todos/UnitTests/Tests/View Models/TaskListViewModelTests.swift

import Foundation
import SwiftData
import SwiftUI
import Testing

@testable import Todos

@Suite("TaskList view model tests")
struct TaskListViewModelTests {

    // MARK: Initializers tests

    @Test(
        "properties are set correctly during initialization",
        arguments: TodoGroup.allCases
    )
    func initialization(for group: TodoGroup) {
        // GIVEN
        // WHEN
        let viewModel = TaskListView.ViewModel(group: group)

        // THEN
        #expect(viewModel.group == group)
        #expect(viewModel.showCompleted == false)
    }

    // MARK: Computed property tests

    @Test(
        "buttonCompleted returns correct values when showCompleted is true",
        arguments: TodoGroup.allCases, [true, false]
    )
    func buttonCompleted(
        for group: TodoGroup,
        showCompleted: Bool
    ) {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: group)

        viewModel.showCompleted = showCompleted

        // WHEN
        let (title, icon) = viewModel.buttonCompleted

        // THEN
        if showCompleted {
            #expect(title == "view.task-list.label.hide-completed")
            #expect(icon == "eye.slash")
        }
        else {
            #expect(title == "view.task-list.label.show-completed")
            #expect(icon == "eye")
        }
    }

    @Test(
        "canShowCompleted returns correct value for each group",
        arguments: zip(
            TodoGroup.allCases,
            [true, true, true, false]
        )
    )
    func canShowCompleted(
        for group: TodoGroup,
        expects expectation: Bool
    ) {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: group)

        // WHEN
        let canShowCompleted = viewModel.canShowCompleted

        // THEN
        #expect(canShowCompleted == expectation)
    }

    @Test(
        "navigationTitle returns correct view title for each group",
        arguments: TodoGroup.allCases
    )
    func navigationTitle(for group: TodoGroup) {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: group)

        // WHEN
        let title = viewModel.navigationTitle

        // THEN
        #expect(title == group.title)
    }

    // MARK: Method tests

    @Test("deleteTasks removes a single task from model context")
    func deleteTasksSingle() throws {
        // GIVEN
        let container = try ModelContainer(
            for: Todo.self,
            configurations: .init(isStoredInMemoryOnly: true)
        )
        let context = ModelContext(container)

        let viewModel = TaskListView.ViewModel(group: .today)
        let todosToInsert: [Todo] = [
            .init(title: "Task 1", due: .now, order: 0),
            .init(title: "Task 2", due: .now, order: 1),
            .init(title: "Task 3", due: .now, order: 2),
        ]
        let countInitial = todosToInsert.count

        for todo in todosToInsert {
            context.insert(todo)
        }

        // WHEN
        viewModel.deleteTasks(
            todosToInsert,
            at: IndexSet(integer: 1),
            from: context
        )

        // THEN
        let descriptor = FetchDescriptor<Todo>()
        let todos = try context.fetch(descriptor)

        #expect(countInitial == 3)
        #expect(todos.count == 2)
        #expect(todos.contains(where: { $0.title == "Task 1" }))
        #expect(todos.contains(where: { $0.title == "Task 3" }))
        #expect(!todos.contains(where: { $0.title == "Task 2" }))
    }

    @Test("reorderTasks updates order property when moving task forward")
    func reorderTasksMovingForward() {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: .today)
        let tasks: [Todo] = [
            .init(title: "Task 1", due: .now, order: 0),
            .init(title: "Task 2", due: .now, order: 1),
            .init(title: "Task 3", due: .now, order: 2),
            .init(title: "Task 4", due: .now, order: 3),
        ]

        // WHEN
        viewModel.reorderTasks(
            tasks,
            from: IndexSet(integer: 0),
            to: 3
        )

        // THEN
        #expect(tasks[0].order == 2)
        #expect(tasks[1].order == 0)
        #expect(tasks[2].order == 1)
        #expect(tasks[3].order == 3)
    }

    @Test("reorderTasks updates order property when moving task backward")
    func reorderTasksMovingBackward() {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: .today)
        let tasks: [Todo] = [
            .init(title: "Task 1", due: .now, order: 0),
            .init(title: "Task 2", due: .now, order: 1),
            .init(title: "Task 3", due: .now, order: 2),
            .init(title: "Task 4", due: .now, order: 3),
        ]

        // WHEN
        viewModel.reorderTasks(
            tasks,
            from: IndexSet(integer: 3),
            to: 1
        )

        // THEN
        #expect(tasks[0].order == 0)
        #expect(tasks[1].order == 2)
        #expect(tasks[2].order == 3)
        #expect(tasks[3].order == 1)
    }

    @Test("toggleCompletedVisbility toggles the showCompleted property")
    func toggleCompletedVisibility() {
        // GIVEN
        let viewModel = TaskListView.ViewModel(group: .today)
        let initialValue = viewModel.showCompleted

        // WHEN
        viewModel.toggleCompletedVisibility()
        let afterFirstToggle = viewModel.showCompleted

        viewModel.toggleCompletedVisibility()
        let afterSecondToggle = viewModel.showCompleted

        // THEN
        #expect(initialValue == false)
        #expect(afterFirstToggle == true)
        #expect(afterSecondToggle == false)
    }

}