<?php
/**
 * Plugin settings store.
 *
 * @package BlockSieve
 */

namespace BlockSieve\Settings;

/**
 * Owns every plugin setting, persisted as one autoloaded option array.
 *
 * All reads and writes go through this class, so the option key and the shape
 * of its value live in exactly one place. Stored values are always passed
 * through sanitize() on the way out as well as on the way in, so a hand-edited
 * or partially written option can never hand a caller an unexpected type.
 *
 * Only settings that were explicitly set are stored; every other setting is
 * read from defaults(), so a changed default reaches existing sites.
 *
 * sanitize(), merge() and defaults() perform no WordPress I/O and are
 * unit-tested; only all() and update() touch the options API.
 */
final class Settings {

	/**
	 * Option key holding the settings array (defined in the main plugin file).
	 */
	public const OPTION = BLOCKSIEVE_SETTINGS_OPTION;

	/**
	 * Setting: currently installed plugin version.
	 */
	public const VERSION = 'version';

	/**
	 * Setting: plugin version first installed on this site; never overwritten.
	 */
	public const INITIAL_VERSION = 'initial_version';

	/**
	 * Setting: report cache lifetime, in seconds.
	 */
	public const REPORT_TTL = 'report_ttl';

	/**
	 * Setting: maximum number of posts inspected in one scan.
	 */
	public const SCAN_LIMIT = 'scan_limit';

	/**
	 * Setting: post types inspected by the scan; empty means "detect".
	 */
	public const SCAN_POST_TYPES = 'scan_post_types';

	/**
	 * Default report cache lifetime: 15 minutes.
	 */
	public const DEFAULT_REPORT_TTL = 900;

	/**
	 * Shortest report cache lifetime accepted, in seconds.
	 */
	public const MIN_REPORT_TTL = 60;

	/**
	 * Default maximum number of posts inspected in one scan.
	 */
	public const DEFAULT_SCAN_LIMIT = 5000;

	/**
	 * Default value of every setting.
	 *
	 * @return array{version: string, initial_version: string, report_ttl: int, scan_limit: int, scan_post_types: string[]}
	 */
	public static function defaults(): array {
		return array(
			self::VERSION         => '',
			self::INITIAL_VERSION => '',
			self::REPORT_TTL      => self::DEFAULT_REPORT_TTL,
			self::SCAN_LIMIT      => self::DEFAULT_SCAN_LIMIT,
			self::SCAN_POST_TYPES => array(),
		);
	}

	/**
	 * Normalises a raw settings array.
	 *
	 * Missing or malformed values fall back to their defaults and unknown keys
	 * are dropped.
	 *
	 * @param array<string, mixed> $raw Raw settings.
	 * @return array{version: string, initial_version: string, report_ttl: int, scan_limit: int, scan_post_types: string[]}
	 */
	public static function sanitize( array $raw ): array {
		$settings = self::defaults();

		foreach ( array( self::VERSION, self::INITIAL_VERSION ) as $key ) {
			if ( is_string( $raw[ $key ] ?? null ) ) {
				$settings[ $key ] = trim( $raw[ $key ] );
			}
		}

		if ( is_numeric( $raw[ self::REPORT_TTL ] ?? null ) ) {
			$settings[ self::REPORT_TTL ] = max( self::MIN_REPORT_TTL, (int) $raw[ self::REPORT_TTL ] );
		}

		if ( is_numeric( $raw[ self::SCAN_LIMIT ] ?? null ) ) {
			$settings[ self::SCAN_LIMIT ] = max( 1, (int) $raw[ self::SCAN_LIMIT ] );
		}

		if ( is_array( $raw[ self::SCAN_POST_TYPES ] ?? null ) ) {
			$types = array();

			foreach ( $raw[ self::SCAN_POST_TYPES ] as $type ) {
				// Same character set as sanitize_key(), which post type slugs follow.
				$type = is_string( $type ) ? preg_replace( '/[^a-z0-9_\-]/', '', strtolower( $type ) ) : '';

				if ( is_string( $type ) && '' !== $type ) {
					$types[] = $type;
				}
			}

			$settings[ self::SCAN_POST_TYPES ] = array_values( array_unique( $types ) );
		}

		return $settings;
	}

	/**
	 * Merges changed settings into a stored array, keeping only explicit values.
	 *
	 * The result holds the sanitised value of every known key present in either
	 * input, and nothing for keys that were never set, so defaults are never
	 * written to the database.
	 *
	 * @param array<string, mixed> $stored Currently stored (raw) settings.
	 * @param array<string, mixed> $values Settings to change.
	 * @return array<string, mixed>
	 */
	public static function merge( array $stored, array $values ): array {
		$merged = array_merge( $stored, $values );

		return array_intersect_key( self::sanitize( $merged ), $merged );
	}

	/**
	 * Every setting, with defaults applied.
	 *
	 * @return array{version: string, initial_version: string, report_ttl: int, scan_limit: int, scan_post_types: string[]}
	 */
	public function all(): array {
		$stored = get_option( self::OPTION, array() );

		return self::sanitize( is_array( $stored ) ? $stored : array() );
	}

	/**
	 * Merges values into the stored settings.
	 *
	 * @param array<string, mixed> $values Settings to change, keyed by setting name.
	 * @return bool Whether the stored option changed.
	 */
	public function update( array $values ): bool {
		$stored = get_option( self::OPTION, array() );

		return update_option( self::OPTION, self::merge( is_array( $stored ) ? $stored : array(), $values ), true );
	}

	/**
	 * Installed plugin version ('' before the first activation).
	 *
	 * @return string
	 */
	public function version(): string {
		return $this->all()[ self::VERSION ];
	}

	/**
	 * Plugin version first installed on this site ('' before the first activation).
	 *
	 * @return string
	 */
	public function initial_version(): string {
		return $this->all()[ self::INITIAL_VERSION ];
	}

	/**
	 * Report cache lifetime, in seconds.
	 *
	 * @return int
	 */
	public function report_ttl(): int {
		return $this->all()[ self::REPORT_TTL ];
	}

	/**
	 * Maximum number of posts inspected in one scan.
	 *
	 * @return int
	 */
	public function scan_limit(): int {
		return $this->all()[ self::SCAN_LIMIT ];
	}

	/**
	 * Post types chosen for the scan; empty means "detect automatically".
	 *
	 * @return string[]
	 */
	public function scan_post_types(): array {
		return $this->all()[ self::SCAN_POST_TYPES ];
	}
}