Added more complex indexing and search query.

README.md

@@ -5,3 +5,12 @@ An indexer and search API for D programming language packages as registered on h
 ## Setup
 
 To set up and run the program, all you need is Java version 21 or higher, and then run the project using your favorite IDE. It will boot up a web server that you can use to search for packages at http://localhost:8080/search?query=test, replacing `query=test` with what you want to search for.
+
+## Architecture
+
+The basic architecture of this searcher is that of your classic indexed search engine, which is usually comprised of the following steps:
+1. Fetch raw data from somewhere.
+2. Generate an index from that data.
+3. Search for relevant data using the index.
+
+In this application, steps 1 and 2 are done periodically in a separate thread, to ensure that the data stays relatively fresh. Step 3 is done whenever a request to the `/search` endpoint is received.

src/main/java/com/andrewlalis/d_package_search/DPackageSearch.java

@@ -28,7 +28,7 @@ public class DPackageSearch {
 			while (true) {
 				indexGenerator.run();
 				try {
-					Thread.sleep(Duration.ofMinutes(1));
+					Thread.sleep(Duration.ofMinutes(5));
 				} catch (InterruptedException e) {
 					System.err.println("Indexing thread interrupted: " + e.getMessage());
 					break;

src/main/java/com/andrewlalis/d_package_search/PackageInfo.java

@@ -7,11 +7,15 @@ import java.time.LocalDateTime;
  * @param name The name of the package.
  * @param categories The list of categories the package is in.
  * @param versions The known list of versions for this package.
+ * @param fetchedAt Timestamp for when this package was fetched exactly, so
+ *                  that later indexing can use a unified timestamp for reference.
  */
 public record PackageInfo(
         String name,
         String[] categories,
-        VersionInfo[] versions
+        VersionInfo[] versions,
+        long totalDownloads,
+        LocalDateTime fetchedAt
 ) {
     /**
      * Information about a specific version of a D package.

src/main/java/com/andrewlalis/d_package_search/WebApiRunner.java

@@ -79,7 +79,7 @@ public final class WebApiRunner extends Handler.Abstract implements Runnable {
             if (idx != -1) {
                 String key = pair.substring(0, idx);
                 if (key.trim().equalsIgnoreCase("query")) {
-                    return pair.substring(idx + 1).trim().toUpperCase();
+                    return pair.substring(idx + 1).trim().toLowerCase();
                 }
             }
         }

src/main/java/com/andrewlalis/d_package_search/impl/DubRegistryPackageFetcher.java

@@ -43,6 +43,7 @@ public class DubRegistryPackageFetcher implements PackageFetcher {
 			if (response.statusCode() != 200) {
 				throw new IOException("Response status code " + response.statusCode());
 			}
+			LocalDateTime fetchedAt = LocalDateTime.now(ZoneOffset.UTC);
 			ObjectMapper mapper = new ObjectMapper();
 			try (var in = new GZIPInputStream(response.body())) {
 				ArrayNode array = mapper.readValue(in, ArrayNode.class);
@@ -50,7 +51,7 @@ public class DubRegistryPackageFetcher implements PackageFetcher {
 				for (JsonNode node : array) {
 					if (node.isObject()) {
 						try {
-							packages.add(parsePackage((ObjectNode) node));
+							packages.add(parsePackage((ObjectNode) node, fetchedAt));
 						} catch (Exception e) {
 							e.printStackTrace();
 						}
@@ -63,11 +64,13 @@ public class DubRegistryPackageFetcher implements PackageFetcher {
 		}
 	}
 
-	private PackageInfo parsePackage(ObjectNode obj) {
+	private PackageInfo parsePackage(ObjectNode obj, LocalDateTime fetchedAt) {
 		return new PackageInfo(
 				obj.get("name").asText(),
 				mapJsonArray(obj.withArray("categories"), JsonNode::asText).toArray(new String[0]),
-				mapJsonArray(obj.withArray("versions"), this::parseVersion).toArray(new PackageInfo.VersionInfo[0])
+				mapJsonArray(obj.withArray("versions"), this::parseVersion).toArray(new PackageInfo.VersionInfo[0]),
+				obj.get("stats").get("downloads").get("total").asLong(),
+				fetchedAt
 		);
 	}
 
@@ -97,6 +100,13 @@ public class DubRegistryPackageFetcher implements PackageFetcher {
 		);
 	}
 
+	/**
+	 * Maps a JSON array to a list of objects, using a mapping function.
+	 * @param array The JSON array.
+	 * @param mapper The mapper function to apply to each element of the array.
+	 * @return The mapped list of objects.
+	 * @param <T> The type of the resultant list elements.
+	 */
 	private static <T> List<T> mapJsonArray(ArrayNode array, Function<JsonNode, T> mapper) {
 		List<T> list = new ArrayList<>(array.size());
 		for (JsonNode node : array) {

src/main/java/com/andrewlalis/d_package_search/impl/LucenePackageIndexer.java

@@ -4,18 +4,23 @@ import com.andrewlalis.d_package_search.PackageIndexer;
 import com.andrewlalis.d_package_search.PackageInfo;
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.analysis.standard.StandardAnalyzer;
-import org.apache.lucene.document.Document;
-import org.apache.lucene.document.Field;
-import org.apache.lucene.document.StoredField;
-import org.apache.lucene.document.TextField;
+import org.apache.lucene.document.*;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.IndexableFieldType;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
 
 import java.io.IOException;
 import java.nio.file.Path;
+import java.time.Duration;
+import java.time.ZoneOffset;
+import java.util.*;
 
+/**
+ * An indexer that produces a Lucene index, which is a directory, composed of
+ * possibly many index segments.
+ */
 public class LucenePackageIndexer implements PackageIndexer {
 	private final IndexWriter indexWriter;
 	private final Directory dir;
@@ -30,13 +35,70 @@ public class LucenePackageIndexer implements PackageIndexer {
 		this.indexWriter = new IndexWriter(dir, config);
 	}
 
+	/**
+	 * Adds a package to the Lucene index. This is the central place where the
+	 * index's fields are defined. We define the following fields:
+	 * <ul>
+	 *     <li>name (text, stored)</li>
+	 *     <li>url (stored only)</li>
+	 *     <li>categories (multivalued string field with value for each category).</li>
+	 *     <li>latestVersionTimestamp (string field with date of latest version).</li>
+	 *     <li>description (optional text field)</li>
+	 *     <li>license (optional string field)</li>
+	 *     <li>readme (optional text field)</li>
+	 *     <li>
+	 *         features (feature field with the following features useful for scoring)
+	 *         <ul>
+	 *             <li>recency (0 - 1 value indicating how recent the package is)</li>
+	 *             <li>downloads (total downloads for the package)</li>
+	 *         </ul>
+	 *     </li>
+	 * </ul>
+	 * @param info The package to index.
+	 * @throws IOException If an error occurs.
+	 */
 	@Override
 	public void addToIndex(PackageInfo info) throws IOException {
+		if (info.versions().length == 0) {
+			System.out.println("Skipping package \"" + info.name() + "\" because there are no versions available.");
+			return;
+		}
+		System.out.println("Indexing package \"" + info.name() + "\".");
 		String dubUrl = "https://code.dlang.org/packages/" + info.name();
+		List<PackageInfo.VersionInfo> allVersions = new ArrayList<>(Arrays.asList(info.versions()));
+		allVersions.sort(Comparator.comparing(PackageInfo.VersionInfo::timestamp).reversed());
+		var recentVersions = allVersions.subList(0, Math.min(5, allVersions.size()));
 
 		Document doc = new Document();
 		doc.add(new TextField("name", info.name(), Field.Store.YES));
 		doc.add(new StoredField("url", dubUrl));
+		for (String category : info.categories()) {
+			doc.add(new StringField("categories", category, Field.Store.NO));
+		}
+
+		PackageInfo.VersionInfo latestVersion = recentVersions.getFirst();
+		doc.add(new StringField(
+				"latestVersionTimestamp",
+				DateTools.dateToString(Date.from(latestVersion.timestamp().toInstant(ZoneOffset.UTC)), DateTools.Resolution.SECOND),
+				Field.Store.NO
+		));
+		if (latestVersion.description() != null) {
+			doc.add(new TextField("description", latestVersion.description(), Field.Store.NO));
+		}
+		if (latestVersion.license() != null) {
+			doc.add(new StringField("license", latestVersion.license(), Field.Store.NO));
+		}
+		if (latestVersion.readmeText() != null) {
+			doc.add(new TextField("readme", latestVersion.readmeText(), Field.Store.NO));
+		}
+
+		// Add FeatureFields to score packages based on some metrics.
+		int daysSinceUpdate = Math.clamp(Duration.between(latestVersion.timestamp(), info.fetchedAt()).toDays(), 1, 365 * 3);
+		float recency = 1f / daysSinceUpdate;
+		float downloadsScore = Math.clamp(info.totalDownloads(), 0.001f, Float.MAX_VALUE);
+		doc.add(new FeatureField("features", "recency", recency));
+		doc.add(new FeatureField("features", "downloads", downloadsScore));
+
 		indexWriter.addDocument(doc);
 	}
 

src/main/java/com/andrewlalis/d_package_search/impl/LucenePackageSearcher.java

@@ -3,6 +3,7 @@ package com.andrewlalis.d_package_search.impl;
 import com.andrewlalis.d_package_search.PackageSearchResult;
 import com.andrewlalis.d_package_search.PackageSearcher;
 import org.apache.lucene.document.Document;
+import org.apache.lucene.document.FeatureField;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.*;
@@ -11,12 +12,13 @@ import org.apache.lucene.store.FSDirectory;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.SequencedCollection;
+import java.util.*;
 import java.util.concurrent.Executors;
 
+/**
+ * A package searcher implementation that uses a weighted wildcard query to
+ * search a Lucene index.
+ */
 public class LucenePackageSearcher implements PackageSearcher {
     private final Path indexPath;
 
@@ -52,12 +54,28 @@ public class LucenePackageSearcher implements PackageSearcher {
     private Query buildQuery(String queryText) {
         BooleanQuery.Builder queryBuilder = new BooleanQuery.Builder();
         String[] searchTerms = queryText.toLowerCase().split("\\s+");
-        for (String searchTerm : searchTerms) {
-            String wildcardTerm = searchTerm + "*";
-            Query basicQuery = new WildcardQuery(new Term("name", wildcardTerm));
-            queryBuilder.add(new BoostQuery(basicQuery, 1f), BooleanClause.Occur.SHOULD);
+
+        Map<String, Float> weightedFields = Map.of(
+                "name", 1f,
+                "description", 0.5f,
+                "readme", 0.25f
+        );
+
+        for (int i = 0; i < Math.min(5, searchTerms.length); i++) {
+            for (var entry : weightedFields.entrySet()) {
+                String fieldName = entry.getKey();
+                float fieldWeight = entry.getValue();
+                Query termQuery = new BoostQuery(new PrefixQuery(new Term(fieldName, searchTerms[i])), fieldWeight);
+                queryBuilder.add(termQuery, BooleanClause.Occur.SHOULD);
+            }
         }
-        return queryBuilder.build();
+        Query baseQuery = queryBuilder.build();
+        Query boostedQuery = new BooleanQuery.Builder()
+                .add(baseQuery, BooleanClause.Occur.MUST)
+                .add(FeatureField.newSaturationQuery("features", "recency"), BooleanClause.Occur.SHOULD)
+                .add(FeatureField.newSaturationQuery("features", "downloads"), BooleanClause.Occur.SHOULD)
+                .build();
+        return boostedQuery;
     }
 
     private PackageSearchResult prepareResult(Document doc) {