selector-unify() implementation trying to get the spirit of the reference implementation #310

Author: Cerdic

src/Compiler.php

@@ -6309,6 +6309,236 @@ protected function libSelectorParse($args)
         return $this->formatOutputSelector($selectors);
     }
 
+    protected static $libSelectorUnify = ['selectors1', 'selectors2'];
+    protected function libSelectorUnify($args)
+    {
+        list($selectors1, $selectors2) = $args;
+        $selectors1 = $this->getSelectorArg($selectors1);
+        $selectors2 = $this->getSelectorArg($selectors2);
+
+        if (! $selectors1 || ! $selectors2) {
+            $this->throwError("selector-unify() invalid arguments");
+        }
+
+        // only consider the first compound of each
+        $compound1 = reset($selectors1);
+        $compound2 = reset($selectors2);
+
+        // unify them and that's it
+        $unified = $this->unifyCompoundSelectors($compound1, $compound2);
+
+        return $this->formatOutputSelector($unified);
+    }
+
+    /**
+     * The selector-unify magic as its best
+     * (at least works as expected on test cases)
+     *
+     * @param array $compound1
+     * @param array $compound2
+     * @return array|mixed
+     */
+    protected function unifyCompoundSelectors($compound1, $compound2)
+    {
+
+        if (!count($compound1)) {
+            return $compound2;
+        }
+        if (!count($compound2)) {
+            return $compound1;
+        }
+
+        // check that last part are compatible
+        $lastPart1 = array_pop($compound1);
+        $lastPart2 = array_pop($compound2);
+        $last = $this->mergeParts($lastPart1, $lastPart2);
+        if (!$last) {
+            return [[]];
+        }
+        $unifiedCompound = [$last];
+        $unifiedSelectors = [$unifiedCompound];
+
+        // do the rest
+        while (count($compound1) || count($compound2)) {
+            $part1 = end($compound1);
+            $part2 = end($compound2);
+            if ($part1 && ($match2 = $this->matchPartInCompound($part1, $compound2))) {
+                list($compound2, $part2, $after2) = $match2;
+                if ($after2) {
+                    $unifiedSelectors = $this->prependSelectors($unifiedSelectors, $after2);
+                }
+                $c = $this->mergeParts($part1, $part2);
+                $unifiedSelectors = $this->prependSelectors($unifiedSelectors, [$c]);
+                $part1 = $part2 = null;
+                array_pop($compound1);
+            }
+            if ($part2 && ($match1 = $this->matchPartInCompound($part2, $compound1))) {
+                list($compound1, $part1, $after1) = $match1;
+                if ($after1) {
+                    $unifiedSelectors = $this->prependSelectors($unifiedSelectors, $after1);
+                }
+                $c = $this->mergeParts($part2, $part1);
+                $unifiedSelectors = $this->prependSelectors($unifiedSelectors, [$c]);
+                $part1 = $part2 = null;
+                array_pop($compound2);
+            }
+            $new = [];
+            if ($part1 && $part2) {
+                array_pop($compound1);
+                array_pop($compound2);
+                $s = $this->prependSelectors($unifiedSelectors, [$part2]);
+                $new = array_merge($new, $this->prependSelectors($s, [$part1]));
+                $s = $this->prependSelectors($unifiedSelectors, [$part1]);
+                $new = array_merge($new, $this->prependSelectors($s, [$part2]));
+            } elseif ($part1) {
+                array_pop($compound1);
+                $new = array_merge($new, $this->prependSelectors($unifiedSelectors, [$part1]));
+            } elseif ($part2) {
+                array_pop($compound2);
+                $new = array_merge($new, $this->prependSelectors($unifiedSelectors, [$part2]));
+            }
+            if ($new) {
+                $unifiedSelectors = $new;
+            }
+        }
+
+        return $unifiedSelectors;
+    }
+
+    /**
+     * Prepend each selector from $selectors with $parts
+     * @param $selectors
+     * @param $parts
+     * @return array
+     */
+    protected function prependSelectors($selectors, $parts)
+    {
+        $new = [];
+        foreach ($selectors as $compoundSelector) {
+            array_unshift($compoundSelector, $parts);
+            $new[] = $compoundSelector;
+        }
+        return $new;
+    }
+
+    /**
+     * Try to find a matching part in a compound:
+     * - with same html tag name
+     * - with some class or id or something in common
+     * @param array $part
+     * @param array $compound
+     * @return array|bool
+     */
+    protected function matchPartInCompound($part, $compound)
+    {
+        $partTag = $this->findTagName($part);
+        $before = $compound;
+        $after = [];
+        // try to find a match by tag name first
+        while (count($before)) {
+            $p = array_pop($before);
+            if ($partTag && $partTag !== '*' && $partTag == $this->findTagName($p)) {
+                return [$before, $p, $after];
+            }
+            $after[] = $p;
+        }
+        // try again matching a non empty intersection and a compatible tagname
+        $before = $compound;
+        $after = [];
+        while (count($before)) {
+            $p = array_pop($before);
+            if ($this->checkCompatibleTags($partTag, $this->findTagName($p))) {
+                if (count(array_intersect($part, $p))) {
+                    return [$before, $p, $after];
+                }
+            }
+            $after[] = $p;
+        }
+
+        return false;
+    }
+
+    /**
+     * Merge two part list taking care that
+     * - the html tag is coming first - if any
+     * - the :something are coming last
+     *
+     * @param $parts1
+     * @param $parts2
+     * @return array
+     */
+    protected function mergeParts($parts1, $parts2)
+    {
+        $tag1 = $this->findTagName($parts1);
+        $tag2 = $this->findTagName($parts2);
+        $tag = $this->checkCompatibleTags($tag1, $tag2);
+        // not compatible tags
+        if ($tag === false) {
+            return [];
+        }
+
+        if ($tag) {
+            if ($tag1) {
+                $parts1 = array_diff($parts1, [$tag1]);
+            }
+            if ($tag2) {
+                $parts2 = array_diff($parts2, [$tag2]);
+            }
+        }
+
+        $mergedParts = array_merge($parts1, $parts2);
+        $mergedOrderedParts = [];
+        foreach ($mergedParts as $part) {
+            if (strpos($part, ':') === 0) {
+                $mergedOrderedParts[] = $part;
+            }
+        }
+        $mergedParts = array_diff($mergedParts, $mergedOrderedParts);
+        $mergedParts = array_merge($mergedParts, $mergedOrderedParts);
+        if ($tag) {
+            array_unshift($mergedParts, $tag);
+        }
+        return $mergedParts;
+    }
+
+    /**
+     * Check the compatibility between two tag names:
+     * if both are defined they should be identical or one has to be '*'
+     *
+     * @param $tag1
+     * @param $tag2
+     * @return array|bool
+     */
+    protected function checkCompatibleTags($tag1, $tag2)
+    {
+        $tags = [$tag1, $tag2];
+        $tags = array_unique($tags);
+        $tags = array_filter($tags);
+        if (count($tags)>1) {
+            $tags = array_diff($tags, ['*']);
+        }
+        // not compatible nodes
+        if (count($tags)>1) {
+            return false;
+        }
+        return $tags;
+    }
+
+    /**
+     * Find the html tag name in a selector parts list
+     * @param array $parts
+     * @return mixed|string
+     */
+    protected function findTagName($parts)
+    {
+        foreach ($parts as $part) {
+            if (! preg_match('/^[\[.:#%_-]/', $part)) {
+                return $part;
+            }
+        }
+        return '';
+    }
+
     protected static $libSimpleSelectors = ['selector'];
     protected function libSimpleSelectors($args)
     {