using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Options;
using StellaOps.Scanner.WebService.Constants;
using StellaOps.Scanner.WebService.Contracts;
using StellaOps.Scanner.WebService.Infrastructure;
using StellaOps.Scanner.WebService.Options;
using StellaOps.Scanner.WebService.Security;
using StellaOps.Scanner.WebService.Services;
using StellaOps.Zastava.Core.Contracts;

namespace StellaOps.Scanner.WebService.Endpoints;

internal static class RuntimeEndpoints
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    public static void MapRuntimeEndpoints(this RouteGroupBuilder apiGroup, string runtimeSegment)
    {
        ArgumentNullException.ThrowIfNull(apiGroup);

        var runtime = apiGroup
            .MapGroup(NormalizeSegment(runtimeSegment))
            .WithTags("Runtime");

        runtime.MapPost("/events", HandleRuntimeEventsAsync)
            .WithName("scanner.runtime.events.ingest")
            .Produces<RuntimeEventsIngestResponseDto>(StatusCodes.Status202Accepted)
            .Produces(StatusCodes.Status400BadRequest)
            .Produces(StatusCodes.Status429TooManyRequests)
            .RequireAuthorization(ScannerPolicies.RuntimeIngest);
    }

    private static async Task<IResult> HandleRuntimeEventsAsync(
        RuntimeEventsIngestRequestDto request,
        IRuntimeEventIngestionService ingestionService,
        IOptions<ScannerWebServiceOptions> options,
        HttpContext context,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(request);
        ArgumentNullException.ThrowIfNull(ingestionService);
        ArgumentNullException.ThrowIfNull(options);

        var runtimeOptions = options.Value.Runtime ?? new ScannerWebServiceOptions.RuntimeOptions();
        var validationError = ValidateRequest(request, runtimeOptions, context, out var envelopes);
        if (validationError is { } problem)
        {
            return problem;
        }

        var result = await ingestionService.IngestAsync(envelopes, request.BatchId, cancellationToken).ConfigureAwait(false);
        if (result.IsPayloadTooLarge)
        {
            var extensions = new Dictionary<string, object?>
            {
                ["payloadBytes"] = result.PayloadBytes,
                ["maxPayloadBytes"] = result.PayloadLimit
            };

            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Runtime event batch too large",
                StatusCodes.Status400BadRequest,
                detail: "Runtime batch payload exceeds configured budget.",
                extensions: extensions);
        }

        if (result.IsRateLimited)
        {
            var retryAfterSeconds = Math.Max(1, (int)Math.Ceiling(result.RetryAfter.TotalSeconds));
            context.Response.Headers.RetryAfter = retryAfterSeconds.ToString(CultureInfo.InvariantCulture);

            var extensions = new Dictionary<string, object?>
            {
                ["scope"] = result.RateLimitedScope,
                ["key"] = result.RateLimitedKey,
                ["retryAfterSeconds"] = retryAfterSeconds
            };

            return ProblemResultFactory.Create(
                context,
                ProblemTypes.RateLimited,
                "Runtime ingestion rate limited",
                StatusCodes.Status429TooManyRequests,
                detail: "Runtime ingestion exceeded configured rate limits.",
                extensions: extensions);
        }

        var payload = new RuntimeEventsIngestResponseDto
        {
            Accepted = result.Accepted,
            Duplicates = result.Duplicates
        };

        return Json(payload, StatusCodes.Status202Accepted);
    }

    private static IResult? ValidateRequest(
        RuntimeEventsIngestRequestDto request,
        ScannerWebServiceOptions.RuntimeOptions runtimeOptions,
        HttpContext context,
        out IReadOnlyList<RuntimeEventEnvelope> envelopes)
    {
        envelopes = request.Events ?? Array.Empty<RuntimeEventEnvelope>();
        if (envelopes.Count == 0)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid runtime ingest request",
                StatusCodes.Status400BadRequest,
                detail: "events array must include at least one item.");
        }

        if (envelopes.Count > runtimeOptions.MaxBatchSize)
        {
            var extensions = new Dictionary<string, object?>
            {
                ["maxBatchSize"] = runtimeOptions.MaxBatchSize,
                ["eventCount"] = envelopes.Count
            };

            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid runtime ingest request",
                StatusCodes.Status400BadRequest,
                detail: "events array exceeds allowed batch size.",
                extensions: extensions);
        }

        var seenEventIds = new HashSet<string>(StringComparer.Ordinal);
        for (var i = 0; i < envelopes.Count; i++)
        {
            var envelope = envelopes[i];
            if (envelope is null)
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}] must not be null.");
            }

            if (!envelope.IsSupported())
            {
                var extensions = new Dictionary<string, object?>
                {
                    ["schemaVersion"] = envelope.SchemaVersion
                };

                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Unsupported runtime schema version",
                    StatusCodes.Status400BadRequest,
                    detail: "Runtime event schemaVersion is not supported.",
                    extensions: extensions);
            }

            var runtimeEvent = envelope.Event;
            if (runtimeEvent is null)
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}].event must not be null.");
            }

            if (string.IsNullOrWhiteSpace(runtimeEvent.EventId))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}].eventId is required.");
            }

            if (!seenEventIds.Add(runtimeEvent.EventId))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"Duplicate eventId detected within batch ('{runtimeEvent.EventId}').");
            }

            if (string.IsNullOrWhiteSpace(runtimeEvent.Tenant))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}].tenant is required.");
            }

            if (string.IsNullOrWhiteSpace(runtimeEvent.Node))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}].node is required.");
            }

            if (runtimeEvent.Workload is null)
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime ingest request",
                    StatusCodes.Status400BadRequest,
                    detail: $"events[{i}].workload is required.");
            }
        }

        return null;
    }

    private static string NormalizeSegment(string segment)
    {
        if (string.IsNullOrWhiteSpace(segment))
        {
            return "/runtime";
        }

        var trimmed = segment.Trim('/');
        return "/" + trimmed;
    }

    private static IResult Json<T>(T value, int statusCode)
    {
        var payload = JsonSerializer.Serialize(value, SerializerOptions);
        return Results.Content(payload, "application/json", Encoding.UTF8, statusCode);
    }
}