feat: add caching to version check with 24h TTL

src/cmd/version.rs

@@ -1,22 +1,72 @@
 use reqwest::blocking::Client;
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::PathBuf;
+use std::time::{SystemTime, UNIX_EPOCH};
 
 pub const VERSION: Option<&'static str> = option_env!("CENV_VERSION");
 
+const CACHE_TTL_SECS: u64 = 86400; // 24 hours
+
 #[derive(Debug, Deserialize)]
 struct VersionInfo {
     tag_name: String,
 }
 
+#[derive(Debug, Serialize, Deserialize)]
+struct VersionCache {
+    time: u64,
+    tag_name: String,
+}
+
 pub fn check_latest_version_and_warn() {
     let _ = try_check_latest_version();
 }
 
+fn cache_path() -> PathBuf {
+    std::env::temp_dir().join("cenv_version_check")
+}
+
+fn now_secs() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0)
+}
+
+fn read_cache() -> Option<VersionCache> {
+    let contents = fs::read_to_string(cache_path()).ok()?;
+    serde_json::from_str(&contents).ok()
+}
+
+fn write_cache(info: &VersionInfo) {
+    let cache = VersionCache {
+        time: now_secs(),
+        tag_name: info.tag_name.clone(),
+    };
+    if let Ok(json) = serde_json::to_string(&cache) {
+        let _ = fs::write(cache_path(), json);
+    }
+}
+
 // Check the latest version of cenv on GitHub and print a warning if the current version is
 // outdated.
 fn try_check_latest_version() -> Option<()> {
     let version = VERSION?;
 
+    if let Some(cache) = read_cache()
+        && now_secs().saturating_sub(cache.time) < CACHE_TTL_SECS
+    {
+        if cache.tag_name != version {
+            eprintln!(
+                "Warning: A new version of cenv is available: {} (current: {})",
+                cache.tag_name, version
+            );
+            eprintln!();
+        }
+        return Some(());
+    }
+
     let client = Client::new();
     let resp = client
         .get("https://api.github.com/repos/echo-webkom/cenv/releases/latest")
@@ -34,5 +84,7 @@ fn try_check_latest_version() -> Option<()> {
         eprintln!();
     }
 
+    write_cache(&info);
+
     Some(())
 }