using ControlPlane.Core.Models;
using ControlPlane.Core.Services;
using Docker.DotNet;
using Docker.DotNet.Models;
using LibGit2Sharp;

namespace ControlPlane.Api.Services;

/// <summary>
/// Drives `docker build` for the clarity-server image via the Docker SDK.
/// Streams each build log line to the provided callback so the API endpoint
/// can forward it as SSE to the control plane UI in real time.
/// Persists build history via BuildHistoryService.
/// </summary>
public class ImageBuildService(
    IConfiguration config,
    BuildHistoryService history,
    ILogger<ImageBuildService> logger)
{
    private static readonly SemaphoreSlim _lock = new(1, 1);

    public bool   IsBuilding => _lock.CurrentCount == 0;
    public string ImageName  => config["Docker:ClarityServerImage"] ?? "clarity-server:latest";

    public async Task<ImageBuildStatus> GetStatusAsync()
    {
        var builds = await history.GetBuildsAsync();
        var last   = builds.FirstOrDefault(b => b.Kind == BuildKind.DockerImage);
        return new ImageBuildStatus(
            last?.Target,
            last?.FinishedAt,
            last?.Status.ToString() ?? "Never built",
            IsBuilding);
    }

    /// <summary>
    /// Runs docker build and streams each log line to <paramref name="onLine"/>.
    /// Returns true on success, false if the build failed or was already running.
    /// </summary>
    public async Task<bool> BuildAsync(
        string repoRoot,
        Action<string> onLine,
        CancellationToken ct)
    {
        if (!await _lock.WaitAsync(TimeSpan.Zero, ct))
        {
            onLine("⚠️  A build is already in progress.");
            return false;
        }

        var record = await history.CreateBuildAsync(BuildKind.DockerImage, ImageName);

        // Capture HEAD SHA so the build is traceable back to a specific commit
        try
        {
            using var repo = new Repository(repoRoot);
            record.CommitSha = repo.Head.Tip?.Sha;
        }
        catch { /* not a git repo or no commits yet — CommitSha stays null */ }

        try
        {
            var socketUri = config["Docker:Socket"] ?? "npipe://./pipe/docker_engine";
            using var docker = new DockerClientConfiguration(new Uri(socketUri)).CreateClient();

            var (repo, tag) = SplitImageTag(ImageName);
            var dockerfilePath = "Clarity/Clarity.Server/Dockerfile";

            void Log(string line) { onLine(line); record.Log.Add(line); }

            Log($"▶ Building {ImageName} from {repoRoot}");
            Log($"  Dockerfile: {dockerfilePath}");
            Log("──────────────────────────────────────");

            var buildParams = new ImageBuildParameters
            {
                Dockerfile  = dockerfilePath,
                Tags        = [$"{repo}:{tag}"],
                Remove      = true,
                ForceRemove = true,
            };

            bool   success     = true;
            string? errorDetail = null;

            await docker.Images.BuildImageFromDockerfileAsync(
                buildParams,
                await CreateTarballAsync(repoRoot, ct),
                authConfigs: null,
                headers: null,
                new Progress<JSONMessage>(msg =>
                {
                    if (!string.IsNullOrWhiteSpace(msg.Stream))
                        Log(msg.Stream.TrimEnd('\n'));

                    if (msg.Error is not null)
                    {
                        success     = false;
                        errorDetail = msg.Error.Message;
                        Log($"✖ {msg.Error.Message}");
                    }
                }),
                ct);

            Log("──────────────────────────────────────");
            if (success) Log($"✔ {ImageName} built successfully at {DateTimeOffset.UtcNow:u}");
            else         Log($"✖ Build failed: {errorDetail}");

            await history.CompleteBuildAsync(record, success ? BuildStatus.Succeeded : BuildStatus.Failed);
            logger.LogInformation("Image build {Result} for {Image}", success ? "succeeded" : "failed", ImageName);
            return success;
        }
        catch (Exception ex)
        {
            record.Log.Add($"Exception: {ex.Message}");
            await history.CompleteBuildAsync(record, BuildStatus.Failed);
            onLine($"✖ Exception during build: {ex.Message}");
            logger.LogError(ex, "Image build threw an exception.");
            return false;
        }
        finally
        {
            _lock.Release();
        }
    }

    /// <summary>
    /// Packs the entire repo root into a tar stream for the Docker build context.
    /// Respects .dockerignore if present.
    /// </summary>
    private static async Task<Stream> CreateTarballAsync(string repoRoot, CancellationToken ct)
    {
        // Use docker's own CLI to create the tarball via stdin — avoids reimplementing
        // .dockerignore parsing. Fall back to a pure managed tar if CLI isn't available.
        // For simplicity we use a managed approach: stream the directory as a tar.
        var ms = new MemoryStream();
        await Task.Run(() => TarHelper.Pack(repoRoot, ms), ct);
        ms.Position = 0;
        return ms;
    }

    private static (string repo, string tag) SplitImageTag(string image)
    {
        var colon = image.LastIndexOf(':');
        return colon < 0 ? (image, "latest") : (image[..colon], image[(colon + 1)..]);
    }
}

public record ImageBuildStatus(
    string? ImageName,
    DateTimeOffset? BuiltAt,
    string LastMessage,
    bool IsBuilding);