1 files changed, 86 insertions, 0 deletions
diff --git a/src/core/DatabaseSourceCollection.vala b/src/core/DatabaseSourceCollection.vala
new file mode 100644
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--- /dev/null
+++ b/src/core/DatabaseSourceCollection.vala
@@ -0,0 +1,86 @@
+/* Copyright 2011-2014 Yorba Foundation
+ *
+ * This software is licensed under the GNU Lesser General Public License
+ * (version 2.1 or later).  See the COPYING file in this distribution.
+ */
+
+public delegate int64 GetSourceDatabaseKey(DataSource source);
+
+// A DatabaseSourceCollection is a SourceCollection that understands database keys (IDs) and the
+// nature that a row in a database can only be instantiated once in the system, and so it tracks
+// their existence in a map so they can be fetched by their key.
+//
+// TODO: This would be better implemented as an observer class, possibly with an interface to
+// force subclasses to provide a fetch_by_key() method.
+public abstract class DatabaseSourceCollection : SourceCollection {
+    private unowned GetSourceDatabaseKey source_key_func;
+    private Gee.HashMap<int64?, DataSource> map = new Gee.HashMap<int64?, DataSource>(int64_hash, 
+        int64_equal);
+        
+    public DatabaseSourceCollection(string name, GetSourceDatabaseKey source_key_func) {
+        base (name);
+        
+        this.source_key_func = source_key_func;
+    }
+
+    public override void notify_items_added(Gee.Iterable<DataObject> added) {
+        foreach (DataObject object in added) {
+            DataSource source = (DataSource) object;
+            int64 key = source_key_func(source);
+            
+            assert(!map.has_key(key));
+            
+            map.set(key, source);
+        }
+        
+        base.notify_items_added(added);
+    }
+    
+    public override void notify_items_removed(Gee.Iterable<DataObject> removed) {
+        foreach (DataObject object in removed) {
+            int64 key = source_key_func((DataSource) object);
+
+            bool is_removed = map.unset(key);
+            assert(is_removed);
+        }
+        
+        base.notify_items_removed(removed);
+    }
+    
+    protected DataSource fetch_by_key(int64 key) {
+        return map.get(key);
+    }
+}
+
+public class DatabaseSourceHoldingTank : SourceHoldingTank {
+    private unowned GetSourceDatabaseKey get_key;
+    private Gee.HashMap<int64?, DataSource> map = new Gee.HashMap<int64?, DataSource>(int64_hash,
+        int64_equal);
+    
+    public DatabaseSourceHoldingTank(SourceCollection sources,
+        SourceHoldingTank.CheckToKeep check_to_keep, GetSourceDatabaseKey get_key) {
+        base (sources, check_to_keep);
+        
+        this.get_key = get_key;
+    }
+    
+    public DataSource? get_by_id(int64 id) {
+        return map.get(id);
+    }
+    
+    protected override void notify_contents_altered(Gee.Collection<DataSource>? added,
+        Gee.Collection<DataSource>? removed) {
+        if (added != null) {
+            foreach (DataSource source in added)
+                map.set(get_key(source), source);
+        }
+        
+        if (removed != null) {
+            foreach (DataSource source in removed)
+                map.unset(get_key(source));
+        }
+        
+        base.notify_contents_altered(added, removed);
+    }
+}
+