initial commit

.gitignore

@@ -0,0 +1,146 @@
+
+# Created by https://www.toptal.com/developers/gitignore/api/java,intellij,maven
+# Edit at https://www.toptal.com/developers/gitignore?templates=java,intellij,maven
+
+### Intellij ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn.  Uncomment if using
+# auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+# *.iml
+# *.ipr
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# IntelliJ
+out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Intellij Patch ###
+# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
+
+# *.iml
+# modules.xml
+# .idea/misc.xml
+# *.ipr
+
+# Sonarlint plugin
+# https://plugins.jetbrains.com/plugin/7973-sonarlint
+.idea/**/sonarlint/
+
+# SonarQube Plugin
+# https://plugins.jetbrains.com/plugin/7238-sonarqube-community-plugin
+.idea/**/sonarIssues.xml
+
+# Markdown Navigator plugin
+# https://plugins.jetbrains.com/plugin/7896-markdown-navigator-enhanced
+.idea/**/markdown-navigator.xml
+.idea/**/markdown-navigator-enh.xml
+.idea/**/markdown-navigator/
+
+# Cache file creation bug
+# See https://youtrack.jetbrains.com/issue/JBR-2257
+.idea/$CACHE_FILE$
+
+# CodeStream plugin
+# https://plugins.jetbrains.com/plugin/12206-codestream
+.idea/codestream.xml
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+### Maven ###
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+.mvn/timing.properties
+# https://github.com/takari/maven-wrapper#usage-without-binary-jar
+.mvn/wrapper/maven-wrapper.jar
+
+# End of https://www.toptal.com/developers/gitignore/api/java,intellij,maven

namespace to language placeholders.iml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

src/Main.java

@@ -0,0 +1,140 @@
+import java.math.BigInteger;
+import java.util.ArrayList;
+
+public class Main {
+	public static void main(String[] args) {
+		if (args.length != 2) {
+			System.err.println("Usage: java -jar <jar file> (encode|decode) <value>");
+			System.exit(-1);
+		}
+
+		switch (args[0]) {
+			case "encode" -> encode(args[1]);
+			case "decode" -> decode(args[1]);
+			default -> System.err.printf("invalid command %s. Expected either \"encode\" or \"decode\".%n", args[0]);
+		}
+
+		final var namespace = args[0];
+	}
+
+	private static void encode(final String namespace) {
+		if (!namespace.matches("^[a-z0-9_.-]+$")) {
+			System.err.printf("invalid namespace %s%n", namespace);
+			System.exit(-1);
+		}
+
+		final boolean fullCharSet = !namespace.matches("^[a-z_]+$");
+
+		BigInteger value = BigInteger.ZERO;
+		final int base = fullCharSet ? 39 : 27;
+		final BigInteger multiplier = BigInteger.valueOf(base);
+
+		for (char curChar : namespace.toCharArray()) {
+			//The add one is here to create a consistent offset. In case a namespace starts with 'a', we don't want
+			// the first digit as 0. 
+			value = value.multiply(multiplier)
+			             .add(BigInteger.valueOf(getCharValue(curChar) + 1));
+		}
+
+		// ceil((value.bitLength() + 1) / 31)
+		// Int division always floors, but ceil can be expressed with ((n - 1) / m) +1
+		// Since n = value.bitLength() + 1, the + 1 with the - 1 cancel each other out.
+		// The + 1 is needed because we use an additional bit to store the value of fullCharSet
+		final int length = value.bitLength() / 31 + 1;
+
+		final int[] placeholders = new int[length];
+		final BigInteger twoPow31 = BigInteger.valueOf(0x80_00_00_00L);
+
+		for (int i = length -1; i >= 0; i--) {
+			final var divMod = value.divideAndRemainder(twoPow31);
+
+			placeholders[i] = divMod[1].intValueExact();
+			value = divMod[0];
+
+			if (i == 0 && fullCharSet) {
+				placeholders[0] |= 0x40_00_00_00;
+			}
+		}
+
+		final var result = new StringBuilder();
+		for (int placeholder : placeholders) {
+			result.append("%")
+			      .append(Integer.toUnsignedString(placeholder))
+			      .append("$s");
+		}
+
+		System.out.println(result);
+	}
+
+	private static int getCharValue(char c) {
+		if (c >= 'a') {
+			return c - 'a';
+		} else if (c == '_') {
+			return 26;
+		} else if (c >= '0') {
+			return c - '0' + 27;
+		} else if (c == '-') {
+			return 37;
+		} else {
+			return 38;
+		}
+	}
+
+	private static void decode(final String encodedNamespace) {
+		if (!encodedNamespace.matches("^(?:%[1-9][0-9]+\\$s)+$")) {
+			System.err.printf("invalid encoded namespace %s%n", encodedNamespace);
+			System.exit(-1);
+		}
+
+		final String trimmed = encodedNamespace.substring(1, encodedNamespace.length() - 2);
+		final String[] placeholderStrings = trimmed.split("\\$s%");
+		final int[] placeholders = new int[placeholderStrings.length];
+
+		for (int i = 0; i < placeholders.length; i++) {
+			placeholders[i] = Integer.parseInt(placeholderStrings[i]);
+		}
+		boolean fullCharSet = (placeholders[0] & 0x40_00_00_00) > 0;
+		placeholders[0] &= 0xBF_FF_FF_FF;
+
+		final BigInteger twoPow31 = BigInteger.valueOf(0x80_00_00_00L);
+		BigInteger value = BigInteger.ZERO;
+
+		for (int placeholder : placeholders) {
+			value = value.multiply(twoPow31);
+			value = value.add(BigInteger.valueOf(placeholder));
+		}
+
+		final int base = fullCharSet ? 39 : 27;
+		final BigInteger divisor = BigInteger.valueOf(base);
+		final var characters = new ArrayList<Character>();
+
+		while (value.compareTo(BigInteger.ZERO) > 0) {
+			value = value.subtract(BigInteger.ONE);
+			final BigInteger[] divMod = value.divideAndRemainder(divisor);
+
+			value = divMod[0];
+			characters.add(getCharFromValue(divMod[1].intValueExact()));
+		}
+
+		final var chars = new char[characters.size()];
+		for(int i = 0; i < chars.length; i++) {
+			chars[i] = characters.get(chars.length - i - 1);
+		}
+
+		System.out.println(new String(chars));
+	}
+
+	private static char getCharFromValue(int value) {
+		if (value < 26) {
+			return (char) ('a' + value);
+		} else if (value == 26) {
+			return '_';
+		} else if (value < 37) {
+			return (char) ('0' + value - 27);
+		} else if (value == 37) {
+			return '-';
+		} else {
+			return '.';
+		}
+	}
+}