[Add] ICal parser

+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 };