check for double-spends in txdb.

lib/bcoin/txdb.js

@@ -237,8 +237,6 @@ TXPool.prototype._add = function add(tx, callback, force) {
           return next();
         }
 
-        // TODO: Check for double-spend by doing self.getTX(input.prevout.hash)
-
         // Only add orphans if this input is ours.
         self._hasAddress(input.getAddress(), function(err, result) {
           if (err)
@@ -247,31 +245,40 @@ TXPool.prototype._add = function add(tx, callback, force) {
           if (!result)
             return next();
 
-          // Add orphan, if no parent transaction is yet known
+          self.getTX(input.prevout.hash, function(err, result) {
-          self.db.get(p + 'o/' + key, function(err, orphans) {
+            if (err)
-            if (err && err.type !== 'NotFoundError')
               return done(err);
 
-            if (orphans) {
+            // Are we double-spending?
-              try {
+            if (result)
-                orphans = JSON.parse(orphans.toString('utf8'));
+              return done(new Error('Transaction is double-spending.'));
-              } catch (e) {
+
-                return done(e);
+            // Add orphan, if no parent transaction is yet known
+            self.db.get(p + 'o/' + key, function(err, orphans) {
+              if (err && err.type !== 'NotFoundError')
+                return done(err);
+
+              if (orphans) {
+                try {
+                  orphans = JSON.parse(orphans.toString('utf8'));
+                } catch (e) {
+                  return done(e);
+                }
+              } else {
+                orphans = [];
               }
-            } else {
-              orphans = [];
-            }
 
-            orphans.push({
+              orphans.push({
-              tx: tx.toExtended(true).toString('hex'),
+                tx: tx.toExtended(true).toString('hex'),
-              index: i
+                index: i
+              });
+
+              orphans = new Buffer(JSON.stringify(orphans), 'utf8');
+
+              batch.put(p + 'o/' + key, orphans);
+
+              return next();
             });
-
-            orphans = new Buffer(JSON.stringify(orphans), 'utf8');
-
-            batch.put(p + 'o/' + key, orphans);
-
-            return next();
           });
         });
       });