Flock: CLI first try (starts and stops the hypervisor)

diff --git a/flock/flock-cli b/flock/flock-cli
new file mode 100755 (executable)
index 0000000..4318a32
--- /dev/null
+++ b/flock/flock-cli
@@ -0,0 +1,133 @@
+#!/usr/bin/python3
+
+import cbor2
+import os
+import pathlib
+import socket
+import subprocess
+import sys
+
+DEFAULT_RUN_PATH = pathlib.Path(f"/run/user/{os.getuid()}/flock")
+handlers = {}
+
+class HandlerError(Exception):
+    pass
+
+def handler(fun):
+    items = fun.__name__.split("_")
+
+    hx = handlers
+    while len(items) > 1:
+        if (s := items.pop(0)) not in hx:
+            hx[s] = dict()
+        hx = hx[s]
+
+    if items[0] in hx:
+        raise Exception(f"Duplicate handler {fun.__name__}")
+
+    hx[items[0]] = fun
+
+class HypervisorNonexistentError(HandlerError):
+    def __init__(self, *args, **kwargs):
+        return super().__init__("Hypervisor not found", *args, **kwargs)
+
+class HypervisorStaleError(HandlerError):
+    def __init__(self, *args, **kwargs):
+        return super().__init__("Hypervisor stale", *args, **kwargs)
+
+def connect(where: pathlib.Path):
+    if not where.exists():
+        raise HypervisorNonexistentError()
+
+    client = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    try:
+        client.connect(bytes(where))
+    except ConnectionRefusedError:
+        raise HypervisorStaleError()
+    return client
+
+def ctl_path(name: str):
+    return DEFAULT_RUN_PATH / f"{name}.ctl"
+
+def msg(name: str, data: dict):
+    try:
+        ctl = connect(ctl_path(name))
+    except HypervisorNonexistentError as e:
+        e.add_note(f"Failed to send message {data} to {name}")
+        raise e
+
+    ctl.sendall(cbor2.dumps(data))
+    return cbor2.loads(ctl.recv(1024))
+
+@handler
+def start(name: str):
+    DEFAULT_RUN_PATH.mkdir(parents=True, exist_ok=True)
+    try:
+        connect(ctl := ctl_path(name))
+        raise HandlerError("Hypervisor already exists")
+    except HypervisorNonexistentError:
+        pass
+    
+    subprocess.run(["./flock-sim", "-s", ctl, name])
+
+@handler
+def stop(name: str):
+    for k,v in msg(name, { 0: None }).items():
+        assert(k == -1)
+        assert(v == "OK")
+
+@handler
+def cleanup(name: str):
+    try:
+        connect(ctl := ctl_path(name))
+        raise HandlerError("Hypervisor is not stale")
+    except HypervisorStaleError:
+        ctl.unlink()
+
+@handler
+def container_start(hypervisor: str, name: str):
+    print(f"start a machine {name} in {hypervisor}")
+
+try:
+    binname = sys.argv.pop(0)
+except Exception as e:
+    raise RuntimeError from e
+    
+def usage(name: str):
+    print(
+            f"Usage: {name} <command> <args>",
+            f"",
+            f"Available commands:",
+            f"\tstart <name>                             start Flock hypervisor",
+            f"\t                                         creates <name>.ctl in {DEFAULT_RUN_PATH}",
+            f"\tstop <name>                              stop Flock hypervisor",
+            f"\tcleanup <name>                           cleanup the control socket left behind a stale hypervisor",
+            f"\tcontainer start <hypervisor> <name>      start virtual machine",
+            f"\tcontainer stop <hypervisor> <name>       stop virtual machine",
+            f"\ttelnet <hypervisor> <name>               run telnet to this machine",
+            sep="\n")
+
+cmd = []
+hx = handlers
+while type(hx) is dict:
+    try:
+        hx = hx[cx := sys.argv.pop(0)]
+    except (IndexError, KeyError):
+        usage(binname)
+        exit(2)
+
+    cmd.append(cx)
+
+try:
+    hx(*sys.argv)
+except HandlerError as e:
+    print(f"Error: {e}")
+#    raise e
+    exit(1)
+except TypeError as e:
+    usage(binname)
+    print()
+    print(f"Error in command {' '.join(cmd)}.")
+    raise RuntimeError from e
+    exit(2)
+