import aiosmtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from sqlalchemy import select
from app.core.database import async_session
from app.core.config import get_settings
from app.models.models import SystemSetting

settings = get_settings()


async def get_site_url() -> str:
    async with async_session() as db:
        result = await db.execute(select(SystemSetting).where(SystemSetting.key == "site_url"))
        setting = result.scalar_one_or_none()
    if setting and setting.value.strip():
        return setting.value.strip().rstrip("/")
    return "http://localhost:806"


async def get_smtp_config() -> dict:
    async with async_session() as db:
        result = await db.execute(
            select(SystemSetting).where(
                SystemSetting.key.in_([
                    "smtp_host", "smtp_port", "smtp_user",
                    "smtp_password", "smtp_from", "smtp_use_tls",
                ])
            )
        )
        rows = {r.key: r.value for r in result.scalars().all()}

    if rows.get("smtp_host") and rows.get("smtp_user"):
        return {
            "host": rows.get("smtp_host", ""),
            "port": int(rows.get("smtp_port", "465")),
            "user": rows.get("smtp_user", ""),
            "password": rows.get("smtp_password", ""),
            "from_addr": rows.get("smtp_from") or rows.get("smtp_user", ""),
            "use_tls": rows.get("smtp_use_tls", "true") == "true",
        }
    return {
        "host": settings.SMTP_HOST,
        "port": settings.SMTP_PORT,
        "user": settings.SMTP_USER,
        "password": settings.SMTP_PASSWORD,
        "from_addr": settings.SMTP_FROM or settings.SMTP_USER,
        "use_tls": settings.SMTP_USE_TLS,
    }


async def send_email(to_email: str, subject: str, body: str) -> bool:
    smtp = await get_smtp_config()
    if not smtp["host"] or not smtp["user"]:
        return False

    msg = MIMEMultipart("alternative")
    msg["From"] = smtp["from_addr"]
    msg["To"] = to_email
    msg["Subject"] = subject
    msg.attach(MIMEText(body, "html", "utf-8"))

    try:
        await aiosmtplib.send(
            msg,
            hostname=smtp["host"],
            port=smtp["port"],
            username=smtp["user"],
            password=smtp["password"],
            use_tls=smtp["use_tls"],
        )
        return True
    except Exception:
        return False


def build_repayment_reminder_html(
    nickname: str, creditor: str, amount_yuan: float,
    due_date: str, days_left: int, is_overdue: bool = False
) -> str:
    status_text = f"已逾期 {abs(days_left)} 天" if is_overdue else f"还有 {days_left} 天到期"
    color = "#ff3b30" if is_overdue else "#0071e3"
    title = "逾期提醒" if is_overdue else "还款提醒"
    return f"""
    <div style="font-family:-apple-system,sans-serif;max-width:480px;margin:0 auto;padding:32px">
      <h2 style="color:{color};margin-bottom:16px">{title}</h2>
      <p>Hi {nickname}，</p>
      <p>您有一笔借款即将到期：</p>
      <div style="background:#f5f5f7;border-radius:12px;padding:20px;margin:16px 0">
        <p><strong>债权人：</strong>{creditor}</p>
        <p><strong>金额：</strong>¥{amount_yuan:,.2f}</p>
        <p><strong>到期日：</strong>{due_date}</p>
        <p style="color:{color};font-weight:600">{status_text}</p>
      </div>
      <p style="color:#6e6e73;font-size:13px">—— 债务管理系统</p>
    </div>
    """


_LOGIN_ALERT_CONFIG = {
    3: {
        "level": "注意",
        "color": "#ff9500",
        "bg": "rgba(255,149,0,.06)",
        "border": "rgba(255,149,0,.15)",
        "icon": "⚠️",
        "desc": "您的账号出现了异常登录尝试。",
    },
    5: {
        "level": "警告",
        "color": "#ff6b35",
        "bg": "rgba(255,107,53,.06)",
        "border": "rgba(255,107,53,.15)",
        "icon": "🔶",
        "desc": "您的账号正遭受多次暴力破解尝试，若非本人操作请立即修改密码。",
    },
    10: {
        "level": "严重",
        "color": "#ff3b30",
        "bg": "rgba(255,59,48,.08)",
        "border": "rgba(255,59,48,.18)",
        "icon": "🔴",
        "desc": "您的账号已被暴力破解锁定 5 分钟。若非本人操作，请立即修改密码并检查账户安全。",
    },
}


def _build_login_alert_html(nickname: str, count: int, threshold: int, ip: str, site_url: str, token: str, uid: int, ttl_minutes: int = 5) -> str:
    cfg = _LOGIN_ALERT_CONFIG[threshold]
    change_pwd_url = f"{site_url}/reset-password.html?token={token}&uid={uid}"
    return f"""
    <div style="font-family:-apple-system,sans-serif;max-width:480px;margin:0 auto;padding:32px">
      <h2 style="color:{cfg['color']};margin-bottom:16px">{cfg['icon']} 登录安全{cfg['level']}</h2>
      <p>Hi {nickname}，</p>
      <p>{cfg['desc']}</p>
      <div style="background:{cfg['bg']};border:1px solid {cfg['border']};border-radius:12px;padding:20px;margin:16px 0">
        <p><strong>异常登录次数：</strong><span style="color:{cfg['color']};font-weight:700">{count} 次</span></p>
        <p><strong>触发来源 IP：</strong>{ip}</p>
        <p><strong>时间：</strong>{__import__('datetime').datetime.now().strftime('%Y-%m-%d %H:%M:%S')}</p>
      </div>
      <div style="text-align:center;margin:24px 0">
        <a href="{change_pwd_url}" style="display:inline-block;padding:12px 32px;background:#0071e3;color:#fff;border-radius:8px;text-decoration:none;font-weight:600">修改密码</a>
      </div>
      <p style="color:#6e6e73;font-size:12px">此链接 {ttl_minutes} 分钟内有效，仅可使用一次。</p>
      <p style="color:#6e6e73;font-size:13px">如非本人操作，请忽略此邮件并尽快检查账户安全。</p>
      <p style="color:#6e6e73;font-size:13px">—— 债务管理系统</p>
    </div>
    """


async def send_login_alert_email(user, count: int, threshold: int, ip: str):
    if not user.real_email:
        return
    import secrets
    from datetime import datetime, timedelta

    token = secrets.token_urlsafe(32)
    ttl_minutes = 5
    expires_at = (datetime.utcnow() + timedelta(minutes=ttl_minutes)).isoformat()
    key = f"pwd_reset:{user.id}"
    value = f"{token}|{expires_at}"

    async with async_session() as db:
        result = await db.execute(select(SystemSetting).where(SystemSetting.key == key))
        setting = result.scalar_one_or_none()
        if setting:
            setting.value = value
        else:
            db.add(SystemSetting(key=key, value=value))
        await db.commit()

    cfg = _LOGIN_ALERT_CONFIG[threshold]
    site_url = await get_site_url()
    html = _build_login_alert_html(user.nickname or user.email, count, threshold, ip, site_url, token, user.id, ttl_minutes)
    subject = f"【{cfg['level']}】账号安全提醒 - 异常登录 {count} 次"
    await send_email(user.real_email, subject, html)


def _build_password_changed_html(nickname: str, action: str, operator: str = "") -> str:
    from datetime import datetime
    now = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    return f"""
    <div style="font-family:-apple-system,sans-serif;max-width:480px;margin:0 auto;padding:32px">
      <h2 style="color:#0071e3;margin-bottom:16px">🔐 密码{action}通知</h2>
      <p>Hi {nickname}，</p>
      <p>您的账户密码已被{action}。</p>
      <div style="background:#f5f5f7;border-radius:12px;padding:20px;margin:16px 0">
        <p><strong>操作类型：</strong>密码{action}</p>
        <p><strong>操作时间：</strong>{now}</p>
        {"<p><strong>操作人：</strong>" + operator + "</p>" if operator else ""}
      </div>
      <p style="color:#6e6e73;font-size:13px">如非本人操作，请立即联系管理员并修改密码。</p>
      <p style="color:#6e6e73;font-size:13px">—— 债务管理系统</p>
    </div>
    """


async def send_password_changed_email(user, action: str, operator: str = ""):
    if not user.real_email:
        return
    html = _build_password_changed_html(user.nickname or user.email, action, operator)
    subject = f"【安全通知】您的密码已被{action}"
    await send_email(user.real_email, subject, html)


def _build_password_reset_link_html(nickname: str, reset_url: str, ttl_hours: int, operator: str) -> str:
    from datetime import datetime
    now = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    return f"""
    <div style="font-family:-apple-system,sans-serif;max-width:480px;margin:0 auto;padding:32px">
      <h2 style="color:#0071e3;margin-bottom:16px">🔐 密码重置链接</h2>
      <p>Hi {nickname}，</p>
      <p>管理员已为您发起密码重置，请点击下方按钮设置新密码。</p>
      <div style="background:#f5f5f7;border-radius:12px;padding:20px;margin:16px 0">
        <p><strong>操作人：</strong>{operator}</p>
        <p><strong>发送时间：</strong>{now}</p>
        <p><strong>有效期：</strong>{ttl_hours} 小时内有效</p>
      </div>
      <div style="text-align:center;margin:24px 0">
        <a href="{reset_url}" style="display:inline-block;padding:14px 36px;background:#0071e3;color:#fff;border-radius:8px;text-decoration:none;font-weight:600;font-size:15px">重置密码</a>
      </div>
      <p style="color:#6e6e73;font-size:12px">如非本人操作，请忽略此邮件。</p>
      <p style="color:#6e6e73;font-size:13px">—— 债务管理系统</p>
    </div>
    """


async def send_password_reset_link_email(user, reset_url: str, ttl_hours: int, operator: str = ""):
    if not user.real_email:
        return
    html = _build_password_reset_link_html(user.nickname or user.email, reset_url, ttl_hours, operator)
    subject = "【密码重置】管理员为您重置了密码"
    await send_email(user.real_email, subject, html)