from __future__ import annotations

import base64
import html
import secrets
from uuid import uuid4

from .redis_session import AdminSessionStore

CAPTCHA_ALPHABET = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"


def _captcha_code(length: int = 4) -> str:
    return "".join(secrets.choice(CAPTCHA_ALPHABET) for _ in range(length))


def _captcha_image(code: str) -> str:
    lines = "".join(
        f'<path d="M{secrets.randbelow(150) + 5},{secrets.randbelow(42) + 3} '
        f'L{secrets.randbelow(150) + 5},{secrets.randbelow(42) + 3}" />'
        for _ in range(5)
    )
    safe_code = html.escape(code)
    svg = (
        '<svg xmlns="http://www.w3.org/2000/svg" width="160" height="48" viewBox="0 0 160 48">'
        '<rect width="160" height="48" rx="4" fill="#f5f7fa"/>'
        f'<g stroke="#c0c4cc" stroke-width="1" opacity=".8">{lines}</g>'
        f'<text x="80" y="32" text-anchor="middle" fill="#303133" '
        'font-family="Arial,sans-serif" font-size="24" font-weight="700" letter-spacing="5">'
        f"{safe_code}</text></svg>"
    )
    encoded = base64.b64encode(svg.encode("utf-8")).decode("ascii")
    return f"data:image/svg+xml;base64,{encoded}"


def create_captcha(store: AdminSessionStore, ttl_seconds: int) -> dict[str, object]:
    captcha_id = uuid4().hex
    code = _captcha_code()
    store.create_captcha(captcha_id, code, ttl_seconds)
    return {
        "captchaEnabled": True,
        "captchaId": captcha_id,
        "image": _captcha_image(code),
        "expiresIn": ttl_seconds,
    }


def verify_captcha(store: AdminSessionStore, captcha_id: str, code: str) -> bool:
    return store.consume_captcha(captcha_id, code)