"""
Provides utility classes for the `AlarmDecoder`_ (AD2) devices.

.. _AlarmDecoder: http://www.alarmdecoder.com

.. moduleauthor:: Scott Petersen <scott@nutech.com>
"""

import time
import threading
import select
import sys
import alarmdecoder

from io import open
from collections import deque


class NoDeviceError(Exception):
    """
    No devices found.
    """
    pass


class CommError(Exception):
    """
    There was an error communicating with the device.
    """
    pass


class TimeoutError(Exception):
    """
    There was a timeout while trying to communicate with the device.
    """
    pass


class InvalidMessageError(Exception):
    """
    The format of the panel message was invalid.
    """
    pass


class UploadError(Exception):
    """
    Generic firmware upload error.
    """
    pass


class UploadChecksumError(UploadError):
    """
    The firmware upload failed due to a checksum error.
    """
    pass


def bytes_available(device):
    """
    Determines the number of bytes available for reading from an
    AlarmDecoder device

    :param device: the AlarmDecoder device
    :type device: :py:class:`~alarmdecoder.devices.Device`

    :returns: int
    """
    bytes_avail = 0

    if isinstance(device, alarmdecoder.devices.SerialDevice):
        if hasattr(device._device, "in_waiting"):
            bytes_avail = device._device.in_waiting
        else:
            bytes_avail = device._device.inWaiting()
    elif isinstance(device, alarmdecoder.devices.SocketDevice):
        bytes_avail = 4096

    return bytes_avail

def bytes_hack(buf):
    """
    Hacky workaround for old installs of the library on systems without python-future that were
    keeping the 2to3 update from working after auto-update.
    """
    ub = None
    if sys.version_info > (3,):
        ub = buf
    else:
        ub = bytes(buf)

    return ub

def filter_ad2prot_byte(buf):
    """
    Return the byte sent in back if valid visible terminal characters or line terminators.
    """
    if sys.version_info > (3,):
        c = buf[0]
    else:
        c = ord(buf)

    if (c == 10 or c == 13):
        return buf
    if (c > 31 and c < 127):
        return buf
    else:
        return b''

def read_firmware_file(file_path):
    """
    Reads a firmware file into a dequeue for processing.

    :param file_path: Path to the firmware file
    :type file_path: string

    :returns: deque
    """
    data_queue = deque()

    with open(file_path) as firmware_handle:
        for line in firmware_handle:
            line = line.rstrip()
            if line != '' and line[0] == ':':
                data_queue.append(line + "\r")

    return data_queue

class Firmware(object):
    """
    Represents firmware for the `AlarmDecoder`_ devices.
    """

    # Constants
    STAGE_START = 0
    STAGE_WAITING = 1
    STAGE_BOOT = 2
    STAGE_WAITING_ON_LOADER = 2.5
    STAGE_LOAD = 3
    STAGE_UPLOADING = 4
    STAGE_DONE = 5
    STAGE_ERROR = 98
    STAGE_DEBUG = 99

    @staticmethod
    def read(device):
        """
        Reads data from the specified device.

        :param device: the AlarmDecoder device
        :type device: :py:class:`~alarmdecoder.devices.Device`

        :returns: string
        """
        response = None
        bytes_avail = bytes_available(device)

        if isinstance(device, alarmdecoder.devices.SerialDevice):
            response = device._device.read(bytes_avail)
        elif isinstance(device, alarmdecoder.devices.SocketDevice):
            response = device._device.recv(bytes_avail)

        return response

    @staticmethod
    def upload(device, file_path, progress_callback=None, debug=False):
        """
        Uploads firmware to an `AlarmDecoder`_ device.

        :param file_path: firmware file path
        :type file_path: string
        :param progress_callback: callback function used to report progress
        :type progress_callback: function

        :raises: :py:class:`~alarmdecoder.util.NoDeviceError`, :py:class:`~alarmdecoder.util.TimeoutError`
        """

        def progress_stage(stage, **kwargs):
            """Callback to update progress for the specified stage."""
            if progress_callback is not None:
                progress_callback(stage, **kwargs)

            return stage

        if device is None:
            raise NoDeviceError('No device specified for firmware upload.')

        fds = [device._device.fileno()]

        # Read firmware file into memory
        try:
            write_queue = read_firmware_file(file_path)
        except IOError as err:
            stage = progress_stage(Firmware.STAGE_ERROR, error=str(err))
            return

        data_read = ''
        got_response = False
        running = True
        stage = progress_stage(Firmware.STAGE_START)

        if device.is_reader_alive():
            # Close the reader thread and wait for it to die, otherwise
            # it interferes with our reading.
            device.stop_reader()
            while device._read_thread.is_alive():
                stage = progress_stage(Firmware.STAGE_WAITING)
                time.sleep(0.5)

            time.sleep(3)

        try:
            while running:
                rr, wr, _ = select.select(fds, fds, [], 0.5)

                if len(rr) != 0:
                    response = Firmware.read(device)

                    for c in response:
                        # HACK: Python 3 / PySerial hack.
                        if isinstance(c, int):
                            c = chr(c)

                        if c == '\xff' or c == '\r':    # HACK: odd case for our mystery \xff byte.
                            # Boot started, start looking for the !boot message
                            if data_read.startswith("!sn"):
                                stage = progress_stage(Firmware.STAGE_BOOT)
                            # Entered bootloader upload mode, start uploading
                            elif data_read.startswith("!load"):
                                got_response = True
                                stage = progress_stage(Firmware.STAGE_UPLOADING)
                            # Checksum error
                            elif data_read == '!ce':
                                running = False
                                raise UploadChecksumError("Checksum error in {0}".format(file_path))
                            # Bad data
                            elif data_read == '!no':
                                running = False
                                raise UploadError("Incorrect data sent to bootloader.")
                            # Firmware upload complete
                            elif data_read == '!ok':
                                running = False
                                stage = progress_stage(Firmware.STAGE_DONE)
                            # All other responses are valid during upload.
                            else:
                                got_response = True
                                if stage == Firmware.STAGE_UPLOADING:
                                    progress_stage(stage)

                            data_read = ''
                        elif c == '\n':
                            pass
                        else:
                            data_read += c

                if len(wr) != 0:
                    # Reboot device
                    if stage in [Firmware.STAGE_START, Firmware.STAGE_WAITING]:
                        device.write('=')
                        stage = progress_stage(Firmware.STAGE_WAITING_ON_LOADER)

                    # Enter bootloader
                    elif stage == Firmware.STAGE_BOOT:
                        device.write('=')
                        stage = progress_stage(Firmware.STAGE_LOAD)

                    # Upload firmware
                    elif stage == Firmware.STAGE_UPLOADING:
                        if len(write_queue) > 0 and got_response == True:
                            got_response = False
                            device.write(write_queue.popleft())

        except UploadError as err:
            stage = progress_stage(Firmware.STAGE_ERROR, error=str(err))
        else:
            stage = progress_stage(Firmware.STAGE_DONE)