"""Templates: saved replies, inserted from the compose window's More menu."""

from __future__ import annotations

import datetime as dt
import uuid
from typing import Annotated

import nh3
from fastapi import APIRouter, Depends
from pydantic import BaseModel, Field
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.errors import raise_api_error
from app.db import get_session
from app.identity.deps import CurrentUser, require_csrf
from app.models import MailTemplate

router = APIRouter(prefix="/templates", tags=["compose"], dependencies=[Depends(require_csrf)])

DbSession = Annotated[AsyncSession, Depends(get_session)]

MAX_TEMPLATES = 200
MAX_BODY_BYTES = 256 * 1024

# What the compose editor writes. A template goes back into the editor as HTML,
# so it is cleaned like any HTML the app renders: no scripts, no handlers.
_TAGS = {
    "a", "b", "blockquote", "br", "code", "div", "em", "font", "h1", "h2", "h3",
    "hr", "i", "img", "li", "ol", "p", "pre", "s", "span", "strike", "strong",
    "sub", "sup", "table", "tbody", "td", "th", "thead", "tr", "u", "ul",
}  # fmt: skip
_GENERIC = {"style", "class", "dir", "align"}
_SPECIFIC = {
    "a": {"href", "title"},
    "img": {"src", "alt", "width", "height"},
    "font": {"color", "face", "size"},
    "td": {"colspan", "rowspan"},
    "th": {"colspan", "rowspan"},
}
# nh3 takes no wildcard: the generic attributes go onto every tag.
_ATTRS = {tag: _GENERIC | _SPECIFIC.get(tag, set()) for tag in _TAGS}


class TemplateOut(BaseModel):
    id: uuid.UUID
    name: str
    subject: str
    body_html: str
    updated_at: dt.datetime


class TemplateIn(BaseModel):
    name: str = Field(min_length=1, max_length=80)
    subject: str = Field(default="", max_length=500)
    body_html: str = ""


def _out(t: MailTemplate) -> TemplateOut:
    return TemplateOut(
        id=t.id, name=t.name, subject=t.subject, body_html=t.body_html, updated_at=t.updated_at
    )


def clean_body(html: str) -> str:
    return nh3.clean(
        html,
        tags=_TAGS,
        attributes=_ATTRS,
        url_schemes={"http", "https", "mailto", "data"},
        link_rel="noopener noreferrer",
    )


@router.get("", response_model=list[TemplateOut])
async def list_templates(user: CurrentUser, db: DbSession) -> list[TemplateOut]:
    rows = await db.scalars(
        select(MailTemplate)
        .where(MailTemplate.user_id == user.id)
        .order_by(func.lower(MailTemplate.name))
    )
    return [_out(t) for t in rows]


@router.post("", response_model=TemplateOut)
async def save_template(body: TemplateIn, user: CurrentUser, db: DbSession) -> TemplateOut:
    """Save a template. Saving under a name that exists replaces that template."""
    name = " ".join(body.name.split())
    if not name:
        raise_api_error(400, "invalid", "a template needs a name")
    if len(body.body_html.encode()) > MAX_BODY_BYTES:
        raise_api_error(400, "too_large", "the template is too large")
    html = clean_body(body.body_html)
    subject = " ".join(body.subject.split())
    existing = await db.scalar(
        select(MailTemplate).where(
            MailTemplate.user_id == user.id, func.lower(MailTemplate.name) == name.lower()
        )
    )
    if existing is not None:
        existing.name, existing.subject, existing.body_html = name, subject, html
        existing.updated_at = dt.datetime.now(dt.UTC)
        saved = existing
    else:
        count = await db.scalar(
            select(func.count()).select_from(MailTemplate).where(MailTemplate.user_id == user.id)
        )
        if (count or 0) >= MAX_TEMPLATES:
            raise_api_error(409, "too_many", f"at most {MAX_TEMPLATES} templates")
        saved = MailTemplate(user_id=user.id, name=name, subject=subject, body_html=html)
        db.add(saved)
    await db.commit()
    await db.refresh(saved)
    return _out(saved)


@router.delete("/{template_id}")
async def delete_template(
    template_id: uuid.UUID, user: CurrentUser, db: DbSession
) -> dict[str, str]:
    row = await db.scalar(
        select(MailTemplate).where(MailTemplate.id == template_id, MailTemplate.user_id == user.id)
    )
    if row is None:
        raise_api_error(404, "not_found", "template not found")
    await db.delete(row)
    await db.commit()
    return {"status": "deleted"}