<?php
/**
 * Database clean-up: stored scan results.
 *
 * @package AdminPowerups
 */

namespace SmartWP\AdminPowerups\Modules\DatabaseCleanup;

defined( 'ABSPATH' ) || exit;

/**
 * The last scan, in one option that is never autoloaded (not a transient: an external object
 * cache could evict it mid-scan and lose the cursors). About 5 KB.
 *
 * Shape: `token`, `started`, `finished` (last full scan), `full` (the scan in progress covers
 * every check), `queue` (IDs still being scanned), `sizes` (table
 * sizes read at the start), `failed` (failed scheduled actions, or null) and `checks`: ID =>
 * `count` (-1 = not counted), `done`, `state`, `threshold`, `unavailable`, `scanned_at`,
 * `bytes`, `recheck` (cleaned since; scan again to confirm), `sample_from` (where the count
 * first found rows, or null; the sample starts there).
 *
 * @since 1.0.0
 */
final class Results {

	const OPTION = 'apwc_dbc_results';

	/**
	 * Seconds after which a count is too old to clean on.
	 */
	const FRESH = DAY_IN_SECONDS;

	/**
	 * The stored results, checked.
	 *
	 * @since 1.0.0
	 * @return array{token: string, started: int, finished: int, full: bool, queue: string[], sizes: array<string, array<string, int>>, failed: int|null, checks: array<string, array<string, mixed>>}
	 */
	public static function get(): array {
		$stored = get_option( self::OPTION, array() );
		$stored = is_array( $stored ) ? $stored : array();
		$checks = array();
		foreach ( (array) ( $stored['checks'] ?? array() ) as $id => $entry ) {
			if ( is_string( $id ) && is_array( $entry ) ) {
				$checks[ $id ] = self::entry( $entry );
			}
		}
		return array(
			'token'    => is_string( $stored['token'] ?? null ) ? $stored['token'] : '',
			'started'  => (int) ( $stored['started'] ?? 0 ),
			'finished' => (int) ( $stored['finished'] ?? 0 ),
			'full'     => ! empty( $stored['full'] ),
			'queue'    => array_values( array_filter( (array) ( $stored['queue'] ?? array() ), 'is_string' ) ),
			'sizes'    => is_array( $stored['sizes'] ?? null ) ? $stored['sizes'] : array(),
			'failed'   => isset( $stored['failed'] ) && is_numeric( $stored['failed'] ) ? (int) $stored['failed'] : null,
			'checks'   => $checks,
		);
	}

	/**
	 * One entry with every key.
	 *
	 * @param array<string, mixed> $entry Stored entry.
	 * @return array<string, mixed>
	 */
	private static function entry( array $entry ): array {
		return array(
			'count'       => (int) ( $entry['count'] ?? 0 ),
			'done'        => ! empty( $entry['done'] ),
			'state'       => is_array( $entry['state'] ?? null ) ? $entry['state'] : array(),
			'threshold'   => isset( $entry['threshold'] ) && is_numeric( $entry['threshold'] ) ? (int) $entry['threshold'] : null,
			'unavailable' => is_string( $entry['unavailable'] ?? null ) ? $entry['unavailable'] : '',
			'scanned_at'  => (int) ( $entry['scanned_at'] ?? 0 ),
			'bytes'       => (int) ( $entry['bytes'] ?? 0 ),
			'recheck'     => ! empty( $entry['recheck'] ),
			'sample_from' => self::sample_from( $entry ),
		);
	}

	/**
	 * Where a check's last count first found rows (`t` target index, `from` key just below
	 * them), from a final count state or a stored entry; null when there's none. The sample
	 * starts there (OrphanRowsCheck).
	 *
	 * @since 1.0.0
	 * @param array<string, mixed> $state Count state or stored entry.
	 * @return array{t: int, from: int}|null
	 */
	public static function sample_from( array $state ): ?array {
		$hint = $state['sample_from'] ?? null;
		if ( ! is_array( $hint ) || ! isset( $hint['t'], $hint['from'] ) || ! is_numeric( $hint['t'] ) || ! is_numeric( $hint['from'] ) ) {
			return null;
		}
		return array(
			't'    => (int) $hint['t'],
			'from' => (int) $hint['from'],
		);
	}

	/**
	 * Save.
	 *
	 * @since 1.0.0
	 * @param array<string, mixed> $results Results.
	 * @return void
	 */
	public static function save( array $results ): void {
		update_option( self::OPTION, $results, false ); // Adds it (not autoloaded) when missing.
	}

	/**
	 * One check's entry, or null.
	 *
	 * @since 1.0.0
	 * @param string $id Check ID.
	 * @return array<string, mixed>|null
	 */
	public static function for_check( string $id ): ?array {
		return self::get()['checks'][ $id ] ?? null;
	}

	/**
	 * Why a check's result can't be cleaned on ('' when it can): never scanned, still scanning,
	 * older than a day, threshold or availability changed since, or cleaned since.
	 *
	 * @since 1.0.0
	 * @param Check                     $check Check.
	 * @param array<string, mixed>|null $entry Entry.
	 * @return string
	 */
	public static function stale_reason( Check $check, ?array $entry ): string {
		if ( ! $entry || ! $entry['done'] || ! $entry['scanned_at'] ) {
			return __( 'Scan first.', 'admin-powerups-for-woocommerce' );
		}
		if ( $entry['recheck'] ) {
			return __( 'Scan again to see what’s left.', 'admin-powerups-for-woocommerce' );
		}
		if ( $entry['scanned_at'] < time() - self::FRESH ) {
			return __( 'The count is more than a day old. Scan again.', 'admin-powerups-for-woocommerce' );
		}
		if ( $entry['threshold'] !== $check->threshold() ) {
			return __( 'The age setting changed since the scan. Scan again.', 'admin-powerups-for-woocommerce' );
		}
		if ( $entry['unavailable'] !== $check->unavailable() ) {
			return __( 'Something changed since the scan. Scan again.', 'admin-powerups-for-woocommerce' );
		}
		return '';
	}

	/**
	 * Update one entry and save.
	 *
	 * @since 1.0.0
	 * @param string               $id      Check ID.
	 * @param array<string, mixed> $changes Keys to set.
	 * @return void
	 */
	public static function update_check( string $id, array $changes ): void {
		$results = self::get();
		if ( ! isset( $results['checks'][ $id ] ) ) {
			return;
		}
		$results['checks'][ $id ] = array_merge( $results['checks'][ $id ], $changes );
		self::save( $results );
	}
}