//
// ImmutableDictionary.cs
//
// Contains code from ACIS P2P Library (https://github.com/ptony82/brunet)
//
// Author:
//       Mike Krüger <mkrueger@xamarin.com>
//
// Copyright (c) 2013 Xamarin Inc. (http://xamarin.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

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

namespace Quobject.Collections.Immutable
{
    /** Read-only immutable data structure for IComparable Keys
	 * Implemented as a readonly binary AVL tree, so most operations
	 * have 1.44 Log C complexity where C is the count.
	 *
	 * http://en.wikipedia.org/wiki/AVL_tree
	  
	 * To modify, use the InsertIntoNew and RemoveFromNew methods
	 * which return a new instance with minimal changes (about Log C),
	 * so this is an efficient way to make changes without having
	 * to copy the entire data structure.
	 * 
	 * Clearly this is a thread-safe class (because it is read-only),
	 * but note: if the K or V types are not immutable, you could have
	 * a problem: someone could modify the object without changing the 
	 * dictionary and not only would the Dictionary be incorrectly ordered
	 * you could have race conditions.  It is required that you only use
	 * immutable key types in the dictionary, and only thread-safe if
	 * both the keys and values are immutable.
	 */
	public class ImmutableDictionary<TKey, TValue> : IImmutableDictionary<TKey, TValue> where TKey : System.IComparable<TKey>
    {
        internal static readonly ImmutableDictionary<TKey, TValue> Empty = new ImmutableDictionary<TKey, TValue>();
        AvlNode<KeyValuePair<TKey, TValue>> root = AvlNode<KeyValuePair<TKey, TValue>>.Empty;
        readonly IEqualityComparer<TKey> keyComparer;
        readonly IEqualityComparer<TValue> valueComparer;

        internal ImmutableDictionary()
        {
        }

        internal ImmutableDictionary(AvlNode<KeyValuePair<TKey, TValue>> root, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
        {
            this.root = root;
            this.keyComparer = keyComparer;
            this.valueComparer = valueComparer;
        }

        public ImmutableDictionary<TKey, TValue> WithComparers(IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
        {
            return new ImmutableDictionary<TKey, TValue>(root, keyComparer, valueComparer);
        }

        public ImmutableDictionary<TKey, TValue> WithComparers(IEqualityComparer<TKey> keyComparer)
        {
            return WithComparers(keyComparer, valueComparer);
        }
        #region IImmutableDictionary implementation
        public ImmutableDictionary<TKey, TValue> Add(TKey key, TValue value)
        {
            var pair = new KeyValuePair<TKey, TValue>(key, value);
            return new ImmutableDictionary<TKey, TValue>(root.InsertIntoNew(pair, CompareKV), keyComparer, valueComparer);
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.Add(TKey key, TValue value)
        {
            return Add(key, value);
        }

        public ImmutableDictionary<TKey, TValue> AddRange(IEnumerable<KeyValuePair<TKey, TValue>> pairs)
        {
            var result = this;
            foreach (var kv in pairs)
                result = result.Add(kv.Key, kv.Value);
            return result;
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.AddRange(IEnumerable<KeyValuePair<TKey, TValue>> pairs)
        {
            return AddRange(pairs);
        }

        public ImmutableDictionary<TKey, TValue> Clear()
        {
            return Empty;
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.Clear()
        {
            return Clear();
        }

        static int CompareKV(KeyValuePair<TKey, TValue> left, KeyValuePair<TKey, TValue> right)
        {
            return left.Key.CompareTo(right.Key);
        }

        public bool Contains(KeyValuePair<TKey, TValue> kv)
        {
            var node = root.SearchNode(kv, CompareKV);
            return !node.IsEmpty && valueComparer.Equals(node.Value.Value, kv.Value);
        }

        public ImmutableDictionary<TKey, TValue> Remove(TKey key)
        {
            bool found;
            var pair = new KeyValuePair<TKey,TValue>(key, default (TValue));
            return new ImmutableDictionary<TKey, TValue>(root.RemoveFromNew(pair, CompareKV, out found), keyComparer, valueComparer);
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.Remove(TKey key)
        {
            return Remove(key);
        }

        public IImmutableDictionary<TKey, TValue> RemoveRange(IEnumerable<TKey> keys)
        {
            IImmutableDictionary<TKey, TValue> result = this;
            foreach (var key in keys)
            {
                result = result.Remove(key);
            }
            return result;
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.RemoveRange(IEnumerable<TKey> keys)
        {
            return RemoveRange(keys);
        }

        public ImmutableDictionary<TKey, TValue> SetItem(TKey key, TValue value)
        {
            var result = this;
            if (result.ContainsKey(key))
                result = result.Remove(key);
            return result.Add(key, value);
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.SetItem(TKey key, TValue value)
        {
            return SetItem(key, value);
        }

        public IImmutableDictionary<TKey, TValue> SetItems(IEnumerable<KeyValuePair<TKey, TValue>> items)
        {
            var result = this;
            foreach (var kv in items)
            {
                result = result.SetItem(kv.Key, kv.Value);
            }
            return result;
        }

        IImmutableDictionary<TKey, TValue> IImmutableDictionary<TKey, TValue>.SetItems(IEnumerable<KeyValuePair<TKey, TValue>> items)
        {
            return SetItems(items);
        }

        public IEqualityComparer<TKey> KeyComparer
        {
            get
            {
                return keyComparer;
            }
        }

        public IEqualityComparer<TValue> ValueComparer
        {
            get
            {
                return valueComparer;
            }
        }
        #endregion
        #region IReadOnlyDictionary implementation
        public bool ContainsKey(TKey key)
        {
            return !root.SearchNode(new KeyValuePair<TKey, TValue>(key, default(TValue)), CompareKV).IsEmpty;
        }

        public bool TryGetValue(TKey key, out TValue value)
        {
            var node = root.SearchNode(new KeyValuePair<TKey, TValue>(key, default(TValue)), CompareKV);
            if (node.IsEmpty)
            {
                value = default (TValue);
                return false;
            }
            value = node.Value.Value;
            return true;
        }

        public TValue this [TKey key]
        {
            get
            {
                TValue value;
                if (TryGetValue(key, out value))
                    return value;
                throw new KeyNotFoundException(String.Format("Key: {0}", key));
            }
        }

        public IEnumerable<TKey> Keys
        {
            get
            {
                foreach (var kv in this)
                {
                    yield return kv.Key;
                }
            }
        }

        public IEnumerable<TValue> Values
        {
            get
            {
                foreach (var kv in this)
                {
                    yield return kv.Value;
                }
            }
        }
        #endregion
        #region IEnumerable implementation
        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
        {
            var to_visit = new Stack<AvlNode<KeyValuePair<TKey,TValue>>>();
            to_visit.Push(root);
            while (to_visit.Count > 0)
            {
                var this_d = to_visit.Pop();
                if (this_d.IsEmpty)
                {
                    continue;
                }
                if (this_d.Left.IsEmpty)
                {
                    //This is the next smallest value in the Dict:
                    yield return this_d.Value;
                    to_visit.Push(this_d.Right);
                }
                else
                {
                    //Break it up
                    to_visit.Push(this_d.Right);
                    to_visit.Push(new AvlNode<KeyValuePair<TKey, TValue>>(this_d.Value));
                    to_visit.Push(this_d.Left);
                }
            }
        }
        #endregion
        #region IEnumerable implementation
        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
        #endregion
        #region IReadOnlyCollection implementation
        public int Count
        {
            get
            {
                return root.Count;
            }
        }
        #endregion
        public Builder ToBuilder()
        {
            return new Builder(root, keyComparer, valueComparer);
        }

        public sealed class Builder : IDictionary<TKey, TValue>
        {
            AvlNode<KeyValuePair<TKey, TValue>> root;
            IEqualityComparer<TKey> keyComparer;

            public IEqualityComparer<TKey> KeyComparer
            {
                get
                {
                    return keyComparer;
                }
                set
                {
                    keyComparer = value;
                }
            }

            IEqualityComparer<TValue> valueComparer;

            public IEqualityComparer<TValue> ValueComparer
            {
                get
                {
                    return valueComparer;
                }
                set
                {
                    valueComparer = value;
                }
            }

            internal Builder(AvlNode<KeyValuePair<TKey, TValue>> root, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
            {
                this.root = root.ToMutable();
                this.keyComparer = keyComparer;
                this.valueComparer = valueComparer;
            }

            public ImmutableDictionary<TKey, TValue> ToImmutable()
            {
                return new ImmutableDictionary<TKey, TValue>(root, keyComparer, valueComparer);
            }
            #region IDictionary implementation
            public void Add(TKey key, TValue value)
            {
                Add(new KeyValuePair<TKey, TValue>(key, value));
            }

            public bool ContainsKey(TKey key)
            {
                return !root.SearchNode(new KeyValuePair<TKey, TValue>(key, default (TValue)), CompareKV).IsEmpty;
            }

            public bool Remove(TKey key)
            {
                bool found;
                root = root.RemoveFromNew(new KeyValuePair<TKey, TValue>(key, default (TValue)), CompareKV, out found);
                return found;
            }

            public void SetItem(TKey key, TValue value)
            {
                if (ContainsKey(key))
                    Remove(key);
                Add(key, value);
            }

            public bool TryGetValue(TKey key, out TValue value)
            {
                var node = root.SearchNode(new KeyValuePair<TKey, TValue>(key, default(TValue)), CompareKV);
                if (node.IsEmpty)
                {
                    value = default (TValue);
                    return false;
                }
                value = node.Value.Value;
                return true;
            }

            public TValue this [TKey key]
            {
                get
                {
                    TValue value;
                    if (TryGetValue(key, out value))
                        return value;
                    throw new KeyNotFoundException(String.Format("Key: {0}", key));
                }
                set
                {
                    if (ContainsKey(key))
                        Remove(key);
                    Add(key, value);
                }
            }

            ICollection<TKey> IDictionary<TKey, TValue>.Keys
            {
                get
                {
                    return Keys.ToList();
                }
            }

            public IEnumerable<TKey> Keys
            {
                get
                {
                    foreach (var kv in this)
                    {
                        yield return kv.Key;
                    }
                }
            }

            ICollection<TValue> IDictionary<TKey, TValue>.Values
            {
                get
                {
                    return Values.ToList();
                }
            }

            public IEnumerable<TValue> Values
            {
                get
                {
                    foreach (var kv in this)
                    {
                        yield return kv.Value;
                    }
                }
            }
            #endregion
            #region ICollection implementation
            public void Add(KeyValuePair<TKey, TValue> item)
            {
                root = root.InsertIntoNew(item, CompareKV);
            }

            public void Clear()
            {
                root = new AvlNode<KeyValuePair<TKey, TValue>>().ToMutable();
            }

            public bool Contains(KeyValuePair<TKey, TValue> item)
            {
                TValue value;
                if (!TryGetValue(item.Key, out value))
                    return false;
                return valueComparer.Equals(value, item.Value);
            }

            public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
            {
                if (arrayIndex < 0 || arrayIndex + Count > array.Length)
                    throw new ArgumentOutOfRangeException("arrayIndex");
                foreach (var pair in this)
                {
                    array[arrayIndex++] = pair;
                }
            }

            public bool Remove(KeyValuePair<TKey, TValue> item)
            {
                if (!Contains(item))
                    return false;
                Remove(item.Key);
                return true;
            }

            public int Count
            {
                get
                {
                    return root.Count;
                }
            }

            public bool IsReadOnly
            {
                get
                {
                    return false;
                }
            }
            #endregion
            #region IEnumerable implementation
            public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
            {
                return root.GetEnumerator(false);
            }
            #endregion
            #region IEnumerable implementation
            IEnumerator IEnumerable.GetEnumerator()
            {
                return this.GetEnumerator();
            }
            #endregion
        }
    }

    public static class ImmutableDictionary
    {
        public static bool Contains<TKey, TValue>(this IImmutableDictionary<TKey, TValue> dictionary, TKey key, TValue value)
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");
            return dictionary.Contains(new KeyValuePair<TKey, TValue>(key, value));
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>() where TKey : System.IComparable<TKey>
        {
            return ImmutableDictionary<TKey, TValue>.Empty;
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>(IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer, IEnumerable<KeyValuePair<TKey, TValue>> items) where TKey : System.IComparable<TKey>
        {
            return Create<TKey, TValue>(keyComparer, valueComparer).AddRange(items);
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>(IEqualityComparer<TKey> keyComparer, IEnumerable<KeyValuePair<TKey, TValue>> items) where TKey : System.IComparable<TKey>
        {
            return Create<TKey, TValue>(keyComparer).AddRange(items);
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>(IEnumerable<KeyValuePair<TKey, TValue>> items) where TKey : System.IComparable<TKey>
        {
            return Create<TKey, TValue>().AddRange(items);
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>(IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer) where TKey : System.IComparable<TKey>
        {
            return Create<TKey, TValue>().WithComparers(keyComparer, valueComparer);
        }

        public static ImmutableDictionary<TKey, TValue> Create<TKey, TValue>(IEqualityComparer<TKey> keyComparer) where TKey : System.IComparable<TKey>
        {
            return Create<TKey, TValue>().WithComparers(keyComparer);
        }

        public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key) where TKey : System.IComparable<TKey>
        {
            return dictionary.GetValueOrDefault<TKey, TValue>(key, default (TValue));
        }

        public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue) where TKey : System.IComparable<TKey>
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");
            TValue result;
            if (dictionary.TryGetValue(key, out result))
                return result;
            return defaultValue;
        }

        public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key) where TKey : System.IComparable<TKey>
        {
            return dictionary.GetValueOrDefault<TKey, TValue>(key, default (TValue));
        }

        public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue) where TKey : System.IComparable<TKey>
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");
            TValue result;
            if (dictionary.TryGetValue(key, out result))
                return result;
            return defaultValue;
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> source, IEqualityComparer<TKey> keyComparer) where TKey : System.IComparable<TKey>
        {
            return source.ToImmutableDictionary(keyComparer, null);
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> source) where TKey : System.IComparable<TKey>
        {
            return source.ToImmutableDictionary(null, null);
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TKey, TValue>(this IEnumerable<KeyValuePair<TKey, TValue>> source, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer) where TKey : System.IComparable<TKey>
        {
            if (source == null)
                throw new ArgumentNullException("dictionary");
            return Create<TKey, TValue>(keyComparer, valueComparer).AddRange(source);
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TSource, TKey, TValue>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TValue> elementSelector, IEqualityComparer<TKey> keyComparer) where TKey : System.IComparable<TKey>
        {
            return source.ToImmutableDictionary(keySelector, elementSelector, keyComparer, null);
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TSource, TKey, TValue>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TValue> elementSelector, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer) where TKey : System.IComparable<TKey>
        {
            if (source == null)
                throw new ArgumentNullException("dictionary");
            return Create<TKey, TValue>(keyComparer, valueComparer).AddRange(source.Select(x => new KeyValuePair<TKey, TValue>(keySelector(x), elementSelector(x))));
        }

        public static ImmutableDictionary<TKey, TValue> ToImmutableDictionary<TSource, TKey, TValue>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TValue> elementSelector) where TKey : System.IComparable<TKey>
        {
            return source.ToImmutableDictionary(keySelector, elementSelector, null, null);
        }
    }
}