[FEATURE] Parse simple expressions

Author: raxbg

src/Value/Expression.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Sabberworm\CSS\Value;
+
+use Sabberworm\CSS\OutputFormat;
+use Sabberworm\CSS\Parsing\ParserState;
+
+/**
+ * An `Expression` represents a special kind of value that is comprised of multiple components wrapped in parenthesis.
+ * Examle `height: (vh - 10);`.
+ */
+class Expression extends CSSFunction
+{
+    /**
+     * @param ParserState $oParserState
+     * @param bool $bIgnoreCase
+     *
+     * @return Expression
+     *
+     * @throws SourceException
+     * @throws UnexpectedEOFException
+     * @throws UnexpectedTokenException
+     */
+    public static function parse(ParserState $oParserState, $bIgnoreCase = false)
+    {
+        $oParserState->consume('(');
+        $aArguments = Value::parseValue($oParserState, ['=', ' ', ',']);
+        $mResult = new Expression("", $aArguments, ',', $oParserState->currentLine());
+        $oParserState->consume(')');
+        return $mResult;
+    }
+}

src/Value/Value.php

@@ -164,6 +164,8 @@ public static function parsePrimitiveValue(ParserState $parserState)
             $value = LineName::parse($parserState);
         } elseif ($parserState->comes('U+')) {
             $value = self::parseUnicodeRangeValue($parserState);
+        } elseif ($parserState->comes("(")) {
+            $value = Expression::parse($parserState);
         } else {
             $nextCharacter = $parserState->peek(1);
             try {

tests/ParserTest.php

@@ -435,6 +435,20 @@ public function functionSyntax(): void
         self::assertSame($expected, $document->render());
     }
 
+    /**
+     * @test
+     */
+    public function parseExpressions()
+    {
+        $oDoc = self::parsedStructureForFile('expressions');
+        $sExpected = 'div {height: (vh - 10);}'
+            . "\n"
+            . 'div {height: (vh - 10)/2;}'
+            . "\n"
+            . 'div {height: max(5,(vh - 10));}';
+        self::assertSame($sExpected, $oDoc->render());
+    }
+
     /**
      * @test
      */

tests/fixtures/expressions.css

@@ -0,0 +1,11 @@
+div {
+    height: (vh - 10);
+}
+
+div {
+    height: (vh - 10) / 2;
+}
+
+div {
+    height: max(5, (vh - 10));
+}