#!/usr/bin/env python3
#
# ---------------------- faust2md ----------------------
# Usage: `faust2md [-t 4] [-c] [-f] foo.dsp > foo.md`
#
# Ultra simple automatic documentation system for Faust.
# Creates a markdown file by extracting the comments from
# a Faust file. The option -t n can be used to change the
# default (4) tab setting. The option -c can be used to
# include the Faust code itself into the generated doc.
# And the option -f can be used to include a YAML front
# matter with the name of the file and the date.
#
# The format of a title is :
#       //############# Title Name #################
#       //  markdown text....
#       //  markdown text....
#       //##########################################
#
# The format of a section is :
#       //============== Section Name ==============
#       //  markdown text....
#       //  markdown text....
#       //==========================================
#
# The format of a comment is :
#       //-------------- foo(x,y) ------------------
#       //  markdown text....
#       //  markdown text....
#       //------------------------------------------
# everything else is considered Faust code.
# The translation is the following:
#   ## foo(x,y)
#       markdown text....
#       markdown text....
# ------------------------------------------------------

import sys
import re
import datetime
import getopt


# Outdent a comment line by n characters in
# order to remove the prefix "//   "
def outdent(line, n):
    if len(line) <= n:
        return "\n"
    else:
        return line[n:]


# Match the first line of a title
# of type "//**** Title ****"
# at least 3 * are needed
def matchBeginTitle(line):
    return re.search(r'^\s*//#{3,}\s*([^#]+)#{3,}', line)


# Match the last line of a title
# of type "//********"
# or a blank line
def matchEndTitle(line):
    return re.search(r'^\s*((//#{3,})|(\s*))$', line)


# Match the first line of a section
# of type "//==== Section ===="
# at least 3 = are needed
def matchBeginSection(line):
    return re.search(r'^\s*//={3,}\s*([^=]+)={3,}', line)


# Match the last line of a section
# of type "//======="
# or a blank line
def matchEndSection(line):
    return re.search(r'^\s*((//={3,})|(\s*))$', line)


# Match the first line of a comment
# of type "//--- foo(x,y) ----"
# at least 3 - are needed
def matchBeginComment(line):
    return re.search(r'^\s*//-{3,}\s*([^-]+)-{3,}', line)


# Match the last line of a comment
# of type "//-----------------"
# or a blank line
def matchEndComment(line):
    return re.search(r'^\s*((//-{3,})|(\s*))$', line)


# Compute the indentation of a line,
# that is the position of the first word character
# after "//   "
def indentation(line):
    matchComment = re.search(r'(^\s*//\s*\w)', line)
    if matchComment:
        return len(matchComment.group(1))-1
    else:
        return 0


# Indicates if a line is a comment
def isComment(line):
    matchComment = re.search(r'^\s*//', line)
    if matchComment:
        return 1
    else:
        return 0


# Print the front matter of the file
def frontMatter(file):
    print('---')
    print('file: %s' % (file,))
    print('date: %s' % (datetime.date.today(),))
    print('---')
    print('')


#
# THE PROGRAM STARTS HERE
#
tabsize = 4             # tabsize used for expanding tabs
codeflag = 0             # 0: no source code; 1: print also source code
frontflag = 0             # 0: no front matter; 1: print front matter
mode = 0             # 0: in code; 1: in md-comment
idt = 0             # indentation retained to outdent comment lines

# Analyze command line arguments
try:
    opts, args = getopt.getopt(sys.argv[1:], "t:cf")
    if not args:
        raise getopt.error("At least one file argument required")
except getopt.error as e:
    print(e.msg)
    print("usage: %s [-t tabsize] [-c] [-f] file ..." % (sys.argv[0],))
    sys.exit(1)
for optname, optvalue in opts:
    if optname == '-t':
        tabsize = int(optvalue)
    if optname == '-c':
        codeflag = 1
    if optname == '-f':
        frontflag = 1


# Process all the files and print the documentation on the standard output
for file in args:
    with open(file) as f:
        if frontflag:
            frontMatter(file)
        for text in f:
            line = text.expandtabs(tabsize)
            if isComment(line) == 0:
                if mode == 1:
                    # we are closing a md-comment
                    print('')
                    mode = 0
                if codeflag:
                    print('\t%s' % line,)
            else:
                if mode == 0:     # we are in code
                    matchComment = matchBeginComment(line)
                    matchSection = matchBeginSection(line)
                    matchTitle = matchBeginTitle(line)
                    if matchComment:
                        print('')
                        print("### %s" % (matchComment.group(1),))
                    elif matchSection:
                        print('')
                        print("## %s" % (matchSection.group(1),))
                    elif matchTitle:
                        print('')
                        print("# %s" % (matchTitle.group(1),))
                    if matchComment or matchSection or matchTitle:
                        mode = 1  # we just started a md-comment
                        idt = 0  # we have to measure the indentation
                    else:
                        # it is a comment but not a md-comment
                        # therefore it is part of the code
                        if codeflag:
                            print('\t%s' % (line,))
                else:
                    # we are in a md-comment
                    if idt == 0:
                        # we have to measure the indentation
                        idt = indentation(line)
                    # check end of md-comment
                    matchComment = matchEndComment(line)
                    matchSection = matchEndSection(line)
                    matchTitle = matchEndTitle(line)
                    if matchComment:
                        print('')
                        print("---")
                        print('')
                    if matchComment or matchSection or matchTitle:
                        # end of md-comment switch back to mode O
                        mode = 0
                    else:
                        # lien of content of md-comment
                        # we print it unindented
                        print(outdent(line, idt)),
