Add toUri/fromUri methods to OpenPgpV4Fingerprint

pgpainless-core/src/main/java/org/pgpainless/key/OpenPgpV4Fingerprint.java

@@ -15,6 +15,8 @@
  */
 package org.pgpainless.key;
 
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.nio.Buffer;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
@@ -31,6 +33,8 @@ import org.bouncycastle.util.encoders.Hex;
  */
 public class OpenPgpV4Fingerprint implements CharSequence, Comparable<OpenPgpV4Fingerprint> {
 
+    public static final String SCHEME = "openpgp4fpr";
+
     private static final Charset utf8 = Charset.forName("UTF-8");
     private final String fingerprint;
 
@@ -138,6 +142,21 @@ public class OpenPgpV4Fingerprint implements CharSequence, Comparable<OpenPgpV4F
         return fingerprint;
     }
 
+    public URI toUri() {
+        try {
+            return new URI(SCHEME, toString(), null);
+        } catch (URISyntaxException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    public static OpenPgpV4Fingerprint fromUri(URI uri) {
+        if (!SCHEME.equals(uri.getScheme())) {
+            throw new IllegalArgumentException("URI scheme MUST equal '" + SCHEME + "'");
+        }
+        return new OpenPgpV4Fingerprint(uri.getSchemeSpecificPart());
+    }
+
     @Override
     public int compareTo(@Nonnull OpenPgpV4Fingerprint openPgpV4Fingerprint) {
         return fingerprint.compareTo(openPgpV4Fingerprint.fingerprint);

pgpainless-core/src/test/java/org/pgpainless/key/OpenPgpV4FingerprintTest.java

@@ -19,6 +19,8 @@ import static junit.framework.TestCase.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 
 import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
 
 import org.bouncycastle.openpgp.PGPPublicKey;
 import org.junit.Test;
@@ -74,4 +76,21 @@ public class OpenPgpV4FingerprintTest {
         OpenPgpV4Fingerprint fingerprint = new OpenPgpV4Fingerprint(key);
         assertEquals(keyId, fingerprint.getKeyId());
     }
+
+    @Test
+    public void testToUri() {
+        OpenPgpV4Fingerprint fingerprint = new OpenPgpV4Fingerprint("5448452043414B452049532041204C4945212121");
+
+        URI uri = fingerprint.toUri();
+        assertEquals("openpgp4fpr:5448452043414B452049532041204C4945212121", uri.toString());
+
+        OpenPgpV4Fingerprint parsed = OpenPgpV4Fingerprint.fromUri(uri);
+        assertEquals(fingerprint, parsed);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testFromUriThrowsIfWrongScheme() throws URISyntaxException {
+        URI uri = new URI(null, "5448452043414B452049532041204C4945212121", null);
+        OpenPgpV4Fingerprint.fromUri(uri);
+    }
 }