using System;
using System.Collections.Generic;

namespace PKHeX.Core.Searching
{
    /// <summary>
    /// <see cref="PKM"/> searching utility
    /// </summary>
    public static class SearchUtil
    {
        // Future: Might need to clamp down further for generations that cannot exist in the current format.
        public static bool SatisfiesFilterFormat(PKM pk, int format, SearchComparison formatOperand) => formatOperand switch
        {
            SearchComparison.GreaterThanEquals when pk.Format <  format => false,
            SearchComparison.Equals            when pk.Format != format => false,
            SearchComparison.LessThanEquals    when pk.Format >  format => false,

            _ when format <= 2 => pk.Format <= 2, // 1-2
            _ when format <= 6 => pk.Format >= 3, // 3-6
            _ => true,
        };

        public static bool SatisfiesFilterGeneration(PKM pk, int generation) => generation switch
        {
            1 => pk.VC || pk.Format < 3,
            2 => pk.VC || pk.Format < 3,
            _ => pk.Generation == generation,
        };

        public static bool SatisfiesFilterLevel(PKM pk, SearchComparison option, int level)
        {
            if (level > 100)
                return true; // why???

            return option switch
            {
                SearchComparison.LessThanEquals =>    pk.Stat_Level <= level,
                SearchComparison.Equals =>            pk.Stat_Level == level,
                SearchComparison.GreaterThanEquals => pk.Stat_Level >= level,
                _ => true,
            };
        }

        public static bool SatisfiesFilterEVs(PKM pk, int option) => option switch
        {
            1 => pk.EVTotal == 0, // None (0)
            2 => pk.EVTotal is (not 0) and < 128, // Some (127-1)
            3 => pk.EVTotal is >= 128 and < 508, // Half (128-507)
            4 => pk.EVTotal >= 508, // Full (508+)
            _ => true,
        };

        public static bool SatisfiesFilterIVs(PKM pk, int option) => option switch
        {
            1 => pk.IVTotal <= 90, // <= 90
            2 => pk.IVTotal is >  90 and <= 120, // 91-120
            3 => pk.IVTotal is > 120 and <= 150, // 121-150
            4 => pk.IVTotal is > 150 and <  180, // 151-179
            5 => pk.IVTotal >= 180, // 180+
            6 => pk.IVTotal == 186, // == 186
            _ => true,
        };

        public static bool SatisfiesFilterMoves(PKM pk, IEnumerable<int> requiredMoves)
        {
            foreach (var m in requiredMoves)
            {
                if (!pk.HasMove(m))
                    return false;
            }
            return true;
        }

        public static bool SatisfiesFilterBatchInstruction(PKM pk, IReadOnlyList<StringInstruction> filters)
        {
            return BatchEditing.IsFilterMatch(filters, pk); // Compare across all filters
        }

        public static Func<PKM, string> GetCloneDetectMethod(CloneDetectionMethod method) => method switch
        {
            CloneDetectionMethod.HashPID => HashByPID,
            _ => HashByDetails,
        };

        public static string HashByDetails(PKM pk) => pk.Format switch
        {
            1 => $"{pk.Species:000}{((PK1) pk).DV16:X4}",
            2 => $"{pk.Species:000}{((PK2) pk).DV16:X4}",
            _ => $"{pk.Species:000}{pk.PID:X8}{string.Join(" ", pk.IVs)}{pk.Form:00}",
        };

        public static string HashByPID(PKM pk) => pk.Format switch
        {
            1 => $"{((PK1) pk).DV16:X4}",
            2 => $"{((PK2) pk).DV16:X4}",
            _ => $"{pk.PID:X8}",
        };

        public static IEnumerable<PKM> GetClones(IEnumerable<PKM> res, CloneDetectionMethod type = CloneDetectionMethod.HashDetails)
        {
            var method = GetCloneDetectMethod(type);
            return GetExtraClones(res, method);
        }

        public static IEnumerable<T> GetUniques<T>(IEnumerable<T> db, Func<T, string> method)
        {
            var hs = new HashSet<string>();
            foreach (var t in db)
            {
                var hash = method(t);
                if (hs.Contains(hash))
                    continue;
                yield return t;
                hs.Add(hash);
            }
        }

        public static IEnumerable<T> GetExtraClones<T>(IEnumerable<T> db, Func<T, string> method)
        {
            var hs = new HashSet<string>();
            foreach (var t in db)
            {
                var hash = method(t);
                if (hs.Contains(hash))
                    yield return t;
                else
                    hs.Add(hash);
            }
        }
    }
}