using PkmnLib.Dynamic.Models;
using PkmnLib.Plugin.Gen7.Scripts.Moves;

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

/// <summary>
/// Tests for the <see cref="Frustration"/> move script.
/// Gen VII Bulbapedia behavior: "Frustration inflicts damage and has no secondary effect. The base power of
/// Frustration is dependent on the user's friendship. The lower the user's friendship is, the greater the
/// base power of Frustration." The power formula is Power = (255 − Friendship) × 2 / 5, and from Generation
/// III to VII, "if calculations yielded zero, the move's power becomes 1 instead".
/// </summary>
public class FrustrationTests
{
    /// <summary>
    /// Creates a fully mocked test setup with a user that has the given friendship value.
    /// </summary>
    private static (Frustration script, IExecutingMove move, IBattlePokemon target) CreateTestSetup(byte friendship)
    {
        var script = new Frustration();
        var move = Substitute.For<IExecutingMove>();
        var target = Substitute.For<IBattlePokemon>();
        var user = Substitute.For<IBattlePokemon>();
        user.Happiness.Returns(friendship);
        move.User.Returns(user);
        return (script, move, target);
    }

    /// <summary>
    /// Bulbapedia: "The base power of Frustration is dependent on the user's friendship. The lower the
    /// user's friendship is, the greater the base power of Frustration." The power formula is
    /// Power = (255 − Friendship) × 2 / 5, with integer truncation.
    /// </summary>
    [Test, Arguments((byte)0, (ushort)102), Arguments((byte)50, (ushort)82), Arguments((byte)100, (ushort)62),
     Arguments((byte)128, (ushort)50), Arguments((byte)200, (ushort)22), Arguments((byte)250, (ushort)2)]
    public async Task ChangeBasePower_FriendshipValue_MatchesFormula(byte friendship, ushort expectedPower)
    {
        // Arrange
        var (script, move, target) = CreateTestSetup(friendship);
        ushort basePower = 102;

        // Act
        script.ChangeBasePower(move, target, 0, ref basePower);

        // Assert
        await Assert.That(basePower).IsEqualTo(expectedPower);
    }

    /// <summary>
    /// Bulbapedia (Generations III to VII): the formula was adjusted so "if calculations yielded zero, the
    /// move's power becomes 1 instead". Friendship values of 253 and above yield 0 from the formula, so the
    /// power becomes 1.
    /// </summary>
    [Test, Arguments((byte)253), Arguments((byte)254), Arguments((byte)255)]
    public async Task ChangeBasePower_FriendshipNearMaximum_PowerIsMinimumOne(byte friendship)
    {
        // Arrange
        var (script, move, target) = CreateTestSetup(friendship);
        ushort basePower = 102;

        // Act
        script.ChangeBasePower(move, target, 0, ref basePower);

        // Assert
        await Assert.That(basePower).IsEqualTo((ushort)1);
    }

    /// <summary>
    /// Bulbapedia: "The lower the user's friendship is, the greater the base power of Frustration." — at 0
    /// friendship the move reaches its maximum power of 102.
    /// </summary>
    [Test]
    public async Task ChangeBasePower_ZeroFriendship_PowerIsMaximum102()
    {
        // Arrange
        var (script, move, target) = CreateTestSetup(0);
        ushort basePower = 102;

        // Act
        script.ChangeBasePower(move, target, 0, ref basePower);

        // Assert
        await Assert.That(basePower).IsEqualTo((ushort)102);
    }

    /// <summary>
    /// The power is derived purely from the user's friendship: the incoming base power value does not
    /// influence the result.
    /// </summary>
    [Test]
    public async Task ChangeBasePower_DifferentIncomingBasePower_ResultDependsOnlyOnFriendship()
    {
        // Arrange
        var (script, move, target) = CreateTestSetup(100);
        ushort basePowerLow = 1;
        ushort basePowerHigh = 250;

        // Act
        script.ChangeBasePower(move, target, 0, ref basePowerLow);
        script.ChangeBasePower(move, target, 0, ref basePowerHigh);

        // Assert
        await Assert.That(basePowerLow).IsEqualTo((ushort)62);
        await Assert.That(basePowerHigh).IsEqualTo((ushort)62);
    }
}