"""邮件模板渲染。"""

from __future__ import annotations

import html
import re

from .system_settings import (
    APP_NAME,
    DEFAULT_EMAIL_TEST_BODY,
    DEFAULT_EMAIL_TEST_HTML,
    DEFAULT_EMAIL_TEST_SUBJECT,
    DEFAULT_EMAIL_VERIFY_BODY,
    DEFAULT_EMAIL_VERIFY_HTML,
    DEFAULT_EMAIL_VERIFY_SUBJECT,
    DEFAULT_PASSWORD_RESET_BODY,
    DEFAULT_PASSWORD_RESET_HTML,
    DEFAULT_PASSWORD_RESET_SUBJECT,
    SystemSettingsData,
)

_TEMPLATE_VAR_PATTERN = re.compile(r"\{(\w+)\}")


def render_email_template(template: str, **context: str) -> str:
    """安全渲染邮件模板，未知占位符保留原样。"""
    value = template or ""

    def replacer(match: re.Match) -> str:
        key = match.group(1)
        return context.get(key, match.group(0))

    return _TEMPLATE_VAR_PATTERN.sub(replacer, value)


def _text_to_html(text: str) -> str:
    escaped = html.escape(text or "")
    return f'<pre style="font-family:sans-serif;white-space:pre-wrap;margin:0;">{escaped}</pre>'


def build_verify_email_content(
    settings: SystemSettingsData,
    username: str,
    to_email: str,
    link: str,
) -> tuple[str, str, str]:
    context = {
        "username": username,
        "email": to_email,
        "link": link,
        "app_name": APP_NAME,
    }
    subject_tpl = settings.email_verify_subject or DEFAULT_EMAIL_VERIFY_SUBJECT
    body_tpl = settings.email_verify_body or DEFAULT_EMAIL_VERIFY_BODY
    html_tpl = settings.email_verify_html or ""

    subject = render_email_template(subject_tpl, **context)
    text_body = render_email_template(body_tpl, **context)
    if html_tpl.strip():
        html_body = render_email_template(html_tpl, **context)
    else:
        html_body = _text_to_html(text_body)
    return subject, text_body, html_body


def build_password_reset_content(
    settings: SystemSettingsData,
    username: str,
    to_email: str,
    link: str,
    expire_hours: int,
) -> tuple[str, str, str]:
    context = {
        "username": username,
        "email": to_email,
        "link": link,
        "app_name": APP_NAME,
        "expire_hours": str(expire_hours),
    }
    subject = render_email_template(DEFAULT_PASSWORD_RESET_SUBJECT, **context)
    text_body = render_email_template(DEFAULT_PASSWORD_RESET_BODY, **context)
    html_body = render_email_template(DEFAULT_PASSWORD_RESET_HTML, **context)
    return subject, text_body, html_body


def build_test_email_content(settings: SystemSettingsData, to_email: str) -> tuple[str, str, str]:
    context = {
        "username": "测试用户",
        "email": to_email,
        "link": settings.app_url_normalized(),
        "app_name": APP_NAME,
    }
    subject_tpl = settings.email_test_subject or DEFAULT_EMAIL_TEST_SUBJECT
    body_tpl = settings.email_test_body or DEFAULT_EMAIL_TEST_BODY
    html_tpl = settings.email_test_html or ""

    subject = render_email_template(subject_tpl, **context)
    text_body = render_email_template(body_tpl, **context)
    if html_tpl.strip():
        html_body = render_email_template(html_tpl, **context)
    else:
        html_body = _text_to_html(text_body)
    return subject, text_body, html_body