"""Address normalization and fingerprint utilities.

Used by 3-tier matching to produce stable, source-independent keys.
Algorithm reference: decisions/Cross_Source_Matching_Strategy.md sec 3.2
"""

import hashlib
import re
import unicodedata

# Strip punctuation EXCEPT hyphens — keep hyphens so abbreviation rules like
# 'пр-кт', 'б-р', 'пр-д' can match before they are collapsed to spaces.
_PUNCT = re.compile(r'[^\w\s\-]', flags=re.UNICODE)
_WS = re.compile(r'\s+')

# Abbreviation expansion — applied after lowercasing, bounded by spaces.
# Order matters: longer/more-specific patterns first to avoid partial overlap.
# Hyphenated forms ('пр-кт', 'б-р', 'пр-д') come first so they match before
# the shorter variants ('пр', 'б') would erroneously consume the prefix.
_ABBREV = [
    (' пр-кт ', ' проспект '),
    (' пр-кт. ', ' проспект '),
    (' б-р ', ' бульвар '),
    (' пр-д ', ' проезд '),
    (' ш ', ' шоссе '),
    (' ул ', ' улица '),
    (' ул. ', ' улица '),
    (' пр ', ' проспект '),
    (' пр. ', ' проспект '),
    (' пер ', ' переулок '),
    (' пл ', ' площадь '),
    (' наб ', ' набережная '),
    (' бул ', ' бульвар '),
    (' туп ', ' тупик '),
    (' стр ', ' строение '),
    (' корп ', ' корпус '),
    (' д ', ' дом '),
    (' к ', ' корпус '),
]


def normalize_address(text: str | None) -> str:
    """Normalize address string for cross-source comparison.

    Steps:
      1. Unicode NFC normalization
      2. Lowercase
      3. Strip punctuation except hyphens (preserve 'пр-кт', 'б-р', 'пр-д' for expansion)
      4. Collapse whitespace
      5. Expand common Russian address abbreviations (hyphenated forms first)
      6. Collapse remaining hyphens to spaces
    """
    if not text:
        return ""
    s = unicodedata.normalize('NFC', text).lower()
    s = _PUNCT.sub(' ', s)  # strip punctuation EXCEPT hyphens
    s = _WS.sub(' ', s).strip()
    # Wrap with spaces for clean boundary matching
    s = f' {s} '
    for short, full in _ABBREV:
        s = s.replace(short, full)
    # Collapse remaining hyphens (e.g. standalone '-' separators or numeric ranges)
    s = s.replace('-', ' ')
    return _WS.sub(' ', s).strip()


def address_fingerprint(address: str | None, lat: float | None, lon: float | None) -> str:
    """SHA-256 fingerprint of normalized address + rounded coordinates (4 dp ≈ 11 m).

    Returns first 32 hex chars of the digest (128 bits — collision-safe for millions of rows).
    """
    norm_addr = normalize_address(address or '')
    lat_r = f'{lat:.4f}' if lat is not None else ''
    lon_r = f'{lon:.4f}' if lon is not None else ''
    key = f'{norm_addr}|{lat_r}|{lon_r}'
    return hashlib.sha256(key.encode('utf-8')).hexdigest()[:32]