using NUnit.Framework;
using ProjectM.Simulation;

namespace ProjectM.Tests
{
    /// <summary>
    /// Pure-function tests for <see cref="ZoneEnemyMath"/> (no ECS world): the deterministic, save-reproducible
    /// expedition-wave composition. Pins the lower bound, the per-epoch ramp, and the grunt-heavy -> charger-heavy
    /// shift (grunt count held fixed; the per-epoch growth is all chargers).
    /// </summary>
    public class ZoneEnemyMathTests
    {
        [Test]
        public void WaveSize_LowerBoundedAtOne()
        {
            Assert.AreEqual(1, ZoneEnemyMath.WaveSize(0, 0, 0), "an occupied expedition always has at least one enemy");
            Assert.AreEqual(1, ZoneEnemyMath.WaveSize(-5, 0, 0), "epoch is floored at 1 internally");
        }

        [Test]
        public void WaveSize_BaselinePlusOnePerEpoch()
        {
            Assert.AreEqual(5, ZoneEnemyMath.WaveSize(1, 4, 1), "epoch 1: 4 grunts + 1 charger");
            Assert.AreEqual(7, ZoneEnemyMath.WaveSize(3, 4, 1), "epoch 3: baseline 5 + (3-1) ramp");
        }

        [Test]
        public void IsChargerSlot_Epoch1_GruntsFirst_OneChargerLast()
        {
            // epoch 1, G=4 C=1 -> size 5, only the last slot is a charger.
            Assert.IsFalse(ZoneEnemyMath.IsChargerSlot(1, 0, 4, 1));
            Assert.IsFalse(ZoneEnemyMath.IsChargerSlot(1, 3, 4, 1));
            Assert.IsTrue(ZoneEnemyMath.IsChargerSlot(1, 4, 4, 1));
        }

        [Test]
        public void Composition_GruntCountFixed_ChargerShareGrowsWithEpoch()
        {
            AssertComposition(epoch: 1, grunts: 4, chargers: 1, expectGrunts: 4, expectChargers: 1);
            AssertComposition(epoch: 5, grunts: 4, chargers: 1, expectGrunts: 4, expectChargers: 5);
        }

        static void AssertComposition(int epoch, int grunts, int chargers, int expectGrunts, int expectChargers)
        {
            int size = ZoneEnemyMath.WaveSize(epoch, grunts, chargers);
            int g = 0, c = 0;
            for (int slot = 0; slot < size; slot++)
                if (ZoneEnemyMath.IsChargerSlot(epoch, slot, grunts, chargers)) c++; else g++;
            Assert.AreEqual(expectGrunts, g, $"grunt count at epoch {epoch}");
            Assert.AreEqual(expectChargers, c, $"charger count at epoch {epoch}");
        }

        [Test]
        public void IsChargerSlot_Deterministic()
        {
            for (int slot = 0; slot < 9; slot++)
                Assert.AreEqual(ZoneEnemyMath.IsChargerSlot(5, slot, 4, 1), ZoneEnemyMath.IsChargerSlot(5, slot, 4, 1));
        }
    }
}