Implement script hash subscriptions

Best considered experimental

Closes #124

server/controller.py

@@ -667,22 +667,29 @@ class Controller(util.LoggedClass):
     # Helpers for RPC "blockchain" command handlers
 
     def address_to_hashX(self, address):
-        if isinstance(address, str):
-            try:
-                return self.coin.address_to_hashX(address)
-            except Exception:
-                pass
+        try:
+            return self.coin.address_to_hashX(address)
+        except Exception:
+            pass
         raise RPCError('{} is not a valid address'.format(address))
 
-    def to_tx_hash(self, value):
+    def script_hash_to_hashX(self, script_hash):
+        try:
+            bin_hash = hex_str_to_hash(script_hash)
+            if len(bin_hash) == 32:
+                return bin_hash[:self.coin.HASHX_LEN]
+        except Exception:
+            pass
+        raise RPCError('{} is not a valid script hash'.format(script_hash))
+
+    def assert_tx_hash(self, value):
         '''Raise an RPCError if the value is not a valid transaction
         hash.'''
-        if isinstance(value, str) and len(value) == 64:
-            try:
-                bytes.fromhex(value)
-                return value
-            except ValueError:
-                pass
+        try:
+            if len(bytes.fromhex(value)) == 32:
+                return
+        except Exception:
+            pass
         raise RPCError('{} should be a transaction hash'.format(value))
 
     def non_negative_integer(self, value):
@@ -703,7 +710,7 @@ class Controller(util.LoggedClass):
         except DaemonError as e:
             raise RPCError('daemon error: {}'.format(e))
 
-    def new_subscription(self, address):
+    def new_subscription(self):
         if self.subs_room <= 0:
             self.subs_room = self.max_subs - self.sub_count()
             if self.subs_room <= 0:
@@ -853,7 +860,7 @@ class Controller(util.LoggedClass):
         '''
         # For some reason Electrum passes a height.  We don't require
         # it in anticipation it might be dropped in the future.
-        tx_hash = self.to_tx_hash(tx_hash)
+        self.assert_tx_hash(tx_hash)
         return await self.daemon_request('getrawtransaction', tx_hash)
 
     async def transaction_get_merkle(self, tx_hash, height):
@@ -863,7 +870,7 @@ class Controller(util.LoggedClass):
         tx_hash: the transaction hash as a hexadecimal string
         height: the height of the block it is in
         '''
-        tx_hash = self.to_tx_hash(tx_hash)
+        self.assert_tx_hash(tx_hash)
         height = self.non_negative_integer(height)
         return await self.tx_merkle(tx_hash, height)
 
@@ -876,7 +883,7 @@ class Controller(util.LoggedClass):
         # Used only for electrum client command-line requests.  We no
         # longer index by address, so need to request the raw
         # transaction.  So it works for any TXO not just UTXOs.
-        tx_hash = self.to_tx_hash(tx_hash)
+        self.assert_tx_hash(tx_hash)
         index = self.non_negative_integer(index)
         raw_tx = await self.daemon_request('getrawtransaction', tx_hash)
         if not raw_tx:

server/session.py

@@ -121,6 +121,7 @@ class ElectrumX(SessionBase):
             'blockchain.address.subscribe': self.address_subscribe,
             'blockchain.headers.subscribe': self.headers_subscribe,
             'blockchain.numblocks.subscribe': self.numblocks_subscribe,
+            'blockchain.script_hash.subscribe': self.script_hash_subscribe,
             'blockchain.transaction.broadcast': self.transaction_broadcast,
             'server.add_peer': self.add_peer,
             'server.banner': self.banner,
@@ -142,9 +143,9 @@ class ElectrumX(SessionBase):
 
         matches = touched.intersection(self.hashX_subs)
         for hashX in matches:
-            address = self.hashX_subs[hashX]
+            alias = self.hashX_subs[hashX]
             status = await self.address_status(hashX)
-            changed.append((address, status))
+            changed.append((alias, status))
 
         if height != self.notified_height:
             self.notified_height = height
@@ -161,11 +162,15 @@ class ElectrumX(SessionBase):
                 old_status = self.mempool_statuses[hashX]
                 status = await self.address_status(hashX)
                 if status != old_status:
-                    address = self.hashX_subs[hashX]
-                    changed.append((address, status))
+                    alias = self.hashX_subs[hashX]
+                    changed.append((alias, status))
 
-        for address_status in changed:
-            pairs.append(('blockchain.address.subscribe', address_status))
+        for alias_status in changed:
+            if len(alias_status[0]) == 64:
+                method = 'blockchain.script_hash.subscribe'
+            else:
+                method = 'blockchain.address.subscribe'
+            pairs.append((method, alias_status))
 
         if pairs:
             self.send_notifications(pairs)
@@ -232,22 +237,31 @@ class ElectrumX(SessionBase):
 
         return status
 
-    async def address_subscribe(self, address):
-        '''Subscribe to an address.
-
-        address: the address to subscribe to'''
+    async def hashX_subscribe(self, hashX, alias):
         # First check our limit.
         if len(self.hashX_subs) >= self.max_subs:
             raise RPCError('your address subscription limit {:,d} reached'
                            .format(self.max_subs))
 
         # Now let the controller check its limit
-        self.controller.new_subscription(address)
-
-        hashX = self.env.coin.address_to_hashX(address)
-        self.hashX_subs[hashX] = address
+        self.controller.new_subscription()
+        self.hashX_subs[hashX] = alias
         return await self.address_status(hashX)
 
+    async def address_subscribe(self, address):
+        '''Subscribe to an address.
+
+        address: the address to subscribe to'''
+        hashX = self.controller.address_to_hashX(address)
+        return await self.hashX_subscribe(hashX, address)
+
+    async def script_hash_subscribe(self, script_hash):
+        '''Subscribe to a script hash.
+
+        script_hash: the SHA256 hash of the script to subscribe to'''
+        hashX = self.controller.script_hash_to_hashX(script_hash)
+        return await self.hashX_subscribe(hashX, script_hash)
+
     def server_features(self):
         '''Returns a dictionary of server features.'''
         return self.controller.peer_mgr.myself.features