<?php
/**
 * Plugin settings: defaults, reading, and sanitising.
 *
 * @package WPAttributionTracker
 */

declare( strict_types=1 );

namespace WPAttributionTracker;

defined( 'ABSPATH' ) || exit;

final class Settings {

	public const OPTION        = 'wpat_settings';
	public const SCHEMA        = 1;
	public const MIN_RETENTION = 1;
	public const MAX_RETENTION = 730;

	/**
	 * Most custom parameters a site can track. Every value travels in the
	 * visitor's cookie, so the list cannot grow without bound.
	 */
	public const PARAM_LIMIT = 100;

	/**
	 * Settings resolved once per request.
	 *
	 * @var array<string, mixed>|null
	 */
	private static ?array $cache = null;

	/**
	 * @return array<string, mixed>
	 */
	public static function defaults(): array {
		return array(
			'schema'         => self::SCHEMA,
			'cookie_name'    => 'wpat_attribution',
			'retention_days' => 90,
			'custom_params'  => array(),
			'public_debug'   => false,
			'server_backup'  => true,
		);
	}

	/**
	 * All settings, with anything missing or invalid replaced by its default.
	 *
	 * @return array<string, mixed>
	 */
	public static function all(): array {
		if ( null === self::$cache ) {
			$stored      = get_option( self::OPTION, array() );
			self::$cache = self::normalize( is_array( $stored ) ? $stored : array() );
		}

		return self::$cache;
	}

	/**
	 * A single setting value.
	 *
	 * @return mixed
	 */
	public static function get( string $key ) {
		return self::all()[ $key ] ?? null;
	}

	/**
	 * Persist settings and refresh the request cache.
	 *
	 * @param array<string, mixed> $values Raw values, typically straight from a form.
	 * @return array<string, mixed> The sanitised values that were stored.
	 */
	public static function save( array $values ): array {
		// Read before the write, so listeners can compare old and new.
		$previous = self::all();
		$clean    = self::sanitize( $values );

		update_option( self::OPTION, $clean );
		self::$cache = $clean;

		/**
		 * Fires after the plugin's settings have been stored.
		 *
		 * @param array<string, mixed> $settings The values that were stored.
		 * @param array<string, mixed> $previous The values they replaced.
		 */
		do_action( 'wpat_settings_saved', $clean, $previous );

		return $clean;
	}

	/**
	 * Force the next read to hit the database again.
	 */
	public static function flush_cache(): void {
		self::$cache = null;
	}

	/**
	 * Normalise a stored settings array.
	 *
	 * @param array<string, mixed> $values Stored values.
	 * @return array<string, mixed>
	 */
	public static function normalize( array $values ): array {
		$merged = $values + self::defaults();

		return array(
			'schema'         => self::SCHEMA,
			'cookie_name'    => self::clean_cookie_name( (string) $merged['cookie_name'] ),
			'retention_days' => self::clamp_retention( $merged['retention_days'] ),
			'custom_params'  => self::sanitize_custom_params( $merged['custom_params'] ),
			'public_debug'   => (bool) $merged['public_debug'],
			'server_backup'  => (bool) $merged['server_backup'],
		);
	}

	/**
	 * Normalise a settings form submission.
	 *
	 * @param array<string, mixed> $values Raw form values.
	 * @return array<string, mixed>
	 */
	public static function sanitize( array $values ): array {
		return self::normalize(
			array(
				'cookie_name'    => $values['cookie_name'] ?? '',
				'retention_days' => $values['retention_days'] ?? self::defaults()['retention_days'],
				'custom_params'  => $values['custom_params'] ?? array(),
				'public_debug'   => ! empty( $values['public_debug'] ),
				'server_backup'  => ! empty( $values['server_backup'] ),
			)
		);
	}

	/**
	 * Keep only the characters a cookie name may contain, falling back to the
	 * default when nothing usable is left.
	 */
	private static function clean_cookie_name( string $name ): string {
		$clean = (string) preg_replace( '/[^A-Za-z0-9_-]/', '', $name );

		return '' !== $clean ? $clean : self::defaults()['cookie_name'];
	}

	/**
	 * Hold retention inside the supported range.
	 *
	 * @param mixed $days Raw value.
	 */
	private static function clamp_retention( $days ): int {
		return min( self::MAX_RETENTION, max( self::MIN_RETENTION, (int) $days ) );
	}

	/**
	 * Normalise the custom parameter list.
	 *
	 * @param mixed $raw Array of names or a newline separated string.
	 * @return string[]
	 */
	private static function sanitize_custom_params( $raw ): array {
		$names = is_string( $raw ) ? preg_split( '/[\r\n,]+/', $raw ) : (array) $raw;
		$clean = array();

		foreach ( (array) $names as $name ) {
			$name = strtolower( trim( (string) $name ) );
			$name = (string) preg_replace( '/[^a-z0-9_-]/', '', $name );

			if ( '' === $name || strlen( $name ) > 40 ) {
				continue;
			}

			if ( in_array( $name, Fields::RESERVED_KEYS, true ) ) {
				continue;
			}

			if ( isset( Fields::utm_params()[ $name ] ) ) {
				continue;
			}

			$clean[ $name ] = $name;
		}

		return array_slice( array_values( $clean ), 0, self::PARAM_LIMIT );
	}
}