# -*- coding: utf-8 -*-
import hashlib

def stable_symbol_id(symbol: str, exchange: str = "US") -> int:
    """Generate a stable positive 64-bit int ID from symbol+exchange.
    Collisions are extremely unlikely for our scale.
    """
    base = f"{exchange}:{symbol}".upper().encode("utf-8")
    h = hashlib.sha1(base).digest()
    # take first 8 bytes as unsigned 64-bit integer
    val = int.from_bytes(h[:8], byteorder="big", signed=False)
    # constrain to 63-bit to avoid CSV tools issues with signedness
    return val & ((1 << 63) - 1)