<?php
/**
 * TMDO_Email_Notifier — Threshold-based email alerts (v2.4.0 M10).
 *
 * Subscribes to action `wpdo/health_alert_critical` (fired by Health_Cron M6
 * when critical_count > 0). Sends a plain-text email to the configured
 * recipient(s) with a 24h throttle key (per-alert-fingerprint) so admins
 * don't get spammed.
 *
 * Default OFF — admin must explicitly enable via Settings tab.
 *
 * @package WP_Data_Optimizer
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Email notifier — stateless static API.
 */
class TMDO_Email_Notifier {

	public const OPT_ENABLED      = 'wpdo_email_alerts_enabled';
	public const OPT_RECIPIENT    = 'wpdo_alert_email';
	public const OPT_THROTTLE_HRS = 'wpdo_alert_throttle_hours';

	/** Default throttle window. */
	public const DEFAULT_THROTTLE_HOURS = 24;

	/**
	 * Register subscriber.
	 *
	 * @return void
	 */
	public static function register(): void {
		add_action( 'wpdo/health_alert_critical', array( __CLASS__, 'maybe_send' ), 10, 1 );
	}

	/**
	 * Decide + send.
	 *
	 * @param array $summary Health summary from Health_Cron::run().
	 * @return bool true on send, false on skip / fail.
	 */
	public static function maybe_send( array $summary ): bool {
		if ( ! self::is_enabled() ) {
			return false;
		}
		$recipient = self::recipient();
		if ( ! is_email( $recipient ) ) {
			return false;
		}
		$fingerprint = self::fingerprint( $summary );
		if ( self::is_throttled( $fingerprint ) ) {
			return false;
		}
		$subject = self::build_subject( $summary );
		$body    = self::build_body( $summary );
		$sent    = wp_mail( $recipient, $subject, $body );
		if ( $sent ) {
			self::mark_sent( $fingerprint );
			if ( class_exists( 'TMDO_Logger' ) ) {
				TMDO_Logger::info(
					'email_alert_sent',
					array(
						'fingerprint' => $fingerprint,
						'critical'    => (int) ( $summary['critical_count'] ?? 0 ),
						'recipient'   => $recipient,
					)
				);
			}
		}
		return (bool) $sent;
	}

	// ─── settings accessors ─────────────────────────────────────────────

	/**
	 * Whether email alerts are enabled.
	 *
	 * @return bool
	 */
	public static function is_enabled(): bool {
		return '1' === (string) get_option( self::OPT_ENABLED, '0' );
	}

	/**
	 * Alert recipient email address (falls back to admin_email).
	 *
	 * @return string
	 */
	public static function recipient(): string {
		$v = (string) get_option( self::OPT_RECIPIENT, '' );
		if ( '' === $v ) {
			$v = (string) get_option( 'admin_email', '' );
		}
		return $v;
	}

	/**
	 * Throttle window in hours (clamped 1..168).
	 *
	 * @return int
	 */
	public static function throttle_hours(): int {
		$v = (int) get_option( self::OPT_THROTTLE_HRS, self::DEFAULT_THROTTLE_HOURS );
		return max( 1, min( 168, $v ) ); // Clamp 1h..1week.
	}

	// ─── private helpers ──────────────────────────────────────────────

	/**
	 * Stable fingerprint from the alert content (so identical incidents
	 * dedupe within the throttle window).
	 *
	 * @param array $summary Summary array.
	 * @return string md5 hash.
	 */
	private static function fingerprint( array $summary ): string {
		$relevant = array(
			'critical_count' => (int) ( $summary['critical_count'] ?? 0 ),
			'first_critical' => null,
		);
		foreach ( (array) ( $summary['tests'] ?? array() ) as $slug => $t ) {
			if ( 'critical' === ( $t['status'] ?? '' ) ) {
				$relevant['first_critical'] = $slug;
				break;
			}
		}
		return md5( wp_json_encode( $relevant ) );
	}

	/**
	 * Check whether an alert with this fingerprint was recently sent.
	 *
	 * @param string $fingerprint Alert fingerprint (md5).
	 * @return bool
	 */
	private static function is_throttled( string $fingerprint ): bool {
		$key = 'wpdo_alert_sent_' . $fingerprint;
		return false !== get_transient( $key );
	}

	/**
	 * Record that an alert was sent (sets throttle transient).
	 *
	 * @param string $fingerprint Alert fingerprint (md5).
	 * @return void
	 */
	private static function mark_sent( string $fingerprint ): void {
		$key = 'wpdo_alert_sent_' . $fingerprint;
		set_transient( $key, time(), self::throttle_hours() * HOUR_IN_SECONDS );
	}

	/**
	 * Build subject. Site name + critical count + first slug.
	 *
	 * @param array $summary Summary array.
	 * @return string
	 */
	private static function build_subject( array $summary ): string {
		$site  = (string) get_option( 'blogname', 'WordPress' );
		$crit  = (int) ( $summary['critical_count'] ?? 0 );
		$first = '';
		foreach ( (array) ( $summary['tests'] ?? array() ) as $slug => $t ) {
			if ( 'critical' === ( $t['status'] ?? '' ) ) {
				$first = $slug;
				break;
			}
		}
		return sprintf(
			/* translators: 1: site name, 2: critical count, 3: first critical test slug */
			__( '[%1$s] WPDO 警告：%2$d 項 critical (%3$s)', '2meet-data-optimizer' ),
			$site,
			$crit,
			$first
		);
	}

	/**
	 * Build plain-text body.
	 *
	 * @param array $summary Summary array.
	 * @return string
	 */
	private static function build_body( array $summary ): string {
		$site_url   = home_url( '/' );
		$health_url = admin_url( 'site-health.php' );
		$wpdo_url   = admin_url( 'tools.php?page=wp-data-optimizer&tab=doctor' );
		$lines      = array();
		$lines[]    = __( 'WP Data Optimizer 自動健康檢查發現 critical 警告。', '2meet-data-optimizer' );
		$lines[]    = '';
		$lines[]    = sprintf( '站台：%s', $site_url );
		$lines[]    = sprintf(
			/* translators: %s: timestamp */
			__( '檢查時間：%s UTC', '2meet-data-optimizer' ),
			(string) ( $summary['ran_at'] ?? '?' )
		);
		$lines[] = sprintf(
			/* translators: 1: critical count, 2: recommended count */
			__( '結果：%1$d critical / %2$d recommended', '2meet-data-optimizer' ),
			(int) ( $summary['critical_count'] ?? 0 ),
			(int) ( $summary['recommended_count'] ?? 0 )
		);
		$lines[] = '';
		$lines[] = __( '失敗的檢查：', '2meet-data-optimizer' );
		foreach ( (array) ( $summary['tests'] ?? array() ) as $slug => $t ) {
			if ( in_array( ( $t['status'] ?? '' ), array( 'critical', 'recommended' ), true ) ) {
				$lines[] = sprintf(
					'  [%s] %s — %s',
					strtoupper( (string) $t['status'] ),
					$slug,
					(string) ( $t['description'] ?? '' )
				);
			}
		}
		$lines[] = '';
		$lines[] = __( '建議行動：', '2meet-data-optimizer' );
		$lines[] = '  · ' . sprintf(
			/* translators: %s: WPDO Doctor admin URL */
			__( '立即查看 WPDO Doctor：%s', '2meet-data-optimizer' ),
			$wpdo_url
		);
		$lines[] = '  · ' . sprintf(
			/* translators: %s: WP Site Health admin URL */
			__( '或 WP Site Health：%s', '2meet-data-optimizer' ),
			$health_url
		);
		$lines[] = '';
		$lines[] = sprintf(
			/* translators: %d: hours */
			__( '註：相同警告在 %d 小時內不會重發；前往設定可調整 throttle / 收件人 / 關閉。', '2meet-data-optimizer' ),
			self::throttle_hours()
		);
		return implode( "\n", $lines );
	}
}