import smtplib
from contextlib import contextmanager
from email.message import EmailMessage

from loguru import logger

from ..config.email import EMAIL_CONFIG


class SMTPError(Exception):
    pass


@contextmanager
def smtp_connection():
    """Context manager that yields a connected, authenticated SMTP session."""
    server = smtplib.SMTP(EMAIL_CONFIG.smtp_host, EMAIL_CONFIG.smtp_port)
    try:
        server.starttls()
        server.login(EMAIL_CONFIG.smtp_key, EMAIL_CONFIG.smtp_secret)
        yield server
    finally:
        server.quit()


def send_email(email: EmailMessage) -> None:
    try:
        with smtp_connection() as server:
            server.send_message(email)
    except smtplib.SMTPException as e:
        logger.error(f"Failed to send email: {e}")
        raise SMTPError(f"SMTP error: {e}") from e


def send_batch(emails: list[EmailMessage]) -> int:
    """Send multiple emails over a single SMTP connection."""
    if not emails:
        return 0

    sent = 0
    try:
        with smtp_connection() as server:
            for email in emails:
                try:
                    server.send_message(email)
                    sent += 1
                except smtplib.SMTPException as e:
                    logger.error(f"Failed to send email: {e}")
    except smtplib.SMTPException as e:
        logger.error(f"Failed to establish SMTP connection: {e}")

    return sent


def send_emails(emails: list[EmailMessage]) -> int:
    """Send multiple emails (uses batch connection reuse)."""
    return send_batch(emails)


def chunk_recipients(recipients: list[str], max_per_chunk: int | None = None) -> list[list[str]]:
    max_size = max_per_chunk or EMAIL_CONFIG.max_recipients_per_email
    return [recipients[i:i + max_size] for i in range(0, len(recipients), max_size)]