#!/usr/bin/env python3
"""
Simulateur Modbus RTU — émule les registres de l'Epever Tracer 4210N.

Se connecte au serveur TCP exposé par QEMU pour UART2 (port 1235).
Répond aux requêtes FC04 (Read Input Registers) avec des valeurs simulées
qui varient dans le temps pour reproduire un comportement réaliste.
"""
import math
import socket
import time

QEMU_HOST = '127.0.0.1'
QEMU_PORT = 1235
RECONNECT_DELAY = 2  # secondes


# ---------------------------------------------------------------------------
# CRC16 Modbus
# ---------------------------------------------------------------------------

def crc16(data: bytes) -> int:
    crc = 0xFFFF
    for b in data:
        crc ^= b
        for _ in range(8):
            crc = (crc >> 1) ^ 0xA001 if crc & 1 else crc >> 1
    return crc


# ---------------------------------------------------------------------------
# Registres simulés Epever Tracer 4210N
# ---------------------------------------------------------------------------

def get_reg(addr: int) -> int:
    """Retourne la valeur simulée d'un registre, avec variation sinusoïdale."""
    t = time.time()

    # --- PV (0x3100..0x3107) ---
    if addr == 0x3100:  # Tension PV × 100
        return max(0, 1872 + int(50 * math.sin(t / 60)))
    if addr == 0x3101:  # Courant PV × 100
        return max(0, 420 + int(30 * abs(math.sin(t / 45))))
    if addr == 0x3104:  # Tension batterie × 100
        return 1345 + int(20 * math.sin(t / 120))

    # --- Load + température batterie (0x310C..0x3110) ---
    if addr == 0x310C:  return 1340           # Tension load × 100 = 13.40 V
    if addr == 0x310D:  return 200            # Courant load × 100 = 2.00 A
    if addr == 0x310E:  return 2680           # Puissance load × 100 = 26.80 W
    if addr == 0x3110:  return 2500           # Temp. batterie × 100 = 25.00 °C

    # --- SOC (0x311A) ---
    if addr == 0x311A:  return 75             # SOC = 75 %

    # --- Statut charge (0x3200) ---
    if addr == 0x3200:  return 0x0004         # bits 3-2 = 01 → charge float

    # --- Énergie (0x3300..0x3307) — registres 32 bits (Low/High) ---
    if addr == 0x3300:  return 150            # Prod. aujourd'hui low  = 1.50 kWh
    if addr == 0x3301:  return 0
    if addr == 0x3302:  return 12000          # Prod. totale low       = 120.00 kWh
    if addr == 0x3303:  return 0
    if addr == 0x3304:  return 80             # Conso. aujourd'hui low = 0.80 kWh
    if addr == 0x3305:  return 0
    if addr == 0x3306:  return 8500           # Conso. totale low      = 85.00 kWh
    if addr == 0x3307:  return 0

    # --- Jour/Nuit (0x200C) ---
    if addr == 0x200C:  return 0x0008         # Bit 3 = 1 → charge active (jour)

    return 0


# ---------------------------------------------------------------------------
# Construction de la réponse FC04
# ---------------------------------------------------------------------------

def build_fc04_response(slave: int, start: int, count: int) -> bytes:
    values = [get_reg(start + i) for i in range(count)]
    payload = bytes([slave, 0x04, count * 2])
    payload += b''.join(v.to_bytes(2, 'big') for v in values)
    crc = crc16(payload)
    return payload + bytes([crc & 0xFF, crc >> 8])


# ---------------------------------------------------------------------------
# Gestion d'une connexion QEMU
# ---------------------------------------------------------------------------

def handle(sock: socket.socket) -> None:
    print('[Modbus] ✓ Connecté à QEMU UART2', flush=True)
    buf = bytearray()
    try:
        while True:
            chunk = sock.recv(256)
            if not chunk:
                break
            buf.extend(chunk)

            # Trame RTU FC04 : exactement 8 octets
            while len(buf) >= 8:
                slave, fc = buf[0], buf[1]
                start  = (buf[2] << 8) | buf[3]
                count  = (buf[4] << 8) | buf[5]
                crc_rx = buf[6] | (buf[7] << 8)

                if crc16(bytes(buf[:6])) == crc_rx and fc == 0x04:
                    resp = build_fc04_response(slave, start, count)
                    sock.sendall(resp)
                    print(f'[Modbus]  FC04 0x{start:04X} × {count} reg → envoyé', flush=True)
                    del buf[:8]
                else:
                    # Octet parasite — décaler
                    del buf[:1]

    except (ConnectionResetError, BrokenPipeError, OSError):
        pass
    print('[Modbus] Déconnecté', flush=True)


# ---------------------------------------------------------------------------
# Boucle principale : reconnexion automatique
# ---------------------------------------------------------------------------

def main() -> None:
    print(f'[Modbus] Attente de QEMU UART2 sur tcp://{QEMU_HOST}:{QEMU_PORT}', flush=True)
    while True:
        try:
            with socket.create_connection((QEMU_HOST, QEMU_PORT), timeout=60) as sock:
                handle(sock)
        except (ConnectionRefusedError, OSError) as exc:
            print(f'[Modbus] {exc} — retry dans {RECONNECT_DELAY}s', flush=True)
            time.sleep(RECONNECT_DELAY)


if __name__ == '__main__':
    main()