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

using static PKHeX.Core.EncountersWC3;

namespace PKHeX.Core
{
    public static class EncounterEvent
    {
        /// <summary>Event Database for Generation 3</summary>
        public static IReadOnlyList<WC3> MGDB_G3 { get; private set; } = Array.Empty<WC3>();

        /// <summary>Event Database for Generation 4</summary>
        public static IReadOnlyList<PCD> MGDB_G4 { get; private set; } = Array.Empty<PCD>();

        /// <summary>Event Database for Generation 5</summary>
        public static IReadOnlyList<PGF> MGDB_G5 { get; private set; } = Array.Empty<PGF>();

        /// <summary>Event Database for Generation 6</summary>
        public static IReadOnlyList<WC6> MGDB_G6 { get; private set; } = Array.Empty<WC6>();

        /// <summary>Event Database for Generation 7</summary>
        public static IReadOnlyList<WC7> MGDB_G7 { get; private set; } = Array.Empty<WC7>();

        /// <summary>Event Database for Generation 7 <see cref="GameVersion.GG"/></summary>
        public static IReadOnlyList<WB7> MGDB_G7GG { get; private set; } = Array.Empty<WB7>();

        /// <summary>Event Database for Generation 8</summary>
        public static IReadOnlyList<WC8> MGDB_G8 { get; private set; } = Array.Empty<WC8>();

        /// <summary>Indicates if the databases are initialized.</summary>
        public static bool Initialized => MGDB_G3.Count != 0;

        private static HashSet<PCD> GetPCDDB(byte[] bin) => new(ArrayUtil.EnumerateSplit(bin, PCD.Size).Select(d => new PCD(d)));

        private static HashSet<PGF> GetPGFDB(byte[] bin) => new(ArrayUtil.EnumerateSplit(bin, PGF.Size).Select(d => new PGF(d)));

        private static HashSet<WC6> GetWC6DB(byte[] wc6bin, byte[] wc6full) => new(
            ArrayUtil.EnumerateSplit(wc6full, WC6Full.Size).Select(d => new WC6Full(d).Gift)
            .Concat(ArrayUtil.EnumerateSplit(wc6bin, WC6.Size).Select(d => new WC6(d))));

        private static HashSet<WC7> GetWC7DB(byte[] wc7bin, byte[] wc7full) => new(
            ArrayUtil.EnumerateSplit(wc7full, WC7Full.Size).Select(d => new WC7Full(d).Gift)
            .Concat(ArrayUtil.EnumerateSplit(wc7bin, WC7.Size).Select(d => new WC7(d))));

        private static HashSet<WB7> GetWB7DB(byte[] wc7full) => new(ArrayUtil.EnumerateSplit(wc7full, WB7.SizeFull).Select(d => new WB7(d)));

        private static HashSet<WC8> GetWC8DB(byte[] wc8bin) =>
            new(ArrayUtil.EnumerateSplit(wc8bin, WC8.Size).Select(d => new WC8(d)));

        public static void RefreshMGDB(params string[] paths)
        {
            var g4 = GetPCDDB(Util.GetBinaryResource("wc4.pkl"));
            var g5 = GetPGFDB(Util.GetBinaryResource("pgf.pkl"));
            var g6 = GetWC6DB(Util.GetBinaryResource("wc6.pkl"), Util.GetBinaryResource("wc6full.pkl"));
            var g7 = GetWC7DB(Util.GetBinaryResource("wc7.pkl"), Util.GetBinaryResource("wc7full.pkl"));
            var b7 = GetWB7DB(Util.GetBinaryResource("wb7full.pkl"));
            var g8 = GetWC8DB(Util.GetBinaryResource("wc8.pkl"));

            foreach (var gift in paths.Where(Directory.Exists).SelectMany(MysteryUtil.GetGiftsFromFolder))
            {
                switch (gift)
                {
                    case PCD pcd: g4.Add(pcd); continue;
                    case PGF pgf: g5.Add(pgf); continue;
                    case WC6 wc6: g6.Add(wc6); continue;
                    case WC7 wc7: g7.Add(wc7); continue;
                    case WB7 wb7: b7.Add(wb7); continue;
                    case WC8 wc8: g8.Add(wc8); continue;
                }
            }

            MGDB_G3 = Encounter_WC3; // hardcoded
            MGDB_G4 = g4.ToArray();
            MGDB_G5 = g5.ToArray();
            MGDB_G6 = g6.ToArray();
            MGDB_G7 = g7.ToArray();
            MGDB_G7GG = b7.ToArray();
            MGDB_G8 = g8.ToArray();
        }

        public static IEnumerable<MysteryGift> GetAllEvents(bool sorted = true)
        {
            var regular = new IReadOnlyList<MysteryGift>[]
            {
                MGDB_G4,
                MGDB_G5,
                MGDB_G6,
                MGDB_G7,
                MGDB_G7GG,
                MGDB_G8,
            }.SelectMany(z => z);
            regular = regular.Where(mg => !mg.IsItem && mg.IsPokémon && mg.Species > 0);
            var result = MGDB_G3.Concat(regular);
            if (sorted)
                result = result.OrderBy(mg => mg.Species);
            return result;
        }
    }
}