import csv, re, serial
from typing import Callable, Optional

CTRL_SPLIT_RE = re.compile(rb'[\x1d\x1e\x04]+')  # GS, RS, EOT

def _strip_header_bytes(b: bytes) -> bytes:
    b = b.strip()
    if b.startswith(b'\x02'): b = b[1:]          # STX
    if b.startswith(b'[)>'):  b = b[3:]
    if b.startswith(b'06'):    b = b[2:]         # format code
    return b

def _normalize_from_bytes(raw: bytes) -> str:
    raw = _strip_header_bytes(raw)
    chunks = [c for c in CTRL_SPLIT_RE.split(raw) if c]
    flat = b''.join(chunks) if chunks else raw
    s = flat.decode('ascii', errors='ignore').strip()
    if s.startswith('06'): s = s[2:]
    return s

def scan_loop(port: str, baud: int, on_scan: Callable[[str], None]):
    ser = serial.Serial(port, baud, timeout=2)
    print(f"Opened {port}. Ready — scan a label.")
    while True:
        data = ser.read_until(b'\r')  # adjust to b'\n' if needed
        if not data: 
            continue
        flat = _normalize_from_bytes(data)
        if flat:
            on_scan(flat)

def maybe_append_csv(path: Optional[str], fields: dict):
    if not path: return
    newfile = not os.path.exists(path)
    import os
    with open(path, "a", newline="", encoding="utf-8") as f:
        w = csv.DictWriter(f, fieldnames=list(fields.keys()))
        if newfile: w.writeheader()
        w.writerow(fields)

def read_one_scan(port: str, baud: int, read_terminator: bytes = b'\r') -> str:
    with serial.Serial(port, baud, timeout=10) as ser:
        data = ser.read_until(read_terminator)
        return _normalize_from_bytes(data)