feat: implemented abstraction logic

1 files changed, 73 insertions, 0 deletions

diff --git a/src/main/java/ftbsc/lll/mapper/MapperProvider.java b/src/main/java/ftbsc/lll/mapper/MapperProvider.java
new file mode 100644
index 0000000..819e792
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/MapperProvider.java
@@ -0,0 +1,73 @@
+package ftbsc.lll.mapper;
+
+import ftbsc.lll.exceptions.InvalidResourceException;
+
+import java.io.*;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * The main class of the mapper library. It loads all the
+ * valid {@link IMapper}s and gets information from them.
+ */
+public class MapperProvider {
+	private static MapperProvider INSTANCE = null;
+
+	private static MapperProvider getInstance() {
+		return INSTANCE == null ? (INSTANCE = new MapperProvider()) : INSTANCE;
+	}
+
+	private Set<IMapper> loadedMappers = null;
+
+	private void loadMappers() {
+		this.loadedMappers = new HashSet<>();
+		for(IMapper mapper: ServiceLoader.load(IMapper.class))
+			this.loadedMappers.add(mapper);
+		if(this.loadedMappers.isEmpty())
+			throw new RuntimeException("Something went wrong: no mapper types were loaded successfully!");
+	}
+
+	/**
+	 * Loads all valid parsers available in the classpath (via the Java Service API),
+	 * attempts to load the resource at given location and to populate a mapper with
+	 * its data.
+	 * @param data the file as a list of strings
+	 * @return a {@link IMapper} (populating it is left to the user)
+	 */
+	public static IMapper getMapper(List<String> data) {
+		if(getInstance().loadedMappers == null)
+			getInstance().loadMappers();
+		return getInstance().loadedMappers.stream()
+			.filter(m -> m.claim(data))
+			.max(Comparator.comparingInt(IMapper::priority))
+			.orElseThrow(InvalidResourceException::new);
+	}
+
+	/**
+	 * Gets a resource and parses it into a {@link List} of {@link String}s.
+	 * @param location either a URL or a local path
+	 * @return a {@link List} containing the lines of the resource
+	 * @throws InvalidResourceException if provided an invalid resource
+	 */
+	public static List<String> fetchFromLocalOrRemote(String location) {
+		InputStream targetStream;
+		try {
+			URI target = new URI(location);
+			targetStream = target.toURL().openStream();
+		} catch(URISyntaxException | IOException e) {
+			//may be a local file path
+			File f = new File(location);
+			try {
+				targetStream = new FileInputStream(f);
+			} catch(FileNotFoundException ex) {
+				throw new InvalidResourceException(location);
+			}
+		}
+
+		return new BufferedReader(new InputStreamReader(targetStream,
+			StandardCharsets.UTF_8)).lines().collect(Collectors.toList());
+	}
+}