#!/bin/bash

# musidl - download music from YouTube
# Copyright (C) 2021 TriMill
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU 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 General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.


# check to make sure all commands are available before running
if ! (command -v "youtube-dl" && command -v "jq" && command -v "id3v2") &>/dev/null; then
    >&2 echo "Missing dependencies."
    exit 1
fi

# this is printed on -h/--help
helpmsg="Usage: musidl [options]... [url]... (-- [youtube-dl options])  
Download music from YouTube using youtube-dl and add id3v2 metadata automatically

Options:
 -h --help              Print this message and exit
 -v --version           Print the version and exit
 -q --quiet             Only print errors
 -f --format <fmt>      The audio format to use (default: mp3)
 -a --artist <name>     Set the artist (default: detect from YouTube)
 -A --album  <name>     Set the album title (default: detect from YouTube)
 -t --song   <name>     Set the song title (default: detect from YouTube)
 -g --genre  <name>     Set the genre (default: none)
 -y --year   <year>     Set the year (default: detect from YouTube)
 -T --track  <track>    Set the track (default: detect from playlist, otherwise none)
 -s --show              Print information to stdout instead of downloading to file

Any arguments after '--' will be sent to youtube-dl directly. These are not officially
supported and some may cause problems."

versionmsg="0.0.1"

# Add a prefix to error messages
function printStderr {
    read -r input
    [ -n "$input" ] && >&2 echo "[$1] $input" 
}

urls=() # The list of URLs to download
arg_format="mp3" # The file format (-f/--format)
# Process the arguments
while [[ $# -gt 0 ]]; do
  case "$1" in
    -h|--help)
      echo "$helpmsg"; exit 0 ;;
    -v|--version)
      echo "musidl $versionmsg"; exit 0 ;;
    -q|--quiet)
      quiet="true"; shift 1 ;;
    -f|--format)
      arg_format="$2"; shift 2 ;;
    -a|--artist)
      i_artist="$2"; shift 2 ;;
    -A|--album)
      i_album="$2"; shift 2 ;;
    -t|--song)
      i_song="$2"; shift 2 ;;
    -g|--genre)
      genre="$2"; shift 2 ;;
    -y|--year)
      i_year="$2"; shift 2 ;;
    -T|--track)
      i_track="$2"; shift 2 ;;
    -s|--show)
      arg_show="true"; shift ;;
    --)
      shift; break ;;
    *)
      urls+=("$1"); shift ;;
  esac
done

# Exit if no URLs are given
[ ${#urls[@]} -eq 0 ] && >&2 echo "[musidl] no URLs provided. Run '$0 --help' for help." && exit 1

ytdl_args=( "$@" )

# Download metadata from all the URLs
[ -z "$quiet" ] && echo "[musidl] downloading data..."
data="$(youtube-dl -j "${ytdl_args[@]}" "${urls[@]}" 2> >(printStderr "youtube-dl"))"
[ -z "$data" ] && echo "[musidl] youtube-dl returned nothing, exiting" | printStderr "musidl" && exit 1

# Create a temporary file (this will be used later)
tmpfile="$(mktemp)"

IFS=$'\n'
# Run for each video to download
for line in $data; do
    # Use jq to extract data from the metadata. The following options are considered in order:
    # Artist: artist, channel name
    # Album: album, playlist name, none
    # Song name: track, video title
    # Year: release year, upload date
    # Track number: playlist index, none
    readarray -t songdata <<< "$(echo "$line" | jq -r \
        'if .artist then .artist else .channel end, if .album then .album else if .playlist_title then .playlist_title else "" end end, if .track then .track else .title end, if .release_year then .release_year else .upload_date end, if .playlist_index then .playlist_index else "" end, .webpage_url' \
        2> >(printStderr "jq"))"

    [ "${#songdata[@]}" -eq 0 ] && >&2 echo "[musidl] could not parse JSON, skipping" && continue

    # If arguments are set manually prefer them, otherwise use ones from YouTube
    if [ -n "$i_artist" ]; then artist="$i_artist"; else
        artist="${songdata[0]}"
    fi
    if [ -n "$i_album" ]; then album="$i_album"; else
        album="${songdata[1]}"
    fi
    if [ -n "$i_song" ]; then song="$i_song"; else
        song="${songdata[2]}"
    fi
    if [ -n "$i_year" ]; then year="$i_year"; else
        year="$(echo "${songdata[3]}" | head -c 4)"
    fi
    if [ -n "$i_track" ]; then track="$i_track"; else
        track="${songdata[4]}"
    fi
    url="${songdata[5]}"

    # If -s/--show is passed, show the data and continue
    if [ -n "$arg_show" ]; then
        echo "URL: $url"
        [ -n "$artist" ] && echo "Artist: $artist"
        [ -n "$album" ] && echo "Album: $album"
        [ -n "$song" ] && echo "Song: $song"
        [ -n "$genre" ] && echo "Genre: $genre"
        [ -n "$year" ] && echo "Year: $year"
        [ -n "$track" ] && echo "Track: $track"
        continue
    fi

    [ -z "$quiet" ] && echo "[musidl] downloading $url"

    # Download the video,
    # Print all errors,
    # Find the filename and save it to a tempfile; add a prefix to the messages,
    # And only print messages if quiet is off
    stdbuf -o0 youtube-dl --no-progress --extract-audio --audio-format="$arg_format" "${ytdl_args[@]}" "$url" \
        2> >(printStderr "youtube-dl") \
        | stdbuf -o0 sed -e '/^\[ffmpeg\] Destination: /w '"$tmpfile" -e 's/^/[youtube-dl] /' \
        | ( if [ -z "$quiet" ]; then stdbuf -o0 cat; else cat > /dev/null; fi )                                 

    # Extract filename from the temporary file
    filename=$(cut -c 23- < "$tmpfile") 

    # use id3v2 to set each property on the file
    if [ -f "$filename" ]; then
        [ -n "$artist" ] && id3v2 --artist "$artist" "$filename"
        [ -n "$album" ] && id3v2 --album "$album" "$filename"
        [ -n "$song" ] && id3v2 --song "$song" "$filename"
        [ -n "$genre" ] && id3v2 --genre "$genre" "$filename"
        [ -n "$year" ] && id3v2 --year "$year" "$filename"
        [ -n "$track" ] && id3v2 --track "$track" "$filename"
        [ -z "$quiet" ] && echo "[musidl] finished with $filename"
    else
        >&2 echo "[musidl] an error occured during downloading, skipping..."
    fi
done

[ -z "$quiet" ] && echo "[musidl] cleaning up..."
# Delete the temporary file
rm "$tmpfile"