Implement hashing for CSS filenames

Based on @ashleygwilliams work

Author: skade

.gitignore

@@ -1,9 +1,9 @@
 /target/
 **/*.rs.bk
 /node_modules
-/static/styles/app.css
-/static/styles/fonts.css
 /static/styles/*.map
 .sass-cache
 localhost*
-/static/styles/vendor.css
+/static/styles/vendor_*.css
+/static/styles/app_*.css
+/static/styles/fonts_*.css

Cargo.lock

@@ -21,6 +21,7 @@ toml = "0.4"
 serde_json = "1.0"
 rust_team_data = { git = "https://github.com/rust-lang/team" }
 handlebars = "1.1.0"
+siphasher = "0.2.3"
 
 [dependencies.rocket_contrib]
 version = "*"

Cargo.toml

@@ -9,6 +9,7 @@ extern crate serde_json;
 extern crate rocket;
 extern crate rust_team_data;
 extern crate sass_rs;
+extern crate siphasher;
 extern crate toml;
 
 extern crate rocket_contrib;
@@ -32,8 +33,10 @@ mod teams;
 
 use production::User;
 
+use std::collections::hash_map::DefaultHasher;
 use std::fs;
 use std::fs::File;
+use std::hash::Hasher;
 use std::io::prelude::*;
 use std::iter::FromIterator;
 use std::path::{Path, PathBuf};
@@ -44,6 +47,7 @@ use rocket::{
     http::Status,
     response::{NamedFile, Redirect},
 };
+
 use rocket_contrib::templates::Template;
 
 use sass_rs::{compile_file, Options};
@@ -52,6 +56,20 @@ use category::Category;
 
 use i18n::{I18NHelper, SupportedLocale, TeamHelper};
 
+lazy_static! {
+    static ref CSS: CSSNames = {
+        let app_css_file = compile_sass("app");
+        let fonts_css_file = compile_sass("fonts");
+        let vendor_css_file = concat_vendor_css(vec!["skeleton", "tachyons"]);
+
+        CSSNames {
+            app: app_css_file,
+            fonts: fonts_css_file,
+            vendor: vendor_css_file,
+        }
+    };
+}
+
 #[derive(Serialize)]
 struct Context<T: ::serde::Serialize> {
     page: String,
@@ -61,6 +79,14 @@ struct Context<T: ::serde::Serialize> {
     data: T,
     lang: String,
     baseurl: String,
+    css: CSSNames,
+}
+
+#[derive(Clone, Serialize)]
+struct CSSNames {
+    app: String,
+    fonts: String,
+    vendor: String,
 }
 
 static LAYOUT: &str = "components/layout";
@@ -209,6 +235,7 @@ fn not_found() -> Template {
         data: (),
         lang: ENGLISH.to_string(),
         baseurl: String::new(),
+        css: CSS.clone(),
     };
     Template::render(page, &context)
 }
@@ -218,26 +245,43 @@ fn catch_error() -> Template {
     not_found()
 }
 
-fn compile_sass(filename: &str) {
+fn hash_css(css: &str) -> String {
+    let mut hasher = DefaultHasher::new();
+    hasher.write(css.as_bytes());
+    hasher.finish().to_string()
+}
+
+fn compile_sass(filename: &str) -> String {
     let scss_file = format!("./src/styles/{}.scss", filename);
-    let css_file = format!("./static/styles/{}.css", filename);
 
     let css = compile_file(&scss_file, Options::default())
         .expect(&format!("couldn't compile sass: {}", &scss_file));
+
+    let css_sha = format!("{}_{}", filename, hash_css(&css));
+    let css_file = format!("./static/styles/{}.css", css_sha);
+
     let mut file =
         File::create(&css_file).expect(&format!("couldn't make css file: {}", &css_file));
     file.write_all(&css.into_bytes())
         .expect(&format!("couldn't write css file: {}", &css_file));
+
+    String::from(&css_file[1..])
 }
 
-fn concat_vendor_css(files: Vec<&str>) {
+fn concat_vendor_css(files: Vec<&str>) -> String {
     let mut concatted = String::new();
     for filestem in files {
         let vendor_path = format!("./static/styles/{}.css", filestem);
         let contents = fs::read_to_string(vendor_path).expect("couldn't read vendor css");
         concatted.push_str(&contents);
     }
-    fs::write("./static/styles/vendor.css", &concatted).expect("couldn't write vendor css");
+
+    let css_sha = format!("vendor_{}", hash_css(&concatted));
+    let css_path = format!("./static/styles/{}.css", &css_sha);
+
+    fs::write(&css_path, &concatted).expect("couldn't write vendor css");
+
+    String::from(&css_path[1..])
 }
 
 fn render_index(lang: String) -> Template {
@@ -263,6 +307,7 @@ fn render_index(lang: String) -> Template {
         },
         baseurl: baseurl(&lang),
         lang,
+        css: CSS.clone(),
     };
     Template::render(page, &context)
 }
@@ -278,6 +323,7 @@ fn render_category(category: Category, lang: String) -> Template {
         data: (),
         baseurl: baseurl(&lang),
         lang,
+        css: CSS.clone(),
     };
     Template::render(page, &context)
 }
@@ -293,6 +339,7 @@ fn render_production(lang: String) -> Template {
         data: load_users_data(),
         baseurl: baseurl(&lang),
         lang,
+        css: CSS.clone(),
     };
     Template::render(page, &context)
 }
@@ -310,6 +357,7 @@ fn render_governance(lang: String) -> Result<Template, Status> {
                 data,
                 baseurl: baseurl(&lang),
                 lang,
+                css: CSS.clone(),
             };
             Ok(Template::render(page, &context))
         }
@@ -337,6 +385,7 @@ fn render_team(
                 data,
                 baseurl: baseurl(&lang),
                 lang,
+                css: CSS.clone(),
             };
             Ok(Template::render(page, &context))
         }
@@ -368,15 +417,12 @@ fn render_subject(category: Category, subject: String, lang: String) -> Template
         data: (),
         baseurl: baseurl(&lang),
         lang,
+        css: CSS.clone(),
     };
     Template::render(page, &context)
 }
 
 fn main() {
-    compile_sass("app");
-    compile_sass("fonts");
-    concat_vendor_css(vec!["skeleton", "tachyons"]);
-
     let templating = Template::custom(|engine| {
         engine
             .handlebars