using System.Globalization;
using Jint.Native.Object;
using Jint.Native.RegExp;
using Jint.Runtime;
using Jint.Runtime.Descriptors;

namespace Jint.Native.Iterator
{
    internal class IteratorInstance : ObjectInstance
    {
        private readonly IEnumerator<JsValue> _enumerable;

        protected IteratorInstance(Engine engine)
            : this(engine, Enumerable.Empty<JsValue>())
        {
        }

        public IteratorInstance(
            Engine engine,
            IEnumerable<JsValue> enumerable) : base(engine)
        {
            _enumerable = enumerable.GetEnumerator();
            _prototype = engine.Realm.Intrinsics.ArrayIteratorPrototype;
       }

        public override object ToObject()
        {
            ExceptionHelper.ThrowNotImplementedException();
            return null;
        }

        public virtual bool TryIteratorStep(out ObjectInstance nextItem)
        {
            if (_enumerable.MoveNext())
            {
                nextItem = new ValueIteratorPosition(_engine, _enumerable.Current);
                return true;
            }

            nextItem = ValueIteratorPosition.Done(_engine);
            return false;
        }

        public virtual void Close(CompletionType completion)
        {
        }

        /// <summary>
        /// https://tc39.es/ecma262/#sec-createiterresultobject
        /// </summary>
        private ObjectInstance CreateIterResultObject(JsValue value, bool done)
        {
            return new IteratorResult(_engine, value, done ? JsBoolean.True :  JsBoolean.False);
        }

        internal sealed class KeyValueIteratorPosition : ObjectInstance
        {
            internal static ObjectInstance Done(Engine engine) => new KeyValueIteratorPosition(engine, null, null);

            public KeyValueIteratorPosition(Engine engine, JsValue? key, JsValue? value) : base(engine)
            {
                var done = ReferenceEquals(null, key) && ReferenceEquals(null, value);
                if (!done)
                {
                    var arrayInstance = engine.Realm.Intrinsics.Array.ArrayCreate(2);
                    arrayInstance.SetIndexValue(0, key!, false);
                    arrayInstance.SetIndexValue(1, value!, false);
                    SetProperty("value", new PropertyDescriptor(arrayInstance, PropertyFlag.AllForbidden));
                }
                SetProperty("done", done ? PropertyDescriptor.AllForbiddenDescriptor.BooleanTrue : PropertyDescriptor.AllForbiddenDescriptor.BooleanFalse);
            }
        }

        internal sealed class ValueIteratorPosition : ObjectInstance
        {
            internal static ObjectInstance Done(Engine engine, JsValue? value = null)
                => new ValueIteratorPosition(engine, value ?? Undefined, true);

            public ValueIteratorPosition(Engine engine, JsValue value, bool? done = null) : base(engine)
            {
                if (value is not null)
                {
                    SetProperty("value", new PropertyDescriptor(value, PropertyFlag.AllForbidden));
                }
                SetProperty("done", new PropertyDescriptor(done ?? value is null, PropertyFlag.AllForbidden));
            }
        }

        internal sealed class ObjectIterator : IteratorInstance
        {
            private readonly ObjectInstance _target;
            private readonly ICallable _nextMethod;

            public ObjectIterator(ObjectInstance target) : base(target.Engine)
            {
                _target = target;
                if (target.Get(CommonProperties.Next, target) is not ICallable callable)
                {
                    ExceptionHelper.ThrowTypeError(target.Engine.Realm);
                    return;
                }
                _nextMethod = callable;
            }

            public override bool TryIteratorStep(out ObjectInstance result)
            {
                result = IteratorNext();

                var done = result.Get(CommonProperties.Done);
                if (!done.IsUndefined() && TypeConverter.ToBoolean(done))
                {
                    return false;
                }

                return true;
            }

            private ObjectInstance IteratorNext()
            {
                var jsValue = _nextMethod.Call(_target, Arguments.Empty);
                var instance = jsValue as ObjectInstance;
                if (instance is null)
                {
                    ExceptionHelper.ThrowTypeError(_target.Engine.Realm, "Iterator result " + jsValue + " is not an object");
                }

                return instance;
            }

            public override void Close(CompletionType completion)
            {
                if (!_target.TryGetValue(CommonProperties.Return, out var func)
                    || func.IsNullOrUndefined())
                {
                    return;
                }

                var callable = func as ICallable;
                if (callable is null)
                {
                    ExceptionHelper.ThrowTypeError(_target.Engine.Realm, func + " is not a function");
                }

                var innerResult = Undefined;
                try
                {
                    innerResult = callable.Call(_target, Arguments.Empty);
                }
                catch
                {
                    if (completion != CompletionType.Throw)
                    {
                        throw;
                    }
                }
                if (completion != CompletionType.Throw && !innerResult.IsObject())
                {
                    ExceptionHelper.ThrowTypeError(_target.Engine.Realm, "Iterator returned non-object");
                }
            }
        }

        internal sealed class StringIterator : IteratorInstance
        {
            private readonly TextElementEnumerator _iterator;

            public StringIterator(Engine engine, string str) : base(engine)
            {
                _iterator = StringInfo.GetTextElementEnumerator(str);
            }

            public override bool TryIteratorStep(out ObjectInstance nextItem)
            {
                if (_iterator.MoveNext())
                {
                    nextItem = new ValueIteratorPosition(_engine, (string) _iterator.Current);
                    return true;
                }

                nextItem = KeyValueIteratorPosition.Done(_engine);
                return false;
            }
        }

        internal sealed class RegExpStringIterator : IteratorInstance
        {
            private readonly RegExpInstance _iteratingRegExp;
            private readonly string _s;
            private readonly bool _global;
            private readonly bool _unicode;

            private bool _done;

            public RegExpStringIterator(Engine engine, ObjectInstance iteratingRegExp, string iteratedString, bool global, bool unicode) : base(engine)
            {
                var r = iteratingRegExp as RegExpInstance;
                if (r is null)
                {
                    ExceptionHelper.ThrowTypeError(engine.Realm);
                }

                _iteratingRegExp = r;
                _s = iteratedString;
                _global = global;
                _unicode = unicode;
            }

            public override bool TryIteratorStep(out ObjectInstance nextItem)
            {
                if (_done)
                {
                    nextItem = CreateIterResultObject(Undefined, true);
                    return false;
                }

                var match = RegExpPrototype.RegExpExec(_iteratingRegExp, _s);
                if (match.IsNull())
                {
                    _done = true;
                    nextItem = CreateIterResultObject(Undefined, true);
                    return false;
                }

                if (_global)
                {
                    var macthStr = TypeConverter.ToString(match.Get(JsString.NumberZeroString));
                    if (macthStr == "")
                    {
                        var thisIndex = TypeConverter.ToLength(_iteratingRegExp.Get(RegExpInstance.PropertyLastIndex));
                        var nextIndex = thisIndex + 1;
                        _iteratingRegExp.Set(RegExpInstance.PropertyLastIndex, nextIndex, true);
                    }
                }
                else
                {
                    _done = true;
                }

                nextItem = CreateIterResultObject(match, false);
                return true;
            }
        }
    }
}