From 7c58b3ced142f011db44892be03cb576e29a6949 Mon Sep 17 00:00:00 2001
From: Johannes Meyer <johannes.meyer@icinga.com>
Date: Thu, 19 Nov 2020 11:30:34 +0100
Subject: [PATCH] LessCompiler: Add support for variable exports by modules

Using the following in a module's less file:

```
@exports: {
  @foo: "bar";
  @number: 4;
  @color: red;
};
```

will export the variables `@foo`, `@number` and `@color` into the global
scope. Though, exports are not able to override already defined variables.
That's still reserved for themes.
---
 library/Icinga/Web/LessCompiler.php | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/library/Icinga/Web/LessCompiler.php b/library/Icinga/Web/LessCompiler.php
index 7ebf66900..1d9aec05c 100644
--- a/library/Icinga/Web/LessCompiler.php
+++ b/library/Icinga/Web/LessCompiler.php
@@ -4,8 +4,6 @@
 namespace Icinga\Web;
 
 use Icinga\Application\Logger;
-use RecursiveArrayIterator;
-use RecursiveIteratorIterator;
 use lessc;
 
 /**
@@ -173,6 +171,7 @@ class LessCompiler
         }
 
         $moduleCss = '';
+        $exportedVars = [];
         foreach ($this->moduleLessFiles as $moduleName => $moduleLessFiles) {
             $moduleCss .= '.icinga-module.module-' . $moduleName . ' {';
 
@@ -184,13 +183,36 @@ class LessCompiler
             }
 
             foreach ($moduleLessFiles as $moduleLessFile) {
-                $moduleCss .= file_get_contents($moduleLessFile);
+                $content = file_get_contents($moduleLessFile);
+
+                $pattern = '/^@exports:\s*{((?:\s*@[^:}]+:[^;]*;\s+)+)};$/m';
+                if (preg_match_all($pattern, $content, $matches, PREG_SET_ORDER)) {
+                    foreach ($matches as $match) {
+                        $content = str_replace($match[0], '', $content);
+                        foreach (explode("\n", trim($match[1])) as $line) {
+                            list($name, $value) = explode(':', $line, 2);
+                            $exportedVars[trim($name)] = trim($value, ' ;');
+                        }
+                    }
+                }
+
+                $moduleCss .= $content;
             }
+
             $moduleCss .= '}';
         }
 
         $this->source .= $moduleCss;
 
+        $varExports = '';
+        foreach ($exportedVars as $name => $value) {
+            $varExports .= sprintf("%s: %s;\n", $name, $value);
+        }
+
+        // exported vars are injected at the beginning to avoid that they are
+        // able to override other variables, that's what themes are for
+        $this->source = $varExports . "\n\n" . $this->source;
+
         if ($this->theme !== null) {
             $this->source .= file_get_contents($this->theme);
         }