recurring-event-api/src/main.rs

use axum::extract::Query;
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 icalendar::{Calendar, Class, Component, Event, EventLike};
use serde::Deserialize;
use std::ops::Sub;

const TEXT_CALENDAR: &'static str = "text/calendar";

#[derive(Deserialize)]
enum Recurring {
    Daily,
    Weeky,
    BiWeekly,
    Monthly,
    Quarterly,
    Yearly,
}

#[derive(Deserialize)]
enum Move {
    Before,
    After,
}

#[derive(Deserialize)]
struct EventQuery {
    /// Start date
    start_date_time: NaiveDateTime,
    /// Recurring date
    recurring: Recurring,
    // If set, will ignore time on start_date
    all_day: bool,
    /// Title of the event
    title: String,
    // Optionals
    end_date: Option<NaiveDate>,
    avoid_weekends: Option<bool>,
    on_collition: Option<Move>,
}

#[derive(Deserialize)]
enum Time {
    /// Specific time at day
    DateTime {
        start: NaiveDateTime,
        end: NaiveDateTime,
    },
    /// All day
    Date(NaiveDate),
}

#[derive(Deserialize)]
struct EventBody {
    /// Start date
    time: Time,
    /// Recurring date
    recurring: Recurring,
    /// Title of the event
    title: String,
    // Optionals
    end_date: Option<NaiveDate>,
    ignore_weekdays: Vec<Weekday>,
    on_collition: Option<Move>,
}

/// TODO create ical object
/// TODO implement Before / After
/// TODO what if start_date is weekend
async fn get_calendar(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());
    Json(get_dates(
        start,
        end,
        query.recurring,
        query.avoid_weekends.unwrap_or(false),
    ))
}

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_time| {
        let mut event = Event::new();
        if query.all_day {
            event.all_day(date_time.date());
        } else {
            event.starts(date_time);
        };
        event.summary(&query.title).class(Class::Private);
        calendar.push(event);
    });

    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 {
        let next = match recurring {
            Recurring::Daily => todo!(),
            Recurring::Weeky => todo!(),
            Recurring::BiWeekly => todo!(),
            Recurring::Monthly => {
                baseline = baseline.checked_add_months(Months::new(1)).unwrap();
                if let true = avoid_weekends {
                    match baseline.weekday() {
                        Weekday::Sat => baseline.sub(TimeDelta::days(1)),
                        Weekday::Sun => baseline.sub(TimeDelta::days(2)),
                        _ => baseline,
                    }
                } else {
                    baseline
                }
            }
            Recurring::Quarterly => todo!(),
            Recurring::Yearly => todo!(),
        };
        events.push(next);
        previous_date_time = next;
    }
    events
}

#[tokio::main]
async fn main() {
    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();
}