package com.mythlane.chainlightning.chain;

import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

final class Vec3Test {

    @Test
    void distanceSquared_zeroToZero_isZero() {
        Vec3 a = new Vec3(0, 0, 0);
        assertEquals(0.0, a.distanceSquared(a), 1e-9);
    }

    @Test
    void distanceSquared_pythagorean345_is25() {
        Vec3 a = new Vec3(0, 0, 0);
        Vec3 b = new Vec3(3, 4, 0);
        assertEquals(25.0, a.distanceSquared(b), 1e-9);
    }

    @Test
    void distanceSquared_isCommutative() {
        Vec3 a = new Vec3(1, 2, 3);
        Vec3 b = new Vec3(-4, 5, 6);
        assertEquals(a.distanceSquared(b), b.distanceSquared(a), 1e-9);
    }

    @Test
    void distance_pythagorean345_is5() {
        Vec3 a = new Vec3(0, 0, 0);
        Vec3 b = new Vec3(3, 4, 0);
        assertEquals(5.0, a.distance(b), 1e-9);
    }

    @Test
    void distanceSquared_negativeCoordinates_works() {
        Vec3 a = new Vec3(-1, -1, -1);
        Vec3 b = new Vec3(1, 1, 1);
        assertEquals(12.0, a.distanceSquared(b), 1e-9);
        assertTrue(a.distance(b) > 3.4 && a.distance(b) < 3.5);
    }

    @Test
    void lerpAtZeroReturnsFrom() {
        Vec3 from = Vec3.ZERO;
        Vec3 to = new Vec3(10, 10, 10);
        Vec3 result = from.lerp(to, 0.0);
        assertEquals(from.x(), result.x(), 1e-9);
        assertEquals(from.y(), result.y(), 1e-9);
        assertEquals(from.z(), result.z(), 1e-9);
    }

    @Test
    void lerpAtOneReturnsTo() {
        Vec3 from = Vec3.ZERO;
        Vec3 to = new Vec3(10, 10, 10);
        Vec3 result = from.lerp(to, 1.0);
        assertEquals(to.x(), result.x(), 1e-9);
        assertEquals(to.y(), result.y(), 1e-9);
        assertEquals(to.z(), result.z(), 1e-9);
    }

    @Test
    void lerpAtHalfReturnsMidpoint() {
        Vec3 from = new Vec3(0, 0, 0);
        Vec3 to = new Vec3(10, 0, 0);
        Vec3 result = from.lerp(to, 0.5);
        assertEquals(5.0, result.x(), 1e-9);
        assertEquals(0.0, result.y(), 1e-9);
        assertEquals(0.0, result.z(), 1e-9);
    }
}