#!/bin/sh

# Copyright (c) 2023 Emma Tebibyte <emma@tebibyte.media>
# SPDX-License-Identifier: AGPL-3.0-or-later
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option) any
# later version.
# 
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License along
# with this program. If not, see https://www.gnu.org/licenses/.

set -e

add() { # adds a video to a playlist file
	while test -n "$2"; do
		if test -z "$(sed -n ";$1;p" "$2")"
		then
			printf "%s: %s: Video already in playlist.\n" "$argv0" "$1"
			exit
		else
			archive "$1"
			printf "%s\n" "$1" >> "$2"
		fi

		shift
	done
}

archive() { # archives a video to the Wayback Machine
	while test -n "$1"; do
		curl -s -d "url=$1" https://web.archive.org/{url} >/dev/null
		shift
	done
}

cache() { # cache the video title for faster retrieval
	while test -n "$1"; do
		grep "$1" "$cachefile" 2>/dev/null 1>&2 || printf '%s\n' \
			"$(yt-dlp -s "$1" --print "$FMT")" >>"$cachefile"
		shift
	done
}

clone() { # clones a YouTube playlist in m3u format
	yt-dlp --flat-playlist "$1" --print url > "$2.m3u"
	verify "$2.m3u"
}

music() { # downloads a video, splitting by chapter and only saving the audio
	while "$1"; do
		yt-dlp -vx --split-chapters -o \
			"chapter:%(fulltitle)s - %(section_number)s %(section_title)s.%(ext)s" \
			"$1" --audio-quality 0 >> log 2>&1
		shift
	done
}

pick() { # Pick a video to play from a list of videos
	while test -n "$1"; do
		for line in $(cat "$1"); do
			cache "$line"

			if test -z "$list"; then
				list="$(grep "$line" "$cachefile")"
			else
				list="$(printf '%s\n%s' "$list" "$(grep "$line" "$cachefile")")"
			fi
		done
		shift
	done

	chosen="$(printf '%s\n' "$list" | fzf | sed -e 's/.*\[//g' -e 's/\]//g')"
	test -n "$chosen" && mpv "$chosen"
}

play() { # play a playlist or video after caching its title
	while test -n "$1"; do
		cache "$1"
		mpv "$1"
		shift
	done
}

usage() {
	printf "Usage: %s %s\n" "$argv0" "$@" 1>&2
	exit 64 # sysexits.h(3) EX_USAGE
}

verify() { # replaces videos with archived versions if they are not available
	while test -n "$1"; do
		for video in $(cat "$1"); do
			# test for unavailability
			if test -n "$(yt-dlp -s "$video" 2>&1 \
				| sed -n -e '/Video unavailable/p' -e '/Private video/p' )"
			then
				printf "%s: %s: Video unavailable.\n" "$argv0" "$video" 1>&2

				wayback_url="$(curl -s "$WBAPI$video" \
					| jq .archived_snapshots.closest.url \
					| tr -d '"' | sed 's/^http:/https:/g')"

				if [ "$wayback_url" = "null" ]; then
					printf "%s: %s is not available on the Wayback Machine.\n" \
						"$argv0" "$video" 1>&2
					# replace the video link with a comment containing link
					content="$(sed "s;^$video;\# $video;g" "$1")"

					# write the new content buffer to the file
					printf '%s\n' "$content" > "$1"
				else
					printf "%s: %s: Replacing link with Wayback link.\n" \
						"$argv0" "$video" 1>&2

					content="$(sed "s;$video;$wayback_url;g" "$1")"
					printf '%s\n' "$content" >"$1"
					cache "$wayback_url"
				fi
			fi
		done

		shift
	done
}

argv0="$0"
com="$1"

cachefile="$XDG_CACHE_HOME/yt.cache"
FMT='%(title)s – %(channel)s (%(duration>%H:%M:%S)s) [%(webpage_url)s]'
WBAPI='https://archive.org/wayback/available?url='

for dep in \
	curl \
	fzf \
	jq \
	mpv \
	yt-dlp
do
	if ! command -v "$dep" >/dev/null
	then
		printf "%s: %s: Missing dependency." "$argv0" "$dep" 1>&2
		exit 69 # syexits.h(3) EX_UNAVAILABLE
	fi
done

case "$com" in
	add)
		shift 2 2>/dev/null || usage 'add uri file'
		add "$@"
		;;
	cache)
		shift 2>/dev/null || usage 'cache uri...'
		cache "$@"
		;;
	clone)
		shift 2 2>/dev/null || usage 'clone uri file'
		clone "$@"
		;;
	music)
		shift 1 2>/dev/null || usage 'music uri...'
		music "$@"
		;;
	pick)
		shift 1 2>/dev/null || usage 'pick file...'
		pick "$@"
		;;
	play)
		shift 1 2>/dev/null || usage 'uri...'
		play "$@"
		;;
	verify)
		shift 1 2>/dev/null || usage 'file...'
		verify "$@"
		;;
	*)
		usage 'add | clone | music | pick | play | verify'
		;;
esac