make it blazingly fast with caching of css and js

build.rs

@@ -1,6 +1,29 @@
+use std::path::PathBuf;
+
+use sha2::Digest;
+
 fn main() {
     // Always rerun.
 
+    let index_css = include_str!("static/index.css");
+    let index_js = include_str!("static/index.js");
+
+    let index_css_name = get_file_ref("css", index_css);
+    let index_js_name = get_file_ref("js", index_js);
+
+    let out_dir = PathBuf::from(std::env::var("OUT_DIR").unwrap());
+
+    std::fs::write(
+        out_dir.join("revs.rs"),
+        format!(
+            r#"
+pub const INDEX_CSS_NAME: &str = "{index_css_name}";
+pub const INDEX_JS_NAME: &str = "{index_js_name}";
+    "#
+        ),
+    )
+    .unwrap();
+
     let version = if let Ok(commit) = try_get_commit() {
         match has_no_changes() {
             Ok(true) => commit,
@@ -20,6 +43,15 @@ fn main() {
     println!("cargo:rustc-env=GIT_COMMIT_SHORT={version_short}");
 }
 
+fn get_file_ref(ext: &str, content: &str) -> String {
+    let mut hash = sha2::Sha256::new();
+    hash.update(content);
+    let digest = hash.finalize();
+    let rev = bs58::encode(digest).into_string();
+    let rev = &rev[..16];
+    format!("/{rev}.{ext}")
+}
+
 fn try_get_commit() -> color_eyre::Result<String> {
     if let Ok(overridden) = std::env::var("DOES_IT_BUILD_OVERRIDE_VERSION") {
         return Ok(overridden);