#    Copyright 2016 ARM Limited
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import os
import struct
from datetime import datetime
from collections import namedtuple


GENERAL_MODE = 0
GAMEPAD_MODE = 1


u16_struct = struct.Struct('<H')
u32_struct = struct.Struct('<I')
u64_struct = struct.Struct('<Q')

# See revent section in WA documentation for the detailed description of
# the recording format.
header_one_struct = struct.Struct('<6sH')
header_two_struct = struct.Struct('<H6x')  # version 2 onwards

devid_struct = struct.Struct('<4H')
devinfo_struct = struct.Struct('<4s96s96s96sI')
absinfo_struct = struct.Struct('<7i')

event_struct = struct.Struct('<HqqHHi')
old_event_struct = struct.Struct("<i4xqqHHi")  # prior to version 2


def read_struct(fh, struct_spec):
    data = fh.read(struct_spec.size)
    return struct_spec.unpack(data)


def read_string(fh):
    length, = read_struct(fh, u32_struct)
    str_struct = struct.Struct('<{}s'.format(length))
    return read_struct(fh, str_struct)[0]


def count_bits(bitarr):
    return sum(bin(b).count('1') for b in bitarr)


def is_set(bitarr, bit):
    byte = bit // 8
    bytebit = bit % 8
    return bitarr[byte] & bytebit


absinfo = namedtuple('absinfo', 'ev_code value min max fuzz flat resolution')


class UinputDeviceInfo(object):

    def __init__(self, fh):
        parts = read_struct(fh, devid_struct)
        self.bustype = parts[0]
        self.vendor = parts[1]
        self.product = parts[2]
        self.version = parts[3]

        self.name = read_string(fh)

        parts = read_struct(fh, devinfo_struct)
        self.ev_bits = bytearray(parts[0])
        self.key_bits = bytearray(parts[1])
        self.rel_bits = bytearray(parts[2])
        self.abs_bits = bytearray(parts[3])
        self.num_absinfo = parts[4]
        self.absinfo = [absinfo(*read_struct(fh, absinfo_struct))
                        for _ in xrange(self.num_absinfo)]

    def __str__(self):
        return 'UInputInfo({})'.format(self.__dict__)


class ReventEvent(object):

    def __init__(self, fh, legacy=False):
        if not legacy:
            dev_id, ts_sec, ts_usec, type_, code, value = read_struct(fh, event_struct)
        else:
            dev_id, ts_sec, ts_usec, type_, code, value = read_struct(fh, old_event_struct)
        self.device_id = dev_id
        self.time = datetime.fromtimestamp(ts_sec + float(ts_usec) / 1000000)
        self.type = type_
        self.code = code
        self.value = value

    def __str__(self):
        return 'InputEvent({})'.format(self.__dict__)


class ReventRecording(object):
    """
    Represents a parsed revent recording. This contains input events and device
    descriptions recorded by revent. Two parsing modes are supported. By
    default, the recording will be parsed in the "streaming" mode. In this
    mode, initial headers and device descritions are parsed on creation and an
    open file handle to the recording is saved. Events will be read from the
    file as they are being iterated over. In this mode, the entire recording is
    never loaded into memory at once. The underlying file may be "released" by
    calling ``close`` on the recroding, after which further iteration over the
    events will not be possible (but would still be possible to access the file
    description and header information).

    The alternative is to load the entire recording on creation (in which case
    the file handle will be closed once the recroding is loaded). This can be
    enabled by specifying ``streaming=False``. This will make it faster to
    subsequently iterate over the events, and also will not "hold" the file
    open.

    .. note:: When starting a new iteration over the events in streaming mode,
              the postion in the open file will be automatically reset to the
              beginning of the event stream. This means it's possible to iterate
              over the events multiple times without having to re-open the
              recording, however it is not possible to do so in parallel. If
              parallel iteration is required, streaming should be disabled.

    """

    @property
    def duration(self):
        if self._duration is None:
            if self.stream:
                events = self._iter_events()
                try:
                    first = last = events.next()
                except StopIteration:
                    self._duration = 0
                else:
                    for last in events:
                        pass
                    self._duration = (last.time - first.time).total_seconds()
            else:  # not streaming
                if not self._events:
                    self._duration = 0
                self._duration = (self._events[-1].time -
                                  self._events[0].time).total_seconds()
        return self._duration

    @property
    def events(self):
        if self.stream:
            return self._iter_events()
        else:
            return self._events

    def __init__(self, f, stream=True):
        self.device_paths = []
        self.gamepad_device = None
        self.num_events = None
        self.stream = stream
        self._events = None
        self._close_when_done = False
        self._events_start = None
        self._duration = None

        if hasattr(f, 'name'):  # file-like object
            self.filepath = f.name
            self.fh = f
        else:  # path to file
            self.filepath = f
            self.fh = open(self.filepath, 'rb')
            if not self.stream:
                self._close_when_done = True
        try:
            self._parse_header_and_devices(self.fh)
            self._events_start = self.fh.tell()
            if not self.stream:
                self._events = [e for e in self._iter_events()]
        finally:
            if self._close_when_done:
                self.close()

    def close(self):
        if self.fh is not None:
            self.fh.close()
            self.fh = None
            self._events_start = None

    def _parse_header_and_devices(self, fh):
        magic, version = read_struct(fh, header_one_struct)
        if magic != 'REVENT':
            raise ValueError('{} does not appear to be an revent recording'.format(self.filepath))
        self.version = version

        if self.version == 2:
            self.mode, = read_struct(fh, header_two_struct)
            if self.mode == GENERAL_MODE:
                self._read_devices(fh)
            elif self.mode == GAMEPAD_MODE:
                self._read_gamepad_info(fh)
            else:
                raise ValueError('Unexpected recording mode: {}'.format(self.mode))
            self.num_events, = read_struct(fh, u64_struct)
        elif 2 > self.version >= 0:
            self.mode = GENERAL_MODE
            self._read_devices(fh)
        else:
            raise ValueError('Invalid recording version: {}'.format(self.version))

    def _read_devices(self, fh):
        num_devices, = read_struct(fh, u32_struct)
        for _ in xrange(num_devices):
            self.device_paths.append(read_string(fh))

    def _read_gamepad_info(self, fh):
        self.gamepad_device = UinputDeviceInfo(fh)
        self.device_paths.append('[GAMEPAD]')

    def _iter_events(self):
        if self.fh is None:
            raise RuntimeError('Attempting to iterate over events of a closed recording')
        self.fh.seek(self._events_start)
        if self.version >= 2:
            for _ in xrange(self.num_events):
                yield ReventEvent(self.fh)
        else:
            file_size = os.path.getsize(self.filepath)
            while self.fh.tell() < file_size:
                yield ReventEvent(self.fh, legacy=True)

    def __iter__(self):
        for event in self.events:
            yield event

    def __enter__(self):
        return self

    def __exit__(self, *args):
        self.close()

    def __del__(self):
        self.close()
