import socket
import time
import random
from datetime import datetime

HOST = "127.0.0.1"
PORT = 12345

VT = b'\x0b'
FS_CR = b'\x1c\x0d'

def generate_hl7_message(patient_id="PAT-12345", device_id="MOCK-CMS7000"):
    # Generate realistic vital signs with small random variations
    hr = random.randint(70, 95)
    spo2 = random.randint(96, 99)
    sys = random.randint(115, 125)
    dia = random.randint(75, 83)
    map_bp = int(dia + (sys - dia) / 3)
    resp = random.randint(14, 18)
    temp = round(random.uniform(36.5, 37.1), 1)

    now_str = datetime.now().strftime("%Y%m%d%H%M%S")

    # Construct HL7 message segments
    msh = f"MSH|^~\\&|{device_id}|MOCK_FACILITY|RECEIVING_APP|RECEIVING_FACILITY|{now_str}||ORU^R01|MSG{now_str}|P|2.3.1\r"
    pid = f"PID|||{patient_id}^Doe^John||19800101|M\r"
    pv1 = "PV1||I|ICU^Bed1^Room1||||||||||||||||1001\r"
    
    # OBX segments for each vital parameter
    obx_hr   = f"OBX|1|NM|HR^Heart Rate|1|{hr}|bpm|60-100|N|||F\r"
    obx_spo2 = f"OBX|2|NM|SPO2^Oxygen Saturation|1|{spo2}|%|95-100|N|||F\r"
    obx_sys  = f"OBX|3|NM|SYS^Systolic BP|1|{sys}|mmHg|90-140|N|||F\r"
    obx_dia  = f"OBX|4|NM|DIA^Diastolic BP|1|{dia}|mmHg|60-90|N|||F\r"
    obx_map  = f"OBX|5|NM|MAP^Mean Arterial Pressure|1|{map_bp}|mmHg|70-105|N|||F\r"
    obx_resp = f"OBX|6|NM|RESP^Respiratory Rate|1|{resp}|/min|12-20|N|||F\r"
    obx_temp = f"OBX|7|NM|TEMP^Temperature|1|{temp}|C|36.1-37.2|N|||F"

    hl7_msg = msh + pid + pv1 + obx_hr + obx_spo2 + obx_sys + obx_dia + obx_map + obx_resp + obx_temp
    return hl7_msg

def main():
    print(f"Starting mock patient monitor simulator...")
    print(f"Connecting to Contec receiver at {HOST}:{PORT}...")
    
    while True:
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.connect((HOST, PORT))
            print(f"Connected to Contec server at {HOST}:{PORT}")
            
            while True:
                hl7_msg = generate_hl7_message()
                # Frame message with MLLP wrappers (VT ... FS_CR)
                framed_msg = VT + hl7_msg.encode('utf-8') + FS_CR
                
                print(f"[{datetime.now().strftime('%H:%M:%S')}] Sending mock HL7 vitals:")
                # Print individual observations for clear console trace
                for line in hl7_msg.split('\r'):
                    if line.startswith("OBX"):
                        print(f"  {line}")
                
                s.sendall(framed_msg)
                
                # Check for ACK response
                try:
                    s.settimeout(1.0)
                    response = s.recv(4096)
                    if response:
                        print("  [ACK Received]")
                except socket.timeout:
                    pass
                
                time.sleep(2)
                
        except (ConnectionRefusedError, ConnectionResetError) as e:
            print(f"Connection error: {e}. Retrying in 3 seconds...")
            time.sleep(3)
        except Exception as e:
            print(f"Unexpected error: {e}. Retrying in 3 seconds...")
            time.sleep(3)

if __name__ == "__main__":
    main()