Add cron parser for start time of a reminder

Cargo.lock

@@ -524,6 +524,15 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "cron-parser"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baa5650eabdaa360e2c240c2a5f544f10185b439cd76d748e44e3f28128a016b"
+dependencies = [
+ "chrono",
+]
+
 [[package]]
 name = "crossbeam-channel"
 version = "0.5.13"
@@ -2619,6 +2628,7 @@ dependencies = [
  "base64 0.22.1",
  "chrono",
  "chrono-tz",
+ "cron-parser",
  "csv",
  "dotenv",
  "env_logger",

Cargo.toml

@@ -35,6 +35,7 @@ serenity = { version = "0.12", default-features = false, features = ["builder",
 oauth2 = "4"
 csv = "1.2"
 sd-notify = "0.4.1"
+cron-parser = "0.10"
 
 [dependencies.extract_derive]
 path = "extract_derive"

src/commands/autocomplete.rs

@@ -3,6 +3,7 @@ use std::time::{SystemTime, UNIX_EPOCH};
 use chrono_tz::TZ_VARIANTS;
 use poise::serenity_prelude::AutocompleteChoice;
 
+use crate::time_parser::cron_next_timestamp;
 use crate::{models::CtxData, time_parser::natural_parser, Context};
 
 pub async fn timezone_autocomplete(ctx: Context<'_>, partial: &str) -> Vec<String> {
@@ -42,7 +43,13 @@ pub async fn time_hint_autocomplete(ctx: Context<'_>, partial: &str) -> Vec<Auto
     if partial.is_empty() {
         vec![AutocompleteChoice::new("Start typing a time...".to_string(), "now".to_string())]
     } else {
-        match natural_parser(partial, &ctx.timezone().await.to_string()).await {
+        let timezone = ctx.timezone().await;
+        let timestamp = match cron_next_timestamp(partial, timezone) {
+            Some(ts) => Some(ts),
+            None => natural_parser(partial, &timezone.to_string()).await,
+        };
+
+        match timestamp {
             Some(timestamp) => match SystemTime::now().duration_since(UNIX_EPOCH) {
                 Ok(now) => {
                     let diff = timestamp - now.as_secs() as i64;

src/models/reminder/mod.rs

@@ -16,7 +16,7 @@ use crate::{
         },
         CtxData,
     },
-    time_parser::natural_parser,
+    time_parser::{cron_next_timestamp, natural_parser},
     utils::{check_guild_subscription, check_subscription},
     Context, Database, Error,
 };
@@ -486,7 +486,10 @@ pub async fn create_reminder(
     let user_data = ctx.author_data().await.unwrap();
     let timezone = timezone.unwrap_or(ctx.timezone().await);
 
-    let time = natural_parser(&time, &timezone.to_string()).await;
+    let time = match cron_next_timestamp(&time, timezone) {
+        Some(ts) => Some(ts),
+        None => natural_parser(&time, &timezone.to_string()).await,
+    };
 
     match time {
         Some(time) => {

src/time_parser.rs

@@ -6,6 +6,8 @@ use std::{
 
 use chrono::{DateTime, Datelike, Timelike, Utc};
 use chrono_tz::Tz;
+use cron_parser::parse;
+use std::str::FromStr;
 use tokio::process::Command;
 
 use crate::consts::{LOCAL_TIMEZONE, PYTHON_LOCATION};
@@ -219,3 +221,7 @@ pub async fn natural_parser(time: &str, timezone: &str) -> Option<i64> {
         })
         .and_then(|inner| if inner < 0 { None } else { Some(inner) })
 }
+
+pub fn cron_next_timestamp(expr: &str, timezone: Tz) -> Option<i64> {
+    parse(expr, &Utc::now().with_timezone(&timezone)).ok().map(|next| next.timestamp() as i64)
+}