using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

namespace Nullframes.Intrigues.Utils
{
    public class SerializableDictionary { }

    [Serializable]
    public class SerializableDictionary<TKey, TValue> : SerializableDictionary, IDictionary<TKey, TValue>,
        IReadOnlyDictionary<TKey, TValue>, ISerializationCallbackReceiver
    {
        [SerializeField] private List<SerializableKeyValuePair> list = new();

        [Serializable]
        public struct SerializableKeyValuePair
        {
            public TKey Key;
            public TValue Value;

            public SerializableKeyValuePair(TKey key, TValue value)
            {
                Key = key;
                Value = value;
            }
        }

        private Dictionary<TKey, uint> KeyPositions => _keyPositions.Value;
        private Lazy<Dictionary<TKey, uint>> _keyPositions;

        public SerializableDictionary()
        {
            _keyPositions = new Lazy<Dictionary<TKey, uint>>(MakeKeyPositions);
        }

        public SerializableDictionary(IDictionary<TKey, TValue> dictionary)
        {
            _keyPositions = new Lazy<Dictionary<TKey, uint>>(MakeKeyPositions);

            if (dictionary == null) throw new ArgumentException("The passed dictionary is null.");

            foreach (var pair in dictionary) Add(pair.Key, pair.Value);
        }

        private Dictionary<TKey, uint> MakeKeyPositions()
        {
            var numEntries = list.Count;

            var result = new Dictionary<TKey, uint>(numEntries);

            for (var i = 0; i < numEntries; ++i) result[list[i].Key] = (uint)i;

            return result;
        }

        public void OnBeforeSerialize() { }

        public void OnAfterDeserialize()
        {
            // After deserialization, the key positions might be changed
            _keyPositions = new Lazy<Dictionary<TKey, uint>>(MakeKeyPositions);
        }

        #region IDictionary

        public TValue this[TKey key]
        {
            get => list[(int)KeyPositions[key]].Value;
            set
            {
                if (KeyPositions.TryGetValue(key, out var index))
                {
                    list[(int)index] = new SerializableKeyValuePair(list[(int)index].Key, value);
                }
                else
                {
                    KeyPositions[key] = (uint)list.Count;

                    list.Add(new SerializableKeyValuePair(key, value));
                }
            }
        }

        IEnumerable<TKey> IReadOnlyDictionary<TKey, TValue>.Keys => Keys;

        IEnumerable<TValue> IReadOnlyDictionary<TKey, TValue>.Values => Values;

        public ICollection<TKey> Keys => list.Select(tuple => tuple.Key).ToArray();
        public ICollection<TValue> Values => list.Select(tuple => tuple.Value).ToArray();

        public void Add(TKey key, TValue value)
        {
            if (KeyPositions.ContainsKey(key))
            {
                throw new ArgumentException("An element with the same key already exists in the dictionary.");
            }
            else
            {
                KeyPositions[key] = (uint)list.Count;

                list.Add(new SerializableKeyValuePair(key, value));
            }
        }

        public bool ContainsKey(TKey key)
        {
            return KeyPositions.ContainsKey(key);
        }

        public bool Remove(TKey key)
        {
            if (KeyPositions.TryGetValue(key, out var index))
            {
                var kp = KeyPositions;

                kp.Remove(key);

                list.RemoveAt((int)index);

                var numEntries = list.Count;

                for (var i = index; i < numEntries; i++) kp[list[(int)i].Key] = i;

                return true;
            }

            return false;
        }

        public bool TryGetValue(TKey key, out TValue value)
        {
            if (KeyPositions.TryGetValue(key, out var index))
            {
                value = list[(int)index].Value;

                return true;
            }

            value = default;

            return false;
        }

        #endregion

        #region ICollection

        public int Count => list.Count;
        public bool IsReadOnly => false;

        public void Add(KeyValuePair<TKey, TValue> kvp)
        {
            Add(kvp.Key, kvp.Value);
        }

        public void Clear()
        {
            list.Clear();
            KeyPositions.Clear();
        }

        public bool Contains(KeyValuePair<TKey, TValue> kvp)
        {
            return KeyPositions.ContainsKey(kvp.Key);
        }

        public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
        {
            var numKeys = list.Count;

            if (array.Length - arrayIndex < numKeys) throw new ArgumentException("arrayIndex");

            for (var i = 0; i < numKeys; ++i, ++arrayIndex)
            {
                var entry = list[i];

                array[arrayIndex] = new KeyValuePair<TKey, TValue>(entry.Key, entry.Value);
            }
        }

        public bool Remove(KeyValuePair<TKey, TValue> kvp)
        {
            return Remove(kvp.Key);
        }

        #endregion

        #region IEnumerable

        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
        {
            return list.Select(ToKeyValuePair).GetEnumerator();

            KeyValuePair<TKey, TValue> ToKeyValuePair(SerializableKeyValuePair skvp)
            {
                return new KeyValuePair<TKey, TValue>(skvp.Key, skvp.Value);
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        #endregion
    }
}