using System.Diagnostics;
using System.Text.Json;
using System.Text.RegularExpressions;
using ControlPlane.Api.Services;

namespace ControlPlane.Api.Endpoints;

public static class ImageBuildEndpoints
{
    private static readonly JsonSerializerOptions JsonOpts = new(JsonSerializerDefaults.Web);

    public static IEndpointRouteBuilder MapImageBuildEndpoints(this IEndpointRouteBuilder app)
    {
        var group = app.MapGroup("/api/image").WithTags("Image");

        group.MapGet("/status",  GetStatus);
        group.MapPost("/build",  TriggerBuild);

        // Post-provisioning verification helpers
        group.MapGet ("/verify/extra-hosts/{containerName}", GetExtraHosts);
        group.MapPost("/verify/dns-test",                    DnsTest);
        group.MapGet ("/artifact/{subdomain}",               GetArtifact);

        return app;
    }

    /// <summary>Returns the last known build status without triggering a new build.</summary>
    private static async Task<IResult> GetStatus(ImageBuildService svc) =>
        Results.Ok(await svc.GetStatusAsync());

    /// <summary>
    /// Triggers a docker build and streams the output line-by-line as SSE.
    /// The build context is the repo root, which must be configured via
    /// Docker:RepoRoot in appsettings / environment.
    /// </summary>
    private static async Task TriggerBuild(
        HttpContext ctx,
        ImageBuildService svc,
        IConfiguration config,
        CancellationToken ct)
    {
        var repoRoot = config["Docker:RepoRoot"];
        if (string.IsNullOrWhiteSpace(repoRoot) || !Directory.Exists(repoRoot))
        {
            ctx.Response.StatusCode = 400;
            await ctx.Response.WriteAsJsonAsync(new
            {
                error = "Docker:RepoRoot is not configured or does not exist.",
                hint  = "Add Docker__RepoRoot to the worker environment pointing at the repo root directory.",
            }, ct);
            return;
        }

        ctx.Response.Headers.ContentType  = "text/event-stream";
        ctx.Response.Headers.CacheControl = "no-cache";
        ctx.Response.Headers.Connection   = "keep-alive";

        // Use a Channel so the Progress<T> callback (sync) can safely hand lines
        // to the async SSE writer without blocking the Docker build thread.
        var channel = System.Threading.Channels.Channel.CreateUnbounded<string?>(
            new System.Threading.Channels.UnboundedChannelOptions { SingleWriter = true, SingleReader = true });

        void OnLine(string line) => channel.Writer.TryWrite(line);

        // Run the build on a background thread so we can drain the channel here
        var buildTask = Task.Run(() => svc.BuildAsync(repoRoot, OnLine, ct), ct)
            .ContinueWith(_ => channel.Writer.TryComplete(), TaskScheduler.Default);

        await foreach (var line in channel.Reader.ReadAllAsync(ct))
        {
            var json = JsonSerializer.Serialize(new { line }, JsonOpts);
            await ctx.Response.WriteAsync($"data: {json}\n\n", ct);
            await ctx.Response.Body.FlushAsync(ct);
        }

        await buildTask; // ensure build is fully done

        // Signal stream end
        await ctx.Response.WriteAsync("data: {\"done\":true}\n\n", ct);
        await ctx.Response.Body.FlushAsync(ct);
    }

    // ── Post-provisioning verification endpoints ──────────────────────────────

    private static readonly Regex SafeContainerName = new(@"^[a-zA-Z0-9_.\-]+$", RegexOptions.Compiled);

    /// <summary>
    /// Returns the ExtraHosts list for a running tenant container.
    /// e.g. GET /api/image/verify/extra-hosts/fdev-app-clarity-01000001
    /// </summary>
    private static async Task<IResult> GetExtraHosts(string containerName)
    {
        if (!SafeContainerName.IsMatch(containerName))
            return Results.BadRequest(new { error = "Invalid container name." });

        var (code, output) = await DockerRunAsync($"inspect --format {{{{json .HostConfig.ExtraHosts}}}} {containerName}");
        if (code != 0 || string.IsNullOrWhiteSpace(output))
            return Results.NotFound(new { error = $"Container '{containerName}' not found or not running.", detail = output });

        try
        {
            var hosts = JsonDocument.Parse(output.Trim()).RootElement;
            return Results.Ok(new { containerName, extraHosts = hosts });
        }
        catch
        {
            return Results.Ok(new { containerName, extraHosts = (object?)null, raw = output.Trim() });
        }
    }

    /// <summary>
    /// Runs <c>curl</c> from inside the container to verify *.clarity.test DNS resolves through nginx.
    /// POST /api/image/verify/dns-test  body: { container, url }
    /// </summary>
    private static async Task<IResult> DnsTest(DnsTestRequest body)
    {
        if (!SafeContainerName.IsMatch(body.Container))
            return Results.BadRequest(new { error = "Invalid container name." });

        // Only allow http/https URLs — prevents command injection via url field
        if (!body.Url.StartsWith("http://", StringComparison.OrdinalIgnoreCase) &&
            !body.Url.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
            return Results.BadRequest(new { error = "URL must start with http:// or https://." });

        var psi = new ProcessStartInfo("docker",
            $"exec {body.Container} curl -sf --max-time 10 --write-out \"\\nHTTP %{{http_code}}\" {body.Url}")
        {
            RedirectStandardOutput = true,
            RedirectStandardError  = true,
            UseShellExecute        = false,
            CreateNoWindow         = true,
        };

        using var proc = Process.Start(psi);
        if (proc is null) return Results.Problem("Failed to start docker process.");

        var stdout = await proc.StandardOutput.ReadToEndAsync();
        var stderr = await proc.StandardError.ReadToEndAsync();
        await proc.WaitForExitAsync();

        return Results.Ok(new
        {
            success  = proc.ExitCode == 0,
            exitCode = proc.ExitCode,
            output   = stdout.Trim(),
            error    = stderr.Trim(),
        });
    }

    /// <summary>
    /// Reads the generated docker-compose.yml from ClientAssets/{subdomain}/.
    /// GET /api/image/artifact/{subdomain}
    /// </summary>
    private static async Task<IResult> GetArtifact(string subdomain, IConfiguration config)
    {
        // Restrict subdomain to safe characters — prevents path traversal
        if (!SafeContainerName.IsMatch(subdomain))
            return Results.BadRequest(new { error = "Invalid subdomain." });

        var root = config["ClientAssets__Folder"] ?? config["ClientAssets:Folder"]
                   ?? Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, "..", "ClientAssets"));

        // Use Path.GetFileName to ensure no directory traversal
        var safeSubdomain  = Path.GetFileName(subdomain);
        var composePath    = Path.GetFullPath(Path.Combine(root, safeSubdomain, "docker-compose.yml"));

        // Verify the final path is still inside the ClientAssets root
        if (!composePath.StartsWith(Path.GetFullPath(root), StringComparison.OrdinalIgnoreCase))
            return Results.BadRequest(new { error = "Invalid subdomain path." });

        if (!File.Exists(composePath))
            return Results.NotFound(new { error = $"No compose artifact found for '{subdomain}'." });

        var content = await File.ReadAllTextAsync(composePath);
        return Results.Ok(new { subdomain, path = composePath, content });
    }

    private static async Task<(int code, string? output)> DockerRunAsync(string args)
    {
        var psi = new ProcessStartInfo("docker", args)
        {
            RedirectStandardOutput = true,
            RedirectStandardError  = true,
            UseShellExecute        = false,
            CreateNoWindow         = true,
        };
        using var proc = Process.Start(psi);
        if (proc is null) return (-1, null);
        var output = await proc.StandardOutput.ReadToEndAsync();
        var err    = await proc.StandardError.ReadToEndAsync();
        await proc.WaitForExitAsync();
        return (proc.ExitCode, string.IsNullOrWhiteSpace(output) ? err : output);
    }

    private record DnsTestRequest(string Container, string Url);
}