"""Lightweight browser/OS classification for human traffic (Chapter 08).

Separate from Chapter 07's bot_identifier — that identifies automated
crawlers via UA substring + DNS verification. This classifies ordinary
browsers/OSes, same ordered-substring-match pattern, signatures as JSON
data (not hardcoded), no third-party UA-parsing dependency — consistent
with the low-footprint bias in Chapter 03.

Order matters within each signature list: e.g. Edge/Opera must be checked
before Chrome (their UAs also contain "Chrome/"); iOS before macOS (iPhone
UAs also contain "like Mac OS X"); Android before Linux (Android UAs also
contain "Linux").
"""
from __future__ import annotations

import json
from dataclasses import dataclass
from pathlib import Path

_DATA_DIR = Path(__file__).parent / "data"


@dataclass(frozen=True)
class UASignature:
    name: str
    ua_substrings: tuple[str, ...]


def _load(filename: str) -> list[UASignature]:
    raw = json.loads((_DATA_DIR / filename).read_text())
    return [UASignature(name=e["name"], ua_substrings=tuple(e["ua_substrings"])) for e in raw]


_BROWSER_SIGNATURES = _load("browser_signatures.json")
_OS_SIGNATURES = _load("os_signatures.json")


def _match(user_agent: str, signatures: list[UASignature], default: str) -> str:
    for sig in signatures:
        if any(sub in user_agent for sub in sig.ua_substrings):
            return sig.name
    return default


def classify_browser(user_agent: str | None) -> str:
    if not user_agent:
        return "Unknown"
    return _match(user_agent, _BROWSER_SIGNATURES, "Other")


def classify_os(user_agent: str | None) -> str:
    if not user_agent:
        return "Unknown"
    return _match(user_agent, _OS_SIGNATURES, "Other")