import collections
import contextlib
import enum
import fcntl
import functools
import os
import pathlib
import queue
import sys
import termios
import threading
import time

import numpy as np

import gi
gi.require_version('GLib', '2.0')
gi.require_version('GObject', '2.0')
gi.require_version('Gst', '1.0')
gi.require_version('GstBase', '1.0')
gi.require_version('GstPbutils', '1.0')

from gi.repository import GLib, GObject, Gst, GstBase

GObject.threads_init()
Gst.init(None)

from gi.repository import GstPbutils  # Must be called after Gst.init().

from PIL import Image

from .gst import *
from .pipelines import *

COMMAND_SAVE_FRAME = ' '
COMMAND_PRINT_INFO = 'p'
COMMAND_QUIT       = 'q'

class Display(enum.Enum):
    FULLSCREEN = 'fullscreen'
    WINDOW = 'window'
    NONE = 'none'

    def __str__(self):
        return self.value

def set_nonblocking(fd):
    flags = fcntl.fcntl(fd, fcntl.F_GETFL)
    return fcntl.fcntl(fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)

@contextlib.contextmanager
def term_raw_mode(fd):
    old = termios.tcgetattr(fd)
    new = termios.tcgetattr(fd)
    new[3] = new[3] & ~(termios.ICANON | termios.ECHO)
    termios.tcsetattr(fd, termios.TCSANOW, new)
    try:
        yield
    finally:
        termios.tcsetattr(fd, termios.TCSAFLUSH, old)

def get_nowait(q):
    try:
        return q.get_nowait()
    except queue.Empty:
        return None

@contextlib.contextmanager
def Worker(process, maxsize=0):
    commands = queue.Queue(maxsize)

    def run():
        while True:
            args = commands.get()
            if args is None:
                break
            process(*args)
            commands.task_done()

    thread = threading.Thread(target=run)
    thread.start()
    try:
        yield commands
    finally:
        commands.put(None)
        thread.join()

def save_frame(rgb, size, overlay=None, ext='png'):
    tag = '%010d' % int(time.monotonic() * 1000)
    img = Image.frombytes('RGB', size, rgb, 'raw')
    name = 'img-%s.%s' % (tag, ext)
    img.save(name)
    print('Frame saved as "%s"' % name)
    if overlay:
        name = 'img-%s.svg' % tag
        with open(name, 'w') as f:
            f.write(overlay)
        print('Overlay saved as "%s"' % name)

Layout = collections.namedtuple('Layout', ('size', 'window', 'inference_size', 'render_size'))

def make_layout(inference_size, render_size):
    size = min_outer_size(inference_size, render_size)
    window = center_inside(render_size, size)
    return Layout(size=size, window=window,
                  inference_size=inference_size, render_size=render_size)

def caps_size(caps):
    structure = caps.get_structure(0)
    return Size(structure.get_value('width'),
                structure.get_value('height'))

def get_video_info(filename):
    uri = pathlib.Path(filename).absolute().as_uri()
    discoverer = GstPbutils.Discoverer()
    info = discoverer.discover_uri(uri)

    streams = info.get_video_streams()
    assert len(streams) == 1
    return streams[0]

def loop():
    return GLib.MainLoop.new(None, False)

@contextlib.contextmanager
def pull_sample(sink):
    sample = sink.emit('pull-sample')
    buf = sample.get_buffer()

    result, mapinfo = buf.map(Gst.MapFlags.READ)
    if result:
        yield sample, mapinfo.data
    buf.unmap(mapinfo)

def new_sample_callback(process):
    def callback(sink, pipeline, loop):
        with pull_sample(sink) as (sample, data):
            process(data, caps_size(sample.get_caps()))
        return Gst.FlowReturn.OK
    return callback

def on_bus_message(bus, message, loop):
    if message.type == Gst.MessageType.EOS:
        loop.quit()
    elif message.type == Gst.MessageType.WARNING:
        err, debug = message.parse_warning()
        sys.stderr.write('Warning: %s: %s\n' % (err, debug))
    elif message.type == Gst.MessageType.ERROR:
        err, debug = message.parse_error()
        sys.stderr.write('Error: %s: %s\n' % (err, debug))
        loop.quit()
    return True

def run_pipeline(loop, pipeline, signals):
    # Create pipeline
    pipeline = describe(pipeline)
    print(pipeline)
    pipeline = Gst.parse_launch(pipeline)

    # Attach signals
    for name, signals in signals.items():
        component = pipeline.get_by_name(name)
        if component:
            for signal_name, signal_handler in signals.items():
                component.connect(signal_name, signal_handler, pipeline, loop)

    # Set up a pipeline bus watch to catch errors.
    bus = pipeline.get_bus()
    bus.add_signal_watch()
    bus.connect('message', on_bus_message, loop)

    # Run pipeline.
    pipeline.set_state(Gst.State.PLAYING)
    try:
        loop.run()
    except KeyboardInterrupt:
        pass
    finally:
        pipeline.set_state(Gst.State.NULL)

    # Process all pending operations on the loop.
    while loop.get_context().iteration(False):
        pass

def on_keypress(fd, flags, commands):
    for ch in sys.stdin.read():
        commands.put(ch)
    return True

def on_new_sample(sink, pipeline, loop, render_overlay, layout, images, commands):
    with pull_sample(sink) as (sample, data):
        custom_command = None
        save_frame = False

        command = get_nowait(commands)
        if command == COMMAND_SAVE_FRAME:
            save_frame = True
        elif command == COMMAND_PRINT_INFO:
            print('Timestamp: %.2f' % time.monotonic())
            print('Render size: %d x %d' % layout.render_size)
            print('Inference size: %d x %d' % layout.inference_size)
        elif  command == COMMAND_QUIT:
            loop.quit()
        else:
            custom_command = command

        svg = render_overlay(np.frombuffer(data, dtype=np.uint8),
                             command=custom_command)
        overlay = pipeline.get_by_name('overlay')
        if overlay:
            overlay.set_property('data', svg)

        if save_frame:
            images.put((data, layout.inference_size, svg))

    return Gst.FlowReturn.OK

def run_gen(render_overlay_gen, *, source, downscale, display):
    inference_size = render_overlay_gen.send(None)  # Initialize.
    return run(inference_size,
        lambda tensor, layout, command:
            render_overlay_gen.send((tensor, layout, command)),
        source=source,
        downscale=downscale,
        display=display)

def run(inference_size, render_overlay, *, source, downscale, display):
    result = get_pipeline(source, inference_size, downscale, display)
    if result:
        layout, pipeline = result
        run_loop(pipeline, layout, render_overlay)
        return True

    return False

def get_pipeline(source, inference_size, downscale, display):
    inference_size = Size(*inference_size)
    fmt = parse_format(source)
    if fmt:
        layout = make_layout(inference_size, fmt.size)
        return layout, camera_pipeline(fmt, layout, display)

    filename = os.path.expanduser(source)
    if os.path.isfile(filename):
        info = get_video_info(filename)
        render_size = Size(info.get_width(), info.get_height()) / downscale
        layout = make_layout(inference_size, render_size)
        return layout, file_pipline(filename, info, layout, display)

    return None

def camera_pipeline(fmt, layout, display):
    if display is Display.NONE:
        return camera_headless_pipeline(fmt, layout)
    else:
        return camera_display_pipeline(fmt, layout, display is Display.FULLSCREEN)

def file_pipline(filename, info, layout, display):
    if display is Display.NONE:
        if info.is_image():
            return image_headless_pipeline(filename, layout)
        else:
            return video_headless_pipeline(filename, layout)
    else:
        fullscreen = display is Display.FULLSCREEN
        if info.is_image():
            return image_display_pipeline(filename, layout, fullscreen)
        else:
            return video_display_pipeline(filename, layout, fullscreen)

def run_loop(pipeline, layout, render_overlay):
    loop = GLib.MainLoop()
    commands = queue.Queue()

    with contextlib.ExitStack() as stack:
        images = stack.enter_context(Worker(save_frame))

        if sys.stdin.isatty():
            set_nonblocking(sys.stdin.fileno())
            GLib.io_add_watch(sys.stdin.fileno(), GLib.IO_IN, on_keypress, commands)
            stack.enter_context(term_raw_mode(sys.stdin.fileno()))

        run_pipeline(loop, pipeline, {'appsink': {'new-sample':
            functools.partial(on_new_sample,
                render_overlay=functools.partial(render_overlay, layout=layout),
                layout=layout,
                images=images,
                commands=commands)}
        })