From cd924f6efbb40993eb12ed2c6e6547d8b505d439 Mon Sep 17 00:00:00 2001
From: Matthias Andreas Benkard <code@mail.matthias.benkard.de>
Date: Tue, 28 Dec 2021 00:46:06 +0100
Subject: Add Decoder#ofDictionaryEntry.

Change-Id: Ie78096e1a7cfd3bcfa446e3ababe15b910d0c23c
---
 .../main/java/eu/mulk/jgvariant/core/Decoder.java  | 42 ++++++++++++++++++++++
 .../java/eu/mulk/jgvariant/core/Signature.java     | 12 ++++++-
 .../main/java/eu/mulk/jgvariant/core/Variant.java  |  1 +
 3 files changed, 54 insertions(+), 1 deletion(-)

(limited to 'jgvariant-core/src/main/java/eu')

diff --git a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Decoder.java b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Decoder.java
index fee0407..96e1332 100644
--- a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Decoder.java
+++ b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Decoder.java
@@ -8,9 +8,11 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.charset.Charset;
 import java.text.ParseException;
+import java.util.AbstractMap.SimpleImmutableEntry;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.function.Function;
 import org.apiguardian.api.API;
@@ -154,6 +156,19 @@ public abstract class Decoder<T> {
     return new TupleDecoder(componentDecoders);
   }
 
+  /**
+   * Creates a {@link Decoder} for a {@code Dictionary Entry} type, decoding into a {@link
+   * Map.Entry}.
+   *
+   * @param keyDecoder a {@link Decoder} for the key component of the dictionary entry.
+   * @param valueDecoder a {@link Decoder} for the value component of the dictionary entry.
+   * @return a new {@link Decoder}.
+   */
+  public static <K, V> Decoder<Map.Entry<K, V>> ofDictionaryEntry(
+      Decoder<K> keyDecoder, Decoder<V> valueDecoder) {
+    return new DictionaryEntryDecoder<>(keyDecoder, valueDecoder);
+  }
+
   /**
    * Creates a {@link Decoder} for the {@link Variant} type.
    *
@@ -169,6 +184,7 @@ public abstract class Decoder<T> {
    *   <li>{@link Optional} (a GVariant {@code Maybe} type)
    *   <li>{@link List} (a GVariant array)
    *   <li>{@code Object[]} (a GVariant structure)
+   *   <li>{@link java.util.Map.Entry} (a dictionary entry)
    *   <li>{@link Variant} (a nested variant)
    * </ul>
    *
@@ -515,6 +531,32 @@ public abstract class Decoder<T> {
     }
   }
 
+  private static class DictionaryEntryDecoder<K, V> extends Decoder<Map.Entry<K, V>> {
+
+    private final TupleDecoder tupleDecoder;
+
+    DictionaryEntryDecoder(Decoder<K> keyDecoder, Decoder<V> valueDecoder) {
+      this.tupleDecoder = new TupleDecoder(keyDecoder, valueDecoder);
+    }
+
+    @Override
+    public byte alignment() {
+      return tupleDecoder.alignment();
+    }
+
+    @Override
+    public Integer fixedSize() {
+      return tupleDecoder.fixedSize();
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public Map.Entry<K, V> decode(ByteBuffer byteSlice) {
+      Object[] components = tupleDecoder.decode(byteSlice);
+      return new SimpleImmutableEntry<>((K) components[0], (V) components[1]);
+    }
+  }
+
   private static class VariantDecoder extends Decoder<Variant> {
 
     @Override
diff --git a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Signature.java b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Signature.java
index 78e4bdd..6a4d01d 100644
--- a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Signature.java
+++ b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Signature.java
@@ -92,7 +92,17 @@ public final class Signature {
       case 'v' -> Decoder.ofVariant();
       case 'm' -> Decoder.ofMaybe(parseSignature(signature));
       case 'a' -> Decoder.ofArray(parseSignature(signature));
-      case '(', '{' -> Decoder.ofStructure(parseTupleTypes(signature).toArray(new Decoder<?>[0]));
+      case '(' -> Decoder.ofStructure(parseTupleTypes(signature).toArray(new Decoder<?>[0]));
+      case '{' -> {
+        var tupleTypes = parseTupleTypes(signature);
+        if (tupleTypes.size() != 2) {
+          throw new ParseException(
+              String.format(
+                  "dictionary entry type with %d components, expected 2", tupleTypes.size()),
+              signature.position());
+        }
+        yield Decoder.ofDictionaryEntry(tupleTypes.get(0), tupleTypes.get(1));
+      }
       default -> throw new ParseException(
           String.format("encountered unknown signature byte '%c'", c), signature.position());
     };
diff --git a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Variant.java b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Variant.java
index d1c1049..34d3945 100644
--- a/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Variant.java
+++ b/jgvariant-core/src/main/java/eu/mulk/jgvariant/core/Variant.java
@@ -18,6 +18,7 @@ import org.apiguardian.api.API.Status;
  *   <li>{@link java.util.Optional} (a GVariant {@code Maybe} type)
  *   <li>{@link java.util.List} (a GVariant array)
  *   <li>{@code Object[]} (a GVariant structure)
+ *   <li>{@link java.util.Map.Entry} (a dictionary entry)
  *   <li>{@link Variant} (a nested variant)
  * </ul>
  *
-- 
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