//
//  QuizAppUnitTests.swift
//  QuizAppUnitTests
//
//  Created by Paul on 08.09.25.
//

import XCTest

@testable import QuizApp

final class QuizAppUnitTests: XCTestCase {

    private func makeMC(
        question: String,
        answers: [String] = ["A", "B", "C"],
        correct: Int
    ) -> QuizQuestion {
        struct Payload: Encodable {
            let question: String
            let answers: [String]
            let correctAnswer: Int
        }
        let payload = Payload(
            question: question,
            answers: answers,
            correctAnswer: correct
        )
        let data = try! JSONEncoder().encode(payload)
        return try! JSONDecoder().decode(QuizQuestion.self, from: data)
    }

    private func makeEst(
        question: String,
        correct: Double,
        min: Double = 0,
        max: Double = 100,
        unit: String = ""
    ) -> QuizQuestion {
        struct Payload: Encodable {
            let type = "estimation"
            let question: String
            let minValue: Double
            let maxValue: Double
            let correctValue: Double
            let unit: String
        }
        let payload = Payload(
            question: question,
            minValue: min,
            maxValue: max,
            correctValue: correct,
            unit: unit
        )
        let data = try! JSONEncoder().encode(payload)
        return try! JSONDecoder().decode(QuizQuestion.self, from: data)
    }

    func testIncrementScore_CorrectAnswer() {
        let vm = QuizViewModel()
        vm.questions = [makeMC(question: "Q1", correct: 2)]
        vm.currentQuestionIndex = 0
        XCTAssertEqual(vm.score, 0)
        vm.incrementScore(selectedIndex: 2)
        XCTAssertEqual(vm.score, 1)
    }

    func testIncrementScore_WrongAnswer() {
        let vm = QuizViewModel()
        vm.questions = [makeMC(question: "Q1", correct: 2)]
        vm.currentQuestionIndex = 0
        vm.incrementScore(selectedIndex: 1)
        XCTAssertEqual(vm.score, 0)
    }

    func testLoadNextQuestion_NotFinished() {
        let vm = QuizViewModel()
        vm.questions = [
            makeMC(question: "Q1", correct: 0),
            makeMC(question: "Q2", correct: 0),
        ]
        vm.currentQuestionIndex = 0
        vm.loadNextQuestion()
        XCTAssertFalse(vm.isQuizFinished)
    }

    func testLoadNextQuestion_Finished() {
        let vm = QuizViewModel()
        vm.questions = [makeMC(question: "Q1", correct: 0)]
        vm.currentQuestionIndex = 0
        vm.loadNextQuestion()
        XCTAssertTrue(vm.isQuizFinished)
    }

    func testPointsForEstimation_onePoint() {
        let vm = QuizViewModel()
        let p = vm.pointsForEstimation(guess: 109, correct: 100, maxPoints: 1)
        XCTAssertEqual(p, 1)
    }

    func testPointsForEstimation_ZeroPoints() {
        let vm = QuizViewModel()
        let p = vm.pointsForEstimation(guess: 111, correct: 100, maxPoints: 1)
        XCTAssertEqual(p, 0)
    }

}