
import datetime
import errno
import functools
import json
import logging
import os
import subprocess
from uuid import uuid4

import gevent
import gevent.backdoor
import prometheus_client as prom
from flask import Flask, url_for, request, abort, Response
from gevent.pywsgi import WSGIServer

from common import dateutil, get_best_segments, rough_cut_segments, fast_cut_segments, full_cut_segments, PromLogCountsHandler, install_stacksampler, serve_with_graceful_shutdown
from common.flask_stats import request_stats, after_request
from common.segments import feed_input, render_segments_waveform

from . import generate_hls


app = Flask('restreamer', static_url_path='/segments')
app.after_request(after_request)


"""
The restreamer is a simple http api for listing available segments and generating
HLS playlists for them.

The segments themselves are ideally to be served by some external webserver
under "/segments/<channel>/<quality>/<hour>/<filename>" (ie. with BASE_DIR
under "/segments"), though this server will also serve them if requested.
"""


def listdir(path, error=True):
	"""List files in path, excluding hidden files.
	Behaviour when path doesn't exist depends on error arg.
	If error is True, raise 404. Otherwise, return [].
	"""
	try:
		return [name for name in os.listdir(path) if not name.startswith('.')]
	except OSError as e:
		if e.errno != errno.ENOENT:
			raise
		if error:
			abort(404)
		return []


def has_path_args(fn):
	"""Decorator to wrap routes which take args which are to be used as parts of a filepath.
	Disallows hidden folders and path traversal.
	"""
	@functools.wraps(fn)
	def _has_path_args(**kwargs):
		for key, value in kwargs.items():
			# Disallowing a leading . prevents both hidden files and path traversal ("..")
			if value.startswith('.'):
				return "Bad {}: May not start with a period".format(key), 403
		return fn(**kwargs)
	return _has_path_args


def cors(app):
	"""WSGI middleware that sets CORS headers"""
	HEADERS = [
		("Access-Control-Allow-Credentials", "false"),
		("Access-Control-Allow-Headers", "*"),
		("Access-Control-Allow-Methods", "GET,POST,HEAD"),
		("Access-Control-Allow-Origin", "*"),
		("Access-Control-Max-Age", "86400"),
	]
	def handle(environ, start_response):
		def _start_response(status, headers, exc_info=None):
			headers += HEADERS
			return start_response(status, headers, exc_info)
		return app(environ, _start_response)
	return handle


@app.route('/metrics')
@request_stats
def metrics():
	"""Return current metrics in prometheus metrics format"""
	return prom.generate_latest()

# To make nginx proxying simpler, we want to allow /metrics/* to work
@app.route('/metrics/<trailing>')
@request_stats
def metrics_with_trailing(trailing):
       """Expose Prometheus metrics."""
       return prom.generate_latest()

@app.route('/files')
@request_stats
def list_channels():
	"""Returns a JSON list of channels for which there may be segments available.
	Returns empty list if no channels are available.
	"""
	path = app.static_folder
	return json.dumps(listdir(path, error=False))


@app.route('/files/<channel>')
@request_stats
@has_path_args
def list_qualities(channel):
	"""Returns a JSON list of qualities for the given channel for which there
	may be segments available. Returns empty list on non-existent channels, etc."""
	path = os.path.join(
		app.static_folder,
		channel,
	)
	return json.dumps(listdir(path, error=False))

@app.route('/files/<channel>/<quality>')
@request_stats
@has_path_args
def list_hours(channel, quality):
	"""Returns a JSON list of hours for the given channel and quality for which
	there may be segments available. Returns empty list on non-existent
	channels, etc.
	"""
	path = os.path.join(
		app.static_folder,
		channel,
		quality,
	)
	return json.dumps(listdir(path, error=False))


@app.route('/files/<channel>/<quality>/<hour>')
@request_stats
@has_path_args
def list_segments(channel, quality, hour):
	"""Returns a JSON list of segment files for a given channel, quality and
	hour. Returns empty list on non-existant channels, etc.
	"""
	path = os.path.join(
		app.static_folder,
		channel,
		quality,
		hour,
	)
	return json.dumps(listdir(path, error=False))


def time_range_for_quality(channel, quality):
	"""Returns earliest and latest times that the given quality has segments for
	(up to hour resolution), or 404 if it doesn't exist / is empty."""
	hours = listdir(os.path.join(app.static_folder, channel, quality))
	if not hours:
		abort(404)
	first, last = min(hours), max(hours)
	# note last hour parses to _start_ of that hour, so we add 1h to go to end of that hour
	def parse_hour(s):
		return datetime.datetime.strptime(s, "%Y-%m-%dT%H")
	return parse_hour(first), parse_hour(last) + datetime.timedelta(hours=1)


@app.route('/playlist/<channel>.m3u8')
@request_stats
@has_path_args
def generate_master_playlist(channel):
	"""Returns a HLS master playlist for the given channel.
	Takes optional params:
		start, end: The time to begin and end the stream at.
			See generate_media_playlist for details.
	"""
	start = dateutil.parse_utc_only(request.args['start']) if 'start' in request.args else None
	end = dateutil.parse_utc_only(request.args['end']) if 'end' in request.args else None
	qualities = listdir(os.path.join(app.static_folder, channel))

	playlists = {}
	for quality in qualities:
		# If start or end are given, try to restrict offered qualities to ones which exist for that
		# time range.
		if start is not None or end is not None:
			first, last = time_range_for_quality(channel, quality)
			if start is not None and last < start:
				continue # last time for quality is before our start time, don't offer quality
			if end is not None and end < first:
				continue # our end time is before first time for quality, don't offer quality
		playlists[quality] = url_for(
			'generate_media_playlist', channel=channel, quality=quality, **request.args
		)

	return generate_hls.generate_master(playlists)


@app.route('/playlist/<channel>/<quality>.m3u8')
@request_stats
@has_path_args
def generate_media_playlist(channel, quality):
	"""Returns a HLS media playlist for the given channel and quality.
	Takes optional params:
		start, end: The time to begin and end the stream at.
			Must be in ISO 8601 format (ie. yyyy-mm-ddTHH:MM:SS) and UTC.
			If not given, effectively means "infinity", ie. no start means
			any time ago, no end means any time in the future.
	Note that because it returns segments _covering_ that range, the playlist
	may start slightly before and end slightly after the given times.
	"""

	hours_path = os.path.join(app.static_folder, channel, quality)
	if not os.path.isdir(hours_path):
		abort(404)

	start = dateutil.parse_utc_only(request.args['start']) if 'start' in request.args else None
	end = dateutil.parse_utc_only(request.args['end']) if 'end' in request.args else None
	if start is None or end is None:
		# If start or end are not given, use the earliest/latest time available
		first, last = time_range_for_quality(channel, quality)
		if start is None:
			start = first
		if end is None:
			end = last

	# get_best_segments requires start be before end, special case that as no segments
	# (not an error because someone might ask for a specific start, no end, but we ended up with
	# end before start because that's the latest time we have)
	if start < end:
		segments = get_best_segments(hours_path, start, end)
	else:
		# Note the None to indicate there was a "hole" at both start and end
		segments = [None]

	return generate_hls.generate_media(segments, os.path.join(app.static_url_path, channel, quality))


@app.route('/cut/<channel>/<quality>.ts')
@request_stats
@has_path_args
def cut(channel, quality):
	"""Return a MPEGTS video file covering the exact timestamp range.
	Params:
		start, end: The start and end times, down to the millisecond.
			Must be in ISO 8601 format (ie. yyyy-mm-ddTHH:MM:SS) and UTC.
			If not given (and ranges not given), will use the earliest/latest data available.
		range: A pair "START,END" which are formatted as per start and end args.
			Overrides "start" and "end" options.
			This option may be given multiple times.
			The final video will consist of all the ranges cut back to back,
			in the order given, with hard cuts between each range.
		allow_holes: Optional, default false. If false, errors out with a 406 Not Acceptable
			if any holes are detected, rather than producing a video with missing parts.
			Set to true by passing "true" (case insensitive).
			Even if holes are allowed, a 406 may result if the resulting video (or any individual
			range) would be empty.
		type: One of:
			"rough": A direct concat, like a fast cut but without any ffmpeg.
				It may extend beyond the requested start and end times by a few seconds.
			"fast": Very fast but with minor artifacting where the first and last segments join
				the other segments.
			"mpegts": A full cut to a streamable mpegts format. This consumes signifigant server
				resources, so please use sparingly.
	"""
	if 'range' in request.args:
		parts = [part.split(',') for part in request.args.getlist('range')]
		ranges = [
			(dateutil.parse_utc_only(start), dateutil.parse_utc_only(end))
			for start, end in parts
		]
	else:
		start = dateutil.parse_utc_only(request.args['start']) if 'start' in request.args else None
		end = dateutil.parse_utc_only(request.args['end']) if 'end' in request.args else None
		if start is None or end is None:
			# If start or end are not given, use the earliest/latest time available
			first, last = time_range_for_quality(channel, quality)
			if start is None:
				start = first
			if end is None:
				end = last
		ranges = [(start, end)]

	for start, end in ranges:
		if end <= start:
			return "Ends must be after starts", 400

	allow_holes = request.args.get('allow_holes', 'false').lower()
	if allow_holes not in ["true", "false"]:
		return "allow_holes must be one of: true, false", 400
	allow_holes = (allow_holes == "true")

	hours_path = os.path.join(app.static_folder, channel, quality)
	if not os.path.isdir(hours_path):
		abort(404)

	segment_ranges = []
	for start, end in ranges:
		segments = get_best_segments(hours_path, start, end)
		if not allow_holes and None in segments:
			return "Requested time range contains holes or is incomplete.", 406
		if not any(segment is not None for segment in segments):
			return "We have no content available within the requested time range.", 406
		segment_ranges.append(segments)

	type = request.args.get('type', 'fast')
	if type == 'rough':
		return Response(rough_cut_segments(segment_ranges, ranges), mimetype='video/MP2T')
	elif type == 'fast':
		return Response(fast_cut_segments(segment_ranges, ranges), mimetype='video/MP2T')
	elif type in ('mpegts', 'mp4'):
		if type == 'mp4':
			return "mp4 type has been disabled due to the load it causes", 400
		# encode as high-quality, without wasting too much cpu on encoding
		stream, muxer, mimetype = (True, 'mpegts', 'video/MP2T') if type == 'mpegts' else (False, 'mp4', 'video/mp4')
		encoding_args = ['-c:v', 'libx264', '-preset', 'ultrafast', '-crf', '0', '-f', muxer]
		if len(ranges) > 1:
			return "full cut does not support multiple ranges at this time", 400
		start, end = ranges[0]
		return Response(full_cut_segments(segment_ranges[0], start, end, encoding_args, stream=stream), mimetype=mimetype)
	else:
		return "Unknown type {!r}".format(type), 400


@app.route('/waveform/<channel>/<quality>.png')
@request_stats
@has_path_args
def generate_waveform(channel, quality):
	"""
	Returns a PNG image showing the audio waveform over the requested time period.
	Params:
		start, end: Required. The start and end times.
			Must be in ISO 8601 format (ie. yyyy-mm-ddTHH:MM:SS) and UTC.
			The returned image may extend beyond the requested start and end times by a few seconds.
		size: The image size to render in form WIDTHxHEIGHT. Default 1024x64.
	"""
	start = dateutil.parse_utc_only(request.args['start'])
	end = dateutil.parse_utc_only(request.args['end'])
	if end <= start:
		return "End must be after start", 400

	if end - start > datetime.timedelta(hours=6):
		return "Range may not be longer than 6 hours", 400

	size = request.args.get('size', '1024x64')
	try:
		width, height = map(int, size.split('x'))
	except ValueError:
		return "Invalid size", 400
	if not ((0 < width <= 4096) and (0 < height <= 4096)):
		return "Image size must be between 1x1 and 4096x4096", 400

	hours_path = os.path.join(app.static_folder, channel, quality)
	if not os.path.isdir(hours_path):
		abort(404)

	segments = get_best_segments(hours_path, start, end)
	if not any(segment is not None for segment in segments):
		return "We have no content available within the requested time range.", 406

	return Response(render_segments_waveform(segments, (width, height)), mimetype='image/png')


@app.route('/generate_videos/<channel>/<quality>', methods=['POST'])
@request_stats
@has_path_args
def generate_videos(channel, quality):
	"""
	Takes a JSON body {name: [start, end]} where start and end are timestamps.
	Creates files CHANNEL_QUALITY_NAME_N.mkv for each contiguous range of segments
	in that hour range (ie. split at holes) and saves them in the segments directory.
	"""
	videos = request.json

	for name, (start, end) in videos.items():
		start = dateutil.parse_utc_only(start)
		end = dateutil.parse_utc_only(end)

		# protect against directory traversal
		if "/" in name:
			return "Name cannot contain /", 400

		if end <= start:
			return "End must be after start", 400

		hours_path = os.path.join(app.static_folder, channel, quality)
		if not os.path.isdir(hours_path):
			abort(404)

		segments = get_best_segments(hours_path, start, end)
		contiguous = []
		n = 0
		logging.info("Generating contiguous videos {!r} for {}/{} from {} to {}".format(
			name, channel, quality, start, end,
		))

		def write_file(segments, n):
			output_name = os.path.join(app.static_folder, '{}_{}_{}_{}.mkv'.format(channel, quality, name, n))
			if os.path.exists(output_name):
				logging.info("Skipping generating hours video - already exists")
				return
			temp_name = os.path.join(app.static_folder, "temp-{}.mkv".format(uuid4()))
			args = [
				'ffmpeg',
				'-hide_banner', '-loglevel', 'error', # suppress noisy output
				'-i', '-',
				'-c', 'copy',
				temp_name,
			]
			logging.info("Generating video with args: {}".format(" ".join(args)))
			proc = None
			try:
				proc = subprocess.Popen(args, stdin=subprocess.PIPE)
				# feed_input will write all the segments and close stdin
				feed_input(segments, proc.stdin)
				# now wait for it to finish and check errors
				if proc.wait() != 0:
					raise Exception("ffmpeg exited {}".format(proc.returncode))
				os.rename(temp_name, output_name)
			finally:
				if os.path.exists(temp_name):
					os.remove(temp_name)

		for segment in segments:
			if segment is not None:
				contiguous.append(segment)
				continue
			if contiguous:
				write_file(contiguous, n)
				n += 1
				contiguous = []
		if contiguous:
			write_file(contiguous, n)

	return ''


def main(host='0.0.0.0', port=8000, base_dir='.', backdoor_port=0):
	app.static_folder = base_dir
	server = WSGIServer((host, port), cors(app))

	PromLogCountsHandler.install()
	install_stacksampler()

	if backdoor_port:
		gevent.backdoor.BackdoorServer(('127.0.0.1', backdoor_port), locals=locals()).start()

	serve_with_graceful_shutdown(server)
