From bb619b245296424385c2e79bc96a6aa41c4b8073 Mon Sep 17 00:00:00 2001
From: _ <_@_>
Date: Tue, 5 Apr 2022 23:58:28 +0000
Subject: [PATCH] :heavy_plus_sign: offset feature

---
 src/config.rs | 17 +++++++++++++++++
 src/main.rs   | 11 +++++++++--
 src/offset.rs | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 src/offset.rs

diff --git a/src/config.rs b/src/config.rs
index bc647dc..aa73b9c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -7,6 +7,9 @@ type Result <T> = std::result::Result <T, crate::error::Error>;
 pub struct Config {
 	pub interval_secs: u64,
 	pub prompt: String,
+	
+	// Open dev tools in a web browser and run `Math.random () * 2225`
+	pub offset_secs: u64,
 }
 
 impl Default for Config {
@@ -14,6 +17,7 @@ impl Default for Config {
 		Self {
 			interval_secs: 2225,
 			prompt: "Write a journal entry, then hit Tab, Enter to submit it.".into (),
+			offset_secs: 0,
 		}
 	}
 }
@@ -35,6 +39,11 @@ impl Config {
 				let val = u64::from_str (&val).map_err (|_| CannotParseArg ("--interval-secs <u64>"))?;
 				that.interval_secs = val;
 			}
+			else if arg == "--offset-secs" {
+				let val = args.next ().ok_or (ParamNeedsArg ("--offset-secs"))?;
+				let val = u64::from_str (&val).map_err (|_| CannotParseArg ("--offset-secs <u64>"))?;
+				that.offset_secs = val;
+			}
 			else if arg == "--prompt" {
 				let val = args.next ().ok_or (ParamNeedsArg ("--prompt"))?;
 				that.prompt = val;
@@ -44,3 +53,11 @@ impl Config {
 		Ok (that)
 	}
 }
+
+#[cfg (test)]
+mod test {
+	#[test]
+	fn parse () {
+		
+	}
+}
diff --git a/src/main.rs b/src/main.rs
index 5fc7228..dfa56c4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -21,12 +21,13 @@ use tokio::{
 	io::AsyncWriteExt,
 	time::{
 		Duration,
-		interval,
+		interval_at,
 	},
 };
 
 mod config;
 mod error;
+mod offset;
 
 use config::Config;
 use error::Error;
@@ -40,7 +41,13 @@ async fn main () -> Result <(), Error> {
 	let app = app::App::default ();
 	
 	tokio::spawn (async move {
-		let mut i = interval (Duration::from_secs (config.interval_secs));
+		let mut i = interval_at (
+			offset::get_next_tick (
+				config.interval_secs,
+				config.offset_secs,
+			).into (),
+			Duration::from_secs (config.interval_secs),
+		);
 		i.set_missed_tick_behavior (tokio::time::MissedTickBehavior::Skip);
 		
 		loop {
diff --git a/src/offset.rs b/src/offset.rs
new file mode 100644
index 0000000..60fb9ba
--- /dev/null
+++ b/src/offset.rs
@@ -0,0 +1,33 @@
+use std::{
+	time::{
+		Duration,
+		Instant,
+		SystemTime,
+	}
+};
+
+pub fn get_next_tick (interval_secs: u64, offset_secs: u64) -> Instant {
+	let now_sys = SystemTime::now ();
+	let now_mono = Instant::now ();
+	
+	let phase = get_phase (now_sys, interval_secs, offset_secs);
+	now_mono.checked_add (Duration::from_millis (interval_secs * 1000 - u64::try_from (phase).unwrap ())).unwrap ()
+}
+
+fn get_phase (now: SystemTime, interval_secs: u64, offset_secs: u64) -> u64 {
+	let ms_since_epoch = now.duration_since (SystemTime::UNIX_EPOCH).unwrap ().as_millis ();
+	u64::try_from ((ms_since_epoch + u128::from (offset_secs) * 1000) % (u128::from (interval_secs) * 1000)).unwrap ()
+}
+
+#[cfg (test)]
+mod test {
+	use super::*;
+	
+	#[test]
+	fn test () {
+		let now = SystemTime::UNIX_EPOCH.checked_add (Duration::from_secs (1649201544)).unwrap ();
+		
+		assert_eq! (get_phase (now, 2225, 0), 394000);
+		assert_eq! (get_phase (now, 2225, 30), 424000);
+	}
+}