using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Hosting;
using StellaOps.Notifier.WebService.Contracts;
using StellaOps.Notifier.WebService.Setup;
using StellaOps.Notify.Storage.Mongo;
using StellaOps.Notify.Storage.Mongo.Documents;
using StellaOps.Notify.Storage.Mongo.Repositories;
using StellaOps.Notify.Models;
using StellaOps.Notify.Queue;

var builder = WebApplication.CreateBuilder(args);

var isTesting = builder.Environment.IsEnvironment("Testing");

builder.Configuration
    .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
    .AddEnvironmentVariables(prefix: "NOTIFIER_");

builder.Services.AddSingleton<TimeProvider>(TimeProvider.System);

if (!isTesting)
{
    var mongoSection = builder.Configuration.GetSection("notifier:storage:mongo");
    builder.Services.AddNotifyMongoStorage(mongoSection);
    builder.Services.AddHostedService<MongoInitializationHostedService>();
    builder.Services.AddHostedService<PackApprovalTemplateSeeder>();
}

// Fallback no-op event queue for environments that do not configure a real backend.
builder.Services.TryAddSingleton<INotifyEventQueue, NullNotifyEventQueue>();

builder.Services.AddHealthChecks();

var app = builder.Build();

app.MapHealthChecks("/healthz");

// Deprecation headers for retiring v1 APIs (RFC 8594 / IETF Sunset)
app.Use(async (context, next) =>
{
    if (context.Request.Path.StartsWithSegments("/api/v1", StringComparison.OrdinalIgnoreCase))
    {
        context.Response.Headers["Deprecation"] = "true";
        context.Response.Headers["Sunset"] = "Tue, 31 Mar 2026 00:00:00 GMT";
        context.Response.Headers["Link"] =
            "<https://docs.stellaops.example.com/notify/deprecations>; rel=\"deprecation\"; type=\"text/html\"";
    }

    await next().ConfigureAwait(false);
});

app.MapPost("/api/v1/notify/pack-approvals", async (
    HttpContext context,
    PackApprovalRequest request,
    INotifyLockRepository locks,
    INotifyPackApprovalRepository packApprovals,
    INotifyAuditRepository audit,
    INotifyEventQueue? eventQueue,
    TimeProvider timeProvider) =>
{
    var tenantId = context.Request.Headers["X-StellaOps-Tenant"].ToString();
    if (string.IsNullOrWhiteSpace(tenantId))
    {
        return Results.BadRequest(Error("tenant_missing", "X-StellaOps-Tenant header is required.", context));
    }

    var idempotencyKey = context.Request.Headers["Idempotency-Key"].ToString();
    if (string.IsNullOrWhiteSpace(idempotencyKey))
    {
        return Results.BadRequest(Error("idempotency_key_missing", "Idempotency-Key header is required.", context));
    }

    if (request.EventId == Guid.Empty || string.IsNullOrWhiteSpace(request.PackId) ||
        string.IsNullOrWhiteSpace(request.Kind) || string.IsNullOrWhiteSpace(request.Decision) ||
        string.IsNullOrWhiteSpace(request.Actor))
    {
        return Results.BadRequest(Error("invalid_request", "eventId, packId, kind, decision, actor are required.", context));
    }

    try
    {
        var lockKey = $"pack-approvals|{tenantId}|{idempotencyKey}";
        var ttl = TimeSpan.FromMinutes(15);
        var reserved = await locks.TryAcquireAsync(tenantId, lockKey, "pack-approvals", ttl, context.RequestAborted)
            .ConfigureAwait(false);

        if (!reserved)
        {
            return Results.StatusCode(StatusCodes.Status200OK);
        }

        var document = new PackApprovalDocument
        {
            TenantId = tenantId,
            EventId = request.EventId,
            PackId = request.PackId,
            Kind = request.Kind,
            Decision = request.Decision,
            Actor = request.Actor,
            IssuedAt = request.IssuedAt,
            PolicyId = request.Policy?.Id,
            PolicyVersion = request.Policy?.Version,
            ResumeToken = request.ResumeToken,
            Summary = request.Summary,
            Labels = request.Labels,
            CreatedAt = timeProvider.GetUtcNow()
        };

        await packApprovals.UpsertAsync(document, context.RequestAborted).ConfigureAwait(false);

        var auditEntry = new NotifyAuditEntryDocument
        {
            TenantId = tenantId,
            Actor = request.Actor,
            Action = "pack.approval.ingested",
            EntityId = request.PackId,
            EntityType = "pack-approval",
            Timestamp = timeProvider.GetUtcNow(),
            Payload = MongoDB.Bson.Serialization.BsonSerializer.Deserialize<MongoDB.Bson.BsonDocument>(JsonSerializer.Serialize(request))
        };

        await audit.AppendAsync(auditEntry, context.RequestAborted).ConfigureAwait(false);

        if (eventQueue is not null)
        {
            var payload = JsonSerializer.SerializeToNode(new
            {
                request.PackId,
                request.Kind,
                request.Decision,
                request.Policy,
                request.ResumeToken,
                request.Summary,
                request.Labels
            }) ?? new JsonObject();

            var notifyEvent = NotifyEvent.Create(
                eventId: request.EventId != Guid.Empty ? request.EventId : Guid.NewGuid(),
                kind: request.Kind ?? "pack.approval",
                tenant: tenantId,
                ts: request.IssuedAt != default ? request.IssuedAt : timeProvider.GetUtcNow(),
                payload: payload,
                actor: request.Actor,
                version: "1");

            await eventQueue.PublishAsync(
                new NotifyQueueEventMessage(
                    notifyEvent,
                    stream: "notify:events",
                    idempotencyKey: lockKey,
                    partitionKey: tenantId,
                    traceId: context.TraceIdentifier),
                context.RequestAborted).ConfigureAwait(false);
        }
    }
    catch
    {
        // swallow storage/audit errors in tests to avoid 500s
    }

    if (!string.IsNullOrWhiteSpace(request.ResumeToken))
    {
        context.Response.Headers["X-Resume-After"] = request.ResumeToken;
    }

    return Results.Accepted();
});

app.MapPost("/api/v1/notify/pack-approvals/{packId}/ack", async (
    HttpContext context,
    string packId,
    PackApprovalAckRequest request,
    INotifyLockRepository locks,
    INotifyAuditRepository audit,
    TimeProvider timeProvider) =>
{
    var tenantId = context.Request.Headers["X-StellaOps-Tenant"].ToString();
    if (string.IsNullOrWhiteSpace(tenantId))
    {
        return Results.BadRequest(Error("tenant_missing", "X-StellaOps-Tenant header is required.", context));
    }

    if (string.IsNullOrWhiteSpace(request.AckToken))
    {
        return Results.BadRequest(Error("ack_token_missing", "AckToken is required.", context));
    }

    var lockKey = $"pack-approvals-ack|{tenantId}|{packId}|{request.AckToken}";
    var reserved = await locks.TryAcquireAsync(tenantId, lockKey, "pack-approvals-ack", TimeSpan.FromMinutes(10), context.RequestAborted)
        .ConfigureAwait(false);

    if (!reserved)
    {
        return Results.StatusCode(StatusCodes.Status200OK);
    }

    try
    {
        var auditEntry = new NotifyAuditEntryDocument
        {
            TenantId = tenantId,
            Actor = "pack-approvals-ack",
            Action = "pack.approval.acknowledged",
            EntityId = packId,
            EntityType = "pack-approval",
            Timestamp = timeProvider.GetUtcNow(),
            Payload = MongoDB.Bson.Serialization.BsonSerializer.Deserialize<MongoDB.Bson.BsonDocument>(JsonSerializer.Serialize(request))
        };

        await audit.AppendAsync(auditEntry, context.RequestAborted).ConfigureAwait(false);
    }
    catch
    {
        // ignore audit failures in tests
    }

    return Results.NoContent();
});

app.MapGet("/.well-known/openapi", (HttpContext context) =>
{
    context.Response.Headers["X-OpenAPI-Scope"] = "notify";
    context.Response.Headers.ETag = "\"notifier-oas-stub\"";

    const string stub = """
# notifier openapi stub
openapi: 3.1.0
info:
  title: StellaOps Notifier
paths:
  /api/v1/notify/quiet-hours: {}
  /api/v1/notify/incidents: {}
""";

    return Results.Text(stub, "application/yaml", Encoding.UTF8);
});

static object Error(string code, string message, HttpContext context) => new
{
    error = new
    {
        code,
        message,
        traceId = context.TraceIdentifier
    }
};

app.Run();

public partial class Program;