Extract shared prefix matching helper

src/mudlib/commands/__init__.py

@@ -63,6 +63,42 @@ def register(defn: CommandDefinition) -> None:
         _registry[alias] = defn
 
 
+def resolve_prefix(command: str) -> CommandDefinition | list[str] | None:
+    """Resolve a command by exact match or shortest unique prefix.
+
+    Args:
+        command: Command name or prefix to resolve
+
+    Returns:
+        CommandDefinition if unique match found
+        list of command names if ambiguous
+        None if no match
+    """
+    # Try exact match first (fast path)
+    defn = _registry.get(command)
+    if defn is not None:
+        return defn
+
+    # Try prefix matching
+    prefix_matches = [key for key in _registry if key.startswith(command)]
+
+    # Deduplicate by CommandDefinition identity
+    unique_defns = {}
+    for key in prefix_matches:
+        defn_obj = _registry[key]
+        unique_defns[id(defn_obj)] = defn_obj
+
+    if len(unique_defns) == 0:
+        # No matches
+        return None
+    elif len(unique_defns) == 1:
+        # Unique match
+        return next(iter(unique_defns.values()))
+    else:
+        # Multiple matches - return list of names
+        return sorted([d.name for d in unique_defns.values()])
+
+
 async def dispatch(player: Player, raw_input: str) -> None:
     """Parse input, find command, call handler.
 
@@ -80,30 +116,17 @@ async def dispatch(player: Player, raw_input: str) -> None:
     command = parts[0].lower()
     args = parts[1] if len(parts) > 1 else ""
 
-    # Look up the definition - exact match first (fast path)
-    defn = _registry.get(command)
+    # Resolve command by exact match or prefix
+    result = resolve_prefix(command)
 
-    if defn is None:
-        # Try prefix matching
-        prefix_matches = [key for key in _registry if key.startswith(command)]
-
-        # Deduplicate by CommandDefinition identity
-        unique_defns = {}
-        for key in prefix_matches:
-            defn_obj = _registry[key]
-            unique_defns[id(defn_obj)] = defn_obj
-
-        if len(unique_defns) == 0:
+    if result is None:
         # No matches
         player.writer.write(f"Unknown command: {command}\r\n")
         await player.writer.drain()
         return
-        elif len(unique_defns) == 1:
-            # Unique match
-            defn = next(iter(unique_defns.values()))
-        else:
+    elif isinstance(result, list):
         # Multiple matches - show disambiguation
-            names = sorted([d.name for d in unique_defns.values()])
+        names = result
         if len(names) == 2:
             msg = f"{names[0]} or {names[1]}?\r\n"
         else:
@@ -111,6 +134,9 @@ async def dispatch(player: Player, raw_input: str) -> None:
         player.writer.write(msg)
         await player.writer.drain()
         return
+    else:
+        # Unique match
+        defn = result
 
     # Check mode restriction
     if defn.mode != "*" and defn.mode != player.mode:

src/mudlib/commands/help.py

@@ -2,7 +2,7 @@
 
 from typing import TYPE_CHECKING
 
-from mudlib.commands import CommandDefinition, _registry, register
+from mudlib.commands import CommandDefinition, _registry, register, resolve_prefix
 from mudlib.commands.movement import DIRECTIONS
 from mudlib.player import Player
 
@@ -19,31 +19,20 @@ async def _show_command_detail(player: Player, command_name: str) -> None:
     """
     from mudlib.combat.commands import combat_moves
 
-    # Look up the command in registry - exact match first
-    defn = _registry.get(command_name)
+    # Resolve command by exact match or prefix
+    result = resolve_prefix(command_name)
 
-    # If not found, try prefix matching
-    if defn is None:
-        prefix_matches = [key for key in _registry if key.startswith(command_name)]
-
-        # Deduplicate by CommandDefinition identity
-        unique_defns = {}
-        for key in prefix_matches:
-            defn_obj = _registry[key]
-            unique_defns[id(defn_obj)] = defn_obj
-
-        if len(unique_defns) == 1:
-            # Unique match via prefix
-            defn = next(iter(unique_defns.values()))
-        elif len(unique_defns) > 1:
+    if isinstance(result, list):
         # Multiple matches - show disambiguation
-            names = sorted([d.name for d in unique_defns.values()])
+        names = result
         if len(names) == 2:
             msg = f"{names[0]} or {names[1]}?\r\n"
         else:
             msg = f"{', '.join(names[:-1])}, or {names[-1]}?\r\n"
         await player.send(msg)
         return
+    else:
+        defn = result
 
     # If still not in registry, check if it's a combat move name (like "punch left")
     if defn is None: