using System;
using System.Collections.Generic;

namespace PKHeX.Core;

public static partial class Util
{
    public static List<ComboItem> GetCountryRegionList(string textFile, string lang)
    {
        string[] inputCSV = GetStringList(textFile);
        int index = GeoLocation.GetLanguageIndex(lang);
        var list = GetCBListFromCSV(inputCSV, index + 1);
        list.Sort(Comparer);
        return list;
    }

    private static List<ComboItem> GetCBListFromCSV(IReadOnlyList<string> inputCSV, int index)
    {
        var arr = new List<ComboItem>(inputCSV.Count);
        foreach (var line in inputCSV)
        {
            var text = StringUtil.GetNthEntry(line.AsSpan(), index, 4);
            var value = line.AsSpan(0, 3);
            var item = new ComboItem(text, ToInt32(value));
            arr.Add(item);
        }
        return arr;
    }

    public static List<ComboItem> GetCBList(ReadOnlySpan<string> inStrings)
    {
        var list = new List<ComboItem>(inStrings.Length);
        for (int i = 0; i < inStrings.Length; i++)
            list.Add(new ComboItem(inStrings[i], i));
        list.Sort(Comparer);
        return list;
    }

    public static List<ComboItem> GetCBList(IReadOnlyList<string> inStrings, IReadOnlyList<ushort> allowed)
    {
        var list = new List<ComboItem>(allowed.Count + 1) { new(inStrings[0], 0) };
        foreach (var index in allowed)
            list.Add(new ComboItem(inStrings[index], index));
        list.Sort(Comparer);
        return list;
    }

    public static List<ComboItem> GetCBList(IReadOnlyList<string> inStrings, int index, int offset = 0)
    {
        var list = new List<ComboItem>();
        AddCBWithOffset(list, inStrings, offset, index);
        return list;
    }

    public static IReadOnlyList<ComboItem> GetUnsortedCBList(IReadOnlyList<string> inStrings, ReadOnlySpan<byte> allowed)
    {
        var count = allowed.Length;
        var list = new ComboItem[count];
        for (var i = 0; i < allowed.Length; i++)
        {
            var index = allowed[i];
            var item = new ComboItem(inStrings[index], index);
            list[i] = item;
        }

        return list;
    }

    public static void AddCBWithOffset(List<ComboItem> list, IReadOnlyList<string> inStrings, int offset, int index)
    {
        var item = new ComboItem(inStrings[index - offset], index);
        list.Add(item);
    }

    public static void AddCBWithOffset(List<ComboItem> cbList, IReadOnlyList<string> inStrings, int offset, ushort[] allowed)
    {
        int beginCount = cbList.Count;
        cbList.Capacity += allowed.Length;
        foreach (var index in allowed)
        {
            var item = new ComboItem(inStrings[index - offset], index);
            cbList.Add(item);
        }
        cbList.Sort(beginCount, allowed.Length, Comparer);
    }

    public static void AddCBWithOffset(List<ComboItem> cbList, ReadOnlySpan<string> inStrings, int offset)
    {
        int beginCount = cbList.Count;
        cbList.Capacity += inStrings.Length;
        for (int i = 0; i < inStrings.Length; i++)
        {
            var x = inStrings[i];
            var item = new ComboItem(x, i + offset);
            cbList.Add(item);
        }
        cbList.Sort(beginCount, inStrings.Length, Comparer);
    }

    public static ComboItem[] GetVariedCBListBall(string[] inStrings, ReadOnlySpan<ushort> stringNum, ReadOnlySpan<byte> stringVal)
    {
        const int forcedTop = 3; // 3 Balls are preferentially first
        var list = new ComboItem[forcedTop + stringNum.Length];
        list[0] = new ComboItem(inStrings[4], (int)Ball.Poke);
        list[1] = new ComboItem(inStrings[3], (int)Ball.Great);
        list[2] = new ComboItem(inStrings[2], (int)Ball.Ultra);

        for (int i = 0; i < stringNum.Length; i++)
        {
            int index = stringNum[i];
            var value = stringVal[i];
            var text = inStrings[index];
            list[i + 3] = new ComboItem(text, value);
        }

        Array.Sort(list, 3, list.Length - 3, Comparer);
        return list;
    }

    private static readonly FunctorComparer<ComboItem> Comparer =
        new((a, b) => string.CompareOrdinal(a.Text, b.Text));

    private sealed class FunctorComparer<T> : IComparer<T>
    {
        private readonly Comparison<T> Comparison;
        public FunctorComparer(Comparison<T> comparison) => Comparison = comparison;
        public int Compare(T x, T y) => Comparison(x, y);
    }
}