using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Text;
using EmbyToolbox.Models;

namespace EmbyToolbox.Services;

public sealed class MergeService
{
    private static readonly UTF8Encoding Utf8NoBom = new(encoderShouldEmitUTF8Identifier: false);
    private readonly Func<string?> _tempDirectoryProvider;
    private readonly LoggingService _logging;
    private readonly FfprobeService _ffprobeService;
    private readonly ChapterBuilderService _chapterBuilderService;

    public MergeService(
        LoggingService logging,
        FfprobeService ffprobeService,
        ChapterBuilderService chapterBuilderService,
        Func<string?>? tempDirectoryProvider = null)
    {
        _logging = logging;
        _ffprobeService = ffprobeService;
        _chapterBuilderService = chapterBuilderService;
        _tempDirectoryProvider = tempDirectoryProvider ?? (() => null);
    }

    public async Task MergeAsync(
        IReadOnlyList<MergeFileItem> orderedFiles,
        string outputPath,
        IProgress<int>? progress,
        CancellationToken cancellationToken)
    {
        if (orderedFiles.Count < 2)
        {
            throw new InvalidOperationException("Для объединения нужно минимум 2 файла.");
        }

        if (string.IsNullOrWhiteSpace(outputPath))
        {
            throw new InvalidOperationException("Не задан путь итогового файла.");
        }

        var configuredTempRoot = ResolveTempRoot();
        var tempDirectory = Path.Combine(configuredTempRoot, "Merge", Guid.NewGuid().ToString("N", CultureInfo.InvariantCulture));
        var tempOutputPath = Path.Combine(tempDirectory, $"{Path.GetFileNameWithoutExtension(outputPath)}.mkv");
        Directory.CreateDirectory(tempDirectory);

        try
        {
            _logging.Info($"объединение: подготовка файлов ({orderedFiles.Count}), temp={tempDirectory}", "merge");
            var durations = new List<double>(orderedFiles.Count);
            foreach (var file in orderedFiles)
            {
                durations.Add(await ResolveDurationSecondsAsync(file.FullPath, cancellationToken).ConfigureAwait(false));
            }

            var totalDurationMs = Math.Max(1.0, durations.Sum() * 1000.0);
            var chapters = orderedFiles.Select(f => f.PartName).ToList();
            var metadataText = _chapterBuilderService.BuildFfmetadata(chapters, durations);
            var concatListPath = Path.Combine(tempDirectory, "merge-list.txt");
            var metadataPath = Path.Combine(tempDirectory, "chapters.ffmeta");
            await File.WriteAllTextAsync(concatListPath, BuildConcatList(orderedFiles), Utf8NoBom, cancellationToken).ConfigureAwait(false);
            await File.WriteAllTextAsync(metadataPath, metadataText, Utf8NoBom, cancellationToken).ConfigureAwait(false);

            var ffmpegPath = Path.Combine(AppContext.BaseDirectory, "Tools", "ffmpeg.exe");
            if (!File.Exists(ffmpegPath))
            {
                throw new FileNotFoundException($"ffmpeg не найден: {ffmpegPath}");
            }

            var args = $"-hide_banner -y -progress pipe:1 -nostats -f concat -safe 0 -i \"{concatListPath}\" -i \"{metadataPath}\" -map 0 -map_metadata 1 -c copy \"{tempOutputPath}\"";
            _logging.Info($"объединение: запуск ffmpeg (temp output) -> {tempOutputPath}", "merge", command: $"{ffmpegPath} {args}");

            var runResult = await RunFfmpegAsync(ffmpegPath, args, totalDurationMs, progress, cancellationToken).ConfigureAwait(false);
            if (runResult.ExitCode != 0)
            {
                throw new InvalidOperationException($"ffmpeg завершился с кодом {runResult.ExitCode}: {runResult.StdErr}");
            }

            if (!File.Exists(tempOutputPath))
            {
                throw new IOException("Временный итоговый файл не был создан.");
            }

            progress?.Report(94);
            await MoveTempOutputToFinalPathAsync(tempOutputPath, outputPath, cancellationToken).ConfigureAwait(false);
            progress?.Report(98);
            _logging.Info($"объединение завершено успешно: {outputPath}", "merge");
            progress?.Report(100);
        }
        finally
        {
            try
            {
                if (Directory.Exists(tempDirectory))
                {
                    Directory.Delete(tempDirectory, recursive: true);
                }
            }
            catch
            {
                // ignore temp cleanup errors
            }
        }
    }

    private static Task MoveTempOutputToFinalPathAsync(string tempOutputPath, string finalOutputPath, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();
        Directory.CreateDirectory(Path.GetDirectoryName(finalOutputPath)!);

        if (File.Exists(finalOutputPath))
        {
            File.Delete(finalOutputPath);
        }

        File.Move(tempOutputPath, finalOutputPath);
        return Task.CompletedTask;
    }

    private string ResolveTempRoot()
    {
        var configured = _tempDirectoryProvider.Invoke();
        if (!string.IsNullOrWhiteSpace(configured))
        {
            return configured.Trim();
        }

        return Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "EmbyToolbox",
            "Temp");
    }

    private async Task<double> ResolveDurationSecondsAsync(string filePath, CancellationToken cancellationToken)
    {
        var probeResult = await _ffprobeService.AnalyzeAsync(filePath, cancellationToken).ConfigureAwait(false);
        if (!probeResult.IsSuccess)
        {
            throw new InvalidOperationException($"ffprobe не смог получить длительность для '{filePath}': {probeResult.Error}");
        }

        var parsed = MediaAnalysisParser.TryParse(probeResult.Json);
        var duration = parsed?.GetEffectiveDurationSeconds();
        if (duration is not { } d || d <= 0.001)
        {
            throw new InvalidOperationException($"Не удалось определить длительность файла: {filePath}");
        }

        return d;
    }

    private static string BuildConcatList(IEnumerable<MergeFileItem> files)
    {
        var sb = new StringBuilder();
        foreach (var file in files)
        {
            var escaped = file.FullPath.Replace("'", "'\\''", StringComparison.Ordinal);
            sb.Append("file '").Append(escaped).AppendLine("'");
        }

        return sb.ToString();
    }

    private static async Task<(int ExitCode, string StdErr)> RunFfmpegAsync(
        string executable,
        string arguments,
        double totalDurationMs,
        IProgress<int>? progress,
        CancellationToken cancellationToken)
    {
        var startInfo = new ProcessStartInfo
        {
            FileName = executable,
            Arguments = arguments,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true,
            StandardOutputEncoding = Encoding.UTF8,
            StandardErrorEncoding = Encoding.UTF8
        };

        using var process = new Process { StartInfo = startInfo };
        process.Start();
        var stderrTask = process.StandardError.ReadToEndAsync(cancellationToken);

        using var killRegistration = cancellationToken.Register(
            static state =>
            {
                try
                {
                    if (state is Process p && !p.HasExited)
                    {
                        p.Kill(entireProcessTree: true);
                    }
                }
                catch
                {
                    // ignore
                }
            },
            process,
            useSynchronizationContext: false);

        string? line;
        while ((line = await process.StandardOutput.ReadLineAsync(cancellationToken).ConfigureAwait(false)) is not null)
        {
            if (!line.StartsWith("out_time_ms=", StringComparison.Ordinal))
            {
                continue;
            }

            var raw = line["out_time_ms=".Length..];
            if (!long.TryParse(raw, NumberStyles.Integer, CultureInfo.InvariantCulture, out var outTimeMicro))
            {
                continue;
            }

            var percent = (int)Math.Clamp((outTimeMicro / 1000.0) / totalDurationMs * 100.0, 0.0, 100.0);
            progress?.Report(percent);
        }

        await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);
        var stdErr = await stderrTask.ConfigureAwait(false);
        return (process.ExitCode, stdErr);
    }
}