/*

 Copyright (C) 2018 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Unit tests for the CalculatorKit framework.

 */

import XCTest

@testable import CalculatorKit

class CalculatorKitTests: XCTestCase {

    // MARK: - Properties

    var calculator: Calculator?

    // MARK: - Setup and Teardown

    override func setUp() {

        super.setUp()

        // Put setup code here. This method is called before the invocation of each test method in the class.

        calculator = Calculator()

        XCTAssertNotNil(calculator, "Cannot create Calculator instance.")

    }

    override func tearDown() {

        // Put teardown code here. This method is called after the invocation of each test method in the class.

        super.tearDown()

    }

    // MARK: - Addition

    /// Performs a simple addition test: 6 + 2 = 8.

    func testAddition() {

        if let calculator = calculator {

            try? calculator.input("6")

            try? calculator.input("+")

            try? calculator.input("2")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "8")

        }

    }

    // MARK: - Subtraction

    /// Performs a simple subtraction test: 19 - 2 = 17.

    func testSubtraction() {

        if let calculator = calculator {

            try? calculator.input("1")

            try? calculator.input("9")

            try? calculator.input("-")

            try? calculator.input("2")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "17")

        }

    }

    // MARK: - Division

    /// Performs a simple division test: 19 / 8 = 2.375.

    func testDivision() {

        if let calculator = calculator {

            try? calculator.input("1")

            try? calculator.input("9")

            try? calculator.input("/")

            try? calculator.input("8")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "2.375")

        }

    }

    // MARK: - Multiplication

    /// Performs a simple multiplication test: 6 * 2 = 12.

    func testMultiplication() {

        if let calculator = calculator {

            try? calculator.input("6")

            try? calculator.input("*")

            try? calculator.input("2")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "12")

        }

    }

    // MARK: - Subtraction Negative Result

    /// Performs a simple subtraction test with a negative result: 6 - 24 = -18.

    func testSubtractionNegativeResult() {

        if let calculator = calculator {

            try? calculator.input("6")

            try? calculator.input("-")

            try? calculator.input("2")

            try? calculator.input("4")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "-18")

        }

    }

    // MARK: - Clear Last Entry

    /// Tests that the clear (C) key clears the last entry when used once.

    func testClearLastEntry() {

        if let calculator = calculator {

            try? calculator.input("7")

            try? calculator.input("+")

            try? calculator.input("3")

            try? calculator.input("C")

            try? calculator.input("4")

            try? calculator.input("=")

            XCTAssertTrue(calculator.displayValue == "11")

        }

    }

    // MARK: - Clear Computation

    /// Tests that the clear (C) key clears the computation when used twice.

    func testClearComputation() {

        if let calculator = calculator {

            try? calculator.input("C")

            try? calculator.input("7")

            try? calculator.input("+")

            try? calculator.input("3")

            try? calculator.input("C")

            try? calculator.input("C")

            XCTAssertTrue(calculator.displayValue == "0")

        }

    }

    // MARK: - Input Exception

    /**

        Tests that the input: method throws an exception in three situations:

        1. The argument contains more than one character.

        2. The argument contains an invalid character.

        3. The argument is nil.

    */

    func testInputException() {

        if let calculator = calculator {

            XCTAssertThrowsError(try calculator.input("67")) { error in

                print(error.localizedDescription)

            }

            XCTAssertThrowsError(try calculator.input("j")) { error in

                print(error.localizedDescription)

            }

            XCTAssertThrowsError(try calculator.input(nil)) { error in

                print(error.localizedDescription)

            }

        }

    }

}