using Misaki.HighPerformance.LowLevel.Buffer;
using Misaki.HighPerformance.LowLevel.Collections.Contracts;
using Misaki.HighPerformance.LowLevel.Contracts;
using Misaki.HighPerformance.LowLevel.Helpers;
using System.Collections;
using System.Runtime.CompilerServices;

namespace Misaki.HighPerformance.LowLevel.Collections;

public unsafe struct UnsafeHashMap<TKey, TValue> : IUnsafeCollection<KeyValuePair<TKey, TValue>>
    where TKey : unmanaged, IEquatable<TKey> where TValue : unmanaged
{
    public struct Enumerator : IEnumerator<KeyValuePair<TKey, TValue>>
    {
        internal HashMapHelper<TKey>.Enumerator _enumerator;

        public Enumerator(HashMapHelper<TKey>* data)
        {
            _enumerator = new HashMapHelper<TKey>.Enumerator(data);
        }

        /// <summary>
        /// The current key-value pair.
        /// </summary>
        /// <value>The current key-value pair.</value>
        public KeyValuePair<TKey, TValue> Current
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _enumerator.GetCurrent<TValue>();
        }

        /// <summary>
        /// Gets the element at the current position of the enumerator in the container.
        /// </summary>
        object IEnumerator.Current => Current;

        /// <summary>
        /// Advances the enumerator to the next key-value pair.
        /// </summary>
        /// <returns>True if <see cref="Current"/> is valid to read after the call.</returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool MoveNext() => _enumerator.MoveNext();

        /// <summary>
        /// Resets the enumerator to its initial state.
        /// </summary>
        public void Reset() => _enumerator.Reset();

        /// <summary>
        /// Does nothing.
        /// </summary>
        public void Dispose()
        {
        }
    }

    private HashMapHelper<TKey> _hashMap;

    public readonly int Count => _hashMap.Count;
    public readonly int Capacity => _hashMap.Capacity;
    public readonly bool IsCreated => _hashMap.IsCreated;

    /// <summary>
    /// Gets and sets values by key.
    /// </summary>
    /// <remarks>Getting a key that is not present will throw. Setting a key that is not already present will add the key.</remarks>
    /// <param name="key">The key to look up.</param>
    /// <value>The value associated with the key.</value>
    /// <exception cref="ArgumentException">For getting, thrown if the key was not present.</exception>
    public TValue this[TKey key]
    {
        get
        {
            if (!_hashMap.TryGetValue<TValue>(key, out var result))
            {
                throw new ArgumentException($"Key: {key} is not present.");
            }

            return result;
        }

        set
        {
            var idx = _hashMap.Find(key);
            if (-1 != idx)
            {
                UnsafeUtilities.WriteArrayElement(_hashMap.Buffer, idx, value);
                return;
            }

            TryAdd(key, value);
        }
    }

    public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() => new Enumerator((HashMapHelper<TKey>*)UnsafeUtilities.AddressOf(ref _hashMap));
    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    public UnsafeHashMap(int capacity, ref AllocationHandle handle, AllocationOption allocationOption = AllocationOption.None)
    {
        _hashMap = new HashMapHelper<TKey>(capacity, sizeof(TValue), HashMapHelper<TKey>.MINIMAL_CAPACITY, ref handle, allocationOption);
    }

    public UnsafeHashMap(int capacity, Allocator allocator, AllocationOption allocationOption = AllocationOption.None)
        : this(capacity, ref AllocationManager.GetAllocationHandle(allocator), allocationOption)
    {
    }

    /// <summary>
    /// Adds a new key-value pair.
    /// </summary>
    /// <remarks>If the key is already present, this method returns false without modifying the hash map.</remarks>
    /// <param name="key">The key to add.</param>
    /// <param name="item">The value to add.</param>
    /// <returns>True if the key-value pair was added.</returns>
    public bool TryAdd(TKey key, TValue item)
    {
        var idx = _hashMap.TryAdd(key);
        if (idx != -1)
        {
            UnsafeUtilities.WriteArrayElement(_hashMap.Buffer, idx, item);
            return true;
        }

        return false;
    }

    /// <summary>
    /// Adds a new key-value pair.
    /// </summary>
    /// <remarks>If the key is already present, this method throws without modifying the hash map.</remarks>
    /// <param name="key">The key to add.</param>
    /// <param name="item">The value to add.</param>
    /// <exception cref="ArgumentException">Thrown if the key was already present.</exception>
    public void Add(TKey key, TValue item)
    {
        var result = TryAdd(key, item);
        if (!result)
        {
            throw new ArgumentException($"An item with the same key has already been added: {key}");
        }
    }

    /// <summary>
    /// Removes a particular key and its value.
    /// </summary>
    /// <param name="item">The value to remove.</param>
    /// <returns>True if the value was present.</returns>
    public bool Remove(TKey key)
    {
        return -1 != _hashMap.TryRemove(key);
    }

    /// <summary>
    /// Returns the value associated with a key.
    /// </summary>
    /// <param name="key">The key to look up.</param>
    /// <param name="item">Outputs the value associated with the key. Outputs default if the key was not present.</param>
    /// <returns>True if the key was present.</returns>
    public bool TryGetValue(TKey key, out TValue item)
    {
        return _hashMap.TryGetValue(key, out item);
    }

    /// <summary>
    /// Returns true if a given key is present in this hash map.
    /// </summary>
    /// <param name="key">The key to look up.</param>
    /// <returns>True if the key was present.</returns>
    public bool ContainsKey(TKey key)
    {
        return -1 != _hashMap.Find(key);
    }

    /// <summary>
    /// Sets the capacity to match what it would be if it had been originally initialized with all its entries.
    /// </summary>
    public void TrimExcess() => _hashMap.TrimExcess();

    public void Resize(int newSize)
    {
        _hashMap.Resize(newSize);
    }

    public void Clear()
    {
        _hashMap.Clear();
    }

    /// <summary>
    /// Retrieves an array of keys from the hash map.
    /// </summary>
    /// <returns>An array containing the keys stored in the hash map.</returns>
    public UnsafeArray<TKey> GetKeyArray(Allocator allocator) => _hashMap.GetKeyArray(allocator);

    /// <summary>
    /// Retrieves an array of values from the underlying hash map.
    /// </summary>
    /// <returns>An UnsafeArray containing the values stored in the hash map.</returns>
    public UnsafeArray<TValue> GetValueArray(Allocator allocator) => _hashMap.GetValueArray<TValue>(allocator);

    /// <summary>
    /// Retrieves an array of key-value pairs from the hash map. The keys are of type TKey and the values are of type
    /// TValue.
    /// </summary>
    /// <returns>Returns an UnsafeArray containing KeyValuePair objects.</returns>
    public UnsafeArray<KeyValuePair<TKey, TValue>> GetKeyValueArrays(Allocator allocator) => _hashMap.GetKeyValueArrays<TValue>(allocator);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public readonly void* GetUnsafePtr()
    {
        return _hashMap.Buffer;
    }

    public void Dispose()
    {
        _hashMap.Dispose();
    }

    public void Test(ref HashMapHelper<TKey> t)
    {
        Console.WriteLine(t.Equals(_hashMap));
    }
}