import base64
import io
import secrets

from PIL import Image, ImageDraw, ImageFont

from app.services.redis_client import get_redis

CAPTCHA_TTL_SEC = 120
CAPTCHA_ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"


def _key(captcha_id: str) -> str:
    return f"gsfdc:captcha:{captcha_id}"


def _new_code() -> str:
    return "".join(secrets.choice(CAPTCHA_ALPHABET) for _ in range(4))


def _image(code: str) -> str:
    width, height = 132, 48
    image = Image.new("RGB", (width, height), (246, 248, 251))
    draw = ImageDraw.Draw(image)
    font = ImageFont.load_default(size=26)
    for _ in range(5):
        draw.line(
            (
                secrets.randbelow(width),
                secrets.randbelow(height),
                secrets.randbelow(width),
                secrets.randbelow(height),
            ),
            fill=(180, 190, 200),
            width=1,
        )
    for index, char in enumerate(code):
        color = (secrets.randbelow(80), secrets.randbelow(80), 40 + secrets.randbelow(80))
        draw.text((12 + index * 30, 8 + secrets.randbelow(8)), char, font=font, fill=color)
    buffer = io.BytesIO()
    image.save(buffer, format="PNG")
    encoded = base64.b64encode(buffer.getvalue()).decode("ascii")
    return f"data:image/png;base64,{encoded}"


def issue_captcha() -> dict:
    captcha_id = secrets.token_hex(16)
    code = _new_code()
    get_redis().set(_key(captcha_id), code.lower(), ex=CAPTCHA_TTL_SEC)
    return {"captchaId": captcha_id, "image": _image(code)}


def consume_captcha(captcha_id: str, code: str) -> bool:
    if not isinstance(captcha_id, str) or not isinstance(code, str):
        return False
    captcha_id = captcha_id.strip()
    code = code.strip()
    if not captcha_id or not code:
        return False
    stored = get_redis().getdel(_key(captcha_id))
    if stored is None:
        return False
    if isinstance(stored, bytes):
        stored = stored.decode("utf-8", errors="replace")
    if not isinstance(stored, str):
        return False
    return stored.lower() == code.lower()