PKHeX/PKHeX.Core/Game/GameStrings/MetDataSource.cs

using System;
using System.Collections.Generic;
using static PKHeX.Core.GameVersion;

namespace PKHeX.Core;

/// <summary>
/// Cached copies of Met Location lists
/// </summary>
public sealed class MetDataSource
{
    private readonly List<ComboItem> MetGen2;
    private readonly List<ComboItem> MetGen3;
    private readonly List<ComboItem> MetGen3CXD;
    private readonly List<ComboItem> MetGen4;
    private readonly List<ComboItem> MetGen5;
    private readonly List<ComboItem> MetGen6;
    private readonly List<ComboItem> MetGen7;
    private readonly List<ComboItem> MetGen7GG;
    private readonly List<ComboItem> MetGen8;
    private readonly List<ComboItem> MetGen8a;
    private readonly List<ComboItem> MetGen8b;

    private IReadOnlyList<ComboItem>? MetGen4Transfer;
    private IReadOnlyList<ComboItem>? MetGen5Transfer;

    public MetDataSource(GameStrings s)
    {
        MetGen2 = CreateGen2(s);
        MetGen3 = CreateGen3(s);
        MetGen3CXD = CreateGen3CXD(s);
        MetGen4 = CreateGen4(s);
        MetGen5 = CreateGen5(s);
        MetGen6 = CreateGen6(s);
        MetGen7 = CreateGen7(s);
        MetGen7GG = CreateGen7GG(s);
        MetGen8 = CreateGen8(s);
        MetGen8a = CreateGen8a(s);
        MetGen8b = CreateGen8b(s);
    }

    private static List<ComboItem> CreateGen2(GameStrings s)
    {
        var locations = Util.GetCBList(s.metGSC_00000.AsSpan(0, 0x5F));
        Util.AddCBWithOffset(locations, s.metGSC_00000.AsSpan(0x7E, 2), 0x7E);
        return locations;
    }

    private static List<ComboItem> CreateGen3(GameStrings s)
    {
        var locations = Util.GetCBList(s.metRSEFRLG_00000.AsSpan(0, 213));
        Util.AddCBWithOffset(locations, s.metRSEFRLG_00000.AsSpan(253, 3), 253);
        return locations;
    }

    private static List<ComboItem> CreateGen3CXD(GameStrings s)
    {
        var list = Util.GetCBList(s.metCXD_00000);
        list.RemoveAll(z => z.Text.Length == 0);
        return list;
    }

    private static List<ComboItem> CreateGen4(GameStrings s)
    {
        var locations = Util.GetCBList(s.metHGSS_00000, 0);
        Util.AddCBWithOffset(locations, s.metHGSS_02000, 2000, Locations.Daycare4);
        Util.AddCBWithOffset(locations, s.metHGSS_02000, 2000, Locations.LinkTrade4);
        Util.AddCBWithOffset(locations, s.metHGSS_03000, 3000, Locations.Ranger4);
        Util.AddCBWithOffset(locations, s.metHGSS_00000, 0000, Locations4.Met0);
        Util.AddCBWithOffset(locations, s.metHGSS_02000, 2000, Locations4.Met2);
        Util.AddCBWithOffset(locations, s.metHGSS_03000, 3000, Locations4.Met3);
        return locations;
    }

    private IReadOnlyList<ComboItem> CreateGen4Transfer()
    {
        // Pal Park to front
        var met = MetGen4.ToArray();
        var index = Array.FindIndex(met, z => z.Value == Locations.Transfer3);
        var pal = met[index];
        Array.Copy(met, 0, met, 1, index);
        met[0] = pal;
        return met;
    }

    private static List<ComboItem> CreateGen5(GameStrings s)
    {
        var locations = Util.GetCBList(s.metBW2_00000, 0);
        Util.AddCBWithOffset(locations, s.metBW2_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metBW2_30000, 30000, Locations.LinkTrade5);
        Util.AddCBWithOffset(locations, s.metBW2_00000, 00000, Locations5.Met0);
        Util.AddCBWithOffset(locations, s.metBW2_30000, 30000, Locations5.Met3);
        Util.AddCBWithOffset(locations, s.metBW2_40000, 40000, Locations5.Met4);
        Util.AddCBWithOffset(locations, s.metBW2_60000, 60000, Locations5.Met6);
        return locations;
    }

    private IReadOnlyList<ComboItem> CreateGen5Transfer()
    {
        // PokéTransfer to front
        var met = MetGen5.ToArray();
        var index = Array.FindIndex(met, z => z.Value == Locations.Transfer4);
        var xfr = met[index];
        Array.Copy(met, 0, met, 1, index);
        met[0] = xfr;
        return met;
    }

    private static List<ComboItem> CreateGen6(GameStrings s)
    {
        var locations = Util.GetCBList(s.metXY_00000, 0);
        Util.AddCBWithOffset(locations, s.metXY_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metXY_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metXY_00000, 00000, Locations6.Met0);
        Util.AddCBWithOffset(locations, s.metXY_30000, 30000, Locations6.Met3);
        Util.AddCBWithOffset(locations, s.metXY_40000, 40000, Locations6.Met4);
        Util.AddCBWithOffset(locations, s.metXY_60000, 60000, Locations6.Met6);
        return locations;
    }

    private static List<ComboItem> CreateGen7(GameStrings s)
    {
        var locations = Util.GetCBList(s.metSM_00000, 0);
        Util.AddCBWithOffset(locations, s.metSM_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metSM_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metSM_00000, 00000, Locations7.Met0);
        Util.AddCBWithOffset(locations, s.metSM_30000, 30000, Locations7.Met3);
        Util.AddCBWithOffset(locations, s.metSM_40000, 40000, Locations7.Met4);
        Util.AddCBWithOffset(locations, s.metSM_60000, 60000, Locations7.Met6);
        return locations;
    }

    private static List<ComboItem> CreateGen7GG(GameStrings s)
    {
        var locations = Util.GetCBList(s.metGG_00000, 0);
        Util.AddCBWithOffset(locations, s.metGG_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metGG_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metGG_00000, 00000, Locations7b.Met0);
        Util.AddCBWithOffset(locations, s.metGG_30000, 30000, Locations7b.Met3);
        Util.AddCBWithOffset(locations, s.metGG_40000, 40000, Locations7b.Met4);
        Util.AddCBWithOffset(locations, s.metGG_60000, 60000, Locations7b.Met6);
        return locations;
    }

    private static List<ComboItem> CreateGen8(GameStrings s)
    {
        var locations = Util.GetCBList(s.metSWSH_00000, 0);
        Util.AddCBWithOffset(locations, s.metSWSH_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metSWSH_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metSWSH_00000, 00000, Locations8.Met0);
        Util.AddCBWithOffset(locations, s.metSWSH_30000, 30000, Locations8.Met3);
        Util.AddCBWithOffset(locations, s.metSWSH_40000, 40000, Locations8.Met4);
        Util.AddCBWithOffset(locations, s.metSWSH_60000, 60000, Locations8.Met6);

        // Add in the BDSP+PLA magic met locations.
        locations.Add(new ComboItem($"{s.EggName} (BD/SP)", Locations.HOME_SWSHBDSPEgg));
        locations.Add(new ComboItem(s.gamelist[(int)BD], Locations.HOME_SWBD));
        locations.Add(new ComboItem(s.gamelist[(int)SP], Locations.HOME_SHSP));
        locations.Add(new ComboItem(s.gamelist[(int)PLA], Locations.HOME_SWLA));

        return locations;
    }

    private static List<ComboItem> CreateGen8a(GameStrings s)
    {
        var locations = Util.GetCBList(s.metLA_00000, 0);
        Util.AddCBWithOffset(locations, s.metLA_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metLA_00000, 00000, Locations8a.Met0);
        Util.AddCBWithOffset(locations, s.metLA_30000, 30000, Locations8a.Met3);
        Util.AddCBWithOffset(locations, s.metLA_40000, 40000, Locations8a.Met4);
        Util.AddCBWithOffset(locations, s.metLA_60000, 60000, Locations8a.Met6);

        // Add in the BDSP+PLA magic met locations.
        locations.Add(new ComboItem($"{s.EggName} (BD/SP)", Locations.HOME_SWSHBDSPEgg));
        locations.Add(new ComboItem(s.gamelist[(int)BD], Locations.HOME_SWBD));
        locations.Add(new ComboItem(s.gamelist[(int)SP], Locations.HOME_SHSP));
        locations.Add(new ComboItem(s.gamelist[(int)PLA], Locations.HOME_SWLA));

        return locations;
    }

    private static List<ComboItem> CreateGen8b(GameStrings s)
    {
        // Manually add invalid (-1) location from SWSH as ID 65535
        var locations = new List<ComboItem> { new(s.metSWSH_00000[0], Locations.Default8bNone) };
        Util.AddCBWithOffset(locations, s.metBDSP_60000, 60000, Locations.Daycare5);
        Util.AddCBWithOffset(locations, s.metBDSP_30000, 30000, Locations.LinkTrade6);
        Util.AddCBWithOffset(locations, s.metBDSP_00000, 00000, Locations8b.Met0);
        Util.AddCBWithOffset(locations, s.metBDSP_30000, 30000, Locations8b.Met3);
        Util.AddCBWithOffset(locations, s.metBDSP_40000, 40000, Locations8b.Met4);
        Util.AddCBWithOffset(locations, s.metBDSP_60000, 60000, Locations8b.Met6);
        return locations;
    }

    /// <summary>
    /// Fetches a Met Location list for a <see cref="version"/> that has been transferred away from and overwritten.
    /// </summary>
    /// <param name="version">Origin version</param>
    /// <param name="context">Current format context</param>
    /// <param name="egg">True if an egg location list, false if a regular met location list</param>
    /// <returns>Met location list</returns>
    public IReadOnlyList<ComboItem> GetLocationList(GameVersion version, EntityContext context, bool egg = false)
    {
        if (context == EntityContext.Gen2)
            return MetGen2;

        IReadOnlyList<ComboItem> result;
        if (egg && version < W && context.Generation() >= 5)
            result = MetGen4;
        else
            result = GetLocationListInternal(version, context);

        // Insert the BDSP none location if the format requires it.
        if (context is EntityContext.Gen8b && !BDSP.Contains(version))
        {
            var list = new List<ComboItem>(result.Count + 1);
            list.AddRange(result);
            list.Insert(1, new ComboItem($"{list[0].Text} (BD/SP)", Locations.Default8bNone));
            result = list;
        }

        return result;
    }

    private IReadOnlyList<ComboItem> GetLocationListInternal(GameVersion version, EntityContext context)
    {
        return version switch
        {
            CXD when context == EntityContext.Gen3 => MetGen3CXD,
            R or S when context == EntityContext.Gen3 => Partition1(MetGen3, z => z <= 87), // Ferry
            E when context == EntityContext.Gen3 => Partition1(MetGen3, z => z is <= 87 or (>= 197 and <= 212)), // Trainer Hill
            FR or LG when context == EntityContext.Gen3 => Partition1(MetGen3, z => z is > 87 and < 197), // Celadon Dept.
            D or P when context == EntityContext.Gen4 => Partition2(MetGen4, z => z <= 111, 4), // Battle Park
            Pt when context == EntityContext.Gen4 => Partition2(MetGen4, z => z <= 125, 4), // Rock Peak Ruins
            HG or SS when context == EntityContext.Gen4 => Partition2(MetGen4, z => z is > 125 and < 234, 4), // Celadon Dept.

            B or W => MetGen5,
            B2 or W2 => Partition2(MetGen5, z => z <= 116), // Abyssal Ruins
            X or Y => Partition2(MetGen6, z => z <= 168), // Unknown Dungeon
            OR or AS => Partition2(MetGen6, z => z is > 168 and <= 354), // Secret Base
            SN or MN => Partition2(MetGen7, z => z < 200), // Outer Cape
            US or UM
                or RD or BU or GN or YW
                or GD or SI or C => Partition2(MetGen7, z => z < 234), // Dividing Peak Tunnel
            GP or GE or GO => Partition2(MetGen7GG, z => z <= 54), // Pokémon League
            SW or SH => Partition2(MetGen8, z => z < 400),
            BD or SP => Partition2(MetGen8b, z => z < 628),
            PLA => Partition2(MetGen8a, z => z < 512),
            _ => new List<ComboItem>(GetLocationListModified(version, context)),
        };

        static IReadOnlyList<ComboItem> Partition1(IReadOnlyList<ComboItem> list, Func<int, bool> criteria)
        {
            var result = new ComboItem[list.Count];
            return GetOrderedList(list, result, criteria);
        }

        static IReadOnlyList<ComboItem> GetOrderedList(IReadOnlyList<ComboItem> list, ComboItem[] result,
            Func<int, bool> criteria, int start = 0)
        {
            // store values that match criteria at the next available position of the array
            // store non-matches starting at the end. reverse before returning
            int end = list.Count - 1;
            for (var index = start; index < list.Count; index++)
            {
                var item = list[index];
                if (criteria(item.Value))
                    result[start++] = item;
                else
                    result[end--] = item;
            }

            // since the non-matches are reversed in order, we swap them back since we know where they end up at.
            Array.Reverse(result, start, list.Count - start);
            return result;
        }

        static IReadOnlyList<ComboItem> Partition2(IReadOnlyList<ComboItem> list, Func<int, bool> criteria,
            int keepFirst = 3)
        {
            var result = new ComboItem[list.Count];
            for (int i = 0; i < keepFirst; i++)
                result[i] = list[i];
            return GetOrderedList(list, result, criteria, keepFirst);
        }
    }

    /// <summary>
    /// Fetches a Met Location list for a <see cref="version"/> that has been transferred away from and overwritten.
    /// </summary>
    /// <param name="version">Origin version</param>
    /// <param name="context">Current format context</param>
    /// <returns>Met location list</returns>
    private IReadOnlyList<ComboItem> GetLocationListModified(GameVersion version, EntityContext context) => version switch
    {
        <= CXD when context == EntityContext.Gen4 => MetGen4Transfer ??= CreateGen4Transfer(),
        < X when context.Generation() >= 5 => MetGen5Transfer ??= CreateGen5Transfer(),
        _ => Array.Empty<ComboItem>(),
    };
}