"""Email template management helpers."""
from __future__ import annotations

from dataclasses import dataclass
from typing import Dict, List

from ..database import get_app_settings, update_app_setting
from .. import settings


@dataclass(frozen=True)
class EmailTemplateDefinition:
    """Definition metadata describing an editable email template."""

    id: str
    setting_key: str
    name: str
    description: str
    default_content: str


EMAIL_TEMPLATE_DEFINITIONS: Dict[str, EmailTemplateDefinition] = {
    "newsletter_confirmation": EmailTemplateDefinition(
        id="newsletter_confirmation",
        setting_key="newsletter_confirmation_template",
        name="Newsletter Confirmation",
        description="HTML email sent to subscribers immediately after they confirm their newsletter signup.",
        default_content=getattr(
            settings, "NEWSLETTER_CONFIRMATION_TEMPLATE", "").strip(),
    ),
}


def list_templates() -> List[dict]:
    """Return a list of metadata describing available email templates."""
    return [
        {
            "id": definition.id,
            "name": definition.name,
            "description": definition.description,
        }
        for definition in EMAIL_TEMPLATE_DEFINITIONS.values()
    ]


def _load_stored_templates() -> dict:
    """Return stored template values keyed by their setting key."""
    return get_app_settings()


def load_template(template_id: str) -> dict:
    """Return template metadata and content for the requested template."""
    if template_id not in EMAIL_TEMPLATE_DEFINITIONS:
        raise KeyError(template_id)

    definition = EMAIL_TEMPLATE_DEFINITIONS[template_id]
    stored = _load_stored_templates()
    content = stored.get(definition.setting_key, definition.default_content)

    return {
        "id": definition.id,
        "name": definition.name,
        "description": definition.description,
        "content": content,
    }


def persist_template(template_id: str, content: str) -> dict:
    """Persist template content and return the updated template payload."""
    if template_id not in EMAIL_TEMPLATE_DEFINITIONS:
        raise KeyError(template_id)

    definition = EMAIL_TEMPLATE_DEFINITIONS[template_id]
    content = (content or "").strip()
    update_app_setting(definition.setting_key, content)
    return load_template(template_id)


def get_template_content(template_id: str) -> str:
    """Return just the template body, falling back to defaults when unset."""
    if template_id not in EMAIL_TEMPLATE_DEFINITIONS:
        raise KeyError(template_id)

    definition = EMAIL_TEMPLATE_DEFINITIONS[template_id]
    stored = _load_stored_templates()
    return stored.get(definition.setting_key, definition.default_content)