import { describe, it, beforeEach, mock } from 'node:test';
import assert from 'node:assert';
import Serpentity, { Component, Entity, Node, System } from '../lib/serpentity.js';

const internals = {
  context: {},
  system: class TestSystem extends System {
    added(engine) {

      this.testNodes = engine.getNodes(internals.node);
      this.addedCalled = true;
      this.addedEngine = engine;
      this.emittedEvents = [];
      this.beforeCall = null;
      this.afterCall = null;

      this.changeObserver = (event) => {
          this.emittedEvents.push(event)
      };

      this.nodeAddedObserver = ({ node }) => {
        node.test.addEventListener('change', this.changeObserver);
      };

      this.nodeRemovedObserver = ({ node }) => {
        node.test.removeEventListener('change', this.changeObserver);
      };

      for (const node of this.testNodes) {
        node.test.addEventListener('change', this.changeObserver);
      }

      this.testNodes.addEventListener('nodeAdded', this.nodeAddedObserver);
      this.testNodes.addEventListener('nodeRemoved', this.nodeRemovedObserver);

      super.added(); // not needed, but takes care of coverage :P
    }

    removed(engine) {

      this.testNodes.removeEventListener('nodeAdded', this.nodeAddedObserver);
      this.nodeAddedObserver = null;

      this.testNodes.removeEventListener('nodeRemoved', this.nodeRemovedObserver);
      this.nodeRemovedObserver = null;

      for (const node of this.testNodes) {
        node.test.removeEventListener('change', this.changeObserver);
      }
      this.changeObserver = null;

      this.testNodes = null;
      this.removedCalled = true;
      this.removedEngine = engine;
      this.emittedEvents = null;
      this.beforeCall = null;
      this.afterCall = null;
      super.removed(); // not needed, but takes care of coverage :P
    }

    update(dt) {

      this.updateCalled = Date.now();
      this.updateDt = dt;

      for (const node of this.testNodes) {
        this.beforeCall = this.beforeCall === null ? node.test.called : this.beforeCall;
        node.test.called = true;
        this.afterCall = this.afterCall === null ? node.test.called : this.afterCall;
        node.entity.called = true;
      }

      while (Date.now() === this.updateCalled) { /* pass some time */ }
      super.update(); // not needed, but takes care of coverage :P
    }
  },
  component: class TestComponent extends Component {
    constructor(config) {

      super(config);

      this.called = false;
    }
  },
  node: class TestNode extends Node {},
  delta: 10
};

// adds a component to the node
internals.node.types = {
  test: internals.component
};

describe('Loading', () => {

  it('Should export the main class', () => {

    assert(typeof Serpentity === 'function');
  });

  it('Should export the Entity class', () => {

    assert(typeof Entity === 'function');
  });

  it('Should export the Component class', () => {

    assert(typeof Component === 'function');
  });

  it('Should export the System class', () => {

    assert(typeof System === 'function');
  });

  it('Should export the Node class', () => {

    assert(typeof Node === 'function');
  });
});

describe('Engine', () => {

  beforeEach(() => {

    internals.context.engine = new Serpentity();

    internals.context.regularSystem = new internals.system();
    internals.context.highPrioritySystem = new internals.system();
    internals.context.lowPrioritySystem = new internals.system();

    internals.context.firstEntity = new Entity();
    internals.context.firstEntity.addComponent(new internals.component());
    internals.context.secondEntity = new Entity();
    internals.context.secondEntity.addComponent(new internals.component());
    internals.context.emptyEntity = new Entity();

    // Add entity before the systems
    internals.context.engine.addEntity(internals.context.firstEntity);

    internals.context.engine.addSystem(internals.context.regularSystem, 100);
    internals.context.engine.addSystem(internals.context.highPrioritySystem, 0);
    internals.context.engine.addSystem(internals.context.lowPrioritySystem, 1000);

    // Add entity after the systems
    internals.context.engine.addEntity(internals.context.secondEntity);
    internals.context.engine.addEntity(internals.context.emptyEntity);
  });

  it('should call added callback on added systems', () => {

    // Ensure the added callback is being called
    assert(internals.context.regularSystem.addedCalled);
    assert(internals.context.highPrioritySystem.addedCalled);
    assert(internals.context.lowPrioritySystem.addedCalled);
  });

  it('should send the engine instance in added callback', () => {

    // Ensure the added callback is sending the engine
    assert(internals.context.regularSystem.addedEngine instanceof Serpentity);
    assert(internals.context.highPrioritySystem.addedEngine instanceof Serpentity);
    assert(internals.context.lowPrioritySystem.addedEngine instanceof Serpentity);
  });

  it('should not add duplicate systems', () => {

    const originalSystemsLength = internals.context.engine.systems.length;
    const added = internals.context.engine.addSystem(internals.context.regularSystem, 0);
    const newSystemsLength = internals.context.engine.systems.length;

    // Ensure we don't add the same system twice
    assert(!added);
    assert.deepEqual(newSystemsLength, originalSystemsLength);
  });

  it('should call update callback on added systems', () => {

    internals.context.engine.update(internals.delta);

    // Ensure update function called
    assert(!!internals.context.regularSystem.updateCalled);
    assert(!!internals.context.highPrioritySystem.updateCalled);
    assert(!!internals.context.lowPrioritySystem.updateCalled);
  });

  it('should keep proxied object behavior as expected', () => {

    internals.context.engine.update(internals.delta);

    assert(internals.context.highPrioritySystem.beforeCall === false);
    assert(internals.context.highPrioritySystem.afterCall === true);
  });

  it('should emit an event for every changed property', () => {

    internals.context.engine.update(internals.delta);

    assert(internals.context.regularSystem.emittedEvents[0].property === 'called');
    assert(internals.context.regularSystem.emittedEvents[0].from === false);
    assert(internals.context.regularSystem.emittedEvents[0].to === true);
    // 3 systems x 2 entities.
    assert(internals.context.regularSystem.emittedEvents.length === 6);
  });

  it('should call update callback in the order of priorities', () => {

    internals.context.engine.update(internals.delta);

    // Ensure order of priorities
    assert(internals.context.regularSystem.updateCalled < internals.context.lowPrioritySystem.updateCalled);
    assert(internals.context.regularSystem.updateCalled > internals.context.highPrioritySystem.updateCalled);
  });

  it('should send the delta in the update callback', () => {

    internals.context.engine.update(internals.delta);

    // Ensure delta is being sent
    assert.deepEqual(internals.context.regularSystem.updateDt, internals.delta);
    assert.deepEqual(internals.context.highPrioritySystem.updateDt, internals.delta);
    assert.deepEqual(internals.context.lowPrioritySystem.updateDt, internals.delta);
  });

  it('should no longer call removed systems', () => {

    const originalSystemLength = internals.context.engine.systems.length;
    const originalRemoved = internals.context.engine.removeSystem(internals.context.lowPrioritySystem);
    const intermediateSystemLength = internals.context.engine.systems.length;
    const finalRemoved = internals.context.engine.removeSystem(internals.context.lowPrioritySystem);
    const finalSystemLength = internals.context.engine.systems.length;
    internals.context.engine.update(internals.delta);

    // Check for return value
    assert(originalRemoved);
    assert(!finalRemoved);

    // Confirm that only removed if found by checking length of systems
    // array
    assert(originalSystemLength > intermediateSystemLength);
    assert.deepEqual(finalSystemLength, intermediateSystemLength);

    // Ensure callback is sent
    assert(!internals.context.regularSystem.removedCalled);
    assert(!internals.context.highPrioritySystem.removedCalled);
    assert(!!internals.context.lowPrioritySystem.removedCalled);

    // Ensure update is no longer sent
    assert(!!internals.context.regularSystem.updateCalled);
    assert(!!internals.context.highPrioritySystem.updateCalled);
    assert(!internals.context.lowPrioritySystem.updateCalled);
  });

  it('should only call nodes in selected node collections', () => {

    internals.context.engine.update(internals.delta);

    // Ensure component is called for each entity
    assert(!!internals.context.firstEntity._components[0].called);
    assert(!!internals.context.secondEntity._components[0].called);

    // Ensure entity not in node collection not called
    assert(!!internals.context.firstEntity.called);
    assert(!!internals.context.secondEntity.called);
    assert(!internals.context.emptyEntity.called);
  });

  it('should stop showing removed entities', () => {

    internals.context.engine.removeEntity(internals.context.secondEntity);
    internals.context.engine.update(internals.delta);

    assert(!!internals.context.firstEntity._components[0].called);
    assert(!internals.context.secondEntity._components[0].called);

    assert(!!internals.context.firstEntity.called);
    assert(!internals.context.secondEntity.called);
    assert(!internals.context.emptyEntity.called);
  });

  it('should not add duplicate components to entities', () => {

    const originalComponentsLength = internals.context.secondEntity._components.length;
    const result = internals.context.secondEntity.addComponent(new internals.component());
    const newComponentsLength = internals.context.secondEntity._components.length;

    assert(!result);
    assert.deepEqual(newComponentsLength, originalComponentsLength);
  });

  it('should allow access to components by class', () => {

    const firstComponent = internals.context.firstEntity.getComponent(internals.component);
    const emptyComponent = internals.context.emptyEntity.getComponent(internals.component);

    assert(firstComponent instanceof internals.component);
    assert.deepEqual(emptyComponent, undefined);
  });

  it('should not add duplicate entities', () => {

    const originalEntitiesLength = internals.context.engine.entities.length;
    const added = internals.context.engine.addEntity(internals.context.firstEntity);
    const finalEntitiesLength = internals.context.engine.entities.length;

    assert(!added);

    assert.deepEqual(finalEntitiesLength, originalEntitiesLength);
  });

  it('should remove entities', () => {

    const originalEntityLength = internals.context.engine.entities.length;
    const originalRemoved = internals.context.engine.removeEntity(internals.context.firstEntity);
    const intermediateEntityLength = internals.context.engine.entities.length;
    const finalRemoved = internals.context.engine.removeEntity(internals.context.firstEntity);
    const finalEntityLength = internals.context.engine.entities.length;
    internals.context.engine.update(internals.delta);

    // Check for return value
    assert(originalRemoved);
    assert(!finalRemoved);

    // Confirm that only removed if found by checking length of systems
    // array
    assert(originalEntityLength > intermediateEntityLength);
    assert.deepEqual(finalEntityLength, intermediateEntityLength);

    // Ensure callback is sent
    assert(!internals.context.firstEntity.called);
    assert(!!internals.context.secondEntity.called);
  });

  it('should not add duplicate entities', () => {

    const originalEntitiesLength = internals.context.engine.entities.length;
    const added = internals.context.engine.addEntity(internals.context.firstEntity);
    const finalEntitiesLength = internals.context.engine.entities.length;

    assert(!added);

    assert.deepEqual(finalEntitiesLength, originalEntitiesLength);
  });
});