//
//  FetcherTests.swift
//  PersistenceTests
//
//  Created by Javier Cicchelli on 17/04/2023.
//  Copyright © 2023 Röck+Cöde. All rights reserved.
//

import Persistence
import XCTest

final class FetcherTests: XCTestCase {

    // MARK: Properties
    
    private let persistence = TestPersistenceService.shared
    
    private var fetcher: Fetcher<TestEntity>!
    
    // MARK: Setup
    
    override func setUpWithError() throws {
        fetcher = .init(
            fetchRequest: .allTestEntities(),
            managedObjectContext: persistence.viewContext
        )
    }
    
    override func tearDownWithError() throws {
        fetcher = nil
    }
    
    // MARK: Number of sections tests
    
    func test_numberOfSections_whenModelIsEmpty() throws {
        // GIVEN
        try fetcher.fetch()
        
        // WHEN
        let numberOfSections = fetcher.numberOfSections
        
        // THEN
        XCTAssertEqual(numberOfSections, 1)
    }
    
    func test_numberOfSections_whenModelIsFilled() throws {
        // GIVEN
        let context = persistence.makeChildContext()
        let _ = [
            TestEntity(context: context),
            TestEntity(context: context),
            TestEntity(context: context)
        ]
        
        try persistence.save(childContext: context)
        try fetcher.fetch()
        
        // WHEN
        let numberOfSections = fetcher.numberOfSections
        
        // THEN
        XCTAssertEqual(numberOfSections, 1)
    }
    
    func test_numberOfSections_whenNoFetch() async throws {
        // GIVEN
        // WHEN
        let numberOfSections = fetcher.numberOfSections
        
        // THEN
        XCTAssertEqual(numberOfSections, 0)
    }
    
    // MARK: Number of objects tests
    
    func test_numberOfObjects_inFirstSection_whenModelIsEmpty() throws {
        // GIVEN
        try fetcher.fetch()

        // WHEN
        let section = fetcher.numberOfSections - 1
        let numberOfObjects = try fetcher.numberOfObjects(in: section)
        
        // THEN
        XCTAssertEqual(numberOfObjects, 0)
    }
    
    func test_numberOfObjects_inFirstSection_whenModelIsFilled() throws {
        // GIVEN
        let context = persistence.makeChildContext()
        let entities = [
            TestEntity(context: context),
            TestEntity(context: context),
            TestEntity(context: context)
        ]
        
        try persistence.save(childContext: context)
        try fetcher.fetch()

        // WHEN
        let section = fetcher.numberOfSections - 1
        let numberOfObjects = try fetcher.numberOfObjects(in: section)
        
        // THEN
        XCTAssertEqual(numberOfObjects, entities.count)
    }
    
    func test_numberOfObjects_inNonExistingSection() throws {
        // GIVEN
        try fetcher.fetch()

        // WHEN & THEN
        let section = fetcher.numberOfSections
        
        XCTAssertThrowsError(try fetcher.numberOfObjects(in: section)) { error in
            XCTAssertEqual(error as? FetcherError, .sectionNotFound)
        }
    }
    
    func test_numberOfObjects_whenNoFetch() throws {
        // GIVEN
        // WHEN & THEN
        XCTAssertThrowsError(try fetcher.numberOfObjects(in: 1)) { error in
            XCTAssertEqual(error as? FetcherError, .fetchNotExecuted)
        }
    }
    
    // MARK: Object at tests
    
    func test_objectAt_whenModelIsEmpty() throws {
        // GIVEN
        try fetcher.fetch()

        // WHEN & THEN
        let indexPath = IndexPath(
            item: 0,
            section: fetcher.numberOfSections - 1
        )
        
        // TODO: Need to find out how to handle NSInvalidArgumentException in this test.
        // let object = try fetcher.object(at: indexPath)
    }
    
    func test_objectAt_whenModelIsFilled() throws {
        // GIVEN
        let context = persistence.makeChildContext()
        let entities = [TestEntity(context: context)]
        
        try persistence.save(childContext: context)
        try fetcher.fetch()

        // WHEN & THEN
        let indexPath = IndexPath(
            item: entities.count - 1,
            section: fetcher.numberOfSections - 1
        )
        
        let object = try fetcher.object(at: indexPath)
        
        XCTAssertNotNil(object)
    }
    
    func test_objectAt_withOutOfBoundsIndexPath() throws {
        // GIVEN
        let context = persistence.makeChildContext()
        let entities = [TestEntity(context: context)]
        
        try persistence.save(childContext: context)
        try fetcher.fetch()

        // WHEN & THEN
        let indexPath = IndexPath(
            item: entities.count,
            section: fetcher.numberOfSections
        )

        // TODO: Need to find out how to handle NSInvalidArgumentException in this test.
        // let object = try fetcher.object(at: indexPath)
    }

    func test_objectAt_whenNoFetch() throws {
        // GIVEN
        // WHEN & THEN
        let indexPath = IndexPath(
            item: 0,
            section: 0
        )
        
        XCTAssertThrowsError(try fetcher.object(at: indexPath)) { error in
            XCTAssertEqual(error as? FetcherError, .fetchNotExecuted)
        }
    }
    
}