"""TRMNL e-ink display feed.

Serves today's jokes in the JSON shape TRMNL's Private Plugin "polling"
strategy expects, so a device can render them with the TRMNL design system.

Polling URL: https://wiki-jokes.obahan.xyz/trmnl.json
If TRMNL_TOKEN is set, the device must send it as ?token=*** header
(polling headers: trmnl-token=<token>).
"""
import os

from fastapi import Request
from fastapi.responses import JSONResponse

from . import db
from .generator import today_local

REFRESH_INTERVAL_SECONDS = 900  # jokes only change once a day; match TRMNL cadence


def _batch():
    """Today's batch, falling back to the latest available (stale flag set)."""
    day = today_local()
    batch = db.get_day(day)
    stale = False
    if batch is None:
        batch = db.get_latest()
        stale = True
    return batch, stale


def payload(batch: dict, stale: bool) -> dict:
    return {
        "refresh_interval": REFRESH_INTERVAL_SECONDS,
        "day": batch["day"],
        "stale": stale,
        "article_title": batch["article_title"],
        "article_url": batch["article_url"],
        "jokes": [{"text": j} for j in batch["jokes"]],
    }


def trmnl_endpoint(request: Request):
    token = os.environ.get("TRMNL_TOKEN", "")
    if token:
        supplied = request.query_params.get("token") or request.headers.get("trmnl-token")
        if supplied != token:
            return JSONResponse({"error": "unauthorized"}, status_code=403)
    batch, stale = _batch()
    if batch is None:
        # Keep the last screen on the device instead of blanking it.
        return JSONResponse(
            {"status": "no_data", "refresh_interval": REFRESH_INTERVAL_SECONDS},
            status_code=204,
        )
    return JSONResponse(payload(batch, stale))