CSS now only compiled when necessary on startup

scripts/compile_css.js

@@ -1,24 +1,86 @@
 const fs = require('fs');
-const settings = require('../lib/settings');
+const css_path = './public/css/';
+const theme_selector_filename = '_theme-selector.scss';
+const style_filename = 'style.scss';
+const style_min_filename = 'style.min.css'
+const custom_filename = 'custom.scss';
+const custom_min_filename = 'custom.min.css'
+const theme_selector_template_text = `$theme-name: "replace";`;
+let compile_theme_css = false;
+let compile_custom_css = false;
+let theme_name = '';
 
-console.log('Compiling CSS.. Please wait..');
+// check if the theme selector file exists
+if (!fs.existsSync(`${css_path}${theme_selector_filename}`)) {
+  // theme file doesn't exist, so it is necessary to compile the css
+  compile_theme_css = true;
+} else {
+  const settings = require('../lib/settings');
+  const last_theme = fs.readFileSync(`${css_path}${theme_selector_filename}`, 'utf-8');
+
+  theme_name = settings.shared_pages.theme;
+
+  // check if the theme name has changed since last run
+  if (theme_selector_template_text.replace('replace', theme_name) != last_theme) {
+    // theme name has changed, so it is necessary to compile the css
+    compile_theme_css = true;
+  } else if (!fs.existsSync(`${css_path}${style_min_filename}`)) {
+    // the minified style file does not exist, so it is necessary to compile the css 
+    compile_theme_css = true;
+  } else {
+    const style_stats = fs.statSync(`${css_path}${style_filename}`);
+    const style_min_stats = fs.statSync(`${css_path}${style_min_filename}`);
+
+    // check if the style file was last modified after the minified style file
+    if (style_stats.mtime > style_min_stats.mtime) {
+      // style file was modified since the style min file was created, so it is necessary to compile the css
+      compile_theme_css = true;
+    }
+  }
+}
+
+// check if the minified custom file exists
+if (!fs.existsSync(`${css_path}${custom_min_filename}`)) {
+  // the minified custom file does not exist, so it is necessary to compile the css 
+  compile_custom_css = true;
+} else {
+  const custom_stats = fs.statSync(`${css_path}${custom_filename}`);
+  const custom_min_stats = fs.statSync(`${css_path}${custom_min_filename}`);
+
+  // check if the custom file was last modified after the minified custom file
+  if (custom_stats.mtime > custom_min_stats.mtime) {
+    // custom file was modified since the custom min file was created, so it is necessary to compile the css
+    compile_custom_css = true;
+  }
+}
+
+// check if it necessary to compile any css files
+if (compile_theme_css || compile_custom_css) {
+  console.log('Compiling CSS.. Please wait..');
 
-// ensure the selected theme is properly installed
-fs.writeFile('./public/css/_theme-selector.scss', `$theme-name: "${settings.shared_pages.theme}";`, function (err) {
   const sass = require('sass');
 
-  // generate minified css from style.scss file
-  const minified = sass.compile('./public/css/style.scss', {style: 'compressed'});
+  // check if the theme css should be compiled
+  if (compile_theme_css) {
+    // ensure the selected theme is properly installed
+    fs.writeFileSync(`${css_path}${theme_selector_filename}`, `$theme-name: "${theme_name}";`, 'utf-8');
 
-  // save the minified css to file
-  fs.writeFile('./public/css/style.min.css', minified.css, function (err) {
-    // generate minified css from custom.scss file
-    const custom_minified = sass.compile('./public/css/custom.scss', {style: 'compressed'});
+    // generate minified css from style.scss file
+    const minified = sass.compile(`${css_path}${style_filename}`, {style: 'compressed'});
 
     // save the minified css to file
-    fs.writeFile('./public/css/custom.min.css', custom_minified.css, function (err) {
-      // finished compiling css
-      process.exit(0);
-    });
-  });
-});
+    fs.writeFileSync(`${css_path}${style_min_filename}`, minified.css, 'utf-8');
+  }
+
+  // check if the custom css should be compiled
+  if (compile_custom_css) {
+    // generate minified css from custom.scss file
+    const custom_minified = sass.compile(`${css_path}${custom_filename}`, {style: 'compressed'});
+
+    // save the minified css to file
+    fs.writeFileSync(`${css_path}${custom_min_filename}`, custom_minified.css, 'utf-8');
+  }
+}
+
+// finished compiling css
+process.exit(0);