<?php
/**
 * Email Statistics Management Class
 *
 * Manages campaign performance metrics and historical data.
 *
 * @package ROBOTSTXT_SMTP_Newsletter
 * @since 2.2.0
 */

namespace Robotstxt_SMTP_Newsletter;

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

/**
 * Statistics management class.
 *
 * Handles aggregation, persistence, and querying of email campaign metrics.
 */
class Statistics {

	/**
	 * Table name (without prefix).
	 *
	 * @var string
	 */
	private const TABLE_NAME = 'robotstxt_smtp_newsletter_stats';

	/**
	 * Database version for migrations.
	 *
	 * @var string
	 */
	private const DB_VERSION = '1.1';

	/**
	 * Option name for database version tracking.
	 *
	 * @var string
	 */
	private const DB_VERSION_OPTION = 'robotstxt_smtp_newsletter_stats_db_version';

	/**
	 * Singleton instance.
	 *
	 * @var Statistics|null
	 */
	private static $instance = null;

	/**
	 * Get singleton instance.
	 *
	 * @return Statistics
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * Constructor.
	 *
	 * Ensures table is created on instantiation.
	 */
	private function __construct() {
		$this->maybe_create_table();
	}

	/**
	 * Get full table name with WordPress prefix.
	 *
	 * @return string
	 */
	public static function get_table_name() {
		global $wpdb;
		return $wpdb->prefix . self::TABLE_NAME;
	}

	/**
	 * Create or upgrade table if needed.
	 *
	 * @return void
	 */
	private function maybe_create_table() {
		$stored_version = get_option( self::DB_VERSION_OPTION, '0' );

		if ( version_compare( $stored_version, self::DB_VERSION, '>=' ) ) {
			return;
		}

		global $wpdb;
		$table_name      = self::get_table_name();
		$charset_collate = $wpdb->get_charset_collate();

		$sql = "CREATE TABLE {$table_name} (
			id                BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
			newsletter_id     BIGINT UNSIGNED NULL,
			campaign_name     VARCHAR(255) NULL,
			provider          VARCHAR(32) NOT NULL,
			total_emails      INT UNSIGNED NOT NULL DEFAULT 0,
			sent_emails       INT UNSIGNED NOT NULL DEFAULT 0,
			failed_emails     INT UNSIGNED NOT NULL DEFAULT 0,
			started_at        DATETIME(6) NULL,
			finished_at       DATETIME(6) NULL,
			duration_seconds  FLOAT NULL,
			emails_per_hour   FLOAT NULL,
			emails_per_minute FLOAT NULL,
			created_at        DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
			updated_at        DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
			PRIMARY KEY  (id),
			UNIQUE KEY idx_newsletter_unique (newsletter_id),
			KEY idx_created (created_at),
			KEY idx_finished (finished_at)
		) {$charset_collate} ENGINE=InnoDB;";

		require_once ABSPATH . 'wp-admin/includes/upgrade.php';
		dbDelta( $sql );

		update_option( self::DB_VERSION_OPTION, self::DB_VERSION );
	}

	/**
	 * Start tracking a new campaign.
	 *
	 * @param int    $newsletter_id Newsletter ID.
	 * @param string $campaign_name Campaign display name.
	 * @param int    $total_emails  Total emails to send.
	 *
	 * @return int|false Inserted stat ID on success, false on failure.
	 */
	public function start_campaign( $newsletter_id, $campaign_name, $total_emails ) {
		global $wpdb;
		$table = self::get_table_name();

		$data = array(
			'newsletter_id' => $newsletter_id,
			'campaign_name' => $campaign_name,
			'provider'      => $this->get_provider_name(),
			'total_emails'  => absint( $total_emails ),
			'started_at'    => current_time( 'mysql', true ),
		);

		$format = array( '%d', '%s', '%s', '%d', '%s' );

		$result = $wpdb->insert( $table, $data, $format );

		return $result ? $wpdb->insert_id : false;
	}

	/**
	 * Update campaign progress.
	 *
	 * @param int $stat_id Stat ID.
	 * @param int $sent    Number of emails sent.
	 * @param int $failed  Number of emails failed.
	 *
	 * @return bool Success status.
	 */
	public function update_campaign_progress( $stat_id, $sent, $failed ) {
		global $wpdb;
		$table = self::get_table_name();

		$data = array(
			'sent_emails'   => absint( $sent ),
			'failed_emails' => absint( $failed ),
		);

		$format = array( '%d', '%d' );

		return false !== $wpdb->update( $table, $data, array( 'id' => $stat_id ), $format, array( '%d' ) );
	}

	/**
	 * Mark campaign as finished and calculate final metrics.
	 *
	 * @param int $stat_id Stat ID.
	 *
	 * @return bool Success status.
	 */
	public function finish_campaign( $stat_id ) {
		global $wpdb;
		$table = self::get_table_name();

		// Get campaign data.
		$campaign = $wpdb->get_row(
			$wpdb->prepare(
				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name is safe.
				"SELECT started_at, sent_emails FROM {$table} WHERE id = %d",
				$stat_id
			)
		);

		if ( ! $campaign || ! $campaign->started_at ) {
			return false;
		}

		$finished_at = current_time( 'mysql', true );
		$start_time  = strtotime( $campaign->started_at );
		$finish_time = strtotime( $finished_at );
		$duration    = max( 1, $finish_time - $start_time );

		$emails_per_hour   = ( $campaign->sent_emails / $duration ) * 3600;
		$emails_per_minute = ( $campaign->sent_emails / $duration ) * 60;

		$data = array(
			'finished_at'       => $finished_at,
			'duration_seconds'  => $duration,
			'emails_per_hour'   => $emails_per_hour,
			'emails_per_minute' => $emails_per_minute,
		);

		$format = array( '%s', '%f', '%f', '%f' );

		return false !== $wpdb->update( $table, $data, array( 'id' => $stat_id ), $format, array( '%d' ) );
	}

	/**
	 * Synchronize statistics from queue table.
	 *
	 * Aggregates queue data and updates/creates statistics records.
	 * This preserves metrics even after queue cleanup.
	 *
	 * @param int|null $newsletter_id Optional newsletter ID to sync (null = all).
	 *
	 * @return void
	 */
	public function sync_from_queue( $newsletter_id = null ) {
		global $wpdb;
		$queue_table = Queue::get_table_name();
		$stats_table = self::get_table_name();

		$where = $newsletter_id ? $wpdb->prepare( 'WHERE newsletter_id = %d', $newsletter_id ) : 'WHERE newsletter_id IS NOT NULL';

		$campaigns = $wpdb->get_results(
			// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- WHERE clause is safe.
			"SELECT
				newsletter_id,
				MAX(campaign_name) as campaign_name,
				MAX(provider) as provider,
				MIN(created_at) as started_at,
				MAX(sent_at) as finished_at,
				COUNT(*) as total_emails,
				SUM(CASE WHEN sent_at IS NOT NULL THEN 1 ELSE 0 END) as sent_emails,
				SUM(CASE WHEN attempts >= 3 AND sent_at IS NULL THEN 1 ELSE 0 END) as failed_emails
			FROM {$queue_table}
			{$where}
			GROUP BY newsletter_id"
		);

		foreach ( $campaigns as $campaign ) {
			$duration      = null;
			$per_hour      = null;
			$per_minute    = null;

			if ( $campaign->finished_at && $campaign->started_at ) {
				$start    = strtotime( $campaign->started_at );
				$finish   = strtotime( $campaign->finished_at );
				$duration = max( 1, $finish - $start );

				if ( $duration > 0 && $campaign->sent_emails > 0 ) {
					$per_hour   = ( $campaign->sent_emails / $duration ) * 3600;
					$per_minute = ( $campaign->sent_emails / $duration ) * 60;
				}
			}

			// Check if stat record exists (by newsletter_id only).
			$existing = $wpdb->get_var(
				$wpdb->prepare(
					// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name is safe.
					"SELECT id FROM {$stats_table} WHERE newsletter_id = %d",
					$campaign->newsletter_id
				)
			);

			if ( $existing ) {
				// Update existing.
				$wpdb->update(
					$stats_table,
					array(
						'total_emails'      => $campaign->total_emails,
						'sent_emails'       => $campaign->sent_emails,
						'failed_emails'     => $campaign->failed_emails,
						'started_at'        => $campaign->started_at,
						'finished_at'       => $campaign->finished_at,
						'duration_seconds'  => $duration,
						'emails_per_hour'   => $per_hour,
						'emails_per_minute' => $per_minute,
					),
					array( 'id' => $existing ),
					array( '%d', '%d', '%d', '%s', '%s', '%f', '%f', '%f' ),
					array( '%d' )
				);
			} else {
				// Insert new.
				$wpdb->insert(
					$stats_table,
					array(
						'newsletter_id'     => $campaign->newsletter_id,
						'campaign_name'     => $campaign->campaign_name,
						'provider'          => $campaign->provider,
						'total_emails'      => $campaign->total_emails,
						'sent_emails'       => $campaign->sent_emails,
						'failed_emails'     => $campaign->failed_emails,
						'started_at'        => $campaign->started_at,
						'finished_at'       => $campaign->finished_at,
						'duration_seconds'  => $duration,
						'emails_per_hour'   => $per_hour,
						'emails_per_minute' => $per_minute,
					),
					array( '%d', '%s', '%s', '%d', '%d', '%d', '%s', '%s', '%f', '%f', '%f' )
				);
			}
		}
	}

	/**
	 * Get statistics for a specific campaign.
	 *
	 * @param int $newsletter_id Newsletter ID.
	 *
	 * @return object|null Campaign statistics or null if not found.
	 */
	public function get_campaign_stats( $newsletter_id ) {
		global $wpdb;
		$table = self::get_table_name();

		return $wpdb->get_row(
			$wpdb->prepare(
				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name is safe.
				"SELECT * FROM {$table}
				WHERE newsletter_id = %d
				ORDER BY created_at DESC
				LIMIT 1",
				$newsletter_id
			)
		);
	}

	/**
	 * Get recent campaigns.
	 *
	 * @param int $limit Maximum results.
	 *
	 * @return object[] Array of campaign statistics.
	 */
	public function get_recent_campaigns( $limit = 10 ) {
		global $wpdb;
		$table = self::get_table_name();

		return $wpdb->get_results(
			$wpdb->prepare(
				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name is safe.
				"SELECT * FROM {$table}
				ORDER BY created_at DESC
				LIMIT %d",
				$limit
			)
		);
	}

	/**
	 * Get global statistics.
	 *
	 * @param int $days Number of days to aggregate.
	 *
	 * @return array{total_sent: int, total_failed: int, avg_emails_per_hour: float}
	 */
	public function get_global_stats( $days = 30 ) {
		global $wpdb;
		$table = self::get_table_name();

		$stats = $wpdb->get_row(
			$wpdb->prepare(
				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name is safe.
				"SELECT
					SUM(sent_emails) as total_sent,
					SUM(failed_emails) as total_failed,
					AVG(emails_per_hour) as avg_emails_per_hour
				FROM {$table}
				WHERE created_at >= DATE_SUB(NOW(), INTERVAL %d DAY)",
				$days
			),
			ARRAY_A
		);

		return array(
			'total_sent'          => absint( $stats['total_sent'] ?? 0 ),
			'total_failed'        => absint( $stats['total_failed'] ?? 0 ),
			'avg_emails_per_hour' => floatval( $stats['avg_emails_per_hour'] ?? 0 ),
		);
	}

	/**
	 * Delete statistics for a campaign.
	 *
	 * @param int $newsletter_id Newsletter ID.
	 *
	 * @return int Number of records deleted.
	 */
	public function delete_campaign_stats( $newsletter_id ) {
		global $wpdb;
		$table = self::get_table_name();

		$result = $wpdb->delete( $table, array( 'newsletter_id' => $newsletter_id ), array( '%d' ) );

		return absint( $result );
	}

	/**
	 * Get current provider name.
	 *
	 * @return string Provider identifier.
	 */
	private function get_provider_name() {
		if ( ! class_exists( '\Robotstxt_SMTP\Plugin' ) ) {
			return 'unknown';
		}

		$is_ses = \Robotstxt_SMTP\Plugin::is_amazon_ses_integration_active();

		return $is_ses ? 'amazonses' : 'postfix';
	}
}