import os
import smtplib
from email.header import Header
from email.mime.text import MIMEText


def send_email(subject, message, to_email):
    smtp_server = os.getenv("SMTP_HOST")
    smtp_port = int(os.getenv("SMTP_PORT", "25"))
    smtp_user = os.getenv("SMTP_USER")
    smtp_password = os.getenv("SMTP_PASSWORD")

    if not smtp_server or not smtp_user or not smtp_password:
        raise ValueError("SMTP 配置缺失：需要 SMTP_HOST/SMTP_USER/SMTP_PASSWORD（可选 SMTP_PORT）")

    msg = MIMEText(message, "plain", "utf-8")
    msg["From"] = Header(smtp_user)
    msg["To"] = Header(to_email)
    msg["Subject"] = Header(subject)

    server = smtplib.SMTP(smtp_server, smtp_port)
    try:
        server.login(smtp_user, smtp_password)
        server.sendmail(smtp_user, [to_email], msg.as_string())
    finally:
        server.quit()