import { Database, Datum, dataEnd, dataStart, day, hour, week } from "./data";

/**
 * This fake server mimics how a real server api chart service may get and format data for charts. If you are a
 * frontend developer you can safely ignore this part of the example.
 */
export const FakeServer = {
  get: async function (params: { windowStart?: Date; windowEnd?: Date }) {
    // Simulate a real server with a random 2000-2500ms delay
    const delayTime = 2000 + Math.floor(Math.random() * 500);
    await delay(delayTime);

    // Fetch the data from the fake database
    const data = Database.get();

    // Format the data ready for the chart
    const formattedData = formatData(
      data,
      params.windowStart?.getTime() ?? dataStart,
      params.windowEnd?.getTime() ?? dataEnd,
    );

    return formattedData;
  },
};

function delay(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function formatData(data: Datum[], windowStart: number, windowEnd: number) {
  const diff = windowEnd - windowStart;
  let granularity = week * 4;
  if (diff < week * 2) {
    granularity = hour;
  } else if (diff < week * 13) {
    granularity = day;
  } else if (diff < week * 52) {
    granularity = week;
  }
  return data.filter(({ time }) => {
    const isCoarse = (time - dataStart) % (week * 4) === 0;
    const isFineWithinWindow =
      (time - dataStart) % granularity === 0 &&
      time >= windowStart &&
      time <= windowEnd;
    return isCoarse || isFineWithinWindow;
  });
}