From e0bf354bb6301761146d3025bdc6176c33877790 Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Sat, 4 Dec 2021 18:39:21 -0700
Subject: disambiguate pending vs fucked ETA

---
 src/history.rs | 24 +++++++++++++++---------
 src/lib.rs     | 11 ++++++++---
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/history.rs b/src/history.rs
index 5216d10..f8ffec2 100644
--- a/src/history.rs
+++ b/src/history.rs
@@ -13,6 +13,11 @@ pub struct History {
     data: Vec<Reading>,
 }
 
+pub enum NoETA {
+    Pending,
+    Fuck,
+}
+
 impl History {
     pub fn record(&mut self, queue_size: u32) {
         self.data.push(Reading {
@@ -21,30 +26,31 @@ impl History {
         });
     }
 
-    pub fn completion_time(&self) -> Option<js_sys::Date> {
+    pub fn completion_time(&self) -> Result<js_sys::Date, NoETA> {
         // TODO make this not suck
         let &Reading {
             time: first_time,
             queue_size: first_size,
             ..
-        } = self.data.first()?;
+        } = self.data.first().ok_or(NoETA::Pending)?;
         let &Reading {
             time: last_time,
             queue_size: last_size,
-        } = self.data.last()?;
+        } = self.data.last().ok_or(NoETA::Pending)?;
         let overall_time_elapsed = last_time - first_time;
         if overall_time_elapsed.is_zero() {
-            return None;
-        }
-        let overall_queue_motion = first_size - last_size;
-        if overall_queue_motion == 0 {
-            return None;
+            return Err(NoETA::Pending);
         }
+        let overall_queue_motion = match first_size.checked_sub(last_size) {
+            Some(0) => return Err(NoETA::Pending),
+            Some(x) => x,
+            None => return Err(NoETA::Fuck),
+        };
         let duration_per_step = overall_time_elapsed / overall_queue_motion as i32;
         let remaining_duration = duration_per_step * last_size as i32;
         let completion_time = last_time + remaining_duration;
         let completion_time_gmt = completion_time.timestamp_millis();
-        Some(js_sys::Date::new(&JsValue::from(
+        Ok(js_sys::Date::new(&JsValue::from(
             completion_time_gmt as f64,
         )))
     }
diff --git a/src/lib.rs b/src/lib.rs
index bb0fc76..74d4be9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -13,6 +13,8 @@ use web_sys::*;
 mod history;
 mod ocr;
 
+use history::{History, NoETA};
+
 // When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
 // allocator.
 #[cfg(feature = "wee_alloc")]
@@ -110,7 +112,7 @@ async fn do_boot() {
 
     let document = gloo::utils::document();
 
-    let history = Rc::new(RefCell::new(history::History::default()));
+    let history = Rc::new(RefCell::new(History::default()));
 
     let (manual_update_tx, manual_update_rx) = mpsc::channel::<()>(5);
 
@@ -252,7 +254,7 @@ async fn do_boot() {
                                     history.record(queue_size);
                                     let estimated_finish = history.completion_time();
                                     let eta_text = match estimated_finish {
-                                        Some(finish) => {
+                                        Ok(finish) => {
                                             let empty_array = js_sys::Array::new();
                                             let options = {
                                                 let kv_pair = js_sys::Array::new();
@@ -271,7 +273,10 @@ async fn do_boot() {
                                                 format.call1(&JsValue::UNDEFINED, &finish).unwrap();
                                             locale_string.as_string().unwrap()
                                         }
-                                        None => format!("pending"),
+                                        Err(NoETA::Pending) => format!("pending"),
+                                        Err(NoETA::Fuck) => {
+                                            format!("fucked (try reloading i guess?)")
+                                        }
                                     };
                                     let label = format!(" - ETA {}", eta_text);
                                     eta.set_inner_text(&label);
-- 
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