import { describe, it, expect, beforeEach } from 'vitest';
import { createWorld, addEntity, addComponent, query } from 'bitecs';
import {
  Position,
  Velocity,
  Health,
  SpriteRef,
  ChemicalComposition,
} from '../src/ecs/components';
import {
  createGameWorld,
  updateTime,
  type World,
} from '../src/ecs/world';
import {
  movementSystem,
  bounceSystem,
} from '../src/ecs/systems/movement';
import {
  healthSystem,
  applyDamage,
  applyHealing,
} from '../src/ecs/systems/health';
import {
  createGameEntity,
  removeGameEntity,
} from '../src/ecs/factory';

// ─── World ──────────────────────────────────────────────────────

describe('World', () => {
  it('creates a game world with zeroed time', () => {
    const gw = createGameWorld();
    expect(gw.world).toBeDefined();
    expect(gw.time.delta).toBe(0);
    expect(gw.time.elapsed).toBe(0);
    expect(gw.time.tick).toBe(0);
  });

  it('updates time tracking correctly', () => {
    const gw = createGameWorld();

    updateTime(gw, 16.67);
    expect(gw.time.delta).toBeCloseTo(16.67);
    expect(gw.time.elapsed).toBeCloseTo(16.67);
    expect(gw.time.tick).toBe(1);

    updateTime(gw, 16.67);
    expect(gw.time.delta).toBeCloseTo(16.67);
    expect(gw.time.elapsed).toBeCloseTo(33.34);
    expect(gw.time.tick).toBe(2);
  });

  it('tracks varying delta times', () => {
    const gw = createGameWorld();

    updateTime(gw, 10);
    updateTime(gw, 20);
    updateTime(gw, 30);

    expect(gw.time.delta).toBe(30);
    expect(gw.time.elapsed).toBe(60);
    expect(gw.time.tick).toBe(3);
  });
});

// ─── Components ─────────────────────────────────────────────────

describe('Components', () => {
  let world: World;

  beforeEach(() => {
    world = createWorld();
  });

  it('stores Position data for entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    Position.x[eid] = 100;
    Position.y[eid] = 200;

    expect(Position.x[eid]).toBe(100);
    expect(Position.y[eid]).toBe(200);
  });

  it('stores Velocity data for entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Velocity);
    Velocity.vx[eid] = 50;
    Velocity.vy[eid] = -30;

    expect(Velocity.vx[eid]).toBe(50);
    expect(Velocity.vy[eid]).toBe(-30);
  });

  it('stores Health data for entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 80;
    Health.max[eid] = 100;

    expect(Health.current[eid]).toBe(80);
    expect(Health.max[eid]).toBe(100);
  });

  it('stores SpriteRef data for entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, SpriteRef);
    SpriteRef.color[eid] = 0x00ff88;
    SpriteRef.radius[eid] = 12;

    expect(SpriteRef.color[eid]).toBe(0x00ff88);
    expect(SpriteRef.radius[eid]).toBe(12);
  });

  it('stores ChemicalComposition for entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, ChemicalComposition);
    ChemicalComposition.primaryElement[eid] = 11; // Na

    expect(ChemicalComposition.primaryElement[eid]).toBe(11);
  });

  it('queries entities by single component', () => {
    const e1 = addEntity(world);
    const e2 = addEntity(world);
    addComponent(world, e1, Position);
    addComponent(world, e2, Position);

    const entities = [...query(world, [Position])];
    expect(entities).toContain(e1);
    expect(entities).toContain(e2);
  });

  it('queries entities by multiple components', () => {
    const moving = addEntity(world);
    const stationary = addEntity(world);

    addComponent(world, moving, Position);
    addComponent(world, moving, Velocity);
    addComponent(world, stationary, Position);

    const movingEntities = [...query(world, [Position, Velocity])];
    expect(movingEntities).toContain(moving);
    expect(movingEntities).not.toContain(stationary);
  });
});

// ─── Movement System ────────────────────────────────────────────

describe('Movement System', () => {
  let world: World;

  beforeEach(() => {
    world = createWorld();
  });

  it('updates position by velocity * delta', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 100;
    Position.y[eid] = 200;
    Velocity.vx[eid] = 60;
    Velocity.vy[eid] = -30;

    movementSystem(world, 1000); // 1 second

    expect(Position.x[eid]).toBeCloseTo(160);
    expect(Position.y[eid]).toBeCloseTo(170);
  });

  it('handles fractional delta (16.67ms ≈ 60fps)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 0;
    Position.y[eid] = 0;
    Velocity.vx[eid] = 100;
    Velocity.vy[eid] = 100;

    movementSystem(world, 16.67);

    expect(Position.x[eid]).toBeCloseTo(1.667, 1);
    expect(Position.y[eid]).toBeCloseTo(1.667, 1);
  });

  it('does not move entities without Velocity', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    Position.x[eid] = 100;
    Position.y[eid] = 200;

    movementSystem(world, 1000);

    expect(Position.x[eid]).toBe(100);
    expect(Position.y[eid]).toBe(200);
  });

  it('handles negative velocities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 500;
    Position.y[eid] = 500;
    Velocity.vx[eid] = -100;
    Velocity.vy[eid] = -200;

    movementSystem(world, 1000);

    expect(Position.x[eid]).toBeCloseTo(400);
    expect(Position.y[eid]).toBeCloseTo(300);
  });

  it('handles zero delta', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 100;
    Position.y[eid] = 200;
    Velocity.vx[eid] = 999;
    Velocity.vy[eid] = 999;

    movementSystem(world, 0);

    expect(Position.x[eid]).toBe(100);
    expect(Position.y[eid]).toBe(200);
  });

  it('moves multiple entities independently', () => {
    const e1 = addEntity(world);
    const e2 = addEntity(world);

    addComponent(world, e1, Position);
    addComponent(world, e1, Velocity);
    addComponent(world, e2, Position);
    addComponent(world, e2, Velocity);

    Position.x[e1] = 0;
    Position.y[e1] = 0;
    Velocity.vx[e1] = 100;
    Velocity.vy[e1] = 0;

    Position.x[e2] = 100;
    Position.y[e2] = 100;
    Velocity.vx[e2] = 0;
    Velocity.vy[e2] = -50;

    movementSystem(world, 1000);

    expect(Position.x[e1]).toBeCloseTo(100);
    expect(Position.y[e1]).toBeCloseTo(0);
    expect(Position.x[e2]).toBeCloseTo(100);
    expect(Position.y[e2]).toBeCloseTo(50);
  });
});

// ─── Bounce System ──────────────────────────────────────────────

describe('Bounce System', () => {
  let world: World;
  const WIDTH = 1280;
  const HEIGHT = 720;

  beforeEach(() => {
    world = createWorld();
  });

  it('bounces at left boundary (x < 0)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = -5;
    Position.y[eid] = 100;
    Velocity.vx[eid] = -100;
    Velocity.vy[eid] = 0;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.x[eid]).toBe(0);
    expect(Velocity.vx[eid]).toBe(100);
  });

  it('bounces at right boundary (x > width)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = WIDTH + 5;
    Position.y[eid] = 100;
    Velocity.vx[eid] = 100;
    Velocity.vy[eid] = 0;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.x[eid]).toBe(WIDTH);
    expect(Velocity.vx[eid]).toBe(-100);
  });

  it('bounces at top boundary (y < 0)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 100;
    Position.y[eid] = -10;
    Velocity.vx[eid] = 0;
    Velocity.vy[eid] = -50;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.y[eid]).toBe(0);
    expect(Velocity.vy[eid]).toBe(50);
  });

  it('bounces at bottom boundary (y > height)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 100;
    Position.y[eid] = HEIGHT + 10;
    Velocity.vx[eid] = 0;
    Velocity.vy[eid] = 200;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.y[eid]).toBe(HEIGHT);
    expect(Velocity.vy[eid]).toBe(-200);
  });

  it('does not affect entities within bounds', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = 640;
    Position.y[eid] = 360;
    Velocity.vx[eid] = 100;
    Velocity.vy[eid] = -50;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.x[eid]).toBe(640);
    expect(Position.y[eid]).toBe(360);
    expect(Velocity.vx[eid]).toBe(100);
    expect(Velocity.vy[eid]).toBe(-50);
  });

  it('handles corner bounce (both axes out of bounds)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    Position.x[eid] = -5;
    Position.y[eid] = -10;
    Velocity.vx[eid] = -100;
    Velocity.vy[eid] = -200;

    bounceSystem(world, WIDTH, HEIGHT);

    expect(Position.x[eid]).toBe(0);
    expect(Position.y[eid]).toBe(0);
    expect(Velocity.vx[eid]).toBe(100);
    expect(Velocity.vy[eid]).toBe(200);
  });
});

// ─── Health System ──────────────────────────────────────────────

describe('Health System', () => {
  let world: World;

  beforeEach(() => {
    world = createWorld();
  });

  it('detects entities with health = 0', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 0;
    Health.max[eid] = 100;

    const dead = healthSystem(world);
    expect(dead).toContain(eid);
  });

  it('detects entities with negative health', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = -50;
    Health.max[eid] = 100;

    const dead = healthSystem(world);
    expect(dead).toContain(eid);
  });

  it('does not flag healthy entities', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 50;
    Health.max[eid] = 100;

    const dead = healthSystem(world);
    expect(dead).not.toContain(eid);
  });

  it('returns empty array when all entities are healthy', () => {
    const e1 = addEntity(world);
    const e2 = addEntity(world);
    addComponent(world, e1, Health);
    addComponent(world, e2, Health);
    Health.current[e1] = 100;
    Health.max[e1] = 100;
    Health.current[e2] = 1;
    Health.max[e2] = 100;

    const dead = healthSystem(world);
    expect(dead).toHaveLength(0);
  });

  it('returns multiple dead entities', () => {
    const e1 = addEntity(world);
    const e2 = addEntity(world);
    const e3 = addEntity(world);
    addComponent(world, e1, Health);
    addComponent(world, e2, Health);
    addComponent(world, e3, Health);
    Health.current[e1] = 0;
    Health.max[e1] = 100;
    Health.current[e2] = -10;
    Health.max[e2] = 50;
    Health.current[e3] = 50;
    Health.max[e3] = 100;

    const dead = healthSystem(world);
    expect(dead).toContain(e1);
    expect(dead).toContain(e2);
    expect(dead).not.toContain(e3);
    expect(dead).toHaveLength(2);
  });
});

// ─── Damage & Healing ───────────────────────────────────────────

describe('Damage and Healing', () => {
  let world: World;

  beforeEach(() => {
    world = createWorld();
  });

  it('applies damage correctly', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 100;
    Health.max[eid] = 100;

    applyDamage(eid, 30);
    expect(Health.current[eid]).toBe(70);
  });

  it('allows overkill (negative health)', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 10;
    Health.max[eid] = 100;

    applyDamage(eid, 50);
    expect(Health.current[eid]).toBe(-40);
  });

  it('applies healing correctly', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 50;
    Health.max[eid] = 100;

    applyHealing(eid, 30);
    expect(Health.current[eid]).toBe(80);
  });

  it('caps healing at max health', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 90;
    Health.max[eid] = 100;

    applyHealing(eid, 50);
    expect(Health.current[eid]).toBe(100);
  });

  it('full damage → heal → kill lifecycle', () => {
    const eid = addEntity(world);
    addComponent(world, eid, Health);
    Health.current[eid] = 100;
    Health.max[eid] = 100;

    applyDamage(eid, 60);
    expect(Health.current[eid]).toBe(40);

    applyHealing(eid, 20);
    expect(Health.current[eid]).toBe(60);

    applyDamage(eid, 70);
    expect(Health.current[eid]).toBe(-10);

    const dead = healthSystem(world);
    expect(dead).toContain(eid);
  });
});

// ─── Entity Factory ─────────────────────────────────────────────

describe('Entity Factory', () => {
  let world: World;

  beforeEach(() => {
    world = createWorld();
  });

  it('creates entity with position only', () => {
    const eid = createGameEntity(world, {
      position: { x: 100, y: 200 },
    });

    expect(typeof eid).toBe('number');
    const entities = [...query(world, [Position])];
    expect(entities).toContain(eid);
    expect(Position.x[eid]).toBe(100);
    expect(Position.y[eid]).toBe(200);
  });

  it('creates entity with all components', () => {
    const eid = createGameEntity(world, {
      position: { x: 10, y: 20 },
      velocity: { vx: 30, vy: 40 },
      health: { current: 80, max: 100 },
      sprite: { color: 0xff0000, radius: 8 },
      chemicalElement: 26, // Fe
    });

    expect(Position.x[eid]).toBe(10);
    expect(Position.y[eid]).toBe(20);
    expect(Velocity.vx[eid]).toBe(30);
    expect(Velocity.vy[eid]).toBe(40);
    expect(Health.current[eid]).toBe(80);
    expect(Health.max[eid]).toBe(100);
    expect(SpriteRef.color[eid]).toBe(0xff0000);
    expect(SpriteRef.radius[eid]).toBe(8);
    expect(ChemicalComposition.primaryElement[eid]).toBe(26);
  });

  it('creates multiple independent entities', () => {
    const e1 = createGameEntity(world, {
      position: { x: 0, y: 0 },
    });
    const e2 = createGameEntity(world, {
      position: { x: 100, y: 100 },
    });

    expect(e1).not.toBe(e2);
    expect(Position.x[e1]).toBe(0);
    expect(Position.x[e2]).toBe(100);
  });

  it('removes entity from world', () => {
    const eid = createGameEntity(world, {
      position: { x: 100, y: 200 },
      health: { current: 50, max: 100 },
    });

    expect([...query(world, [Position])]).toContain(eid);

    removeGameEntity(world, eid);

    expect([...query(world, [Position])]).not.toContain(eid);
  });

  it('creates entity without any components', () => {
    const eid = createGameEntity(world, {});
    expect(typeof eid).toBe('number');
  });
});

// ─── Integration ────────────────────────────────────────────────

describe('Integration', () => {
  it('full lifecycle: create → move → damage → die → remove', () => {
    const { world } = createGameWorld();

    const eid = createGameEntity(world, {
      position: { x: 100, y: 100 },
      velocity: { vx: 200, vy: 0 },
      health: { current: 50, max: 100 },
    });

    // Move for 1 second
    movementSystem(world, 1000);
    expect(Position.x[eid]).toBeCloseTo(300);

    // Lethal damage
    applyDamage(eid, 60);
    expect(Health.current[eid]).toBe(-10);

    // Health system detects death
    const dead = healthSystem(world);
    expect(dead).toContain(eid);

    // Remove dead entity
    removeGameEntity(world, eid);
    expect([...query(world, [Health])]).not.toContain(eid);
  });

  it('movement + bounce in sequence', () => {
    const { world } = createGameWorld();

    const eid = createGameEntity(world, {
      position: { x: 1270, y: 360 },
      velocity: { vx: 100, vy: 0 },
    });

    // Move past right boundary (1270 + 100*0.5 = 1320 > 1280)
    movementSystem(world, 500);
    expect(Position.x[eid]).toBeCloseTo(1320);

    // Bounce should clamp and reverse
    bounceSystem(world, 1280, 720);
    expect(Position.x[eid]).toBe(1280);
    expect(Velocity.vx[eid]).toBe(-100);

    // Next frame: move away from boundary
    movementSystem(world, 1000);
    expect(Position.x[eid]).toBeCloseTo(1180);
  });
});