import re
import secrets
import string

from app.services.mailer import send_email
from app.services.redis_client import get_redis

EMAIL_CODE_TTL_SEC = 600
EMAIL_CODE_PURPOSES = ("register", "login", "reset")
_EMAIL_RE = re.compile(r"^[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+\.[A-Za-z]{2,}$")


def normalize_email(email: str) -> str:
    return (email or "").strip().lower()


def is_valid_email(email: str) -> bool:
    text = normalize_email(email)
    return bool(text) and len(text) <= 191 and _EMAIL_RE.match(text) is not None


def _key(purpose: str, email: str) -> str:
    return f"gsfdc:email_code:{purpose}:{normalize_email(email)}"


def _rate_key(purpose: str, email: str) -> str:
    return f"gsfdc:email_code_rate:{purpose}:{normalize_email(email)}"


def _new_code() -> str:
    return "".join(secrets.choice(string.digits) for _ in range(6))


def issue_email_code(*, email: str, purpose: str) -> None:
    if purpose not in EMAIL_CODE_PURPOSES:
        raise ValueError("验证码用途不正确")
    if not is_valid_email(email):
        raise ValueError("邮箱格式不正确")
    normalized = normalize_email(email)
    redis = get_redis()
    if redis.get(_rate_key(purpose, normalized)):
        raise ValueError("发送过于频繁，请稍后再试")
    code = _new_code()
    redis.set(_key(purpose, normalized), code, ex=EMAIL_CODE_TTL_SEC)
    redis.set(_rate_key(purpose, normalized), "1", ex=60)
    labels = {"register": "注册", "login": "登录", "reset": "重置密码"}
    subject = f"甘肃省房地产价格评估行业协会 · {labels[purpose]}验证码"
    body = (
        f"您的{labels[purpose]}验证码是：{code}\n"
        f"有效期 {EMAIL_CODE_TTL_SEC // 60} 分钟。如非本人操作请忽略本邮件。\n"
    )
    try:
        send_email(to=normalized, subject=subject, body=body)
    except Exception:
        # 发信失败时仍保留验证码，便于本地/测试校验路径；生产日志可见失败。
        import logging

        logging.getLogger("gsfdc.email_code").exception("邮箱验证码发信失败")


def consume_email_code(*, email: str, purpose: str, code: str) -> bool:
    if purpose not in EMAIL_CODE_PURPOSES:
        return False
    if not is_valid_email(email) or not isinstance(code, str):
        return False
    normalized = normalize_email(email)
    text = code.strip()
    if not text:
        return False
    # 仅在码匹配时删除；输错不消耗，避免一次错码废掉仍有效的验证码。
    redis = get_redis()
    key = _key(purpose, normalized)
    deleted = redis.eval(
        "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end",
        1,
        key,
        text,
    )
    return bool(deleted)