Initial Commit

packages/communication/emails/email-processing/src/calendar-parser/calendar-parser.ts

@@ -0,0 +1,115 @@
+import {
+    EMAIL_PROCESSING_CODES,
+    EmailProcessingError,
+} from "../error-codes/error-codes.js";
+import type { CalendarEvent } from "./calendar-parser.types.js";
+
+/** Parse an iCal/ICS string into calendar events. */
+export function parseICalendar(icsContent: string): CalendarEvent[] {
+    if (typeof icsContent !== "string") {
+        throw new EmailProcessingError(
+            EMAIL_PROCESSING_CODES.INVALID_INPUT,
+            "email_processing.invalid_input.ics"
+        );
+    }
+    return parseICalendarInner(icsContent);
+}
+
+function parseICalendarInner(icsContent: string): CalendarEvent[] {
+    const events: CalendarEvent[] = [];
+    const lines = unfoldIcsLines(icsContent);
+
+    let method: string | undefined;
+    const methodLine = lines.find((l) => l.startsWith("METHOD:"));
+    if (methodLine) {
+        method = methodLine.slice("METHOD:".length).trim();
+    }
+
+    let inEvent = false;
+    let current: Partial<CalendarEvent> = {};
+
+    for (const line of lines) {
+        if (line === "BEGIN:VEVENT") {
+            inEvent = true;
+            current =
+                method !== undefined
+                    ? { attendees: [], method }
+                    : { attendees: [] };
+            continue;
+        }
+        if (line === "END:VEVENT") {
+            inEvent = false;
+            const event: CalendarEvent = {
+                // current.attendees is always set by BEGIN:VEVENT above.
+                attendees: current.attendees as string[],
+            };
+            if (current.summary !== undefined) event.summary = current.summary;
+            if (current.description !== undefined)
+                event.description = current.description;
+            if (current.dtStart !== undefined) event.dtStart = current.dtStart;
+            if (current.dtEnd !== undefined) event.dtEnd = current.dtEnd;
+            if (current.location !== undefined)
+                event.location = current.location;
+            if (current.organizer !== undefined)
+                event.organizer = current.organizer;
+            if (current.uid !== undefined) event.uid = current.uid;
+            if (current.method !== undefined) event.method = current.method;
+            events.push(event);
+            continue;
+        }
+        if (!inEvent) continue;
+
+        if (line.startsWith("SUMMARY:")) {
+            current.summary = unescapeIcs(line.slice("SUMMARY:".length));
+        } else if (line.startsWith("DESCRIPTION:")) {
+            current.description = unescapeIcs(
+                line.slice("DESCRIPTION:".length)
+            );
+        } else if (line.startsWith("DTSTART")) {
+            current.dtStart = extractIcsDateTime(line);
+        } else if (line.startsWith("DTEND")) {
+            current.dtEnd = extractIcsDateTime(line);
+        } else if (line.startsWith("LOCATION:")) {
+            current.location = unescapeIcs(line.slice("LOCATION:".length));
+        } else if (line.startsWith("ORGANIZER")) {
+            const org = extractMailto(line);
+            if (org !== undefined) current.organizer = org;
+        } else if (line.startsWith("ATTENDEE")) {
+            const email = extractMailto(line);
+            // current.attendees is always set by BEGIN:VEVENT above.
+            if (email) (current.attendees as string[]).push(email);
+        } else if (line.startsWith("UID:")) {
+            current.uid = line.slice("UID:".length).trim();
+        }
+    }
+
+    return events;
+}
+
+function unfoldIcsLines(content: string): string[] {
+    return content
+        .replace(/\r\n /g, "")
+        .replace(/\r\n\t/g, "")
+        .split(/\r?\n/);
+}
+
+function unescapeIcs(text: string): string {
+    return text
+        .replace(/\\n/g, "\n")
+        .replace(/\\,/g, ",")
+        .replace(/\\;/g, ";")
+        .replace(/\\\\/g, "\\");
+}
+
+function extractIcsDateTime(line: string): string {
+    const colonIdx = line.indexOf(":");
+    if (colonIdx === -1) return "";
+    return line.slice(colonIdx + 1).trim();
+}
+
+function extractMailto(line: string): string | undefined {
+    const match = line.match(/mailto:([^\s;]+)/i);
+    // The regex's capture group always matches when the overall regex
+    // matches, so match[1] is non-undefined here.
+    return match ? match[1] : undefined;
+}