From 8ae429ac54dc5921c9e3e7d24071d41da4e1a396 Mon Sep 17 00:00:00 2001
From: Martin Berg Alstad <git@martials.no>
Date: Sat, 20 Sep 2025 12:39:56 +0200
Subject: [PATCH] Implement create Icalendar endpoint

---
 src/main.rs | 70 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 58 insertions(+), 12 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index ce09d36..d0d41f2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,10 +1,12 @@
 use axum::extract::Query;
-use axum::response::IntoResponse;
+use axum::http::header::CONTENT_TYPE;
+use axum::response::{IntoResponse, Response};
 use axum::routing::get;
 use axum::{Json, Router};
 use chrono::{Datelike, Months, NaiveDate, NaiveDateTime, TimeDelta, Weekday};
-use serde::{Deserialize, Serialize};
-use std::ops::{Add, Sub};
+use icalendar::{Calendar, Class, Component, Event, EventLike};
+use serde::Deserialize;
+use std::ops::Sub;
 
 #[derive(Deserialize)]
 enum Recurring {
@@ -68,24 +70,66 @@ struct EventBody {
 /// TODO what if start_date is weekend
 async fn get_calendar(Query(query): Query<EventQuery>) -> impl IntoResponse {
     let start = query.start_date_time;
-    let start_day = start.day();
     let end = query
         .end_date
         .unwrap_or_else(|| (start + TimeDelta::days(365)).date());
+    Json(get_dates(
+        start,
+        end,
+        query.recurring,
+        query.avoid_weekends.unwrap_or(false),
+    ))
+}
 
+const TEXT_CALENDAR: &'static str = "text/calendar";
+
+async fn get_ics(Query(query): Query<EventQuery>) -> impl IntoResponse {
+    let start = query.start_date_time;
+    let end = query
+        .end_date
+        .unwrap_or_else(|| (start + TimeDelta::days(365)).date());
+    let mut calendar = Calendar::new();
+    calendar.name(&query.title);
+    get_dates(
+        start,
+        end,
+        query.recurring,
+        query.avoid_weekends.unwrap_or(false),
+    )
+    .into_iter()
+    .for_each(|date| {
+        calendar.push(
+            Event::new()
+                .summary(&query.title)
+                .starts(date)
+                .class(Class::Confidential),
+        );
+    });
+
+    Response::builder()
+        .header(CONTENT_TYPE, TEXT_CALENDAR)
+        .body(calendar.done().to_string())
+        .unwrap()
+}
+
+fn get_dates(
+    start: NaiveDateTime,
+    end: NaiveDate,
+    recurring: Recurring,
+    avoid_weekends: bool,
+) -> Vec<NaiveDateTime> {
     let mut events = vec![start];
     let mut previous_date_time = start;
+    let mut baseline = start;
     while previous_date_time.date() < end {
-        previous_date_time = previous_date_time.with_day(start_day).unwrap();
-        let next = match query.recurring {
+        let next = match recurring {
             Recurring::Daily => todo!(),
             Recurring::Weeky => todo!(),
             Recurring::BiWeekly => todo!(),
             Recurring::Monthly => {
-                let new_date = previous_date_time
-                    .checked_add_months(Months::new(1))
-                    .unwrap();
-                if let Some(true) = query.avoid_weekends {
+                let new_date = baseline.checked_add_months(Months::new(1)).unwrap();
+                baseline = new_date;
+                if let true = avoid_weekends {
                     match new_date.weekday() {
                         Weekday::Sat => new_date.sub(TimeDelta::days(1)),
                         Weekday::Sun => new_date.sub(TimeDelta::days(2)),
@@ -101,12 +145,14 @@ async fn get_calendar(Query(query): Query<EventQuery>) -> impl IntoResponse {
         events.push(next);
         previous_date_time = next;
     }
-    Json(events)
+    events
 }
 
 #[tokio::main]
 async fn main() {
-    let app = Router::new().route("/", get(get_calendar));
+    let app = Router::new()
+        .route("/", get(get_calendar))
+        .route("/ics", get(get_ics));
 
     let listener = tokio::net::TcpListener::bind("0.0.0.0:8000").await.unwrap();
     axum::serve(listener, app).await.unwrap();