From e4d8b14d0b17a709b0f59b0d9beff4b89ebf9bf2 Mon Sep 17 00:00:00 2001
From: Wilson Lin <code@wilsonl.in>
Date: Fri, 8 Jan 2021 00:26:02 +1100
Subject: [PATCH] CSS minification using esbuild

---
 Cargo.toml                                    |  6 +--
 README.md                                     | 15 +++---
 bench/README.md                               |  1 -
 bench/minifiers.js                            | 49 ++++++++++++-------
 bench/minify-html-bench/src/main.rs           |  1 +
 bench/package.json                            |  1 +
 cli/src/main.rs                               |  3 ++
 fuzz/src/main.rs                              |  1 +
 java/pom.xml                                  |  2 +-
 .../in/wilsonl/minifyhtml/Configuration.java  | 12 ++++-
 java/src/main/rust/lib.rs                     |  1 +
 nodejs/binding.c                              | 14 +++++-
 nodejs/index.d.ts                             |  6 ++-
 nodejs/native/src/lib.rs                      |  3 +-
 nodejs/package.json                           |  2 +-
 python/Cargo.toml                             |  2 +-
 python/src/lib.rs                             |  5 +-
 ruby/minify_html.gemspec                      |  2 +-
 ruby/src/lib.rs                               |  4 ++
 src/cfg/mod.rs                                |  5 ++
 src/lib.rs                                    |  5 ++
 src/proc/mod.rs                               | 38 +++++++-------
 src/tests/mod.rs                              | 18 +++++++
 src/unit/script.rs                            |  7 +--
 src/unit/style.rs                             | 45 ++++++++++++++++-
 src/unit/tag.rs                               |  2 +-
 26 files changed, 187 insertions(+), 63 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 19a15ee..3dcb32e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,10 +1,10 @@
 [package]
 name = "minify-html"
-description = "Fast and smart HTML + JS minifier"
+description = "Extremely fast and smart HTML + JS + CSS minifier"
 license = "MIT"
 homepage = "https://github.com/wilsonzlin/minify-html"
 readme = "README.md"
-keywords = ["html", "compress", "minifier", "minify", "minification"]
+keywords = ["html", "compress", "minifier", "js", "css"]
 categories = ["compression", "command-line-utilities", "development-tools::build-utils", "web-programming"]
 repository = "https://github.com/wilsonzlin/minify-html.git"
 version = "0.3.12"
@@ -22,6 +22,6 @@ js-esbuild = ["crossbeam", "esbuild-rs"]
 [dependencies]
 aho-corasick = "0.7"
 crossbeam = { version = "0.7", optional = true }
-esbuild-rs = { version = "0.2.1", optional = true }
+esbuild-rs = { version = "0.8.30", optional = true }
 lazy_static = "1.4"
 memchr = "2"
diff --git a/README.md b/README.md
index 770567e..f71bbab 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Comes with native bindings to Node.js, Python, Java, and Ruby.
 - Advanced minification strategy beats other minifiers with only one pass.
 - Uses zero memory allocations, SIMD searching, direct tries, and lookup tables.
 - Well tested with a large test suite and extensive [fuzzing](./fuzz).
-- Natively binds to [esbuild](https://github.com/wilsonzlin/esbuild-rs) for super fast JS minification.
+- Natively binds to [esbuild](https://github.com/wilsonzlin/esbuild-rs) for super fast JS and CSS minification.
 
 ## Performance
 
@@ -46,9 +46,9 @@ minify-html --src /path/to/src.html --out /path/to/output.min.html
 minify-html = { version = "0.3.12", features = ["js-esbuild"] }
 ```
 
-Building with the `js-esbuild` feature requires the Go compiler to be installed as well, to build the [JS minifier](https://github.com/wilsonzlin/esbuild-rs).
+Building with the `js-esbuild` feature requires the Go compiler to be installed as well, to build the [JS and CSS minifier](https://github.com/wilsonzlin/esbuild-rs).
 
-If the `js-esbuild` feature is not enabled, `cfg.minify_js` will have no effect.
+If the `js-esbuild` feature is not enabled, `cfg.minify_js` and `cfg.minify_css` will have no effect.
 
 ##### Use
 
@@ -82,7 +82,7 @@ yarn add @minify-html/js
 ```js
 const minifyHtml = require("@minify-html/js");
 
-const cfg = minifyHtml.createConfiguration({ minifyJs: false });
+const cfg = minifyHtml.createConfiguration({ minifyJs: false, minifyCss: false });
 const minified = minifyHtml.minify("<p>  Hello, world!  </p>", cfg);
 
 // Alternatively, minify in place to avoid copying.
@@ -97,7 +97,7 @@ minify-html is also available for TypeScript:
 import * as minifyHtml from "@minify-html/js";
 import * as fs from "fs";
 
-const cfg = minifyHtml.createConfiguration({ minifyJs: false });
+const cfg = minifyHtml.createConfiguration({ minifyJs: false, minifyCss: false });
 const minified = minifyHtml.minify("<p>  Hello, world!  </p>", cfg);
 // Or alternatively:
 const minified = minifyHtml.minifyInPlace(fs.readFileSync("source.html"), cfg);
@@ -133,6 +133,7 @@ import in.wilsonl.minifyhtml.SyntaxException;
 
 Configuration cfg = new Configuration.Builder()
     .setMinifyJs(false)
+    .setMinifyCss(false)
     .build();
 
 try {
@@ -165,7 +166,7 @@ Add the PyPI project as a dependency and install it using `pip` or `pipenv`.
 import minify_html
 
 try:
-    minified = minify_html.minify("<p>  Hello, world!  </p>", minify_js=False)
+    minified = minify_html.minify("<p>  Hello, world!  </p>", minify_js=False, minify_css=False)
 except SyntaxError as e:
     print(e)
 ```
@@ -188,7 +189,7 @@ Add the library as a dependency to `Gemfile` or `*.gemspec`.
 ```ruby
 require 'minify_html'
 
-print MinifyHtml.minify("<p>  Hello, world!  </p>", { :minify_js => false })
+print MinifyHtml.minify("<p>  Hello, world!  </p>", { :minify_js => false, :minify_css => false })
 ```
 
 </details>
diff --git a/bench/README.md b/bench/README.md
index e889c23..9cee574 100644
--- a/bench/README.md
+++ b/bench/README.md
@@ -41,7 +41,6 @@ Since speed depends on the input, speed charts show performance relative to the
 
 The settings used for each minifier can be found in [minifiers.js](./minifiers.js). Some settings to note:
 
-- CSS minification is disabled for all, as minify-html currently does not support CSS minification (coming soon).
 - All minifiers are configured to use esbuild for JS minification asynchronously and in parallel, similar to how minify-html works.
 - `conservativeCollapse` is enabled for html-minifier as otherwise some whitespace would be unsafely removed with side effects. minify-html can safely remove whitespace with context if configured properly.
 
diff --git a/bench/minifiers.js b/bench/minifiers.js
index 292a84a..d04a5d8 100644
--- a/bench/minifiers.js
+++ b/bench/minifiers.js
@@ -1,9 +1,10 @@
+const cleanCss = require('clean-css');
 const esbuild = require('esbuild');
 const htmlMinifier = require('html-minifier');
 const minifyHtml = require('@minify-html/js');
 const minimize = require('minimize');
 
-const testJsMinification = process.env.HTML_ONLY !== '1';
+const testJsAndCssMinification = process.env.HTML_ONLY !== '1';
 
 const jsMime = new Set([
   undefined,
@@ -46,7 +47,10 @@ class EsbuildAsync {
   }
 }
 
-const minifyHtmlCfg = minifyHtml.createConfiguration({minifyJs: testJsMinification});
+const minifyHtmlCfg = minifyHtml.createConfiguration({
+  minifyJs: testJsAndCssMinification,
+  minifyCss: testJsAndCssMinification,
+});
 const htmlMinifierCfg = {
   collapseBooleanAttributes: true,
   collapseInlineTagWhitespace: true,
@@ -59,7 +63,8 @@ const htmlMinifierCfg = {
   decodeEntities: true,
   ignoreCustomComments: [],
   ignoreCustomFragments: [/<\?[\s\S]*?\?>/],
-  // This will be set to a function if `testJsMinification` is true.
+  // These will be set later if `testJsAndCssMinification` is true.
+  minifyCSS: false,
   minifyJS: false,
   processConditionalComments: true,
   removeAttributeQuotes: true,
@@ -75,32 +80,42 @@ const htmlMinifierCfg = {
 
 module.exports = {
   '@minify-html/js': (_, buffer) => minifyHtml.minifyInPlace(Buffer.from(buffer), minifyHtmlCfg),
-  'html-minifier': testJsMinification
+  'html-minifier': testJsAndCssMinification
     ? async (content) => {
       const js = new EsbuildAsync();
       const res = htmlMinifier.minify(content, {
         ...htmlMinifierCfg,
+        minifyCSS: true,
         minifyJS: code => js.queue(code),
       });
       return js.finalise(res);
     }
     : content => htmlMinifier.minify(content, htmlMinifierCfg),
-  'minimize': testJsMinification
+  'minimize': testJsAndCssMinification
     ? async (content) => {
       const js = new EsbuildAsync();
-      const plugins = [];
-      if (testJsMinification) {
-        plugins.push({
-          id: 'esbuild',
-          element: (node, next) => {
-            if (node.type === 'text' && node.parent && node.parent.type === 'script' && jsMime.has(node.parent.attribs.type)) {
-              node.data = js.queue(node.data);
-            }
-            next();
+      const css = new cleanCss({
+        level: 2,
+        inline: false,
+        rebase: false,
+      });
+      const res = new minimize({
+        plugins: [
+          {
+            id: 'esbuild',
+            element: (node, next) => {
+              if (node.type === 'text' && node.parent) {
+                if (node.parent.type === 'script' && jsMime.has(node.parent.attribs.type)) {
+                  node.data = js.queue(node.data);
+                } else if (node.parent.type === 'style') {
+                  node.data = css.minify(node.data).styles;
+                }
+              }
+              next();
+            },
           },
-        });
-      }
-      const res = new minimize({plugins}).parse(content);
+        ],
+      }).parse(content);
       return js.finalise(res);
     }
     : content => new minimize().parse(content),
diff --git a/bench/minify-html-bench/src/main.rs b/bench/minify-html-bench/src/main.rs
index 1aa67ae..46fbc5a 100644
--- a/bench/minify-html-bench/src/main.rs
+++ b/bench/minify-html-bench/src/main.rs
@@ -25,6 +25,7 @@ fn main() {
             let mut data = source.to_vec();
             in_place(&mut data, &Cfg {
                 minify_js: false,
+                minify_css: false,
             }).unwrap();
         };
         let elapsed = start.elapsed().as_secs_f64();
diff --git a/bench/package.json b/bench/package.json
index c3eda9d..19fe34b 100644
--- a/bench/package.json
+++ b/bench/package.json
@@ -5,6 +5,7 @@
     "benchmark": "2.1.4",
     "chart.js": "^2.9.3",
     "chartjs-node": "^1.7.1",
+    "clean-css": "^4.2.3",
     "esbuild": "^0.6.5",
     "html-minifier": "4.0.0",
     "minimize": "2.2.0",
diff --git a/cli/src/main.rs b/cli/src/main.rs
index e07e7cc..0ffbedf 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -13,6 +13,8 @@ struct Cli {
     out: Option<std::path::PathBuf>,
     #[structopt(long)]
     js: bool,
+    #[structopt(long)]
+    css: bool,
 }
 
 macro_rules! io_expect {
@@ -38,6 +40,7 @@ fn main() {
     io_expect!(src_file.read_to_end(&mut code), "could not load source code");
     match with_friendly_error(&mut code, &Cfg {
         minify_js: args.js,
+        minify_css: args.css,
     }) {
         Ok(out_len) => {
             let mut out_file: Box<dyn Write> = match args.out {
diff --git a/fuzz/src/main.rs b/fuzz/src/main.rs
index 5808443..c32e02b 100644
--- a/fuzz/src/main.rs
+++ b/fuzz/src/main.rs
@@ -6,6 +6,7 @@ fn main() {
         let mut mut_data: Vec<u8> = data.iter().map(|x| *x).collect();
         let _ = in_place(&mut mut_data, &Cfg {
             minify_js: false,
+            minify_css: false,
         });
     });
 }
diff --git a/java/pom.xml b/java/pom.xml
index a98045f..880e448 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -9,7 +9,7 @@
     <version>0.3.12</version>
 
     <name>minify-html</name>
-    <description>Fast and smart HTML + JS minifier</description>
+    <description>Extremely fast and smart HTML + JS + CSS minifier</description>
     <url>https://github.com/wilsonzlin/minify-html</url>
     <developers>
         <developer>
diff --git a/java/src/main/java/in/wilsonl/minifyhtml/Configuration.java b/java/src/main/java/in/wilsonl/minifyhtml/Configuration.java
index da8bee1..108f828 100644
--- a/java/src/main/java/in/wilsonl/minifyhtml/Configuration.java
+++ b/java/src/main/java/in/wilsonl/minifyhtml/Configuration.java
@@ -5,9 +5,11 @@ package in.wilsonl.minifyhtml;
  */
 public class Configuration {
   private final boolean minifyJs;
+  private final boolean minifyCss;
 
-  public Configuration(boolean minifyJs) {
+  public Configuration(boolean minifyJs, boolean minifyCss) {
     this.minifyJs = minifyJs;
+    this.minifyCss = minifyCss;
   }
 
   /**
@@ -15,14 +17,20 @@ public class Configuration {
    */
   public static class Builder {
     private boolean minifyJs = false;
+    private boolean minifyCss = false;
 
     public Builder setMinifyJs(boolean minifyJs) {
       this.minifyJs = minifyJs;
       return this;
     }
 
+    public Builder setMinifyCss(boolean minifyCss) {
+      this.minifyCss = minifyCss;
+      return this;
+    }
+
     public Configuration build() {
-      return new Configuration(this.minifyJs);
+      return new Configuration(this.minifyJs, this.minifyCss);
     }
   }
 }
diff --git a/java/src/main/rust/lib.rs b/java/src/main/rust/lib.rs
index d67e239..d558678 100644
--- a/java/src/main/rust/lib.rs
+++ b/java/src/main/rust/lib.rs
@@ -12,6 +12,7 @@ fn build_cfg(
 ) -> Cfg {
     Cfg {
         minify_js: env.get_field(*obj, "minifyJs", "Z").unwrap().z().unwrap(),
+        minify_css: env.get_field(*obj, "minifyCss", "Z").unwrap().z().unwrap(),
     }
 }
 
diff --git a/nodejs/binding.c b/nodejs/binding.c
index 33cf264..499163c 100644
--- a/nodejs/binding.c
+++ b/nodejs/binding.c
@@ -96,7 +96,19 @@ napi_value node_method_create_configuration(napi_env env, napi_callback_info inf
     return undefined;
   }
 
-  Cfg const* cfg = ffi_create_cfg(minify_js);
+  // Get `minifyCss` property.
+  napi_value minify_css_value;
+  if (napi_get_named_property(env, obj_arg, "minifyCss", &minify_css_value) != napi_ok) {
+    assert_ok(napi_throw_type_error(env, NULL, "Failed to get minifyCss property"));
+    return undefined;
+  }
+  bool minify_css;
+  if (napi_get_value_bool(env, minify_css_value, &minify_css) != napi_ok) {
+    assert_ok(napi_throw_type_error(env, NULL, "Failed to get minifyCss boolean property"));
+    return undefined;
+  }
+
+  Cfg const* cfg = ffi_create_cfg(minify_js, minify_css);
 
   napi_value js_cfg;
   if (napi_create_external(env, (void*) cfg, js_cfg_finalizer, NULL, &js_cfg) != napi_ok) {
diff --git a/nodejs/index.d.ts b/nodejs/index.d.ts
index 4008002..79f6ec7 100644
--- a/nodejs/index.d.ts
+++ b/nodejs/index.d.ts
@@ -11,7 +11,11 @@ export function createConfiguration (options: {
   /**
    * If enabled, content in `<script>` tags with a JS or no [MIME type](https://mimesniff.spec.whatwg.org/#javascript-mime-type) will be minified using [esbuild-rs](https://github.com/wilsonzlin/esbuild-rs).
    */
-  minifyJs: false;
+  minifyJs: boolean;
+  /**
+   * If enabled, CSS in `<style>` tags will be minified using [esbuild-rs](https://github.com/wilsonzlin/esbuild-rs).
+   */
+  minifyCss: boolean;
 }): Cfg;
 
 /**
diff --git a/nodejs/native/src/lib.rs b/nodejs/native/src/lib.rs
index d4beb71..999bb64 100644
--- a/nodejs/native/src/lib.rs
+++ b/nodejs/native/src/lib.rs
@@ -2,9 +2,10 @@ use std::{mem, ptr, slice};
 use minify_html::{Cfg, Error, in_place};
 
 #[no_mangle]
-pub extern "C" fn ffi_create_cfg(minify_js: bool) -> *const Cfg {
+pub extern "C" fn ffi_create_cfg(minify_js: bool, minify_css: bool) -> *const Cfg {
     Box::into_raw(Box::new(Cfg {
         minify_js,
+        minify_css,
     }))
 }
 
diff --git a/nodejs/package.json b/nodejs/package.json
index 8b57b15..95cfb06 100644
--- a/nodejs/package.json
+++ b/nodejs/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@minify-html/js",
   "version": "0.3.12",
-  "description": "Fast and smart HTML + JS minifier",
+  "description": "Extremely fast and smart HTML + JS + CSS minifier",
   "main": "index.node",
   "types": "index.d.ts",
   "files": [
diff --git a/python/Cargo.toml b/python/Cargo.toml
index 21fdf43..c19e384 100644
--- a/python/Cargo.toml
+++ b/python/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 publish = false
 name = "minify_html"
-description = "Fast and smart HTML + JS minifier"
+description = "Extremely fast and smart HTML + JS + CSS minifier"
 license = "MIT"
 homepage = "https://github.com/wilsonzlin/minify-html"
 readme = "README.md"
diff --git a/python/src/lib.rs b/python/src/lib.rs
index 179a13a..ed935a0 100644
--- a/python/src/lib.rs
+++ b/python/src/lib.rs
@@ -4,11 +4,12 @@ use pyo3::exceptions::PySyntaxError;
 use pyo3::wrap_pyfunction;
 use std::str::from_utf8_unchecked;
 
-#[pyfunction(py_args="*", minify_js="false")]
-fn minify(code: String, minify_js: bool) -> PyResult<String> {
+#[pyfunction(py_args="*", minify_js="false", minify_css="false")]
+fn minify(code: String, minify_js: bool, minify_css: bool) -> PyResult<String> {
     let mut code = code.into_bytes();
     match minify_html_native(&mut code, &Cfg {
         minify_js,
+        minify_css,
     }) {
         Ok(out_len) => Ok(unsafe { from_utf8_unchecked(&code[0..out_len]).to_string() }),
         Err(Error { error_type, position }) => Err(PySyntaxError::new_err(format!("{} [Character {}]", error_type.message(), position))),
diff --git a/ruby/minify_html.gemspec b/ruby/minify_html.gemspec
index 29ec551..dbf9be2 100644
--- a/ruby/minify_html.gemspec
+++ b/ruby/minify_html.gemspec
@@ -7,7 +7,7 @@ Gem::Specification.new do |spec|
   spec.email         = ["code@wilsonl.in"]
   spec.license       = "MIT"
   spec.files         = FileList["lib/*", "README.md"].to_a
-  spec.summary       = "Fast and smart HTML + JS minifier"
+  spec.summary       = "Extremely fast and smart HTML + JS + CSS minifier"
   spec.homepage      = "https://github.com/wilsonzlin/minify_html"
 
   spec.require_paths = ["lib"]
diff --git a/ruby/src/lib.rs b/ruby/src/lib.rs
index 9a304bc..f1a88b2 100644
--- a/ruby/src/lib.rs
+++ b/ruby/src/lib.rs
@@ -20,6 +20,10 @@ methods! {
                 .map(|h| h.at(&Symbol::new("minify_js")))
                 .and_then(|e| e.try_convert_to::<Boolean>())
                 .map_or(false, |v| v.to_bool()),
+            minify_css: cfg_hash
+                .map(|h| h.at(&Symbol::new("minify_css")))
+                .and_then(|e| e.try_convert_to::<Boolean>())
+                .map_or(false, |v| v.to_bool()),
         };
 
         minify_html_native(&mut code, cfg)
diff --git a/src/cfg/mod.rs b/src/cfg/mod.rs
index 7c448a2..92ce04e 100644
--- a/src/cfg/mod.rs
+++ b/src/cfg/mod.rs
@@ -9,4 +9,9 @@ pub struct Cfg {
     /// [MIME type](https://mimesniff.spec.whatwg.org/#javascript-mime-type) is considered to
     /// contain JavaScript, as per the specification.
     pub minify_js: bool,
+
+    /// If enabled, CSS in `<style>` tags are minified using
+    /// [esbuild-rs](https://github.com/wilsonzlin/esbuild-rs). The `js-esbuild` feature must be
+    /// enabled; otherwise, this value has no effect.
+    pub minify_css: bool,
 }
diff --git a/src/lib.rs b/src/lib.rs
index dcb6ba0..7fc4ac5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,6 +31,7 @@ mod unit;
 /// let mut code = b"<p>  Hello, world!  </p>".to_vec();
 /// let cfg = &Cfg {
 ///     minify_js: false,
+///     minify_css: false,
 /// };
 /// match in_place(&mut code, cfg) {
 ///     Ok(minified_len) => assert_eq!(&code, b"<p>Hello, world!d!  </p>"),
@@ -68,6 +69,7 @@ pub fn in_place(code: &mut [u8], cfg: &Cfg) -> Result<usize, Error> {
 /// let mut code = "<p>  Hello, world!  </p>".to_string();
 /// let cfg = &Cfg {
 ///     minify_js: false,
+///     minify_css: false,
 /// };
 /// match in_place_str(&mut code, cfg) {
 ///     Ok(minified_len) => assert_eq!(&code, "<p>Hello, world!d!  </p>"),
@@ -97,6 +99,7 @@ pub fn in_place_str<'s>(code: &'s mut str, cfg: &Cfg) -> Result<&'s str, Error>
 /// let mut code = b"<p>  Hello, world!  </p>".to_vec();
 /// let cfg = &Cfg {
 ///     minify_js: false,
+///     minify_css: false,
 /// };
 /// match truncate(&mut code, cfg) {
 ///     Ok(()) => assert_eq!(code, b"<p>Hello, world!".to_vec()),
@@ -129,6 +132,7 @@ pub fn truncate(code: &mut Vec<u8>, cfg: &Cfg) -> Result<(), Error> {
 /// let mut code: &[u8] = b"<p>  Hello, world!  </p>";
 /// let cfg = &Cfg {
 ///     minify_js: false,
+///     minify_css: false,
 /// };
 /// match copy(&code, cfg) {
 ///     Ok(minified) => {
@@ -167,6 +171,7 @@ pub fn copy(code: &[u8], cfg: &Cfg) -> Result<Vec<u8>, Error> {
 /// let mut code = b"<p></div>".to_vec();
 /// let cfg = &Cfg {
 ///     minify_js: false,
+///     minify_css: false,
 /// };
 /// match with_friendly_error(&mut code, cfg) {
 ///     Ok(minified_len) => {}
diff --git a/src/proc/mod.rs b/src/proc/mod.rs
index 159cb75..d96d0d7 100644
--- a/src/proc/mod.rs
+++ b/src/proc/mod.rs
@@ -52,7 +52,7 @@ pub enum MatchAction {
 }
 
 #[cfg(feature = "js-esbuild")]
-pub struct JsMinSection {
+pub struct EsbuildSection {
     pub src: ProcessorRange,
     pub result: TransformResult,
 }
@@ -65,9 +65,9 @@ pub struct Processor<'d> {
     // Index of the next unwritten space.
     write_next: usize,
     #[cfg(feature = "js-esbuild")]
-    script_wg: WaitGroup,
+    esbuild_wg: WaitGroup,
     #[cfg(feature = "js-esbuild")]
-    script_results: Arc<Mutex<Vec<JsMinSection>>>,
+    esbuild_results: Arc<Mutex<Vec<EsbuildSection>>>,
 }
 
 impl<'d> Index<ProcessorRange> for Processor<'d> {
@@ -97,9 +97,9 @@ impl<'d> Processor<'d> {
             read_next: 0,
             code,
             #[cfg(feature = "js-esbuild")]
-            script_wg: WaitGroup::new(),
+            esbuild_wg: WaitGroup::new(),
             #[cfg(feature = "js-esbuild")]
-            script_results: Arc::new(Mutex::new(Vec::new())),
+            esbuild_results: Arc::new(Mutex::new(Vec::new())),
         }
     }
 
@@ -353,8 +353,8 @@ impl<'d> Processor<'d> {
 
     #[cfg(feature = "js-esbuild")]
     #[inline(always)]
-    pub fn new_script_section(&self) -> (WaitGroup, Arc<Mutex<Vec<JsMinSection>>>) {
-        (self.script_wg.clone(), self.script_results.clone())
+    pub fn new_esbuild_section(&self) -> (WaitGroup, Arc<Mutex<Vec<EsbuildSection>>>) {
+        (self.esbuild_wg.clone(), self.esbuild_results.clone())
     }
 
     // Since we consume the Processor, we must provide a full Error with positions.
@@ -370,32 +370,32 @@ impl<'d> Processor<'d> {
     #[inline(always)]
     pub fn finish(self) -> Result<usize, Error> {
         debug_assert!(self.at_end());
-        self.script_wg.wait();
-        let mut results = Arc::try_unwrap(self.script_results)
-            .unwrap_or_else(|_| panic!("failed to acquire script results"))
+        self.esbuild_wg.wait();
+        let mut results = Arc::try_unwrap(self.esbuild_results)
+            .unwrap_or_else(|_| panic!("failed to acquire esbuild results"))
             .into_inner()
             .unwrap();
         results.sort_unstable_by_key(|r| r.src.start);
-        // As we write minified JS code for sections from left to right, we will be shifting code
-        // towards the left as previous source JS code sections shrink. We need to keep track of
+        // As we write minified JS/CSS code for sections from left to right, we will be shifting code
+        // towards the left as previous source JS/CSS code sections shrink. We need to keep track of
         // the write pointer after previous compaction.
         // If there are no script sections, then we get self.write_next which will be returned.
         let mut write_next = results.get(0).map_or(self.write_next, |r| r.src.start);
-        for (i, JsMinSection { result, src }) in results.iter().enumerate() {
-            // Resulting minified JS to write.
+        for (i, EsbuildSection { result, src }) in results.iter().enumerate() {
+            // Resulting minified JS/CSS to write.
             // TODO Verify.
             // TODO Rewrite these in esbuild fork so we don't have to do a memcpy and search+replace.
-            let min_js = result.js.as_str().trim().replace("</script", "<\\/script");
-            let js_len = if min_js.len() < src.len() {
-                self.code[write_next..write_next + min_js.len()].copy_from_slice(min_js.as_bytes());
-                min_js.len()
+            let min_code = result.code.as_str().trim().replace("</script", "<\\/script");
+            let min_len = if min_code.len() < src.len() {
+                self.code[write_next..write_next + min_code.len()].copy_from_slice(min_code.as_bytes());
+                min_code.len()
             } else {
                 // If minified result is actually longer than source, then write source instead.
                 // NOTE: We still need to write source as previous iterations may have shifted code down.
                 self.code.copy_within(src.start..src.end, write_next);
                 src.len()
             };
-            let write_end = write_next + js_len;
+            let write_end = write_next + min_len;
             let next_start = results.get(i + 1).map_or(self.write_next, |r| r.src.start);
             self.code.copy_within(src.end..next_start, write_end);
             write_next = write_end + (next_start - src.end);
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
index c0ff825..f999a42 100644
--- a/src/tests/mod.rs
+++ b/src/tests/mod.rs
@@ -28,6 +28,7 @@ fn _eval_error(src: &'static [u8], expected: ErrorType, cfg: &super::Cfg) -> ()
 fn eval(src: &'static [u8], expected: &'static [u8]) -> () {
     _eval(src, expected, &super::Cfg {
         minify_js: false,
+        minify_css: false,
     });
 }
 
@@ -35,6 +36,7 @@ fn eval(src: &'static [u8], expected: &'static [u8]) -> () {
 fn eval_error(src: &'static [u8], expected: ErrorType) -> () {
     _eval_error(src, expected, &super::Cfg {
         minify_js: false,
+        minify_css: false,
     });
 }
 
@@ -43,6 +45,16 @@ fn eval_error(src: &'static [u8], expected: ErrorType) -> () {
 fn eval_with_js_min(src: &'static [u8], expected: &'static [u8]) -> () {
     _eval(src, expected, &super::Cfg {
         minify_js: true,
+        minify_css: false,
+    });
+}
+
+#[cfg(test)]
+#[cfg(feature = "js-esbuild")]
+fn eval_with_css_min(src: &'static [u8], expected: &'static [u8]) -> () {
+    _eval(src, expected, &super::Cfg {
+        minify_js: false,
+        minify_css: true,
     });
 }
 
@@ -402,3 +414,9 @@ fn test_js_minification() {
     "#, b"<script>let a=1;</script><script>let b=2;</script>");
     eval_with_js_min(b"<scRIPt type=text/plain>   alert(1.00000);   </scripT>", b"<script type=text/plain>   alert(1.00000);   </script>");
 }
+
+#[cfg(feature = "js-esbuild")]
+#[test]
+fn test_css_minification() {
+    eval_with_css_min(b"<style>div { color: yellow }</style>", b"<style>div{color:#ff0}</style>");
+}
diff --git a/src/unit/script.rs b/src/unit/script.rs
index de8c257..091da90 100644
--- a/src/unit/script.rs
+++ b/src/unit/script.rs
@@ -9,7 +9,7 @@ use crate::proc::Processor;
 use {
     std::sync::Arc,
     esbuild_rs::{TransformOptionsBuilder, TransformOptions},
-    crate::proc::JsMinSection,
+    crate::proc::EsbuildSection,
     crate::proc::checkpoint::WriteCheckpoint,
 };
 
@@ -36,14 +36,15 @@ pub fn process_script(proc: &mut Processor, cfg: &Cfg, js: bool) -> ProcessingRe
     proc.m(WhileNotSeq(&SCRIPT_END), Keep);
     // `process_tag` will require closing tag.
 
+    // TODO This is copied from style.rs.
     #[cfg(feature = "js-esbuild")]
     if js && cfg.minify_js {
-        let (wg, results) = proc.new_script_section();
+        let (wg, results) = proc.new_esbuild_section();
         let src = start.written_range(proc);
         unsafe {
             esbuild_rs::transform_direct_unmanaged(&proc[src], &TRANSFORM_OPTIONS.clone(), move |result| {
                 let mut guard = results.lock().unwrap();
-                guard.push(JsMinSection {
+                guard.push(EsbuildSection {
                     src,
                     result,
                 });
diff --git a/src/unit/style.rs b/src/unit/style.rs
index e867091..0b1d99e 100644
--- a/src/unit/style.rs
+++ b/src/unit/style.rs
@@ -4,16 +4,59 @@ use crate::err::ProcessingResult;
 use crate::proc::MatchAction::*;
 use crate::proc::MatchMode::*;
 use crate::proc::Processor;
+#[cfg(feature = "js-esbuild")]
+use {
+    std::sync::Arc,
+    esbuild_rs::{Loader, TransformOptionsBuilder, TransformOptions},
+    crate::proc::EsbuildSection,
+    crate::proc::checkpoint::WriteCheckpoint,
+};
+use crate::Cfg;
+
+#[cfg(feature = "js-esbuild")]
+lazy_static! {
+    static ref TRANSFORM_OPTIONS: Arc<TransformOptions> = {
+        let mut builder = TransformOptionsBuilder::new();
+        builder.loader = Loader::CSS;
+        builder.minify_identifiers = true;
+        builder.minify_syntax = true;
+        builder.minify_whitespace = true;
+        builder.build()
+    };
+}
 
 lazy_static! {
     static ref STYLE_END: AhoCorasick = AhoCorasickBuilder::new().ascii_case_insensitive(true).build(&["</style"]);
 }
 
 #[inline(always)]
-pub fn process_style(proc: &mut Processor) -> ProcessingResult<()> {
+pub fn process_style(proc: &mut Processor, cfg: &Cfg) -> ProcessingResult<()> {
+    #[cfg(feature = "js-esbuild")]
+    let start = WriteCheckpoint::new(proc);
     proc.require_not_at_end()?;
     proc.m(WhileNotSeq(&STYLE_END), Keep);
     // `process_tag` will require closing tag.
 
+    // TODO This is copied from script.rs.
+    #[cfg(feature = "js-esbuild")]
+    if cfg.minify_css {
+        let (wg, results) = proc.new_esbuild_section();
+        let src = start.written_range(proc);
+        unsafe {
+            esbuild_rs::transform_direct_unmanaged(&proc[src], &TRANSFORM_OPTIONS.clone(), move |result| {
+                let mut guard = results.lock().unwrap();
+                guard.push(EsbuildSection {
+                    src,
+                    result,
+                });
+                // Drop Arc reference and Mutex guard before marking task as complete as it's possible proc::finish
+                // waiting on WaitGroup will resume before Arc/Mutex is dropped after exiting this function.
+                drop(guard);
+                drop(results);
+                drop(wg);
+            });
+        };
+    };
+
     Ok(())
 }
diff --git a/src/unit/tag.rs b/src/unit/tag.rs
index d71187b..49308a0 100644
--- a/src/unit/tag.rs
+++ b/src/unit/tag.rs
@@ -211,7 +211,7 @@ pub fn process_tag(
     match tag_type {
         TagType::ScriptData => process_script(proc, cfg, false)?,
         TagType::ScriptJs => process_script(proc, cfg, true)?,
-        TagType::Style => process_style(proc)?,
+        TagType::Style => process_style(proc, cfg)?,
         _ => closing_tag_omitted = process_content(proc, cfg, child_ns, Some(tag_name))?.closing_tag_omitted,
     };