under construction

linkback/README.md

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+# Linkback

linkback/build.gradle.kts

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+plugins {
+    id("elex-springboot")
+    id("org.springframework.boot") version "2.5.3"
+    id("io.spring.dependency-management") version "1.0.11.RELEASE"
+}
+
+version = "1.0.0"
+description = "Linkback"
+
+tasks.bootJar{
+    enabled = false
+}
+tasks.jar {
+    enabled = true
+}
+
+dependencies {
+    // https://mvnrepository.com/artifact/org.jsoup/jsoup
+    implementation("org.jsoup:jsoup:1.14.2")
+
+    // https://mvnrepository.com/artifact/com.fasterxml.jackson.dataformat/jackson-dataformat-xml
+    implementation("com.fasterxml.jackson.dataformat:jackson-dataformat-xml")
+    // https://mvnrepository.com/artifact/com.github.spullara.mustache.java/compiler
+    //implementation("com.github.spullara.mustache.java:compiler:0.9.7")
+
+    implementation("org.springframework.boot:spring-boot-starter")
+    //implementation("org.springframework.boot:spring-boot-starter-mustache")
+
+    compileOnly("org.projectlombok:lombok")
+    //runtimeOnly("org.mariadb.jdbc:mariadb-java-client")
+
+    annotationProcessor("org.projectlombok:lombok")
+
+    testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

linkback/src/main/java/com/elex_project/asgard/linkback/Backlink.java

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+package com.elex_project.asgard.linkback;
+
+import lombok.Data;
+
+import java.net.URI;
+
+@Data
+public class Backlink {
+	private URI source, target;
+	private String title;
+	private String excerpt;
+}

linkback/src/main/java/com/elex_project/asgard/linkback/Linkback.java

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+package com.elex_project.asgard.linkback;
+
+import lombok.extern.slf4j.Slf4j;
+import org.jetbrains.annotations.NotNull;
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
+import org.jsoup.select.Elements;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.concurrent.Executors;
+
+@Slf4j
+public class Linkback {
+	private static final String UA = "Asgard linkback crawler by Elex (https://www.elex-project.com/)";
+	private static final HttpClient httpClient;
+
+	static {
+		httpClient = HttpClient.newBuilder()
+				.executor(Executors.newSingleThreadExecutor())
+				.version(HttpClient.Version.HTTP_2)
+				.connectTimeout(Duration.ofSeconds(10))
+				.followRedirects(HttpClient.Redirect.NORMAL)
+				.build();
+	}
+
+	private final URI source, target;
+
+	public Linkback(final @NotNull URI source, final @NotNull URI target) {
+		this.source = source;
+		this.target = target;
+	}
+
+	public void process(final @NotNull LinkbackListener listener) {
+		if (source.equals(target)) {
+			listener.onError(new Exception(""));//todo
+			return;
+		}
+
+		httpClient.sendAsync(HttpRequest.newBuilder(source)
+						.GET()
+						.header("User-Agent", UA)
+						.timeout(Duration.ofSeconds(10))
+						.build(),
+				HttpResponse.BodyHandlers.ofString())
+				.exceptionally(ex -> {
+					listener.onError(ex);
+					return null;
+				})
+				.thenAccept(resp -> {
+					final Backlink result = new Backlink();
+					result.setSource(source);
+					result.setTarget(target);
+
+					try {
+						final Document document = Jsoup.parse(resp.body());
+
+						result.setTitle(document.title());
+
+						final Element descElement = document.selectFirst("meta[name='description']");
+						if (null == descElement) {
+							final String text = document.wholeText();
+							result.setExcerpt(text.substring(0, Math.min(text.length(), 200)));
+						} else {
+							result.setExcerpt(descElement.attr("value"));
+						}
+
+						final Elements links = document.select("a[href^='" + target.toString() + "']");
+						if (links.size() > 0) {
+							listener.onResult(result);
+						} else {
+							listener.onError(new Exception("No link found."));
+						}
+						// todo
+
+					} catch (Throwable e) {
+						listener.onError(e);
+					}
+				});
+	}
+
+	private void crawl(String document){
+
+	}
+}

linkback/src/main/java/com/elex_project/asgard/linkback/LinkbackListener.java

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+package com.elex_project.asgard.linkback;
+
+public interface LinkbackListener {
+	public void onResult(final Backlink backlink);
+	public void onError(final Throwable e);
+}

linkback/src/main/java/com/elex_project/asgard/linkback/package-info.java

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+package com.elex_project.asgard.linkback;

linkback/src/test/java/com/elex_project/asgard/linkback/LinkbackTest.java

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+/*
+ * Project Asgard
+ *
+ * Copyright (c) 2021. Elex. All Rights Reserved.
+ * https://www.elex-project.com/
+ */
+
+package com.elex_project.asgard.linkback;
+
+import org.junit.jupiter.api.Test;
+
+import java.net.URI;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class LinkbackTest {
+
+	@Test
+	void uriTest(){
+		URI a = URI.create("http://example.com/a").normalize();
+		URI b = URI.create("http://example.com/a/").normalize();
+
+		Path pa = Path.of(a.getPath());
+		Path pb = Path.of(b.getPath());
+		System.out.println(pa.equals(pb));
+	}
+}