<?php
/**
 * Proof snapshots: what exactly a visitor was shown when they chose.
 *
 * @package AriConsent
 */

namespace AriConsent;

defined( 'ABSPATH' ) || exit;

/**
 * Stores each distinct version of the banner (texts, categories, services, policy link) once,
 * keyed by its SHA-256 hash. Every consent record points to the hash it was given under, so the
 * site owner can show what a visitor agreed to on a given day (GDPR Art. 7(1)).
 */
final class Snapshots {

	const KNOWN_OPT = 'ariconsent_snapshot_hashes';

	/**
	 * Table name.
	 *
	 * @return string
	 */
	public static function table() {
		global $wpdb;
		return $wpdb->prefix . 'ariconsent_snapshots';
	}

	/**
	 * What the visitor sees right now, in the current language.
	 *
	 * @return array<string, mixed>
	 */
	public static function content() {
		$settings   = Settings::get();
		$categories = array();
		foreach ( Services::categories() as $slug => $category ) {
			$categories[ $slug ] = array(
				'label'       => $category['label'],
				'description' => $category['description'],
				'required'    => ! empty( $category['required'] ),
			);
		}
		$services = array();
		foreach ( Services::listed() as $id => $service ) {
			$services[ $id ] = array(
				'name'     => $service['name'],
				'provider' => $service['provider'],
				'category' => $service['category'],
			);
		}
		ksort( $services );
		$policy = Multilingual::privacy_url( $settings );

		return array(
			'locale'     => determine_locale(),
			'revision'   => (int) $settings['revision'],
			'texts'      => Settings::texts(),
			'categories' => $categories,
			'services'   => $services,
			'policy_url' => $policy ? (string) $policy : '',
		);
	}

	/**
	 * Hash of the current banner, stored if it is new.
	 *
	 * @return string 64-character hex hash.
	 */
	public static function current() {
		$content = self::content();
		$hash    = hash( 'sha256', (string) wp_json_encode( $content ) );
		self::store( $hash, $content );
		return $hash;
	}

	/**
	 * Stores a snapshot once. Known hashes are cached in an option so normal page views do no writes.
	 *
	 * @param string               $hash    Hash.
	 * @param array<string, mixed> $content Content.
	 */
	public static function store( $hash, array $content ) {
		$known = (array) get_option( self::KNOWN_OPT, array() );
		if ( in_array( $hash, $known, true ) ) {
			return;
		}
		global $wpdb;
		$table = self::table();
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table; INSERT IGNORE keeps one row per hash.
		$wpdb->query( $wpdb->prepare( 'INSERT IGNORE INTO %i (hash, created_at, content) VALUES (%s, %s, %s)', $table, $hash, current_time( 'mysql', true ), wp_json_encode( $content ) ) );
		if ( self::exists( $hash ) ) {
			$known[] = $hash;
			update_option( self::KNOWN_OPT, array_slice( array_values( array_unique( $known ) ), -200 ), false );
		}
	}

	/**
	 * Whether a snapshot exists.
	 *
	 * @param string $hash Hash.
	 * @return bool
	 */
	public static function exists( $hash ) {
		return null !== self::get( $hash );
	}

	/**
	 * Loads a snapshot.
	 *
	 * @param string $hash Hash.
	 * @return array{hash: string, created_at: string, content: array<string, mixed>}|null
	 */
	public static function get( $hash ) {
		if ( ! is_string( $hash ) || ! preg_match( '/^[a-f0-9]{64}$/', $hash ) ) {
			return null;
		}
		global $wpdb;
		$table = self::table();
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Custom table.
		$row = $wpdb->get_row( $wpdb->prepare( 'SELECT hash, created_at, content FROM %i WHERE hash = %s', $table, $hash ), ARRAY_A );
		if ( ! $row ) {
			return null;
		}
		$content = json_decode( (string) $row['content'], true );
		return array(
			'hash'       => (string) $row['hash'],
			'created_at' => (string) $row['created_at'],
			'content'    => is_array( $content ) ? $content : array(),
		);
	}
}