// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (c) StellaOps

using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using StellaOps.Scanner.Reachability.Stack;
using StellaOps.Scanner.WebService.Constants;
using StellaOps.Scanner.WebService.Contracts;
using StellaOps.Scanner.WebService.Infrastructure;
using StellaOps.Scanner.WebService.Security;

namespace StellaOps.Scanner.WebService.Endpoints;

/// <summary>
/// Endpoints for three-layer reachability stack analysis.
/// </summary>
internal static class ReachabilityStackEndpoints
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
        Converters = { new JsonStringEnumConverter() }
    };

    /// <summary>
    /// Maps reachability stack endpoints under /reachability.
    /// </summary>
    public static void MapReachabilityStackEndpoints(this RouteGroupBuilder apiGroup)
    {
        ArgumentNullException.ThrowIfNull(apiGroup);

        var reachabilityGroup = apiGroup.MapGroup("/reachability");

        // GET /reachability/{findingId}/stack - Full 3-layer breakdown
        reachabilityGroup.MapGet("/{findingId}/stack", HandleGetStackAsync)
            .WithName("scanner.reachability.stack")
            .WithTags("ReachabilityStack")
            .Produces<ReachabilityStackDto>(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status400BadRequest)
            .Produces(StatusCodes.Status404NotFound)
            .RequireAuthorization(ScannerPolicies.ScansRead);

        // GET /reachability/{findingId}/stack/layer/{layerNumber} - Single layer detail
        reachabilityGroup.MapGet("/{findingId}/stack/layer/{layerNumber:int}", HandleGetLayerAsync)
            .WithName("scanner.reachability.stack.layer")
            .WithTags("ReachabilityStack")
            .Produces(StatusCodes.Status200OK)
            .Produces(StatusCodes.Status400BadRequest)
            .Produces(StatusCodes.Status404NotFound)
            .RequireAuthorization(ScannerPolicies.ScansRead);
    }

    private static async Task<IResult> HandleGetStackAsync(
        string findingId,
        IReachabilityStackRepository? stackRepository,
        HttpContext context,
        CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(findingId))
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid finding identifier",
                StatusCodes.Status400BadRequest,
                detail: "Finding identifier is required.");
        }

        // If no repository is registered, return a stub implementation for now
        if (stackRepository is null)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.NotImplemented,
                "Reachability stack not available",
                StatusCodes.Status501NotImplemented,
                detail: "Reachability stack analysis is not yet implemented for this deployment.");
        }

        var stack = await stackRepository.TryGetByFindingIdAsync(findingId, cancellationToken)
            .ConfigureAwait(false);

        if (stack is null)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.NotFound,
                "Reachability stack not found",
                StatusCodes.Status404NotFound,
                detail: $"No reachability stack found for finding '{findingId}'.");
        }

        var dto = MapToDto(stack);
        return Json(dto, StatusCodes.Status200OK);
    }

    private static async Task<IResult> HandleGetLayerAsync(
        string findingId,
        int layerNumber,
        IReachabilityStackRepository? stackRepository,
        HttpContext context,
        CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(findingId))
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid finding identifier",
                StatusCodes.Status400BadRequest,
                detail: "Finding identifier is required.");
        }

        if (layerNumber < 1 || layerNumber > 3)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.Validation,
                "Invalid layer number",
                StatusCodes.Status400BadRequest,
                detail: "Layer number must be 1, 2, or 3.");
        }

        if (stackRepository is null)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.NotImplemented,
                "Reachability stack not available",
                StatusCodes.Status501NotImplemented,
                detail: "Reachability stack analysis is not yet implemented for this deployment.");
        }

        var stack = await stackRepository.TryGetByFindingIdAsync(findingId, cancellationToken)
            .ConfigureAwait(false);

        if (stack is null)
        {
            return ProblemResultFactory.Create(
                context,
                ProblemTypes.NotFound,
                "Reachability stack not found",
                StatusCodes.Status404NotFound,
                detail: $"No reachability stack found for finding '{findingId}'.");
        }

        object layerDto = layerNumber switch
        {
            1 => MapLayer1ToDto(stack.StaticCallGraph),
            2 => MapLayer2ToDto(stack.BinaryResolution),
            3 => MapLayer3ToDto(stack.RuntimeGating),
            _ => throw new InvalidOperationException("Invalid layer number")
        };

        return Json(layerDto, StatusCodes.Status200OK);
    }

    private static ReachabilityStackDto MapToDto(ReachabilityStack stack)
    {
        return new ReachabilityStackDto(
            Id: stack.Id,
            FindingId: stack.FindingId,
            Symbol: MapSymbolToDto(stack.Symbol),
            Layer1: MapLayer1ToDto(stack.StaticCallGraph),
            Layer2: MapLayer2ToDto(stack.BinaryResolution),
            Layer3: MapLayer3ToDto(stack.RuntimeGating),
            Verdict: stack.Verdict.ToString(),
            Explanation: stack.Explanation,
            AnalyzedAt: stack.AnalyzedAt);
    }

    private static VulnerableSymbolDto MapSymbolToDto(VulnerableSymbol symbol)
    {
        return new VulnerableSymbolDto(
            Name: symbol.Name,
            Library: symbol.Library,
            Version: symbol.Version,
            VulnerabilityId: symbol.VulnerabilityId,
            Type: symbol.Type.ToString());
    }

    private static ReachabilityLayer1Dto MapLayer1ToDto(ReachabilityLayer1 layer)
    {
        return new ReachabilityLayer1Dto(
            IsReachable: layer.IsReachable,
            Confidence: layer.Confidence.ToString(),
            PathCount: layer.Paths.Length,
            EntrypointCount: layer.ReachingEntrypoints.Length,
            AnalysisMethod: layer.AnalysisMethod,
            Paths: layer.Paths.Select(MapCallPathToDto).ToList());
    }

    private static ReachabilityLayer2Dto MapLayer2ToDto(ReachabilityLayer2 layer)
    {
        return new ReachabilityLayer2Dto(
            IsResolved: layer.IsResolved,
            Confidence: layer.Confidence.ToString(),
            Reason: layer.Reason,
            Resolution: layer.Resolution is not null ? MapResolutionToDto(layer.Resolution) : null,
            LoaderRule: layer.AppliedRule is not null ? MapLoaderRuleToDto(layer.AppliedRule) : null);
    }

    private static ReachabilityLayer3Dto MapLayer3ToDto(ReachabilityLayer3 layer)
    {
        return new ReachabilityLayer3Dto(
            IsGated: layer.IsGated,
            Outcome: layer.Outcome.ToString(),
            Confidence: layer.Confidence.ToString(),
            Conditions: layer.Conditions.Select(MapGatingConditionToDto).ToList());
    }

    private static CallPathDto MapCallPathToDto(CallPath path)
    {
        return new CallPathDto(
            Entrypoint: path.Entrypoint is not null ? MapEntrypointToDto(path.Entrypoint) : null,
            Sites: path.Sites.Select(MapCallSiteToDto).ToList(),
            Confidence: path.Confidence,
            HasConditionals: path.HasConditionals);
    }

    private static EntrypointDto MapEntrypointToDto(Entrypoint entrypoint)
    {
        return new EntrypointDto(
            Name: entrypoint.Name,
            Type: entrypoint.Type.ToString(),
            File: entrypoint.Location,
            Description: entrypoint.Description);
    }

    private static CallSiteDto MapCallSiteToDto(CallSite site)
    {
        return new CallSiteDto(
            Method: site.MethodName,
            Type: site.ClassName,
            File: site.FileName,
            Line: site.LineNumber,
            CallType: site.Type.ToString());
    }

    private static SymbolResolutionDto MapResolutionToDto(SymbolResolution resolution)
    {
        return new SymbolResolutionDto(
            SymbolName: resolution.SymbolName,
            ResolvedLibrary: resolution.ResolvedLibrary,
            ResolvedVersion: resolution.ResolvedVersion,
            SymbolVersion: resolution.SymbolVersion,
            Method: resolution.Method.ToString());
    }

    private static LoaderRuleDto MapLoaderRuleToDto(LoaderRule rule)
    {
        return new LoaderRuleDto(
            Type: rule.Type.ToString(),
            Value: rule.Value,
            Source: rule.Source);
    }

    private static GatingConditionDto MapGatingConditionToDto(GatingCondition condition)
    {
        return new GatingConditionDto(
            Type: condition.Type.ToString(),
            Description: condition.Description,
            ConfigKey: condition.ConfigKey,
            EnvVar: condition.EnvVar,
            IsBlocking: condition.IsBlocking,
            Status: condition.Status.ToString());
    }

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

/// <summary>
/// Repository interface for reachability stack data.
/// </summary>
public interface IReachabilityStackRepository
{
    /// <summary>
    /// Gets a reachability stack by finding ID.
    /// </summary>
    Task<ReachabilityStack?> TryGetByFindingIdAsync(string findingId, CancellationToken ct);

    /// <summary>
    /// Stores a reachability stack.
    /// </summary>
    Task StoreAsync(ReachabilityStack stack, CancellationToken ct);
}