commit d76e764496069565436e35e1fa429d771be30d98
Author: Yusuf Kandemir <yusuf.kandemir@outlook.com.tr>
Date:   Sat Nov 10 13:51:55 2018 +0300

    Initial commit
    
    Procedural implemantation of W3C Microdata Specification

diff --git a/src/procedures.php b/src/procedures.php
new file mode 100644
index 0000000..645a731
--- /dev/null
+++ b/src/procedures.php
@@ -0,0 +1,272 @@
+<?php
+
+// Microdata Extractor
+function extractMicrodata(DOMNodeList $topLevelItems)
+{
+    // Step 1
+    $result = new stdClass;
+
+    // Step 2
+    $items = [];
+
+    // Step 3
+    // items = map("top-level microdata items", item => getObject(item))
+    $items = array_map('getObject', iterator_to_array($topLevelItems));
+
+    /*foreach ($topLevelItems as $topLevelItem) {
+        $items[] = getObject($topLevelItem);
+    }*/
+
+    // Step 4
+    $result->items = $items;
+
+    // Step 5
+    return $result;
+}
+
+
+// Get Object
+
+function getObject(DOMElement $item, $memory = [])
+{
+    // Step 1
+    $result = new stdClass();
+
+    // Step 2 in 2nd parameter of this function
+    // $memory = [];
+
+    // Step 3
+    $memory[] = $item;
+
+    // Step 4
+    $itemtype = $item->getAttribute('itemtype');
+    $result->type = $itemtype ? preg_split('/\s+/', $itemtype) : [];
+    // @todo Check if types are valid absolute urls
+
+    // Step 5
+    if ($itemId = $item->getAttribute('itemid')) {
+        $result->id = $itemId;
+    }
+    // @todo Check if item ids are valid absolute urls or like isbn:xxx
+
+    // Step 6
+    $properties = new stdClass;
+
+    // Step 7
+    foreach (getProperties($item) as $element) {
+        $value = getPropertyValue($element);
+
+        if (isItem($value)) {
+            foreach ($memory as $memory_item) {
+                if ($element->isSameNode($memory_item)) {
+                    $value = 'ERROR';
+                }
+            }
+
+            if ($value != 'ERROR') {
+                $value = getObject($value, $memory);
+            }
+        }
+
+        foreach (getPropertyNames($element) as $name) {
+            $properties->{$name}[] = $value;
+        }
+    }
+
+    // Step 8
+    $result->properties = $properties;
+
+    // Step 9
+    return $result;
+}
+
+// https://www.w3.org/TR/microdata/#dfn-property-name
+function getPropertyNames(DOMElement $item)
+{
+    // Step 1
+    $itemprop = $item->getAttribute('itemprop');
+    $tokens = $itemprop ? preg_split('/\s+/', $itemprop) : [];
+
+    // Step 2
+    $properties = [];
+
+    // Step 3
+    foreach ($tokens as $token) {
+        if (isAbsoluteUri($token)) {
+            $properties[] = $token;
+        } elseif (isTypedItem($item)) {
+            $properties[] = /*$vocabularyIdentifier . */ $token;
+        } else {
+            $properties[] = $token;
+        }
+    }
+
+    $properties = array_unique($properties);
+
+    return $properties;
+}
+
+// https://www.w3.org/TR/microdata/#dfn-item-properties
+function getProperties(DOMElement $root)
+{
+    // Step 1
+    $results = [];
+    $memory = [];
+    $pending = [];
+
+    // Step 2
+    $memory[] = $root;
+
+    // Step 3
+    if ($root->hasChildNodes()) {
+        $childNodes = iterator_to_array($root->childNodes);
+
+        $childNodes = array_filter($childNodes, function ($node) {
+            return $node instanceof DOMElement;
+        }); // Get only DOMElements
+
+        $pending = array_merge($pending, $childNodes);
+    }
+
+    // Step 4
+    if ($root->hasAttribute('itemref')) {
+        $tokens = preg_split('/\s+/', $root->getAttribute('itemref'));
+
+        foreach ($tokens as $token) {
+            // @todo Implement xpath query and get the first item
+        }
+    }
+
+    // Step 5
+    while ($pending) {
+        // Step 6
+        $current = array_pop($pending);
+
+        // Step 7
+        // in_array can't compare objects
+        /*if (in_array($current, $memory)) {
+            // There is MicrodataError
+            continue;
+        }*/
+        $error = false;
+
+        foreach ($memory as $memory_item) {
+            if ($current->isSameNode($memory_item)) {
+                // There is MicrodataError
+                $error = true;
+                break;
+            }
+        }
+
+        if ($error) {
+            continue;
+        }
+
+        // Step 8
+        $memory[] = $current;
+
+        // Step 9
+        if (! $current->hasAttribute('itemscope')) {
+            if ($current->hasChildNodes()) {
+                $childNodes = iterator_to_array($current->childNodes);
+
+                $childNodes = array_filter($childNodes, function ($node) {
+                    return $node instanceof DOMElement;
+                });
+
+                $pending = array_merge($pending, $childNodes);
+            }
+        }
+
+        // Step 10
+        if ($current->hasAttribute('itemprop') && /* hasPropertyNames */ getPropertyNames($current)) {
+            $results[] = $current;
+        }
+
+        // Step 11: Return to loop
+    }
+
+    // Step 12: End of loop. Sort results in tree order.
+
+    $results = array_reverse($results);
+
+    // Step 13
+    return $results;
+}
+
+// https://www.w3.org/TR/microdata/#dfn-property-value
+function getPropertyValue(DOMElement $item)
+{
+
+    if ($item->hasAttribute('itemscope')) {
+        return $item;
+    }
+
+    if ($item->hasAttribute('content')) {
+        return $item->getAttribute('content');
+    }
+
+    $base = $item->ownerDocument->documentURI;
+
+    switch ($item->tagName) {
+        case 'audio':
+        case 'embed':
+        case 'iframe':
+        case 'img':
+        case 'source':
+        case 'track':
+        case 'video':
+            if ($item->hasAttribute('src')) {
+                $result = $item->getAttribute('src');
+
+                // @todo check against protocol relative urls like "//example.com/test.jpg"
+                return isAbsoluteUri($result) ? $result : $base.$result;
+            }
+        case 'a':
+        case 'area':
+        case 'link':
+            if ($item->hasAttribute('href')) {
+                $result = $item->getAttribute('href');
+
+                return isAbsoluteUri($result) ? $result : $base.$result;
+            }
+        case 'object':
+            if ($item->hasAttribute('data')) {
+                $result = $item->getAttribute('data');
+
+                return isAbsoluteUri($result) ? $result : $base.$result;
+            }
+        case 'data':
+        case 'meter':
+            if ($item->hasAttribute('value')) {
+                return $item->getAttribute('value');
+            }
+        case 'time':
+            if ($item->hasAttribute('datetime')) {
+                return $item->getAttribute('datetime');
+            }
+        default:
+            return $item->textContent;
+    }
+}
+
+function isItem($element)
+{
+    return $element instanceof DOMElement && $element->hasAttribute('itemscope');
+}
+
+function isTypedItem(DOMElement $item)
+{
+    $tokens = [];
+
+    if ($item->hasAttribute('itemtype')) {
+        $tokens = preg_split("/\s+/", $item->getAttribute('itemtype'));
+    }
+
+    return !empty($tokens);
+}
+
+function isAbsoluteUri(string $uri)
+{
+    return preg_match("/^\w+:/", trim($uri));
+}