Added main method for command line usage

lib/src/main/kotlin/net/thauvin/erik/urlencoder/UrlEncoder.kt

@@ -19,15 +19,22 @@ package net.thauvin.erik.urlencoder
 
 import java.nio.charset.StandardCharsets
 import java.util.BitSet
+import kotlin.system.exitProcess
 
 /**
  * URL parameters encoding and decoding.
  *
+ * - Rules determined by [RFC 3986](https://www.rfc-editor.org/rfc/rfc3986#page-13),
+ *
  * @author Geert Bevin (gbevin[remove] at uwyn dot com)
  * @author Erik C. Thauvin (erik@thauvin.net)
  */
 object UrlEncoder {
     private val hexDigits = "0123456789ABCDEF".toCharArray()
+    internal val usage = """Usage : kotlin -cp urlencoder-*.jar ${UrlEncoder::class.java.name} [-ed] text
+Encode and decode URL parameters.
+  -e  encode (default)
+  -d  decode"""
 
     // see https://www.rfc-editor.org/rfc/rfc3986#page-13
     private val unreservedChars = BitSet('~'.code + 1).apply {
@@ -103,7 +110,7 @@ object UrlEncoder {
                 }
             } else {
                 if (bytesBuffer != null) {
-                    out?.append(String(bytesBuffer, 0, bytesPos, StandardCharsets.UTF_8))
+                    out!!.append(String(bytesBuffer, 0, bytesPos, StandardCharsets.UTF_8))
                     bytesBuffer = null
                     bytesPos = 0
                 }
@@ -121,7 +128,9 @@ object UrlEncoder {
 
     /**
      * Transforms a provided [String] object into a new string, containing only valid URL characters in the UTF-8
-     * encoding. Letters, numbers, unreserved (`_-!.~'()*`) and allowed characters are left intact.
+     * encoding.
+     *
+     * - Letters, numbers, unreserved (`_-!.~'()*`) and allowed characters are left intact.
      */
     @JvmStatic
     fun encode(source: String, allow: String): String {
@@ -167,10 +176,50 @@ object UrlEncoder {
 
     /**
      * Transforms a provided [String] object into a new string, containing only valid URL characters in the UTF-8
-     * encoding. Letters, numbers, unreserved (`_-!.~'()*`) and allowed characters are left intact.
+     * encoding.
+     *
+     * - Letters, numbers, unreserved (`_-!.~'()*`) and allowed characters are left intact.
      */
     @JvmStatic
     fun encode(source: String, vararg allow: Char): String {
         return encode(source, String(allow))
     }
+
+    /**
+     * Encodes and decodes URLs from the command line.
+     *
+     * - `kotlin -cp urlencoder-*.jar net.thauvin.erik.urlencoder.UrlEncoder`
+     */
+    @JvmStatic
+    fun main(args: Array<String>) {
+        val result = processMain(args)
+        if (result.status == 1) {
+            System.err.println(result.output)
+        } else {
+            println(result.output)
+        }
+        exitProcess(result.status)
+    }
+
+    internal data class MainResult(var output: String = usage, var status: Int = 1)
+
+    internal fun processMain(args: Array<String>): MainResult {
+        val result = MainResult()
+        if (args.isNotEmpty() && args[0].isNotBlank()) {
+            val hasDecode = args[0] == "-d"
+            val hasOption = hasDecode || args[0] == "-e"
+            if (!hasOption || args.size >= 2) {
+                val argsList = mutableListOf<String>()
+                argsList.addAll(args)
+                if (hasOption) argsList.removeAt(0)
+                if (hasDecode) {
+                    result.output = decode(argsList.joinToString(" "))
+                } else {
+                    result.output = encode(argsList.joinToString(" "))
+                }
+                result.status = 0
+            }
+        }
+        return result
+    }
 }

lib/src/test/kotlin/net/thauvin/erik/urlencoder/UrlEncoderTest.kt

@@ -19,6 +19,8 @@ package net.thauvin.erik.urlencoder
 
 import net.thauvin.erik.urlencoder.UrlEncoder.decode
 import net.thauvin.erik.urlencoder.UrlEncoder.encode
+import net.thauvin.erik.urlencoder.UrlEncoder.processMain
+import net.thauvin.erik.urlencoder.UrlEncoder.usage
 import org.junit.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
@@ -44,9 +46,10 @@ class UrlEncoderTest {
             assertEquals(it.key, decode(it.value))
         }
         invalid.forEach {
-            assertFailsWith(IllegalArgumentException::class) {
-                decode(it)
-            }
+            assertFailsWith<IllegalArgumentException>(
+                message = it,
+                block = { decode(it) }
+            )
         }
     }
 
@@ -63,4 +66,45 @@ class UrlEncoderTest {
         assertEquals("?test=a%20test", encode("?test=a test", "=?"))
         assertEquals("aaa", encode("aaa", 'a'))
     }
+
+    @Test
+    fun testMainDecode() {
+        var result: UrlEncoder.MainResult
+        validMap.forEach {
+            result = processMain(arrayOf("-d", it.value))
+            assertEquals(result.output, it.key, it.key)
+            assertEquals(result.status, 0, it.key)
+        }
+    }
+
+    @Test
+    fun testMainEncode() {
+        var result: UrlEncoder.MainResult
+        validMap.forEach {
+            result = processMain(arrayOf("-e", it.key))
+            assertEquals(it.value, result.output, "-e ${it.key}")
+            assertEquals(0, result.status, "-e ${it.key}")
+
+            result = processMain(arrayOf(it.key))
+            assertEquals(it.value, result.output, it.value)
+            assertEquals(0, result.status, it.value)
+        }
+
+        invalid.forEach {
+            assertFailsWith<IllegalArgumentException>(
+                message = it,
+                block = { processMain(arrayOf("-d", it)) }
+            )
+        }
+    }
+
+    @Test
+    fun testMainUsage() {
+        var result: UrlEncoder.MainResult
+        for (arg in arrayOf("", " ", "-d", "-e")) {
+            result = processMain(arrayOf(arg))
+            assertEquals(usage, result.output, "processMain('$arg')")
+            assertEquals(1, result.status, "processMain('$arg')")
+        }
+    }
 }