using System.Collections.Generic;
using System.Collections.Immutable;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using StellaOps.Policy;
using StellaOps.Scanner.WebService.Constants;
using StellaOps.Scanner.WebService.Contracts;
using StellaOps.Scanner.WebService.Infrastructure;
using StellaOps.Scanner.WebService.Security;
using StellaOps.Scanner.WebService.Services;
using StellaOps.Zastava.Core.Contracts;
using RuntimePolicyVerdict = StellaOps.Zastava.Core.Contracts.PolicyVerdict;

namespace StellaOps.Scanner.WebService.Endpoints;

internal static class PolicyEndpoints
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };
    public static void MapPolicyEndpoints(this RouteGroupBuilder apiGroup, string policySegment)
    {
        ArgumentNullException.ThrowIfNull(apiGroup);

        var policyGroup = apiGroup
            .MapGroup(NormalizeSegment(policySegment))
            .WithTags("Policy");

        policyGroup.MapGet("/schema", HandleSchemaAsync)
            .WithName("scanner.policy.schema")
            .Produces(StatusCodes.Status200OK)
            .RequireAuthorization(ScannerPolicies.Reports)
            .WithOpenApi(operation =>
            {
                operation.Summary = "Retrieve the embedded policy JSON schema.";
                operation.Description = "Returns the policy schema (`policy-schema@1`) used to validate YAML or JSON rulesets.";
                return operation;
            });

        policyGroup.MapPost("/diagnostics", HandleDiagnosticsAsync)
            .WithName("scanner.policy.diagnostics")
            .Produces<PolicyDiagnosticsResponseDto>(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status400BadRequest)
            .RequireAuthorization(ScannerPolicies.Reports)
            .WithOpenApi(operation =>
            {
                operation.Summary = "Run policy diagnostics.";
                operation.Description = "Accepts YAML or JSON policy content and returns normalization issues plus recommendations (ignore rules, VEX include/exclude, vendor precedence).";
                return operation;
            });

        policyGroup.MapPost("/preview", HandlePreviewAsync)
            .WithName("scanner.policy.preview")
            .Produces<PolicyPreviewResponseDto>(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status400BadRequest)
            .RequireAuthorization(ScannerPolicies.Reports)
            .WithOpenApi(operation =>
            {
                operation.Summary = "Preview policy impact against findings.";
                operation.Description = "Evaluates the supplied findings against the active or proposed policy, returning diffs, quieted verdicts, and actionable validation messages.";
                return operation;
            });

        policyGroup.MapPost("/runtime", HandleRuntimePolicyAsync)
            .WithName("scanner.policy.runtime")
            .Produces<RuntimePolicyResponseDto>(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status400BadRequest)
            .RequireAuthorization(ScannerPolicies.Reports)
            .WithOpenApi(operation =>
            {
                operation.Summary = "Evaluate runtime policy for digests.";
                operation.Description = "Returns per-image policy verdicts, signature and SBOM metadata, and cache hints for admission controllers.";
                return operation;
            });
    }

    private static IResult HandleSchemaAsync(HttpContext context)
    {
        var schema = PolicySchemaResource.ReadSchemaJson();
        return Results.Text(schema, "application/schema+json", Encoding.UTF8);
    }

    private static IResult HandleDiagnosticsAsync(
        PolicyDiagnosticsRequestDto request,
        TimeProvider timeProvider,
        HttpContext context)
    {
        ArgumentNullException.ThrowIfNull(request);
        ArgumentNullException.ThrowIfNull(timeProvider);

        if (request.Policy is null || string.IsNullOrWhiteSpace(request.Policy.Content))
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid policy diagnostics request",
                StatusCodes.Status400BadRequest,
                detail: "Policy content is required for diagnostics.");
        }

        var format = PolicyDtoMapper.ParsePolicyFormat(request.Policy.Format);
        var binding = PolicyBinder.Bind(request.Policy.Content, format);
        var diagnostics = PolicyDiagnostics.Create(binding, timeProvider);

        var response = new PolicyDiagnosticsResponseDto
        {
            Success = diagnostics.ErrorCount == 0,
            Version = diagnostics.Version,
            RuleCount = diagnostics.RuleCount,
            ErrorCount = diagnostics.ErrorCount,
            WarningCount = diagnostics.WarningCount,
            GeneratedAt = diagnostics.GeneratedAt,
            Issues = diagnostics.Issues.Select(PolicyDtoMapper.ToIssueDto).ToImmutableArray(),
            Recommendations = diagnostics.Recommendations
        };

        return Json(response);
    }

    private static async Task<IResult> HandlePreviewAsync(
        PolicyPreviewRequestDto request,
        PolicyPreviewService previewService,
        HttpContext context,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(request);
        ArgumentNullException.ThrowIfNull(previewService);

        if (string.IsNullOrWhiteSpace(request.ImageDigest))
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid policy preview request",
                StatusCodes.Status400BadRequest,
                detail: "imageDigest is required.");
        }

        if (!request.ImageDigest.Contains(':', StringComparison.Ordinal))
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid policy preview request",
                StatusCodes.Status400BadRequest,
                detail: "imageDigest must include algorithm prefix (e.g. sha256:...).");
        }

        if (request.Findings is not null)
        {
            var missingIds = request.Findings.Any(f => string.IsNullOrWhiteSpace(f.Id));
            if (missingIds)
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid policy preview request",
                    StatusCodes.Status400BadRequest,
                    detail: "All findings must include an id value.");
            }
        }

        var domainRequest = PolicyDtoMapper.ToDomain(request);
        var response = await previewService.PreviewAsync(domainRequest, cancellationToken).ConfigureAwait(false);
        var payload = PolicyDtoMapper.ToDto(response);
        return Json(payload);
    }

    private static async Task<IResult> HandleRuntimePolicyAsync(
        RuntimePolicyRequestDto request,
        IRuntimePolicyService runtimePolicyService,
        HttpContext context,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(request);
        ArgumentNullException.ThrowIfNull(runtimePolicyService);

        if (request.Images is null || request.Images.Count == 0)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid runtime policy request",
                StatusCodes.Status400BadRequest,
                detail: "images collection must include at least one digest.");
        }

        var normalizedImages = new List<string>();
        var seen = new HashSet<string>(StringComparer.Ordinal);
        foreach (var image in request.Images)
        {
            if (string.IsNullOrWhiteSpace(image))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime policy request",
                    StatusCodes.Status400BadRequest,
                    detail: "Image digests must be non-empty.");
            }

            var trimmed = image.Trim();
            if (!trimmed.Contains(':', StringComparison.Ordinal))
            {
                return ProblemResultFactory.Create(
                    context,
                    ProblemTypes.Validation,
                    "Invalid runtime policy request",
                    StatusCodes.Status400BadRequest,
                    detail: "Image digests must include an algorithm prefix (e.g. sha256:...).");
            }

            if (seen.Add(trimmed))
            {
                normalizedImages.Add(trimmed);
            }
        }

        if (normalizedImages.Count == 0)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid runtime policy request",
                StatusCodes.Status400BadRequest,
                detail: "images collection must include at least one unique digest.");
        }

        var namespaceValue = string.IsNullOrWhiteSpace(request.Namespace) ? null : request.Namespace.Trim();
        var normalizedLabels = new Dictionary<string, string>(StringComparer.Ordinal);
        if (request.Labels is not null)
        {
            foreach (var pair in request.Labels)
            {
                if (string.IsNullOrWhiteSpace(pair.Key))
                {
                    continue;
                }

                var key = pair.Key.Trim();
                var value = pair.Value?.Trim() ?? string.Empty;
                normalizedLabels[key] = value;
            }
        }

        var evaluationRequest = new RuntimePolicyEvaluationRequest(
            namespaceValue,
            new ReadOnlyDictionary<string, string>(normalizedLabels),
            normalizedImages);

        var evaluation = await runtimePolicyService.EvaluateAsync(evaluationRequest, cancellationToken).ConfigureAwait(false);

        var resultPayload = MapRuntimePolicyResponse(evaluation);
        return Json(resultPayload);
    }

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

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

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

    private static RuntimePolicyResponseDto MapRuntimePolicyResponse(RuntimePolicyEvaluationResult evaluation)
    {
        var results = new Dictionary<string, RuntimePolicyImageResponseDto>(evaluation.Results.Count, StringComparer.Ordinal);
        foreach (var pair in evaluation.Results)
        {
            var decision = pair.Value;
            RuntimePolicyRekorDto? rekor = null;
            if (decision.Rekor is not null)
            {
                rekor = new RuntimePolicyRekorDto
                {
                    Uuid = decision.Rekor.Uuid,
                    Url = decision.Rekor.Url,
                    Verified = decision.Rekor.Verified
                };
            }

            string? metadata = null;
            if (decision.Metadata is not null && decision.Metadata.Count > 0)
            {
                metadata = JsonSerializer.Serialize(decision.Metadata, SerializerOptions);
            }

            results[pair.Key] = new RuntimePolicyImageResponseDto
            {
                PolicyVerdict = ToCamelCase(decision.PolicyVerdict),
                Signed = decision.Signed,
                HasSbomReferrers = decision.HasSbomReferrers,
                HasSbomLegacy = decision.HasSbomReferrers,
                Reasons = decision.Reasons.ToArray(),
                Rekor = rekor,
                Confidence = Math.Round(decision.Confidence, 6, MidpointRounding.AwayFromZero),
                Quieted = decision.Quieted,
                QuietedBy = decision.QuietedBy,
                Metadata = metadata
            };
        }

        return new RuntimePolicyResponseDto
        {
            TtlSeconds = evaluation.TtlSeconds,
            ExpiresAtUtc = evaluation.ExpiresAtUtc,
            PolicyRevision = evaluation.PolicyRevision,
            Results = results
        };
    }

    private static string ToCamelCase(RuntimePolicyVerdict verdict)
        => verdict switch
        {
            RuntimePolicyVerdict.Pass => "pass",
            RuntimePolicyVerdict.Warn => "warn",
            RuntimePolicyVerdict.Fail => "fail",
            RuntimePolicyVerdict.Error => "error",
            _ => "unknown"
        };
}