// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschränkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

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

namespace Squidex.Infrastructure
{
    public static class CollectionExtensions
    {
        public static bool SetEquals<T>(this IReadOnlyCollection<T> source, IReadOnlyCollection<T> other)
        {
            return source.Count == other.Count && source.Intersect(other).Count() == other.Count;
        }

        public static bool SetEquals<T>(this IReadOnlyCollection<T> source, IReadOnlyCollection<T> other, IEqualityComparer<T> comparer)
        {
            return source.Count == other.Count && source.Intersect(other, comparer).Count() == other.Count;
        }

        public static IResultList<T> SortSet<T, TKey>(this IResultList<T> input, Func<T, TKey> idProvider, IReadOnlyList<TKey> ids) where T : class
        {
            return ResultList.Create(input.Total, SortList(input, idProvider, ids));
        }

        public static IEnumerable<T> SortList<T, TKey>(this IEnumerable<T> input, Func<T, TKey> idProvider, IReadOnlyList<TKey> ids) where T : class
        {
            return ids.Select(id => input.FirstOrDefault(x => Equals(idProvider(x), id))).NotNull();
        }

        public static IEnumerable<T> Duplicates<T>(this IEnumerable<T> input)
        {
            return input.GroupBy(x => x).Where(x => x.Count() > 1).Select(x => x.Key);
        }

        public static int IndexOf<T>(this IEnumerable<T> input, Func<T, bool> predicate)
        {
            var i = 0;

            foreach (var item in input)
            {
                if (predicate(item))
                {
                    return i;
                }

                i++;
            }

            return -1;
        }

        public static IEnumerable<TResult> Duplicates<TResult, T>(this IEnumerable<T> input, Func<T, TResult> selector)
        {
            return input.GroupBy(selector).Where(x => x.Count() > 1).Select(x => x.Key);
        }

        public static void AddRange<T>(this ICollection<T> target, IEnumerable<T> source)
        {
            foreach (var value in source)
            {
                target.Add(value);
            }
        }

        public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> enumerable)
        {
            var random = new Random();

            return enumerable.OrderBy(x => random.Next()).ToList();
        }

        public static IEnumerable<T> OrEmpty<T>(this IEnumerable<T>? source)
        {
            return source ?? Enumerable.Empty<T>();
        }

        public static IEnumerable<T> NotNull<T>(this IEnumerable<T?> source) where T : class
        {
            return source.Where(x => x != null)!;
        }

        public static IEnumerable<T> Concat<T>(this IEnumerable<T> source, T value)
        {
            return source.Concat(Enumerable.Repeat(value, 1));
        }

        public static TResult[] Map<TResult, T>(this T[] value, Func<T, TResult> convert)
        {
            var result = new TResult[value.Length];

            for (var i = 0; i < value.Length; i++)
            {
                result[i] = convert(value[i]);
            }

            return result;
        }

        public static int SequentialHashCode<T>(this IEnumerable<T> collection)
        {
            return collection.SequentialHashCode(EqualityComparer<T>.Default);
        }

        public static int SequentialHashCode<T>(this IEnumerable<T> collection, IEqualityComparer<T> comparer)
        {
            var hashCode = 17;

            foreach (var item in collection)
            {
                if (!Equals(item, null))
                {
                    hashCode = (hashCode * 23) + comparer.GetHashCode(item);
                }
            }

            return hashCode;
        }

        public static int OrderedHashCode<T>(this IEnumerable<T> collection) where T : notnull
        {
            return collection.OrderedHashCode(EqualityComparer<T>.Default);
        }

        public static int OrderedHashCode<T>(this IEnumerable<T> collection, IEqualityComparer<T> comparer) where T : notnull
        {
            Guard.NotNull(comparer, nameof(comparer));

            var hashCodes = collection.Where(x => !Equals(x, null)).Select(x => x.GetHashCode()).OrderBy(x => x).ToArray();

            var hashCode = 17;

            foreach (var code in hashCodes)
            {
                hashCode = (hashCode * 23) + code;
            }

            return hashCode;
        }

        public static int DictionaryHashCode<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary) where TKey : notnull
        {
            return DictionaryHashCode(dictionary, EqualityComparer<TKey>.Default, EqualityComparer<TValue>.Default);
        }

        public static int DictionaryHashCode<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer) where TKey : notnull
        {
            var hashCode = 17;

            foreach (var (key, value) in dictionary.OrderBy(x => x.Key))
            {
                hashCode = (hashCode * 23) + keyComparer.GetHashCode(key);

                if (!Equals(value, null))
                {
                    hashCode = (hashCode * 23) + valueComparer.GetHashCode(value);
                }
            }

            return hashCode;
        }

        public static bool EqualsDictionary<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, IReadOnlyDictionary<TKey, TValue> other) where TKey : notnull
        {
            return EqualsDictionary(dictionary, other, EqualityComparer<TKey>.Default, EqualityComparer<TValue>.Default);
        }

        public static bool EqualsDictionary<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, IReadOnlyDictionary<TKey, TValue> other, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer) where TKey : notnull
        {
            if (other == null)
            {
                return false;
            }

            if (dictionary.Count != other.Count)
            {
                return false;
            }

            var comparer = new KeyValuePairComparer<TKey, TValue>(keyComparer, valueComparer);

            return !dictionary.Except(other, comparer).Any();
        }

        public static Dictionary<TKey, TValue> ToDictionary<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary) where TKey : notnull
        {
            return dictionary.ToDictionary(x => x.Key, x => x.Value);
        }

        public static TValue GetOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key) where TKey : notnull
        {
            return dictionary.GetOrCreate(key, _ => default!);
        }

        public static TValue GetOrAddDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key) where TKey : notnull
        {
            return dictionary.GetOrAdd(key, _ => default!);
        }

        public static TValue GetOrNew<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key) where TKey : notnull where TValue : class, new()
        {
            return dictionary.GetOrCreate(key, _ => new TValue());
        }

        public static TValue GetOrAddNew<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key) where TKey : notnull where TValue : class, new()
        {
            return dictionary.GetOrAdd(key, _ => new TValue());
        }

        public static TValue GetOrCreate<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key, Func<TKey, TValue> creator) where TKey : notnull
        {
            if (!dictionary.TryGetValue(key, out var result))
            {
                result = creator(key);
            }

            return result;
        }

        public static TValue GetOrAdd<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue fallback) where TKey : notnull
        {
            if (!dictionary.TryGetValue(key, out var result))
            {
                result = fallback;

                dictionary.Add(key, result);
            }

            return result;
        }

        public static TValue GetOrAdd<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, Func<TKey, TValue> creator) where TKey : notnull
        {
            if (!dictionary.TryGetValue(key, out var result))
            {
                result = creator(key);

                dictionary.Add(key, result);
            }

            return result;
        }

        public static TValue GetOrAdd<TKey, TContext, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TContext context, Func<TKey, TContext, TValue> creator) where TKey : notnull
        {
            if (!dictionary.TryGetValue(key, out var result))
            {
                result = creator(key, context);

                dictionary.Add(key, result);
            }

            return result;
        }

        public static void Foreach<T>(this IEnumerable<T> collection, Action<T, int> action)
        {
            var index = 0;

            foreach (var item in collection)
            {
                action(item, index);

                index++;
            }
        }

        public sealed class KeyValuePairComparer<TKey, TValue> : IEqualityComparer<KeyValuePair<TKey, TValue>> where TKey : notnull
        {
            private readonly IEqualityComparer<TKey> keyComparer;
            private readonly IEqualityComparer<TValue> valueComparer;

            public KeyValuePairComparer(IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
            {
                this.keyComparer = keyComparer;
                this.valueComparer = valueComparer;
            }

            public bool Equals(KeyValuePair<TKey, TValue> x, KeyValuePair<TKey, TValue> y)
            {
                return keyComparer.Equals(x.Key, y.Key) && valueComparer.Equals(x.Value, y.Value);
            }

            public int GetHashCode(KeyValuePair<TKey, TValue> obj)
            {
                return keyComparer.GetHashCode(obj.Key) ^ ValueHashCode(obj);
            }

            private int ValueHashCode(KeyValuePair<TKey, TValue> obj)
            {
                if (Equals(obj.Value, null))
                {
                    return 0;
                }

                return valueComparer.GetHashCode(obj.Value);
            }
        }
    }
}