"""Отправка сгенерированного отчёта по email через SMTP."""

import email.charset as _charset
import os
import smtplib
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from typing import Dict

from .client import RedmineAPIError
from .config import EmailConfig

# Use 8bit transfer encoding for UTF-8 so non-ASCII text (e.g. Russian)
# appears literally in MIME output instead of base64.
_charset.add_charset("utf-8", _charset.SHORTEST, None, "utf-8")

SMTP_TIMEOUT = 30

MIME_TYPES: Dict[str, str] = {
    ".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    ".odt": "application/vnd.oasis.opendocument.text",
    ".csv": "text/csv",
    ".html": "text/html",
    ".json": "application/json",
    ".md": "text/markdown",
}


def _resolve_mime_type(file_path: str) -> str:
    """Определяет MIME-тип по расширению файла."""
    ext = os.path.splitext(file_path)[1].lower()
    return MIME_TYPES.get(ext, "application/octet-stream")


def build_message(
    email_config: EmailConfig,
    file_path: str,
    author: str,
    period: str,
) -> MIMEMultipart:
    """Формирует MIME-письмо с подстановками и вложением."""
    subject = email_config.subject.replace("{author}", author).replace(
        "{period}", period
    )
    body = email_config.body_text.replace("{author}", author).replace(
        "{period}", period
    )

    msg = MIMEMultipart()
    msg["Subject"] = subject
    msg["From"] = email_config.from_
    msg["To"] = ", ".join(email_config.to)
    if email_config.cc:
        msg["Cc"] = ", ".join(email_config.cc)

    msg.attach(MIMEText(body, "plain", "utf-8"))

    if email_config.attach:
        try:
            with open(file_path, "rb") as fh:
                attachment = MIMEApplication(fh.read())
        except OSError:
            raise RedmineAPIError(
                f"Не удалось прочитать файл отчёта: {file_path}"
            ) from None
        attachment.add_header(
            "Content-Disposition",
            "attachment",
            filename=os.path.basename(file_path),
        )
        mime_type = _resolve_mime_type(file_path)
        attachment.set_type(mime_type)
        msg.attach(attachment)

    return msg


def send_report(
    email_config: EmailConfig,
    file_path: str,
    author: str,
    period: str,
) -> None:
    """Отправляет сгенерированный отчёт по email через SMTP.

    Args:
        email_config: Настройки SMTP и письма.
        file_path: Путь к файлу отчёта для вложения.
        author: Имя автора (для подстановки в тему/тело).
        period: Строка периода (для подстановки в тему/тело).

    Raises:
        RedmineAPIError: При любой ошибке соединения или отправки.
    """
    smtp_cfg = email_config.smtp
    msg = build_message(email_config, file_path, author, period)
    all_recipients = (
        list(email_config.to) + list(email_config.cc) + list(email_config.bcc)
    )

    try:
        with smtplib.SMTP(smtp_cfg.host, smtp_cfg.port, timeout=SMTP_TIMEOUT) as server:
            if smtp_cfg.tls:
                server.starttls()
            if smtp_cfg.user:
                server.login(smtp_cfg.user, smtp_cfg.password)

            server.send_message(
                msg, from_addr=email_config.from_, to_addrs=all_recipients
            )
    except smtplib.SMTPAuthenticationError:
        raise RedmineAPIError(
            "Ошибка аутентификации SMTP. Проверьте логин и пароль."
        ) from None
    except TimeoutError:
        raise RedmineAPIError("Таймаут соединения с SMTP-сервером.") from None
    except smtplib.SMTPException as exc:
        raise RedmineAPIError(f"Ошибка отправки письма: {exc}") from exc
    except OSError as exc:
        raise RedmineAPIError(
            f"Не удалось подключиться к SMTP-серверу {smtp_cfg.host}:{smtp_cfg.port}"
        ) from exc