stgsharp/StgSharp.Common/Collections/BidirectionalDictionary.cs

// -----------------------------------------------------------------------------
// file="BidirectionalDictionary"
// Project: StgSharp
// Copyright (c) Nitload.
// SPDX-License-Identifier: MIT
// -----------------------------------------------------------------------------

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;

namespace StgSharp.Collections
{
    public sealed class BidirectionalDictionary<TFirst, TSecond> : IBidirectionalDictionary<TFirst, TSecond>
        where TFirst : notnull
        where TSecond : notnull
    {

        private readonly Dictionary<TFirst, TSecond> _forward;
        private readonly Dictionary<TSecond, TFirst> _reverse;

        public BidirectionalDictionary()
        {
            _forward = [];
            _reverse = [];
        }

        public TFirst this[
                      TSecond key
        ]
        {
            get => _reverse.TryGetValue(key, out TFirst value) ?
                   value :
                   throw new ArgumentException($"Cannot find key {key} in dictionary.");
            set
            {
                if (_reverse.TryGetValue(key, out TFirst origin))
                {
                    _reverse[key] = value;
                    _ = _forward.Remove(origin);
                } else
                {
                    _reverse.Add(key, value);
                }
                _forward.Add(value, key);
            }
        }

        public TSecond this[
                       TFirst key
        ]
        {
            get => _forward.TryGetValue(key, out TSecond value) ?
                   value :
                   throw new ArgumentException($"Cannot find key {key} in dictionary.");
            set
            {
                if (_forward.TryGetValue(key, out TSecond origin))
                {
                    _forward[key] = value;
                    _ = _reverse.Remove(origin);
                } else
                {
                    _forward.Add(key, value);
                }
                _reverse.Add(value, key);
            }
        }

        public bool IsReadOnly => false;

        public ICollection<TFirst> FirstIndex => _forward.Keys;

        public ICollection<TSecond> SecondIndex => _reverse.Keys;

        public int Count => _forward.Count;

        public IReadOnlyDictionary<TFirst, TSecond> Forward => new ReadOnlyDictionary<TFirst, TSecond>(
            _forward);

        public IReadOnlyDictionary<TSecond, TFirst> Reverse => new ReadOnlyDictionary<TSecond, TFirst>(
            _reverse);

        public void Add(
                    KeyValuePair<TFirst, TSecond> item
        )
        {
            if (_forward.ContainsKey(item.Key) || _reverse.ContainsKey(item.Value)) {
                throw new ArgumentException("Duplicate key or value.");
            }
            _forward.Add(item.Key, item.Value);
            _reverse.Add(item.Value, item.Key);
        }

        public void Add(
                    TFirst key,
                    TSecond value
        )
        {
            if (_forward.ContainsKey(key) || _reverse.ContainsKey(value)) {
                throw new ArgumentException("Duplicate key or value.");
            }
            _forward.Add(key, value);
            _reverse.Add(value, key);
        }

        public void Clear()
        {
            _forward.Clear();
            _reverse.Clear();
        }

        public bool Contains(
                    KeyValuePair<TFirst, TSecond> item
        )
        {
            return _forward.Contains(item) &&
                   _reverse.TryGetValue(item.Value, out TFirst var) &&
                   var!.Equals(item.Key);
        }

        public bool Contains(
                    TSecond key
        )
        {
            return _reverse.ContainsKey(key);
        }

        public bool Contains(
                    TFirst key
        )
        {
            return _forward.ContainsKey(key);
        }

        public void CopyTo(
                    KeyValuePair<TFirst, TSecond>[] array,
                    int arrayIndex
        )
        {
            if (array == null) {
                throw new ArgumentNullException(nameof(array));
            }
            if (arrayIndex < 0 || arrayIndex > array.Length) {
                throw new ArgumentOutOfRangeException(nameof(arrayIndex));
            }
            if (array.Length - arrayIndex < _forward.Count) {
                throw new ArgumentException("The array is too small to copy the elements.");
            }

            foreach (KeyValuePair<TFirst, TSecond> pair in _forward) {
                array[arrayIndex++] = pair;
            }
        }

        public IEnumerator<KeyValuePair<TFirst, TSecond>> GetEnumerator()
        {
            foreach (KeyValuePair<TFirst, TSecond> pair in _forward) {
                yield return pair;
            }
        }

        public bool Remove(
                    TFirst key
        )
        {
            throw new NotImplementedException();
        }

        public bool Remove(
                    KeyValuePair<TFirst, TSecond> item
        )
        {
            if (_forward.Remove(item.Key)) {
                return _reverse.Remove(item.Value);
            }
            return false;
        }

        public bool TryGetValue(
                    TFirst key,
                    out TSecond value
        )
        {
            return _forward.TryGetValue(key, out value);
        }

        public bool TryGetValue(
                    TSecond key,
                    out TFirst value
        )
        {
            return _reverse.TryGetValue(key, out value);
        }

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

    }
}