added pattern Chain Of Responsibilities

README.md

@@ -33,9 +33,10 @@ Content:
     * [Singleton](/src/main/kotlin/design_patterns/Singleton.kt)
     * [Strategy](/src/main/kotlin/design_patterns/Strategy.kt)
     * [Observer](/src/main/kotlin/design_patterns/Observer.kt)
-    * [Dependency Injection](/src/main/kotlin/design_patterns/Dependency%20%20Injection.kt)
+    * [Dependency Injection](/src/main/kotlin/design_patterns/Dependency%20Injection.kt)
     * [Adapter](/src/main/kotlin/design_patterns/Adapter.kt)
     * [Memento](/src/main/kotlin/design_patterns/Memento.kt)
+    * [Chain Of Responsibilities](/src/main/kotlin/design_patterns/Chain%20Of%20Responsibilities.kt)
 
 2. package <code>structures</code> - data structure
     * [Binary tree](/src/main/kotlin/structures/BinaryTree.kt)

README_ru.md

@@ -31,9 +31,10 @@
     * [Singleton](/src/main/kotlin/design_patterns/Singleton.kt)
     * [Strategy](/src/main/kotlin/design_patterns/Strategy.kt)
     * [Observer](/src/main/kotlin/design_patterns/Observer.kt)
-    * [Dependency Injection](/src/main/kotlin/design_patterns/Dependency%20%20Injection.kt)
+    * [Dependency Injection](/src/main/kotlin/design_patterns/Dependency%20Injection.kt)
     * [Adapter](/src/main/kotlin/design_patterns/Adapter.kt)
     * [Memento](/src/main/kotlin/design_patterns/Memento.kt)
+    * [Chain Of Responsibilities](/src/main/kotlin/design_patterns/Chain%20Of%20Responsibilities.kt)
 
 2. пакет <code>ru.structures</code> - структуры данных
     * [Бинарное дерево](/src/main/kotlin/structures/BinaryTree.kt)

src/main/kotlin/design_patterns/Visitor.kt

@@ -1,6 +1,7 @@
 package design_patterns
 
 /**
+ *
  * pattern: Visitor
  *
  * description: it's a behavioral pattern that allows you to add a new operation

src/main/kotlin/design_patterns/Сhain Of Responsibilities.kt

@@ -0,0 +1,68 @@
+package design_patterns
+
+/**
+ *
+ * pattern: Chain of responsibility
+ *
+ * description: a design pattern consisting of “a source of command objects and a series of processing objects”.
+ * Each processing object in the chain is responsible for a certain type of command, and the processing is done,
+ * it forwards the command to the next processor in the chain.
+ *
+ */
+
+enum class BlockFactor {
+    ONE, TWO, THREE
+}
+
+/**
+ *
+ * I decided to give an analogy from the Minecraft game.
+ * In this game there are blocks that can be broken with a stone pickaxe, iron and diamond.
+ * For example: diamond may mine by iron and diamond pickaxes unlike cobblestone, which is mined by any
+ *
+ */
+abstract class Block(private val factor: BlockFactor) {
+    fun mayMine(factor: BlockFactor) = this.factor.ordinal <= factor.ordinal
+}
+
+/**
+ *
+ * blocks from the game
+ *
+ */
+class StoneBlock: Block(BlockFactor.ONE)
+class DiamondBlock: Block(BlockFactor.TWO)
+class ObsidianBlock: Block(BlockFactor.THREE)
+
+abstract class Pickaxe(private val factor: BlockFactor) {
+
+    private var nextPickaxe: Pickaxe? = null
+    fun changeNextPickaxe(pickaxe: Pickaxe) {
+        this.nextPickaxe = pickaxe
+    }
+
+    /**
+     *
+     * we mine the block, if it doesn't work, we take another pickaxe, if there is one
+     *
+     * @return return true if a pickaxe can mine
+     */
+    fun mine(block: Block): Boolean =
+        if (block.mayMine(factor)) {
+            true
+        } else {
+            nextPickaxe?.mine(block) ?: false
+        }
+
+}
+
+/**
+ *
+ * pickaxes from the game
+ *
+ */
+class StonePickaxe: Pickaxe(BlockFactor.ONE)
+
+class IronPickaxe: Pickaxe(BlockFactor.TWO)
+
+class DiamondPickaxe: Pickaxe(BlockFactor.THREE)

src/test/kotlin/design_patterns/ChainOfResponsibilitiesTest.kt

@@ -0,0 +1,41 @@
+package design_patterns
+
+import org.junit.Test
+import org.junit.jupiter.api.Assertions
+
+class ChainOfResponsibilitiesTest {
+
+    @Test
+    fun test_when_we_have_only_stone_pickaxe() {
+        val pickaxe = StonePickaxe()
+
+        Assertions.assertEquals(true, pickaxe.mine(StoneBlock()))
+        Assertions.assertEquals(false, pickaxe.mine(DiamondBlock()))
+        Assertions.assertEquals(false, pickaxe.mine(ObsidianBlock()))
+    }
+
+    @Test
+    fun test_when_we_have_stone_and_iron_pickaxes() {
+        val pickaxe = StonePickaxe()
+        pickaxe.changeNextPickaxe(IronPickaxe())
+
+        Assertions.assertEquals(true, pickaxe.mine(StoneBlock()))
+        Assertions.assertEquals(true, pickaxe.mine(DiamondBlock()))
+        Assertions.assertEquals(false, pickaxe.mine(ObsidianBlock()))
+    }
+
+    @Test
+    fun test_when_we_have_all_three_pickaxes() {
+        val pickaxe = StonePickaxe()
+        val ironPickaxe = IronPickaxe().apply {
+            changeNextPickaxe(DiamondPickaxe())
+        }
+        pickaxe.changeNextPickaxe(ironPickaxe)
+
+        Assertions.assertEquals(true, pickaxe.mine(StoneBlock()))
+        Assertions.assertEquals(true, pickaxe.mine(DiamondBlock()))
+        Assertions.assertEquals(true, pickaxe.mine(ObsidianBlock()))
+    }
+
+
+}