Task 1,2,3.

.github/workflows/check.yml

@@ -0,0 +1,32 @@
+name: Check
+
+on:
+  pull_request:
+    types: [assigned, opened, synchronize, reopened]
+
+jobs:
+  checks:
+    name: Checks
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - name: set up JDK 17
+      uses: actions/setup-java@v1
+      with:
+        java-version: 17
+    - name: Cache
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.gradle/caches
+          ~/.gradle/wrapper
+          ~/.m2
+          ~/.android/build-cache
+        key: ${GITHUB_REF##*/}
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Check with gradle
+      run: ./gradlew build

README.md

@@ -1,2 +1,33 @@
 # Kotlin-7 - Generics
 Код к занятию Kotlin-7 - Generics
+
+## Домашнее задание
+В папке [network](src/main/kotlin/ru/kotlin/homework/network) находится прототип класса
+результата работы сетевого сервиса `NetworkResponse`, который может быть:
+
+- `Success` - для удачного результата
+- `Failure` - для ошибки
+
+### Задание 1.
+Исправьте определение классов так, чтобы все присваивания под определениями компилировались
+без ошибок. Подсказки:
+
+- Используйте declaration type variance
+- Мы только ВОЗВРАЩАЕМ результат или ошибку (ковариантность по обоим параметрам)
+- Вспоминаем, что тип Nothing - это подтип любого другого типа
+
+### Задание 2.
+Почините (правильно расставьте variance параметров) класс [NetworkLogger](src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt)
+таким образом, чтобы **один** универсальный экземпляр логгера можно было использовать для логирования любых ошибок:
+
+- `processThrowables` принимает `ErrorLogger<Throwable>`
+- `processApiErrors` принимает `ErrorLogger<ApiException>`
+
+Приступайте ко второму заданию только после окончания работы над первым!
+
+### Задание 3 (со звездочкой)
+Сделайте так, чтобы [NetworkLogger](src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt) имел возможность выдать список
+накопленных ошибок. Настройте типы таким образом, чтобы при сохранении условий заданий 1 и 2, в классе появилась функция:
+```kotlin
+fun dump(): List<Pair<LocalDateTime, E>>
+```

settings.gradle

@@ -1,2 +1 @@
 rootProject.name = 'Kotlin7'
-

src/main/kotlin/ru/kotlin/homework/Colors.kt

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+package ru.kotlin.homework
+
+abstract class Color
+
+data object Red : Color()
+data object Blue : Color()
+data object Green : Color()

src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt

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+@file:Suppress("unused")
+
+package ru.kotlin.homework
+
+import java.lang.IllegalArgumentException
+
+open class ShapeToColor {
+    open fun process(shape: Shape): Color = when(shape) {
+        is Square -> Red
+        is Circle -> Blue
+        else -> throw IllegalArgumentException("Unknown shape")
+    }
+}
+
+class CircleToColor : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Circle -> Blue
+        else -> throw IllegalArgumentException("Unknown shape")
+    }
+}
+
+class NewShapeToColor : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Triangle -> Blue
+        else -> super.process(shape)
+    }
+}
+
+class NewColors : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Triangle -> Blue
+        is Square -> Green
+        else -> super.process(shape)
+    }
+}
+
+class AllInRed : ShapeToColor() {
+    override fun process(shape: Shape): Color = Red
+}

src/main/kotlin/ru/kotlin/homework/Shapes.kt

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+package ru.kotlin.homework
+
+import kotlin.random.Random
+
+abstract class Shape {
+    val id: Int = Random.nextInt()
+}
+
+data object Square: Shape()
+data object Circle: Shape()
+data object Triangle: Shape()

src/main/kotlin/ru/kotlin/homework/coVarianceInKotlin.kt

@@ -0,0 +1,19 @@
+package ru.kotlin.homework
+
+
+fun main() {
+    val producer: ShapeProducer = CircleProducer()
+    println(producer.produce())
+}
+
+open class ShapeProducer {
+    open fun produce(): Shape {
+        return Square
+    }
+}
+
+class CircleProducer : ShapeProducer() {
+    override fun produce(): Circle {
+        return Circle
+    }
+}

src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt

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+package ru.kotlin.homework
+
+fun main() {
+    val processor: ToExtendCircle = ToExtendShape()
+    processor.process(Circle)
+
+    val shapeProcessor: ToExtendShape = processor as ToExtendShape
+    shapeProcessor.process(Square)
+}
+
+open class ToExtendCircle {
+    open fun process(value: Circle) {
+        println(value)
+    }
+}
+
+class ToExtendShape : ToExtendCircle() {
+    fun process(value: Shape) = when(value) {
+        is Circle -> super.process(value)
+        else -> println("Any: $value")
+    }
+}

src/main/kotlin/ru/kotlin/homework/generics.kt

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+@file:Suppress("RedundantExplicitType")
+
+package ru.kotlin.homework
+
+import java.lang.IllegalArgumentException
+
+private val matcher: ShapeToColor = AllInRed()
+
+fun main() {
+    println("Square: ${process(Square)}")
+    println("Circle: ${process(Circle)}")
+}
+
+fun process(shape: Shape) = when(matcher.process(shape)) {
+    Red -> "Красный"
+    Blue -> "Голубой"
+    else -> throw IllegalArgumentException("Неизвестный цвет")
+}

src/main/kotlin/ru/kotlin/homework/inOut.kt

@@ -0,0 +1,61 @@
+package ru.kotlin.homework
+
+
+fun main() {
+    val circleGroup = Group<Circle>()
+    circleGroup.insert(Circle)
+    val fromGroup = circleGroup.fetch()
+    println("From group: $fromGroup")
+
+    val readGroup: Group<out Shape> = circleGroup
+    val fromReadGroup: Shape = readGroup.fetch()
+    println("From read group: $fromReadGroup")
+    fetcher(circleGroup)
+
+    val shapeGroup = Group<Shape>()
+    val writeCircleGroup: Group<in Circle> = shapeGroup
+    writeCircleGroup.insert(Circle)
+    val writeTriangleGroup: Group<in Triangle> = shapeGroup
+    writeTriangleGroup.insert(Triangle)
+    putter(shapeGroup, Circle)
+
+    val fromShapeGroup: Shape = shapeGroup.fetch()
+    println("From shape group: $fromShapeGroup")
+
+    var anyGroup: Group<*> = circleGroup
+    println(measure(anyGroup))
+    anyGroup = readGroup
+    println(measure(anyGroup))
+    anyGroup = shapeGroup
+    println(measure(anyGroup))
+
+    idOfFetched(anyGroup)
+}
+
+open class Group<T : Shape> {
+    private val items: MutableList<T> = mutableListOf()
+
+    fun getSize(): Int = items.size
+
+    fun insert(item: T) {
+        items.add(item)
+    }
+    fun fetch(): T {
+        return items.last()
+    }
+}
+
+fun fetcher(group: Group<out Shape>) {
+    val fetched = group.fetch()
+    println(fetched)
+}
+fun putter(group: Group<in Circle>, item: Circle) {
+    group.insert(item)
+}
+fun measure(group: Group<*>) {
+    println("Size of group: ${group.getSize()}")
+}
+fun idOfFetched(group: Group<*>) {
+    val fetched: Shape = group.fetch()
+    println("Id of fetched: ${fetched.id}")
+}

src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt

@@ -0,0 +1,68 @@
+@file:Suppress("unused")
+
+package ru.kotlin.homework.network
+
+import ru.kotlin.homework.Circle
+import java.lang.IllegalArgumentException
+import java.time.LocalDateTime
+
+/**
+ * Известный вам список ошибок
+ */
+sealed class ApiException(message: String) : Throwable(message) {
+    data object NotAuthorized : ApiException("Not authorized")
+    data object NetworkException : ApiException("Not connected")
+    data object UnknownException: ApiException("Unknown exception")
+}
+
+class ErrorLogger<E: Throwable> {
+
+    private val errors = mutableListOf<Pair<LocalDateTime, E>>()
+
+    fun log(response: NetworkResponse<*, out E>) {
+        if (response is Failure) {
+            errors.add(response.responseDateTime to response.error)
+        }
+    }
+
+    fun dumpLog() {
+        errors.forEach { (date, error) ->
+            println("Error at $date: ${error.message}")
+        }
+    }
+
+    fun dump(): List<Pair<LocalDateTime, E>> {
+        return errors.toList()
+    }
+}
+
+fun processThrowables(logger: ErrorLogger<in Throwable>) {
+    logger.log(Success("Success"))
+    Thread.sleep(100)
+    logger.log(Success(Circle))
+    Thread.sleep(100)
+    logger.log(Failure(IllegalArgumentException("Something unexpected")))
+
+    logger.dumpLog()
+}
+
+fun processApiErrors(apiExceptionLogger: ErrorLogger<in ApiException>) {
+    apiExceptionLogger.log(Success("Success"))
+    Thread.sleep(100)
+    apiExceptionLogger.log(Success(Circle))
+    Thread.sleep(100)
+    apiExceptionLogger.log(Failure(ApiException.NetworkException))
+
+    apiExceptionLogger.dumpLog()
+}
+
+fun main() {
+    val logger = ErrorLogger<Throwable>()
+
+    println("Processing Throwable:")
+    processThrowables(logger)
+
+    println("Processing Api:")
+    processApiErrors(logger)
+}
+

src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt

@@ -0,0 +1,45 @@
+@file:Suppress("unused")
+
+package ru.kotlin.homework.network
+
+import java.lang.Exception
+import java.lang.IllegalArgumentException
+import java.time.LocalDateTime
+
+/**
+ * Network result
+ */
+sealed class NetworkResponse<out T, out R> {
+    val responseDateTime: LocalDateTime = LocalDateTime.now()
+}
+
+/**
+ * Network success
+ */
+data class Success<out T>(val resp: T): NetworkResponse<T, Nothing>()
+
+/**
+ * Network error
+ */
+data class Failure<out R>(val error: R): NetworkResponse<Nothing, R>()
+
+val s1 = Success("Message")
+val r11: NetworkResponse<String, Error> = s1
+val r12: NetworkResponse<Any, Error> = s1
+
+val s2 = Success("Message")
+val r21: NetworkResponse<String, Exception> = s2
+val r22: NetworkResponse<Any, Exception> = s2
+
+val s3 = Success(String())
+val r31: Success<CharSequence> = s3
+val r32: Success<Any> = s3
+
+val e = Failure(Error())
+val er1: NetworkResponse<String, Error> = e
+val er2: NetworkResponse<Any, Error> = e
+val er4: NetworkResponse<Any, Throwable> = e
+
+val er5: NetworkResponse<Int, Throwable> = Failure(IllegalArgumentException("message"))
+
+val message = e.error.message