# Copyright (C) 2011-2012  Patrick Totzke <patricktotzke@gmail.com>
# This file is released under the GNU GPL, version 3 or a later revision.
# For further details see the COPYING file
from collections import deque
import errno
import logging
import multiprocessing
import os
import signal
import sys
import threading

from notmuch import Database, NotmuchError, XapianError
import notmuch

from . import DB_ENC
from .errors import DatabaseError
from .errors import DatabaseLockedError
from .errors import DatabaseROError
from .errors import NonexistantObjectError
from .message import Message
from .thread import Thread
from .utils import is_subdir_of
from ..settings.const import settings


class FillPipeProcess(multiprocessing.Process):

    def __init__(self, it, stdout, stderr, pipe, fun=(lambda x: x)):
        multiprocessing.Process.__init__(self)
        self.it = it
        self.pipe = pipe[1]
        self.fun = fun
        self.keep_going = True
        self.stdout = stdout
        self.stderr = stderr

    def handle_sigterm(self, signo, frame):
        # this is used to suppress any EINTR errors at interpreter
        # shutdown
        self.keep_going = False

        # raises SystemExit to shut down the interpreter from the
        # signal handler
        sys.exit()

    def run(self):
        # replace filedescriptors 1 and 2 (stdout and stderr) with
        # pipes to the parent process
        os.dup2(self.stdout, 1)
        os.dup2(self.stderr, 2)

        # register a signal handler for SIGTERM
        signal.signal(signal.SIGTERM, self.handle_sigterm)

        for a in self.it:
            try:
                self.pipe.send(self.fun(a))
            except IOError as e:
                # suppress spurious EINTR errors at interpreter
                # shutdown
                if e.errno != errno.EINTR or self.keep_going:
                    raise

        self.pipe.close()


class DBManager(object):

    """
    Keeps track of your index parameters, maintains a write-queue and
    lets you look up threads and messages directly to the persistent wrapper
    classes.
    """
    _sort_orders = {
        'oldest_first': notmuch.database.Query.SORT.OLDEST_FIRST,
        'newest_first': notmuch.database.Query.SORT.NEWEST_FIRST,
        'unsorted': notmuch.database.Query.SORT.UNSORTED,
        'message_id': notmuch.database.Query.SORT.MESSAGE_ID,
    }
    """constants representing sort orders"""

    def __init__(self, path=None, ro=False):
        """
        :param path: absolute path to the notmuch index
        :type path: str
        :param ro: open the index in read-only mode
        :type ro: bool
        """
        self.ro = ro
        self.path = path
        self.writequeue = deque([])
        self.processes = []

    def flush(self):
        """
        write out all queued write-commands in order, each one in a separate
        :meth:`atomic <notmuch.Database.begin_atomic>` transaction.

        If this fails the current action is rolled back, stays in the write
        queue and an exception is raised.
        You are responsible to retry flushing at a later time if you want to
        ensure that the cached changes are applied to the database.

        :exception: :exc:`~errors.DatabaseROError` if db is opened read-only
        :exception: :exc:`~errors.DatabaseLockedError` if db is locked
        """
        if self.ro:
            raise DatabaseROError()
        if self.writequeue:
            # read notmuch's config regarding imap flag synchronization
            sync = settings.get_notmuch_setting('maildir', 'synchronize_flags')

            # go through writequeue entries
            while self.writequeue:
                current_item = self.writequeue.popleft()
                logging.debug('write-out item: %s', str(current_item))

                # watch out for notmuch errors to re-insert current_item
                # to the queue on errors
                try:
                    # the first two coordinants are cnmdname and post-callback
                    cmd, afterwards = current_item[:2]
                    logging.debug('cmd created')

                    # acquire a writeable db handler
                    try:
                        mode = Database.MODE.READ_WRITE
                        db = Database(path=self.path, mode=mode)
                    except NotmuchError:
                        raise DatabaseLockedError()
                    logging.debug('got write lock')

                    # make this a transaction
                    db.begin_atomic()
                    logging.debug('got atomic')

                    if cmd == 'add':
                        logging.debug('add')
                        path, tags = current_item[2:]
                        msg, _ = db.add_message(path, sync_maildir_flags=sync)
                        logging.debug('added msg')
                        msg.freeze()
                        logging.debug('freeze')
                        for tag in tags:
                            msg.add_tag(tag, sync_maildir_flags=sync)
                        logging.debug('added tags ')
                        msg.thaw()
                        logging.debug('thaw')

                    elif cmd == 'remove':
                        path = current_item[2]
                        db.remove_message(path)

                    elif cmd == 'setconfig':
                        key = current_item[2]
                        value = current_item[3]
                        db.set_config(key, value)

                    else:  # tag/set/untag
                        querystring, tags = current_item[2:]
                        query = db.create_query(querystring)
                        for msg in query.search_messages():
                            msg.freeze()
                            if cmd == 'tag':
                                strategy = msg.add_tag
                            if cmd == 'set':
                                msg.remove_all_tags()
                                strategy = msg.add_tag
                            elif cmd == 'untag':
                                strategy = msg.remove_tag
                            for tag in tags:
                                strategy(tag, sync_maildir_flags=sync)
                            msg.thaw()

                    logging.debug('ended atomic')
                    # end transaction and reinsert queue item on error
                    if db.end_atomic() != notmuch.STATUS.SUCCESS:
                        raise DatabaseError('end_atomic failed')
                    logging.debug('ended atomic')

                    # close db
                    db.close()
                    logging.debug('closed db')

                    # call post-callback
                    if callable(afterwards):
                        logging.debug(str(afterwards))
                        afterwards()
                        logging.debug('called callback')

                # re-insert item to the queue upon Xapian/NotmuchErrors
                except (XapianError, NotmuchError) as e:
                    logging.exception(e)
                    self.writequeue.appendleft(current_item)
                    raise DatabaseError(str(e))
                except DatabaseLockedError as e:
                    logging.debug('index temporarily locked')
                    self.writequeue.appendleft(current_item)
                    raise e
                logging.debug('flush finished')

    def kill_search_processes(self):
        """
        terminate all search processes that originate from
        this managers :meth:`get_threads`.
        """
        for p in self.processes:
            p.terminate()
        self.processes = []

    def tag(self, querystring, tags, afterwards=None, remove_rest=False):
        """
        add tags to messages matching `querystring`.
        This appends a tag operation to the write queue and raises
        :exc:`~errors.DatabaseROError` if in read only mode.

        :param querystring: notmuch search string
        :type querystring: str
        :param tags: a list of tags to be added
        :type tags: list of str
        :param afterwards: callback that gets called after successful
                           application of this tagging operation
        :type afterwards: callable
        :param remove_rest: remove tags from matching messages before tagging
        :type remove_rest: bool
        :exception: :exc:`~errors.DatabaseROError`

        .. note::
            This only adds the requested operation to the write queue.
            You need to call :meth:`DBManager.flush` to actually write out.
        """
        if self.ro:
            raise DatabaseROError()
        if remove_rest:
            self.writequeue.append(('set', afterwards, querystring, tags))
        else:
            self.writequeue.append(('tag', afterwards, querystring, tags))

    def untag(self, querystring, tags, afterwards=None):
        """
        removes tags from messages that match `querystring`.
        This appends an untag operation to the write queue and raises
        :exc:`~errors.DatabaseROError` if in read only mode.

        :param querystring: notmuch search string
        :type querystring: str
        :param tags: a list of tags to be added
        :type tags: list of str
        :param afterwards: callback that gets called after successful
                           application of this tagging operation
        :type afterwards: callable
        :exception: :exc:`~errors.DatabaseROError`

        .. note::
            This only adds the requested operation to the write queue.
            You need to call :meth:`DBManager.flush` to actually write out.
        """
        if self.ro:
            raise DatabaseROError()
        self.writequeue.append(('untag', afterwards, querystring, tags))

    def count_messages(self, querystring):
        """returns number of messages that match `querystring`"""
        return self.query(querystring).count_messages()

    def count_threads(self, querystring):
        """returns number of threads that match `querystring`"""
        return self.query(querystring).count_threads()

    def _get_notmuch_thread(self, tid):
        """returns :class:`notmuch.database.Thread` with given id"""
        query = self.query('thread:' + tid)
        try:
            return next(query.search_threads())
        except StopIteration:
            errmsg = 'no thread with id %s exists!' % tid
            raise NonexistantObjectError(errmsg)

    def get_thread(self, tid):
        """returns :class:`Thread` with given thread id (str)"""
        return Thread(self, self._get_notmuch_thread(tid))

    def _get_notmuch_message(self, mid):
        """returns :class:`notmuch.database.Message` with given id"""
        mode = Database.MODE.READ_ONLY
        db = Database(path=self.path, mode=mode)
        try:
            return db.find_message(mid)
        except:
            errmsg = 'no message with id %s exists!' % mid
            raise NonexistantObjectError(errmsg)

    def get_message(self, mid):
        """returns :class:`Message` with given message id (str)"""
        return Message(self, self._get_notmuch_message(mid))

    def get_all_tags(self):
        """
        returns all tagsstrings used in the database
        :rtype: list of str
        """
        db = Database(path=self.path)
        return [t for t in db.get_all_tags()]

    def get_named_queries(self):
        """
        returns the named queries stored in the database.
        :rtype: dict (str -> str) mapping alias to full query string
        """
        db = Database(path=self.path)
        return {k[6:]: v for k, v in db.get_configs('query.')}

    def async_(self, cbl, fun):
        """
        return a pair (pipe, process) so that the process writes
        `fun(a)` to the pipe for each element `a` in the iterable returned
        by the callable `cbl`.

        :param cbl: a function returning something iterable
        :type cbl: callable
        :param fun: an unary translation function
        :type fun: callable
        :rtype: (:class:`multiprocessing.Pipe`,
                :class:`multiprocessing.Process`)
        """
        # create two unix pipes to redirect the workers stdout and
        # stderr
        stdout = os.pipe()
        stderr = os.pipe()

        # create a multiprocessing pipe for the results
        pipe = multiprocessing.Pipe(False)
        receiver, sender = pipe

        process = FillPipeProcess(cbl(), stdout[1], stderr[1], pipe, fun)
        process.start()
        self.processes.append(process)
        logging.debug('Worker process %s spawned', process.pid)

        def threaded_wait():
            # wait(2) for the process to die
            process.join()

            if process.exitcode < 0:
                msg = 'received signal {0}'.format(-process.exitcode)
            elif process.exitcode > 0:
                msg = 'returned error code {0}'.format(process.exitcode)
            else:
                msg = 'exited successfully'

            logging.debug('Worker process %s %s', process.pid, msg)
            self.processes.remove(process)

        # XXX: it would be much nicer to run this as a coroutine than a thread,
        # except that this code is executed before the eventloop is started.
        #
        # spawn a thread to collect the worker process once it dies
        # preventing it from hanging around as zombie
        threading.Thread(target=threaded_wait).start()

        # TODO: avoid this if logging level > debug
        def threaded_reader(prefix, fd):
            with os.fdopen(fd) as handle:
                for line in handle:
                    logging.debug('Worker process %s said on %s: %s',
                                  process.pid, prefix, line.rstrip())

        # spawn two threads that read from the stdout and stderr pipes
        # and write anything that appears there to the log
        threading.Thread(target=threaded_reader,
                         args=('stdout', stdout[0])).start()
        os.close(stdout[1])
        threading.Thread(target=threaded_reader,
                         args=('stderr', stderr[0])).start()
        os.close(stderr[1])

        # closing the sending end in this (receiving) process guarantees
        # that here the appropriate EOFError is raised upon .recv in the walker
        sender.close()
        return receiver, process

    def get_threads(self, querystring, sort='newest_first', exclude_tags=None):
        """
        asynchronously look up thread ids matching `querystring`.

        :param querystring: The query string to use for the lookup
        :type querystring: str.
        :param sort: Sort order. one of ['oldest_first', 'newest_first',
                     'message_id', 'unsorted']
        :type query: str
        :param exclude_tags: Tags to exclude by default unless included in the
                             search
        :type exclude_tags: list of str
        :returns: a pipe together with the process that asynchronously
                  writes to it.
        :rtype: (:class:`multiprocessing.Pipe`,
                :class:`multiprocessing.Process`)
        """
        assert sort in self._sort_orders
        q = self.query(querystring)
        q.set_sort(self._sort_orders[sort])
        if exclude_tags:
            for tag in exclude_tags:
                q.exclude_tag(tag)
        return self.async_(q.search_threads, (lambda a: a.get_thread_id()))

    def query(self, querystring):
        """
        creates :class:`notmuch.Query` objects on demand

        :param querystring: The query string to use for the lookup
        :type query: str.
        :returns: :class:`notmuch.Query` -- the query object.
        """
        mode = Database.MODE.READ_ONLY
        db = Database(path=self.path, mode=mode)
        q = db.create_query(querystring)
        # add configured exclude tags
        for tag in settings.get('exclude_tags'):
            q.exclude_tag(tag)
        return q

    def add_message(self, path, tags=None, afterwards=None):
        """
        Adds a file to the notmuch index.

        :param path: path to the file
        :type path: str
        :param tags: tagstrings to add
        :type tags: list of str
        :param afterwards: callback to trigger after adding
        :type afterwards: callable or None
        """
        tags = tags or []

        if self.ro:
            raise DatabaseROError()
        if not is_subdir_of(path, self.path):
            msg = 'message path %s ' % path
            msg += ' is not below notmuchs '
            msg += 'root path (%s)' % self.path
            raise DatabaseError(msg)
        else:
            self.writequeue.append(('add', afterwards, path, tags))

    def remove_message(self, message, afterwards=None):
        """
        Remove a message from the notmuch index

        :param message: message to remove
        :type message: :class:`Message`
        :param afterwards: callback to trigger after removing
        :type afterwards: callable or None
        """
        if self.ro:
            raise DatabaseROError()
        path = message.get_filename()
        self.writequeue.append(('remove', afterwards, path))

    def save_named_query(self, alias, querystring, afterwards=None):
        """
        add an alias for a query string.

        These are stored in the notmuch database and can be used as part of
        more complex queries using the syntax "query:alias".
        See :manpage:`notmuch-search-terms(7)` for more info.

        :param alias: name of shortcut
        :type alias: str
        :param querystring: value, i.e., the full query string
        :type querystring: str
        :param afterwards: callback to trigger after adding the alias
        :type afterwards: callable or None
        """
        if self.ro:
            raise DatabaseROError()
        self.writequeue.append(('setconfig', afterwards, 'query.' + alias,
                                querystring))

    def remove_named_query(self, alias, afterwards=None):
        """
        remove a named query from the notmuch database.

        :param alias: name of shortcut
        :type alias: str
        :param afterwards: callback to trigger after adding the alias
        :type afterwards: callable or None
        """
        if self.ro:
            raise DatabaseROError()
        self.writequeue.append(('setconfig', afterwards, 'query.' + alias, ''))
