#!/usr/bin/env bash
set -euo pipefail

# --- Configuration (from environment variables with defaults) ---
URLS="${URLS:-}"
URLS_FILE="${URLS_FILE:-/app/urls.txt}"
LOOP="${LOOP:-1}"
PROTOCOL="${PROTOCOL:-udp}"   # udp | rtp | rtmp | icecast
TARGET="${TARGET:-udp://239.0.0.1:1234?ttl=16}"
CODEC="${CODEC:-aac}"
COPY_CODEC_WHEN_POSSIBLE="${COPY_CODEC_WHEN_POSSIBLE:-1}"
BITRATE="${BITRATE:-160k}"
SAMPLE_RATE="${SAMPLE_RATE:-48000}"
FFMPEG_EXTRA_ARGS="${FFMPEG_EXTRA_ARGS:-}"

# --- Globals ---
PID_FILE="/tmp/ffmpeg.pid"
PLAYLIST_FILE="/tmp/playlist.txt"
declare -a URL_LIST=()
declare -a CODEC_ARGS=()
declare -a OUTPUT_FORMAT_ARGS=()

# --- Functions ---

# Graceful cleanup on exit
cleanup() {
    rm -f "$PID_FILE" "$PLAYLIST_FILE"
}
trap cleanup EXIT

# Populates URL_LIST from environment or file
get_urls() {
    local raw_urls=()
    if [[ -n "$URLS" ]]; then
        IFS=$'\n,' read -r -d '' -a raw_urls < <(printf '%s\0' "$URLS")
        elif [[ -f "$URLS_FILE" ]]; then
        mapfile -t raw_urls < "$URLS_FILE"
    fi
    
    # Trim whitespace and remove empty entries
    for u in "${raw_urls[@]:-}"; do
        u="$(echo "$u" | sed 's/^[[:space:]]*//; s/[[:space:]]*$//')"
        [[ -n "$u" ]] && URL_LIST+=("$u")
    done
}

# Creates the playlist file for ffmpeg's concat demuxer
build_playlist() {
    : > "$PLAYLIST_FILE"
    for u in "${URL_LIST[@]}"; do
        printf "file '%s'\n" "$u" >> "$PLAYLIST_FILE"
    done
}

# Sets OUTPUT_FORMAT_ARGS based on the streaming protocol
get_output_format_args() {
    case "$PROTOCOL" in
        udp)     OUTPUT_FORMAT_ARGS=(-f mpegts) ;;
        rtp)     OUTPUT_FORMAT_ARGS=(-f rtp) ;;
        rtmp)    OUTPUT_FORMAT_ARGS=(-f flv) ;;
        icecast) OUTPUT_FORMAT_ARGS=(-content_type audio/mpeg -f mp3) ;;
        *) echo "Unsupported PROTOCOL: $PROTOCOL" >&2; exit 2 ;;
    esac
}

# Sets CODEC_ARGS for copying or re-encoding
get_codec_args() {
    if [[ "$COPY_CODEC_WHEN_POSSIBLE" == "1" && "$PROTOCOL" != "icecast" ]]; then
        CODEC_ARGS=(-c:a copy)
        elif [[ "$PROTOCOL" == "icecast" ]]; then
        # Icecast typically requires MP3
        CODEC_ARGS=(-c:a libmp3lame -b:a "$BITRATE" -ar "$SAMPLE_RATE" -ac 2)
    else
        # Default re-encode
        CODEC_ARGS=(-c:a "$CODEC" -b:a "$BITRATE" -ar "$SAMPLE_RATE" -ac 2)
    fi
}

# Runs a single ffmpeg instance
run_ffmpeg() {
    local proto_whitelist="file,crypto,data,subfile,http,https,tcp,tls,pipe"
    
    # Run in background to allow this script to wait and manage it
    ffmpeg -hide_banner -nostats -v info \
    -protocol_whitelist "$proto_whitelist" \
    -re -stream_loop -1 -f concat -safe 0 -i "$PLAYLIST_FILE" \
    -vn "${CODEC_ARGS[@]}" \
    "${OUTPUT_FORMAT_ARGS[@]}" \
    $FFMPEG_EXTRA_ARGS \
    "$TARGET" &
    
    echo $! > "$PID_FILE"
    wait $!
}

# --- Main Execution ---
main() {
    get_urls
    if [[ ${#URL_LIST[@]} -eq 0 ]]; then
        echo "No URLs provided. Set URLS env or mount a file at $URLS_FILE." >&2
        exit 1
    fi
    
    get_output_format_args
    get_codec_args
    build_playlist
    
    echo "Starting stream from ${#URL_LIST[@]} URL(s) → $PROTOCOL → $TARGET"
    
    if [[ "$LOOP" == "1" ]]; then
        while true; do
            set +e # Prevent exit on non-zero ffmpeg exit code
            run_ffmpeg
            local exit_code=$?
            set -e
            echo "FFmpeg exited with code $exit_code; restarting in 2s..."
            sleep 2
            # Rebuild playlist in case URLs have changed/expired
            build_playlist
        done
    else
        run_ffmpeg
    fi
}

main "$@"