/* 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_DUPLICATE_MESSAGE_ID:
	return "Message ID is identical to a message in database";
    case NOTMUCH_STATUS_NULL_POINTER:
	return "Erroneous NULL pointer";
    case NOTMUCH_STATUS_TAG_TOO_LONG:
	return "Tag value is too long (exceeds NOTMUCH_TAG_MAX)";
    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_doc_ids (notmuch_database_t *notmuch,
	      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 = notmuch->xapian_db->postlist_begin (term);

    *end = notmuch->xapian_db->postlist_end (term);

    free (term);
}

static notmuch_private_status_t
find_unique_doc_id (notmuch_database_t *notmuch,
		    const char *prefix_name,
		    const char *value,
		    unsigned int *doc_id)
{
    Xapian::PostingIterator i, end;

    find_doc_ids (notmuch, prefix_name, value, &i, &end);

    if (i == end) {
	*doc_id = 0;
	return NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND;
    } else {
	*doc_id = *i;
	return NOTMUCH_PRIVATE_STATUS_SUCCESS;
    }
}

static Xapian::Document
find_document_for_doc_id (notmuch_database_t *notmuch, unsigned doc_id)
{
    return notmuch->xapian_db->get_document (doc_id);
}

static notmuch_private_status_t
find_unique_document (notmuch_database_t *notmuch,
		      const char *prefix_name,
		      const char *value,
		      Xapian::Document *document,
		      unsigned int *doc_id)
{
    notmuch_private_status_t status;

    status = find_unique_doc_id (notmuch, prefix_name, value, doc_id);

    if (status) {
	*document = Xapian::Document ();
	return status;
    }

    *document = find_document_for_doc_id (notmuch, *doc_id);
    return NOTMUCH_PRIVATE_STATUS_SUCCESS;
}

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)
{
    notmuch_private_status_t status;
    unsigned int doc_id;

    status = find_unique_doc_id (notmuch, "msgid", message_id, &doc_id);

    if (status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND)
	return NULL;

    return _notmuch_message_create (notmuch, notmuch, doc_id);
}

/* 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::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_doc_ids (notmuch, "ref", message_id, &child, &children_end);
    for ( ; child != children_end; child++) {
	doc = find_document_for_doc_id (notmuch, *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_private_status_t
find_timestamp_document (notmuch_database_t *notmuch, const char *db_key,
			 Xapian::Document *doc, unsigned int *doc_id)
{
    return find_unique_document (notmuch, "timestamp", db_key, doc, doc_id);
}

/* We allow the user to use arbitrarily long keys for timestamps,
 * (they're for filesystem paths after all, which have no limit we
 * know about). But we have a term-length limit. So if we exceed that,
 * we'll use the SHA-1 of the user's key as the actual key for
 * constructing a database term.
 *
 * Caution: This function returns a newly allocated string which the
 * caller should free() when finished.
 */
static char *
timestamp_db_key (const char *key)
{
    if (strlen (key) + 1 > NOTMUCH_TERM_MAX) {
	return notmuch_sha1_of_string (key);
    } else {
	return strdup (key);
    }
}

notmuch_status_t
notmuch_database_set_timestamp (notmuch_database_t *notmuch,
				const char *key, time_t timestamp)
{
    Xapian::Document doc;
    unsigned int doc_id;
    notmuch_private_status_t status;
    notmuch_status_t ret = NOTMUCH_STATUS_SUCCESS;
    char *db_key = NULL;

    db_key = timestamp_db_key (key);

    try {
	status = find_timestamp_document (notmuch, db_key, &doc, &doc_id);

	doc.add_value (0, Xapian::sortable_serialise (timestamp));

	if (status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND) {
	    char *term = talloc_asprintf (NULL, "%s%s",
					  _find_prefix ("timestamp"), db_key);
	    doc.add_term (term);
	    talloc_free (term);

	    notmuch->xapian_db->add_document (doc);
	} else {
	    notmuch->xapian_db->replace_document (doc_id, doc);
	}

    } catch (Xapian::Error &error) {
	fprintf (stderr, "A Xapian exception occurred: %s.\n",
		 error.get_msg().c_str());
	ret = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
    }

    if (db_key)
	free (db_key);

    return ret;
}

time_t
notmuch_database_get_timestamp (notmuch_database_t *notmuch, const char *key)
{
    Xapian::Document doc;
    unsigned int doc_id;
    notmuch_private_status_t status;
    char *db_key = NULL;
    time_t ret = 0;

    db_key = timestamp_db_key (key);

    try {
	status = find_timestamp_document (notmuch, db_key, &doc, &doc_id);

	if (status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND)
	    goto DONE;

	ret =  Xapian::sortable_unserialise (doc.get_value (0));
    } catch (Xapian::Error &error) {
	goto DONE;
    }

  DONE:
    if (db_key)
	free (db_key);

    return ret;
}

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)) {
	    ret = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
	    goto DONE;
	} 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;
}