/* partlist.c - Partition/backend selection functions
 *
 * Copyright (c) 1994-2008 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/types.h>


#include "libconfig.h"
#include "partlist.h"
#include "util.h"
#include "xmalloc.h"


#define FREE(var) if (var) { free(var); (var) = NULL; }

static void partlist_bump_action(partlist_t *part_list);
static int partlist_selectpart_index(partlist_t *part_list);
static void partlist_compute_quota(partlist_t *part_list);
static void partlist_fill(const char *key, const char *value, void *rock);
static void partition_filldata(partlist_t *part_list, int idx);

typedef struct partlist_conf {
    partlist_t  *part_list;
    const char  *key_prefix;
    size_t      excluded_count;
    const char  **excluded_item;
} partlist_conf_t;

static partlist_t *partlist_local = NULL;


EXPORTED partmode_t partlist_getmode(const char *mode)
{
    if (!strcmp(mode, "freespace-most")) {
        return PART_SELECT_MODE_FREESPACE_MOST;
    }
    else if (!strcmp(mode, "freespace-percent-most")) {
        return PART_SELECT_MODE_FREESPACE_PERCENT_MOST;
    }
    else if (!strcmp(mode, "freespace-percent-weighted")) {
        return PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED;
    }
    else if (!strcmp(mode, "freespace-percent-weighted-delta")) {
        return PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED_DELTA;
    }
    else {
        return PART_SELECT_MODE_RANDOM;
    }
}


EXPORTED void partlist_initialize(partlist_t *part_list, cb_part_filldata filldata,
                         const char *key_prefix, const char *key_value,
                         const char *excluded, partmode_t mode,
                         int soft_usage_limit, int reinit)
{
    partlist_conf_t part_list_conf;
    char *excluded_parts = NULL;

    srand(time(NULL));
    memset(&part_list_conf, 0, sizeof(part_list_conf));
    memset(part_list, 0, sizeof(partlist_t));

    part_list->mode = mode;
    part_list->filldata = (filldata ? filldata : partition_filldata);
    part_list->size = 0;
    part_list->soft_usage_limit = soft_usage_limit;
    part_list->reinit = reinit;

    part_list_conf.part_list = part_list;
    part_list_conf.key_prefix = key_prefix;

    if (excluded && (strlen(excluded) > 0)) {
        char *item = NULL;
        char *lasts;

        excluded_parts = xstrdup(excluded);
        item = strtok_r(excluded_parts, " ,\t", &lasts);
        while (item) {
            part_list_conf.excluded_item = (const char **)xrealloc(part_list_conf.excluded_item, (part_list_conf.excluded_count+1) * sizeof(const char *));
            part_list_conf.excluded_item[part_list_conf.excluded_count++] = item;
            item = strtok_r(NULL, " ,\t", &lasts);
        }
    }

    if (key_value) {
        char *items = xstrdup(key_value);
        char *item = NULL;
        char *lasts;

        item = strtok_r(items, " ,\t", &lasts);
        while (item) {
            partlist_fill(item, item, &part_list_conf);
            item = strtok_r(NULL, " ,\t", &lasts);
        }

        FREE(items);
    }
    else {
        config_foreachoverflowstring(partlist_fill, &part_list_conf);
    }

    /* excluded items no more necessary */
    FREE(excluded_parts);
    FREE(part_list_conf.excluded_item);

    partlist_compute_quota(part_list);
}


EXPORTED void partlist_free(partlist_t *part_list)
{
    int i;

    if (part_list == NULL) {
        return;
    }

    for (i = 0; i < part_list->size; i++) {
        FREE(part_list->items[i].item);
        FREE(part_list->items[i].value);
    }
    FREE(part_list->items);
    part_list->size = -1;
}


static void partlist_bump_action(partlist_t *part_list)
{
    if ((part_list->reinit > 0) && (part_list->reinit_counter++ >= part_list->reinit)) {
        partlist_compute_quota(part_list);
        part_list->reinit_counter = 1;
    }
}


static int partlist_getavailable(partlist_t *part_list)
{
    int count = 0;
    int idx;

    for (idx = 0; idx < part_list->size; idx++) {
        if (part_list->items[idx].quota != 0.) {
            count++;
        }
    }

    /* When nothing available, refresh quotas after a while */
    if (!count) {
        partlist_bump_action(part_list);
    }

    return count;
}


static const char *partlist_select_item(partlist_t *part_list)
{
    int idx = partlist_selectpart_index(part_list);

    return (idx == -1 ? NULL : part_list->items[idx].item);
}


EXPORTED const char *partlist_select_value(partlist_t *part_list)
{
    int idx = partlist_selectpart_index(part_list);

    return (idx == -1 ? NULL : part_list->items[idx].value);
}

EXPORTED int partlist_foreach(partlist_t *part_list,
                              partlist_foreach_cb proc,
                              void *rock)
{
    int i, r = -1;

    for (i = 0; i < part_list->size; i++) {
        r = proc(&part_list->items[i], rock);

        if (r) break;
    }

    return r;
}

static int partlist_selectpart_index(partlist_t *part_list)
{
    int i;
    int do_random = 0;
    int ret = -1;
    int available;

    if (part_list->size <= 0) {
        return -1;
    }

    available = partlist_getavailable(part_list);
    if (!available) {
        return -1;
    }

    partlist_bump_action(part_list);

    if ((part_list->mode == PART_SELECT_MODE_RANDOM) || part_list->force_random) {
        do_random = 1;
    }
    else {
        double sq = 0.;
        double val = 0.;
        uint64_t max_available = 0;

        switch (part_list->mode) {
        case PART_SELECT_MODE_FREESPACE_MOST:
            for (i = 0; i < part_list->size; i++) {
                if (part_list->items[i].quota == 0.) {
                    continue;
                }

                if (part_list->items[i].available > max_available) {
                    ret = i;
                    max_available = part_list->items[i].available;
                }
            }
            break;

        case PART_SELECT_MODE_FREESPACE_PERCENT_MOST:
            for (i = 0 ;i < part_list->size; i++) {
                if (part_list->items[i].quota == 0.) {
                    continue;
                }

                if (part_list->items[i].quota > val) {
                    ret = i;
                    val = part_list->items[i].quota;
                }
            }
            break;

        case PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED:
        case PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED_DELTA:
            /* random in [0,100[ */
            val = 100. * ((double)rand() / (RAND_MAX + 1.));

            for (i = 0; i < part_list->size; i++) {
                sq += part_list->items[i].quota;
                ret = i;
                if (val < sq) {
                    break;
                }
            }

            /* sanity check: make sure we did not pick an unwanted entry
               and get last wanted one (or -1 if all items are unwanted) */
            while ((part_list->items[ret].quota == 0.) && (--ret >= 0))
                ;
            break;

        default:
            /* sanity check */
            do_random = 1;
            break;
        }
    }

    if (do_random) {
        i = rand() % available;
        ret = 0;
        while (i--) {
            while (part_list->items[++ret].quota == 0.)
                ;
        }
    }

    return ret;
}


static void partlist_compute_quota(partlist_t *part_list)
{
    int i;
    int j;
    unsigned long id;
    double percent_available;
    double quota_total = 0;
    double quota_min = 100.;
    double quota_min_limit = 100.;
    double soft_quota_limit = 100. - part_list->soft_usage_limit;
    int soft_quota_limit_use = 0;
    partmode_t mode = part_list->mode;

    part_list->force_random = 0;

    if (mode == PART_SELECT_MODE_RANDOM) {
        /* No need to check items usage */
        for (i = 0; i < part_list->size; i++) {
            part_list->items[i].quota = 50.0;
        }

        return;
    }

    for (i = 0; i < part_list->size; i++) {
        part_list->filldata(part_list, i);

        if ((mode == PART_SELECT_MODE_FREESPACE_MOST) || (mode == PART_SELECT_MODE_FREESPACE_PERCENT_MOST)) {
            id = part_list->items[i].id;
            for (j = i-1; j >= 0; j--) {
                if (id == part_list->items[j].id) {
                    /* duplicate id, keep only the first of its kind */
                    part_list->items[i].quota = 0.;
                    break;
                }
            }
            if (j >= 0) {
                /* duplicate id, skip */
                continue;
            }
        }
        /* else: other modes does not need id de-duplication */

        percent_available = -1.;
        if (part_list->items[i].total > 0) {
            percent_available = (part_list->items[i].available * (double)100. / part_list->items[i].total);
        }

        /* ensure we got a consistent value */
        if ((percent_available<0.) || (percent_available>100.)) {
            /* fallback to random mode */
            part_list->force_random = 1;
            break;
        }

        part_list->items[i].quota = percent_available;
        /* Note: beware floating-point precision between variables stored in
         * memory and CPU registers. From now on, do not use percent_available.
         */

        if (part_list->items[i].quota < quota_min) {
            quota_min = part_list->items[i].quota;
        }

        /* check free space against limit */
        if (part_list->items[i].quota <= soft_quota_limit) {
            /* entry below limit, will not be taken into account (unless all
               entries are below limit) */
            continue;
        }
        /* at least one entry is ok, quota limit can be applied */
        soft_quota_limit_use = 1;
        if (part_list->items[i].quota < quota_min_limit) {
            quota_min_limit = part_list->items[i].quota;
        }
    }

    if (soft_quota_limit_use) {
        quota_min = quota_min_limit;
    }

    for (i = 0; i < part_list->size; i++) {
        if (part_list->force_random) {
            part_list->items[i].quota = 50.0;
        }
        else if (soft_quota_limit_use && (part_list->items[i].quota <= soft_quota_limit)) {
            /* entry is below limit, make sure not to select it */
            part_list->items[i].quota = 0.;
        }
        else if (mode == PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED_DELTA) {
            /* Note: according to previous tests, current item quota shall be
             * >= quota_min. Even with differences in floating-point precision
             * between variables stored in memory and CPU registers, the former
             * would be slightly under the latter, which would not matter since
             * we are about to add .5.
             */

            /* the goal is to reach the level of the most used volume */
            part_list->items[i].quota -= quota_min;
            /* but prevent the most used one to starve */
            part_list->items[i].quota += .5;

            /* Sanity check */
            if (part_list->items[i].quota < 0) {
                part_list->items[i].quota = 0.;
            }
        }
    }

    if (part_list->force_random) {
        /* nothing else to do */
        return;
    }

    if ((mode == PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED) || (mode == PART_SELECT_MODE_FREESPACE_PERCENT_WEIGHTED_DELTA)) {
        /* normalize */
        for (i = 0; i < part_list->size; i++) {
            quota_total += part_list->items[i].quota;
        }
        if (quota_total != 0) {
            for (i = 0; i < part_list->size; i++) {
                part_list->items[i].quota = (part_list->items[i].quota * 100.) / quota_total;
            }
        }
    }
}


static void partlist_fill(const char *key, const char *value, void *rock)
{
    partlist_conf_t *part_list_conf = (partlist_conf_t *)rock;
    partlist_t *part_list = part_list_conf->part_list;
    size_t key_prefix_len = (part_list_conf->key_prefix ? strlen(part_list_conf->key_prefix) : 0);
    unsigned i;

    if (key_prefix_len) {
        if ((strncmp(part_list_conf->key_prefix, key, key_prefix_len) != 0) || (strlen(key) <= key_prefix_len)) {
            return;
        }
    }

    for (i = 0; i < part_list_conf->excluded_count; i++) {
        if (!strcmp(key+key_prefix_len, (part_list_conf->excluded_item)[i])) {
            return;
        }
    }

    part_list->items = xzrealloc(part_list->items,
                                 part_list->size * sizeof(partitem_t),
                                 (part_list->size + 1) * sizeof(partitem_t));
    part_list->items[part_list->size].item = xstrdup(key + key_prefix_len);
    part_list->items[part_list->size].value = xstrdup(value);
    /* item usage data will be filled later */

    part_list->size++;
}


/**
 * \brief Fills partition data.
 *
 * @param inout part_list   items list structure
 * @param in    idx         item index
 */
static void partition_filldata(partlist_t *part_list, int idx)
{
    partitem_t *item = &part_list->items[idx];
    struct statvfs stat;

    item->id = 0;
    item->available = 0;
    item->total = 0;
    item->quota = 0.;

    if (statvfs(item->value, &stat)) {
        /* statvfs error */
        int error = 1;

        if (errno == ENOENT) {
            /* try to create path */
            if ((cyrus_mkdir(item->value, 0755) == -1) || (mkdir(item->value, 0755) == -1)) {
                syslog(LOG_ERR, "IOERROR: creating %s: %m", item->value);
                return;
            }
            else {
                error = statvfs(item->value, &stat) ? 1 : 0;
            }
        }

        if (error) {
            syslog(LOG_ERR, "IOERROR: statvfs[%s]: %m", item->value);
            return;
        }
    }

    if (stat.f_blocks <= 0) {
        /* error retrieving statvfs info */
        syslog(LOG_ERR, "IOERROR: statvfs[%s]: non-positive number of blocks", item->value);
        return;
    }

    item->id = stat.f_fsid;
    item->available = (uint64_t)(stat.f_bavail * (stat.f_frsize / 1024.));
    item->total = (uint64_t)(stat.f_blocks * (stat.f_frsize / 1024.));
}


static void partlist_local_init(void)
{
    if (partlist_local) {
        /* already done */
        return;
    }

    partlist_local = xzmalloc(sizeof(partlist_t));
    partlist_initialize(
        partlist_local,
        NULL,
        "partition-",
        NULL,
        config_getstring(IMAPOPT_PARTITION_SELECT_EXCLUDE),
        partlist_getmode(config_getstring(IMAPOPT_PARTITION_SELECT_MODE)),
        config_getint(IMAPOPT_PARTITION_SELECT_SOFT_USAGE_LIMIT),
        config_getint(IMAPOPT_PARTITION_SELECT_USAGE_REINIT)
    );
}


HIDDEN const char *partlist_local_select(void)
{
    /* lazy loading */
    if (!partlist_local) {
        partlist_local_init();
    }

    return (char *)partlist_select_item(partlist_local);
}


HIDDEN const char *partlist_local_find_freespace_most(int percent, uint64_t *available,
                                               uint64_t *total, uint64_t *tavailable,
                                               uint64_t *ttotal)
{
    const char *item = NULL;
    unsigned long id;
    uint64_t available_tmp;
    uint64_t total_tmp;
    double percent_available;
    uint64_t available_max = 0;
    double percent_available_max = 0.;
    int i;
    int j;

    /* lazy loading */
    if (!partlist_local) {
        partlist_local_init();
    }

    if (available) *available = 0;
    if (total) *total = 0;
    if (tavailable) *tavailable = 0;
    if (ttotal) *ttotal = 0;

    partlist_bump_action(partlist_local);

    for (i = 0; i < partlist_local->size; i++) {
        if (partlist_local->items[i].quota == 0.) {
            continue;
        }

        id = partlist_local->items[i].id;
        for (j = i-1; j >= 0; j--) {
            if (id == partlist_local->items[j].id) {
                /* duplicate id */
                break;
            }
        }
        if (j >= 0) {
            /* duplicate id, skip */
            continue;
        }

        available_tmp = partlist_local->items[i].available;
        total_tmp = partlist_local->items[i].total;

        if (tavailable) *tavailable += available_tmp;
        if (ttotal) *ttotal += total_tmp;

        if (percent) {
            percent_available = 0.;
            if (total_tmp > 0) {
                percent_available = (available_tmp * (double)100. / total_tmp);
            }
            if ((percent_available > percent_available_max) && (percent_available <= 100.)) {
                percent_available_max = percent_available;
                item = partlist_local->items[i].item;
                if (available) *available = available_tmp;
                if (total) *total = total_tmp;
            }
        }
        else {
            if (available_tmp > available_max) {
                available_max = available_tmp;
                item = partlist_local->items[i].item;
                if (available) *available = available_tmp;
                if (total) *total = total_tmp;
            }
        }
    }

    return item;
}


EXPORTED void partlist_local_done(void)
{
    if (partlist_local) {
        partlist_free(partlist_local);
        free(partlist_local);
        partlist_local = NULL;
    }
}
