using PkmnLib.Dynamic.Libraries;
using PkmnLib.Dynamic.Models;
using PkmnLib.Dynamic.ScriptHandling;
using PkmnLib.Plugin.Gen7.Scripts.Moves;
using PkmnLib.Static;
using PkmnLib.Static.Libraries;
using PkmnLib.Static.Utils;

namespace PkmnLib.Plugin.Gen7.Tests.Scripts.Moves;

/// <summary>
/// Tests for the <see cref="HiddenPower"/> move script.
/// Gen VII Bulbapedia behavior: "Hidden Power can be any type, other than Normal and Fairy, based on its user's
/// IVs." and "From Generation VI onward, its power is fixed at 60."
/// </summary>
public class HiddenPowerTests
{
    public record TestCaseData(IndividualValueStatisticSet Ivs, StringKey ExpectedType)
    {
        /// <inheritdoc />
        public override string ToString() =>
            $"Hidden Power type is {ExpectedType} " +
            $"with IVs: HP {Ivs.Hp}, Atk {Ivs.Attack}, Def {Ivs.Defense}, SpA {Ivs.SpecialAttack}, SpD {Ivs.SpecialDefense}, Spe {Ivs.Speed}";
    }

    /// <summary>
    /// Rows of the Bulbapedia type-determination formula: the type index is
    /// (a + 2b + 4c + 8d + 16e + 32f) × 15 / 63 rounded down, where a–f are the least significant bits of the
    /// HP, Attack, Defense, Speed, Special Attack, and Special Defense IVs, and index 0 is Fighting through
    /// index 15 being Dark.
    /// </summary>
    public static IEnumerable<Func<TestCaseData>> HiddenPowerTestData()
    {
        // All-even IVs: formula value 0 -> the lowest possible type, Fighting.
        yield return () => new TestCaseData(new IndividualValueStatisticSet(0, 0, 0, 0, 0, 0), "fighting");
        // Only the Speed IV is odd: formula value 8 -> 8 * 15 / 63 = 1, Flying.
        yield return () => new TestCaseData(new IndividualValueStatisticSet(0, 0, 0, 0, 0, 1), "flying");
        // All-odd IVs: formula value 63 -> the highest possible type, Dark.
        yield return () => new TestCaseData(new IndividualValueStatisticSet(31, 31, 31, 31, 31, 31), "dark");
        yield return () => new TestCaseData(new IndividualValueStatisticSet(25, 2, 12, 5, 8, 17), "bug");
        yield return () => new TestCaseData(new IndividualValueStatisticSet(29, 19, 18, 22, 15, 28), "fire");
    }

    /// <summary>
    /// Creates a type library holding all 18 Gen VII types, registered in the National Pokédex type order.
    /// </summary>
    private static TypeLibrary CreateTypeLibrary()
    {
        var typeLibrary = new TypeLibrary();
        typeLibrary.RegisterType("normal");
        typeLibrary.RegisterType("fighting");
        typeLibrary.RegisterType("flying");
        typeLibrary.RegisterType("poison");
        typeLibrary.RegisterType("ground");
        typeLibrary.RegisterType("rock");
        typeLibrary.RegisterType("bug");
        typeLibrary.RegisterType("ghost");
        typeLibrary.RegisterType("steel");
        typeLibrary.RegisterType("fire");
        typeLibrary.RegisterType("water");
        typeLibrary.RegisterType("grass");
        typeLibrary.RegisterType("electric");
        typeLibrary.RegisterType("psychic");
        typeLibrary.RegisterType("ice");
        typeLibrary.RegisterType("dragon");
        typeLibrary.RegisterType("dark");
        typeLibrary.RegisterType("fairy");
        return typeLibrary;
    }

    /// <summary>
    /// Creates a mocked executing move whose user has the given IVs and a library containing all 18 types.
    /// </summary>
    private static (IExecutingMove executingMove, IBattlePokemon target) CreateTestSetup(
        IndividualValueStatisticSet ivs)
    {
        var executingMove = Substitute.For<IExecutingMove>();
        var user = Substitute.For<IBattlePokemon>();
        var target = Substitute.For<IBattlePokemon>();
        var dynamicLibrary = Substitute.For<IDynamicLibrary>();
        var staticLibrary = Substitute.For<IStaticLibrary>();

        executingMove.User.Returns(user);
        user.IndividualValues.Returns(ivs);
        user.Library.Returns(dynamicLibrary);
        staticLibrary.Types.Returns(CreateTypeLibrary());
        dynamicLibrary.StaticLibrary.Returns(staticLibrary);
        return (executingMove, target);
    }

    /// <summary>
    /// Bulbapedia: "Hidden Power can be any type, other than Normal and Fairy, based on its user's IVs."
    /// The type index is (a + 2b + 4c + 8d + 16e + 32f) × 15 / 63 rounded down, where a–f are the least
    /// significant bits of the HP, Attack, Defense, Speed, Special Attack, and Special Defense IVs.
    /// </summary>
    [Test, MethodDataSource(nameof(HiddenPowerTestData))]
    public async Task HiddenPower_ChangesType(TestCaseData test)
    {
        var (executingMove, target) = CreateTestSetup(test.Ivs);

        TypeIdentifier? moveType = new TypeIdentifier(1, "normal");

        var hiddenPower = new HiddenPower();
        hiddenPower.ChangeMoveType(executingMove, target, 0, ref moveType);

        await Assert.That(moveType!.Value.Name).IsEqualTo(test.ExpectedType);
    }

    /// <summary>
    /// Bulbapedia: "Hidden Power can be any type, other than Normal and Fairy, based on its user's IVs."
    /// The type only depends on the least significant bit of each of the six IVs, so checking all 64 parity
    /// combinations exhaustively proves the move can never be Normal or Fairy.
    /// </summary>
    [Test]
    public async Task ChangeMoveType_AllIvParityCombinations_TypeIsNeverNormalOrFairy()
    {
        for (byte combination = 0; combination < 64; combination++)
        {
            // Arrange - each bit of the combination becomes the least significant bit of one IV.
            var ivs = new IndividualValueStatisticSet((byte)(combination & 0x01), (byte)((combination >> 1) & 0x01),
                (byte)((combination >> 2) & 0x01), (byte)((combination >> 4) & 0x01), (byte)((combination >> 5) & 0x01),
                (byte)((combination >> 3) & 0x01));
            var (executingMove, target) = CreateTestSetup(ivs);
            TypeIdentifier? moveType = new TypeIdentifier(1, "normal");

            // Act
            var hiddenPower = new HiddenPower();
            hiddenPower.ChangeMoveType(executingMove, target, 0, ref moveType);

            // Assert
            await Assert.That(moveType!.Value.Name).IsNotEqualTo(new StringKey("normal"));
            await Assert.That(moveType!.Value.Name).IsNotEqualTo(new StringKey("fairy"));
        }
    }

    /// <summary>
    /// Bulbapedia: "From Generation VI onward, its power is fixed at 60." The pre-Gen-VI variable power formula
    /// no longer applies, so the script must leave the base power of 60 from the move data untouched, regardless
    /// of the user's IVs.
    /// </summary>
    [Test, MethodDataSource(nameof(HiddenPowerTestData))]
    public async Task ChangeBasePower_AnyIvs_PowerRemainsFixedAtSixty(TestCaseData test)
    {
        var hiddenPower = new HiddenPower();
        await Assert.That(hiddenPower).IsNotAssignableTo<IScriptChangeBasePower>();
    }
}