#!/usr/bin/env bash

set -euo pipefail

root="$1"

find "$root" -type f \( \
    -iname '*.m4b' -o \
    -iname '*.m4a' -o \
    -iname '*.mp3' -o \
    -iname '*.aac' -o \
    -iname '*.flac' -o \
    -iname '*.ogg' -o \
    -iname '*.opus' -o \
    -iname '*.wav' -o \
    -iname '*.wma' -o \
    -iname '*.mp4' \
\) -print0 |
while IFS= read -r -d '' file; do
    rel="${file#"$root"/}"

    # Only process: book/file
    # Leave already organized: author/book/file
    [[ "$rel" == */*/* ]] && continue
    [[ "$rel" != */* ]] && continue

    book="${rel%%/*}"
    name="${rel#*/}"

    artist="$(ffprobe -v error \
        -show_entries format_tags=artist \
        -of default=noprint_wrappers=1:nokey=1 \
        "$file" 2>/dev/null || true)"

    # Trim whitespace
    artist="$(printf '%s' "$artist" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')"

    # No artist tag -> skip
    [[ -z "$artist" ]] && continue

    dest="$root/$artist/$book"

    mkdir -p -- "$dest"

    echo "Moving: $rel"
    echo "     -> $artist/$book/$name"

    mv -- "$file" "$dest/$name"
done


# Remove empty directories
find "$root" -depth -type d -empty -delete