Several features:

- Ability to serve static files, HTML and CSS are supported so far
 - Consequently, show a simple HTML form to enter the parameters when
   navigating to / (or /index.html).
 - Make the server multi-threaded (in a rather primitive way so far).
 - Use logback instead of the simple-slf4j logger.

labyrinth-server.iml

@@ -13,15 +13,16 @@
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="module" module-name="labyrinth-generator" />
-    <orderEntry type="library" name="Maven: org.apache.pdfbox:pdfbox:2.0.20" level="project" />
+    <orderEntry type="library" name="Maven: org.apache.pdfbox:pdfbox:2.0.25" level="project" />
-    <orderEntry type="library" name="Maven: org.apache.pdfbox:fontbox:2.0.20" level="project" />
+    <orderEntry type="library" name="Maven: org.apache.pdfbox:fontbox:2.0.25" level="project" />
     <orderEntry type="library" name="Maven: commons-logging:commons-logging:1.2" level="project" />
     <orderEntry type="library" name="Maven: io.vavr:vavr:0.10.2" level="project" />
     <orderEntry type="library" name="Maven: io.vavr:vavr-match:0.10.2" level="project" />
     <orderEntry type="library" scope="PROVIDED" name="Maven: org.projectlombok:lombok:1.18.12" level="project" />
     <orderEntry type="library" name="Maven: org.jetbrains:annotations:19.0.0" level="project" />
-    <orderEntry type="library" name="Maven: org.slf4j:slf4j-api:1.7.30" level="project" />
+    <orderEntry type="library" name="Maven: org.slf4j:slf4j-api:1.7.35" level="project" />
-    <orderEntry type="library" name="Maven: org.slf4j:slf4j-simple:1.7.30" level="project" />
+    <orderEntry type="library" name="Maven: ch.qos.logback:logback-classic:1.2.10" level="project" />
+    <orderEntry type="library" name="Maven: ch.qos.logback:logback-core:1.2.10" level="project" />
     <orderEntry type="library" scope="TEST" name="Maven: org.junit.jupiter:junit-jupiter-api:5.6.1" level="project" />
     <orderEntry type="library" scope="TEST" name="Maven: org.apiguardian:apiguardian-api:1.1.0" level="project" />
     <orderEntry type="library" scope="TEST" name="Maven: org.opentest4j:opentest4j:1.2.0" level="project" />

pom.xml

@@ -14,6 +14,10 @@
 	<artifactId>labyrinth-server</artifactId>
 	<version>0.0.1-SNAPSHOT</version>
 
+	<properties>
+		<slf4j.version>1.7.35</slf4j.version>
+	</properties>
+
 	<dependencies>
 		<dependency>
 			<groupId>ch.fritteli.labyrinth</groupId>
@@ -35,12 +39,12 @@
 		<dependency>
 			<groupId>org.slf4j</groupId>
 			<artifactId>slf4j-api</artifactId>
-			<version>1.7.30</version>
+			<version>${slf4j.version}</version>
 		</dependency>
 		<dependency>
-			<groupId>org.slf4j</groupId>
+			<groupId>ch.qos.logback</groupId>
-			<artifactId>slf4j-simple</artifactId>
+			<artifactId>logback-classic</artifactId>
-			<version>1.7.30</version>
+			<version>1.2.10</version>
 		</dependency>
 		<dependency>
 			<groupId>org.junit.jupiter</groupId>
@@ -95,12 +99,24 @@
 	</distributionManagement>
 	<repositories>
 		<repository>
-			<id>repo.gittr.ch</id>
+			<id>repo.gittr.ch.releases</id>
-			<url>https://repo.gittr.ch/</url>
+			<url>https://repo.gittr.ch/releases/</url>
 			<releases>
 				<enabled>true</enabled>
 				<updatePolicy>never</updatePolicy>
 			</releases>
+			<snapshots>
+				<enabled>false</enabled>
+				<updatePolicy>never</updatePolicy>
+			</snapshots>
+		</repository>
+		<repository>
+			<id>repo.gittr.ch.snapshots</id>
+			<url>https://repo.gittr.ch/snapshots/</url>
+			<releases>
+				<enabled>false</enabled>
+				<updatePolicy>never</updatePolicy>
+			</releases>
 			<snapshots>
 				<enabled>true</enabled>
 				<updatePolicy>always</updatePolicy>

src/main/java/ch/fritteli/labyrinth/server/LabyrinthServer.java

@@ -24,20 +24,24 @@ import org.jetbrains.annotations.Nullable;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.InetSocketAddress;
+import java.net.URISyntaxException;
 import java.nio.charset.StandardCharsets;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
 
 @Slf4j
 public class LabyrinthServer {
+    @NonNull
     private final HttpServer httpServer;
+    @NonNull
+    private final ExecutorService executorService = Executors.newCachedThreadPool();
 
-    public LabyrinthServer(@NonNull final ServerConfig config) throws IOException {
+    public LabyrinthServer(@NonNull final ServerConfig config) throws IOException, URISyntaxException {
         this.httpServer = HttpServer.create(new InetSocketAddress(config.getAddress(), config.getPort()), 5);
-        this.httpServer.createContext("/", exchange -> {
+        this.httpServer.createContext("/", new StaticResourcesFileHandler(this.executorService));
-            exchange.getResponseHeaders().add("Location", "/create");
-            exchange.sendResponseHeaders(302, -1);
-        });
         this.httpServer.createContext("/create", this::handleCreate);
         this.httpServer.createContext("/render", this::handleRender);
     }
@@ -94,16 +98,25 @@ public class LabyrinthServer {
     public void stop() {
         log.info("Stopping server ...");
         this.httpServer.stop(5);
+        this.executorService.shutdown();
+        try {
+            if (!this.executorService.awaitTermination(5, TimeUnit.SECONDS)) {
+                log.warn("Timeout occurred while awaiting termination of executor service");
+            }
+        } catch (final InterruptedException e) {
+            log.error("Failed to await termination of executor service", e);
+        }
         log.info("Server stopped.");
     }
 
     private void handleCreate(HttpExchange exchange) throws IOException {
+        this.executorService.submit(() -> {
             log.debug("Handling request to {}", exchange.getRequestURI());
+            try {
                 final String requestMethod = exchange.getRequestMethod();
                 if (!requestMethod.equals("GET")) {
                     exchange.getResponseBody().close();
                     exchange.sendResponseHeaders(405, -1);
-            exchange.close();
                     return;
                 }
                 final Map<RequestParameter, String> requestParams = this.parseQueryString(exchange.getRequestURI().getQuery());
@@ -118,7 +131,6 @@ public class LabyrinthServer {
                 if (needsRedirect.get()) {
                     responseHeaders.add("Location", "/create?width=" + width + "&height=" + height + "&output=" + output.toString() + "&id=" + id);
                     exchange.sendResponseHeaders(302, -1);
-            exchange.close();
                     return;
                 }
                 final Labyrinth labyrinth = new Labyrinth(width, height, id);
@@ -131,18 +143,26 @@ public class LabyrinthServer {
                     final OutputStream responseBody = exchange.getResponseBody();
                     responseBody.write(("Error: " + e).getBytes(StandardCharsets.UTF_8));
                     responseBody.flush();
-            exchange.close();
                     return;
                 }
                 responseHeaders.add("Content-type", output.getContentType());
+                if (output.equals(OutputType.BINARY)) {
+                    responseHeaders.add("Content-disposition", "attachment; filename=\"labyrinth-" + width + "x" + height + "-" + id + ".laby\"");
+                }
                 exchange.sendResponseHeaders(200, 0);
                 final OutputStream responseBody = exchange.getResponseBody();
                 responseBody.write(render);
                 responseBody.flush();
+            } catch (Exception e) {
+                log.error("FSCK!", e);
+            } finally {
                 exchange.close();
             }
+        });
+    }
 
     private void handleRender(final HttpExchange exchange) throws IOException {
+        this.executorService.submit(() -> {
             try {
                 log.debug("Handling request to {}", exchange.getRequestURI());
                 final String requestMethod = exchange.getRequestMethod();
@@ -152,15 +172,10 @@ public class LabyrinthServer {
                     return;
                 }
                 final byte[] bytes = exchange.getRequestBody().readAllBytes();
-            @NonNull final Labyrinth labyrinth;
-            try {
-                labyrinth = SerializerDeserializer.deserialize(bytes);
-            } catch (Exception e) {
-                e.printStackTrace();
-                throw e;
-            }
 
-            OutputType output = exchange.getRequestHeaders()
+                final Labyrinth labyrinth = SerializerDeserializer.deserialize(bytes);
+
+                final OutputType output = exchange.getRequestHeaders()
                         .get("Accept")
                         .contains("text/html") ?
                         OutputType.HTML :
@@ -182,9 +197,12 @@ public class LabyrinthServer {
                 final OutputStream responseBody = exchange.getResponseBody();
                 responseBody.write(render);
                 responseBody.flush();
+            } catch (Exception e) {
+                log.error("FSCK!", e);
             } finally {
                 exchange.close();
             }
+        });
     }
 
     private enum RequestParameter {

src/main/java/ch/fritteli/labyrinth/server/StaticResourcesFileHandler.java

@@ -0,0 +1,98 @@
+package ch.fritteli.labyrinth.server;
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.pdfbox.io.IOUtils;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.ExecutorService;
+
+@Slf4j
+public class StaticResourcesFileHandler implements HttpHandler {
+
+    public static final String WEBASSETS_DIRECTORY = "webassets";
+    private final ExecutorService executorService;
+
+    public StaticResourcesFileHandler(final ExecutorService executorService) {
+        this.executorService = executorService;
+    }
+
+    private static void redirect(@NonNull final HttpExchange exchange, @NonNull final String target) throws IOException {
+        log.debug("Sending redirect to {}", target);
+        exchange.getResponseHeaders().add("Location", target);
+        exchange.sendResponseHeaders(302, -1);
+    }
+
+    private static void notFound(@NonNull final HttpExchange exchange, @NonNull final String path) throws IOException {
+        log.debug("Resource '{}' not found, replying with HTTP 404", path);
+        exchange.getResponseHeaders().add("Content-type", "text/plain; charset=utf-8");
+        exchange.sendResponseHeaders(404, 0);
+        exchange.getResponseBody().write("404 - Not found".getBytes(StandardCharsets.UTF_8));
+        exchange.getResponseBody().flush();
+    }
+
+    @NonNull
+    private static byte[] getBytes(@NonNull final String path) throws IOException {
+        final InputStream stream = StaticResourcesFileHandler.class.getClassLoader().getResourceAsStream(WEBASSETS_DIRECTORY + path);
+        if (stream == null) {
+            log.debug("Resource '{}' not found in classpath.", path);
+            return new byte[0];
+        }
+        return IOUtils.toByteArray(stream);
+    }
+
+    @Nullable
+    private static String getMimeType(@NonNull final String path) {
+        if (path.endsWith(".html")) {
+            return "text/html";
+        }
+        if (path.endsWith(".css")) {
+            return "text/css";
+        }
+        return null;
+    }
+
+    @Override
+    public void handle(@NonNull final HttpExchange exchange) throws IOException {
+        this.executorService.submit(() -> {
+            try {
+                final URI requestURI = exchange.getRequestURI();
+                final String path = requestURI.getPath();
+                log.debug("Handling request to {}", path);
+                if ("/".equals(path)) {
+                    redirect(exchange, "/index.html");
+                    return;
+                }
+                if (!path.startsWith("/")) {
+                    notFound(exchange, path);
+                    return;
+                }
+                final String mimeType = getMimeType(path);
+                if (mimeType == null) {
+                    notFound(exchange, path);
+                    return;
+                }
+                final byte[] responseBytes = getBytes(path);
+                if (responseBytes.length == 0) {
+                    notFound(exchange, path);
+                    return;
+                }
+                log.debug("Serving {}{} with mimetype {}: {} bytes", WEBASSETS_DIRECTORY, path, mimeType, responseBytes.length);
+                exchange.getResponseHeaders().add("Content-type", mimeType);
+                exchange.sendResponseHeaders(200, 0);
+                exchange.getResponseBody().write(responseBytes);
+                exchange.getResponseBody().flush();
+            } catch (Exception e) {
+                log.error("FSCK!", e);
+            } finally {
+                exchange.close();
+            }
+        });
+    }
+}

src/main/resources/logback.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+	<shutdownHook class="ch.qos.logback.core.hook.DelayingShutdownHook"/>
+
+	<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+		<!-- encoders are by default assigned the type
+		ch.qos.logback.classic.encoder.PatternLayoutEncoder -->
+		<encoder>
+			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+		</encoder>
+	</appender>
+
+	<root level="info">
+		<appender-ref ref="STDOUT"/>
+	</root>
+	<logger name="ch.fritteli.labyrinth.server.StaticResourcesFileHandler" level="debug"/>
+</configuration>

src/main/resources/webassets/index.html

@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>Labyrinth Generator</title>
+    <link rel="stylesheet" href="style.css">
+</head>
+<body>
+<div class="content">
+    <h1>Labyrinth Generator</h1>
+    <p>Enter some values, click the "Create!" button and see what happens!</p>
+    <form action="/create" method="get">
+        <div class="inputs-wrapper">
+            <label for="width">Width:</label><input id="width" name="width" type="number" min="1" required>
+            <label for="height">Height:</label><input id="height" name="height" type="number" min="1" required>
+            <label for="output">Output format:</label>
+            <select id="output" name="output" required>
+                <option label="HTML Document" value="html"></option>
+                <option label="Plain text" value="text"></option>
+                <option label="PDF Document" value="pdf"></option>
+                <option label="Binary" value="binary"></option>
+            </select>
+            <label for="id">Seed (optional):</label><input id="id" name="id" type="number">
+        </div>
+        <div class="controls-wrapper">
+            <button type="submit" class="primary">Create!</button>
+            <button type="reset">Reset form</button>
+        </div>
+    </form>
+</div>
+</body>
+</html>

src/main/resources/webassets/style.css

@@ -0,0 +1,51 @@
+:root {
+    --color-background: #181a1b;
+    --color-foreground: #e8e6e3;
+    --color-border: #5d6164;
+    --color-background-highlight: #292b2c;
+    --color-foreground-highlight: #f8f7f4;
+    --color-border-highlight: #6e7275;
+}
+
+body {
+    display: flex;
+    font-family: sans-serif;
+    justify-content: center;
+}
+
+body, button, input, select {
+    background-color: var(--color-background);
+    color: var(--color-foreground);
+}
+
+button, input, select {
+    border: 1px solid var(--color-border);
+}
+
+button:active, input:active, select:active,
+button:focus, input:focus, select:focus,
+button:hover, input:hover, select:hover {
+    background-color: var(--color-background-highlight);
+    border-color: var(--color-border-highlight);
+    color: var(--color-foreground-highlight);
+}
+
+button.primary {
+    background-color: #ffcc00;
+    border-color: #eebb00;
+    color: var(--color-background);
+}
+
+.content {
+    width: 75%;
+}
+
+.content h1 {
+    text-align: center;
+}
+
+.inputs-wrapper {
+    display: grid;
+    grid-row-gap: 1em;
+    grid-template-columns: 0.5fr 1fr;
+}