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Commit 2e3389c

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added Bridge design pattern
1 parent 92c70bf commit 2e3389c

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package design_patterns
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/**
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*
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* Bridge is a structural design pattern used to separate abstraction and implementation
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*
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* so they can change independently
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*
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*/
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// OperatingSystem implements an internal algorithm for drawing primitives (operating systems are implementations in this example)
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abstract class OperatingSystem(private val name: String, private val version: Int) {
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protected val lines = mutableListOf<String>()
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protected val circles = mutableListOf<String>()
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abstract fun drawLine(startX: Int, startY: Int, endX: Int, endY: Int)
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abstract fun drawCircle(centerX: Int, centerY: Int, radius: Int)
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override fun toString(): String {
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return """
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$name $version
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Lines:
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${lines.joinToString("\n")}
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Circles:
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${circles.joinToString("\n")}
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""".trimIndent()
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}
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}
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// different implementations have different algorithms for drawing primitives
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class WindowsSystem : OperatingSystem("Windows", 10) {
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override fun drawLine(startX: Int, startY: Int, endX: Int, endY: Int) {
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lines.add("Windows graphic subsystem -> startX: $startX, startY: $startY, endX: $endX, endY: $endY")
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}
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override fun drawCircle(centerX: Int, centerY: Int, radius: Int) {
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circles.add("Windows graphic subsystem -> centerX: $centerX, centerY: $centerY, radius: $radius")
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}
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}
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class MacOSSystem : OperatingSystem("MacOS", 14) {
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override fun drawLine(startX: Int, startY: Int, endX: Int, endY: Int) {
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lines.add("MacOS graphic subsystem -> startX: $startX, startY: $startY, endX: $endX, endY: $endY")
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}
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override fun drawCircle(centerX: Int, centerY: Int, radius: Int) {
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circles.add("MacOS graphic subsystem -> centerX: $centerX, centerY: $centerY, radius: $radius")
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}
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}
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// we can add new primitives without changing OperatingSystem implementations (primitives are abstractions in this example)
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abstract class GraphicPrimitive {
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abstract fun draw(system: OperatingSystem)
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}
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class GraphicCirclePrimitive(
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private val centerX: Int,
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private val centerY: Int,
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private val radius: Int
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) : GraphicPrimitive() {
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override fun draw(system: OperatingSystem) {
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system.drawCircle(centerX, centerY, radius)
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}
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}
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class GraphicLinePrimitive(
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private val startX: Int,
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private val startY: Int,
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private val endX: Int,
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private val endY: Int
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) : GraphicPrimitive() {
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override fun draw(system: OperatingSystem) {
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system.drawLine(startX, startY, endX, endY)
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}
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}
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package design_patterns
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import org.junit.Test
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import org.junit.Assert.assertEquals
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class BridgeTest {
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@Test
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fun test() {
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val windowsSystem = WindowsSystem()
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val macOSSystem = MacOSSystem()
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// the line doesn't know how graphics are implemented in different operating systems
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val line = GraphicLinePrimitive(0, 0, 100, 100)
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line.draw(windowsSystem)
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line.draw(macOSSystem)
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// the circle doesn't know how graphics are implemented in different operating systems
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val circle = GraphicCirclePrimitive(10, 10, 6)
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circle.draw(windowsSystem)
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circle.draw(macOSSystem)
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assertEquals("""
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Windows 10
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Lines:
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Windows graphic subsystem -> startX: 0, startY: 0, endX: 100, endY: 100
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Circles:
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Windows graphic subsystem -> centerX: 10, centerY: 10, radius: 6
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""".trimIndent(), windowsSystem.toString())
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assertEquals("""
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MacOS 14
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Lines:
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MacOS graphic subsystem -> startX: 0, startY: 0, endX: 100, endY: 100
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Circles:
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MacOS graphic subsystem -> centerX: 10, centerY: 10, radius: 6
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""".trimIndent(), macOSSystem.toString())
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}
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}

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