import hashlib
import re
from typing import Optional

def normalize_text(text: Optional[str]) -> str:
    """Normalize text by removing URLs, telegram handles, hashtags, excessive punctuation/whitespace, and lowercasing."""
    if not text:
        return ""
    # Remove URLs
    text = re.sub(r'https?://\S+|www\.\S+', '', text)
    # Remove Telegram @mentions / hashtags
    text = re.sub(r'[@#]\w+', '', text)
    # Normalize punctuation and whitespace
    text = re.sub(r'[^\w\s]', ' ', text)
    text = re.sub(r'\s+', ' ', text)
    return text.strip().lower()

def compute_content_hash(text: Optional[str], media_hash: Optional[str] = None) -> Optional[str]:
    """Generate SHA256 hash from normalized text and/or media hash."""
    norm_text = normalize_text(text)
    if not norm_text and not media_hash:
        return None
    raw_key = f"{norm_text}|{media_hash or ''}"
    return hashlib.sha256(raw_key.encode('utf-8')).hexdigest()

def compute_file_hash(file_path: str) -> Optional[str]:
    """Generate SHA256 hash of a media file."""
    try:
        hasher = hashlib.sha256()
        with open(file_path, 'rb') as f:
            while chunk := f.read(65536):
                hasher.update(chunk)
        return hasher.hexdigest()
    except Exception:
        return None