"""
QEMU Console Socket Module:

This python module implements a ConsoleSocket object,
which can drain a socket and optionally dump the bytes to file.
"""
# Copyright 2020 Linaro
#
# Authors:
#  Robert Foley <robert.foley@linaro.org>
#
# This code is licensed under the GPL version 2 or later.  See
# the COPYING file in the top-level directory.
#

import asyncore
import socket
import threading
from collections import deque
import time


class ConsoleSocket(asyncore.dispatcher):
    """
    ConsoleSocket represents a socket attached to a char device.

    Drains the socket and places the bytes into an in memory buffer
    for later processing.

    Optionally a file path can be passed in and we will also
    dump the characters to this file for debugging purposes.
    """
    def __init__(self, address, file=None):
        self._recv_timeout_sec = 300
        self._sleep_time = 0.5
        self._buffer = deque()
        self._asyncore_thread = None
        self._sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        self._sock.connect(address)
        self._logfile = None
        if file:
            self._logfile = open(file, "w")
        asyncore.dispatcher.__init__(self, sock=self._sock)
        self._open = True
        self._thread_start()

    def _thread_start(self):
        """Kick off a thread to wait on the asyncore.loop"""
        if self._asyncore_thread is not None:
            return
        self._asyncore_thread = threading.Thread(target=asyncore.loop,
                                                 kwargs={'timeout':1})
        self._asyncore_thread.daemon = True
        self._asyncore_thread.start()

    def handle_close(self):
        """redirect close to base class"""
        # Call the base class close, but not self.close() since
        # handle_close() occurs in the context of the thread which
        # self.close() attempts to join.
        asyncore.dispatcher.close(self)

    def close(self):
        """Close the base object and wait for the thread to terminate"""
        if self._open:
            self._open = False
            asyncore.dispatcher.close(self)
            if self._asyncore_thread is not None:
                thread, self._asyncore_thread = self._asyncore_thread, None
                thread.join()
            if self._logfile:
                self._logfile.close()
                self._logfile = None

    def handle_read(self):
        """process arriving characters into in memory _buffer"""
        data = asyncore.dispatcher.recv(self, 1)
        # latin1 is needed since there are some chars
        # we are receiving that cannot be encoded to utf-8
        # such as 0xe2, 0x80, 0xA6.
        string = data.decode("latin1")
        if self._logfile:
            self._logfile.write("{}".format(string))
            self._logfile.flush()
        for c in string:
            self._buffer.extend(c)

    def recv(self, buffer_size=1):
        """Return chars from in memory buffer.
           Maintains the same API as socket.socket.recv.
        """
        start_time = time.time()
        while len(self._buffer) < buffer_size:
            time.sleep(self._sleep_time)
            elapsed_sec = time.time() - start_time
            if elapsed_sec > self._recv_timeout_sec:
                raise socket.timeout
        chars = ''.join([self._buffer.popleft() for i in range(buffer_size)])
        # We choose to use latin1 to remain consistent with
        # handle_read() and give back the same data as the user would
        # receive if they were reading directly from the
        # socket w/o our intervention.
        return chars.encode("latin1")

    def set_blocking(self):
        """Maintain compatibility with socket API"""
        pass

    def settimeout(self, seconds):
        """Set current timeout on recv"""
        self._recv_timeout_sec = seconds