# mapping_rules.py
import re, datetime

KNOWN_HEADWORKS = ["Tarbela","Kalabagh","Chashma","Taunsa","Taunsa","Guddu","Sukkur","Kotri","Mangla","Rasul","Marala",
                   "Khanki","Qadirabad","Trimmu","Panjnad","Balloki","Sidhnai","Sulemanki","Islam",]

def parse_number(s):
    if s is None: return None
    s = str(s).strip()
    if s == "": return None
    s = s.replace(',', '').replace('O','0').replace('o','0').replace('I','1').replace('l','1').replace('S','5')
    neg = False
    if re.search(r'^\(.*\)$', s):
        neg = True
        s = s.strip('()')
    m = re.search(r'[-+]?\d+(\.\d+)?', s)
    if not m: return None
    try:
        val = float(m.group(0))
    except:
        return None
    return -val if neg else val

def parse_date(s):
    if not s: return None
    s = str(s).strip()
    for fmt in ("%d-%m-%Y","%d/%m/%Y","%Y-%m-%d","%d-%m-%y","%d %b %Y","%d %B %Y"):
        try:
            return datetime.datetime.strptime(s, fmt).date().isoformat()
        except:
            pass
    m = re.search(r'(\d{1,2})[\/\-](\d{1,2})[\/\-](\d{2,4})', s)
    if m:
        d,mo,y = m.groups()
        if len(y)==2: y = '20'+y
        return f"{int(y):04d}-{int(mo):02d}-{int(d):02d}"
    return None

def find_known_headworks(text):
    if not text: return None
    for h in KNOWN_HEADWORKS:
        if h.lower() in text.lower():
            return h
    return None

def detect_unit(text):
    if not text: return None
    t = str(text)
    if re.search(r'\b(cs|Cs|CS)\b', t): return 'Cs'
    if re.search(r'\b(ft|FT)\b', t): return 'ft'
    if re.search(r'\b(ind|IND)\b', t): return 'IND'
    return None

def map_row(cells, confidences=None, header_tokens=None):
    """
    cells: list of strings (OCR per column)
    confidences: list of floats (0..1)
    header_tokens: optional list of header strings if row is header
    returns: dict with canonical fields
    """
    if confidences is None:
        confidences = [0.95]*len(cells)
    joined = " | ".join([c for c in cells if c])
    header = " ".join(header_tokens).lower() if header_tokens else ""
    out = {
        "Date": None, "Headworks": None, "Canal": None, "Site": None,
        "A.F.S.Q": None, "Gauge": None, "Indent": None, "Actual": None,
        "Unit": None, "SourceRowText": joined, "OCRConfidence": round(sum(confidences)/len(confidences),3)
    }
    # Date
    for c in cells:
        d = parse_date(c)
        if d:
            out["Date"] = d
            break
    # Headworks
    if header and "headwork" in header:
        for t in header_tokens:
            h = find_known_headworks(t)
            if h:
                out["Headworks"] = h
                break
    if not out["Headworks"]:
        for c in cells[:3]:
            h = find_known_headworks(c)
            if h:
                out["Headworks"] = h
                break
    # Gauge detection (decimal-like)
    gauge_idx = None
    for i,c in enumerate(cells):
        if c and re.search(r'\d+\.\d{1,2}', str(c)):
            gauge_idx = i
            out["Gauge"] = parse_number(c)
            break
    # Numeric candidates
    nums = [(i, parse_number(c)) for i,c in enumerate(cells) if parse_number(c) is not None]
    nums = [(i,v) for (i,v) in nums if i!=gauge_idx]
    nums_sorted = sorted(nums, key=lambda x: abs(x[1]) if x[1] is not None else 0, reverse=True)
    if len(nums_sorted)>=1:
        out["Indent"] = nums_sorted[0][1]
    if len(nums_sorted)>=2:
        out["Actual"] = nums_sorted[1][1]
    # A.F.S.Q detection (small decimal or single-digit)
    for c in cells:
        try:
            val = float(str(c).strip())
            if val>0 and val<30:
                out["A.F.S.Q"] = val
                break
        except:
            continue
    # Unit detection
    for c in cells:
        u = detect_unit(c)
        if u:
            out["Unit"] = u
            break
    # Canal and Site heuristics
    for c in cells:
        if c and any(k in str(c).lower() for k in ["canal","link","feeder","escape","branch","rd","rd-","tail","head"]):
            if not out["Canal"]:
                out["Canal"] = str(c).strip().title()
            elif not out["Site"]:
                out["Site"] = str(c).strip().upper()
    # Site tokens U/S D/S HEAD TAIL
    for c in cells:
        if c and any(k in str(c).upper() for k in ["U/S","D/S","HEAD","TAIL","RD","RD-"]):
            out["Site"] = str(c).strip().upper()
            break
    return out