using System.Reflection;
using System.Text.Json;
using Scalar.AspNetCore;
using MyCompany.MyProject.BackendApi.Models;
using System.Security;

// Ensure S8n.Components.Packages assembly is loaded
_ = typeof(S8n.Components.Basics.Calculator).Assembly;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
// Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
builder.Services.AddOpenApi();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
    app.MapScalarApiReference();
}

app.UseHttpsRedirection();

// Component registry endpoint
app.MapGet("/api/components", () =>
{
    var components = new List<ComponentDefinition>();
    var presets = new List<PresetDefinition>();
    
    // Load components from components/ directory
    var componentsPath = Path.Combine(Directory.GetCurrentDirectory(), "..", "components");
    if (!Directory.Exists(componentsPath))
    {
        // Fallback to absolute path from workspace root
        componentsPath = Path.Combine(Directory.GetCurrentDirectory(), "components");
    }
    
    // Load presets from components_user/ directory
    var userComponentsPath = Path.Combine(Directory.GetCurrentDirectory(), "..", "components_user");
    if (!Directory.Exists(userComponentsPath))
    {
        userComponentsPath = Path.Combine(Directory.GetCurrentDirectory(), "components_user");
    }
    
    // Load all JSON files from both directories
    var allPaths = new List<string>();
    if (Directory.Exists(componentsPath)) allPaths.Add(componentsPath);
    if (Directory.Exists(userComponentsPath)) allPaths.Add(userComponentsPath);
    
    foreach (var path in allPaths)
    {
        var jsonFiles = Directory.GetFiles(path, "*.json", SearchOption.AllDirectories);
        foreach (var file in jsonFiles)
        {
            try
            {
                var json = File.ReadAllText(file);
                
                // Try to determine if this is a component or preset by checking for "type" field
                using var doc = JsonDocument.Parse(json);
                var isPreset = doc.RootElement.TryGetProperty("type", out var typeElement) &&
                               typeElement.GetString() == "preset";
                
                if (isPreset)
                {
                    var preset = JsonSerializer.Deserialize<PresetDefinition>(json, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });
                    if (preset != null)
                    {
                        presets.Add(preset);
                    }
                }
                else
                {
                    var component = JsonSerializer.Deserialize<ComponentDefinition>(json, new JsonSerializerOptions
                    {
                        PropertyNameCaseInsensitive = true
                    });
                    if (component != null)
                    {
                        components.Add(component);
                    }
                }
            }
            catch (Exception ex)
            {
                // Log error but continue
                Console.WriteLine($"Error reading component/preset file {file}: {ex.Message}");
            }
        }
    }
    
    // Group presets by baseComponentCode and attach to components
    var presetsByComponent = presets.GroupBy(p => p.BaseComponentCode)
                                    .ToDictionary(g => g.Key, g => g.ToList());
    
    foreach (var component in components)
    {
        if (presetsByComponent.TryGetValue(component.Code, out var componentPresets))
        {
            component.Presets = componentPresets;
        }
    }
    
    return Results.Ok(components);
})
.WithName("GetComponents");

// Runtime execution endpoint
app.MapPost("/api/runtime/execute", async (RuntimeRequest request, ILogger<RuntimeRequest> logger) =>
{
    const int MAX_CLASS_NAME_LENGTH = 500;
    const int MAX_METHOD_NAME_LENGTH = 100;
    
    try
    {
        // Input validation and sanitization
        if (string.IsNullOrWhiteSpace(request.ClassName) || 
            string.IsNullOrWhiteSpace(request.MethodName) ||
            request.ClassName.Length > MAX_CLASS_NAME_LENGTH ||
            request.MethodName.Length > MAX_METHOD_NAME_LENGTH)
        {
            logger.LogWarning("Invalid input parameters received");
            return Results.BadRequest(new RuntimeResponse
            {
                Error = "Invalid class name or method name"
            });
        }

        // Security: Validate class name format to prevent malicious type loading
        if (!IsValidTypeName(request.ClassName))
        {
            logger.LogWarning("Invalid type name format: {ClassName}", request.ClassName);
            return Results.BadRequest(new RuntimeResponse
            {
                Error = "Invalid class name format"
            });
        }

        // Security: Validate method name format
        if (!IsValidMethodName(request.MethodName))
        {
            logger.LogWarning("Invalid method name format: {MethodName}", request.MethodName);
            return Results.BadRequest(new RuntimeResponse
            {
                Error = "Invalid method name format"
            });
        }

        // Get the type from the class name with security restrictions
        var type = GetTypeSafely(request.ClassName);
        if (type == null)
        {
            logger.LogWarning("Class not found: {ClassName}", request.ClassName);
            return Results.NotFound(new RuntimeResponse
            {
                Error = $"Class not found: {request.ClassName}"
            });
        }

        // Security: Verify the type is in allowed assemblies/namespaces
        if (!IsAllowedAssembly(type.Assembly))
        {
            logger.LogWarning("Access to type from disallowed assembly: {Assembly}", type.Assembly.FullName);
            return Results.Forbid();
        }

        // Security: Check if type is instantiable and safe
        if (!IsSafeInstantiableType(type))
        {
            logger.LogWarning("Attempted to instantiate unsafe type: {Type}", type.FullName);
            return Results.BadRequest(new RuntimeResponse
            {
                Error = "Type instantiation is not allowed"
            });
        }

        // Create instance with dependency injection if available
        var instance = CreateInstanceSafely(type);
        if (instance == null)
        {
            logger.LogError("Failed to create instance of: {ClassName}", request.ClassName);
            return Results.BadRequest(new RuntimeResponse
            {
                Error = $"Failed to create instance of: {request.ClassName}"
            });
        }

        // Get the method with security checks
        var method = type.GetMethod(request.MethodName, BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static);
        if (method == null)
        {
            logger.LogWarning("Method not found: {MethodName} in type {Type}", request.MethodName, type.FullName);
            return Results.NotFound(new RuntimeResponse
            {
                Error = $"Method not found: {request.MethodName}"
            });
        }

        // Security: Verify method is safe to execute
        if (!IsSafeExecutableMethod(method))
        {
            logger.LogWarning("Unsafe method attempted: {Method} in type {Type}", method.Name, type.FullName);
            return Results.BadRequest(new RuntimeResponse
            {
                Error = "Method execution is not allowed"
            });
        }

        // Execute method with proper parameter binding
        var result = await ExecuteMethodSafely(instance, method, request.Inputs, logger);

        return Results.Ok(new RuntimeResponse
        {
            Outputs = result
        });
    }
    catch (TargetInvocationException tie) when (tie.InnerException != null)
    {
        logger.LogError(tie.InnerException, "Method execution failed for {ClassName}.{MethodName}", 
            request?.ClassName, request?.MethodName);
        
        return Results.BadRequest(new RuntimeResponse
        {
            Error = tie.InnerException.Message
        });
    }
    catch (SecurityException se)
    {
        logger.LogError(se, "Security violation during execution of {ClassName}.{MethodName}", 
            request?.ClassName, request?.MethodName);
        
        return Results.Forbid();
    }
    catch (Exception ex)
    {
        logger.LogError(ex, "Unexpected error during runtime execution for {ClassName}.{MethodName}", 
            request?.ClassName, request?.MethodName);
        
        return Results.Problem("An unexpected error occurred during execution", statusCode: 500);
    }
})
.WithName("ExecuteRuntime");

// Helper methods for enhanced security and functionality
static bool IsValidTypeName(string typeName)
{
    // Basic validation - only allow alphanumeric characters, dots, underscores, and spaces
    return System.Text.RegularExpressions.Regex.IsMatch(typeName, @"^[a-zA-Z0-9._]+$") &&
           !typeName.Contains("..") && // Prevent path traversal attempts
           !typeName.StartsWith(".") && // Prevent relative paths
           !typeName.EndsWith("."); // Prevent malformed names
}

static bool IsValidMethodName(string methodName)
{
    // Basic validation for method names
    return System.Text.RegularExpressions.Regex.IsMatch(methodName, @"^[a-zA-Z_][a-zA-Z0-9_]*$");
}

static Type? GetTypeSafely(string className)
{
    // First try direct lookup
    var type = Type.GetType(className);
    if (type != null) return type;

    // Search in loaded assemblies with additional safety
    var assemblies = AppDomain.CurrentDomain.GetAssemblies()
        .Where(a => !a.IsDynamic && !a.FullName!.StartsWith("System.Private"))
        .Take(50); // Limit search scope for performance

    foreach (var assembly in assemblies)
    {
        type = assembly.GetType(className);
        if (type != null) return type;
    }

    return null;
}

static bool IsAllowedAssembly(Assembly assembly)
{
    var assemblyName = assembly.GetName().Name;
    
    // Allow only specific assemblies (customize based on your needs)
    var allowedPrefixes = new[] { 
        "S8n.Components.", // Replace with your application namespace
        "MyCompany.MyProject."      // Replace with your library namespaces
    };
    
    return allowedPrefixes.Any(prefix => assemblyName!.StartsWith(prefix));
}

static bool IsSafeInstantiableType(Type type)
{
    // Don't allow instantiation of system types, delegates, interfaces, abstract classes
    return !type.IsInterface && 
           !type.IsAbstract && 
           !type.IsGenericTypeDefinition &&
           !type.IsNotPublic &&
           !type.Namespace!.StartsWith("System.") && // More restrictive than just containing "System"
           !type.Namespace.StartsWith("Microsoft.");
}

static object? CreateInstanceSafely(Type type)
{
    try
    {
        // Use Activator.CreateInstance with proper exception handling
        return Activator.CreateInstance(type, nonPublic: false);
    }
    catch
    {
        return null;
    }
}

static bool IsSafeExecutableMethod(MethodInfo method)
{
    // Don't allow access to potentially dangerous methods
    var dangerousNames = new[] { "GetType", "MemberwiseClone", "Finalize", "Dispose" };
    
    if (dangerousNames.Contains(method.Name, StringComparer.OrdinalIgnoreCase))
        return false;

    // Check if method has dangerous attributes or return types
    var returnType = method.ReturnType;
    if (returnType == typeof(Type))
        return false; // Potential information disclosure

    return true;
}

static async Task<object?> ExecuteMethodSafely(object instance, MethodInfo method, object? inputs, ILogger logger)
{
    var parameters = method.GetParameters();
    object?[] args;

    if (inputs is JsonElement jsonElement)
    {
        args = BindParameters(parameters, jsonElement, logger);
    }
    else
    {
        args = [];
    }

    var result = method.Invoke(instance, args);

    // Handle async methods properly
    if (result is Task taskResult)
    {
        await taskResult.ConfigureAwait(false);
        
        // Extract result from generic Task<T>
        if (taskResult.GetType().IsGenericType)
        {
            var resultProperty = taskResult.GetType().GetProperty("Result");
            if (resultProperty != null)
            {
                return resultProperty.GetValue(taskResult);
            }
        }
        return null; // For non-generic Task
    }

    return result;
}

static object?[] BindParameters(ParameterInfo[] parameters, JsonElement jsonElement, ILogger logger)
{
    var args = new object?[parameters.Length];

    for (int i = 0; i < parameters.Length; i++)
    {
        var param = parameters[i];
        
        if (jsonElement.TryGetProperty(param.Name!, out var property))
        {
            try
            {
                var value = JsonSerializer.Deserialize(property.GetRawText(), param.ParameterType);
                args[i] = value;
            }
            catch (JsonException ex)
            {
                logger.LogError(ex, "Failed to deserialize parameter {ParamName}", param.Name);
                throw new ArgumentException($"Invalid value for parameter '{param.Name}'");
            }
        }
        else if (param.IsOptional)
        {
            args[i] = param.DefaultValue;
        }
        else
        {
            throw new ArgumentException($"Missing required parameter: {param.Name}");
        }
    }

    return args;
}

app.Run();