# Copyright (c) 2009-2012 Denis Bilenko. See LICENSE for details.
"""Synchronized queues.

The :mod:`gevent.queue` module implements multi-producer, multi-consumer queues
that work across greenlets, with the API similar to the classes found in the
standard :mod:`Queue` and :class:`multiprocessing <multiprocessing.Queue>` modules.

The classes in this module implement iterator protocol. Iterating over queue
means repeatedly calling :meth:`get <Queue.get>` until :meth:`get <Queue.get>` returns ``StopIteration``.

    >>> queue = gevent.queue.Queue()
    >>> queue.put(1)
    >>> queue.put(2)
    >>> queue.put(StopIteration)
    >>> for item in queue:
    ...    print(item)
    1
    2

.. versionchanged:: 1.0
       ``Queue(0)`` now means queue of infinite size, not a channel. A :exc:`DeprecationWarning`
       will be issued with this argument.
"""

from __future__ import absolute_import
import sys
import heapq
import collections

if sys.version_info[0] == 2:
    import Queue as __queue__
else:
    import queue as __queue__
Full = __queue__.Full
Empty = __queue__.Empty

from gevent.timeout import Timeout
from gevent.hub import get_hub, Waiter, getcurrent, PY3
from gevent.hub import InvalidSwitchError


__all__ = ['Queue', 'PriorityQueue', 'LifoQueue', 'JoinableQueue', 'Channel']


def _safe_remove(deq, item):
    # For when the item may have been removed by
    # Queue._unlock
    try:
        deq.remove(item)
    except ValueError:
        pass


class Queue(object):
    """
    Create a queue object with a given maximum size.

    If *maxsize* is less than or equal to zero or ``None``, the queue
    size is infinite.

    .. versionchanged:: 1.1b3
       Queue's now support :func:`len`; it behaves the same as :meth:`qsize`.
    .. versionchanged:: 1.1b3
       Multiple greenlets that block on a call to :meth:`put` for a full queue
       will now be woken up to put their items into the queue in the order in which
       they arrived. Likewise, multiple greenlets that block on a call to :meth:`get` for
       an empty queue will now receive items in the order in which they blocked. An
       implementation quirk under CPython *usually* ensured this was roughly the case
       previously anyway, but that wasn't the case for PyPy.
    """

    def __init__(self, maxsize=None, items=None):
        if maxsize is not None and maxsize <= 0:
            self.maxsize = None
            if maxsize == 0:
                import warnings
                warnings.warn('Queue(0) now equivalent to Queue(None); if you want a channel, use Channel',
                              DeprecationWarning, stacklevel=2)
        else:
            self.maxsize = maxsize
        # Explicitly maintain order for getters and putters that block
        # so that callers can consistently rely on getting things out
        # in the apparent order they went in. This was once required by
        # imap_unordered. Previously these were set() objects, and the
        # items put in the set have default hash() and eq() methods;
        # under CPython, since new objects tend to have increasing
        # hash values, this tended to roughly maintain order anyway,
        # but that's not true under PyPy. An alternative to a deque
        # (to avoid the linear scan of remove()) might be an
        # OrderedDict, but it's 2.7 only; we don't expect to have so
        # many waiters that removing an arbitrary element is a
        # bottleneck, though.
        self.getters = collections.deque()
        self.putters = collections.deque()
        self.hub = get_hub()
        self._event_unlock = None
        if items:
            self._init(maxsize, items)
        else:
            self._init(maxsize)

    # QQQ make maxsize into a property with setter that schedules unlock if necessary

    def copy(self):
        return type(self)(self.maxsize, self.queue)

    def _init(self, maxsize, items=None):
        if items:
            self.queue = collections.deque(items)
        else:
            self.queue = collections.deque()

    def _get(self):
        return self.queue.popleft()

    def _peek(self):
        return self.queue[0]

    def _put(self, item):
        self.queue.append(item)

    def __repr__(self):
        return '<%s at %s%s>' % (type(self).__name__, hex(id(self)), self._format())

    def __str__(self):
        return '<%s%s>' % (type(self).__name__, self._format())

    def _format(self):
        result = []
        if self.maxsize is not None:
            result.append('maxsize=%r' % (self.maxsize, ))
        if getattr(self, 'queue', None):
            result.append('queue=%r' % (self.queue, ))
        if self.getters:
            result.append('getters[%s]' % len(self.getters))
        if self.putters:
            result.append('putters[%s]' % len(self.putters))
        if result:
            return ' ' + ' '.join(result)
        else:
            return ''

    def qsize(self):
        """Return the size of the queue."""
        return len(self.queue)

    def __len__(self):
        """
        Return the size of the queue. This is the same as :meth:`qsize`.

        .. versionadded: 1.1b3

            Previously, getting len() of a queue would raise a TypeError.
        """

        return self.qsize()

    def __bool__(self):
        """
        A queue object is always True.

        .. versionadded: 1.1b3

           Now that queues support len(), they need to implement ``__bool__``
           to return True for backwards compatibility.
        """
        return True
    __nonzero__ = __bool__

    def empty(self):
        """Return ``True`` if the queue is empty, ``False`` otherwise."""
        return not self.qsize()

    def full(self):
        """Return ``True`` if the queue is full, ``False`` otherwise.

        ``Queue(None)`` is never full.
        """
        return self.maxsize is not None and self.qsize() >= self.maxsize

    def put(self, item, block=True, timeout=None):
        """Put an item into the queue.

        If optional arg *block* is true and *timeout* is ``None`` (the default),
        block if necessary until a free slot is available. If *timeout* is
        a positive number, it blocks at most *timeout* seconds and raises
        the :class:`Full` exception if no free slot was available within that time.
        Otherwise (*block* is false), put an item on the queue if a free slot
        is immediately available, else raise the :class:`Full` exception (*timeout*
        is ignored in that case).
        """
        if self.maxsize is None or self.qsize() < self.maxsize:
            # there's a free slot, put an item right away
            self._put(item)
            if self.getters:
                self._schedule_unlock()
        elif self.hub is getcurrent():
            # We're in the mainloop, so we cannot wait; we can switch to other greenlets though.
            # Check if possible to get a free slot in the queue.
            while self.getters and self.qsize() and self.qsize() >= self.maxsize:
                getter = self.getters.popleft()
                getter.switch(getter)
            if self.qsize() < self.maxsize:
                self._put(item)
                return
            raise Full
        elif block:
            waiter = ItemWaiter(item, self)
            self.putters.append(waiter)
            timeout = Timeout._start_new_or_dummy(timeout, Full)
            try:
                if self.getters:
                    self._schedule_unlock()
                result = waiter.get()
                if result is not waiter:
                    raise InvalidSwitchError("Invalid switch into Queue.put: %r" % (result, ))
            finally:
                timeout.cancel()
                _safe_remove(self.putters, waiter)
        else:
            raise Full

    def put_nowait(self, item):
        """Put an item into the queue without blocking.

        Only enqueue the item if a free slot is immediately available.
        Otherwise raise the :class:`Full` exception.
        """
        self.put(item, False)

    def __get_or_peek(self, method, block, timeout):
        # Internal helper method. The `method` should be either
        # self._get when called from self.get() or self._peek when
        # called from self.peek(). Call this after the initial check
        # to see if there are items in the queue.

        if self.hub is getcurrent():
            # special case to make get_nowait() or peek_nowait() runnable in the mainloop greenlet
            # there are no items in the queue; try to fix the situation by unlocking putters
            while self.putters:
                # Note: get() used popleft(), peek used pop(); popleft
                # is almost certainly correct.
                self.putters.popleft().put_and_switch()
                if self.qsize():
                    return method()
            raise Empty()

        if not block:
            # We can't block, we're not the hub, and we have nothing
            # to return. No choice...
            raise Empty()

        waiter = Waiter()
        timeout = Timeout._start_new_or_dummy(timeout, Empty)
        try:
            self.getters.append(waiter)
            if self.putters:
                self._schedule_unlock()
            result = waiter.get()
            if result is not waiter:
                raise InvalidSwitchError('Invalid switch into Queue.get: %r' % (result, ))
            return method()
        finally:
            timeout.cancel()
            _safe_remove(self.getters, waiter)

    def get(self, block=True, timeout=None):
        """Remove and return an item from the queue.

        If optional args *block* is true and *timeout* is ``None`` (the default),
        block if necessary until an item is available. If *timeout* is a positive number,
        it blocks at most *timeout* seconds and raises the :class:`Empty` exception
        if no item was available within that time. Otherwise (*block* is false), return
        an item if one is immediately available, else raise the :class:`Empty` exception
        (*timeout* is ignored in that case).
        """
        if self.qsize():
            if self.putters:
                self._schedule_unlock()
            return self._get()

        return self.__get_or_peek(self._get, block, timeout)

    def get_nowait(self):
        """Remove and return an item from the queue without blocking.

        Only get an item if one is immediately available. Otherwise
        raise the :class:`Empty` exception.
        """
        return self.get(False)

    def peek(self, block=True, timeout=None):
        """Return an item from the queue without removing it.

        If optional args *block* is true and *timeout* is ``None`` (the default),
        block if necessary until an item is available. If *timeout* is a positive number,
        it blocks at most *timeout* seconds and raises the :class:`Empty` exception
        if no item was available within that time. Otherwise (*block* is false), return
        an item if one is immediately available, else raise the :class:`Empty` exception
        (*timeout* is ignored in that case).
        """
        if self.qsize():
            # XXX: Why doesn't this schedule an unlock like get() does?
            return self._peek()

        return self.__get_or_peek(self._peek, block, timeout)

    def peek_nowait(self):
        """Return an item from the queue without blocking.

        Only return an item if one is immediately available. Otherwise
        raise the :class:`Empty` exception.
        """
        return self.peek(False)

    def _unlock(self):
        while True:
            repeat = False
            if self.putters and (self.maxsize is None or self.qsize() < self.maxsize):
                repeat = True
                try:
                    putter = self.putters.popleft()
                    self._put(putter.item)
                except:
                    putter.throw(*sys.exc_info())
                else:
                    putter.switch(putter)
            if self.getters and self.qsize():
                repeat = True
                getter = self.getters.popleft()
                getter.switch(getter)
            if not repeat:
                return

    def _schedule_unlock(self):
        if not self._event_unlock:
            self._event_unlock = self.hub.loop.run_callback(self._unlock)

    def __iter__(self):
        return self

    def next(self):
        result = self.get()
        if result is StopIteration:
            raise result
        return result

    if PY3:
        __next__ = next
        del next


class ItemWaiter(Waiter):
    __slots__ = ['item', 'queue']

    def __init__(self, item, queue):
        Waiter.__init__(self)
        self.item = item
        self.queue = queue

    def put_and_switch(self):
        self.queue._put(self.item)
        self.queue = None
        self.item = None
        return self.switch(self)


class PriorityQueue(Queue):
    '''A subclass of :class:`Queue` that retrieves entries in priority order (lowest first).

    Entries are typically tuples of the form: ``(priority number, data)``.
    '''

    def _init(self, maxsize, items=None):
        if items:
            self.queue = list(items)
        else:
            self.queue = []

    def _put(self, item, heappush=heapq.heappush):
        heappush(self.queue, item)

    def _get(self, heappop=heapq.heappop):
        return heappop(self.queue)


class LifoQueue(Queue):
    '''A subclass of :class:`Queue` that retrieves most recently added entries first.'''

    def _init(self, maxsize, items=None):
        if items:
            self.queue = list(items)
        else:
            self.queue = []

    def _put(self, item):
        self.queue.append(item)

    def _get(self):
        return self.queue.pop()

    def _peek(self):
        return self.queue[-1]


class JoinableQueue(Queue):
    '''A subclass of :class:`Queue` that additionally has :meth:`task_done` and :meth:`join` methods.'''

    def __init__(self, maxsize=None, items=None, unfinished_tasks=None):
        from gevent.event import Event
        Queue.__init__(self, maxsize, items)
        self._cond = Event()
        self._cond.set()

        if unfinished_tasks:
            self.unfinished_tasks = unfinished_tasks
        elif items:
            self.unfinished_tasks = len(items)
        else:
            self.unfinished_tasks = 0

        if self.unfinished_tasks:
            self._cond.clear()

    def copy(self):
        return type(self)(self.maxsize, self.queue, self.unfinished_tasks)

    def _format(self):
        result = Queue._format(self)
        if self.unfinished_tasks:
            result += ' tasks=%s _cond=%s' % (self.unfinished_tasks, self._cond)
        return result

    def _put(self, item):
        Queue._put(self, item)
        self.unfinished_tasks += 1
        self._cond.clear()

    def task_done(self):
        '''Indicate that a formerly enqueued task is complete. Used by queue consumer threads.
        For each :meth:`get <Queue.get>` used to fetch a task, a subsequent call to :meth:`task_done` tells the queue
        that the processing on the task is complete.

        If a :meth:`join` is currently blocking, it will resume when all items have been processed
        (meaning that a :meth:`task_done` call was received for every item that had been
        :meth:`put <Queue.put>` into the queue).

        Raises a :exc:`ValueError` if called more times than there were items placed in the queue.
        '''
        if self.unfinished_tasks <= 0:
            raise ValueError('task_done() called too many times')
        self.unfinished_tasks -= 1
        if self.unfinished_tasks == 0:
            self._cond.set()

    def join(self, timeout=None):
        '''Block until all items in the queue have been gotten and processed.

        The count of unfinished tasks goes up whenever an item is added to the queue.
        The count goes down whenever a consumer thread calls :meth:`task_done` to indicate
        that the item was retrieved and all work on it is complete. When the count of
        unfinished tasks drops to zero, :meth:`join` unblocks.

        :param float timeout: If not ``None``, then wait no more than this time in seconds
            for all tasks to finish.
        :return: ``True`` if all tasks have finished; if ``timeout`` was given and expired before
            all tasks finished, ``False``.
        '''
        return self._cond.wait(timeout=timeout)


class Channel(object):

    def __init__(self):
        self.getters = collections.deque()
        self.putters = collections.deque()
        self.hub = get_hub()
        self._event_unlock = None

    def __repr__(self):
        return '<%s at %s %s>' % (type(self).__name__, hex(id(self)), self._format())

    def __str__(self):
        return '<%s %s>' % (type(self).__name__, self._format())

    def _format(self):
        result = ''
        if self.getters:
            result += ' getters[%s]' % len(self.getters)
        if self.putters:
            result += ' putters[%s]' % len(self.putters)
        return result

    @property
    def balance(self):
        return len(self.putters) - len(self.getters)

    def qsize(self):
        return 0

    def empty(self):
        return True

    def full(self):
        return True

    def put(self, item, block=True, timeout=None):
        if self.hub is getcurrent():
            if self.getters:
                getter = self.getters.popleft()
                getter.switch(item)
                return
            raise Full

        if not block:
            timeout = 0

        waiter = Waiter()
        item = (item, waiter)
        self.putters.append(item)
        timeout = Timeout._start_new_or_dummy(timeout, Full)
        try:
            if self.getters:
                self._schedule_unlock()
            result = waiter.get()
            if result is not waiter:
                raise InvalidSwitchError("Invalid switch into Channel.put: %r" % (result, ))
        except:
            _safe_remove(self.putters, item)
            raise
        finally:
            timeout.cancel()

    def put_nowait(self, item):
        self.put(item, False)

    def get(self, block=True, timeout=None):
        if self.hub is getcurrent():
            if self.putters:
                item, putter = self.putters.popleft()
                self.hub.loop.run_callback(putter.switch, putter)
                return item

        if not block:
            timeout = 0

        waiter = Waiter()
        timeout = Timeout._start_new_or_dummy(timeout, Empty)
        try:
            self.getters.append(waiter)
            if self.putters:
                self._schedule_unlock()
            return waiter.get()
        except:
            self.getters.remove(waiter)
            raise
        finally:
            timeout.cancel()

    def get_nowait(self):
        return self.get(False)

    def _unlock(self):
        while self.putters and self.getters:
            getter = self.getters.popleft()
            item, putter = self.putters.popleft()
            getter.switch(item)
            putter.switch(putter)

    def _schedule_unlock(self):
        if not self._event_unlock:
            self._event_unlock = self.hub.loop.run_callback(self._unlock)

    def __iter__(self):
        return self

    def next(self):
        result = self.get()
        if result is StopIteration:
            raise result
        return result
