/* 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 *filename;
    Xapian::Document doc;
};

typedef struct _notmuch_terms {
    char prefix_char;
    Xapian::TermIterator iterator;
    Xapian::TermIterator iterator_end;
} notmuch_terms_t;

struct _notmuch_tags {
    notmuch_terms_t terms;
};

struct _notmuch_thread_ids {
    notmuch_terms_t terms;
};

/* "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 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. 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;
    message->message_id = NULL; /* lazily created */
    message->filename = NULL; /* lazily created */

    /* 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);

    if (private_status >= (notmuch_private_status_t) NOTMUCH_STATUS_LAST_STATUS)
    {
	INTERNAL_ERROR ("Failed to find document immediately after adding it.\n");
    }

    *status = (notmuch_status_t) private_status;

    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);
    return message->message_id;
}

/* Set the filename for 'message' to 'filename'.
 *
 * XXX: We should still figure out what we want to do for multiple
 * files with identical message IDs. We will probably want to store a
 * list of filenames here, (so that this will be "add_filename"
 * instead of "set_filename"). Which would make this very similar to
 * add_thread_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;
}

/* We end up having to call the destructors 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_terms_destructor (notmuch_terms_t *terms)
{
    terms->iterator.~TermIterator ();
    terms->iterator_end.~TermIterator ();

    return 0;
}

notmuch_terms_t *
_notmuch_terms_create (void *ctx,
		       Xapian::Document doc,
		       const char *prefix_name)
{
    notmuch_terms_t *terms;
    const char *prefix = _find_prefix (prefix_name);

    /* Currently, notmuch_terms_t is written with the assumption that
     * any prefix its derivatives use will be only a single
     * character. */
    assert (strlen (prefix) == 1);

    terms = talloc (ctx, notmuch_terms_t);
    if (unlikely (terms == NULL))
	return NULL;

    terms->prefix_char = *prefix;
    new (&terms->iterator) Xapian::TermIterator;
    new (&terms->iterator_end) Xapian::TermIterator;

    talloc_set_destructor (terms, _notmuch_terms_destructor);

    terms->iterator = doc.termlist_begin ();
    terms->iterator.skip_to (prefix);
    terms->iterator_end = doc.termlist_end ();

    return terms;
}

/* The assertion is to ensure that 'type' is a derivative of
 * notmuch_terms_t in that it contains a notmuch_terms_t as its first
 * member. We do this by name of 'terms' as opposed to type, because
 * that's as clever as I've been so far. */
#define _notmuch_terms_create_type(ctx, doc, prefix_name, type) \
    (COMPILE_TIME_ASSERT(offsetof(type, terms) == 0),		\
     (type *) _notmuch_terms_create (ctx, doc, prefix_name))

notmuch_tags_t *
notmuch_message_get_tags (notmuch_message_t *message)
{
    return _notmuch_terms_create_type (message, message->doc, "tag",
				       notmuch_tags_t);
}

notmuch_thread_ids_t *
notmuch_message_get_thread_ids (notmuch_message_t *message)
{
    return _notmuch_terms_create_type (message, message->doc, "thread",
				       notmuch_thread_ids_t);
}

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));
}

void
_notmuch_message_add_thread_id (notmuch_message_t *message,
				const char *thread_id)
{
    _notmuch_message_add_term (message, "thread", thread_id);
}

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);
}

notmuch_bool_t
_notmuch_terms_has_more (notmuch_terms_t *terms)
{
    std::string s;

    if (terms->iterator == terms->iterator_end)
	return FALSE;

    s = *terms->iterator;
    if (! s.empty () && s[0] == terms->prefix_char)
	return TRUE;
    else
	return FALSE;
}

const char *
_notmuch_terms_get (notmuch_terms_t *terms)
{
    return talloc_strdup (terms, (*terms->iterator).c_str () + 1);
}

void
_notmuch_terms_advance (notmuch_terms_t *terms)
{
    terms->iterator++;
}

void
_notmuch_terms_destroy (notmuch_terms_t *terms)
{
    talloc_free (terms);
}

notmuch_bool_t
notmuch_tags_has_more (notmuch_tags_t *tags)
{
    return _notmuch_terms_has_more (&tags->terms);
}

const char *
notmuch_tags_get (notmuch_tags_t *tags)
{
    return _notmuch_terms_get (&tags->terms);
}

void
notmuch_tags_advance (notmuch_tags_t *tags)
{
    return _notmuch_terms_advance (&tags->terms);
}

void
notmuch_tags_destroy (notmuch_tags_t *tags)
{
    return _notmuch_terms_destroy (&tags->terms);
}

notmuch_bool_t
notmuch_thread_ids_has_more (notmuch_thread_ids_t *thread_ids)
{
    return _notmuch_terms_has_more (&thread_ids->terms);
}

const char *
notmuch_thread_ids_get (notmuch_thread_ids_t *thread_ids)
{
    return _notmuch_terms_get (&thread_ids->terms);
}

void
notmuch_thread_ids_advance (notmuch_thread_ids_t *thread_ids)
{
    return _notmuch_terms_advance (&thread_ids->terms);
}

void
notmuch_thread_ids_destroy (notmuch_thread_ids_t *thread_ids)
{
    return _notmuch_terms_destroy (&thread_ids->terms);
}