using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using ControlPlane.Core.Messages;
using MassTransit;

namespace ControlPlane.Api.Endpoints;

public static class GiteaWebhookEndpoints
{
    // Map of Gitea repo name → solution file (relative to cloned repo root)
    private static readonly Dictionary<string, string> RepoSolutions = new(StringComparer.OrdinalIgnoreCase)
    {
        ["OPC"]     = "ControlPlane.slnx",
        ["Clarity"] = "Clarity.slnx",
    };

    public static IEndpointRouteBuilder MapGiteaWebhookEndpoints(this IEndpointRouteBuilder app)
    {
        app.MapPost("/api/hooks/gitea/push", HandlePushAsync)
           .WithName("Gitea:PushWebhook")
           .AllowAnonymous(); // validated via HMAC below

        return app;
    }

    private static async Task<IResult> HandlePushAsync(
        HttpRequest         request,
        IPublishEndpoint    bus,
        IConfiguration      config,
        ILogger<GiteaWebhookEndpointsMarker> logger,
        CancellationToken   ct)
    {
        // ── HMAC-SHA256 signature validation ─────────────────────────────────
        var secret = config["Gitea:WebhookSecret"];
        if (!string.IsNullOrWhiteSpace(secret))
        {
            if (!request.Headers.TryGetValue("X-Gitea-Signature", out var sigHeader))
                return Results.Unauthorized();

            var body = await ReadBodyAsync(request, ct);
            var expectedSig = ComputeHmacSha256(body, secret);

            if (!CryptographicOperations.FixedTimeEquals(
                    Encoding.ASCII.GetBytes(sigHeader.ToString()),
                    Encoding.ASCII.GetBytes(expectedSig)))
            {
                logger.LogWarning("Gitea push webhook: HMAC signature mismatch — ignoring.");
                return Results.Unauthorized();
            }

            var payload = JsonSerializer.Deserialize<GiteaPushPayload>(body, JsonOpts);
            return await ProcessPayloadAsync(payload, bus, logger, ct);
        }
        else
        {
            // No secret configured — accept without validation (dev only)
            logger.LogWarning("Gitea:WebhookSecret is not configured — webhook signature validation is disabled.");
            var payload = await JsonSerializer.DeserializeAsync<GiteaPushPayload>(
                request.Body, JsonOpts, ct);
            return await ProcessPayloadAsync(payload, bus, logger, ct);
        }
    }

    private static async Task<IResult> ProcessPayloadAsync(
        GiteaPushPayload?     payload,
        IPublishEndpoint      bus,
        ILogger<GiteaWebhookEndpointsMarker> logger,
        CancellationToken     ct)
    {
        if (payload is null)
            return Results.BadRequest("Could not parse push payload.");

        // Only act on pushes to develop
        if (payload.Ref != "refs/heads/develop")
        {
            logger.LogDebug("Gitea push webhook: ignoring push to {Ref}", payload.Ref);
            return Results.Ok(new { skipped = true, reason = "not develop" });
        }

        var repoName = payload.Repository?.Name;
        if (string.IsNullOrWhiteSpace(repoName) || !RepoSolutions.TryGetValue(repoName, out var solutionPath))
        {
            logger.LogWarning("Gitea push webhook: unknown or unsupported repo '{Repo}'", repoName);
            return Results.Ok(new { skipped = true, reason = "unsupported repo" });
        }

        var headSha = payload.After;
        if (string.IsNullOrWhiteSpace(headSha) || headSha == "0000000000000000000000000000000000000000")
        {
            logger.LogInformation("Gitea push webhook: branch deleted — nothing to build.");
            return Results.Ok(new { skipped = true, reason = "branch deleted" });
        }

        logger.LogInformation(
            "Gitea push webhook: queuing build for {Repo}@{Sha} ({Branch})",
            repoName, headSha[..8], payload.Ref);

        await bus.Publish(new BuildRequestedCommand
        {
            RepoName     = repoName,
            HeadSha      = headSha,
            Branch       = "develop",
            SolutionPath = solutionPath,
        }, ct);

        return Results.Accepted(value: new { queued = true, repo = repoName, sha = headSha[..8] });
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    private static async Task<byte[]> ReadBodyAsync(HttpRequest request, CancellationToken ct)
    {
        request.EnableBuffering();
        using var ms = new MemoryStream();
        await request.Body.CopyToAsync(ms, ct);
        request.Body.Position = 0;
        return ms.ToArray();
    }

    private static string ComputeHmacSha256(byte[] body, string secret)
    {
        var key  = Encoding.UTF8.GetBytes(secret);
        var hash = HMACSHA256.HashData(key, body);
        return Convert.ToHexString(hash).ToLowerInvariant();
    }

    private static readonly JsonSerializerOptions JsonOpts = new(JsonSerializerDefaults.Web);

    // Marker type for logger category
    private sealed class GiteaWebhookEndpointsMarker;
}

// ── Payload DTOs ──────────────────────────────────────────────────────────────

public sealed class GiteaPushPayload
{
    [JsonPropertyName("ref")]
    public string Ref { get; init; } = string.Empty;

    [JsonPropertyName("before")]
    public string Before { get; init; } = string.Empty;

    [JsonPropertyName("after")]
    public string After { get; init; } = string.Empty;

    [JsonPropertyName("repository")]
    public GiteaPushRepo? Repository { get; init; }
}

public sealed class GiteaPushRepo
{
    [JsonPropertyName("name")]
    public string Name { get; init; } = string.Empty;

    [JsonPropertyName("full_name")]
    public string FullName { get; init; } = string.Empty;
}