const fs = require("fs");

function parseICal(text) {
  const schedules = [];
  let sche = {};
  let reading = false;
  for (const line of text.replace(/\r\n /g, "").split("\r\n")) {
    if (reading) {
      if (line === "END:VEVENT") {
        reading = false;
        schedules.push(sche);
        sche = {};
      } else {
        const i = line.indexOf(":");
        process(sche, line.slice(0, i), line.slice(i + 1));
      }
    } else if (line === "BEGIN:VEVENT") reading = true;
  }
  return schedules;
}

const errArr = [];
function process(sche, k, v) {
  switch (k) {
    case "DTSTAMP":
      k = "CREATED";
      v = dateTimeToDate(v);
      break;
    case "UID":
      v = v.split("-")[2];
      break;
    case "DTSTART":
      k = "START";
      v = dateTimeToDate(v);
      break;
    case "DTEND":
      k = "END";
      v = dateTimeToDate(v);
      break;
    case "DTSTART;VALUE=DATE":
    case "DTEND;VALUE=DATE":
      k = "DATE";
      v = dateToDate(v);
      break;
    case "X-ALT-DESC;FMTTYPE=text/html":
      k = "DETAIL";
      break;
    case "SUMMARY":
      k = "LABEL";
      let b;
      [v, b] = v.split(" [");
      sche["SUBJECT"] = b.substring(0, b.length - 1);
      break;
    case "CLASS":
    case "SEQUENCE":
      return;
    case "DESCRIPTION":
    case "URL":
      break;
    default:
      errArr.push(k);
  }
  sche[k] = v;
}

function insert(str, idxs, char) {
  let nstr = str.substring(0, idxs[0]);
  for (let i = 0; i < idxs.length - 1; i++)
    nstr += char + str.substring(idxs[i], idxs[i + 1]);
  return nstr;
}

function dateTimeToDate(str) {
  const [a, b] = str.split("T");
  return new Date(insert(a, [4, 6, 8], "-") + "T" + insert(b, [2, 4, 6], ":"));
}

function dateToDate(str) {
  return new Date(insert(str, [4, 6, 8], "-"));
}

// let result;
// fs.readFile("C:/Users/teddy/Downloads/data.ics", "utf8", (err, data) => {
//   if (err) console.log(err);
//   else result = parseICal(data);
// });

export { parseICal };