#!/usr/bin/env bash
# to_mp3.sh — Convert .m4a and .wav files to .mp3
#
# Usage:
#   ./to_mp3.sh <file_or_folder> [options]
#
# Options:
#   --quality N    VBR quality 0-9 (default: 2 ≈ 190kbps; lower = better)
#   --bitrate N    CBR bitrate e.g. 192k (overrides --quality)
#   --replace      Delete originals after successful conversion
#   --dry-run      Show what would be converted without doing anything
#
# Examples:
#   ./to_mp3.sh recordings/
#   ./to_mp3.sh interview.m4a
#   ./to_mp3.sh recordings/ --replace
#   ./to_mp3.sh recordings/ --bitrate 128k

set -euo pipefail

QUALITY=2
BITRATE=""
REPLACE=false
DRY_RUN=false
TARGET=""

# Parse arguments
while [[ $# -gt 0 ]]; do
    case "$1" in
        --quality)  QUALITY="$2";  shift 2 ;;
        --bitrate)  BITRATE="$2";  shift 2 ;;
        --replace)  REPLACE=true;  shift ;;
        --dry-run)  DRY_RUN=true;  shift ;;
        -*)         echo "Unknown option: $1" >&2; exit 1 ;;
        *)          TARGET="$1";   shift ;;
    esac
done

if [[ -z "$TARGET" ]]; then
    echo "Usage: $(basename "$0") <file_or_folder> [--quality N] [--bitrate N] [--replace] [--dry-run]"
    exit 1
fi

if ! command -v ffmpeg &>/dev/null; then
    echo "Error: ffmpeg not found." >&2
    exit 1
fi

# Collect files
files=()
if [[ -f "$TARGET" ]]; then
    files=("$TARGET")
elif [[ -d "$TARGET" ]]; then
    while IFS= read -r -d '' f; do
        files+=("$f")
    done < <(find "$TARGET" -maxdepth 1 -type f \( -iname "*.m4a" -o -iname "*.wav" \) -print0 | sort -z)
else
    echo "Error: '$TARGET' is not a file or directory." >&2
    exit 1
fi

if [[ ${#files[@]} -eq 0 ]]; then
    echo "No .m4a or .wav files found in: $TARGET"
    exit 0
fi

# Build audio quality flags
if [[ -n "$BITRATE" ]]; then
    audio_flags=(-b:a "$BITRATE")
    quality_desc="CBR ${BITRATE}"
else
    audio_flags=(-q:a "$QUALITY")
    quality_desc="VBR quality ${QUALITY}"
fi

echo "Converting ${#files[@]} file(s) to MP3 (${quality_desc})"
[[ "$REPLACE" == true ]] && echo "  Originals will be deleted after conversion."
[[ "$DRY_RUN" == true ]] && echo "  Dry-run mode — no files will be written."
echo ""

converted=0
skipped=0
errors=0

for src in "${files[@]}"; do
    out="${src%.*}.mp3"

    if [[ -f "$out" && "$DRY_RUN" == false ]]; then
        echo "  $(basename "$src"): output already exists, skipping"
        ((skipped++)) || true
        continue
    fi

    size_mb=$(( $(stat -f%z "$src" 2>/dev/null || stat -c%s "$src") / 1048576 ))
    printf "  %-40s (%d MB)" "$(basename "$src")" "$size_mb"

    if [[ "$DRY_RUN" == true ]]; then
        echo "  [dry-run] → $(basename "$out")"
        continue
    fi

    if ffmpeg -i "$src" -vn "${audio_flags[@]}" -y "$out" -loglevel error; then
        out_kb=$(( $(stat -f%z "$out" 2>/dev/null || stat -c%s "$out") / 1024 ))
        echo "  → $(basename "$out") (${out_kb} KB)"
        ((converted++)) || true
        if [[ "$REPLACE" == true ]]; then
            rm "$src"
        fi
    else
        echo "  ERROR"
        ((errors++)) || true
        [[ -f "$out" ]] && rm "$out"
    fi
done

echo ""
echo "Done: ${converted} converted, ${skipped} skipped, ${errors} errors."