Initial Commit.

.gitattributes

@@ -0,0 +1,6 @@
+#
+# https://help.github.com/articles/dealing-with-line-endings/
+#
+# These are explicitly windows files and should use crlf
+*.bat           text eol=crlf
+

.gitignore

@@ -0,0 +1,5 @@
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build

.vscode/launch.json

@@ -0,0 +1,21 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "java",
+            "name": "Current File",
+            "request": "launch",
+            "mainClass": "${file}"
+        },
+        {
+            "type": "java",
+            "name": "App",
+            "request": "launch",
+            "mainClass": "butler.App",
+            "projectName": "app"
+        }
+    ]
+}

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "java.configuration.updateBuildConfiguration": "interactive"
+}

app/build.gradle

@@ -0,0 +1,50 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * This generated file contains a sample Java application project to get you started.
+ * For more details take a look at the 'Building Java & JVM projects' chapter in the Gradle
+ * User Manual available at https://docs.gradle.org/7.3/userguide/building_java_projects.html
+ */
+
+plugins {
+    // Apply the application plugin to add support for building a CLI application in Java.
+    id 'application'
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(17)
+    }
+}
+
+repositories {
+    // Use Maven Central for resolving dependencies.
+    mavenCentral()
+    maven {
+        url 'https://dogforce-games.com/maven'
+    }
+}
+
+dependencies {
+    // Use JUnit Jupiter for testing.
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.7.2'
+
+    // This dependency is used by the application.
+    implementation 'net.sf.jopt-simple:jopt-simple:5.0.4'
+    implementation 'org.apache.logging.log4j:log4j-api:2.20.0'
+    implementation 'org.apache.logging.log4j:log4j-core:2.20.0'
+
+    implementation 'com.github.jgonian:commons-ip-math:1.32'
+
+    implementation 'dev.gigaherz.util.gddl:gddl2:2.0.0-alpha.2'
+}
+
+application {
+    // Define the main class for the application.
+    mainClass = 'butler.App'
+}
+
+tasks.named('test') {
+    // Use JUnit Platform for unit tests.
+    useJUnitPlatform()
+}

app/src/main/java/butler/App.java

@@ -0,0 +1,321 @@
+package butler;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadPoolExecutor;
+
+import com.sun.net.httpserver.HttpServer;
+
+import butler.rule.Rule;
+import butler.source.SourceData;
+import joptsimple.OptionParser;
+import joptsimple.OptionSet;
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.config.Configurator;
+import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.LogManager;
+
+import dev.gigaherz.util.gddl2.GDDL;
+import dev.gigaherz.util.gddl2.exceptions.ParserException;
+import dev.gigaherz.util.gddl2.structure.GddlDocument;
+import dev.gigaherz.util.gddl2.structure.GddlElement;
+import dev.gigaherz.util.gddl2.structure.GddlList;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/****************
+ * 
+ * Butler
+ *  A webhook filtering and forwarding tool
+ * 
+ ****************
+ * 
+ * Behaviour is completely configuration-driven.
+ * 
+ * The configuration allows you to specify the listening port and URL, as well as an array of rules.
+ * Rules determine what to do when an incoming webhook is received.
+ * 
+ * Rules have two components; a list of filters, and a list of actions.
+ *  Filters:
+ *      - Allow you to narrow rules down to their source
+ *      - Allow you to narrow rules down by webhook content
+ *      - Allow you to narrow rules down by (optionally) the context sent by a Github Hookshot.
+ * 
+ *  Actions:
+ *      - Allow you to rewrite webhook content
+ *      - Allow you to forward a webhook via a different URL
+ *      - Allow you to block a webhook so that it is not sent on
+ * 
+ * Combined, this means that you can create rules that separate organization-wide Github webhooks to multiple Discord channels
+ *  (the reason this project exists)
+ * or to simply not allow certain webhooks to be sent.
+ * 
+ ****************
+ *
+ * An example rule is provided that redirects Github Webhooks for the TheCurle/butler repository to example.com:
+ * ```
+ * {
+ *   rules: [
+ *      rule {
+ *          name: "TheCurle/Butler to example.com",
+ *          filters: [
+ *              source { origin: "github.com" }
+ *              github { user: "TheCurle", repo: "butler" }
+ *          ]
+ *          actions: {
+ *              forward { url: "example.com/" }
+ *          }
+ *      }  
+ *   ]
+ * }
+ * ```
+ * 
+ * An example rule is provided that prevents a custom webhook containing the word "milk" from being forwarded.
+ * ```
+ * {
+ *   rules: [
+ *      rule { 
+ *          name: "filter out milk",
+ *          filters: [
+ *              content { str: "milk" }
+ *          ]
+ *          actions: [
+ *              reject {}
+ *          ]
+ *      }
+ *   ]
+ * }
+ * ```
+ * 
+ ****************
+ * 
+ * Rules and Names
+ * 
+ * Rules are required to have names.
+ * This is an intentional decision designed to make it easier to navigate large configuration files with lots of rules.
+ * By string-searching the effect that a rule has, you can find the exact code that makes it happen.
+ * 
+ * This is designed to put maintenance and longevity of the system first, though can seem like a strange and arbitrary decision at first.
+ * 
+ ****************
+ * 
+ * Filter and Action Types
+ * 
+ * Since filters and actions can have different parameters depending on what the type is, the type must be specified before any further parsing.
+ * This allows for an interesting kind of "dynamic dispatch", where the rest of the rule is parsed based on the type given.
+ * 
+ * Eventually this will allow for custom types to be specified in addon code, but this is a very far-future idea.
+ * 
+ ****************
+ * 
+ * Filtering Conditions
+ * 
+ * Two "types" of filtering conditions are provided; source and content, with an extra GitHub integration provided.
+ * 
+ * Source:
+ *  - will attempt to match the URL where the webhook originated.
+ *    the shortcut "github" is provided that matches a user-agent of "Github-Hookshot".
+ *    other content is taken as a substring of the incoming URL. 
+ *      for example, if the remote IP has a R-DNS resolution, it will match that.
+ *      Otherwise, the IP is matched directly.
+ * Content:
+ *  - will attempt to match a substring of the webhook content.
+ * GitHub:
+ *    github sources have a few shorthands:
+ *      - "repository": matches the NAME of the repository that relates to this Github webhook
+ *      - "user": matches the USER that OWNS THE REPOSITORY that relates to this Github webhook
+ *      - "sender": matches the USER that TRIGGERED this Github webhook
+ *      as an example, the user "octocat" pushing to "torvalds/linux" will have linux as the repository, torvalds as the user, and octocat as the sender.
+ * 
+ ****************
+ * 
+ * Actions
+ * 
+ * There are three main types of action: rewrite, forward, reject.
+ * 
+ * Rewrite:
+ *  - will replace all instances of a string in the JSON body with another string.
+ * Forward:
+ *  - will send the webhook as-is to another URL (with an X-Proxy header added)
+ * Reject:
+ *  - will reject the webhook and close the connection with a 403.
+ * 
+ */
+
+public class App {
+
+    public static String version = "1.0f";
+
+    private static int DEFAULT_PORT = 6000;
+    private static String DEFAULT_CONFIG_PATH = "./config.gddl";
+
+    // The Web server listening for incoming webhook requests
+    private HttpServer server;
+    private ThreadPoolExecutor executor;
+
+    // The instance of the HttpHandler that actually redirects the webhooks.
+    private WebhookHandler handler;
+
+    // The configuration file set by the user, read once at read.
+    private GddlDocument config;
+    // The list of rules that set how the program should react to an incoming webhook.
+    private List<Rule> rules;
+
+    // The logger for this class
+    private static Logger logger = LogManager.getLogger(App.class);
+
+    public App(OptionSet options) {
+        int port = options.has("port") ? (int) options.valueOf("port") : 
+                        DEFAULT_PORT;
+        try {
+            server = HttpServer.create(new InetSocketAddress("localhost", port), 0);
+        } catch (IOException e) {
+            logger.error("[INIT] Failed to bind to port {}, aborting.", port);   
+            System.exit(1);
+        }
+
+        String path = options.has("config") ? (String) options.valueOf("config") :
+                        DEFAULT_CONFIG_PATH;
+        try {
+            config = GDDL.fromFile(path);
+            parseConfig();
+        } catch (ParserException | IOException e) {
+            logger.error("[INIT] Failed to load configuration file at path {}, aborting.", path);
+            System.exit(2);
+        }
+
+        executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(5);
+        handler = new WebhookHandler();
+
+        logger.info("[INIT] Registering handler for all incoming webhooks.");
+        server.createContext("/", handler);
+        server.setExecutor(executor);
+    }
+
+    public void begin() {
+        server.start();
+    }
+    
+    private void parseSources(List<SourceData> list, GddlElement<?> entry) {
+        logger.info("[CONF] Reading Sources list..");
+        if (!entry.isList()) {
+            logger.error("[CONF] Sources should be a list. Aborting..");
+            System.exit(11);
+        }
+
+        GddlList sources = entry.asList();
+        sources.forEach(source -> {
+            if (!source.isMap() || source.asMap().hasTypeName() || source.asMap().getTypeName() != "source") {
+                logger.error("[CONF] Source entry should be a map with type \"source\". Aborting.");
+                System.exit(12);
+            }
+
+            SourceData data = SourceData.from(source);
+            logger.info("[CONF] Adding source {} to list of known hosts.", data.host());
+            list.add(data);
+        });
+    }
+
+    private void parseRules(List<Rule> rules, List<SourceData> sources, GddlElement<?> entry) {
+        logger.info("[CONF] Reading Rules list..");
+
+        if (!entry.isList()) {
+            logger.error("[CONF] Rules should be a list. Aborting...");
+            System.exit(17);
+        }
+
+        GddlList list = entry.asList();
+        list.forEach(rule -> {
+            if (!rule.isMap() || !rule.asMap().hasTypeName() || !rule.asMap().getTypeName().equals("rule")) {
+                logger.error("[CONF] Rules entry should be a map with type \"rule\". Aborting.");
+                System.exit(18);
+            }
+
+            Rule data = Rule.from(rule, sources);
+            logger.info("[CONF] Adding rule {} to list of active rules.", data.getName());
+            rules.add(data);
+        });
+    }
+
+    private void parseConfig() {
+        GddlElement<?> root = config.getRoot();
+        if (!root.isMap() || !root.asMap().containsKey("rules") || !root.asMap().containsKey("sources")) {
+            logger.error("[INIT] Malformed configuration file! The root element should be a map of rules and sources.");
+            System.exit(3);
+        }
+        
+        GddlMap cfgList = root.asMap();
+        rules = new ArrayList<Rule>();
+
+        List<SourceData> sources = new ArrayList<>();
+        cfgList.forEach((key, entry) -> {
+            if (key.equals("sources")) {
+                parseSources(sources, entry);
+            } else if (key.equals("rules")) {
+                parseRules(rules, sources, entry);
+            } else {
+                logger.error("[CONF] Unknown entry {} in configuration map. Aborting..", key);
+                System.exit(10);
+            }
+        });
+    }
+
+    public static void main(String[] args) {
+        Configurator.setAllLevels(LogManager.getRootLogger().getName(), Level.INFO);
+        logger.info("[INIT] Butler v{} starting.", version);
+
+        OptionParser parser = new OptionParser();
+        parser.accepts("port").withRequiredArg().ofType(Integer.class);
+        parser.accepts("config").withRequiredArg();
+        
+        OptionSet opts = parser.parse(args);
+
+        App app = new App(opts);
+
+        int port = opts.has("port") ? (int) opts.valueOf("port") : 
+                    DEFAULT_PORT;
+
+        logger.info("[CORE] Listening for webhooks on port {}.", port);
+        app.begin();
+    }
+
+    /**
+     * The class that actually handles redirecting the webhooks.
+     * When a new request is received, the handle method is called.
+     * If the request is a GET, a 403 is returned.
+     * If the request is a PUT, it is handled as per the config.
+     * Generally, the webhook is ignored unless a specific flag is set, in which case it is modified and redirected to another server.
+     * This allows for easy webhook filtering and querying.
+     */
+    class WebhookHandler implements HttpHandler {
+
+        @Override
+        public void handle(HttpExchange exchange) throws IOException {
+            logger.debug("[NETW] Incoming Request. {}:{}, from {}.", exchange.getRequestMethod(), exchange.getRequestURI(), exchange.getRemoteAddress());
+            if (exchange.getRequestMethod().equals("GET")) {
+                logger.info("[NETW] Refusing GET request from {}.", exchange.getRemoteAddress());
+                exchange.sendResponseHeaders(403, 0);
+            } else if (exchange.getRequestMethod().equals("POST")) {
+                logger.info("[NETW] POST from {}.", exchange.getRemoteAddress());
+
+                for (Rule rule : rules) {
+                    logger.trace("[RULE] Testing rule {} against POST from {}.", rule.getName(), exchange.getRemoteAddress());
+                    if (rule.tryFilters(exchange)) {
+                        logger.info("[RULE] Rule {} matched. Applying actions.", rule.getName());
+                        if (!rule.applyActions(exchange))
+                            return;
+                    }
+                }
+
+                exchange.sendResponseHeaders(200, 0);
+                exchange.close();
+            }
+        }
+    }
+}

app/src/main/java/butler/action/Action.java

@@ -0,0 +1,10 @@
+package butler.action;
+
+import com.sun.net.httpserver.HttpExchange;
+
+public interface Action {
+    /**
+     * Perform the given action against the given HttpExchange.
+     */
+    boolean perform(HttpExchange exc);
+}

app/src/main/java/butler/action/ForwardAction.java

@@ -0,0 +1,109 @@
+package butler.action;
+
+import java.io.BufferedReader;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.UnsupportedEncodingException;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.ProtocolException;
+import java.net.URL;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import com.sun.net.httpserver.HttpExchange;
+
+import butler.App;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * Takes the webhook headers and content, and sends it on to another URL.
+ * An X-Proxy header is added with the value of "Butler" followed by the version number.
+ */
+public class ForwardAction implements Action {
+    private Logger logger = LogManager.getLogger(ForwardAction.class);
+    private String url;
+
+    public ForwardAction(GddlMap map) {
+        url = map.values().stream().findFirst().get().stringValue();
+    }
+    
+    @Override
+    public boolean perform(HttpExchange exc) {
+
+        logger.info("[NETW] Redirecting request from {} (target {}) to {}.", exc.getRemoteAddress().getHostString(), exc.getLocalAddress().getHostName(), url);
+
+        ByteArrayOutputStream result = new ByteArrayOutputStream();
+        byte[] buffer = new byte[1024];
+
+        try {
+            for (int length; (length = exc.getRequestBody().read(buffer)) != -1; ) {
+                result.write(buffer, 0, length);
+            }
+        } catch (IOException e) {
+            logger.error("[NETW] Unable to read request body for request from {}. Aborting.", exc.getRemoteAddress().getHostString());
+            return false;
+        }
+        String content;
+        try {
+            content = result.toString("UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            logger.error("[NETW] Unable to read request body for request from {}. Aborting.", exc.getRemoteAddress().getHostString());
+            return false;
+        }
+
+        URL req;
+        HttpURLConnection conn;
+
+        try {
+            req = new URL(url);
+        } catch (MalformedURLException e) {
+            logger.error("[NETW] Unable to parse destination url {}. Aborting.", url);
+            return false;
+        }
+
+        try {
+            conn = (HttpURLConnection) req.openConnection();
+        } catch (IOException e) {
+            logger.error("[NETW] Unable to open a connection to {}. Aborting.", url);
+            return false;
+        }
+
+        try {
+            conn.setRequestMethod("POST");
+            exc.getRequestHeaders().forEach((name, val) -> conn.setRequestProperty(name, val.get(0)));
+            conn.setRequestProperty("X-Proxy", "Butler " + App.version);
+        } catch (ProtocolException e) {
+            logger.error("[NETW] Unable to set request method. Java is broken??");
+            return false;
+        }
+        conn.setDoOutput(true); 
+        
+        DataOutputStream out;
+        try {
+            conn.setFixedLengthStreamingMode(content.length());
+            conn.connect();
+            out = new DataOutputStream(conn.getOutputStream());
+            out.write(content.getBytes());
+        } catch (IOException e) {
+            logger.error("[NETW] Unable to send a request to target url {}. Aborting.", url);
+            return false;
+        }
+
+        try (BufferedReader res = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {
+            StringBuilder sb = new StringBuilder();
+            String line;
+            while ((line = res.readLine()) != null) 
+                sb.append(line);
+
+            logger.trace("[NETW] POST to {} returned string {}.", url, sb.toString());
+        } catch (IOException e) {
+            logger.error("[NETW] Failed to read response from {}. Aborting.", url);
+            System.exit(37);
+        }
+        return true;
+    }
+}

app/src/main/java/butler/action/RejectAction.java

@@ -0,0 +1,23 @@
+package butler.action;
+
+import com.sun.net.httpserver.HttpExchange;
+
+import butler.rule.Rule;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * An action that rejects the given webhook.
+ * Allows active rejection (ie. block IP ranges from making otherwise valid requests).
+ */
+public class RejectAction implements Action {
+
+    public RejectAction(GddlMap entry) {
+    }
+
+    @Override
+    public boolean perform(HttpExchange exc) {
+        Rule.logger.info("[RULE] Rejecting POST from {}.", exc.getRemoteAddress());
+        exc.close();
+        return false;
+    }
+}

app/src/main/java/butler/filter/Filter.java

@@ -0,0 +1,13 @@
+package butler.filter;
+
+import com.sun.net.httpserver.HttpExchange;
+
+public interface Filter {
+    
+    /**
+     * Run the filter against the given HTTP request.
+     * @param exchange an in-progress HTTP request with all context given.
+     * @return whether or not the filter matched the request
+     */
+    boolean test(HttpExchange exchange);
+}

app/src/main/java/butler/filter/FilterContent.java

@@ -0,0 +1,32 @@
+package butler.filter;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import com.sun.net.httpserver.HttpExchange;
+
+import butler.rule.Rule;
+import butler.source.SourceData;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * Matches the content of the request body against a given string.
+ */
+public class FilterContent implements Filter {
+
+    private String content = "";
+
+    public FilterContent(GddlMap map, List<SourceData> sources) {
+        content = map.values().stream().findFirst().get().stringValue();
+    }
+
+    @Override
+    public boolean test(HttpExchange exchange) {
+        Rule.logger.trace("[RULE] Testing content of request against {}.", content);
+        String body = new BufferedReader(new InputStreamReader(exchange.getRequestBody())).lines().collect(Collectors.joining("\n"));
+        return body.contains(content);
+    }
+    
+}

app/src/main/java/butler/filter/FilterGithub.java

@@ -0,0 +1,107 @@
+package butler.filter;
+
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import com.sun.net.httpserver.HttpExchange;
+
+import butler.source.SourceData;
+import dev.gigaherz.util.gddl2.GDDL;
+import dev.gigaherz.util.gddl2.exceptions.ParserException;
+import dev.gigaherz.util.gddl2.structure.GddlDocument;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * A Github filter.
+ * Allows matching by user/repository, sender, and string content of the webhook.
+ */
+public class FilterGithub implements Filter {
+    private Logger logger = LogManager.getLogger(FilterGithub.class);
+
+    private String user = "";
+    private String sender = "";
+    private String repo = "";
+    private String action = "";
+    private String content = "";
+
+    public FilterGithub(GddlMap map, List<SourceData> sources) {
+        if (map.containsKey("user"))
+            user = map.get("user").stringValue();
+        if (map.containsKey("sender"))
+            sender = map.get("sender").stringValue();
+        if (map.containsKey("repo"))
+            repo = map.get("repo").stringValue();
+        if (map.containsKey("action"))
+            action = map.get("action").stringValue();
+        if (map.containsKey("content"))
+            content = map.get("content").stringValue();
+    }
+
+    @Override
+    public boolean test(HttpExchange exc) {
+        GddlDocument gddl;
+
+        try {
+            gddl = GDDL.fromStream(exc.getRequestBody());
+        } catch (ParserException | IOException e) {
+            logger.error("[RULE] Unable to read JSON content for Github Filter on request from {}. Aborting.", exc.getRemoteAddress());
+            return false;
+        }
+
+        GddlMap map = gddl.getRoot().asMap();
+
+        if (action.length() > 0) {
+            logger.trace("[RULE] Testing GitHub webhook action..");
+            List<String> fields = List.of(action.split("/")[0].split(","));
+            String ctx = action.split("/")[1];
+            logger.trace("[RULE] Searching for an action {} on {}.", ctx, fields);
+
+            for (String field : fields) {
+                if (!map.containsKey(field)) {
+                    logger.trace("[RULE] Webhook does not contain field {}, skipping.", field);
+                    return false;
+                }
+            }
+
+            if (!map.get("action").stringValue().equals(ctx)) {
+                logger.trace("[RULE] Webhook is not applying to action {}, skipping.", ctx);
+            }
+        }
+
+        if (sender.length() > 0) {
+            logger.trace("[RULE] Testing Github webhook user..");
+            String senderLogin = map.get("sender").asMap().get("login").stringValue();
+            if (!senderLogin.equals(sender)) {
+                logger.trace("[RULE] GitHub webhook sender {} does not match specified user {}, skipping..", senderLogin, sender);
+                return false;
+            }
+        }
+
+        if (repo.length() > 0) {
+            logger.trace("[RULE] Testing Github webhook repository..");
+            String repositoryName = map.get("repository").asMap().get("name").stringValue();
+            if (!repositoryName.equals(repo)) {
+                logger.trace("[RULE] GitHub webhook repository {} does not match specified repo {}, skipping.", repositoryName, repo);
+                return false;
+            }
+
+            if (user.length() > 0) {
+                String repositoryFullName = map.get("repository").asMap().get("full_name").stringValue();
+                if (!(user + "/" + repositoryName).equals(repositoryFullName)) {
+                    logger.trace("[RULE] GitHub webhook repository {} does not belong to specified user {}, skipping", repositoryFullName, user);
+                }
+            }
+        }
+
+        if (content.length() > 0) {
+            logger.warn("[RULE] Github Content filter is unsupported. Skipping.");
+        }
+
+
+        return true;
+    }
+    
+}

app/src/main/java/butler/filter/FilterSource.java

@@ -0,0 +1,51 @@
+package butler.filter;
+
+import java.util.List;
+
+import com.sun.net.httpserver.HttpExchange;
+
+import butler.source.SourceData;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * Filter by the source of the webhook.
+ * The remote address of the request is checked agains the content of the Source Filter.
+ * Optionally, if the source is a domain, then it is resolved and checked against the incoming URL.
+ * If a match is found, then the associated action is triggered.
+ */
+public class FilterSource implements Filter {
+    private String origin;
+    private List<SourceData> sources;
+
+    public FilterSource(GddlMap data, List<SourceData> knownSources) {
+        // The origin can be under any name, but it must be the first (and only) entry in the filter.
+        origin = data.values().stream().findFirst().get().stringValue();
+        sources = knownSources;
+    }
+
+    public boolean test(HttpExchange exc) {
+        // Match the literal address, if given.
+        String addr = exc.getRemoteAddress().getAddress().getHostAddress();
+        if (origin.equals(addr))
+            return true;
+
+        // If a Reverse DNS ip can be resolved, try that.
+        String host = exc.getRemoteAddress().getHostName();
+        if (!host.equals(addr) && host.equals(origin))
+            return true;
+        
+        // Also match the Host header.
+        if (exc.getRequestHeaders().get("Host").get(0).equals(origin))
+            return true;
+
+        for (SourceData source : sources) {
+            // If the literal address doesn't match, try it as a host/nickname in the list of known sources.
+            if (origin.equals(source.host())) {
+                return source.test(exc.getRemoteAddress().getHostName());
+            }
+        }
+
+        return false;
+    }
+    
+}

app/src/main/java/butler/rule/Rule.java

@@ -0,0 +1,190 @@
+package butler.rule;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import butler.action.Action;
+import butler.filter.Filter;
+import butler.source.SourceData;
+import dev.gigaherz.util.gddl2.structure.GddlElement;
+import dev.gigaherz.util.gddl2.structure.GddlList;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+import com.sun.net.httpserver.HttpExchange;
+
+/**
+ * The core class that encodes the information of a redirect rule.
+ * A rule contains: 
+ *  - A name (for easy identification)
+ *  - A set of conditions (if all are matched, the action is performed)
+ *  - A set of actions
+ * 
+ * Actions are performed in order; so if a request is dropped and then redirected, the redirect will fail.
+ * 
+ */
+public class Rule {
+    // The name of this rule
+    private String name;
+    // The list of filters that specify whether the current rule should apply
+    private List<Filter> filters;
+    // The list of actions that should be executed when the current rule applies
+    private List<Action> actions;
+
+    public static Logger logger = LogManager.getLogger(Rule.class);
+
+    public Rule(String name, List<Filter> filters, List<Action> actions) {
+        this.name = name;
+        this.filters = filters;
+        this.actions = actions;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Try all the filters in the rule against the given exchange.
+     * @param exc an active HttpExchange for an incoming webhook request.
+     * @return false if any filter failed, true if all filters matched.
+     */
+    public boolean tryFilters(HttpExchange exc) {
+        for (Filter filter : filters) {
+            logger.trace("[RULE] ({}) Trying filter {} against {}.", name, filter.getClass().getSimpleName(), exc.getRemoteAddress());
+            if (!filter.test(exc)) {
+                logger.trace("[RULE] Filter failed.");
+                return false;
+            }
+        }
+
+        logger.trace("[RULE] All filters passed for rule {}.", name);
+        return true;
+    }
+
+    /**
+     * Apply all relevant actions of the rule against the given exchange.
+     */
+    public boolean applyActions(HttpExchange exc) {
+        for (Action action : actions) {
+            logger.trace("[RULE] ({}) Applying action {} for request from {}.", name, action.getClass().getSimpleName(), exc.getRemoteAddress().getHostName());
+            // Terminal actions return false; stop processing if that happens.
+            if (!action.perform(exc))
+                return false;
+        }
+        return true;
+    }
+
+    public static Rule from(GddlElement<?> entry, List<SourceData> sources) {
+        GddlMap map = entry.asMap();
+        if (!map.containsKey("name")) {
+            Rule.logger.error("[CONF] Rules must have a name. Aborting..");
+            System.exit(4);
+        }
+        
+        String name = map.get("name").asValue().stringValue();
+
+        if (!map.containsKey("filters") && !map.get("filters").isList() ) {
+            Rule.logger.error("[CONF] Rule {} must have a list of filters. Aborting..", name);
+            System.exit(5);
+        }
+
+        List<Filter> filters = new ArrayList<>();
+        GddlList filterList = map.get("filters").asList();
+        filterList.forEach(listEntry -> {
+            if (!listEntry.isMap()) {
+                Rule.logger.error("[CONF] Entry in the filters list is not a Map. Aborting..");
+                System.exit(6);
+            }
+
+            GddlMap eMap = listEntry.asMap();
+            if (!eMap.hasTypeName()) {
+                Rule.logger.error("[CONF] Entry in the filters list does not have a type. Aborting..");
+                System.exit(7);
+            }
+
+            String filterType = eMap.getTypeName();
+            String filterClassName = "butler.filter.Filter" + filterType.substring(0, 1).toUpperCase() + filterType.substring(1);
+            try {
+                Class<?> filterClass = Class.forName(filterClassName);
+                Constructor<?> filterCtor = filterClass.getConstructor(GddlMap.class, List.class);
+                filters.add((Filter) filterCtor.newInstance(eMap, (List<?>) sources));
+            } catch (ClassNotFoundException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which does not exist. Aborting..", filterType, filterClassName);
+                System.exit(8);
+            } catch (NoSuchMethodException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which does not have the correct constructor (String,List). Aborting..", filterType, filterClassName);
+                System.exit(20);
+            } catch (SecurityException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which could not be instantiated ({}). Aborting..", filterType, filterClassName, e.getMessage());
+                System.exit(21);
+            } catch (InstantiationException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which could not be instantiated ({}). Aborting..", filterType, filterClassName, e.getMessage());
+                System.exit(22);
+            } catch (IllegalAccessException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which could not be instantiated ({}). Aborting..", filterType, filterClassName, e.getMessage());
+                System.exit(23);
+            } catch (IllegalArgumentException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which could not be instantiated ({}). Aborting..", filterType, filterClassName, e.getMessage());
+                System.exit(24);
+            } catch (InvocationTargetException e) {
+                Rule.logger.error("[CONF] Filter type {} resolves to {}.class, which could not be instantiated ({}). Aborting..", filterType, filterClassName, e.getMessage());
+                System.exit(25);
+            }
+        });
+
+        if (!map.containsKey("actions") && !map.get("actions").isList() ) {
+            Rule.logger.error("[CONF] Rule {} must have a list of actions. Aborting..");
+            System.exit(26);
+        }
+
+        List<Action> actions = new ArrayList<>();
+        GddlList actionList = map.get("actions").asList();
+        actionList.forEach(listEntry -> {
+            if (!listEntry.isMap()) {
+                Rule.logger.error("[CONF] Entry in the actions list is not a Map. Aborting..");
+                System.exit(27);
+            }
+
+            GddlMap aMap = listEntry.asMap();
+            if (!aMap.hasTypeName()) {
+                Rule.logger.error("[CONF] Entry in the actions list does not have a type. Aborting..");
+                System.exit(28);
+            }
+
+            String actionType = aMap.getTypeName();
+            String actionClassName = "butler.action." + actionType.substring(0, 1).toUpperCase() + actionType.substring(1) + "Action";
+            try {
+                Class<?> actionClass = Class.forName(actionClassName);
+                Constructor<?> actionCtor = actionClass.getConstructor(GddlMap.class);
+                actions.add((Action) actionCtor.newInstance(aMap));
+            } catch (ClassNotFoundException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which does not exist. Aborting..", actionType, actionClassName);
+                System.exit(29);
+            } catch (NoSuchMethodException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which does not have the correct constructor (String). Aborting..", actionType, actionClassName);
+                System.exit(30);
+            } catch (SecurityException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which could not be instantiated. Aborting..", actionType, actionClassName);
+                System.exit(31);
+            } catch (InstantiationException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which could not be instantiated. Aborting..", actionType, actionClassName);
+                System.exit(32);
+            } catch (IllegalAccessException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which could not be instantiated. Aborting..", actionType, actionClassName);
+                System.exit(33);
+            } catch (IllegalArgumentException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which could not be instantiated. Aborting..", actionType, actionClassName);
+                System.exit(34);
+            } catch (InvocationTargetException e) {
+                Rule.logger.error("[CONF] Action type {} resolves to {}.class, which could not be instantiated. Aborting..", actionType, actionClassName);
+                System.exit(35);
+            }
+        });
+
+        return new Rule(name, filters, actions);
+    }
+}

app/src/main/java/butler/source/SourceData.java

@@ -0,0 +1,74 @@
+package butler.source;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.github.jgonian.ipmath.Ipv4;
+import com.github.jgonian.ipmath.Ipv4Range;
+
+import butler.rule.Rule;
+import dev.gigaherz.util.gddl2.structure.GddlElement;
+import dev.gigaherz.util.gddl2.structure.GddlList;
+import dev.gigaherz.util.gddl2.structure.GddlMap;
+
+/**
+ * Provides a list of data that can be used to identify webhook sources.
+ * They are provided in config by a list of strings of form x.y.z.w/a, which encodes a subnet.
+ * These are mapped to a single domain by name, or alternatively to a nickname.
+ *
+ */
+public record SourceData(String host, List<String> subnets) {
+
+    public boolean test(String ip) {
+        for (String subnet : subnets) {
+            if (Ipv4Range.from(subnet.split("/")[0]).andPrefixLength(subnet.split("/")[1]).contains(Ipv4.of(ip)))
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Create a SourceData from the given GddlMap.
+     * @param source the GddlMap of a single entry in the "sources" list of the configuration file.
+     * @return the SourceData representing the single entry given.
+     */
+    public static SourceData from(GddlElement<?> entry) {
+        if (!entry.isMap()) {
+            Rule.logger.error("Sources list entry is not a map. Aborting..");
+            System.exit(36);
+        }
+
+        GddlMap source = entry.asMap();
+
+        if (!source.containsKey("host") || source.containsKey("ranges")) {
+            Rule.logger.error("Source map should contain a host string and a list of ranges. Aborting..");
+            System.exit(13);
+        }
+
+        if (!source.get("host").isString()) {
+            Rule.logger.error("Source host should be a string. Aborting..");
+            System.exit(14);
+        }
+
+        if (!source.get("ranges").isList() || source.get("ranges").asList().size() == 0 || !source.get("ranges").asList().get(0).isString()) {
+            Rule.logger.error("Source ranges should be a non-empty list of Strings. Aborting..");
+            System.exit(15);
+        }
+
+        String host = source.get("host").stringValue();
+        List<String> addresses = new ArrayList<>();
+        GddlList ranges = source.get("ranges").asList();
+        ranges.forEach(range -> {
+            if (!range.isString()) {
+                Rule.logger.error("Source range entry should be a string. Aborting..");
+                System.exit(16);
+            }
+
+            addresses.add(range.stringValue());
+        });
+
+        return new SourceData(host, addresses);
+    }
+
+}

app/src/test/java/butler/AppTest.java

@@ -0,0 +1,12 @@
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+package butler;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class AppTest {
+    @Test void appHasAGreeting() {
+    }
+}

config.gddl

@@ -0,0 +1,23 @@
+{
+    sources: []
+    rules: [
+        rule {
+            name: "Not in my Christian Minecraft server!",
+            filters: [
+                content { str: "poo" }
+            ]
+            actions: [
+                reject {}
+            ]
+        }
+        rule {
+            name: "Test",
+            filters: [
+                source { url: "127.0.0.1" }
+            ]
+            actions: [
+                forward { url: "https://webhook.site/bd2e20cf-6b52-4134-8387-8b6107455b77" }
+            ]
+        }
+    ]
+}

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.3-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle

@@ -0,0 +1,11 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * The settings file is used to specify which projects to include in your build.
+ *
+ * Detailed information about configuring a multi-project build in Gradle can be found
+ * in the user manual at https://docs.gradle.org/7.3/userguide/multi_project_builds.html
+ */
+
+rootProject.name = 'butler'
+include('app')