#!/bin/bash
# MIT GUM-Darstellung
# Abhängigkeiten: sudo apt-get install ffmpeg id3v2
#                 https://github.com/charmbracelet/gum

track=1

for i in *.m4b; do
    name="${i%.m4b}"

    ffmpeg -i "$i" 2> tmp.txt
    chapter_count=$(grep -c "Chapter #" tmp.txt || true)

    if [[ "$chapter_count" -gt 0 ]]; then
        title=$(basename "$(pwd)")
        full_file_path="${name}.mp3"

        gum spin --title "Konvertiere: $name ..." -- \
            ffmpeg -i "$i" \
                -acodec libmp3lame \
                -b:a 128k \
                -map_metadata 0 \
                -id3v2_version 3 \
                "$full_file_path"

        echo "Splitte nach Kapiteln: $name"
        while read -r first _ _ start _ end; do
            if [[ "${first}" = "Chapter" ]]; then
                read
                read _ _ chapter
                track_padded=$(printf "%02d" "$track")
                base_name="${title} - ${track_padded} - ${chapter}"
                chapter_file="${base_name}.mp3"
                suffix=1
                while [[ -e "$chapter_file" ]]; do
                    chapter_file="${base_name}_(${suffix}).mp3"
                    suffix=$((suffix + 1))
                done
                echo "  -> $chapter_file"
                </dev/null ffmpeg -loglevel error -stats \
                    -i "$full_file_path" \
                    -ss "${start%?}" \
                    -to "$end" \
                    -codec:a copy \
                    -metadata title="$chapter" \
                    -metadata album="$title" \
                    -metadata track="$track" \
                    "$chapter_file"
                track=$((track + 1))
            fi
        done < tmp.txt

        rm "$full_file_path"
    else
        gum spin --title "Konvertiere: $name ..." -- \
            ffmpeg -i "$i" \
                -acodec libmp3lame \
                -b:a 128k \
                -map_metadata 0 \
                -id3v2_version 3 \
                "${name}.mp3"

        echo "  -> ${name}.mp3"
        track=$((track + 1))
    fi

    rm -f tmp.txt
done

echo "==> Fertig."