<?php
/**
 * Builds the public representation of a dashboard.
 *
 * @package PulseCast
 */

namespace PulseCast\Rest;

use PulseCast\Domain\Dashboard;
use PulseCast\Domain\Feed_List;
use PulseCast\Feeds\Feed_Cache;
use PulseCast\Feeds\Refresh_Policy;
use PulseCast\Support\Settings_Schema;

/**
 * Reads cached items only (never the network) and returns an explicit whitelist of fields.
 *
 * Output: `v`, `status` (ok, stale or pending), `feed_count`, `updated` (ISO 8601 or null), `settings` (the
 * public settings), and `items`, each with exactly `id`, `title`, `summary`, `url`, `image`,
 * `source`, `color` (validated `#rrggbb`, or empty for automatic) and `published` (ISO 8601 or null). Feed URLs, dashboard IDs, errors, intervals and
 * every other internal value are never included.
 */
final class Payload_Builder {

	public const VERSION = 1;

	/**
	 * Feed cache.
	 *
	 * @var Feed_Cache
	 */
	private Feed_Cache $cache;

	/**
	 * Constructor.
	 *
	 * @param Feed_Cache $cache Feed cache.
	 */
	public function __construct( Feed_Cache $cache ) {
		$this->cache = $cache;
	}

	/**
	 * Builds the public payload.
	 *
	 * @param Dashboard $dashboard Dashboard.
	 * @param int       $now       Current Unix time.
	 * @return array<string,mixed>
	 */
	public function build( Dashboard $dashboard, int $now ): array {
		$settings = $dashboard->settings;
		$interval = (int) $settings['refresh_interval'] * 60;
		$items    = array();
		$seen     = array();
		$statuses = array();
		$updated  = 0;

		foreach ( $dashboard->feeds as $feed ) {
			$entry = $this->cache->get( $feed['url'] );

			$statuses[] = Refresh_Policy::status( $entry, $interval, $now );

			if ( null === $entry ) {
				continue;
			}

			$updated = max( $updated, $entry['fetched_at'] );

			foreach ( $entry['items'] as $item ) {
				if ( ! is_array( $item ) || ! is_string( $item['title'] ?? null ) ) {
					continue;
				}

				$dedupe = ( is_string( $item['url'] ?? null ) && '' !== $item['url'] ) ? $item['url'] : (string) ( $item['id'] ?? $item['title'] );

				if ( isset( $seen[ $dedupe ] ) ) {
					continue;
				}

				$seen[ $dedupe ] = true;
				$items[]         = array(
					'id'        => (string) ( $item['id'] ?? '' ),
					'title'     => $item['title'],
					'summary'   => (string) ( $item['summary'] ?? '' ),
					'url'       => (string) ( $item['url'] ?? '' ),
					'image'     => (string) ( $item['image'] ?? '' ),
					'source'    => '' !== $feed['label'] ? $feed['label'] : (string) ( $item['source'] ?? '' ),
					'color'     => Feed_List::sanitize_color( $feed['color'] ?? '' ),
					'published' => (int) ( $item['published'] ?? 0 ),
				);
			}//end foreach
		}//end foreach

		// Newest first; undated items last. usort is stable.
		usort(
			$items,
			static function ( array $a, array $b ): int {
				if ( 0 === $a['published'] || 0 === $b['published'] ) {
					return ( 0 === $a['published'] ) <=> ( 0 === $b['published'] );
				}

				return $b['published'] <=> $a['published'];
			}
		);

		$has_items = array() !== $items;
		$items     = array_slice( $items, 0, (int) $settings['max_items'] );

		foreach ( $items as $index => $item ) {
			$items[ $index ]['published'] = $item['published'] > 0 ? self::iso( $item['published'] ) : null;
		}

		return array(
			'v'          => self::VERSION,
			'status'     => self::status( $has_items, $statuses ),
			'feed_count' => count( $dashboard->feeds ),
			'updated'    => $updated > 0 ? self::iso( $updated ) : null,
			'settings'   => Settings_Schema::public_settings( $settings ),
			'items'      => $items,
		);
	}

	/**
	 * Overall status: pending until there is content, stale if any feed is stale or failing.
	 *
	 * @param bool              $has_items Whether any item is cached.
	 * @param array<int,string> $statuses  Per-feed status.
	 */
	private static function status( bool $has_items, array $statuses ): string {
		if ( ! $has_items ) {
			return 'pending';
		}

		foreach ( $statuses as $status ) {
			if ( Refresh_Policy::STATUS_STALE === $status || Refresh_Policy::STATUS_FAILING === $status ) {
				return 'stale';
			}
		}

		return 'ok';
	}

	/**
	 * ISO 8601 UTC time.
	 *
	 * @param int $timestamp Unix time.
	 */
	private static function iso( int $timestamp ): string {
		return gmdate( 'Y-m-d\TH:i:s\Z', $timestamp );
	}
}