using System;
using System.Globalization;

namespace Paca.Core;

/// <summary>
/// Image format for extracted video poster thumbnails.
/// </summary>
public enum PosterFormat
{
    Jpeg,
    Png,
    WebP
}

/// <summary>
/// Specification for capturing high-quality single-frame video posters.
/// </summary>
public sealed record PosterExtractionSpec(
    double SeekTimeSec,
    int Width,
    int Height,
    PosterFormat Format,
    int Quality = 85
);

/// <summary>
/// Video poster frame extractor generating intelligent seek points and scaling pipelines.
/// </summary>
public static class VideoPosterExtractor
{
    /// <summary>
    /// 배터리 절전 모드 활성화 시 CPU 집약적인 썸네일/포스터 프레임 추출을 일시 유예할지 판정합니다.
    /// </summary>
    public static bool ShouldDeferExtraction(Platform.BatterySaverPowerManager? powerManager) =>
        powerManager?.ShouldDeferBackgroundProcessing ?? false;

    /// <summary>
    /// Computes optimal frame timestamp skipping black intro/logos while avoiding spoilers.
    /// </summary>
    public static double CalculateOptimalSeekTime(double totalDurationSec)
    {
        if (totalDurationSec <= 0)
            return 0.0;

        if (totalDurationSec < 10.0)
            return Math.Min(1.0, totalDurationSec * 0.5);

        return Math.Min(10.0, totalDurationSec * 0.1);
    }

    /// <summary>
    /// Builds aspect-ratio preserving downscale filter.
    /// </summary>
    public static string BuildScalingFilter(PosterExtractionSpec spec)
    {
        return $"scale={spec.Width}:{spec.Height}:force_original_aspect_ratio=decrease";
    }

    /// <summary>
    /// Builds full ffmpeg command line for single-frame thumbnail extraction.
    /// </summary>
    public static string BuildPosterCommandLine(
        string inputVideoPath,
        string outputImagePath,
        PosterExtractionSpec spec)
    {
        if (string.IsNullOrWhiteSpace(inputVideoPath)) throw new ArgumentException("Input video path cannot be null or whitespace.", nameof(inputVideoPath));
        if (string.IsNullOrWhiteSpace(outputImagePath)) throw new ArgumentException("Output image path cannot be null or whitespace.", nameof(outputImagePath));

        var cleanIn = inputVideoPath.Trim().Replace("\"", "");
        var cleanOut = outputImagePath.Trim().Replace("\"", "");

        if (string.Equals(System.IO.Path.GetFullPath(cleanIn), System.IO.Path.GetFullPath(cleanOut), StringComparison.OrdinalIgnoreCase))
            throw new InvalidOperationException("입력 파일과 출력 파일 경로가 동일할 수 없습니다.");

        var seekStr = spec.SeekTimeSec.ToString("F2", CultureInfo.InvariantCulture);
        var scaleFilter = BuildScalingFilter(spec);

        var encoderFlags = spec.Format switch
        {
            PosterFormat.WebP => $"-c:v libwebp -quality {spec.Quality}",
            PosterFormat.Png => "-c:v png",
            _ => "-q:v 2"
        };

        return $"-ss {seekStr} -i \"{cleanIn}\" -vframes 1 -vf \"{scaleFilter}\" {encoderFlags} \"{cleanOut}\" -y";
    }
}