#!/usr/bin/env bash
# -----------------------------------------------------------------------------
# Title:     flac2m4a
# Purpose:   Comprehensive flac to m4a auto-converter
# Version:   1.0.0
# Developer: h@x
# -----------------------------------------------------------------------------

set -euo pipefail
trap 'echo "✗ ERROR on line $LINENO (exit code $?): ${BASH_COMMAND}" >&2' ERR
IFS=$'\n\t'

# === Input & output directories ===
SRC_DIR="${1:-.}"
DST_DIR="${2:-./m4a_output}"
[[ -d "$SRC_DIR" ]] || {
  echo "ERROR: Source directory '$SRC_DIR' not found." >&2
  exit 1
}
mkdir -p "$DST_DIR"

# === FFmpeg capability check ===
if ! ffmpeg -hide_banner -muxers 2>/dev/null | grep -qw mov; then
  echo "ERROR: FFmpeg build lacks the MP4/mov muxer required for .m4a outputs." >&2
  exit 1
fi

# === Codec selection ===
declare -a CODEC_OPTS
if ffmpeg -hide_banner -encoders 2>/dev/null | grep -qw libfdk_aac; then
  CODEC_OPTS=( -c:a libfdk_aac -profile:a aac_he_v2 -cutoff 18000 -b:a 256k )
  echo "INFO: Using libfdk_aac HE-AAC v2 @256 kbps." >&2
else
  CODEC_OPTS=( -c:a aac -b:a 256k )
  echo "WARNING: Falling back to native AAC @256 kbps." >&2
fi

declare -a META_OPTS=(
  -map_metadata 0
  -id3v2_version 3
  -write_id3v1 1
  -metadata:s:a encoder="ffmpeg/${CODEC_OPTS[1]}"
)
declare -a FFMPEG_OPTS=( -hide_banner -loglevel error -nostdin -n )

# === Discover .flac files ===
mapfile -d '' files < <(find "$SRC_DIR" -type f -iname '*.flac' -print0)
TOTAL=${#files[@]}

(( TOTAL > 0 )) || {
  echo "Nothing to do: no .flac files found under '$SRC_DIR'." >&2
  exit 0
}
echo "FOUND: $TOTAL .flac file(s) to process." >&2

# === Progress-bar initialization ===
BAR_WIDTH=40
COUNT=0
LAST_PCT=-1

# pre-fill bar with dots, print initial line
empty_bar=$(printf '%*s' "$BAR_WIDTH" '' | tr ' ' '.')
printf "Progress: [%-${BAR_WIDTH}s]   0%% (%d/%d)\n" \
  "$empty_bar" 0 "$TOTAL" >&2

# === Conversion loop with ANSI overwrite ===
##declare -a SKIPPED CONVERTED
##declare -A FAILED

declare -a SKIPPED=()
declare -a CONVERTED=()
declare -A FAILED=()

for SRC_FILE in "${files[@]}"; do
  (( COUNT += 1 ))
  REL_PATH="${SRC_FILE#"$SRC_DIR"/}"
  DST_FILE="$DST_DIR/${REL_PATH%.flac}.m4a"
  mkdir -p "$(dirname "$DST_FILE")"

  # calculate and render updated bar if % changed
  PCT=$(( COUNT * 100 / TOTAL ))
  if (( PCT != LAST_PCT )); then
    LAST_PCT=$PCT
    filled=$(( COUNT * BAR_WIDTH / TOTAL ))
    fbar=$(printf '%*s' "$filled" '' | tr ' ' '#')
    ebar=$(printf '%*s' "$(( BAR_WIDTH - filled ))" '' | tr ' ' '.')
    # move cursor up one line, carriage-return, then overwrite
    printf "\033[1A\rProgress: [%s%s] %3d%% (%d/%d)\n" \
      "$fbar" "$ebar" "$PCT" "$COUNT" "$TOTAL" >&2
  fi

  # skip or convert
  if [[ -f "$DST_FILE" ]]; then
    SKIPPED+=("$REL_PATH")
  else
    if ffmpeg "${FFMPEG_OPTS[@]}" -i "$SRC_FILE" \
         "${CODEC_OPTS[@]}" -vn "${META_OPTS[@]}" -f ipod "$DST_FILE"; then
      CONVERTED+=("$REL_PATH")
    else
      FAILED["$REL_PATH"]=1
    fi
  fi
done

# === Summary ===
echo >&2
printf "========== SUMMARY ==========\n" >&2

printf "Skipped (already present): %d\n" "${#SKIPPED[@]}" >&2
for f in "${SKIPPED[@]}"; do printf " • %s\n" "$f"; done >&2

echo >&2
printf "Converted: %d\n" "${#CONVERTED[@]}" >&2
for f in "${CONVERTED[@]}"; do printf " • %s\n" "$f"; done >&2

echo >&2
printf "Failed: %d\n" "${#FAILED[@]}" >&2
for f in "${!FAILED[@]}"; do printf " • %s\n" "$f"; done >&2

echo >&2
printf "Output directory: '%s'\n" "$DST_DIR" >&2
echo "=============================" >&2

# appropriate exit code
(( ${#FAILED[@]} )) && exit 2 || exit 0