<?php
/**
 * Feed health monitor.
 *
 * Checks product data against each feed format's required and
 * recommended fields to flag missing data that could affect
 * feed quality or platform acceptance.
 *
 * @package AICommerce\Feed
 */

declare(strict_types=1);

namespace AICommerce\Feed;

/**
 * Monitors feed data quality and flags missing required fields.
 */
class FeedHealthMonitor {

	/**
	 * Check the health of products for a specific feed format.
	 *
	 * @param AbstractFeed $feed     The feed format.
	 * @param array        $products Array of normalized product data.
	 *
	 * @return array Health report.
	 */
	public function check_feed( AbstractFeed $feed, array $products ): array {
		$total          = count( $products );
		$valid_count    = 0;
		$missing_fields = array();
		$warnings       = array();

		foreach ( $products as $product ) {
			$validation = $feed->validate_product( $product );

			if ( $validation['valid'] ) {
				++$valid_count;
			} else {
				foreach ( $validation['missing'] as $field ) {
					if ( ! isset( $missing_fields[ $field ] ) ) {
						$missing_fields[ $field ] = 0;
					}
					++$missing_fields[ $field ];
				}
			}

			// Check recommended fields.
			foreach ( $feed->get_recommended_fields() as $field ) {
				if ( empty( $product[ $field ] ) ) {
					if ( ! isset( $warnings[ $field ] ) ) {
						$warnings[ $field ] = 0;
					}
					++$warnings[ $field ];
				}
			}
		}

		$coverage = $total > 0 ? round( ( $valid_count / $total ) * 100, 1 ) : 0;

		return array(
			'feed_type'           => $feed->get_type(),
			'total_products'      => $total,
			'valid_products'      => $valid_count,
			'invalid_products'    => $total - $valid_count,
			'coverage_percent'    => $coverage,
			'missing_required'    => $missing_fields,
			'missing_recommended' => $warnings,
			'status'              => $this->determine_status( $coverage ),
		);
	}

	/**
	 * Check health across all feed formats.
	 *
	 * @param array<string, AbstractFeed> $feeds    Registered feed formats.
	 * @param array                       $products Normalized product data.
	 *
	 * @return array Health reports keyed by feed type.
	 */
	public function check_all( array $feeds, array $products ): array {
		$reports = array();

		foreach ( $feeds as $type => $feed ) {
			$reports[ $type ] = $this->check_feed( $feed, $products );
		}

		return $reports;
	}

	/**
	 * Get a summary of the most common missing fields across all feeds.
	 *
	 * @param array $health_reports Health reports from check_all().
	 *
	 * @return array Sorted list of missing fields with counts.
	 */
	public function get_missing_field_summary( array $health_reports ): array {
		$all_missing = array();

		foreach ( $health_reports as $report ) {
			foreach ( $report['missing_required'] as $field => $count ) {
				if ( ! isset( $all_missing[ $field ] ) ) {
					$all_missing[ $field ] = array(
						'field'       => $field,
						'total_count' => 0,
						'feeds'       => array(),
					);
				}
				$all_missing[ $field ]['total_count'] += $count;
				$all_missing[ $field ]['feeds'][]      = $report['feed_type'];
			}
		}

		// Sort by most impactful (highest count).
		usort(
			$all_missing,
			static function ( array $a, array $b ): int {
				return $b['total_count'] <=> $a['total_count'];
			}
		);

		return $all_missing;
	}

	/**
	 * Determine health status from coverage percentage.
	 *
	 * @param float $coverage Coverage percentage.
	 *
	 * @return string Status: 'healthy', 'warning', or 'critical'.
	 */
	private function determine_status( float $coverage ): string {
		if ( $coverage >= 90 ) {
			return 'healthy';
		}
		if ( $coverage >= 70 ) {
			return 'warning';
		}

		return 'critical';
	}
}