feat: serve Vacationplanner calendar subscriptions

src/calendar.rs

@@ -0,0 +1,90 @@
+use std::collections::BTreeMap;
+
+use chrono::{Datelike, NaiveDate, Utc};
+use icalendar::{Calendar, Class, Component, Event, EventLike, EventStatus};
+use reqwest::Url;
+use serde::Deserialize;
+
+use crate::Error;
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Vacation {
+    id: u64,
+    worker_name: String,
+    date_start: NaiveDate,
+    date_end: NaiveDate,
+    #[serde(default)]
+    department_name: Option<String>,
+    #[serde(default)]
+    comment: Option<String>,
+    #[serde(default)]
+    moderation_status: Option<String>,
+}
+
+fn text(value: &str) -> String {
+    value
+        .replace("\r\n", "\n")
+        .replace('\r', "\n")
+        .chars()
+        .filter(|c| !c.is_control() || *c == '\n' || *c == '\t')
+        .collect()
+}
+
+pub fn render(vacations: Vec<Vacation>, origin: &Url) -> Result<String, Error> {
+    let mut unique = BTreeMap::new();
+    for vacation in vacations {
+        if vacation.id == 0
+            || vacation.worker_name.trim().is_empty()
+            || vacation.date_start > vacation.date_end
+            || !(1..=9998).contains(&vacation.date_start.year())
+            || !(1..=9998).contains(&vacation.date_end.year())
+        {
+            return Err(Error::upstream());
+        }
+        // The same cross-year vacation may be returned by both year endpoints.
+        unique.insert(vacation.id, vacation);
+    }
+    let mut calendar = Calendar::new();
+    calendar.name("Vacationplanner");
+    let timestamp = Utc::now();
+    for vacation in unique.into_values() {
+        // Vacationplanner's final day is inclusive; iCalendar's DTEND is exclusive.
+        let end = vacation.date_end.succ_opt().ok_or_else(Error::upstream)?;
+        let uid = format!(
+            "vacation-{}@{}",
+            vacation.id,
+            origin.origin().ascii_serialization().replace("://", "-")
+        );
+        let mut description = Vec::new();
+        if let Some(department) = vacation.department_name.filter(|value| !value.is_empty()) {
+            description.push(format!("Department: {}", text(&department)));
+        }
+        if let Some(comment) = vacation.comment.filter(|value| !value.is_empty()) {
+            description.push(text(&comment));
+        }
+        let status = match vacation.moderation_status.as_deref() {
+            Some("approved") => Some(EventStatus::Confirmed),
+            Some("on_moderation") => Some(EventStatus::Tentative),
+            Some("rejected") => Some(EventStatus::Cancelled),
+            _ => None,
+        };
+        if let Some(moderation) = vacation.moderation_status {
+            description.push(format!("Moderation: {}", text(&moderation)));
+        }
+        let mut event = Event::new();
+        event
+            .uid(&uid)
+            .timestamp(timestamp)
+            .starts(vacation.date_start)
+            .ends(end)
+            .summary(&format!("{} — Vacation", text(&vacation.worker_name)))
+            .description(&description.join("\n"))
+            .class(Class::Private);
+        if let Some(status) = status {
+            event.status(status);
+        }
+        calendar.push(event);
+    }
+    Ok(calendar.to_string())
+}