feat(repl): add auto-completer

src/completer/completer.py

@@ -0,0 +1,38 @@
+from typing import Optional
+
+from src.interpreter.environment import Environment
+from src.interpreter.interpreter import Interpreter
+
+
+class Completer:
+    def __init__(self, interpreter: Interpreter):
+        self.interpreter: Interpreter = interpreter
+        self.options: list[str] = []
+        self.matches: list[str] = []
+
+    def complete(self, text: str, state: int) -> Optional[str]:
+        if state == 0:
+            self.update_matches(text)
+        try:
+            return self.matches[state]
+        except IndexError:
+            return None
+
+    def update_matches(self, text: str):
+        self.options = []
+
+        env: Optional[Environment] = self.interpreter.env
+        while env is not None:
+            self.options.extend(env.values.keys())
+            env = env.enclosing
+
+        self.options = sorted(self.options)
+
+        if not text:
+            self.matches = self.options
+        else:
+            self.matches = [
+                opt
+                for opt in self.options
+                if opt.startswith(text)
+            ]

src/repl.py

@@ -3,6 +3,7 @@ import readline
 from pathlib import Path
 
 from src.ast.stmt import Stmt
+from src.completer.completer import Completer
 from src.interpreter.interpreter import Interpreter
 from src.interpreter.resolver import Resolver
 from src.parser.parser import Parser
@@ -16,6 +17,8 @@ class REPL:
 
     def __init__(self):
         self.interpreter: Interpreter = Interpreter()
+        self.completer: Completer = Completer(self.interpreter)
+        self.buf: str = ""
 
     @staticmethod
     def greet():
@@ -38,6 +41,10 @@ class REPL:
 
         atexit.register(save, h_len, self.HIST_FILE)
 
+    def init_completer(self):
+        readline.set_completer(self.completer.complete)
+        readline.parse_and_bind("tab: complete")
+
     def run(self):
         line: str
         tokens: list[Token]
@@ -45,22 +52,22 @@ class REPL:
 
         self.greet()
         self.init_history()
+        self.init_completer()
 
-        buf: str = ""
         while True:
             try:
-                line = input(">>> " if len(buf) == 0 else "... ")
+                line = input(">>> " if len(self.buf) == 0 else "... ")
             except EOFError:
                 print()
                 break
             except KeyboardInterrupt:
-                buf = ""
+                self.buf = ""
                 print()
                 continue
 
-            buf += line + "\n"
+            self.buf += line + "\n"
             try:
-                tokens = Lexer(buf).process()
+                tokens = Lexer(self.buf).process()
             except:
                 continue
             if Pebble.had_error:
@@ -71,7 +78,7 @@ class REPL:
                 continue
 
             program = Parser(tokens).parse()
-            buf = ""
+            self.buf = ""
 
             if Pebble.had_error:
                 Pebble.had_error = False