from collections import deque
import bbctrl


# 16-bit less with wrap around
def id_less(a, b):
    return (1 << 15) < (a - b) & ((1 << 16) - 1)


class CommandQueue():

    def __init__(self, ctrl):
        self.log = ctrl.log.get('CmdQ')
        self.log.set_level(bbctrl.log.WARNING)

        self.lastEnqueueID = 0
        self.releaseID = 0
        self.q = deque()

    def is_active(self):
        return len(self.q)

    def clear(self):
        self.lastEnqueueID = 0
        self.releaseID = 0
        self.q.clear()

    def enqueue(self, id, cb, *args, **kwargs):
        self.log.info('add(#%d) releaseID=%d', id, self.releaseID)
        self.lastEnqueueID = id
        self.q.append([id, cb, args, kwargs])
        self._release()

    def _release(self):
        while len(self.q):
            id, cb, args, kwargs = self.q[0]

            # Execute commands <= releaseID
            if id_less(self.releaseID, id): return

            self.log.info('releasing id=%d' % id)
            self.q.popleft()

            try:
                if cb is not None: cb(*args, **kwargs)
            except Exception:
                self.log.exception(
                    'Internal error: Command queue callback error')

    def release(self, id):
        if id and not id_less(self.releaseID, id):
            self.log.debug('id out of order %d <= %d' % (id, self.releaseID))
        self.releaseID = id

        self._release()