implement robots.txt library #2

library/robots.php

@@ -0,0 +1,83 @@
+<?php
+
+class Robots {
+
+  private $_index = [];
+
+  public function __construct(string $data) {
+
+    $read = false;
+
+    foreach ((array) explode(PHP_EOL, $data) as $row) {
+
+      $row = strtolower(trim($row));
+
+      // User-agent * begin
+      if (preg_match('!^user-agent:\s?\*!', $row)) {
+        $read = true;
+        continue;
+      }
+
+      if ($read) {
+        $part = explode(' ', $row);
+
+        if (isset($part[0]) && isset($part[1])) {
+
+          if (false !== strpos($part[0], 'allow')) {
+            $this->_index[$this->_regex(trim($part[1]))] = true;
+          }
+
+          if (false !== strpos($part[0], 'disallow')) {
+            $this->_index[$this->_regex(trim($part[1]))] = false;
+          }
+        }
+      }
+
+      // User-agent * end
+      if ($read && preg_match('!^user-agent:!', $row)) {
+        break;
+      }
+    }
+  }
+
+  public function indexURL(string $url) {
+
+    // Unify case match
+    $url = strtolower(trim($url));
+
+    // Convert to URI
+    $url = str_replace(parse_url($url, PHP_URL_SCHEME) . '://' .
+                       parse_url($url, PHP_URL_HOST) .
+                       parse_url($url, PHP_URL_PORT),
+                       '', $url);
+
+    // Index by default
+    $result = true;
+
+    // Begin index rules by ASC priority
+    foreach ($this->_index as $rule => $index) {
+
+      if (preg_match('!^' . $rule . '!', $url)) {
+
+        $result = $index;
+      }
+    }
+
+    return $result;
+  }
+
+  private function _regex(string $string) {
+
+    return str_replace(
+      [
+        '*',
+        '?'
+      ],
+      [
+        '.*',
+        '\?'
+      ],
+      $string
+    );
+  }
+}