/* mailstore-files.c - Original notmuch mail store - a collection of
 * plain-text email messages (one message per file).
 *
 * Copyright © 2009 Carl Worth
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see http://www.gnu.org/licenses/ .
 *
 * Authors: Carl Worth <cworth@cworth.org>
 * 	    Michal Sojka <sojkam1@fel.cvut.cz>
 */

#define _GNU_SOURCE		/* For asprintf() */
#include "notmuch.h"
#include "mailstore-private.h"
#include <dirent.h>

typedef struct _filename_node {
    char *filename;
    struct _filename_node *next;
} _filename_node_t;

typedef struct _filename_list {
    _filename_node_t *head;
    _filename_node_t **tail;
} _filename_list_t;

typedef struct _indexing_context_priv {
    _filename_list_t *removed_files;
    _filename_list_t *removed_directories;
} _indexing_context_priv_t;

static _filename_list_t *
_filename_list_create (const void *ctx)
{
    _filename_list_t *list;

    list = talloc (ctx, _filename_list_t);
    if (list == NULL)
	return NULL;

    list->head = NULL;
    list->tail = &list->head;

    return list;
}

static void
_filename_list_add (_filename_list_t *list,
		    const char *filename)
{
    _filename_node_t *node = talloc (list, _filename_node_t);

    node->filename = talloc_strdup (list, filename);
    node->next = NULL;

    *(list->tail) = node;
    list->tail = &node->next;
}

static void
tag_inbox_and_unread (notmuch_message_t *message)
{
    notmuch_message_add_tag (message, "inbox");
    notmuch_message_add_tag (message, "unread");
}

static int
dirent_sort_inode (const struct dirent **a, const struct dirent **b)
{
    return ((*a)->d_ino < (*b)->d_ino) ? -1 : 1;
}

static int
dirent_sort_strcmp_name (const struct dirent **a, const struct dirent **b)
{
    return strcmp ((*a)->d_name, (*b)->d_name);
}

/* Test if the directory looks like a Maildir directory.
 *
 * Search through the array of directory entries to see if we can find all
 * three subdirectories typical for Maildir, that is "new", "cur", and "tmp".
 *
 * Return 1 if the directory looks like a Maildir and 0 otherwise.
 */
static int
_entries_resemble_maildir (struct dirent **entries, int count)
{
    int i, found = 0;

    for (i = 0; i < count; i++) {
	if (entries[i]->d_type != DT_DIR && entries[i]->d_type != DT_UNKNOWN)
	    continue;

	if (strcmp(entries[i]->d_name, "new") == 0 ||
	    strcmp(entries[i]->d_name, "cur") == 0 ||
	    strcmp(entries[i]->d_name, "tmp") == 0)
	{
	    found++;
	    if (found == 3)
		return 1;
	}
    }

    return 0;
}


/* Examine 'path' recursively as follows:
 *
 *   o Ask the filesystem for the mtime of 'path' (fs_mtime)
 *   o Ask the database for its timestamp of 'path' (db_mtime)
 *
 *   o Ask the filesystem for files and directories within 'path'
 *     (via scandir and stored in fs_entries)
 *   o Ask the database for files and directories within 'path'
 *     (db_files and db_subdirs)
 *
 *   o Pass 1: For each directory in fs_entries, recursively call into
 *     this same function.
 *
 *   o Pass 2: If 'fs_mtime' > 'db_mtime', then walk fs_entries
 *     simultaneously with db_files and db_subdirs. Look for one of
 *     three interesting cases:
 *
 *	   1. Regular file in fs_entries and not in db_files
 *            This is a new file to add_message into the database.
 *
 *         2. Filename in db_files not in fs_entries.
 *            This is a file that has been removed from the mail store.
 *
 *         3. Directory in db_subdirs not in fs_entries
 *            This is a directory that has been removed from the mail store.
 *
 *     Note that the addition of a directory is not interesting here,
 *     since that will have been taken care of in pass 1. Also, we
 *     don't immediately act on file/directory removal since we must
 *     ensure that in the case of a rename that the new filename is
 *     added before the old filename is removed, (so that no
 *     information is lost from the database).
 *
 *   o Tell the database to update its time of 'path' to 'fs_mtime'
 */
static notmuch_status_t
add_files_recursive (notmuch_mailstore_t *mailstore,
		     const char *path,
		     notmuch_indexing_context_t *state)
{
    DIR *dir = NULL;
    struct dirent *entry = NULL;
    char *next = NULL;
    time_t fs_mtime, db_mtime;
    notmuch_status_t status, ret = NOTMUCH_STATUS_SUCCESS;
    notmuch_message_t *message = NULL;
    struct dirent **fs_entries = NULL;
    int i, num_fs_entries;
    notmuch_directory_t *directory;
    notmuch_filenames_t *db_files = NULL;
    notmuch_filenames_t *db_subdirs = NULL;
    struct stat st;
    notmuch_bool_t is_maildir, new_directory;
    _indexing_context_priv_t *priv = state->priv;
    notmuch_database_t *notmuch = mailstore->notmuch;

    if (stat (path, &st)) {
	fprintf (stderr, "Error reading directory %s: %s\n",
		 path, strerror (errno));
	return NOTMUCH_STATUS_FILE_ERROR;
    }

    /* This is not an error since we may have recursed based on a
     * symlink to a regular file, not a directory, and we don't know
     * that until this stat. */
    if (! S_ISDIR (st.st_mode))
	return NOTMUCH_STATUS_SUCCESS;

    fs_mtime = st.st_mtime;

    directory = notmuch_database_get_directory (notmuch, path);
    db_mtime = notmuch_directory_get_mtime (directory);

    if (db_mtime == 0) {
	new_directory = TRUE;
	db_files = NULL;
	db_subdirs = NULL;
    } else {
	new_directory = FALSE;
	db_files = notmuch_directory_get_child_files (directory);
	db_subdirs = notmuch_directory_get_child_directories (directory);
    }

    /* If the database knows about this directory, then we sort based
     * on strcmp to match the database sorting. Otherwise, we can do
     * inode-based sorting for faster filesystem operation. */
    num_fs_entries = scandir (path, &fs_entries, 0,
			      new_directory ?
			      dirent_sort_inode : dirent_sort_strcmp_name);

    if (num_fs_entries == -1) {
	fprintf (stderr, "Error opening directory %s: %s\n",
		 path, strerror (errno));
	ret = NOTMUCH_STATUS_FILE_ERROR;
	goto DONE;
    }

    /* Pass 1: Recurse into all sub-directories. */
    is_maildir = _entries_resemble_maildir (fs_entries, num_fs_entries);

    for (i = 0; i < num_fs_entries; i++) {
	if (state->interrupted)
	    break;

	entry = fs_entries[i];

	/* We only want to descend into directories.
	 * But symlinks can be to directories too, of course.
	 *
	 * And if the filesystem doesn't tell us the file type in the
	 * scandir results, then it might be a directory (and if not,
	 * then we'll stat and return immediately in the next level of
	 * recursion). */
	if (entry->d_type != DT_DIR &&
	    entry->d_type != DT_LNK &&
	    entry->d_type != DT_UNKNOWN)
	{
	    continue;
	}

	/* Ignore special directories to avoid infinite recursion.
	 * Also ignore the .notmuch directory and any "tmp" directory
	 * that appears within a maildir.
	 */
	/* XXX: Eventually we'll want more sophistication to let the
	 * user specify files to be ignored. */
	if (strcmp (entry->d_name, ".") == 0 ||
	    strcmp (entry->d_name, "..") == 0 ||
	    (is_maildir && strcmp (entry->d_name, "tmp") == 0) ||
	    strcmp (entry->d_name, ".notmuch") ==0)
	{
	    continue;
	}

	next = talloc_asprintf (notmuch, "%s/%s", path, entry->d_name);
	status = add_files_recursive (mailstore, next, state);
	if (status && ret == NOTMUCH_STATUS_SUCCESS)
	    ret = status;
	talloc_free (next);
	next = NULL;
    }

    /* If this directory hasn't been modified since the last
     * "notmuch new", then we can skip the second pass entirely. */
    if (fs_mtime <= db_mtime)
	goto DONE;

    /* Pass 2: Scan for new files, removed files, and removed directories. */
    for (i = 0; i < num_fs_entries; i++)
    {
	if (state->interrupted)
	    break;

        entry = fs_entries[i];

	/* Check if we've walked past any names in db_files or
	 * db_subdirs. If so, these have been deleted. */
	while (notmuch_filenames_valid (db_files) &&
	       strcmp (notmuch_filenames_get (db_files), entry->d_name) < 0)
	{
	    char *absolute = talloc_asprintf (priv->removed_files,
					      "%s/%s", path,
					      notmuch_filenames_get (db_files));

	    _filename_list_add (priv->removed_files, absolute);

	    notmuch_filenames_move_to_next (db_files);
	}

	while (notmuch_filenames_valid (db_subdirs) &&
	       strcmp (notmuch_filenames_get (db_subdirs), entry->d_name) <= 0)
	{
	    const char *filename = notmuch_filenames_get (db_subdirs);

	    if (strcmp (filename, entry->d_name) < 0)
	    {
		char *absolute = talloc_asprintf (priv->removed_directories,
						  "%s/%s", path, filename);

		_filename_list_add (priv->removed_directories, absolute);
	    }

	    notmuch_filenames_move_to_next (db_subdirs);
	}

	/* If we're looking at a symlink, we only want to add it if it
	 * links to a regular file, (and not to a directory, say).
	 *
	 * Similarly, if the file is of unknown type (due to filesytem
	 * limitations), then we also need to look closer.
	 *
	 * In either case, a stat does the trick.
	 */
	if (entry->d_type == DT_LNK || entry->d_type == DT_UNKNOWN) {
	    int err;

	    next = talloc_asprintf (notmuch, "%s/%s", path, entry->d_name);
	    err = stat (next, &st);
	    talloc_free (next);
	    next = NULL;

	    /* Don't emit an error for a link pointing nowhere, since
	     * the directory-traversal pass will have already done
	     * that. */
	    if (err)
		continue;

	    if (! S_ISREG (st.st_mode))
		continue;
	} else if (entry->d_type != DT_REG) {
	    continue;
	}

	/* Don't add a file that we've added before. */
	if (notmuch_filenames_valid (db_files) &&
	    strcmp (notmuch_filenames_get (db_files), entry->d_name) == 0)
	{
	    notmuch_filenames_move_to_next (db_files);
	    continue;
	}

	/* We're now looking at a regular file that doesn't yet exist
	 * in the database, so add it. */
	next = talloc_asprintf (notmuch, "%s/%s", path, entry->d_name);

	state->processed_files++;

	if (state->verbose && state->print_verbose_cb)
	    state->print_verbose_cb(state, next);

	status = notmuch_database_add_message (notmuch, next, &message);
	switch (status) {
	/* success */
	case NOTMUCH_STATUS_SUCCESS:
	    state->added_messages++;
	    tag_inbox_and_unread (message);
	    break;
	/* Non-fatal issues (go on to next file) */
	case NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID:
	    /* Stay silent on this one. */
	    break;
	case NOTMUCH_STATUS_FILE_NOT_EMAIL:
	    fprintf (stderr, "Note: Ignoring non-mail file: %s\n",
		     next);
	    break;
	/* Fatal issues. Don't process anymore. */
	case NOTMUCH_STATUS_READ_ONLY_DATABASE:
	case NOTMUCH_STATUS_XAPIAN_EXCEPTION:
	case NOTMUCH_STATUS_OUT_OF_MEMORY:
	    fprintf (stderr, "Error: %s. Halting processing.\n",
		     notmuch_status_to_string (status));
	    ret = status;
	    goto DONE;
	default:
	case NOTMUCH_STATUS_FILE_ERROR:
	case NOTMUCH_STATUS_NULL_POINTER:
	case NOTMUCH_STATUS_TAG_TOO_LONG:
	case NOTMUCH_STATUS_UNBALANCED_FREEZE_THAW:
	case NOTMUCH_STATUS_LAST_STATUS:
	    INTERNAL_ERROR ("add_message returned unexpected value: %d",  status);
	    goto DONE;
	}

	if (message) {
	    notmuch_message_destroy (message);
	    message = NULL;
	}

	if (state->print_progress &&
	    state->print_progress_cb) {
	    state->print_progress = 0;
	    state->print_progress_cb (state);
	}

	talloc_free (next);
	next = NULL;
    }

    if (state->interrupted)
	goto DONE;

    /* Now that we've walked the whole filesystem list, anything left
     * over in the database lists has been deleted. */
    while (notmuch_filenames_valid (db_files))
    {
	char *absolute = talloc_asprintf (priv->removed_files,
					  "%s/%s", path,
					  notmuch_filenames_get (db_files));

	_filename_list_add (priv->removed_files, absolute);

	notmuch_filenames_move_to_next (db_files);
    }

    while (notmuch_filenames_valid (db_subdirs))
    {
	char *absolute = talloc_asprintf (priv->removed_directories,
					  "%s/%s", path,
					  notmuch_filenames_get (db_subdirs));

	_filename_list_add (priv->removed_directories, absolute);

	notmuch_filenames_move_to_next (db_subdirs);
    }

    if (! state->interrupted) {
	status = notmuch_directory_set_mtime (directory, fs_mtime);
	if (status && ret == NOTMUCH_STATUS_SUCCESS)
	    ret = status;
    }

DONE:
    if (next)
	talloc_free (next);
    if (entry)
	free (entry);
    if (dir)
	closedir (dir);
    if (fs_entries)
	free (fs_entries);
    if (db_subdirs)
	notmuch_filenames_destroy (db_subdirs);
    if (db_files)
	notmuch_filenames_destroy (db_files);
    if (directory)
	notmuch_directory_destroy (directory);

    return ret;
}

/* XXX: This should be merged with the add_files function since it
 * shares a lot of logic with it. */
/* Recursively count all regular files in path and all sub-directories
 * of path.  The result is added to *count (which should be
 * initialized to zero by the top-level caller before calling
 * count_files). */
static void
count_files (notmuch_mailstore_t *mailstore,
	     const char *path, int *count,
	     volatile sig_atomic_t *interrupted)
{
    struct dirent *entry = NULL;
    char *next;
    struct stat st;
    struct dirent **fs_entries = NULL;
    int num_fs_entries = scandir (path, &fs_entries, 0, dirent_sort_inode);
    int i = 0;

    (void)mailstore;
    if (num_fs_entries == -1) {
	fprintf (stderr, "Warning: failed to open directory %s: %s\n",
		 path, strerror (errno));
	goto DONE;
    }

    while (!*interrupted) {
        if (i == num_fs_entries)
	    break;

        entry = fs_entries[i++];

	/* Ignore special directories to avoid infinite recursion.
	 * Also ignore the .notmuch directory.
	 */
	/* XXX: Eventually we'll want more sophistication to let the
	 * user specify files to be ignored. */
	if (strcmp (entry->d_name, ".") == 0 ||
	    strcmp (entry->d_name, "..") == 0 ||
	    strcmp (entry->d_name, ".notmuch") == 0)
	{
	    continue;
	}

	if (asprintf (&next, "%s/%s", path, entry->d_name) == -1) {
	    next = NULL;
	    fprintf (stderr, "Error descending from %s to %s: Out of memory\n",
		     path, entry->d_name);
	    continue;
	}

	stat (next, &st);

	if (S_ISREG (st.st_mode)) {
	    *count = *count + 1;
	    if (*count % 1000 == 0) {
		printf ("Found %d files so far.\r", *count);
		fflush (stdout);
	    }
	} else if (S_ISDIR (st.st_mode)) {
	    count_files (mailstore, next, count, interrupted);
	}

	free (next);
    }

DONE:
    if (entry)
	free (entry);
    if (fs_entries)
        free (fs_entries);
}

/* Recursively remove all filenames from the database referring to
 * 'path' (or to any of its children). */
static void
_remove_directory (void *ctx,
		   notmuch_database_t *notmuch,
		   const char *path,
		   int *renamed_files,
		   int *removed_files)
{
    notmuch_directory_t *directory;
    notmuch_filenames_t *files, *subdirs;
    notmuch_status_t status;
    char *absolute;

    directory = notmuch_database_get_directory (notmuch, path);

    for (files = notmuch_directory_get_child_files (directory);
	 notmuch_filenames_valid (files);
	 notmuch_filenames_move_to_next (files))
    {
	absolute = talloc_asprintf (ctx, "%s/%s", path,
				    notmuch_filenames_get (files));
	status = notmuch_database_remove_message (notmuch, absolute);
	if (status == NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID)
	    *renamed_files = *renamed_files + 1;
	else
	    *removed_files = *removed_files + 1;
	talloc_free (absolute);
    }

    for (subdirs = notmuch_directory_get_child_directories (directory);
	 notmuch_filenames_valid (subdirs);
	 notmuch_filenames_move_to_next (subdirs))
    {
	absolute = talloc_asprintf (ctx, "%s/%s", path,
				    notmuch_filenames_get (subdirs));
	_remove_directory (ctx, notmuch, absolute, renamed_files, removed_files);
	talloc_free (absolute);
    }

    notmuch_directory_destroy (directory);
}

static notmuch_private_status_t
index_new(notmuch_mailstore_t *mailstore, const char* path,
	  notmuch_indexing_context_t *indexing_ctx)
{
    _indexing_context_priv_t *priv;
    _filename_node_t *f;
    notmuch_status_t status, ret;
    notmuch_database_t *notmuch = mailstore->notmuch;

    priv = talloc(NULL, _indexing_context_priv_t);
    indexing_ctx->priv = priv;
    if (priv == NULL)
	return NOTMUCH_STATUS_OUT_OF_MEMORY;

    priv->removed_files = _filename_list_create (priv);
    priv->removed_directories = _filename_list_create (priv);

    ret = add_files_recursive(mailstore, path, indexing_ctx);

    indexing_ctx->removed_files = 0;
    indexing_ctx->renamed_files = 0;
    for (f = priv->removed_files->head; f; f = f->next) {
	status = notmuch_database_remove_message (notmuch, f->filename);
	if (status == NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID)
	    indexing_ctx->renamed_files++;
	else
	    indexing_ctx->removed_files++;
    }

    for (f = priv->removed_directories->head; f; f = f->next) {
	_remove_directory (priv, notmuch, f->filename,
			   &indexing_ctx->renamed_files,
			   &indexing_ctx->removed_files);
    }

    talloc_free(priv);

    return ret;
}

/* Original notmuch mail store */
struct _notmuch_mailstore mailstore_files = {
    .type = "files",
    .count_files = count_files,
    .index_new = index_new,
    .sync_tags = NULL,		/* We cannot store tags in this mailstore. */
    .open_file = NULL,		/* Currently not implemented */
};