<?php
/**
 * Thresholds for the Client Monitor.
 *
 * @package TurtleReport
 */

namespace TurtleReport\Attention;

defined( 'ABSPATH' ) || exit;

/**
 * When a change is big enough, and based on enough data, to be worth a
 * founder's attention.
 *
 * Every rule has a volume floor (so 4 → 2 leads is never "−50%"), a trigger
 * and a lower "clear" level. An open alert only resolves once the number is
 * back past the clear level, so an alert doesn't flicker on and off around
 * the trigger.
 */
final class Rules {

	const STANDARD = 'standard';
	const RELAXED  = 'relaxed';

	/**
	 * Rules for a sensitivity setting.
	 *
	 * "relaxed" ("only big drops") raises every volume floor and makes every
	 * drop threshold 1.5 times as large.
	 *
	 * @param string $sensitivity standard|relaxed.
	 * @return array
	 */
	public static function get( $sensitivity = self::STANDARD ) {
		$rules = array(
			// Google clicks for the whole site.
			'clicks'   => array(
				'min_prev' => 100,
				'trigger'  => -20,
				'clear'    => -10,
				'high'     => -40,
			),
			// One important page: in the top pages by clicks, or it brought leads.
			'page'     => array(
				'top'       => 10,
				'min_leads' => 3,
				'min_prev'  => 30,
				'min_lost'  => 20,
				'trigger'   => -30,
				'clear'     => -15,
				'high'      => -60,
				'max'       => 3,
			),
			// Keywords that slipped down Google's results.
			'rankings' => array(
				'min_prev_clicks' => 10,
				'min_prev_impr'   => 300,
				'worse'           => 3.0,
				'clear'           => 1.5,
				'min_keywords'    => 3,
				'min_lost'        => 30,
				'high_lost'       => 200,
				'list'            => 8,
			),
			// Conversions (leads) from organic search.
			'leads'    => array(
				'min_prev' => 10,
				'trigger'  => -25,
				'clear'    => -10,
				'high'     => -50,
			),
			// A conversion event that stopped recording while visits continued.
			'tracking' => array(
				'min_before'   => 8,
				'min_sessions' => 20,
			),
			// GA4 organic sessions, only for sites without Search Console.
			'sessions' => array(
				'min_prev' => 100,
				'trigger'  => -20,
				'clear'    => -10,
				'high'     => -40,
			),
			// No Google clicks at all.
			'zero'     => array(
				'min_prev' => 20,
			),
		);

		if ( self::RELAXED === $sensitivity ) {
			foreach ( $rules as $name => $rule ) {
				foreach ( $rule as $key => $value ) {
					if ( in_array( $key, array( 'trigger', 'clear', 'high', 'worse' ), true ) ) {
						$rules[ $name ][ $key ] = max( -95, $value * 1.5 );
					} elseif ( 0 === strpos( $key, 'min_' ) ) {
						$rules[ $name ][ $key ] = $value * 2;
					}
				}
			}
		}

		/**
		 * Filters the Client Monitor's thresholds.
		 *
		 * Percentages are negative (−20 means "down 20%"). Volume floors are
		 * the minimum in the earlier period for a change to count.
		 *
		 * @param array  $rules       Rules keyed by check.
		 * @param string $sensitivity standard|relaxed.
		 */
		return (array) apply_filters( 'turtlereport_attention_rules', $rules, $sensitivity );
	}

	/**
	 * Percentage change from $before to $now, or null with nothing to compare.
	 *
	 * @param float $now    Now.
	 * @param float $before Before.
	 * @return float|null
	 */
	public static function change( $now, $before ) {
		return $before > 0 ? ( ( $now - $before ) / $before ) * 100 : null;
	}
}