import pandas as pd
import re

def classify_signal(desca, tagname, descb=None):
    """
    Classify signal based on DESCA content, TAGNAME, and DESCB
    Priority order matters: PB_LT before PB, FIOH before FIO, SOL+DIVERT before SOL
    """
    if pd.isna(desca):
        return 'UNKNOWN'
    
    desca_str = str(desca).upper()
    tagname_str = str(tagname).upper()
    descb_str = str(descb).upper() if pd.notna(descb) else ''
    
    # Check for SPARE first
    if re.search(r'SPARE', desca_str):
        return 'SPARE'
    
    # Signal O patterns (check higher priority first)
    if re.search(r'BCN\d+_[AGBR]', desca_str):  # e.g., BCN3_B, BCN1_A
        return 'O'
    elif re.search(r'PB_LT', desca_str):
        return 'O'
    
    # Check for PR sensors (user rule: PR is I) - moved after specific patterns
    elif re.search(r'_PR\d+|PR\d+', desca_str):  # Match PR followed by digits (proximity sensors)
        return 'I'
    elif re.search(r'STO', desca_str):
        return 'O'
    elif re.search(r'BCN', desca_str) and 'FIOH' in tagname_str:
        return 'O'
    
    # IOLink patterns (check FIOH before FIO due to priority)
    elif re.search(r'SOL', desca_str) and re.search(r'DIVERT', descb_str):
        return 'IOLink'
    elif re.search(r'LPE', desca_str):
        return 'IOLink'
    elif re.search(r'FIOH', desca_str):
        return 'IOLink'
    elif re.search(r'BCN', desca_str) and 'FIO' in tagname_str:
        return 'IOLink'
    
    # Signal O patterns continued (SOL without DIVERT)
    elif re.search(r'SOL', desca_str):
        return 'O'
    
    # Signal I patterns
    elif re.search(r'PWM', desca_str):
        return 'I'
    elif re.search(r'CB', desca_str):
        return 'I'
    elif re.search(r'FPE', desca_str):
        return 'I'
    elif re.search(r'ENC', desca_str):
        return 'I'
    elif re.search(r'PS', desca_str):
        return 'I'
    elif re.search(r'EPC', desca_str):
        return 'I'
    elif re.search(r'PX', desca_str):
        return 'I'
    elif re.search(r'DISC', desca_str):
        return 'I'
    elif re.search(r'PE', desca_str):
        return 'I'
    elif re.search(r'PB', desca_str):  # This comes after PB_LT check
        return 'I'
    elif re.search(r'ESTOP', desca_str):
        return 'I'
    elif 'IB16' in tagname_str or 'IB16S' in tagname_str:
        return 'I'
    elif 'OB16E' in tagname_str:
        return 'O'
    
    return 'UNKNOWN'

def get_device_type(tagname):
    """Determine device type from TAGNAME"""
    tagname_str = str(tagname).upper()
    
    if 'VFD' in tagname_str:
        return 'APF'
    elif 'FIOH' in tagname_str:
        return 'Hub'
    elif 'FIO' in tagname_str:
        return 'M12DR'
    elif 'SIO' in tagname_str:
        return 'SIO'
    elif 'OB16E' in tagname_str:
        return 'OB16E'
    elif 'IB16S' in tagname_str:
        return 'IB16S'
    elif 'IB16' in tagname_str:
        return 'IB16'
    return 'UNKNOWN'