/* message.cc - Results of message-based searches from a notmuch database
 *
 * 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 "notmuch-private.h"
#include "database-private.h"

#include <xapian.h>

struct _notmuch_message {
    notmuch_database_t *notmuch;
    Xapian::docid doc_id;
    char *message_id;
    char *thread_id;
    char *filename;
    notmuch_message_file_t *message_file;
    Xapian::Document doc;
};


/* "128 bits of thread-id ought to be enough for anybody" */
#define NOTMUCH_THREAD_ID_BITS	 128
#define NOTMUCH_THREAD_ID_DIGITS (NOTMUCH_THREAD_ID_BITS / 4)
typedef struct _thread_id {
    char str[NOTMUCH_THREAD_ID_DIGITS + 1];
} thread_id_t;

/* We end up having to call the destructor explicitly because we had
 * to use "placement new" in order to initialize C++ objects within a
 * block that we allocated with talloc. So C++ is making talloc
 * slightly less simple to use, (we wouldn't need
 * talloc_set_destructor at all otherwise).
 */
static int
_notmuch_message_destructor (notmuch_message_t *message)
{
    message->doc.~Document ();

    return 0;
}

/* Create a new notmuch_message_t object for an existing document in
 * the database.
 *
 * Here, 'talloc owner' is an optional talloc context to which the new
 * message will belong. This allows for the caller to not bother
 * calling notmuch_message_destroy on the message, and no that all
 * memory will be reclaimed with 'talloc_owner' is free. The caller
 * still can call notmuch_message_destroy when finished with the
 * message if desired.
 *
 * The 'talloc_owner' argument can also be NULL, in which case the
 * caller *is* responsible for calling notmuch_message_destroy.
 *
 * If no document exists in the database with document ID of 'doc_id'
 * then this function returns NULL and optionally sets *status to
 * NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND.
 *
 * This function can also fail to due lack of available memory,
 * returning NULL and optionally setting *status to
 * NOTMUCH_PRIVATE_STATUS_OUT_OF_MEMORY.
 *
 * The caller can pass NULL for status if uninterested in
 * distinguishing these two cases.
 */
notmuch_message_t *
_notmuch_message_create (const void *talloc_owner,
			 notmuch_database_t *notmuch,
			 unsigned int doc_id,
			 notmuch_private_status_t *status)
{
    notmuch_message_t *message;

    if (status)
	*status = NOTMUCH_PRIVATE_STATUS_SUCCESS;

    message = talloc (talloc_owner, notmuch_message_t);
    if (unlikely (message == NULL)) {
	if (status)
	    *status = NOTMUCH_PRIVATE_STATUS_OUT_OF_MEMORY;
	return NULL;
    }

    message->notmuch = notmuch;
    message->doc_id = doc_id;

    /* Each of these will be lazily created as needed. */
    message->message_id = NULL;
    message->thread_id = NULL;
    message->filename = NULL;
    message->message_file = NULL;

    /* This is C++'s creepy "placement new", which is really just an
     * ugly way to call a constructor for a pre-allocated object. So
     * it's really not an error to not be checking for OUT_OF_MEMORY
     * here, since this "new" isn't actually allocating memory. This
     * is language-design comedy of the wrong kind. */

    new (&message->doc) Xapian::Document;

    talloc_set_destructor (message, _notmuch_message_destructor);

    try {
	message->doc = notmuch->xapian_db->get_document (doc_id);
    } catch (const Xapian::DocNotFoundError &error) {
	talloc_free (message);
	if (status)
	    *status = NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND;
	return NULL;
    }

    return message;
}

/* Create a new notmuch_message_t object for a specific message ID,
 * (which may or may not already exist in the databas).
 *
 * Here, 'talloc owner' is an optional talloc context to which the new
 * message will belong. This allows for the caller to not bother
 * calling notmuch_message_destroy on the message, and no that all
 * memory will be reclaimed with 'talloc_owner' is free. The caller
 * still can call notmuch_message_destroy when finished with the
 * message if desired.
 *
 * The 'talloc_owner' argument can also be NULL, in which case the
 * caller *is* responsible for calling notmuch_message_destroy.
 *
 * If there is already a document with message ID 'message_id' in the
 * database, then the returned message can be used to query/modify the
 * document. Otherwise, a new document will be inserted into the
 * database before this function returns.
 *
 * If an error occurs, this function will return NULL and *status
 * will be set as appropriate. (The status pointer argument must
 * not be NULL.)
 */
notmuch_message_t *
_notmuch_message_create_for_message_id (const void *talloc_owner,
					notmuch_database_t *notmuch,
					const char *message_id,
					notmuch_status_t *status)
{
    notmuch_private_status_t private_status;
    notmuch_message_t *message;
    Xapian::Document doc;
    unsigned int doc_id;
    char *term;

    *status = NOTMUCH_STATUS_SUCCESS;

    message = notmuch_database_find_message (notmuch, message_id);
    if (message)
	return talloc_steal (talloc_owner, message);

    term = talloc_asprintf (NULL, "%s%s",
			    _find_prefix ("id"), message_id);
    if (term == NULL) {
	*status = NOTMUCH_STATUS_OUT_OF_MEMORY;
	return NULL;
    }

    try {
	doc.add_term (term);
	talloc_free (term);

	doc.add_value (NOTMUCH_VALUE_MESSAGE_ID, message_id);

	doc_id = notmuch->xapian_db->add_document (doc);
    } catch (const Xapian::Error &error) {
	*status = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
	return NULL;
    }

    message = _notmuch_message_create (talloc_owner, notmuch,
				       doc_id, &private_status);

    *status = COERCE_STATUS (private_status,
			     "Failed to find dcocument after inserting it.");

    return message;
}

const char *
notmuch_message_get_message_id (notmuch_message_t *message)
{
    Xapian::TermIterator i;

    if (message->message_id)
	return message->message_id;

    i = message->doc.termlist_begin ();
    i.skip_to (_find_prefix ("id"));

    if (i == message->doc.termlist_end ())
	INTERNAL_ERROR ("Message with document ID of %d has no message ID.\n",
			message->doc_id);

    message->message_id = talloc_strdup (message, (*i).c_str () + 1);

#if DEBUG_DATABASE_SANITY
    i++;

    if (i != message->doc.termlist_end () &&
	strncmp ((*i).c_str (), _find_prefix ("id"),
		 strlen (_find_prefix ("id"))) == 0)
    {
	INTERNAL_ERROR ("Mail (doc_id: %d) has duplicate message IDs",
			message->doc_id);
    }
#endif

    return message->message_id;
}

const char *
_notmuch_message_get_subject (notmuch_message_t *message)
{
    if (! message->message_file) {
	notmuch_message_file_t *message_file;
	const char *filename;

	filename = notmuch_message_get_filename (message);
	if (unlikely (filename == NULL))
	    return NULL;

	message_file = _notmuch_message_file_open_ctx (message, filename);
	if (unlikely (message_file == NULL))
	    return NULL;

	message->message_file = message_file;
    }

    return notmuch_message_file_get_header (message->message_file,
					    "subject");
}

const char *
notmuch_message_get_thread_id (notmuch_message_t *message)
{
    Xapian::TermIterator i;

    if (message->thread_id)
	return message->thread_id;

    i = message->doc.termlist_begin ();
    i.skip_to (_find_prefix ("thread"));

    if (i == message->doc.termlist_end ())
	INTERNAL_ERROR ("Message with document ID of %d has no thread ID.\n",
			message->doc_id);

    message->thread_id = talloc_strdup (message, (*i).c_str () + 1);

#if DEBUG_DATABASE_SANITY
    i++;

    if (i != message->doc.termlist_end () &&
	strncmp ((*i).c_str (), _find_prefix ("thread"),
		 strlen (_find_prefix ("thread"))) == 0)
    {
	INTERNAL_ERROR ("Message with document ID of %d has duplicate thread IDs.\n",
			message->doc_id);
    }
#endif

    return message->thread_id;
}

/* Set the filename for 'message' to 'filename'.
 *
 * XXX: We should still figure out if we think it's important to store
 * multiple filenames for email messages with identical message IDs.
 *
 * This change will not be reflected in the database until the next
 * call to _notmuch_message_set_sync. */
void
_notmuch_message_set_filename (notmuch_message_t *message,
			       const char *filename)
{
    if (message->filename)
	talloc_free (message->filename);
    message->doc.set_data (filename);
}

const char *
notmuch_message_get_filename (notmuch_message_t *message)
{
    std::string filename_str;

    if (message->filename)
	return message->filename;

    filename_str = message->doc.get_data ();
    message->filename = talloc_strdup (message, filename_str.c_str ());

    return message->filename;
}

notmuch_tags_t *
notmuch_message_get_tags (notmuch_message_t *message)
{
    const char *prefix = _find_prefix ("tag");
    Xapian::TermIterator i, end;
    notmuch_tags_t *tags;
    std::string tag;

    /* Currently this iteration is written with the assumption that
     * "tag" has a single-character prefix. */
    assert (strlen (prefix) == 1);

    tags = _notmuch_tags_create (message);
    if (unlikely (tags == NULL))
	return NULL;

    i = message->doc.termlist_begin ();
    end = message->doc.termlist_end ();

    i.skip_to (prefix);

    while (1) {
	tag = *i;

	if (tag.empty () || tag[0] != *prefix)
	    break;

	_notmuch_tags_add_tag (tags, tag.c_str () + 1);

	i++;
    }

    _notmuch_tags_prepare_iterator (tags);

    return tags;
}

void
_notmuch_message_set_date (notmuch_message_t *message,
			   const char *date)
{
    time_t time_value;

    time_value = notmuch_parse_date (date, NULL);

    message->doc.add_value (NOTMUCH_VALUE_TIMESTAMP,
			    Xapian::sortable_serialise (time_value));
}

static void
thread_id_generate (thread_id_t *thread_id)
{
    static int seeded = 0;
    FILE *dev_random;
    uint32_t value;
    char *s;
    int i;

    if (! seeded) {
	dev_random = fopen ("/dev/random", "r");
	if (dev_random == NULL) {
	    srand (time (NULL));
	} else {
	    fread ((void *) &value, sizeof (value), 1, dev_random);
	    srand (value);
	    fclose (dev_random);
	}
	seeded = 1;
    }

    s = thread_id->str;
    for (i = 0; i < NOTMUCH_THREAD_ID_DIGITS; i += 8) {
	value = rand ();
	sprintf (s, "%08x", value);
	s += 8;
    }
}

void
_notmuch_message_ensure_thread_id (notmuch_message_t *message)
{
    /* If not part of any existing thread, generate a new thread_id. */
    thread_id_t thread_id;

    thread_id_generate (&thread_id);
    _notmuch_message_add_term (message, "thread", thread_id.str);
}

/* Synchronize changes made to message->doc out into the database. */
void
_notmuch_message_sync (notmuch_message_t *message)
{
    Xapian::WritableDatabase *db = message->notmuch->xapian_db;

    db->replace_document (message->doc_id, message->doc);
}

/* Add a name:value term to 'message', (the actual term will be
 * encoded by prefixing the value with a short prefix). See
 * NORMAL_PREFIX and BOOLEAN_PREFIX arrays for the mapping of term
 * names to prefix values.
 *
 * This change will not be reflected in the database until the next
 * call to _notmuch_message_set_sync. */
notmuch_private_status_t
_notmuch_message_add_term (notmuch_message_t *message,
			   const char *prefix_name,
			   const char *value)
{

    char *term;

    if (value == NULL)
	return NOTMUCH_PRIVATE_STATUS_NULL_POINTER;

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

    if (strlen (term) > NOTMUCH_TERM_MAX)
	return NOTMUCH_PRIVATE_STATUS_TERM_TOO_LONG;

    message->doc.add_term (term);

    talloc_free (term);

    return NOTMUCH_PRIVATE_STATUS_SUCCESS;
}

/* Remove a name:value term from 'message', (the actual term will be
 * encoded by prefixing the value with a short prefix). See
 * NORMAL_PREFIX and BOOLEAN_PREFIX arrays for the mapping of term
 * names to prefix values.
 *
 * This change will not be reflected in the database until the next
 * call to _notmuch_message_set_sync. */
notmuch_private_status_t
_notmuch_message_remove_term (notmuch_message_t *message,
			      const char *prefix_name,
			      const char *value)
{
    char *term;

    if (value == NULL)
	return NOTMUCH_PRIVATE_STATUS_NULL_POINTER;

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

    if (strlen (term) > NOTMUCH_TERM_MAX)
	return NOTMUCH_PRIVATE_STATUS_TERM_TOO_LONG;

    message->doc.remove_term (term);

    talloc_free (term);

    return NOTMUCH_PRIVATE_STATUS_SUCCESS;
}

notmuch_status_t
notmuch_message_add_tag (notmuch_message_t *message, const char *tag)
{
    notmuch_private_status_t status;

    if (tag == NULL)
	return NOTMUCH_STATUS_NULL_POINTER;

    if (strlen (tag) > NOTMUCH_TAG_MAX)
	return NOTMUCH_STATUS_TAG_TOO_LONG;

    status = _notmuch_message_add_term (message, "tag", tag);
    if (status) {
	INTERNAL_ERROR ("_notmuch_message_add_term return unexpected value: %d\n",
			status);
    }

    _notmuch_message_sync (message);

    return NOTMUCH_STATUS_SUCCESS;
}

notmuch_status_t
notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
{
    notmuch_private_status_t status;

    if (tag == NULL)
	return NOTMUCH_STATUS_NULL_POINTER;

    if (strlen (tag) > NOTMUCH_TAG_MAX)
	return NOTMUCH_STATUS_TAG_TOO_LONG;

    status = _notmuch_message_remove_term (message, "tag", tag);
    if (status) {
	INTERNAL_ERROR ("_notmuch_message_remove_term return unexpected value: %d\n",
			status);
    }

    _notmuch_message_sync (message);

    return NOTMUCH_STATUS_SUCCESS;
}

void
notmuch_message_destroy (notmuch_message_t *message)
{
    talloc_free (message);
}