using System.Diagnostics;
using System.Text.Json;
using VideoDownloader.Core.Config;

namespace VideoDownloader.Core.Social;

/// <summary>
/// yt-dlp 실행 파일 해결(설정 오버라이드 → 번들 → PATH → 자동 다운로드) +
/// 안전한 프로세스 실행(stdout/stderr 라인 단위 동시 드레인, 취소 시 트리 킬, exit 검증).
/// HlsDownloader.RunFfmpegAsync(#2 패턴) 과 동일한 안전 규칙을 따른다.
/// </summary>
public static class YtDlpRunner
{
    public static string ToolsDir => Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "VideoDownloader", "tools");

    private static string BundledPath => Path.Combine(ToolsDir,
        OperatingSystem.IsWindows() ? "yt-dlp.exe" : "yt-dlp");

    private static readonly HttpClient Downloader = new(new HttpClientHandler { AllowAutoRedirect = true })
    { Timeout = TimeSpan.FromMinutes(5) };

    private const string ReleaseUrl = "https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp.exe";

    // GitHub Releases API — 최신 태그(버전) 조회용. yt-dlp 태그는 "2026.03.17" 형식(--version 출력과 동일).
    private const string LatestReleaseApiUrl = "https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest";

    /// <summary>yt-dlp 경로를 해결한다. 못 찾으면 null.</summary>
    public static string? Resolve(AppConfig config)
    {
        if (!string.IsNullOrWhiteSpace(config.YtDlpPath) && File.Exists(config.YtDlpPath))
            return config.YtDlpPath;
        try { if (File.Exists(BundledPath)) return BundledPath; } catch { }
        return FindOnPath(OperatingSystem.IsWindows() ? "yt-dlp.exe" : "yt-dlp");
    }

    /// <summary>yt-dlp 가 없고 AutoInstallYtDlp 면 번들 디렉토리로 자동 다운로드. 경로 반환(실패 시 null).</summary>
    public static async Task<string?> EnsureInstalledAsync(AppConfig config, Action<string>? log, CancellationToken ct)
    {
        var found = Resolve(config);
        if (found != null) return found;
        if (!config.AutoInstallYtDlp) return null;
        return await DownloadAsync(config, log, ct);
    }

    /// <summary>yt-dlp 를 강제로(재)다운로드해 번들 디렉토리에 설치.</summary>
    public static async Task<string?> DownloadAsync(AppConfig config, Action<string>? log, CancellationToken ct)
    {
        try
        {
            Directory.CreateDirectory(ToolsDir);
            try { if (File.Exists(BundledPath)) File.Delete(BundledPath); } catch { }
            var tmp = BundledPath + ".tmp";
            log?.Invoke("yt-dlp 다운로드 중...");
            using var resp = await Downloader.GetAsync(ReleaseUrl, HttpCompletionOption.ResponseHeadersRead, ct);
            resp.EnsureSuccessStatusCode();
            await using var src = await resp.Content.ReadAsStreamAsync(ct);
            await using var dst = new FileStream(tmp, FileMode.Create, FileAccess.Write, FileShare.None, 65536, useAsync: true);
            await src.CopyToAsync(dst, 65536, ct);
            await dst.FlushAsync(ct);
            File.Move(tmp, BundledPath, overwrite: true);
            log?.Invoke($"yt-dlp 설치 완료: {BundledPath}");
            return BundledPath;
        }
        catch (Exception e)
        {
            log?.Invoke($"yt-dlp 다운로드 실패: {e.Message}");
            return null;
        }
    }

    /// <summary>설치된 yt-dlp 버전 문자열("2026.03.17"). 알 수 없으면 null.</summary>
    public static async Task<string?> GetVersionAsync(string exe, CancellationToken ct,
        Platform.IProcessRunner? runner = null)
    {
        try
        {
            var (exit, stdout, _) = await RunCaptureAsync(exe, new[] { "--version" }, ct, runner);
            if (exit != 0) return null;
            var first = stdout.Trim().Split('\n', StringSplitOptions.TrimEntries)[0];
            return string.IsNullOrWhiteSpace(first) ? null : first;
        }
        catch { return null; }
    }

    /// <summary>GitHub Releases 의 최신 yt-dlp 버전(태그). 조회 실패 시 null.</summary>
    public static async Task<string?> GetLatestVersionAsync(CancellationToken ct)
    {
        try
        {
            using var req = new HttpRequestMessage(HttpMethod.Get, LatestReleaseApiUrl);
            req.Headers.UserAgent.ParseAdd("VideoDownloader");       // GitHub API 요구 헤더
            req.Headers.Accept.ParseAdd("application/vnd.github+json");
            using var resp = await Downloader.SendAsync(req, ct);
            if (!resp.IsSuccessStatusCode) return null;
            var json = await resp.Content.ReadAsStringAsync(ct);
            using var doc = JsonDocument.Parse(json);
            if (doc.RootElement.TryGetProperty("tag_name", out var tag) &&
                tag.ValueKind == JsonValueKind.String)
                return tag.GetString()?.Trim().TrimStart('v');        // 태그 "v2026.03.17" → "2026.03.17"
            return null;
        }
        catch { return null; }
    }

    /// <summary>ffmpeg 위치(디렉토리) 를 찾는다(--ffmpeg-location). 없으면 null.</summary>
    public static string? ResolveFfmpegDir(AppConfig config)
    {
        string? exe = null;
        if (!string.IsNullOrWhiteSpace(config.FfmpegPath) && File.Exists(config.FfmpegPath))
            exe = config.FfmpegPath;
        else
        {
            var name = OperatingSystem.IsWindows() ? "ffmpeg.exe" : "ffmpeg";
            exe = FindOnPath(name);
        }
        return exe == null ? null : Path.GetDirectoryName(exe);
    }

    private static string? FindOnPath(string name)
    {
        foreach (var d in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator))
        {
            var p = Path.Combine(d.Trim('"'), name);
            if (File.Exists(p)) return p;
        }
        return null;
    }

    /// <summary>프로세스 실행. onLine(stream, line): stream="out"|"err". 취소 시 트리 킬.
    /// 재구성 ②: IProcessRunner 주입 가능(테스트/모바일) — 기본 DesktopProcessRunner.</summary>
    public static async Task<int> RunAsync(string exe, IEnumerable<string> args,
        Action<string, string> onLine, CancellationToken ct, Platform.IProcessRunner? runner = null)
    {
        var r = runner ?? Platform.DesktopProcessRunner.Default;
        var res = await r.RunAsync(new Platform.ProcessSpec(exe, args.ToList(),
            EnvPrefix: new Dictionary<string, string> { ["PATH"] = ToolsDir }), onLine, ct);
        return res.ExitCode;
    }

    /// <summary>stdout 전체를 하나의 문자열로 캡처(-J JSON 덤프용). 재구성 ②: 러너 주입 가능.</summary>
    public static async Task<(int Exit, string Stdout, string Stderr)> RunCaptureAsync(
        string exe, IEnumerable<string> args, CancellationToken ct, Platform.IProcessRunner? runner = null)
    {
        var r = runner ?? Platform.DesktopProcessRunner.Default;
        var res = await r.RunAsync(new Platform.ProcessSpec(exe, args.ToList(),
            EnvPrefix: new Dictionary<string, string> { ["PATH"] = ToolsDir }), null, ct);
        return (res.ExitCode, res.Stdout, res.Stderr);
    }
}