io-to-data.21 : Extension function all the things

Duncan McGregor · dmcg · commit 6a736a44e5a8 · 2021-06-23T22:24:16.000+01:00
diff --git a/src/main/java/travelator/marketing/HighValueCustomersMain.kt b/src/main/java/travelator/marketing/HighValueCustomersMain.kt
@@ -1,19 +1,25 @@
 package travelator.marketing
 
+import java.io.Reader
 import java.io.Writer
 
 fun main() {
     System.`in`.reader().use { reader ->
         System.out.writer().use { writer ->
-            writer.appendLines(
-                generate(
-                    reader.buffered().lineSequence()
-                )
-            )
+            reader
+                .asLineSequence()
+                .toHighValueCustomerReport()
+                .writeTo(writer)
         }
     }
 }
 
+fun Reader.asLineSequence() = buffered().lineSequence()
+
+fun Sequence<CharSequence>.writeTo(writer: Writer) {
+    writer.appendLines(this)
+}
+
 fun Writer.appendLines(lines: Sequence<CharSequence>): Writer {
     return this.also {
         lines.forEach(this::appendLine)
diff --git a/src/main/java/travelator/marketing/HighValueCustomersReport.kt b/src/main/java/travelator/marketing/HighValueCustomersReport.kt
@@ -1,7 +1,7 @@
 package travelator.marketing
 
-fun generate(lines: Sequence<String>): Sequence<String> {
-    val valuableCustomers = lines
+fun Sequence<String>.toHighValueCustomerReport(): Sequence<String> {
+    val valuableCustomers = this
         .withoutHeader()
         .map(String::toCustomerData)
         .filter { it.score >= 10 }
diff --git a/src/test/java/travelator/marketing/HighValueCustomersReportTests.kt b/src/test/java/travelator/marketing/HighValueCustomersReportTests.kt
@@ -50,11 +50,10 @@ class HighValueCustomersReportTests {
         inputLines: List<String>,
         expectedLines: List<String>
     ) {
+        val lines = inputLines.asSequence().constrainOnce()
         assertEquals(
             expectedLines,
-            generate(
-                inputLines.asSequence().constrainOnce()
-            ).toList()
+            lines.toHighValueCustomerReport().toList()
         )
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -50,11 +50,10 @@ class HighValueCustomersReportTests {`
`50`	`50`	`inputLines: List<String>,`
`51`	`51`	`expectedLines: List<String>`
`52`	`52`	`) {`
	`53`	`+ val lines = inputLines.asSequence().constrainOnce()`
`53`	`54`	`assertEquals(`
`54`	`55`	`expectedLines,`
`55`		`- generate(`
`56`		`- inputLines.asSequence().constrainOnce()`
`57`		`- ).toList()`
	`56`	`+ lines.toHighValueCustomerReport().toList()`
`58`	`57`	`)`
`59`	`58`	`}`
`60`	`59`	`}`