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

media_root=${1:-data}

if ! command -v ffprobe >/dev/null 2>&1; then
    echo "ffprobe is required to validate media." >&2
    exit 2
fi

if [[ ! -d $media_root ]]; then
    printf 'Media directory does not exist: %s\n' "$media_root" >&2
    exit 2
fi

valid_count=0
invalid_count=0

validate_file() {
    local file=$1
    local format_name streams codec type attached_pic
    local video_count=0
    local audio_count=0
    local invalid_reason=

    if ! format_name=$(ffprobe -v error -show_entries format=format_name \
        -of default=noprint_wrappers=1:nokey=1 "$file"); then
        printf 'INVALID: %q: unreadable or corrupt MP4\n' "$file" >&2
        return 1
    fi

    if [[ ,$format_name, != *,mp4,* ]]; then
        printf 'INVALID: %q: expected an MP4 container, got %s\n' "$file" "$format_name" >&2
        return 1
    fi

    if ! streams=$(ffprobe -v error \
        -show_entries stream=codec_name,codec_type:stream_disposition=attached_pic \
        -of csv=p=0 "$file"); then
        printf 'INVALID: %q: unable to inspect streams\n' "$file" >&2
        return 1
    fi

    while IFS=, read -r codec type attached_pic; do
        case "$type" in
            video)
                if [[ $attached_pic == 1 ]]; then
                    continue
                fi
                if [[ $codec != h264 ]]; then
                    invalid_reason="unsupported video codec $codec"
                fi
                ((video_count += 1))
                ;;
            audio)
                if [[ $codec != aac ]]; then
                    invalid_reason="unsupported audio codec $codec"
                fi
                ((audio_count += 1))
                ;;
            *)
                invalid_reason="unsupported $type track ($codec)"
                ;;
        esac
    done <<< "$streams"

    if [[ -n $invalid_reason ]]; then
        printf 'INVALID: %q: %s\n' "$file" "$invalid_reason" >&2
        return 1
    fi

    if ((video_count != 1 || audio_count != 1)); then
        printf 'INVALID: %q: expected one H.264 video and one AAC audio track; found %d video and %d audio\n' \
            "$file" "$video_count" "$audio_count" >&2
        return 1
    fi

    printf 'VALID: %s\n' "$file"
}

while IFS= read -r -d '' file; do
    if validate_file "$file"; then
        ((valid_count += 1))
    else
        ((invalid_count += 1))
    fi
done < <(find "$media_root" -type f -iname '*.mp4' -print0)

if ((valid_count == 0)); then
    echo "No valid MP4 files were found." >&2
    exit 1
fi

if ((invalid_count > 0)); then
    printf 'Validation failed: %d valid, %d invalid file(s).\n' "$valid_count" "$invalid_count" >&2
    exit 1
fi

printf 'Validation passed: %d MP4 file(s).\n' "$valid_count"