const subDays = require("date-fns/sub_days");
const startOfDay = require("date-fns/start_of_day");
const startOfSecond = require("date-fns/start_of_second");

const StatsAPI = require("../StatsAPI");

function showStats(req, res) {
  let since, until;
  switch (req.query.period) {
    case "last-day":
      until = startOfDay(new Date());
      since = subDays(until, 1);
      break;
    case "last-week":
      until = startOfDay(new Date());
      since = subDays(until, 7);
      break;
    case "last-month":
      until = startOfDay(new Date());
      since = subDays(until, 30);
      break;
    default:
      until = req.query.until
        ? new Date(req.query.until)
        : startOfSecond(new Date());
      since = new Date(req.query.since);
  }

  if (isNaN(since.getTime())) {
    return res.status(403).send({ error: "?since is not a valid date" });
  }

  if (isNaN(until.getTime())) {
    return res.status(403).send({ error: "?until is not a valid date" });
  }

  if (until <= since) {
    return res
      .status(403)
      .send({ error: "?until date must come after ?since date" });
  }

  if (until >= new Date()) {
    return res.status(403).send({ error: "?until must be a date in the past" });
  }

  StatsAPI.getStats(since, until).then(
    stats => {
      res
        .set({
          "Cache-Control": "public, max-age=60",
          "Cache-Tag": "stats"
        })
        .send(stats);
    },
    error => {
      console.error(error);
      res.status(500).send({ error: "Unable to fetch stats" });
    }
  );
}

module.exports = showStats;