From 58aa8b249df9029bb4d2d9e2bc987dfbd6eb6d5a Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@harmonic.ai>
Date: Sun, 8 May 2022 00:06:35 -0400
Subject: [PATCH] Support detecting no events, but not sleeping after first
 one.

---
 src/githubctl/github_endpoint_watcher.rs | 46 ++++++++++++++++++------
 src/githubctl/githubctl.rs               |  8 +++--
 src/main.rs                              |  2 +-
 3 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/src/githubctl/github_endpoint_watcher.rs b/src/githubctl/github_endpoint_watcher.rs
index 04abb38..5481ec8 100644
--- a/src/githubctl/github_endpoint_watcher.rs
+++ b/src/githubctl/github_endpoint_watcher.rs
@@ -8,6 +8,7 @@ pub struct GithubEndpointWatcher {
     url: String,
     http_client: reqwest::Client,
     etag: Option<HeaderValue>,
+    last_modified_at: Option<HeaderValue>,
     next_poll_allowed: u64,
     ratelimit_remaining: Option<u64>,
     ratelimit_reset: Option<u64>,
@@ -26,13 +27,16 @@ impl GithubEndpointWatcher {
             url,
             http_client,
             etag: None,
+            last_modified_at: None,
             next_poll_allowed: 0,
             ratelimit_remaining: None,
             ratelimit_reset: None,
         })
     }
 
-    pub async fn get_results(&mut self) -> Result<serde_json::Value, Box<dyn std::error::Error>> {
+    pub async fn get_results(
+        &mut self,
+    ) -> Result<Option<serde_json::Value>, Box<dyn std::error::Error>> {
         let mut request = self
             .http_client
             .get(&self.url)
@@ -40,7 +44,17 @@ impl GithubEndpointWatcher {
             .header("User-Agent", "github_watcher")
             .header("Accept", "application/vnd.github.v3+json");
         if let Some(etag) = &self.etag {
-            request = request.header(reqwest::header::ETAG, etag);
+            let trimmed = etag.to_str()?.trim_matches('"');
+            println!("Setting etag to {}", trimmed);
+            request = request.header(reqwest::header::ETAG, trimmed);
+        }
+        if let Some(last_modified_at) = &self.last_modified_at {
+            // let trimmed = etag.to_str()?.trim_matches('"');
+            println!(
+                "Setting If-Modified-Since to {}",
+                last_modified_at.to_str()?
+            );
+            request = request.header(reqwest::header::IF_MODIFIED_SINCE, last_modified_at);
         }
         self.sleep_until_next_poll().await?;
         self.sleep_until_ratelimit().await?;
@@ -56,16 +70,26 @@ impl GithubEndpointWatcher {
         self.ratelimit_reset = number_header(headers.get("x-ratelimit-reset"))?;
         // let ratelimit_used = headers.get("x-ratelimit-used").map(|x| x.to_owned());
         // let ratelimit_resource = headers.get("x-ratelimit-resource").map(|x| x.to_owned());
+        let last_modified_at = headers
+            .get(reqwest::header::LAST_MODIFIED)
+            .map(|x| x.to_owned());
 
-        let body = response.json::<serde_json::Value>().await?;
-        println!("{}", serde_json::to_string(&body)?);
-        self.etag = etag;
-        let poll_interval_parsed: u64 = poll_interval.unwrap_or_else(|| {
-            println!("No poll interval returned, defaulting to 5 minute polling.");
-            300
-        });
-        self.next_poll_allowed = request_started_at + poll_interval_parsed;
-        Ok(body)
+        if let reqwest::StatusCode::NOT_MODIFIED = response.status() {
+            self.etag = etag;
+            self.last_modified_at = last_modified_at;
+            return Ok(None);
+        } else {
+            let body = response.json::<serde_json::Value>().await?;
+            self.etag = etag;
+            self.last_modified_at = last_modified_at;
+            let poll_interval_parsed: u64 = poll_interval.unwrap_or_else(|| {
+                println!("No poll interval returned, defaulting to 5 minute polling.");
+                300
+            });
+            self.next_poll_allowed = request_started_at + poll_interval_parsed;
+
+            return Ok(Some(body));
+        }
     }
 
     async fn sleep_until_next_poll(&self) -> Result<(), Box<dyn std::error::Error>> {
diff --git a/src/githubctl/githubctl.rs b/src/githubctl/githubctl.rs
index dc408fa..7f54391 100644
--- a/src/githubctl/githubctl.rs
+++ b/src/githubctl/githubctl.rs
@@ -80,18 +80,20 @@ impl<'a> GithubCtl<'a> {
             loop {
                 let api_result = match endpoint_watcher.get_results().await {
                     Ok(result) => result,
-                    Err(_) => {
-                        println!("Failed to get results.");
+                    Err(e) => {
+                        println!("Failed to get results. {}", e);
                         return;
                     }
                 };
-                if let serde_json::Value::Array(events) = api_result {
+                if let Some(serde_json::Value::Array(events)) = api_result {
                     for event in events {
                         if let Err(_) = event_stream.send(event).await {
                             println!("Receiver dropped.");
                             return;
                         }
                     }
+                } else if let None = api_result {
+                    println!("No new results available.");
                 } else {
                     println!("Unsupported JSON type.");
                 }
diff --git a/src/main.rs b/src/main.rs
index 91c387d..aa6141c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,6 +13,6 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     github.watch_repo(ORG, REPO).await?;
     loop {
         let event = github.get_event().await?;
-        println!("{}", serde_json::to_string(&event)?);
+        // println!("{}", serde_json::to_string(&event)?);
     }
 }