Add Base37 implementation

util/src/main/kotlin/org/openrs2/util/Base37.kt

@@ -0,0 +1,89 @@
+package org.openrs2.util
+
+public object Base37 {
+    private const val MAX_LENGTH: Int = 12
+
+    private val FIRST_VALID_NAME = encode("")
+    private val LAST_VALID_NAME = encode("999999999999")
+
+    private val DECODE_TABLE = CharArray(37) { i ->
+        when (i) {
+            0 -> '_'
+            in 1..26 -> 'a' + (i - 1)
+            else -> '0' + (i - 27)
+        }
+    }
+
+    public fun encode(s: String): Long {
+        // casting to CharSequence avoids a copy
+        val trimmed = (s as CharSequence).trim { it == ' ' || it == '_' }
+        require(trimmed.length <= MAX_LENGTH)
+
+        var n = 0L
+
+        for (c in trimmed) {
+            n *= 37
+
+            when (c) {
+                in 'A'..'Z' -> n += 1 + (c - 'A')
+                in 'a'..'z' -> n += 1 + (c - 'a')
+                in '0'..'9' -> n += 27 + (c - '0')
+                ' ', '_' -> Unit
+                else -> throw IllegalArgumentException()
+            }
+        }
+
+        return n
+    }
+
+    public fun decodeLowerCase(n: Long): String {
+        require(n in FIRST_VALID_NAME..LAST_VALID_NAME)
+        require(n == 0L || n % 37 != 0L)
+
+        val chars = CharArray(MAX_LENGTH)
+        var len = 0
+        var temp = n
+
+        while (temp != 0L) {
+            chars[len++] = DECODE_TABLE[(temp % 37).toInt()]
+            temp /= 37
+        }
+
+        chars.reverse(0, len)
+        return String(chars, 0, len)
+    }
+
+    public fun decodeTitleCase(n: Long): String {
+        require(n in FIRST_VALID_NAME..LAST_VALID_NAME)
+        require(n == 0L || n % 37 != 0L)
+
+        val chars = CharArray(MAX_LENGTH)
+        var len = 0
+        var temp = n
+
+        while (temp != 0L) {
+            var c = DECODE_TABLE[(temp % 37).toInt()]
+            temp /= 37
+
+            if (c == '_') {
+                c = ' '
+                chars[len - 1] = chars[len - 1].uppercaseChar()
+            }
+
+            chars[len++] = c
+        }
+
+        chars.reverse(0, len)
+        chars[0] = chars[0].uppercaseChar()
+
+        return String(chars, 0, len)
+    }
+
+    public fun toLowerCase(s: String): String {
+        return decodeLowerCase(encode(s))
+    }
+
+    public fun toTitleCase(s: String): String {
+        return decodeTitleCase(encode(s))
+    }
+}

util/src/test/kotlin/org/openrs2/util/Base37Test.kt

@@ -0,0 +1,120 @@
+package org.openrs2.util
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+class Base37Test {
+    @Test
+    fun testEncodeBounds() {
+        assertEquals(0, Base37.encode(""))
+        assertEquals(1, Base37.encode("a"))
+        assertEquals(1, Base37.encode("A"))
+        assertEquals(6582952005840035279, Base37.encode("999999999998"))
+        assertEquals(6582952005840035280, Base37.encode("999999999999"))
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.encode("aaaaaaaaaaaaa")
+        }
+    }
+
+    @Test
+    fun testEncodeBoundsWhitespace() {
+        assertEquals(6582952005840035280, Base37.encode("999999999999 "))
+        assertEquals(6582952005840035280, Base37.encode(" 999999999999"))
+        assertEquals(6582952005840035280, Base37.encode(" 999999999999 "))
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.encode("aaaaaaaaaaaaa ")
+        }
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.encode(" aaaaaaaaaaaaa")
+        }
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.encode(" aaaaaaaaaaaaa ")
+        }
+    }
+
+    @Test
+    fun testDecodeLowerCaseBounds() {
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeLowerCase(-1)
+        }
+
+        assertEquals("", Base37.decodeLowerCase(0))
+        assertEquals("a", Base37.decodeLowerCase(1))
+        assertEquals("999999999998", Base37.decodeLowerCase(6582952005840035279))
+        assertEquals("999999999999", Base37.decodeLowerCase(6582952005840035280))
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeLowerCase(6582952005840035281)
+        }
+    }
+
+    @Test
+    fun testDecodeTitleCaseBounds() {
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeTitleCase(-1)
+        }
+
+        assertEquals("", Base37.decodeTitleCase(0))
+        assertEquals("A", Base37.decodeTitleCase(1))
+        assertEquals("999999999998", Base37.decodeTitleCase(6582952005840035279))
+        assertEquals("999999999999", Base37.decodeTitleCase(6582952005840035280))
+
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeTitleCase(6582952005840035281)
+        }
+    }
+
+    @Test
+    fun testEncodeInvalidChar() {
+        assertFailsWith<IllegalArgumentException> {
+            Base37.encode("!")
+        }
+    }
+
+    @Test
+    fun testEncodeWhitespace() {
+        assertEquals(1465402762952, Base37.encode("Open Rs2"))
+        assertEquals(1465402762952, Base37.encode("open_rs2"))
+        assertEquals(1465402762952, Base37.encode(" Open Rs2 "))
+        assertEquals(1465402762952, Base37.encode("_Open Rs2_"))
+    }
+
+    @Test
+    fun testDecodeLowerCaseWhitespace() {
+        assertEquals("open_rs2", Base37.decodeLowerCase(1465402762952))
+    }
+
+    @Test
+    fun testDecodeTitleCaseWhitespace() {
+        assertEquals("Open Rs2", Base37.decodeTitleCase(1465402762952))
+    }
+
+    @Test
+    fun testDecodeLowerCaseTrailingWhitespace() {
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeLowerCase(54219902229224)
+        }
+    }
+
+    @Test
+    fun testDecodeTitleCaseTrailingWhitespace() {
+        assertFailsWith<IllegalArgumentException> {
+            Base37.decodeTitleCase(54219902229224)
+        }
+    }
+
+    @Test
+    fun testToLowerCase() {
+        assertEquals("open_rs2", Base37.toLowerCase(" OpEn rS2_"))
+    }
+
+    @Test
+    fun testToTitleCase() {
+        assertEquals("Open Rs2", Base37.toTitleCase(" OpEn rS2_"))
+    }
+}