Add Windows REPL virtual terminal queue

To support virtual terminal mode in Windows PYREPL, we need a scanner
to read over the supported escaped VT sequences.

Signed-off-by: y5c4l3 <[email protected]>

Author: y5c4l3

Lib/_pyrepl/windows_eventqueue.py

@@ -0,0 +1,117 @@
+"""
+Windows event and VT sequence scanner, similar to `unix_eventqueue.py`
+"""
+
+from collections import deque
+
+from . import keymap
+from .console import Event
+from .trace import trace
+import os
+
+# Reference: https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#input-sequences
+VT_MAP: dict[bytes, str] = {
+    b'\x1b[A': 'up',
+    b'\x1b[B': 'down',
+    b'\x1b[C': 'right',
+    b'\x1b[D': 'left',
+
+    b'\x1b[H': 'home',
+    b'\x1b[F': 'end',
+
+    b'\x7f': 'backspace',
+    b'\x1b[2~': 'insert',
+    b'\x1b[3~': 'delete',
+    b'\x1b[5~': 'page up',
+    b'\x1b[6~': 'page down',
+
+    b'\x1bOP':    'f1',
+    b'\x1bOQ':    'f2',
+    b'\x1bOR':    'f3',
+    b'\x1bOS':    'f4',
+    b'\x1b[15~':  'f5',
+    b'\x1b[17~]': 'f6',
+    b'\x1b[18~]': 'f7',
+    b'\x1b[19~]': 'f8',
+    b'\x1b[20~]': 'f9',
+    b'\x1b[21~]': 'f10',
+    b'\x1b[23~]': 'f11',
+    b'\x1b[24~]': 'f12',
+}
+
+class EventQueue:
+    def __init__(self, encoding: str) -> None:
+        self.compiled_keymap = keymap.compile_keymap(VT_MAP)
+        self.keymap = self.compiled_keymap
+        trace("keymap {k!r}", k=self.keymap)
+        self.encoding = encoding
+        self.events: deque[Event] = deque()
+        self.buf = bytearray()
+
+    def get(self) -> Event | None:
+        """
+        Retrieves the next event from the queue.
+        """
+        if self.events:
+            return self.events.popleft()
+        else:
+            return None
+
+    def empty(self) -> bool:
+        """
+        Checks if the queue is empty.
+        """
+        return not self.events
+
+    def flush_buf(self) -> bytearray:
+        """
+        Flushes the buffer and returns its contents.
+        """
+        old = self.buf
+        self.buf = bytearray()
+        return old
+
+    def insert(self, event: Event) -> None:
+        """
+        Inserts an event into the queue.
+        """
+        trace('added event {event}', event=event)
+        self.events.append(event)
+
+    def push(self, char: int | bytes) -> None:
+        """
+        Processes a character by updating the buffer and handling special key mappings.
+        """
+        ord_char = char if isinstance(char, int) else ord(char)
+        char = bytes(bytearray((ord_char,)))
+        self.buf.append(ord_char)
+        if char in self.keymap:
+            if self.keymap is self.compiled_keymap:
+                #sanity check, buffer is empty when a special key comes
+                assert len(self.buf) == 1
+            k = self.keymap[char]
+            trace('found map {k!r}', k=k)
+            if isinstance(k, dict):
+                self.keymap = k
+            else:
+                self.insert(Event('key', k, self.flush_buf()))
+                self.keymap = self.compiled_keymap
+
+        elif self.buf and self.buf[0] == 27:  # escape
+            # escape sequence not recognized by our keymap: propagate it
+            # outside so that i can be recognized as an M-... key (see also
+            # the docstring in keymap.py
+            trace('unrecognized escape sequence, propagating...')
+            self.keymap = self.compiled_keymap
+            self.insert(Event('key', '\033', bytearray(b'\033')))
+            for _c in self.flush_buf()[1:]:
+                self.push(_c)
+
+        else:
+            try:
+                decoded = bytes(self.buf).decode(self.encoding)
+            except UnicodeError:
+                return
+            else:
+                self.insert(Event('key', decoded, self.flush_buf()))
+            self.keymap = self.compiled_keymap