/**
 * Projectile System Tests — Phase 4.5
 *
 * Tests: projectile creation, direction calculation,
 * lifetime expiry, tile collision removal.
 */

import { describe, it, expect } from 'vitest';
import { createWorld, addEntity, addComponent, query } from 'bitecs';
import { Position, Velocity, Projectile, SpriteRef } from '../src/ecs/components';
import {
  launchProjectile,
  projectileSystem,
  calculateDirection,
  type ProjectileData,
  PROJECTILE_SPEED,
  PROJECTILE_LIFETIME,
} from '../src/player/projectile';

// === Direction Calculation ===

describe('calculateDirection', () => {
  it('normalizes direction vector', () => {
    const d = calculateDirection(0, 0, 100, 0);
    expect(d.dx).toBeCloseTo(1);
    expect(d.dy).toBeCloseTo(0);
  });

  it('handles diagonal direction', () => {
    const d = calculateDirection(0, 0, 100, 100);
    const mag = Math.sqrt(d.dx * d.dx + d.dy * d.dy);
    expect(mag).toBeCloseTo(1);
  });

  it('handles negative direction', () => {
    const d = calculateDirection(100, 100, 0, 0);
    expect(d.dx).toBeCloseTo(-1 / Math.SQRT2);
    expect(d.dy).toBeCloseTo(-1 / Math.SQRT2);
  });

  it('returns zero for same position', () => {
    const d = calculateDirection(50, 50, 50, 50);
    expect(d.dx).toBe(1); // default to right
    expect(d.dy).toBe(0);
  });
});

// === Launch Projectile ===

describe('launchProjectile', () => {
  it('creates entity at source position', () => {
    const world = createWorld();
    const projData = new Map<number, ProjectileData>();

    const eid = launchProjectile(world, projData, 100, 200, 200, 200, 'Na');

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

  it('sets velocity toward target', () => {
    const world = createWorld();
    const projData = new Map<number, ProjectileData>();

    const eid = launchProjectile(world, projData, 0, 0, 100, 0, 'Na');

    expect(Velocity.vx[eid]).toBeCloseTo(PROJECTILE_SPEED);
    expect(Velocity.vy[eid]).toBeCloseTo(0);
  });

  it('stores chemical data', () => {
    const world = createWorld();
    const projData = new Map<number, ProjectileData>();

    const eid = launchProjectile(world, projData, 0, 0, 100, 0, 'Na');

    expect(projData.get(eid)).toBeDefined();
    expect(projData.get(eid)!.itemId).toBe('Na');
  });

  it('sets lifetime', () => {
    const world = createWorld();
    const projData = new Map<number, ProjectileData>();

    const eid = launchProjectile(world, projData, 0, 0, 100, 0, 'Na');

    expect(Projectile.lifetime[eid]).toBe(PROJECTILE_LIFETIME);
  });

  it('sets sprite with element color', () => {
    const world = createWorld();
    const projData = new Map<number, ProjectileData>();

    const eid = launchProjectile(world, projData, 0, 0, 100, 0, 'Na');

    expect(SpriteRef.radius[eid]).toBeGreaterThan(0);
    expect(SpriteRef.color[eid]).toBeDefined();
  });
});

// === Projectile System ===

describe('projectileSystem', () => {
  it('decrements lifetime', () => {
    const world = createWorld();
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    addComponent(world, eid, Projectile);
    Position.x[eid] = 48;
    Position.y[eid] = 48;
    Velocity.vx[eid] = 100;
    Velocity.vy[eid] = 0;
    Projectile.lifetime[eid] = 1000;

    const grid = [[0, 0, 0], [0, 0, 0], [0, 0, 0]];
    const walkable = new Set([0]);
    const projData = new Map<number, ProjectileData>();
    projData.set(eid, { itemId: 'Na' });

    projectileSystem(world, 100, grid, 32, walkable, projData);

    expect(Projectile.lifetime[eid]).toBe(900);
  });

  it('removes expired projectiles', () => {
    const world = createWorld();
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    addComponent(world, eid, Projectile);
    Position.x[eid] = 48;
    Position.y[eid] = 48;
    Projectile.lifetime[eid] = 50;

    const grid = [[0, 0, 0], [0, 0, 0], [0, 0, 0]];
    const walkable = new Set([0]);
    const projData = new Map<number, ProjectileData>();
    projData.set(eid, { itemId: 'Na' });

    projectileSystem(world, 100, grid, 32, walkable, projData);

    expect(query(world, [Projectile]).length).toBe(0);
    expect(projData.size).toBe(0);
  });

  it('removes projectiles on non-walkable tile', () => {
    const world = createWorld();
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    addComponent(world, eid, Projectile);
    // Position on non-walkable tile (1,1) = tile 3
    Position.x[eid] = 48;
    Position.y[eid] = 48;
    Projectile.lifetime[eid] = 5000;

    const grid = [[0, 0, 0], [0, 3, 0], [0, 0, 0]];
    const walkable = new Set([0]);
    const projData = new Map<number, ProjectileData>();
    projData.set(eid, { itemId: 'Na' });

    projectileSystem(world, 16, grid, 32, walkable, projData);

    expect(query(world, [Projectile]).length).toBe(0);
  });

  it('keeps valid projectiles alive', () => {
    const world = createWorld();
    const eid = addEntity(world);
    addComponent(world, eid, Position);
    addComponent(world, eid, Velocity);
    addComponent(world, eid, Projectile);
    Position.x[eid] = 48;
    Position.y[eid] = 48;
    Projectile.lifetime[eid] = 5000;

    const grid = [[0, 0, 0], [0, 0, 0], [0, 0, 0]];
    const walkable = new Set([0]);
    const projData = new Map<number, ProjectileData>();
    projData.set(eid, { itemId: 'Na' });

    projectileSystem(world, 16, grid, 32, walkable, projData);

    expect(query(world, [Projectile]).length).toBe(1);
    expect(projData.size).toBe(1);
  });
});