import 'dart:html' as html;
import 'package:rules_of_living/src/Simulation.dart';
import 'package:test/test.dart';
import 'package:mockito/mockito.dart';

@TestOn('browser')
import 'package:rules_of_living/src/Engine.dart';

class MockSimulation extends Mock implements Simulation {
  int updateNum = 0;
  bool hasChanges = false;

  @override
  Map<int, bool> update() {
    updateNum++;
    return hasChanges ? {1: true, 2: false} : {};
  }
}

void main() {
  Engine sut;
  setUp(() {
    sut = Engine();
  });
  group("process", () {
    setUp(() => sut.running = true);
    test("errors out if updating takes too long",
        () => expect(() => sut.process(5000, 10), throwsA(StackOverflowError)));
    test("does not update if not enough time elapsed to pass ms per step", () {
      bool result = false;
      sut.stepsPerSecond = 1000;

      sut.process(999, 2000,
          update: () => result = true, render: (double interp) => null);

      expect(result, true);
    });
    test("updates only when the ms per step threshold is crossed", () {
      int updateNum = 0;
      sut.stepsPerSecond = 1;

      sut.process(1001, 2000, update: () => updateNum++);
      expect(updateNum, equals(1));
    });
    test("updates until updateLag has been resolved", () {
      int updateNum = 0;
      sut.stepsPerSecond = 1;

      sut.process(2999, 5000, update: () => updateNum++);
      expect(updateNum, equals(2));
    });
    test("works without passing in update or render function arguments", () {
      sut.stepsPerSecond = 1000;
      expect(() => sut.process(500, 5000), isNot(throwsA(anything)));
    });
  });
  group("update", () {
    MockSimulation mockSim;
    setUp(() {
      mockSim = MockSimulation();
      sut.simulation = mockSim;
    });
    test("does not error out if no simulation variable is set", () {
      sut.simulation = null;
      expect(() => sut.update(), isNot(throwsA(anything)));
    });
    test("updates simulation one tick for every time it is called", () {
      sut.update();
      sut.update();
      sut.update();
      expect(mockSim.updateNum, equals(3));
    });
    test("sets running to false when simulation returns no changes", () {
      sut.running = true;
      sut.update();
      expect(sut.running, equals(false));
    });
    test("keeps running when simulation returns changes", () {
      sut.running = true;
      mockSim.hasChanges = true;

      sut.update();

      expect(sut.running, equals(true));
    });
  });
  group("step", () {
    MockSimulation mockSim;
    setUp(() {
      mockSim = MockSimulation();
      sut.simulation = mockSim;
    });
    test("advances the simulation by one update", () {
      sut.step();
      expect(mockSim.updateNum, equals(1));
    });
    test("turns off continuous engine updates", () {
      sut.running = true;
      sut.step();

      expect(sut.running, equals(false));
    });
  });
  group("canvas", () {
    test("Engine can be instantiated without canvas", () {
      expect(sut, isNot(throwsNoSuchMethodError));
    });

    test("Engine does not throw errors when calling render directly", () {
      // anonymous function necessary since throws can not use functions with args
      expect(() => sut.render, isNot(throwsNoSuchMethodError));
    });

    test("Engine does not throw errors when processing without attached canvas",
        () {
      // anonymous function necessary since throws can not use functions with args
      expect(() => sut.process, isNot(throwsNoSuchMethodError));
    });

    test("setCanvas allows setting a canvas for an engine at any point", () {
      sut.canvas = new html.CanvasElement();
      expect(sut.canvas, isNotNull);
    });
  });
}