+ const char *filename,
+ notmuch_message_t **message);
+
+/* Find a message with the given messsage_id.
+ *
+ * If the database contains a message with the given message_id, then
+ * a new notmuch_message_t object is returned. The caller should call
+ * notmuch_message_destroy when done with the message.
+ *
+ * If no message is found with the given message_id or if an
+ * out-of-memory situation occurs, this function returns NULL.
+ */
+notmuch_message_t *
+notmuch_database_find_message (notmuch_database_t *database,
+ const char *message_id);
+
+/* Create a new query for 'database'.
+ *
+ * Here, 'database' should be an open database, (see
+ * notmuch_database_open and notmuch_database_create).
+ *
+ * For the query string, we'll document the syntax here more
+ * completely in the future, but it's likely to be a specialized
+ * version of the general Xapian query syntax:
+ *
+ * http://xapian.org/docs/queryparser.html
+ *
+ * As a special case, passing a length-zero string, (that is ""), will
+ * result in a query that returns all messages in the database.
+ *
+ * See notmuch_query_set_sort for controlling the order of results and
+ * notmuch_query_search to actually execute the query.
+ *
+ * User should call notmuch_query_destroy when finished with this
+ * query.
+ *
+ * Will return NULL if insufficient memory is available.
+ */
+notmuch_query_t *
+notmuch_query_create (notmuch_database_t *database,
+ const char *query_string);
+
+/* Sort values for notmuch_query_set_sort */
+typedef enum {
+ NOTMUCH_SORT_DATE_OLDEST_FIRST,
+ NOTMUCH_SORT_DATE_NEWEST_FIRST,
+ NOTMUCH_SORT_MESSAGE_ID
+} notmuch_sort_t;
+
+/* Specify the sorting desired for this query. */
+void
+notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort);
+
+/* Execute a query for threads, returning a notmuch_threads_t object
+ * which can be used to iterate over the results. The returned threads
+ * object is owned by the query and as such, will only be valid until
+ * notmuch_query_destroy.
+ *
+ * Typical usage might be:
+ *
+ * notmuch_query_t *query;
+ * notmuch_threads_t *threads;
+ * notmuch_thread_t *thread;
+ *
+ * query = notmuch_query_create (database, query_string);
+ *
+ * for (threads = notmuch_query_search_threads (query);
+ * notmuch_threads_has_more (threads);
+ * notmuch_threads_advance (threads))
+ * {
+ * thread = notmuch_threads_get (threads);
+ * ....
+ * notmuch_thread_destroy (thread);
+ * }
+ *
+ * notmuch_query_destroy (query);
+ *
+ * Note: If you are finished with a thread before its containing
+ * query, you can call notmuch_thread_destroy to clean up some memory
+ * sooner (as in the above example). Otherwise, if your thread objects
+ * are long-lived, then you don't need to call notmuch_thread_destroy
+ * and all the memory will still be reclaimed when the query is
+ * destroyed.
+ *
+ * Note that there's no explicit destructor needed for the
+ * notmuch_threads_t object. (For consistency, we do provide a
+ * notmuch_threads_destroy function, but there's no good reason
+ * to call it if the query is about to be destroyed).
+ */
+notmuch_threads_t *
+notmuch_query_search_threads (notmuch_query_t *query);
+
+/* Execute a query for messages, returning a notmuch_messages_t object
+ * which can be used to iterate over the results. The returned
+ * messages object is owned by the query and as such, will only be
+ * valid until notmuch_query_destroy.
+ *
+ * Typical usage might be:
+ *
+ * notmuch_query_t *query;
+ * notmuch_messages_t *messages;
+ * notmuch_message_t *message;
+ *
+ * query = notmuch_query_create (database, query_string);
+ *
+ * for (messages = notmuch_query_search_messages (query);
+ * notmuch_messages_has_more (messages);
+ * notmuch_messages_advance (messages))
+ * {
+ * message = notmuch_messages_get (messages);
+ * ....
+ * notmuch_message_destroy (message);
+ * }
+ *
+ * notmuch_query_destroy (query);
+ *
+ * Note: If you are finished with a message before its containing
+ * query, you can call notmuch_message_destroy to clean up some memory
+ * sooner (as in the above example). Otherwise, if your message
+ * objects are long-lived, then you don't need to call
+ * notmuch_message_destroy and all the memory will still be reclaimed
+ * when the query is destroyed.
+ *
+ * Note that there's no explicit destructor needed for the
+ * notmuch_messages_t object. (For consistency, we do provide a
+ * notmuch_messages_destroy function, but there's no good
+ * reason to call it if the query is about to be destroyed).
+ */
+notmuch_messages_t *
+notmuch_query_search_messages (notmuch_query_t *query);
+
+/* Destroy a notmuch_query_t along with any associated resources.
+ *
+ * This will in turn destroy any notmuch_threads_t and
+ * notmuch_messages_t objects generated by this query, (and in
+ * turn any notmuch_thrad_t and notmuch_message_t objects generated
+ * from those results, etc.), if such objects haven't already been
+ * destroyed.
+ */
+void
+notmuch_query_destroy (notmuch_query_t *query);
+
+/* Does the given notmuch_threads_t object contain any more
+ * results.
+ *
+ * When this function returns TRUE, notmuch_threads_get will
+ * return a valid object. Whereas when this function returns FALSE,
+ * notmuch_threads_get will return NULL.
+ *
+ * See the documentation of notmuch_query_search_threads for example
+ * code showing how to iterate over a notmuch_threads_t object.
+ */
+notmuch_bool_t
+notmuch_threads_has_more (notmuch_threads_t *threads);
+
+/* Get the current thread from 'threads' as a notmuch_thread_t.
+ *
+ * Note: The returned thread belongs to 'threads' and has a lifetime
+ * identical to it (and the query to which it belongs).
+ *
+ * See the documentation of notmuch_query_search_threads for example
+ * code showing how to iterate over a notmuch_threads_t object.
+ *
+ * If an out-of-memory situation occurs, this function will return
+ * NULL.
+ */
+notmuch_thread_t *
+notmuch_threads_get (notmuch_threads_t *threads);
+
+/* Advance the 'threads' iterator to the next thread.
+ *
+ * See the documentation of notmuch_query_search_threads for example
+ * code showing how to iterate over a notmuch_threads_t object.
+ */
+void
+notmuch_threads_advance (notmuch_threads_t *threads);
+
+/* Destroy a notmuch_threads_t object.
+ *
+ * It's not strictly necessary to call this function. All memory from
+ * the notmuch_threads_t object will be reclaimed when the
+ * containg query object is destroyed.
+ */
+void
+notmuch_threads_destroy (notmuch_threads_t *threads);
+
+/* Get the thread ID of 'thread'.
+ *
+ * The returned string belongs to 'thread' and as such, should not be
+ * modified by the caller and will only be valid for as long as the
+ * thread is valid, (which is until notmuch_thread_destroy or until
+ * the query from which it derived is destroyed).
+ */
+const char *
+notmuch_thread_get_thread_id (notmuch_thread_t *thread);
+
+/* Get the subject of 'thread'
+ *
+ * The subject is taken from the first message (according to the query
+ * order---see notmuch_query_set_sort) in the query results that
+ * belongs to this thread.
+ *
+ * The returned string belongs to 'thread' and as such, should not be
+ * modified by the caller and will only be valid for as long as the
+ * thread is valid, (which is until notmuch_thread_destroy or until
+ * the query from which it derived is destroyed).
+ */
+const char *
+notmuch_thread_get_subject (notmuch_thread_t *thread);
+
+/* Get the date of the oldest message in 'thread' as a time_t value.
+ */
+time_t
+notmuch_thread_get_oldest_date (notmuch_thread_t *thread);
+
+/* Get the date of the oldest message in 'thread' as a time_t value.
+ */
+time_t
+notmuch_thread_get_newest_date (notmuch_thread_t *thread);
+
+/* Get the tags for 'thread', returning a notmuch_tags_t object which
+ * can be used to iterate over all tags.
+ *
+ * Note: In the Notmuch database, tags are stored on individual
+ * messages, not on threads. So the tags returned here will be all
+ * tags of the messages which matched the search and which belong to
+ * this thread.
+ *
+ * The tags object is owned by the thread and as such, will only be
+ * valid for as long as the thread is valid, (for example, until
+ * notmuch_thread_destroy or until the query from which it derived is
+ * destroyed).
+ *
+ * Typical usage might be:
+ *
+ * notmuch_thread_t *thread;
+ * notmuch_tags_t *tags;
+ * const char *tag;
+ *
+ * thread = notmuch_threads_get (threads);
+ *
+ * for (tags = notmuch_thread_get_tags (thread);
+ * notmuch_tags_has_more (tags);
+ * notmuch_result_advance (tags))
+ * {
+ * tag = notmuch_tags_get (tags);
+ * ....
+ * }
+ *
+ * notmuch_thread_destroy (thread);
+ *
+ * Note that there's no explicit destructor needed for the
+ * notmuch_tags_t object. (For consistency, we do provide a
+ * notmuch_tags_destroy function, but there's no good reason to call
+ * it if the message is about to be destroyed).
+ */
+notmuch_tags_t *
+notmuch_thread_get_tags (notmuch_thread_t *thread);
+
+/* Destroy a notmuch_thread_t object. */
+void
+notmuch_thread_destroy (notmuch_thread_t *thread);
+
+/* Does the given notmuch_messages_t object contain any more
+ * messages.
+ *
+ * When this function returns TRUE, notmuch_messages_get will return a
+ * valid object. Whereas when this function returns FALSE,
+ * notmuch_messages_get will return NULL.
+ *
+ * See the documentation of notmuch_query_search_messages for example
+ * code showing how to iterate over a notmuch_messages_t object.
+ */
+notmuch_bool_t
+notmuch_messages_has_more (notmuch_messages_t *messages);
+
+/* Get the current message from 'messages' as a notmuch_message_t.
+ *
+ * Note: The returned message belongs to 'messages' and has a lifetime
+ * identical to it (and the query to which it belongs).
+ *
+ * See the documentation of notmuch_query_search_messages for example
+ * code showing how to iterate over a notmuch_messages_t object.
+ *
+ * If an out-of-memory situation occurs, this function will return
+ * NULL.
+ */
+notmuch_message_t *
+notmuch_messages_get (notmuch_messages_t *messages);
+
+/* Advance the 'messages' iterator to the next result.
+ *
+ * See the documentation of notmuch_query_search_messages for example
+ * code showing how to iterate over a notmuch_messages_t object.
+ */
+void
+notmuch_messages_advance (notmuch_messages_t *messages);
+
+/* Destroy a notmuch_messages_t object.
+ *
+ * It's not strictly necessary to call this function. All memory from
+ * the notmuch_messages_t object will be reclaimed when the containg
+ * query object is destroyed.
+ */
+void
+notmuch_messages_destroy (notmuch_messages_t *messages);
+
+/* Get the message ID of 'message'.
+ *
+ * The returned string belongs to 'message' and as such, should not be
+ * modified by the caller and will only be valid for as long as the
+ * message is valid, (which is until the query from which it derived
+ * is destroyed).
+ *
+ * This function will not return NULL since Notmuch ensures that every
+ * message has a unique message ID, (Notmuch will generate an ID for a
+ * message if the original file does not contain one).
+ */
+const char *
+notmuch_message_get_message_id (notmuch_message_t *message);
+
+/* Get the thread ID of 'message'.
+ *
+ * The returned string belongs to 'message' and as such, should not be
+ * modified by the caller and will only be valid for as long as the
+ * message is valid, (for example, until the user calls
+ * notmuch_message_destroy on 'message' or until a query from which it
+ * derived is destroyed).
+ *
+ * This function will not return NULL since Notmuch ensures that every
+ * message belongs to a single thread.
+ */
+const char *
+notmuch_message_get_thread_id (notmuch_message_t *message);
+
+/* Get the filename for the email corresponding to 'message'.
+ *
+ * The returned filename is an absolute filename, (the initial
+ * component will match notmuch_database_get_path() ).
+ *
+ * The returned string belongs to the message so should not be
+ * modified or freed by the caller (nor should it be referenced after
+ * the message is destroyed). */
+const char *
+notmuch_message_get_filename (notmuch_message_t *message);
+
+/* Get the date of 'message' as a time_t value.
+ *
+ * For the original textual representation of the Date header from the
+ * message call notmuch_message_get_header() with a header value of
+ * "date". */
+time_t
+notmuch_message_get_date (notmuch_message_t *message);
+
+/* Get the size in bytes of the full header section of 'message'.
+ *
+ * This is useful in conjunction with notmuch_message_get_filename
+ * for separately parsing the message header and content.
+ *
+ * Returns 0 in the case of any error.
+ */
+size_t
+notmuch_message_get_header_size (notmuch_message_t *message);
+
+/* Get the value of the specified header from 'message'.
+ *
+ * The value will be read from the actual message file, not from the
+ * notmuch database. The header name is case insensitive.
+ *
+ * The returned string belongs to the message so should not be
+ * modified or freed by the caller (nor should it be referenced after
+ * the message is destroyed).
+ *
+ * Returns NULL if the message does not contain a header line matching
+ * 'header' of if any error occurs.
+ */
+const char *
+notmuch_message_get_header (notmuch_message_t *message, const char *header);
+
+/* Get the entire set of headers from an email message as a string.
+ *
+ * The value will be read from the actual message file, not from the
+ * notmuch database.
+ *
+ * The returned value is owned by the notmuch message and is valid
+ * only until the message is closed. The caller should copy it if
+ * needing to modify the value or to hold onto it for longer.
+ *
+ * Returns NULL in the case of any error.
+ */
+const char *
+notmuch_message_get_all_headers (notmuch_message_t *message);
+
+/* Get the tags for 'message', returning a notmuch_tags_t object which
+ * can be used to iterate over all tags.
+ *
+ * The tags object is owned by the message and as such, will only be
+ * valid for as long as the message is valid, (which is until the
+ * query from which it derived is destroyed).
+ *
+ * Typical usage might be:
+ *
+ * notmuch_message_t *message;
+ * notmuch_tags_t *tags;
+ * const char *tag;
+ *
+ * message = notmuch_database_find_message (database, message_id);
+ *
+ * for (tags = notmuch_message_get_tags (message);
+ * notmuch_tags_has_more (tags);
+ * notmuch_result_advance (tags))
+ * {
+ * tag = notmuch_tags_get (tags);
+ * ....
+ * }
+ *
+ * notmuch_message_destroy (message);
+ *
+ * Note that there's no explicit destructor needed for the
+ * notmuch_tags_t object. (For consistency, we do provide a
+ * notmuch_tags_destroy function, but there's no good reason to call
+ * it if the message is about to be destroyed).
+ */
+notmuch_tags_t *
+notmuch_message_get_tags (notmuch_message_t *message);
+
+/* The longest possible tag value. */
+#define NOTMUCH_TAG_MAX 200
+
+/* Add a tag to the given message.
+ *
+ * Return value:
+ *
+ * NOTMUCH_STATUS_SUCCESS: Tag successfully added to message
+ *
+ * NOTMUCH_STATUS_NULL_POINTER: The 'tag' argument is NULL
+ *
+ * NOTMUCH_STATUS_TAG_TOO_LONG: The length of 'tag' is too long
+ * (exceeds NOTMUCH_TAG_MAX)
+ */
+notmuch_status_t
+notmuch_message_add_tag (notmuch_message_t *message, const char *tag);
+
+/* Remove a tag from the given message.
+ *
+ * Return value:
+ *
+ * NOTMUCH_STATUS_SUCCESS: Tag successfully removed from message
+ *
+ * NOTMUCH_STATUS_NULL_POINTER: The 'tag' argument is NULL
+ *
+ * NOTMUCH_STATUS_TAG_TOO_LONG: The length of 'tag' is too long
+ * (exceeds NOTMUCH_TAG_MAX)
+ */
+notmuch_status_t
+notmuch_message_remove_tag (notmuch_message_t *message, const char *tag);
+
+/* Remove all tags from the given message.
+ *
+ * See notmuch_message_freeze for an example showing how to safely
+ * replace tag values.
+ */
+void
+notmuch_message_remove_all_tags (notmuch_message_t *message);
+
+/* Freeze the current state of 'message' within the database.
+ *
+ * This means that changes to the message state, (via
+ * notmuch_message_add_tag, notmuch_message_remove_tag, and
+ * notmuch_message_remove_all_tags), will not be committed to the
+ * database until the message is thawed with notmuch_message_thaw.
+ *
+ * Multiple calls to freeze/thaw are valid and these calls with
+ * "stack". That is there must be as many calls to thaw as to freeze
+ * before a message is actually thawed.
+ *
+ * The ability to do freeze/thaw allows for safe transactions to
+ * change tag values. For example, explicitly setting a message to
+ * have a given set of tags might look like this:
+ *
+ * notmuch_message_freeze (message);
+ *
+ * notmuch_message_remove_all_tags (message);
+ *
+ * for (i = 0; i < NUM_TAGS; i++)
+ * notmuch_message_add_tag (message, tags[i]);
+ *
+ * notmuch_message_thaw (message);
+ *
+ * With freeze/thaw used like this, the message in the database is
+ * guaranteed to have either the full set of original tag value, or
+ * the full set of new tag values, but nothing in between.
+ *
+ * Imagine the example above without freeze/thaw and the operation
+ * somehow getting interrupted. This could result in the message being
+ * left with no tags if the interruption happened after
+ * notmuch_message_remove_all_tags but before notmuch_message_add_tag.
+ */
+void
+notmuch_message_freeze (notmuch_message_t *message);
+
+/* Thaw the current 'message', synchronizing any changes that may have
+ * occurred while 'message' was frozen into the notmuch database.
+ *
+ * See notmuch_message_freeze for an example of how to use this
+ * function to safely provide tag changes.
+ *
+ * Multiple calls to freeze/thaw are valid and these calls with
+ * "stack". That is there must be as many calls to thaw as to freeze
+ * before a message is actually thawed.
+ *
+ * Return value:
+ *
+ * NOTMUCH_STATUS_SUCCESS: Message successfully thawed, (or at least
+ * its frozen count has successfully been reduced by 1).
+ *
+ * NOTMUCH_STATUS_UNBALANCE_FREEZE_THAW: An attempt was made to thaw
+ * an unfrozen message. That is, there have been an unbalanced
+ * number of calls to notmuch_message_freeze and
+ * notmuch_message_thaw.
+ */
+notmuch_status_t
+notmuch_message_thaw (notmuch_message_t *message);
+
+/* Destroy a notmuch_message_t object.
+ *
+ * It can be useful to call this function in the case of a single
+ * query object with many messages in the result, (such as iterating
+ * over the entire database). Otherwise, it's fine to never call this
+ * function and there will still be no memory leaks. (The memory from
+ * the messages get reclaimed when the containing query is destroyed.)
+ */
+void
+notmuch_message_destroy (notmuch_message_t *message);
+
+/* Does the given notmuch_tags_t object contain any more tags.
+ *
+ * When this function returns TRUE, notmuch_tags_get will return a
+ * valid string. Whereas when this function returns FALSE,
+ * notmuch_tags_get will return NULL.
+ *
+ * See the documentation of notmuch_message_get_tags for example code
+ * showing how to iterate over a notmuch_tags_t object.
+ */
+notmuch_bool_t
+notmuch_tags_has_more (notmuch_tags_t *tags);
+
+/* Get the current tag from 'tags' as a string.
+ *
+ * Note: The returned string belongs to 'tags' and has a lifetime
+ * identical to it (and the query to which it utlimately belongs).
+ *
+ * See the documentation of notmuch_message_get_tags for example code
+ * showing how to iterate over a notmuch_tags_t object.
+ */
+const char *
+notmuch_tags_get (notmuch_tags_t *tags);
+
+/* Advance the 'tags' iterator to the next tag.
+ *
+ * See the documentation of notmuch_message_get_tags for example code
+ * showing how to iterate over a notmuch_tags_t object.
+ */
+void
+notmuch_tags_advance (notmuch_tags_t *tags);
+
+/* Destroy a notmuch_tags_t object.
+ *
+ * It's not strictly necessary to call this function. All memory from
+ * the notmuch_tags_t object will be reclaimed when the containg
+ * message or query objects are destroyed.
+ */
+void
+notmuch_tags_destroy (notmuch_tags_t *tags);