# Simulates the SDK heartbeat: connects to the virtual camera's TCP 6679,
# sends UpdateAck(203) heartbeats periodically, and verifies each response.
# If the connection drops or a response is wrong, the SDK would mark the
# device offline after 3 consecutive failures.
import socket
import struct
import time
import sys

HOST = "127.0.0.1"
PORT = 6679

def pack_frame(op, cmd, seq, payload=b""):
    total = 24 + len(payload)
    return (b"VZEB" + struct.pack("<IIII", total, op, cmd, seq) +
            payload + b"VZEE")

def unpack(buf):
    # returns (op, cmd, seq, payload, consumed) or None if incomplete
    if len(buf) < 20:
        return None
    # find VZEB head
    pos = buf.find(b"VZEB")
    if pos < 0:
        return None
    total = struct.unpack("<I", buf[pos+4:pos+8])[0]
    if len(buf) < pos + total:
        return None
    op, cmd, seq = struct.unpack("<III", buf[pos+8:pos+20])
    tail = buf[pos+total-4:pos+total]
    payload = buf[pos+20:pos+total-4]
    if tail != b"VZEE":
        return None
    return (op, cmd, seq, payload, pos + total)

def main():
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(3.0)
    try:
        sock.connect((HOST, PORT))
    except Exception as e:
        print(f"[FAIL] connect failed: {e}")
        sys.exit(1)
    print("connected")

    buf = b""
    seq = 0
    ok = 0
    fail = 0
    start = time.time()
    while time.time() - start < 15:
        seq += 1
        # Send heartbeat (UpdateAck = 203, empty payload, Request)
        sock.sendall(pack_frame(1, 203, seq))
        t0 = time.time()
        # Wait for the matching response
        got = None
        deadline = time.time() + 4.0
        while time.time() < deadline:
            try:
                chunk = sock.recv(4096)
            except socket.timeout:
                break
            if not chunk:
                print("[FAIL] connection closed by server")
                fail += 1
                sock.close()
                print(f"result: ok={ok} fail={fail}")
                sys.exit(1)
            buf += chunk
            r = unpack(buf)
            if r:
                got = r
                # Consume exactly this frame so a stale response isn't re-read.
                buf = buf[r[4]:]
                break
        if not got:
            print(f"[FAIL] heartbeat #{seq}: no response")
            fail += 1
        else:
            op, cmd, rseq, payload, _ = got
            if op == 2 and cmd == 203 and rseq == seq:
                err = struct.unpack("<I", payload[:4])[0] if len(payload) >= 4 else -1
                if err == 0:
                    ok += 1
                    print(f"  OK  heartbeat #{seq} err=0 ({time.time()-t0:.1f}s)")
                else:
                    print(f"[FAIL] heartbeat #{seq} errCode={err}")
                    fail += 1
            else:
                print(f"[FAIL] heartbeat #{seq} unexpected resp op={op} cmd={cmd} seq={rseq}")
                fail += 1
        time.sleep(2.0)

    sock.close()
    print(f"\nresult: ok={ok} fail={fail}")
    print("PASS" if fail == 0 else "FAIL")

if __name__ == "__main__":
    main()