<?php
declare( strict_types=1 );
/**
 * Click analytics tracking and reporting.
 *
 * Handles recording click events, aggregating daily stats,
 * and generating trend/topic reports.
 *
 * @since 1.0.0
 */
class Peptide_News_Analytics {

	/**
	 * Record a click event for an article.
	 *
	 * @param int    $article_id
	 * @param array  $meta  Additional context (IP, UA, referrer, etc.).
	 * @return bool
	 */
	public static function record_click( int $article_id, array $meta = array() ): bool {
		global $wpdb;

		$table = $wpdb->prefix . 'peptide_news_clicks';

		$ip = isset( $meta['ip'] ) ? $meta['ip'] : self::get_client_ip();

		// Skip recording if no valid IP is available.
		if ( null === $ip ) {
			return false;
		}

		// Optionally anonymize IP (GDPR-friendly).
		if ( get_option( 'peptide_news_anonymize_ip', 1 ) ) {
			$ip = self::anonymize_ip( $ip );
		}

		$data = array(
			'article_id'  => absint( $article_id ),
			'clicked_at'  => current_time( 'mysql' ),
			'user_ip'     => sanitize_text_field( $ip ),
			'user_agent'  => sanitize_text_field( isset( $meta['user_agent'] ) ? $meta['user_agent'] : '' ),
			'referrer_url' => esc_url_raw( isset( $meta['referrer'] ) ? $meta['referrer'] : '' ),
			'page_url'    => esc_url_raw( isset( $meta['page_url'] ) ? $meta['page_url'] : '' ),
			'session_id'  => sanitize_text_field( isset( $meta['session_id'] ) ? $meta['session_id'] : '' ),
			'user_id'     => is_user_logged_in() ? get_current_user_id() : null,
			'device_type' => sanitize_text_field( self::detect_device( isset( $meta['user_agent'] ) ? $meta['user_agent'] : '' ) ),
		);

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

		// Update daily aggregate.
		if ( false !== $result ) {
			self::update_daily_stats( $article_id, $ip );
		}

		return false !== $result;
	}

	/**
	 * Update daily aggregated stats.
	 *
	 * @param int    $article_id
	 * @param string $ip  Anonymized IP for unique visitor counting.
	 */
	private static function update_daily_stats( int $article_id, string $ip ): void {
		global $wpdb;

		$table     = $wpdb->prefix . 'peptide_news_daily_stats';
		$today     = current_time( 'Y-m-d' );
		$clicks_tbl = $wpdb->prefix . 'peptide_news_clicks';

		// Upsert daily click count.
		$existing = $wpdb->get_row( $wpdb->prepare(
			"SELECT id, click_count FROM {$table} WHERE article_id = %d AND stat_date = %s",
			$article_id,
			$today
		) );

		// Count unique IPs for today.
		$unique = $wpdb->get_var( $wpdb->prepare(
			"SELECT COUNT(DISTINCT user_ip) FROM {$clicks_tbl} WHERE article_id = %d AND DATE(clicked_at) = %s",
			$article_id,
			$today
		) );

		if ( $existing ) {
			$wpdb->update(
				$table,
				array(
					'click_count'     => $existing->click_count + 1,
					'unique_visitors' => (int) $unique,
				),
				array( 'id' => $existing->id ),
				array( '%d', '%d' ),
				array( '%d' )
			);
		} else {
			$wpdb->insert(
				$table,
				array(
					'article_id'      => $article_id,
					'stat_date'       => $today,
					'click_count'     => 1,
					'unique_visitors' => 1,
				)
			);
		}
	}

	/**
	 * Get top articles by click count within a date range.
	 *
	 * @param string $start_date  Y-m-d
	 * @param string $end_date    Y-m-d
	 * @param int    $limit
	 * @return array
	 */
	public static function get_top_articles( string $start_date, string $end_date, int $limit = 20 ): array {
		global $wpdb;

		$stats_table    = $wpdb->prefix . 'peptide_news_daily_stats';
		$articles_table = $wpdb->prefix . 'peptide_news_articles';

		return $wpdb->get_results( $wpdb->prepare(
			"SELECT a.id, a.title, a.source, a.source_url, a.thumbnail_url, a.categories, a.published_at,
					SUM(s.click_count) AS total_clicks,
					SUM(s.unique_visitors) AS total_unique
			 FROM {$stats_table} s
			 INNER JOIN {$articles_table} a ON a.id = s.article_id
			 WHERE s.stat_date BETWEEN %s AND %s
			 GROUP BY a.id
			 ORDER BY total_clicks DESC
			 LIMIT %d",
			$start_date,
			$end_date,
			$limit
		) );
	}

	/**
	 * Get click trends over time (daily totals).
	 *
	 * @param string $start_date
	 * @param string $end_date
	 * @return array
	 */
	public static function get_click_trends( string $start_date, string $end_date ): array {
		global $wpdb;

		$table = $wpdb->prefix . 'peptide_news_daily_stats';

		return $wpdb->get_results( $wpdb->prepare(
			"SELECT stat_date, SUM(click_count) AS total_clicks, SUM(unique_visitors) AS total_unique
			 FROM {$table}
			 WHERE stat_date BETWEEN %s AND %s
			 GROUP BY stat_date
			 ORDER BY stat_date ASC",
			$start_date,
			$end_date
		) );
	}

	/**
	 * Get popular topics/categories by click volume.
	 *
	 * @param string $start_date
	 * @param string $end_date
	 * @param int    $limit
	 * @return array
	 */
	public static function get_popular_topics( string $start_date, string $end_date, int $limit = 20 ): array {
		global $wpdb;

		$stats_table    = $wpdb->prefix . 'peptide_news_daily_stats';
		$articles_table = $wpdb->prefix . 'peptide_news_articles';

		// Get articles with their click counts.
		$rows = $wpdb->get_results( $wpdb->prepare(
			"SELECT a.categories, a.title, SUM(s.click_count) AS clicks
			 FROM {$stats_table} s
			 INNER JOIN {$articles_table} a ON a.id = s.article_id
			 WHERE s.stat_date BETWEEN %s AND %s AND a.categories != ''
			 GROUP BY a.id
			 ORDER BY clicks DESC",
			$start_date,
			$end_date
		) );

		// Aggregate by category.
		$topics = array();
		foreach ( $rows as $row ) {
			$cats = array_map( 'trim', explode( ',', $row->categories ) );
			foreach ( $cats as $cat ) {
				if ( empty( $cat ) ) {
					continue;
				}
				$cat_lower = strtolower( $cat );
				if ( ! isset( $topics[ $cat_lower ] ) ) {
					$topics[ $cat_lower ] = array(
						'topic'         => $cat,
						'total_clicks'  => 0,
						'article_count' => 0,
					);
				}
				$topics[ $cat_lower ]['total_clicks']  += (int) $row->clicks;
				$topics[ $cat_lower ]['article_count'] += 1;
			}
		}

		// Sort by clicks.
		usort( $topics, function ( $a, $b ) {
			return $b['total_clicks'] - $a['total_clicks'];
		} );

		return array_slice( $topics, 0, $limit );
	}

	/**
	 * Get device breakdown stats.
	 *
	 * @param string $start_date
	 * @param string $end_date
	 * @return array
	 */
	public static function get_device_breakdown( string $start_date, string $end_date ): array {
		global $wpdb;

		$table = $wpdb->prefix . 'peptide_news_clicks';

		return $wpdb->get_results( $wpdb->prepare(
			"SELECT device_type, COUNT(*) AS click_count
			 FROM {$table}
			 WHERE DATE(clicked_at) BETWEEN %s AND %s
			 GROUP BY device_type
			 ORDER BY click_count DESC",
			$start_date,
			$end_date
		) );
	}

	/**
	 * Get source performance stats.
	 *
	 * @param string $start_date
	 * @param string $end_date
	 * @return array
	 */
	public static function get_source_performance( string $start_date, string $end_date ): array {
		global $wpdb;

		$stats_table    = $wpdb->prefix . 'peptide_news_daily_stats';
		$articles_table = $wpdb->prefix . 'peptide_news_articles';

		return $wpdb->get_results( $wpdb->prepare(
			"SELECT a.source,
					COUNT(DISTINCT a.id) AS article_count,
					SUM(s.click_count) AS total_clicks,
					ROUND(IFNULL(SUM(s.click_count) / NULLIF(COUNT(DISTINCT a.id), 0), 0), 1) AS avg_clicks_per_article
			 FROM {$stats_table} s
			 INNER JOIN {$articles_table} a ON a.id = s.article_id
			 WHERE s.stat_date BETWEEN %s AND %s
			 GROUP BY a.source
			 ORDER BY total_clicks DESC",
			$start_date,
			$end_date
		) );
	}

	/**
	 * Hard cap on CSV export rows to prevent memory exhaustion on large datasets.
	 *
	 * @var int
	 */
	const CSV_EXPORT_MAX_ROWS = 50000;

	/**
	 * Export click data as CSV-ready array.
	 *
	 * Capped at CSV_EXPORT_MAX_ROWS to prevent memory exhaustion on sites
	 * with large click volumes. The cap is applied at the SQL level so
	 * only the limited result set is ever loaded into PHP memory.
	 *
	 * @param string $start_date Y-m-d format.
	 * @param string $end_date   Y-m-d format.
	 * @return array Array of associative arrays (one per click row).
	 */
	public static function export_clicks_csv( string $start_date, string $end_date ): array {
		global $wpdb;

		$clicks_table   = $wpdb->prefix . 'peptide_news_clicks';
		$articles_table = $wpdb->prefix . 'peptide_news_articles';

		return $wpdb->get_results( $wpdb->prepare(
			"SELECT c.clicked_at, a.title, a.source, a.source_url, a.categories,
					c.referrer_url, c.page_url, c.device_type, c.session_id
			 FROM {$clicks_table} c
			 INNER JOIN {$articles_table} a ON a.id = c.article_id
			 WHERE DATE(c.clicked_at) BETWEEN %s AND %s
			 ORDER BY c.clicked_at DESC
			 LIMIT %d",
			$start_date,
			$end_date,
			self::CSV_EXPORT_MAX_ROWS
		), ARRAY_A );
	}

	/**
	 * Get the client IP address.
	 *
	 * @return string|null
	 */
	private static function get_client_ip(): ?string {
		$ip_keys = array( 'HTTP_CF_CONNECTING_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_REAL_IP', 'REMOTE_ADDR' );

		foreach ( $ip_keys as $key ) {
			if ( ! empty( $_SERVER[ $key ] ) ) {
				$ip = explode( ',', sanitize_text_field( wp_unslash( $_SERVER[ $key ] ) ) );
				$ip = trim( $ip[0] );
				if ( filter_var( $ip, FILTER_VALIDATE_IP ) ) {
					return $ip;
				}
			}
		}

		return null;
	}

	/**
	 * Anonymize an IP address (zero out last octet for IPv4, last 80 bits for IPv6).
	 *
	 * @param string $ip
	 * @return string
	 */
	private static function anonymize_ip( string $ip ): string {
		if ( filter_var( $ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4 ) ) {
			return preg_replace( '/\.\d+$/', '.0', $ip );
		}
		if ( filter_var( $ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6 ) ) {
			return substr( $ip, 0, strrpos( $ip, ':' ) ) . ':0000';
		}
		return '0.0.0.0';
	}

	/**
	 * Simple device detection from user agent.
	 *
	 * @param string $ua
	 * @return string
	 */
	private static function detect_device( string $ua ): string {
		$ua = strtolower( $ua );

		if ( preg_match( '/(tablet|ipad|playbook|silk)/', $ua ) ) {
			return 'tablet';
		}
		if ( preg_match( '/(mobile|android|iphone|ipod|phone|blackberry|opera mini|iemobile)/', $ua ) ) {
			return 'mobile';
		}
		if ( preg_match( '/(bot|crawl|spider|slurp|wget|curl)/', $ua ) ) {
			return 'bot';
		}

		return 'desktop';
	}
}