using System.Dynamic;
using System.Globalization;
using System.Reflection;
using Jint.Native;
using Jint.Native.Object;
using Jint.Runtime;
using Jint.Runtime.Interop;
using Jint.Runtime.Debugger;
using Jint.Runtime.Descriptors;
using Jint.Runtime.Modules;

namespace Jint
{
    public delegate JsValue? MemberAccessorDelegate(Engine engine, object target, string member);

    public delegate ObjectInstance? WrapObjectDelegate(Engine engine, object target);

    public delegate bool ExceptionHandlerDelegate(Exception exception);

    public class Options
    {
        internal List<Action<Engine>> _configurations { get; } = new();

        /// <summary>
        /// Execution constraints for the engine.
        /// </summary>
        public ConstraintOptions Constraints { get; } = new();

        /// <summary>
        /// CLR interop related options.
        /// </summary>
        public InteropOptions Interop { get; } = new();

        /// <summary>
        /// Debugger configuration.
        /// </summary>
        public DebuggerOptions Debugger { get; } = new();

        /// <summary>
        /// Host options.
        /// </summary>
        internal HostOptions Host { get; } = new();

        /// <summary>
        /// Module options
        /// </summary>
        public ModuleOptions Modules { get; } = new();

        /// <summary>
        /// Whether the code should be always considered to be in strict mode. Can improve performance.
        /// </summary>
        public bool Strict { get; set; }

        /// <summary>
        /// The culture the engine runs on, defaults to current culture.
        /// </summary>
        public CultureInfo Culture { get; set; } = CultureInfo.CurrentCulture;

        /// <summary>
        /// The time zone the engine runs on, defaults to local.
        /// </summary>
        public TimeZoneInfo TimeZone { get; set; } = TimeZoneInfo.Local;

        /// <summary>
        /// Reference resolver allows customizing behavior for reference resolving. This can be useful in cases where
        /// you want to ignore long chain of property accesses that might throw if anything is null or undefined.
        /// An example of such is <code>var a = obj.field.subField.value</code>. Custom resolver could accept chain to return
        /// null/undefined on first occurrence.
        /// </summary>
        public IReferenceResolver ReferenceResolver { get; set; } = DefaultReferenceResolver.Instance;

        /// <summary>
        /// Called by the <see cref="Engine"/> instance that loads this <see cref="Options" />
        /// once it is loaded.
        /// </summary>
        internal void Apply(Engine engine)
        {
            foreach (var configuration in _configurations)
            {
                configuration?.Invoke(engine);
            }

            // add missing bits if needed
            if (Interop.Enabled)
            {
                engine.Realm.GlobalObject.SetProperty("System",
                    new PropertyDescriptor(new NamespaceReference(engine, "System"), PropertyFlag.AllForbidden));
                engine.Realm.GlobalObject.SetProperty("importNamespace", new PropertyDescriptor(new ClrFunctionInstance(
                        engine,
                        "importNamespace",
                        (thisObj, arguments) =>
                            new NamespaceReference(engine, TypeConverter.ToString(arguments.At(0)))),
                    PropertyFlag.AllForbidden));
            }

            if (Interop.ExtensionMethodTypes.Count > 0)
            {
                AttachExtensionMethodsToPrototypes(engine);
            }

            if (Modules.RegisterRequire)
            {
                // Node js like loading of modules
                engine.Realm.GlobalObject.SetProperty("require", new PropertyDescriptor(new ClrFunctionInstance(
                        engine,
                        "require",
                        (thisObj, arguments) =>
                        {
                            var specifier = TypeConverter.ToString(arguments.At(0));
                            return engine.ImportModule(specifier);
                        }),
                    PropertyFlag.AllForbidden));
            }

            engine.ModuleLoader = Modules.ModuleLoader;

            // ensure defaults
            engine.ClrTypeConverter ??= new DefaultTypeConverter(engine);
        }

        private static void AttachExtensionMethodsToPrototypes(Engine engine)
        {
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.Array.PrototypeObject, typeof(Array));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.Boolean.PrototypeObject, typeof(bool));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.Date.PrototypeObject, typeof(DateTime));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.Number.PrototypeObject, typeof(double));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.Object.PrototypeObject, typeof(ExpandoObject));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.RegExp.PrototypeObject, typeof(System.Text.RegularExpressions.Regex));
            AttachExtensionMethodsToPrototype(engine, engine.Realm.Intrinsics.String.PrototypeObject, typeof(string));
        }

        private static void AttachExtensionMethodsToPrototype(Engine engine, ObjectInstance prototype, Type objectType)
        {
            if (!engine._extensionMethods.TryGetExtensionMethods(objectType, out var methods))
            {
                return;
            }

            foreach (var overloads in methods.GroupBy(x => x.Name))
            {
                PropertyDescriptor CreateMethodInstancePropertyDescriptor(ClrFunctionInstance? function)
                {
                    var instance = function is null
                        ? new MethodInfoFunctionInstance(engine, MethodDescriptor.Build(overloads.ToList()))
                        : new MethodInfoFunctionInstance(engine, MethodDescriptor.Build(overloads.ToList()), function);

                    return new PropertyDescriptor(instance, PropertyFlag.AllForbidden);
                }

                JsValue key = overloads.Key;
                PropertyDescriptor? descriptorWithFallback = null;
                PropertyDescriptor? descriptorWithoutFallback = null;

                if (prototype.HasOwnProperty(key) &&
                    prototype.GetOwnProperty(key).Value is ClrFunctionInstance clrFunctionInstance)
                {
                    descriptorWithFallback = CreateMethodInstancePropertyDescriptor(clrFunctionInstance);
                    prototype.SetOwnProperty(key, descriptorWithFallback);
                }
                else
                {
                    descriptorWithoutFallback = CreateMethodInstancePropertyDescriptor(null);
                    prototype.SetOwnProperty(key, descriptorWithoutFallback);
                }

                // make sure we register both lower case and upper case
                if (char.IsUpper(overloads.Key[0]))
                {
                    key = char.ToLower(overloads.Key[0]) + overloads.Key.Substring(1);

                    if (prototype.HasOwnProperty(key) &&
                        prototype.GetOwnProperty(key).Value is ClrFunctionInstance lowerclrFunctionInstance)
                    {
                        descriptorWithFallback ??= CreateMethodInstancePropertyDescriptor(lowerclrFunctionInstance);
                        prototype.SetOwnProperty(key, descriptorWithFallback);
                    }
                    else
                    {
                        descriptorWithoutFallback ??= CreateMethodInstancePropertyDescriptor(null);
                        prototype.SetOwnProperty(key, descriptorWithoutFallback);
                    }
                }
            }
        }
    }

    public class DebuggerOptions
    {
        /// <summary>
        /// Whether debugger functionality is enabled, defaults to false.
        /// </summary>
        public bool Enabled { get; set; }

        /// <summary>
        /// Configures the statement handling strategy, defaults to Ignore.
        /// </summary>
        public DebuggerStatementHandling StatementHandling { get; set; } = DebuggerStatementHandling.Ignore;

        /// <summary>
        /// Configures the step mode used when entering the script.
        /// </summary>
        public StepMode InitialStepMode { get; set; } = StepMode.None;
    }

    public class InteropOptions
    {
        /// <summary>
        /// Whether accessing CLR and it's types and methods is allowed from JS code, defaults to false.
        /// </summary>
        public bool Enabled { get; set; }

        /// <summary>
        /// Whether to expose <see cref="object.GetType"></see> which can allow bypassing allow lists and open a way to reflection.
        /// Defaults to false.
        /// </summary>
        public bool AllowGetType { get; set; }

        /// <summary>
        /// Whether Jint should allow wrapping objects from System.Reflection namespace.
        /// Defaults to false.
        /// </summary>
        public bool AllowSystemReflection { get; set; }

        /// <summary>
        /// Whether writing to CLR objects is allowed (set properties), defaults to true.
        /// </summary>
        public bool AllowWrite { get; set; } = true;

        /// <summary>
        /// Whether operator overloading resolution is allowed, defaults to false.
        /// </summary>
        public bool AllowOperatorOverloading { get; set; }

        /// <summary>
        /// Types holding extension methods that should be considered when resolving methods.
        /// </summary>
        public List<Type> ExtensionMethodTypes { get; } = new();

        /// <summary>
        /// Object converters to try when build-in conversions.
        /// </summary>
        public List<IObjectConverter> ObjectConverters { get; } = new();

        /// <summary>
        /// Whether identity map is persisted for object wrappers in order to maintain object identity.
        /// Defaults to true.
        /// </summary>
        public bool TrackObjectWrapperIdentity { get; set; } = true;

        /// <summary>
        /// If no known type could be guessed, objects are by default wrapped as an
        /// ObjectInstance using class ObjectWrapper. This function can be used to
        /// change the behavior.
        /// </summary>
        public WrapObjectDelegate WrapObjectHandler { get; set; } = static (engine, target) =>
        {
            // check global cache, have we already wrapped the value?
            if (engine._objectWrapperCache.TryGetValue(target, out var wrapped))
            {
                return wrapped;
            }

            wrapped = new ObjectWrapper(engine, target);
            if (engine.Options.Interop.TrackObjectWrapperIdentity)
            {
                engine._objectWrapperCache.Add(target, wrapped);
            }
            return wrapped;
        };

        /// <summary>
        ///
        /// </summary>
        public MemberAccessorDelegate MemberAccessor { get; set; } = static (engine, target, member) => null;

        /// <summary>
        /// Exceptions that thrown from CLR code are converted to JavaScript errors and
        /// can be used in at try/catch statement. By default these exceptions are bubbled
        /// to the CLR host and interrupt the script execution. If handler returns true these exceptions are converted
        /// to JS errors that can be caught by the script.
        /// </summary>
        public ExceptionHandlerDelegate ExceptionHandler { get; set; } = static exception => false;

        /// <summary>
        /// Assemblies to allow scripts to call CLR types directly like <example>System.IO.File</example>.
        /// </summary>
        public List<Assembly> AllowedAssemblies { get; set; } = new();

        /// <summary>
        /// Type and member resolving strategy, which allows filtering allowed members and configuring member
        /// name matching comparison.
        /// </summary>
        /// <remarks>
        /// As this object holds caching state same instance should be shared between engines, if possible.
        /// </remarks>
        public TypeResolver TypeResolver { get; set; } = TypeResolver.Default;

        /// <summary>
        /// When writing values to CLR objects, how should JS values be coerced to CLR types.
        /// Defaults to only coercing to string values when writing to string targets.
        /// </summary>
        public ValueCoercionType ValueCoercion { get; set; } = ValueCoercionType.String;

        /// <summary>
        /// Strategy to create a CLR object to hold converted <see cref="ObjectInstance"/>.
        /// </summary>
        public Func<ObjectInstance, IDictionary<string, object>> CreateClrObject = _ => new ExpandoObject();

        /// <summary>
        /// When not null, is used to serialize any CLR object in an
        /// <see cref="IObjectWrapper"/> passing through 'JSON.stringify'.
        /// </summary>
        public Func<object, string>? SerializeToJson { get; set; }
    }

    /// <summary>
    /// Rules for writing values to CLR fields.
    /// </summary>
    [Flags]
    public enum ValueCoercionType
    {
        /// <summary>
        /// No coercion will be done. If there's no type converter, and error will be thrown.
        /// </summary>
        None = 0,

        /// <summary>
        /// JS coercion using boolean rules "dog" == true, "" == false, 1 == true, 3 == true, 0 == false, { "prop": 1 } == true etc.
        /// </summary>
        Boolean = 1,

        /// <summary>
        /// JS coercion to numbers, false == 0, true == 1. valueOf functions will be used when available for object instances.
        /// Valid against targets of type: Decimal, Double, Int32, Int64.
        /// </summary>
        Number = 2,

        /// <summary>
        /// JS coercion to strings, toString function will be used when available for objects.
        /// </summary>
        String = 4,

        /// <summary>
        /// All coercion rules enabled.
        /// </summary>
        All = Boolean | Number | String
    }

    public class ConstraintOptions
    {
        /// <summary>
        /// Registered constraints.
        /// </summary>
        public List<IConstraint> Constraints { get; } = new();

        /// <summary>
        /// Maximum recursion depth allowed, defaults to -1 (no checks).
        /// </summary>
        public int MaxRecursionDepth { get; set; } = -1;

        /// <summary>
        /// Maximum time a Regex is allowed to run, defaults to 10 seconds.
        /// </summary>
        public TimeSpan RegexTimeout { get; set; } = TimeSpan.FromSeconds(10);

        /// <summary>
        /// The maximum size for JavaScript array, defaults to <see cref="uint.MaxValue"/>.
        /// </summary>
        public uint MaxArraySize { get; set; } = uint.MaxValue;
    }

    /// <summary>
    /// Host related customization, still work in progress.
    /// </summary>
    public class HostOptions
    {
        internal Func<Engine, Host> Factory { get; set; } = _ => new Host();
    }

    /// <summary>
    /// Module related customization
    /// </summary>
    public class ModuleOptions
    {
        /// <summary>
        /// Whether to register require function to engine which will delegate to module loader, defaults to false.
        /// </summary>
        public bool RegisterRequire { get; set; }

        /// <summary>
        /// Module loader implementation, by default exception will be thrown if module loading is not enabled.
        /// </summary>
        public IModuleLoader ModuleLoader { get; set; } = FailFastModuleLoader.Instance;
    }
}