using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using Xunit;
using ytLive.Services.Encoder;

namespace ytLive.Tests;

/// <summary>
/// The FFmpeg locator (TASK 4 ship step 2, rewritten by TASK 48 item 1).
///
/// <para><b>What changed.</b> The locator used to pin a BtbN release URL, download the zip
/// on first run, extract it, and execute it. That is Windows Store policy 10.2.2 (dynamic
/// code inclusion — <c>TASKS/research-store-certification.md</c> §4) and it had already
/// failed in production: the pin aged out of BtbN's 14-day retention and the download
/// <b>404'd on the creator's first real recording attempt</b> (2026-09-01). FFmpeg is now
/// <b>bundled</b>, fetched at build time by <c>scripts/fetch-ffmpeg.sh</c> and copied into
/// <c>ffmpeg/</c> beside the executable. Nothing is downloaded at runtime, ever.</para>
///
/// <para><b>Why the order flipped.</b> PATH used to win ("the user's own install wins").
/// With a bundle in the package that is backwards: a PATH <c>ffmpeg</c> may be a different
/// major version or a GPL build, and the bundle is the one that was pinned, license-vetted
/// and tested. PATH remains the escape hatch for someone who deliberately wants their own.</para>
/// </summary>
public class FfmpegLocatorTests
{
    private static string TempDir()
    {
        var dir = Path.Combine(Path.GetTempPath(), "ytllive-tests-" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(dir);
        return dir;
    }

    /// <summary>Repo root, found by walking up to a file only the repo has.</summary>
    private static string RepoRoot()
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir != null)
        {
            if (File.Exists(Path.Combine(dir.FullName, "ytLive.csproj"))) return dir.FullName;
            dir = dir.Parent;
        }
        throw new FileNotFoundException($"could not locate ytLive.csproj above {AppContext.BaseDirectory}");
    }

    private static string RepoFile(params string[] parts)
    {
        var candidate = Path.Combine(new[] { RepoRoot() }.Concat(parts).ToArray());
        if (File.Exists(candidate)) return candidate;
        throw new FileNotFoundException($"could not locate {Path.Combine(parts)} under {RepoRoot()}");
    }

    /// <summary>
    /// The Good Dog integration test for this unit: prove the whole chain end to end —
    /// the build actually copied the bundle into the app's output, the locator resolves it
    /// without any network, and the located binary <b>executes</b>. Running it is the part
    /// that matters most: FFmpeg is an lgpl-<i>shared</i> build, so it only starts if every
    /// <c>libav*.dll</c> sits beside the exe. A packaging change that dropped the DLLs would
    /// pass every existence check and still hand the user a broken encoder.
    /// </summary>
    [Fact]
    public async Task Locate_Integration_TheBuiltOutputShipsABundleThatRuns()
    {
        // NOTE: the output root is derived from the *project* directory, not from the
        // repository folder name. The repo directory happens to also be called "ytLive",
        // so naively appending "ytLive" would resolve to a path that only works on this
        // machine's checkout.
        var projectDir = Path.GetDirectoryName(RepoFile("ytLive.csproj"))!;
        var binRoot = Path.Combine(projectDir, "bin");
        Assert.True(Directory.Exists(binRoot),
            $"no build output at {binRoot} — build ytLive.csproj before running this test");

        var withBundle = Directory
            .GetDirectories(binRoot, "*", SearchOption.AllDirectories)
            .Where(d => File.Exists(Path.Combine(d, FfmpegLocator.BundleFolderName, FfmpegLocator.FileName)))
            .ToArray();

        Assert.True(withBundle.Length > 0,
            $"No build output under {binRoot} carries ffmpeg/{FfmpegLocator.FileName}. " +
            "Run ./scripts/fetch-ffmpeg.sh, then rebuild — the csproj GuardBundledFfmpeg " +
            "target should have failed the build if the source folder was missing.");

        var outputDir = withBundle[0];
        var bundleDir = Path.Combine(outputDir, FfmpegLocator.BundleFolderName);

        // The sibling DLLs are the shared-build's whole dependency story.
        foreach (var required in new[] { FfmpegLocator.ProbeFileName, "avcodec-63.dll", "avformat-63.dll" })
            Assert.True(File.Exists(Path.Combine(bundleDir, required)),
                $"{required} must ship beside {FfmpegLocator.FileName} — a shared build resolves DLLs " +
                "from the executable's own directory.");

        // The locator resolves it with an empty PATH, i.e. nothing outside the bundle.
        var resolved = await new FfmpegLocator(searchDirs: [], bundleRoot: outputDir).LocateAsync();

        Assert.Equal(Path.Combine(bundleDir, FfmpegLocator.FileName), resolved);

        // And it actually runs. This is what proves the DLLs resolve.
        var info = new ProcessStartInfo
        {
            FileName = resolved,
            Arguments = "-version",
            UseShellExecute = false,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            CreateNoWindow = true,
        };
        using var process = Process.Start(info)!;
        var stdout = process.StandardOutput.ReadToEnd();
        Assert.True(process.WaitForExit(milliseconds: 30_000), "bundled ffmpeg -version did not exit in 30s");
        Assert.Equal(0, process.ExitCode);
        Assert.Contains("ffmpeg version", stdout, StringComparison.OrdinalIgnoreCase);
    }

    [Fact]
    public async Task Locate_PrefersTheBundle_OverAPathInstall()
    {
        var root = TempDir();
        try
        {
            var pathDir = Path.Combine(root, "on-path");
            var bundleDir = Path.Combine(root, FfmpegLocator.BundleFolderName);
            Directory.CreateDirectory(pathDir);
            Directory.CreateDirectory(bundleDir);
            File.WriteAllText(Path.Combine(pathDir, FfmpegLocator.FileName), "user's ffmpeg");
            var bundled = Path.Combine(bundleDir, FfmpegLocator.FileName);
            File.WriteAllText(bundled, "bundled ffmpeg");

            var resolved = await new FfmpegLocator([pathDir], root).LocateAsync();
            Assert.Equal(bundled, resolved);
        }
        finally
        {
            Directory.Delete(root, recursive: true);
        }
    }

    [Fact]
    public async Task Locate_FallsBackToPath_WhenNoBundleIsPresent()
    {
        var root = TempDir();
        try
        {
            var pathDir = Path.Combine(root, "on-path");
            Directory.CreateDirectory(pathDir);
            var onPath = Path.Combine(pathDir, FfmpegLocator.FileName);
            File.WriteAllText(onPath, "user's ffmpeg");

            var resolved = await new FfmpegLocator([pathDir], root).LocateAsync();
            Assert.Equal(onPath, resolved);
        }
        finally
        {
            Directory.Delete(root, recursive: true);
        }
    }

    [Fact]
    public async Task Locate_ZeroByteBundle_IsNotUsable()
    {
        var root = TempDir();
        try
        {
            var bundleDir = Path.Combine(root, FfmpegLocator.BundleFolderName);
            Directory.CreateDirectory(bundleDir);
            File.WriteAllText(Path.Combine(bundleDir, FfmpegLocator.FileName), "");

            var ex = await Assert.ThrowsAsync<IOException>(
                () => new FfmpegLocator([], root).LocateAsync());
            Assert.Contains(FfmpegLocator.BundleFolderName, ex.Message, StringComparison.Ordinal);
        }
        finally
        {
            Directory.Delete(root, recursive: true);
        }
    }

    /// <summary>
    /// A missing bundle must be LOUD and must say where to look. The old ladder had a
    /// "found something on disk" path that could quietly satisfy a missing bundle with a
    /// stale cached copy — silent drift in exactly the dependency Store certification
    /// inspects, and silent drift is how a packaging bug ships.
    /// </summary>
    [Fact]
    public async Task Locate_NoBundleAndNoPath_ThrowsNamingTheBundleFolderAndTheFix()
    {
        var root = TempDir();
        try
        {
            var ex = await Assert.ThrowsAsync<IOException>(
                () => new FfmpegLocator([], root).LocateAsync());
            Assert.Contains(FfmpegLocator.BundleFolderName, ex.Message, StringComparison.Ordinal);
            Assert.Contains("fetch-ffmpeg.sh", ex.Message, StringComparison.Ordinal);
            Assert.Contains("PATH", ex.Message, StringComparison.Ordinal);
        }
        finally
        {
            Directory.Delete(root, recursive: true);
        }
    }

    /// <summary>
    /// The Store-gate assertion, kept as a source-level fact so it cannot rot: the locator
    /// must contain no network capability at all. Policy 10.2.2 forbids download-and-execute,
    /// and this is the only type in the app that ever executed a downloaded binary. If a
    /// future change reintroduces an HttpClient, a URL, or a downloader here, this fails —
    /// which is the entire point.
    ///
    /// <para>Patterns are <b>call-shaped</b> (<c>new HttpClient</c>, not <c>HttpClient</c>)
    /// on purpose. A bare word match flags the file's own doc comment, which legitimately
    /// says "nothing is downloaded" — a test that fails on the prose explaining the
    /// guarantee is a test that gets deleted instead of obeyed.</para>
    /// </summary>
    [Theory]
    [InlineData("new HttpClient")]
    [InlineData("HttpClient()")]
    [InlineData("GetByteArrayAsync(")]
    [InlineData("GetStreamAsync(")]
    [InlineData("WebRequest.Create")]
    [InlineData("DownloadFileTaskAsync")]
    [InlineData("http://")]
    [InlineData("https://")]
    [InlineData("PinnedUrl =")]
    [InlineData("ExtractBinaries(")]
    public void TheLocatorCarriesNoNetworkCapability(string forbidden)
    {
        var source = File.ReadAllText(
            RepoFile("Services", "Encoder", "FfmpegLocator.cs"));

        Assert.DoesNotContain(forbidden, source, StringComparison.OrdinalIgnoreCase);
    }

    /// <summary>
    /// The guard that makes a forgotten bundle a build failure rather than a runtime one.
    /// Without it, a fresh clone with no <c>ffmpeg/</c> builds cleanly and the app only
    /// discovers the problem when the creator presses Record.
    /// </summary>
    [Fact]
    public void TheBuildRefusesToCompileWithoutTheBundle()
    {
        var csproj = File.ReadAllText(RepoFile("ytLive.csproj"));
        Assert.Contains("GuardBundledFfmpeg", csproj, StringComparison.Ordinal);
        Assert.Contains("ffmpeg\\ffmpeg.exe", csproj, StringComparison.Ordinal);
        Assert.Contains("CopyToPublishDirectory=\"Always\"", csproj, StringComparison.Ordinal);
    }
}