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import select
from senderbase import SenderBase
from ece361.lab2.frame import Frame

class SlidingWindowSender(SenderBase):
    def __init__(self, file, destination, frame_size, timeout, maxseqnum, sender_window_size):
        super().__init__(file, destination, frame_size, timeout, maxseqnum)
        self.send_queue = []
        self.sender_window_size = sender_window_size

    def _arqsend(self):
        # implementation of the Sliding Window ARQ protocol
        while True:
            # a queue is the perfect data structure for implementing sliding window
            while (len(self.send_queue) < self.sender_window_size):
                # fill up the sending window
                current_frame = self.get_next_frame()
                # add frame to queue
                self.send_queue.append(current_frame)

            if (self.send_queue[0].data == b''):
                # end of file
                break

            ''' Part 2: Implement the sliding window ARQ protocol:'''

            ''' Step 1: Go through the send queue and send those frames that need to be sent/resent'''
            ''' Do not forget to update the frames_sent variable'''
            ''' Your Code'''
            for i in self.send_queue:
                i.send()
                self.frames_sent +=1



            ''' Step 2: wait on all frames in the send_queue in parallel'''
            ''' Hint: call the wait_for_multiple_ack_nacks function'''
            ''' Your Code'''
            Frame.wait_for_multiple_ack_nacks(self.send_queue)





            ''' Step 3: Go through the send queue and process ack/nack/timeout'''
            ''' Use the status() method to check status of the frame'''
            ''' Hint: In the sliding window ARQ if a frame is acked it is implied that all earlier frames are also acked even without receiving an explicit ack(why?)'''
            ''' Your Code'''

            max_ack_nack = 0
            i = len(self.send_queue) -1
            while(i>=0):
                if(self.send_queue[i].status()==Frame.Status.ack_nacked):
                    max_ack_nack = i;
                    break
                i = i-1


            ''' Step 4: Remove acked frames by calling the 'pop' method on the send queue'''
            ''' In the sliding window ARQ there might be more than 1 acked frames in an iteration'''
            ''' so you might need to call 'pop' multiple times'''
            ''' Do not forget to update the frames_delivered variable'''
            ''' Your Code'''
            if(max_ack_nack >=0):
                for i in range(max_ack_nack ):
                    self.send_queue.pop(0)
                    self.frames_delivered = self.frames_delivered + 1