using System;
using System.Collections.Generic;
using static System.Buffers.Binary.BinaryPrimitives;

namespace PKHeX.Core;

/// <summary>
/// Mystery Gift Template File
/// </summary>
public abstract class MysteryGift : IEncounterable, IMoveset, IRelearn
{
    /// <summary>
    /// Determines whether or not the given length of bytes is valid for a mystery gift.
    /// </summary>
    /// <param name="len">Length, in bytes, of the data of which to determine validity.</param>
    /// <returns>A boolean indicating whether or not the given length is valid for a mystery gift.</returns>
    public static bool IsMysteryGift(long len) => Sizes.Contains((int)len);

    private static readonly HashSet<int> Sizes = new() { WA8.Size, WB8.Size, WC8.Size, WC6Full.Size, WC6.Size, PGF.Size, PGT.Size, PCD.Size };

    /// <summary>
    /// Converts the given data to a <see cref="MysteryGift"/>.
    /// </summary>
    /// <param name="data">Raw data of the mystery gift.</param>
    /// <param name="ext">Extension of the file from which the <paramref name="data"/> was retrieved.</param>
    /// <returns>An instance of <see cref="MysteryGift"/> representing the given data, or null if <paramref name="data"/> or <paramref name="ext"/> is invalid.</returns>
    /// <remarks>This overload differs from <see cref="GetMysteryGift(byte[])"/> by checking the <paramref name="data"/>/<paramref name="ext"/> combo for validity.  If either is invalid, a null reference is returned.</remarks>
    public static DataMysteryGift? GetMysteryGift(byte[] data, string ext) => data.Length switch
    {
        PGT.Size when ext == ".pgt" => new PGT(data),
        PCD.Size when ext is ".pcd" or ".wc4" => new PCD(data),
        PGF.Size when ext == ".pgf" => new PGF(data),
        WC6.Size when ext == ".wc6" => new WC6(data),
        WC7.Size when ext == ".wc7" => new WC7(data),
        WB7.Size when ext == ".wb7" => new WB7(data),
        WR7.Size when ext == ".wr7" => new WR7(data),
        WC8.Size when ext is ".wc8" or ".wc8full" => new WC8(data),
        WB8.Size when ext is ".wb8" => new WB8(data),
        WA8.Size when ext is ".wa8" => new WA8(data),
        WC9.Size when ext is ".wc9" => new WC9(data),

        WB7.SizeFull when ext == ".wb7full" => new WB7(data),
        WC6Full.Size when ext == ".wc6full" => new WC6Full(data).Gift,
        WC7Full.Size when ext == ".wc7full" => new WC7Full(data).Gift,
        _ => null,
    };

    /// <summary>
    /// Converts the given data to a <see cref="MysteryGift"/>.
    /// </summary>
    /// <param name="data">Raw data of the mystery gift.</param>
    /// <returns>An instance of <see cref="MysteryGift"/> representing the given data, or null if <paramref name="data"/> is invalid.</returns>
    public static DataMysteryGift? GetMysteryGift(byte[] data) => data.Length switch
    {
        PGT.Size => new PGT(data),
        PCD.Size => new PCD(data),
        PGF.Size => new PGF(data),
        WR7.Size => new WR7(data),
        WC8.Size => new WC8(data),
        WB8.Size => new WB8(data),

        // WA8/WC9: WA8 CardType >0 for wa8, 0 for wc9.
        WA8.Size => data[0xF] > 0 ? new WA8(data) : new WC9(data),

        // WC6/WC7: Check year
        WC6.Size => ReadUInt32LittleEndian(data.AsSpan(0x4C)) / 10000 < 2000 ? new WC7(data) : new WC6(data),
        // WC6Full/WC7Full: 0x205 has 3 * 0x46 for gen6, now only 2.
        WC6Full.Size => data[0x205] == 0 ? new WC7Full(data).Gift : new WC6Full(data).Gift,
        _ => null,
    };

    public string Extension => GetType().Name.ToLowerInvariant();
    public string FileName => $"{CardHeader}.{Extension}";
    public abstract int Generation { get; }
    public abstract EntityContext Context { get; }

    public PKM ConvertToPKM(ITrainerInfo tr) => ConvertToPKM(tr, EncounterCriteria.Unrestricted);
    public abstract PKM ConvertToPKM(ITrainerInfo tr, EncounterCriteria criteria);

    public abstract bool IsMatchExact(PKM pk, EvoCriteria evo);
    protected abstract bool IsMatchDeferred(PKM pk);
    protected abstract bool IsMatchPartial(PKM pk);

    public EncounterMatchRating GetMatchRating(PKM pk)
    {
        if (IsMatchPartial(pk))
            return EncounterMatchRating.PartialMatch;
        if (IsMatchDeferred(pk))
            return EncounterMatchRating.Deferred;
        return EncounterMatchRating.Match;
    }

    /// <summary>
    /// Creates a deep copy of the <see cref="MysteryGift"/> object data.
    /// </summary>
    public abstract MysteryGift Clone();

    /// <summary>
    /// Gets a friendly name for the underlying <see cref="MysteryGift"/> type.
    /// </summary>
    public string Type => GetType().Name;

    /// <summary>
    /// Gets a friendly name for the underlying <see cref="MysteryGift"/> type for the <see cref="IEncounterable"/> interface.
    /// </summary>
    public string Name => "Event Gift";

    /// <summary>
    /// Gets a friendly name for the underlying <see cref="MysteryGift"/> type for the <see cref="IEncounterable"/> interface.
    /// </summary>
    public string LongName => $"{Name} ({Type})";

    public virtual GameVersion Version
    {
        get => GameUtil.GetVersion(Generation);
        set { }
    }

    // Properties
    public virtual ushort Species { get => 0; set { } }
    public abstract AbilityPermission Ability { get; }
    public abstract bool GiftUsed { get; set; }
    public abstract string CardTitle { get; set; }
    public abstract int CardID { get; set; }

    public abstract bool IsItem { get; set; }
    public abstract int ItemID { get; set; }

    public abstract bool IsEntity { get; set; }
    public virtual int Quantity { get => 1; set { } }
    public virtual bool Empty => false;

    public virtual string CardHeader => (CardID > 0 ? $"Card #: {CardID:0000}" : "N/A") + $" - {CardTitle.Replace('\u3000',' ').Trim()}";

    // Search Properties
    public virtual Moveset Moves { get => default; set { } }
    public virtual Moveset Relearn { get => default; set { } }
    public virtual int[] IVs { get => Array.Empty<int>(); set { } }
    public virtual bool HasFixedIVs => true;
    public virtual void GetIVs(Span<int> value) { }
    public virtual bool IsShiny => false;

    public virtual Shiny Shiny
    {
        get => Shiny.Never;
        init => throw new InvalidOperationException();
    }

    public virtual bool IsEgg { get => false; set { } }
    public virtual int HeldItem { get => -1; set { } }
    public virtual int AbilityType { get => -1; set { } }
    public abstract int Gender { get; set; }
    public abstract byte Form { get; set; }
    public abstract int TID { get; set; }
    public abstract int SID { get; set; }
    public abstract string OT_Name { get; set; }
    public abstract int Location { get; set; }

    public abstract byte Level { get; set; }
    public byte LevelMin => Level;
    public byte LevelMax => Level;
    public abstract int Ball { get; set; }
    public virtual bool EggEncounter => IsEgg;
    public abstract int EggLocation { get; set; }

    protected virtual bool IsMatchEggLocation(PKM pk)
    {
        var expect = EggEncounter ? EggLocation : pk is PB8 ? Locations.Default8bNone : 0;
        return pk.Egg_Location == expect;
    }

    public Ball FixedBall => (Ball)Ball;

    public int TrainerID7 => (int)((uint)(TID | (SID << 16)) % 1000000);
    public int TrainerSID7 => (int)((uint)(TID | (SID << 16)) / 1000000);

    /// <summary>
    /// Checks if the <see cref="PKM"/> has the <see cref="move"/> in its current move list.
    /// </summary>
    public bool HasMove(ushort move) => Moves.Contains(move);
}