"""Sentence completion for the compose window (app/completion.py)."""

from __future__ import annotations

import datetime as dt
from typing import Annotated

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

from app import completion
from app.db import get_session
from app.identity.deps import CurrentUser, require_csrf
from app.models import CompletionIndexState
from app.queue import enqueue_job

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

DbSession = Annotated[AsyncSession, Depends(get_session)]


class CompletionIn(BaseModel):
    # The text before the cursor (its last line is all that matters). A POST,
    # not a query string: what the user is typing stays out of access logs.
    before: str = Field(max_length=2000)


class CompletionOut(BaseModel):
    suggestion: str | None


@router.post("", response_model=CompletionOut)
async def suggest(body: CompletionIn, user: CurrentUser, db: DbSession) -> CompletionOut:
    before = body.before[-300:]
    built = await db.scalar(
        select(CompletionIndexState.built_at).where(CompletionIndexState.user_id == user.id)
    )
    if built is None or built < dt.datetime.now(dt.UTC) - completion.REBUILD_AFTER:
        # In the background; until it is built, the starter phrases still answer.
        await enqueue_job("build_index_job", str(user.id), _job_id=f"complete:{user.id}")
    personal = await completion.personal_phrases(db, user.id, completion.keys_for(before))
    return CompletionOut(suggestion=completion.complete(personal, before))