/* database.cc - The database interfaces of the notmuch mail library
 *
 * 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/ .
 *
 * Author: Carl Worth <cworth@cworth.org>
 */

#include "database-private.h"

#include <iostream>

#include <xapian.h>

#include <glib.h> /* g_strdup_printf, g_free, GPtrArray, GHashTable */

using namespace std;

const char *
notmuch_status_to_string (notmuch_status_t status)
{
    switch (status) {
    case NOTMUCH_STATUS_SUCCESS:
	return "No error occurred";
    case NOTMUCH_STATUS_XAPIAN_EXCEPTION:
	return "A Xapian exception occurred";
    case NOTMUCH_STATUS_FILE_ERROR:
	return "Something went wrong trying to read or write a file";
    case NOTMUCH_STATUS_FILE_NOT_EMAIL:
	return "File is not an email";
    case NOTMUCH_STATUS_NULL_POINTER:
	return "Erroneous NULL pointer";
    case NOTMUCH_STATUS_TAG_TOO_LONG:
	return "Tag value is too long";
    default:
    case NOTMUCH_STATUS_LAST_STATUS:
	return "Unknown error status value";
    }
}

/* XXX: We should drop this function and convert all callers to call
 * _notmuch_message_add_term instead. */
static void
add_term (Xapian::Document doc,
	  const char *prefix_name,
	  const char *value)
{
    const char *prefix;
    char *term;

    if (value == NULL)
	return;

    prefix = _find_prefix (prefix_name);

    term = g_strdup_printf ("%s%s", prefix, value);

    if (strlen (term) <= NOTMUCH_TERM_MAX)
	doc.add_term (term);

    g_free (term);
}

static void
find_messages_by_term (Xapian::Database *db,
		       const char *prefix_name,
		       const char *value,
		       Xapian::PostingIterator *begin,
		       Xapian::PostingIterator *end)
{
    Xapian::PostingIterator i;
    char *term;

    term = g_strdup_printf ("%s%s", _find_prefix (prefix_name), value);

    *begin = db->postlist_begin (term);

    if (end)
	*end = db->postlist_end (term);

    free (term);
}

Xapian::Document
find_message_by_docid (Xapian::Database *db, Xapian::docid docid)
{
    return db->get_document (docid);
}

static void
insert_thread_id (GHashTable *thread_ids, Xapian::Document doc)
{
    string value_string;
    const char *value, *id, *comma;

    value_string = doc.get_value (NOTMUCH_VALUE_THREAD);
    value = value_string.c_str();
    if (strlen (value)) {
	id = value;
	while (*id) {
	    comma = strchr (id, ',');
	    if (comma == NULL)
		comma = id + strlen (id);
	    g_hash_table_insert (thread_ids,
				 strndup (id, comma - id), NULL);
	    id = comma;
	    if (*id)
		id++;
	}
    }
}

notmuch_message_t *
notmuch_database_find_message (notmuch_database_t *notmuch,
			       const char *message_id)
{
    Xapian::PostingIterator i, end;

    find_messages_by_term (notmuch->xapian_db,
			   "msgid", message_id, &i, &end);

    if (i == end)
	return NULL;

    return _notmuch_message_create (notmuch, notmuch, *i);
}

/* Return one or more thread_ids, (as a GPtrArray of strings), for the
 * given message based on looking into the database for any messages
 * referenced in parents, and also for any messages in the database
 * referencing message_id.
 *
 * Caller should free all strings in the array and the array itself,
 * (g_ptr_array_free) when done. */
static GPtrArray *
find_thread_ids (notmuch_database_t *notmuch,
		 GPtrArray *parents,
		 const char *message_id)
{
    Xapian::WritableDatabase *db = notmuch->xapian_db;
    Xapian::PostingIterator child, children_end;
    Xapian::Document doc;
    GHashTable *thread_ids;
    GList *keys, *l;
    unsigned int i;
    const char *parent_message_id;
    GPtrArray *result;

    thread_ids = g_hash_table_new_full (g_str_hash, g_str_equal,
					free, NULL);

    find_messages_by_term (db, "ref", message_id, &child, &children_end);
    for ( ; child != children_end; child++) {
	doc = find_message_by_docid (db, *child);
	insert_thread_id (thread_ids, doc);
    }

    for (i = 0; i < parents->len; i++) {
	notmuch_message_t *parent;
	notmuch_thread_ids_t *ids;

	parent_message_id = (char *) g_ptr_array_index (parents, i);
	parent = notmuch_database_find_message (notmuch, parent_message_id);
	if (parent == NULL)
	    continue;

	for (ids = notmuch_message_get_thread_ids (parent);
	     notmuch_thread_ids_has_more (ids);
	     notmuch_thread_ids_advance (ids))
	{
	    const char *id;

	    id = notmuch_thread_ids_get (ids);
	    g_hash_table_insert (thread_ids, strdup (id), NULL);
	}

	notmuch_message_destroy (parent);
    }

    result = g_ptr_array_new ();

    keys = g_hash_table_get_keys (thread_ids);
    for (l = keys; l; l = l->next) {
	char *id = (char *) l->data;
	g_ptr_array_add (result, id);
    }
    g_list_free (keys);

    /* We're done with the hash table, but we've taken the pointers to
     * the allocated strings and put them into our result array, so
     * tell the hash not to free them on its way out. */
    g_hash_table_steal_all (thread_ids);
    g_hash_table_unref (thread_ids);

    return result;
}

/* Advance 'str' past any whitespace or RFC 822 comments. A comment is
 * a (potentially nested) parenthesized sequence with '\' used to
 * escape any character (including parentheses).
 *
 * If the sequence to be skipped continues to the end of the string,
 * then 'str' will be left pointing at the final terminating '\0'
 * character.
 */
static void
skip_space_and_comments (const char **str)
{
    const char *s;

    s = *str;
    while (*s && (isspace (*s) || *s == '(')) {
	while (*s && isspace (*s))
	    s++;
	if (*s == '(') {
	    int nesting = 1;
	    s++;
	    while (*s && nesting) {
		if (*s == '(')
		    nesting++;
		else if (*s == ')')
		    nesting--;
		else if (*s == '\\')
		    if (*(s+1))
			s++;
		s++;
	    }
	}
    }

    *str = s;
}

/* Parse an RFC 822 message-id, discarding whitespace, any RFC 822
 * comments, and the '<' and '>' delimeters.
 *
 * If not NULL, then *next will be made to point to the first character
 * not parsed, (possibly pointing to the final '\0' terminator.
 *
 * Returns a newly allocated string which the caller should free()
 * when done with it.
 *
 * Returns NULL if there is any error parsing the message-id. */
static char *
parse_message_id (const char *message_id, const char **next)
{
    const char *s, *end;
    char *result;

    if (message_id == NULL)
	return NULL;

    s = message_id;

    skip_space_and_comments (&s);

    /* Skip any unstructured text as well. */
    while (*s && *s != '<')
	s++;

    if (*s == '<') {
	s++;
    } else {
	if (next)
	    *next = s;
	return NULL;
    }

    skip_space_and_comments (&s);

    end = s;
    while (*end && *end != '>')
	end++;
    if (next) {
	if (*end)
	    *next = end + 1;
	else
	    *next = end;
    }

    if (end > s && *end == '>')
	end--;
    if (end <= s)
	return NULL;

    result = strndup (s, end - s + 1);

    /* Finally, collapse any whitespace that is within the message-id
     * itself. */
    {
	char *r;
	int len;

	for (r = result, len = strlen (r); *r; r++, len--)
	    if (*r == ' ' || *r == '\t')
		memmove (r, r+1, len);
    }

    return result;
}

/* Parse a References header value, putting a copy of each referenced
 * message-id into 'array'. */
static void
parse_references (GPtrArray *array,
		  const char *refs)
{
    char *ref;

    if (refs == NULL)
	return;

    while (*refs) {
	ref = parse_message_id (refs, &refs);

	if (ref)
	    g_ptr_array_add (array, ref);
    }
}

char *
notmuch_database_default_path (void)
{
    if (getenv ("NOTMUCH_BASE"))
	return strdup (getenv ("NOTMUCH_BASE"));

    return g_strdup_printf ("%s/mail", getenv ("HOME"));
}

notmuch_database_t *
notmuch_database_create (const char *path)
{
    notmuch_database_t *notmuch = NULL;
    char *notmuch_path = NULL;
    struct stat st;
    int err;
    char *local_path = NULL;

    if (path == NULL)
	path = local_path = notmuch_database_default_path ();

    err = stat (path, &st);
    if (err) {
	fprintf (stderr, "Error: Cannot create database at %s: %s.\n",
		 path, strerror (errno));
	goto DONE;
    }

    if (! S_ISDIR (st.st_mode)) {
	fprintf (stderr, "Error: Cannot create database at %s: Not a directory.\n",
		 path);
	goto DONE;
    }

    notmuch_path = g_strdup_printf ("%s/%s", path, ".notmuch");

    err = mkdir (notmuch_path, 0755);

    if (err) {
	fprintf (stderr, "Error: Cannot create directory %s: %s.\n",
		 notmuch_path, strerror (errno));
	goto DONE;
    }

    notmuch = notmuch_database_open (path);

  DONE:
    if (notmuch_path)
	free (notmuch_path);
    if (local_path)
	free (local_path);

    return notmuch;
}

notmuch_database_t *
notmuch_database_open (const char *path)
{
    notmuch_database_t *notmuch = NULL;
    char *notmuch_path = NULL, *xapian_path = NULL;
    struct stat st;
    int err;
    char *local_path = NULL;

    if (path == NULL)
	path = local_path = notmuch_database_default_path ();

    notmuch_path = g_strdup_printf ("%s/%s", path, ".notmuch");

    err = stat (notmuch_path, &st);
    if (err) {
	fprintf (stderr, "Error opening database at %s: %s\n",
		 notmuch_path, strerror (errno));
	goto DONE;
    }

    xapian_path = g_strdup_printf ("%s/%s", notmuch_path, "xapian");

    notmuch = talloc (NULL, notmuch_database_t);
    notmuch->path = talloc_strdup (notmuch, path);

    try {
	notmuch->xapian_db = new Xapian::WritableDatabase (xapian_path,
							   Xapian::DB_CREATE_OR_OPEN);
	notmuch->query_parser = new Xapian::QueryParser;
	notmuch->query_parser->set_default_op (Xapian::Query::OP_AND);
	notmuch->query_parser->set_database (*notmuch->xapian_db);
    } catch (const Xapian::Error &error) {
	fprintf (stderr, "A Xapian exception occurred: %s\n",
		 error.get_msg().c_str());
    }
    
  DONE:
    if (local_path)
	free (local_path);
    if (notmuch_path)
	free (notmuch_path);
    if (xapian_path)
	free (xapian_path);

    return notmuch;
}

void
notmuch_database_close (notmuch_database_t *notmuch)
{
    delete notmuch->query_parser;
    delete notmuch->xapian_db;
    talloc_free (notmuch);
}

const char *
notmuch_database_get_path (notmuch_database_t *notmuch)
{
    return notmuch->path;
}

notmuch_status_t
notmuch_database_add_message (notmuch_database_t *notmuch,
			      const char *filename)
{
    notmuch_message_file_t *message_file;
    notmuch_message_t *message;
    notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS;

    GPtrArray *parents, *thread_ids;

    const char *refs, *in_reply_to, *date, *header;
    const char *from, *to, *subject, *old_filename;
    char *message_id;

    unsigned int i;

    message_file = notmuch_message_file_open (filename);
    if (message_file == NULL) {
	ret = NOTMUCH_STATUS_FILE_ERROR;
	goto DONE;
    }

    notmuch_message_file_restrict_headers (message_file,
					   "date",
					   "from",
					   "in-reply-to",
					   "message-id",
					   "references",
					   "subject",
					   "to",
					   (char *) NULL);

    try {
	/* The first order of business is to find/create a message ID. */

	header = notmuch_message_file_get_header (message_file, "message-id");
	if (header) {
	    message_id = parse_message_id (header, NULL);
	    /* So the header value isn't RFC-compliant, but it's
	     * better than no message-id at all. */
	    if (message_id == NULL)
		message_id = xstrdup (header);
	} else {
	    /* No message-id at all, let's generate one by taking a
	     * hash over the file's contents. */
	    char *sha1 = notmuch_sha1_of_file (filename);

	    /* If that failed too, something is really wrong. Give up. */
	    if (sha1 == NULL) {
		ret = NOTMUCH_STATUS_FILE_ERROR;
		goto DONE;
	    }

	    message_id = g_strdup_printf ("notmuch-sha1-%s", sha1);
	    free (sha1);
	}

	/* Now that we have a message ID, we get a message object,
	 * (which may or may not reference an existing document in the
	 * database). */

	/* Use NULL for owner since we want to free this locally. */

	/* XXX: This call can fail by either out-of-memory or an
	 * "impossible" Xapian exception. We should rewrite it to
	 * allow us to propagate the error status. */
	message = _notmuch_message_create_for_message_id (NULL, notmuch,
							  message_id);
	if (message == NULL) {
	    fprintf (stderr, "Internal error. This shouldn't happen.\n\n");
	    fprintf (stderr, "I mean, it's possible you ran out of memory, but then this code path is still an internal error since it should have detected that and propagated the status value up the stack.\n");
	    exit (1);
	}

	/* Has a message previously been added with the same ID? */
	old_filename = notmuch_message_get_filename (message);
	if (old_filename && strlen (old_filename)) {
	    /* XXX: This is too noisy to actually print, and what do we
	     * really expect the user to do? Go manually delete a
	     * redundant message or merge two similar messages?
	     * Instead we should handle this transparently.
	     *
	     * What we likely want to move to is adding both filenames
	     * to the database so that subsequent indexing will pick up
	     * terms from both files.
	     */
#if 0
	    fprintf (stderr,
		     "Note: Attempting to add a message with a duplicate message ID:\n"
		     "Old: %s\n"   "New: %s\n",
		     old_filename, filename);
	    fprintf (stderr, "The old filename will be used, but any new terms\n"
		     "from the new message will added to the database.\n");
#endif
	} else {
	    _notmuch_message_set_filename (message, filename);
	    _notmuch_message_add_term (message, "type", "mail");
	}

	/* Next, find the thread(s) to which this message belongs. */
	parents = g_ptr_array_new ();

	refs = notmuch_message_file_get_header (message_file, "references");
	parse_references (parents, refs);

	in_reply_to = notmuch_message_file_get_header (message_file, "in-reply-to");
	parse_references (parents, in_reply_to);

	for (i = 0; i < parents->len; i++)
	    _notmuch_message_add_term (message, "ref",
				       (char *) g_ptr_array_index (parents, i));

	thread_ids = find_thread_ids (notmuch, parents, message_id);

	free (message_id);

	for (i = 0; i < parents->len; i++)
	    g_free (g_ptr_array_index (parents, i));
	g_ptr_array_free (parents, TRUE);

	if (thread_ids->len) {
	    unsigned int i;
	    GString *thread_id;
	    char *id;

	    for (i = 0; i < thread_ids->len; i++) {
		id = (char *) thread_ids->pdata[i];
		_notmuch_message_add_thread_id (message, id);
		if (i == 0)
		    thread_id = g_string_new (id);
		else
		    g_string_append_printf (thread_id, ",%s", id);

		free (id);
	    }
	    g_string_free (thread_id, TRUE);
	} else {
	    _notmuch_message_ensure_thread_id (message);
	}

	g_ptr_array_free (thread_ids, TRUE);

	date = notmuch_message_file_get_header (message_file, "date");
	_notmuch_message_set_date (message, date);

	from = notmuch_message_file_get_header (message_file, "from");
	subject = notmuch_message_file_get_header (message_file, "subject");
	to = notmuch_message_file_get_header (message_file, "to");

	if (from == NULL &&
	    subject == NULL &&
	    to == NULL)
	{
	    ret = NOTMUCH_STATUS_FILE_NOT_EMAIL;
	    goto DONE;
	} else {
	    _notmuch_message_sync (message);
	}
    } catch (const Xapian::Error &error) {
	fprintf (stderr, "A Xapian exception occurred: %s.\n",
		 error.get_msg().c_str());
	ret = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
	goto DONE;
    }

  DONE:
    if (message)
	notmuch_message_destroy (message);
    if (message_file)
	notmuch_message_file_close (message_file);

    return ret;
}