Refactor to MediaHandler transform (#20)

Closes #6, Closes #18

This PR separates out 3 different classes: a distinct Hooks handling class, a MediaHandler class for models, and a MediaTransform class that handles all the actual model rendering.

Reviewed-on: #20

includes/GlModelHandler.php

@@ -0,0 +1,77 @@
+<?php
+namespace MediaWiki\Extension\GlModelViewer;
+
+use ImageHandler;
+use Html;
+
+class GlModelHandler extends ImageHandler {
+  /**
+   * Model cannot be displayed directly in a browser but can be rendered.
+   * 
+	 * @param File $file
+	 * @return bool
+	 */
+	public function mustRender( $file ) {
+		return true;
+	}
+
+  /**
+   * Model can be rendered.
+   * 
+	 * @param File $file
+	 * @return bool
+	 */
+	public function canRender( $file ) {
+		return true;
+	}
+
+  /**
+   * Get a MediaTransformOutput object representing the transformed output.
+   * 
+   * @param File	$image
+   * @param string	$dstPath	Filesystem destination path
+   * @param string	$dstUrl	Destination URL to use in output HTML
+   * @param array	$params	Arbitrary set of parameters validated by $this->validateParam()
+   * @param int	$flags	A bitfield, may contain self::TRANSFORM_LATER
+   * @return MediaTransformOutput
+   */
+  public function doTransform($image, $dstPath, $dstUrl, $params, $flags = 0) {
+    return new GlModelTransformOutput($image, $params);
+  }
+
+  /**
+   * Check the incoming media parameters
+   * 
+	 * @param string $name
+	 * @param string $value
+	 * @return bool
+	 */
+	public function validateParam( $name, $value ) {
+    if (in_array($name, ['width', 'height'])) {
+      return $value > 0;
+    } else if (in_array($name, ['view', 'hsset'])) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  /**
+   * Small helper function to display information on the browser console
+   * 
+   * Usage:
+   * echo '<script>';
+   * self::console_log('logged string');
+   * echo '</script>';
+   * 
+   * @param $data information to display
+   * @param bool $add_script_tags true to put information is inside complete script tag
+   */
+  public static function console_log($data, $add_script_tags = false) {
+    $command = 'console.log('. json_encode($data, JSON_HEX_TAG).');';
+    if ($add_script_tags) {
+        $command = '<script>'. $command . '</script>';
+    }
+    echo $command;
+  }
+}