Added tracking load of individual plugin load (WP 5.1+)

Fixes #24

src/Record/Collector/Plugin_Load_Collector.php

@@ -0,0 +1,69 @@
+<?php
+declare( strict_types=1 );
+
+namespace Rarst\Laps\Record\Collector;
+
+use Rarst\Laps\Record\Record;
+use Rarst\Laps\Record\Record_Interface;
+
+/**
+ * Tracks load time of individual plugins.
+ */
+class Plugin_Load_Collector implements Record_Collector_Interface {
+
+	/** @var float */
+	private $last;
+
+	/** @var array */
+	private $entries = [];
+
+	/**
+	 * Sets up start time and tracking callbacks.
+	 */
+	public function __construct() {
+		$this->last = microtime( true );
+
+		add_action( 'network_plugin_loaded', [ $this, 'plugin_loaded' ] );
+		add_action( 'plugin_loaded', [ $this, 'plugin_loaded' ] );
+	}
+
+	/**
+	 * Records time for a plugin that just finished loading.
+	 *
+	 * @param string $plugin Plugin file path.
+	 */
+	public function plugin_loaded( string $plugin ): void {
+
+		$time            = microtime( true );
+		$this->entries[] = [
+			'name'     => $plugin,
+			'origin'   => $this->last,
+			'duration' => $time - $this->last,
+		];
+		$this->last      = $time;
+	}
+
+	/**
+	 * @return Record_Interface[]
+	 */
+	public function get_records(): array {
+		return array_map( [ $this, 'create_record' ], $this->entries );
+	}
+
+	/**
+	 * Converts recorded information into a Record instance.
+	 *
+	 * @param array $entry Data entry for the plugin.
+	 *
+	 * @return Record_Interface
+	 */
+	private function create_record( array $entry ): Record_Interface {
+		return new Record(
+			plugin_basename( $entry['name'] ),
+			$entry['origin'],
+			$entry['duration'],
+			'',
+			'plugin'
+		);
+	}
+}