2 files changed, 107 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
index 47daed8..6bd2de5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,6 @@
 mod agenda;
 mod discord;
+mod reminder;
 mod slack;
 
 use crate::agenda::AgendaPoint;
diff --git a/src/reminder.rs b/src/reminder.rs
new file mode 100644
index 0000000..20e8fb8
--- /dev/null
+++ b/src/reminder.rs
@@ -0,0 +1,106 @@
+use chrono::{DateTime, Datelike, Duration, Local, NaiveTime, Weekday};
+use serde::{Deserialize, Serialize};
+use std::fs;
+use tokio::sync::watch;
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub enum ReminderType {
+    // Different types of reminders are possible.
+    // e.g. different reminders for the day before and one hour before.
+    Void,
+    OneHour,  //TODO struct instead
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Reminder {
+    reminder_type: ReminderType,
+    last_fire: DateTime<Local>,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct Reminders {
+    reminders: Vec<Reminder>,
+}
+
+impl Reminders {
+    fn write(&self) {
+        fs::write(
+            std::path::Path::new("reminders.json"),
+            serde_json::to_string_pretty(&self).expect("Can't serialize reminders"),
+        )
+        .expect("Can't write reminders.json")
+    }
+}
+
+pub async fn handle(sender: watch::Sender<ReminderType>) {
+    let mut interval = tokio::time::interval(tokio::time::Duration::from_millis(1000));
+
+    let now = Local::now();
+    let next = next_meeting();
+    let mut reminders = read_reminders();
+    for mut reminder in &mut reminders.reminders {
+        match reminder.reminder_type {
+            ReminderType::OneHour => {
+                if in_remind_zone(now, next) && !in_remind_zone(reminder.last_fire, next) {
+                    sender.broadcast(ReminderType::OneHour).unwrap();
+                    reminder.last_fire = now;
+                }
+            },
+            _ => {},
+        }
+    }
+    reminders.write();
+
+    loop {
+        interval.tick().await;
+    }
+}
+
+fn read_reminders() -> Reminders {
+    serde_json::from_str(
+        &fs::read_to_string("reminders.json").expect("Can't read reminders.json")
+    )
+    .expect("Error parsing reminders.json")
+}
+
+fn in_remind_zone(dt: DateTime<Local>, meeting: DateTime<Local>) -> bool {
+    // Wether we're in a "send reminder"-zone.
+    // Currently implemented as "are we 1 hour before?".
+    ((meeting - Duration::hours(1))..meeting).contains(&dt)
+}
+
+fn next_meeting() -> DateTime<Local> {
+    // Check current datetime and calculate when the next meeting is.
+    let now = Local::now();
+    let meeting_time = NaiveTime::from_hms(12, 15, 00);
+    let meeting = match Datelike::weekday(&now) {
+        Weekday::Thu => {
+            // same day as meeting.
+            // next week if meeting has occured.
+            let date_delta = Duration::weeks(
+                if now.time() < meeting_time { 0 } else { 1 }
+            );
+            (now.date() + date_delta).and_time(meeting_time).unwrap()
+        },
+        _ => {
+            let dow_index: i64 = now.date().weekday().num_days_from_monday().into();
+            let date_delta = Duration::days((3 - dow_index).rem_euclid(7));
+            (now.date() + date_delta).and_time(meeting_time).unwrap()
+        },
+    };
+    assert!(meeting.weekday() == Weekday::Thu);
+    meeting
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn in_remind_zone() {
+        let now = Local::now();
+        assert!(super::in_remind_zone(now, now + Duration::minutes(30)));
+        assert!(!super::in_remind_zone(now, now + Duration::hours(2)));
+        assert!(!super::in_remind_zone(now, now - Duration::minutes(30)));
+    }
+}