/*
 * Copyright (c) 2021 ETH Zürich, Educational Development and Technology (LET)
 * 
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

using System;
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;
using SafeExamBrowser.Core.Contracts.OperationModel;
using SafeExamBrowser.Logging.Contracts;
using SafeExamBrowser.Core.OperationModel;

namespace SafeExamBrowser.Core.UnitTests.OperationModel
{
	[TestClass]
	public class RepeatableOperationSequenceTests
	{
		private Mock<ILogger> logger;

		[TestInitialize]
		public void Initialize()
		{
			logger = new Mock<ILogger>();
		}

		[TestMethod]
		public void MustCorrectlyAbortRepeat()
		{
			var operationA = new Mock<IRepeatableOperation>();
			var operationB = new Mock<IRepeatableOperation>();
			var operationC = new Mock<IRepeatableOperation>();
			var operations = new Queue<IRepeatableOperation>();

			operationA.Setup(o => o.Repeat()).Returns(OperationResult.Success);
			operationB.Setup(o => o.Repeat()).Returns(OperationResult.Aborted);

			operations.Enqueue(operationA.Object);
			operations.Enqueue(operationB.Object);
			operations.Enqueue(operationC.Object);

			var sut = new RepeatableOperationSequence(logger.Object, operations);
			var result = sut.TryRepeat();

			operationA.Verify(o => o.Repeat(), Times.Once);
			operationA.Verify(o => o.Revert(), Times.Never);
			operationB.Verify(o => o.Repeat(), Times.Once);
			operationB.Verify(o => o.Revert(), Times.Never);
			operationC.Verify(o => o.Repeat(), Times.Never);
			operationC.Verify(o => o.Revert(), Times.Never);

			Assert.AreEqual(OperationResult.Aborted, result);
		}

		[TestMethod]
		public void MustRepeatOperations()
		{
			var operationA = new Mock<IRepeatableOperation>();
			var operationB = new Mock<IRepeatableOperation>();
			var operationC = new Mock<IRepeatableOperation>();
			var operations = new Queue<IRepeatableOperation>();

			operationA.Setup(o => o.Repeat()).Returns(OperationResult.Success);
			operationB.Setup(o => o.Repeat()).Returns(OperationResult.Success);
			operationC.Setup(o => o.Repeat()).Returns(OperationResult.Success);

			operations.Enqueue(operationA.Object);
			operations.Enqueue(operationB.Object);
			operations.Enqueue(operationC.Object);

			var sut = new RepeatableOperationSequence(logger.Object, operations);
			var result = sut.TryRepeat();

			operationA.Verify(o => o.Perform(), Times.Never);
			operationA.Verify(o => o.Repeat(), Times.Once);
			operationA.Verify(o => o.Revert(), Times.Never);
			operationB.Verify(o => o.Perform(), Times.Never);
			operationB.Verify(o => o.Repeat(), Times.Once);
			operationB.Verify(o => o.Revert(), Times.Never);
			operationC.Verify(o => o.Perform(), Times.Never);
			operationC.Verify(o => o.Repeat(), Times.Once);
			operationC.Verify(o => o.Revert(), Times.Never);

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void MustRepeatOperationsInSequence()
		{
			int current = 0, a = 0, b = 0, c = 0;
			var operationA = new Mock<IRepeatableOperation>();
			var operationB = new Mock<IRepeatableOperation>();
			var operationC = new Mock<IRepeatableOperation>();
			var operations = new Queue<IRepeatableOperation>();

			operationA.Setup(o => o.Repeat()).Returns(OperationResult.Success).Callback(() => a = ++current);
			operationB.Setup(o => o.Repeat()).Returns(OperationResult.Success).Callback(() => b = ++current);
			operationC.Setup(o => o.Repeat()).Returns(OperationResult.Success).Callback(() => c = ++current);

			operations.Enqueue(operationA.Object);
			operations.Enqueue(operationB.Object);
			operations.Enqueue(operationC.Object);

			var sut = new RepeatableOperationSequence(logger.Object, operations);
			var result = sut.TryRepeat();

			Assert.AreEqual(OperationResult.Success, result);
			Assert.IsTrue(a == 1);
			Assert.IsTrue(b == 2);
			Assert.IsTrue(c == 3);
		}

		[TestMethod]
		public void MustNotRevertOperationsInCaseOfError()
		{
			var operationA = new Mock<IRepeatableOperation>();
			var operationB = new Mock<IRepeatableOperation>();
			var operationC = new Mock<IRepeatableOperation>();
			var operationD = new Mock<IRepeatableOperation>();
			var operations = new Queue<IRepeatableOperation>();

			operationA.Setup(o => o.Repeat()).Returns(OperationResult.Success);
			operationB.Setup(o => o.Repeat()).Returns(OperationResult.Success);
			operationC.Setup(o => o.Repeat()).Throws<Exception>();

			operations.Enqueue(operationA.Object);
			operations.Enqueue(operationB.Object);
			operations.Enqueue(operationC.Object);
			operations.Enqueue(operationD.Object);

			var sut = new RepeatableOperationSequence(logger.Object, operations);
			var result = sut.TryRepeat();

			operationA.Verify(o => o.Repeat(), Times.Once);
			operationA.Verify(o => o.Revert(), Times.Never);
			operationB.Verify(o => o.Repeat(), Times.Once);
			operationB.Verify(o => o.Revert(), Times.Never);
			operationC.Verify(o => o.Repeat(), Times.Once);
			operationC.Verify(o => o.Revert(), Times.Never);
			operationD.Verify(o => o.Repeat(), Times.Never);
			operationD.Verify(o => o.Revert(), Times.Never);

			Assert.AreEqual(OperationResult.Failed, result);
		}

		[TestMethod]
		public void MustSucceedRepeatingWithEmptyQueue()
		{
			var sut = new RepeatableOperationSequence(logger.Object, new Queue<IRepeatableOperation>());
			var result = sut.TryRepeat();

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void MustSucceedRepeatingWithoutCallingPerform()
		{
			var sut = new RepeatableOperationSequence(logger.Object, new Queue<IRepeatableOperation>());
			var result = sut.TryRepeat();

			Assert.AreEqual(OperationResult.Success, result);
		}

		[TestMethod]
		public void MustNotFailInCaseOfUnexpectedErrorWhenRepeating()
		{
			var sut = new RepeatableOperationSequence(logger.Object, new Queue<IRepeatableOperation>());

			sut.ProgressChanged += (args) => throw new Exception();

			var result = sut.TryRepeat();

			Assert.AreEqual(OperationResult.Failed, result);
		}
	}
}