<?php
namespace W3TC;

/**
 * Google Page Speed API
 */
define( 'W3TC_PAGESPEED_API_URL', 'https://www.googleapis.com/pagespeedonline/v1/runPagespeed' );

/**
 * class PageSpeed_Api
 */
class PageSpeed_Api {
	/**
	 * API Key
	 */
	private $key = '';

	/**
	 * Referrer for key restricting
	 */
	private $key_restrict_referrer = '';

	/**
	 * PHP5-style constructor
	 */
	function __construct( $api_key, $api_ref ) {
		$this->key = $api_key;
		$this->key_restrict_referrer = $api_ref;
	}

	/**
	 * Analyze URL
	 */
	function analyze( $url ) {
		$json = $this->_request( $url );
		if ( !$json )
			return null;

		$results = $this->_parse( $json );
		if ( $results )
			$this->_sort( $results );

		return $results;
	}

	/**
	 * Make API request
	 *
	 * @param string  $url
	 * @return string
	 */
	function _request( $url ) {
		$request_url = Util_Environment::url_format( W3TC_PAGESPEED_API_URL, array(
				'url' => $url,
				'key' => $this->key,
			) );

		$response = Util_Http::get( $request_url, array(
				'timeout' => 120,
				'headers' => array( 'Referer' => $this->key_restrict_referrer )
			) );

		if ( !is_wp_error( $response ) && $response['response']['code'] == 200 ) {
			return $response['body'];
		}

		return false;
	}

	/**
	 * Parse response
	 *
	 * @param string  $json
	 * @return array|bool
	 */
	function _parse( $json ) {
		$data = json_decode( $json );
		$results = false;

		if ( isset( $data->formattedResults ) ) {
			$results = array(
				'url' => $data->id,
				'code' => $data->responseCode,
				'title' => $data->title,
				'score' => $data->score,
				'rules' => array()
			);

			foreach ( (array) $data->formattedResults->ruleResults as $i => $rule_result ) {
				$results['rules'][$i] = array(
					'name' => $rule_result->localizedRuleName,
					'impact' => $rule_result->ruleImpact,
					'priority' => $this->_get_priority( $rule_result->ruleImpact ),
					'resolution' => $this->_get_resolution( $rule_result->localizedRuleName ),
					'blocks' => array()
				);

				if ( isset( $rule_result->urlBlocks ) ) {
					foreach ( (array) $rule_result->urlBlocks as $j => $url_block ) {
						$args = isset( $url_block->header->args ) ? $url_block->header->args : array();
						$results['rules'][$i]['blocks'][$j] = array(
							'header' => $this->_format_string( $url_block->header->format, $args ),
							'urls' => array()
						);

						if ( isset( $url_block->urls ) ) {
							foreach ( (array) $url_block->urls as $k => $url ) {
								$args = isset( $url->result->args ) ? $url->result->args : array();
								$results['rules'][$i]['blocks'][$j]['urls'][$k] = array(
									'result' => $this->_format_string( $url->result->format, $args )
								);
							}
						}
					}
				}
			}
		}

		return $results;
	}

	/**
	 * Returns rule priority by impact
	 *
	 * @param float   $impact
	 * @return string
	 */
	function _get_priority( $impact ) {
		if ( $impact < 3 ) {
			$priority = 'low';
		} elseif ( $impact >= 3 && $impact <= 10 ) {
			$priority = 'medium';
		} else {
			$priority = 'high';
		}

		return $priority;
	}

	/**
	 * Returns resolution
	 *
	 * @param string  $code
	 * @return array
	 */
	function _get_resolution( $code ) {
		switch ( $code ) {
		case 'MinifyHTML':
			return array(
				'header' => 'Enable HTML Minify',
				'tab' => 'minify'
			);

		case 'MinifyJavaScript':
		case 'DeferParsingJavaScript':
			return array(
				'header' => 'Enable JavaScript Minify',
				'tab' => 'minify'
			);

		case 'MinifyCss':
		case 'PutCssInTheDocumentHead':
			return array(
				'header' => 'Enable CSS Minify',
				'tab' => 'minify'
			);

		case 'AvoidCssImport':
			return array(
				'header' => 'Enable CSS Minify and @import processing',
				'tab' => 'minify'
			);

		case 'OptimizeTheOrderOfStylesAndScripts':
			return array(
				'header' => 'Enable JavaScript and CSS Minify',
				'tab' => 'minify'
			);

		case 'PreferAsyncResources':
			return array(
				'header' => 'Switch to non-blocking JavaScript embedding',
				'tab' => 'minify'
			);

		case 'RemoveQueryStringsFromStaticResources':
			return array(
				'header' => 'Disable the "Prevent caching of objects after settings change" feature',
				'tab' => 'browsercache'
			);

		case 'LeverageBrowserCaching':
			return array(
				'header' => 'Enable the expires header on the Browser Cache Settings tab',
				'tab' => 'browsercache'
			);

		case 'SpecifyACacheValidator':
			return array(
				'header' => 'Enable the ETag header on the Browser Cache Settings tab',
				'tab' => 'browsercache'
			);
		}

		return array();
	}

	private $_format_string_args = array();

	/**
	 * Formats string
	 *
	 * @param string  $format
	 * @param array   $args
	 * @return mixed
	 */
	function _format_string( $format, $args ) {
		$result = $format;
		if ( !empty( $args ) ) {
			$this->_format_string_args = $args;

			$result = preg_replace_callback( '~\$([0-9]+)~', array(
					$this,
					'_format_string_callback'
				), $format );
		}

		return $result;
	}

	/**
	 * Format string callback
	 *
	 * @param array   $matches
	 * @return string
	 */
	function _format_string_callback( $matches ) {
		$index = (int) $matches[1] - 1;

		if ( isset( $this->_format_string_args[$index]->value ) ) {
			switch ( $this->_format_string_args[$index]->type ) {
			case 'URL':
				return sprintf( '<a href="%s">%s</a>', $this->_format_string_args[$index]->value, $this->_format_string_args[$index]->value );

			default:
				return $this->_format_string_args[$index]->value;
			}
		}

		return $matches[0];
	}

	/**
	 * Sort results
	 *
	 * @param array   $results
	 * @return void
	 */
	function _sort( &$results ) {
		if ( isset( $results['rules'] ) ) {
			usort( $results['rules'], array(
					$this,
					'_sort_cmp'
				) );
		}
	}

	/**
	 * Compare function
	 *
	 * @param array   $rule_result1
	 * @param array   $rule_result2
	 * @return int
	 */
	function _sort_cmp( &$rule_result1, &$rule_result2 ) {
		if ( $rule_result1['impact'] == $rule_result2['impact'] ) {
			return 0;
		}

		return ( $rule_result1['impact'] > $rule_result2['impact'] ) ? -1 : 1;
	}
}