webrepl_cli.py: Add support for accessing the REPL.

With this commit, the webrepl_cli.py script can be used to access the REPL,
for example:

    $ ./webrepl_cli.py -p x 192.168.4.1
    op:repl, host:192.168.20.27, port:8266, passwd:x.
    Remote WebREPL version: (1, 17, 0)
    Use Ctrl-] to exit this shell
    1/2
    0.5
    >>>

Signed-off-by: Damien George <damien@micropython.org>

webrepl_cli.py

@@ -19,6 +19,8 @@
 WEBREPL_PUT_FILE = 1
 WEBREPL_GET_FILE = 2
 WEBREPL_GET_VER  = 3
+WEBREPL_FRAME_TXT = 0x81
+WEBREPL_FRAME_BIN = 0x82
 
 
 def debugmsg(msg):
@@ -35,13 +37,12 @@ def __init__(self, s):
             self.s = s
             self.buf = b""
 
-        def write(self, data):
+        def write(self, data, frame=WEBREPL_FRAME_BIN):
             l = len(data)
             if l < 126:
-                # TODO: hardcoded "binary" type
-                hdr = struct.pack(">BB", 0x82, l)
+                hdr = struct.pack(">BB", frame, l)
             else:
-                hdr = struct.pack(">BBH", 0x82, 126, l)
+                hdr = struct.pack(">BBH", frame, 126, l)
             self.s.send(hdr)
             self.s.send(data)
 
@@ -115,6 +116,71 @@ def get_ver(ws):
     return d
 
 
+def do_repl(ws):
+    import termios, select
+
+    class ConsolePosix:
+        def __init__(self):
+            self.infd = sys.stdin.fileno()
+            self.infile = sys.stdin.buffer.raw
+            self.outfile = sys.stdout.buffer.raw
+            self.orig_attr = termios.tcgetattr(self.infd)
+
+        def enter(self):
+            # attr is: [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]
+            attr = termios.tcgetattr(self.infd)
+            attr[0] &= ~(
+                termios.BRKINT | termios.ICRNL | termios.INPCK | termios.ISTRIP | termios.IXON
+            )
+            attr[1] = 0
+            attr[2] = attr[2] & ~(termios.CSIZE | termios.PARENB) | termios.CS8
+            attr[3] = 0
+            attr[6][termios.VMIN] = 1
+            attr[6][termios.VTIME] = 0
+            termios.tcsetattr(self.infd, termios.TCSANOW, attr)
+
+        def exit(self):
+            termios.tcsetattr(self.infd, termios.TCSANOW, self.orig_attr)
+
+        def readchar(self):
+            res = select.select([self.infd], [], [], 0)
+            if res[0]:
+                return self.infile.read(1)
+            else:
+                return None
+
+        def write(self, buf):
+            self.outfile.write(buf)
+
+    print("Use Ctrl-] to exit this shell")
+    console = ConsolePosix()
+    console.enter()
+    try:
+        while True:
+            sel = select.select([console.infd, ws.s], [], [])
+            c = console.readchar()
+            if c:
+                if c == b"\x1d":  # ctrl-], exit
+                    break
+                else:
+                    ws.write(c, WEBREPL_FRAME_TXT)
+            if ws.s in sel[0]:
+                c = ws.read(1, text_ok=True)
+                while c is not None:
+                    # pass character through to the console
+                    oc = ord(c)
+                    if oc in (8, 9, 10, 13, 27) or oc >= 32:
+                        console.write(c)
+                    else:
+                        console.write(b"[%02x]" % ord(c))
+                    if ws.buf:
+                        c = ws.read(1)
+                    else:
+                        c = None
+    finally:
+        console.exit()
+
+
 def put_file(ws, local_file, remote_file):
     sz = os.stat(local_file)[6]
     dest_fname = (SANDBOX + remote_file).encode("utf-8")
@@ -164,11 +230,16 @@ def get_file(ws, local_file, remote_file):
 
 def help(rc=0):
     exename = sys.argv[0].rsplit("/", 1)[-1]
-    print("%s - Perform remote file operations using MicroPython WebREPL protocol" % exename)
+    print(
+        "%s - Access REPL, perform remote file operations via MicroPython WebREPL protocol"
+        % exename
+    )
     print("Arguments:")
+    print("  [-p password] <host>                            - Access the remote REPL")
     print("  [-p password] <host>:<remote_file> <local_file> - Copy remote file to local file")
     print("  [-p password] <local_file> <host>:<remote_file> - Copy local file to remote file")
     print("Examples:")
+    print("  %s 192.168.4.1" % exename)
     print("  %s script.py 192.168.4.1:/another_name.py" % exename)
     print("  %s script.py 192.168.4.1:/app/" % exename)
     print("  %s -p password 192.168.4.1:/app/script.py ." % exename)
@@ -212,26 +283,30 @@ def client_handshake(sock):
 
 
 def main():
-    if len(sys.argv) not in (3, 5):
-        help(1)
-
     passwd = None
     for i in range(len(sys.argv)):
         if sys.argv[i] == '-p':
             sys.argv.pop(i)
             passwd = sys.argv.pop(i)
             break
 
-    if not passwd:
+    if len(sys.argv) not in (2, 3):
+        help(1)
+
+    if passwd is None:
         import getpass
         passwd = getpass.getpass()
 
-    if ":" in sys.argv[1] and ":" in sys.argv[2]:
-        error("Operations on 2 remote files are not supported")
-    if ":" not in sys.argv[1] and ":" not in sys.argv[2]:
-        error("One remote file is required")
+    if len(sys.argv) > 2:
+        if ":" in sys.argv[1] and ":" in sys.argv[2]:
+            error("Operations on 2 remote files are not supported")
+        if ":" not in sys.argv[1] and ":" not in sys.argv[2]:
+            error("One remote file is required")
 
-    if ":" in sys.argv[1]:
+    if len(sys.argv) == 2:
+        op = "repl"
+        host, port, _ = parse_remote(sys.argv[1] + ":")
+    elif ":" in sys.argv[1]:
         op = "get"
         host, port, src_file = parse_remote(sys.argv[1])
         dst_file = sys.argv[2]
@@ -248,7 +323,8 @@ def main():
 
     if True:
         print("op:%s, host:%s, port:%d, passwd:%s." % (op, host, port, passwd))
-        print(src_file, "->", dst_file)
+        if op in ("get", "put"):
+            print(src_file, "->", dst_file)
 
     s = socket.socket()
 
@@ -267,7 +343,9 @@ def main():
     # Set websocket to send data marked as "binary"
     ws.ioctl(9, 2)
 
-    if op == "get":
+    if op == "repl":
+        do_repl(ws)
+    elif op == "get":
         get_file(ws, dst_file, src_file)
     elif op == "put":
         put_file(ws, src_file, dst_file)