defvar mh-unpropagated-sequences '(cur range subject search)
  "List of sequences that aren't preserved.")

(defun mh-unpropagated-sequences ()
  "Return a list of sequences that aren't propagated to the source folders.
It is just the sequences in the variable
`mh-unpropagated-sequences' in addition to the
Previous-Sequence (see mh-profile 5)."
  (if mh-previous-seq
      (cons mh-previous-seq mh-unpropagated-sequences)
    mh-unpropagated-sequences))

(defun mh-index-matching-source-msgs (msgs &optional delete-from-index-data)
  "Return a table of original messages and folders for messages in MSGS.
If optional argument DELETE-FROM-INDEX-DATA is non-nil, then each
of the messages, whose counter-part is found in some source
folder, is removed from `mh-index-data'."
  (let ((table (make-hash-table :test #'equal)))
    (dolist (msg msgs)
      (let* ((checksum (gethash msg mh-index-msg-checksum-map))
             (pair (gethash checksum mh-index-checksum-origin-map)))
        (when (and checksum (car pair) (cdr pair)
                   (mh-index-match-checksum (cdr pair) (car pair) checksum))
          (push (cdr pair) (gethash (car pair) table))
          (when delete-from-index-data
            (remhash (cdr pair) (gethash (car pair) mh-index-data))))))
    table))

(defun mh-index-match-checksum (msg folder checksum)
  "Check if MSG in FOLDER has X-MHE-Checksum header value of CHECKSUM."
  (with-temp-buffer
    (mh-exec-cmd-output mh-scan-prog nil "-width" "80"
                        "-format" "%{x-mhe-checksum}\n" folder msg)
    (goto-char (point-min))
    (string-equal (buffer-substring-no-properties
                   (point) (mh-line-end-position))
                  checksum)))



;;; Serialization of Index Data

(defun mh-index-write-data ()
  "Write index data to file."
  (ignore-errors
    (unless (eq major-mode 'mh-folder-mode)
      (error "Can't be called from folder in \"%s\"" major-mode))
    (let ((data mh-index-data)
          (msg-checksum-map mh-index-msg-checksum-map)
          (checksum-origin-map mh-index-checksum-origin-map)
          (previous-search mh-index-previous-search)
          (sequence-search-flag mh-index-sequence-search-flag)
          (outfile (concat buffer-file-name mh-index-data-file))
          (print-length nil)
          (print-level nil))
      (with-temp-file outfile
        (mh-index-write-hashtable
         data (lambda (x) (cl-loop for y being the hash-keys of x collect y)))
        (mh-index-write-hashtable msg-checksum-map #'identity)
        (mh-index-write-hashtable checksum-origin-map #'identity)
        (pp previous-search (current-buffer)) (insert "\n")
        (pp sequence-search-flag (current-buffer)) (insert "\n")))))

(defun mh-index-write-hashtable (table proc)
  "Write TABLE to `current-buffer'.
PROC is used to serialize the values corresponding to the hash
table keys."
  (pp (cl-loop for x being the hash-keys of table
               collect (cons x (funcall proc (gethash x table))))
      (current-buffer))
  (insert "\n"))

;;;###mh-autoload
(defun mh-index-read-data ()
  "Read index data from file."
  (ignore-errors
    (unless (eq major-mode 'mh-folder-mode)
      (error "Can't be called from folder in \"%s\"" major-mode))
    (let ((infile (concat buffer-file-name mh-index-data-file))
          t1 t2 t3 t4 t5)
      (with-temp-buffer
        (insert-file-contents-literally infile)
        (goto-char (point-min))
        (setq t1 (mh-index-read-hashtable
                  (lambda (data)
                    (cl-loop with table = (make-hash-table :test #'equal)
                             for x in data do (setf (gethash x table) t)
                             finally return table)))
              t2 (mh-index-read-hashtable #'identity)
              t3 (mh-index-read-hashtable #'identity)
              t4 (read (current-buffer))
              t5 (read (current-buffer))))
      (setq mh-index-data t1
            mh-index-msg-checksum-map t2
            mh-index-checksum-origin-map t3
            mh-index-previous-search t4
            mh-index-sequence-search-flag t5))))

(defun mh-index-read-hashtable (proc)
  "From BUFFER read a hash table serialized as a list.
PROC is used to convert the value to actual data."
  (cl-loop with table = (make-hash-table :test #'equal)
           for pair in (read (current-buffer))
           do (setf (gethash (car pair) table) (funcall proc (cdr pair)))
           finally return table))



;;; Checksum Routines

;; A few different checksum programs are supported. The supported
;; programs are:

;;   1. md5sum
;;   2. md5
;;   3. openssl

;; To add support for your favorite checksum program add a clause to
;; the cond statement in mh-checksum-choose. This should set the
;; variable mh-checksum-cmd to the command line needed to run the
;; checksum program and should set mh-checksum-parser to a function
;; which returns a cons cell containing the message number and
;; checksum string.

(defvar mh-checksum-cmd)
(defvar mh-checksum-parser)

(defun mh-checksum-choose ()
  "Check if a program to create a checksum is present."
  (unless (boundp 'mh-checksum-cmd)
    (let ((exec-path (append '("/sbin" "/usr/sbin") exec-path)))
      (cond ((executable-find "md5sum")
             (setq mh-checksum-cmd (list (executable-find "md5sum")))
             (setq mh-checksum-parser #'mh-md5sum-parser))
            ((executable-find "openssl")
             (setq mh-checksum-cmd (list (executable-find "openssl") "md5"))
             (setq mh-checksum-parser #'mh-openssl-parser))
            ((executable-find "md5")
             (setq mh-checksum-cmd (list (executable-find "md5")))
             (setq mh-checksum-parser #'mh-md5-parser))
            (t (error "No suitable checksum program"))))))

(defun mh-md5sum-parser ()
  "Parse md5sum output."
  (let ((begin (mh-line-beginning-position))
        (end (mh-line-end-position))
        first-space last-slash)
    (setq first-space (search-forward " " end t))
    (goto-char end)
    (setq last-slash (search-backward "/" begin t))
    (cond ((and first-space last-slash)
           (cons (string-to-number (buffer-substring-no-properties
                                    (1+ last-slash) end))
                 (buffer-substring-no-properties begin (1- first-space))))
          (t (cons nil nil)))))

(defun mh-openssl-parser ()
  "Parse openssl output."
  (let ((begin (mh-line-beginning-position))
        (end (mh-line-end-position))
        last-space last-slash)
    (goto-char end)
    (setq last-space (search-backward " " begin t))
    (setq last-slash (search-backward "/" begin t))
    (cond ((and last-slash last-space)
           (cons (string-to-number (buffer-substring-no-properties
                                    (1+ last-slash) (1- last-space)))
                 (buffer-substring-no-properties (1+ last-space) end))))))

(defalias 'mh-md5-parser 'mh-openssl-parser)

;;;###mh-autoload
(defun mh-index-update-maps (folder &optional origin-map)
  "Annotate all as yet unannotated messages in FOLDER with their MD5 hash.
As a side effect msg -> checksum map is updated. Optional
argument ORIGIN-MAP is a hash table which maps each message in the
index folder to the original folder and message from whence it
was copied. If present the checksum -> (origin-folder,
origin-index) map is updated too."
  (clrhash mh-index-msg-checksum-map)
  ;; Clear temp buffer
  (with-current-buffer (get-buffer-create mh-temp-checksum-buffer)
    (erase-buffer)
    ;; Run scan to check if any messages needs MD5 annotations at all
    (with-temp-buffer
      (mh-exec-cmd-output mh-scan-prog nil "-width" "80"
                          "-format" "%(msg)\n%{x-mhe-checksum}\n"
                          folder "all")
      (goto-char (point-min))
      (let (msg checksum)
        (while (not (eobp))
          (setq msg (buffer-substring-no-properties
                     (point) (mh-line-end-position)))
          (forward-line)
          (save-excursion
            (cond ((not (string-match "^[0-9]*$" msg)))
                  ((eolp)
                   ;; need to compute checksum
                   (set-buffer mh-temp-checksum-buffer)
                   (insert mh-user-path (substring folder 1) "/" msg "\n"))
                  (t
                   ;; update maps
                   (setq checksum (buffer-substring-no-properties
                                   (point) (mh-line-end-position)))
                   (let ((msg (string-to-number msg)))
                     (set-buffer folder)
                     (mh-index-update-single-msg msg checksum origin-map)))))
          (forward-line))))
    ;; Run checksum program if needed
    (unless (and (eobp) (bobp))
      (apply #'mh-xargs mh-checksum-cmd)
      (goto-char (point-min))
      (while (not (eobp))
        (let* ((intermediate (funcall mh-checksum-parser))
               (msg (car intermediate))
               (checksum (cdr intermediate)))
          (when msg
            ;; annotate
            (mh-exec-cmd "anno" folder msg "-component" "X-MHE-Checksum"
                         "-nodate" "-text" checksum "-inplace")
            ;; update maps
            (with-current-buffer folder
              (mh-index-update-single-msg msg checksum origin-map)))
          (forward-line)))))
  (mh-index-write-data))

(defun mh-index-update-single-msg (msg checksum origin-map)
  "Update various maps for one message.
MSG is an index folder message, CHECKSUM its MD5 hash and
ORIGIN-MAP, if non-nil, a hash table containing which maps each
message in the index folder to the folder and message that it was
copied from. The function updates the hash tables
`mh-index-msg-checksum-map' and `mh-index-checksum-origin-map'.

This function should only be called in the appropriate index
folder buffer."
  (cond ((gethash checksum mh-index-checksum-origin-map)
         (when origin-map
           (let* ((intermediate (gethash msg origin-map))
                  (ofolder (car intermediate))
                  (omsg (cdr intermediate)))
             ;; This is most probably a duplicate. So eliminate it.
             (call-process "rm" nil nil nil
                           (format "%s%s/%s" mh-user-path
                                   (substring mh-current-folder 1) msg))
             (when (gethash ofolder mh-index-data)
               (remhash omsg (gethash ofolder mh-index-data))))))
        (t
         (setf (gethash msg mh-index-msg-checksum-map) checksum)
         (when (and origin-map (gethash msg origin-map))
           (setf (gethash checksum mh-index-checksum-origin-map)
                 (gethash msg origin-map))))))


(provide 'mh-search)

;; Local Variables:
;; indent-tabs-mode: nil
;; sentence-end-double-space: nil
;; End:

;;; mh-search ends here
