<?php
/**
 * Immutable engine settings snapshot.
 *
 * @package ZeroSpamForms
 */

namespace TwoOTwoCode\ZeroSpamForms\Engine;

defined( 'ABSPATH' ) || exit;

/**
 * Provides sanitized settings for engine evaluation.
 */
final class SettingsSnapshot {
	public const MODE_PROTECT  = 'protect';
	public const MODE_MONITOR  = 'monitor';
	public const MODE_DISABLED = 'disabled';

	public const STRICTNESS_SAFE     = 'safe';
	public const STRICTNESS_BALANCED = 'balanced';
	public const STRICTNESS_STRICT   = 'strict';

	public const MODE_RELAXED  = self::STRICTNESS_SAFE;
	public const MODE_BALANCED = self::STRICTNESS_BALANCED;
	public const MODE_STRICT   = self::STRICTNESS_STRICT;

	/**
	 * Sanitized settings.
	 *
	 * @var array<string, bool|float|int|string>
	 */
	private $settings;

	/**
	 * Constructor.
	 *
	 * @param array<string, mixed> $settings Raw settings.
	 */
	private function __construct( array $settings ) {
		$this->settings = $this->sanitize( $settings );
	}

	/**
	 * Create from a settings array.
	 *
	 * @param array<string, mixed> $settings Raw settings.
	 */
	public static function from_array( array $settings ): self {
		return new self( $settings );
	}

	/**
	 * Get default engine settings.
	 *
	 * @return array<string, bool|float|int|string>
	 */
	public static function defaults(): array {
		return array(
			'protection_mode'                => self::MODE_PROTECT,
			'strictness'                     => self::STRICTNESS_BALANCED,
			'minimum_fill_time_seconds'      => 3,
			'token_lifetime_seconds'         => 1800,
			'rate_limit_window_seconds'      => 300,
			'rate_limit_threshold'           => 5,
			'link_density_threshold'         => 0.5,
			'honeypot_check_enabled'         => true,
			'minimum_time_check_enabled'     => true,
			'javascript_token_check_enabled' => true,
			'rate_limit_check_enabled'       => true,
			'link_density_check_enabled'     => true,
		);
	}

	/**
	 * Get protection mode.
	 */
	public function get_protection_mode(): string {
		return (string) $this->settings['protection_mode'];
	}

	/**
	 * Get strictness.
	 */
	public function get_strictness(): string {
		return (string) $this->settings['strictness'];
	}

	/**
	 * Get minimum fill time.
	 */
	public function get_minimum_fill_time_seconds(): int {
		return (int) $this->settings['minimum_fill_time_seconds'];
	}

	/**
	 * Get token lifetime.
	 */
	public function get_token_lifetime_seconds(): int {
		return (int) $this->settings['token_lifetime_seconds'];
	}

	/**
	 * Get rate-limit window.
	 */
	public function get_rate_limit_window_seconds(): int {
		return (int) $this->settings['rate_limit_window_seconds'];
	}

	/**
	 * Get rate-limit threshold.
	 */
	public function get_rate_limit_threshold(): int {
		return (int) $this->settings['rate_limit_threshold'];
	}

	/**
	 * Get link-density threshold.
	 */
	public function get_link_density_threshold(): float {
		return (float) $this->settings['link_density_threshold'];
	}

	/**
	 * Check whether a named check is enabled.
	 *
	 * @param string $key Setting key.
	 */
	public function is_check_enabled( string $key ): bool {
		return ! empty( $this->settings[ $key ] );
	}

	/**
	 * Get settings as an array.
	 *
	 * @return array<string, bool|float|int|string>
	 */
	public function to_array(): array {
		return $this->settings;
	}

	/**
	 * Sanitize engine settings.
	 *
	 * @param array<string, mixed> $settings Raw settings.
	 *
	 * @return array<string, bool|float|int|string>
	 */
	private function sanitize( array $settings ): array {
		$defaults  = self::defaults();
		$sanitized = $defaults;

		if ( isset( $settings['protection_mode'] ) && is_scalar( $settings['protection_mode'] ) ) {
			$mode = strtolower( (string) $settings['protection_mode'] );

			if ( in_array( $mode, array( self::MODE_PROTECT, self::MODE_MONITOR, self::MODE_DISABLED ), true ) ) {
				$sanitized['protection_mode'] = $mode;
			}
		}

		if ( isset( $settings['strictness'] ) && is_scalar( $settings['strictness'] ) ) {
			$strictness = strtolower( (string) $settings['strictness'] );

			if ( in_array( $strictness, array( self::STRICTNESS_SAFE, self::STRICTNESS_BALANCED, self::STRICTNESS_STRICT ), true ) ) {
				$sanitized['strictness'] = $strictness;
			}
		}

		$sanitized['minimum_fill_time_seconds'] = $this->bounded_int( $settings, 'minimum_fill_time_seconds', 1, 60, (int) $defaults['minimum_fill_time_seconds'] );
		$sanitized['token_lifetime_seconds']    = $this->bounded_int( $settings, 'token_lifetime_seconds', 60, 86400, (int) $defaults['token_lifetime_seconds'] );
		$sanitized['rate_limit_window_seconds'] = $this->bounded_int( $settings, 'rate_limit_window_seconds', 60, 86400, (int) $defaults['rate_limit_window_seconds'] );
		$sanitized['rate_limit_threshold']      = $this->bounded_int( $settings, 'rate_limit_threshold', 1, 1000, (int) $defaults['rate_limit_threshold'] );
		$sanitized['link_density_threshold']    = $this->bounded_float( $settings, 'link_density_threshold', 0.05, 1.0, (float) $defaults['link_density_threshold'] );

		foreach ( array( 'honeypot_check_enabled', 'minimum_time_check_enabled', 'javascript_token_check_enabled', 'rate_limit_check_enabled', 'link_density_check_enabled' ) as $enabled_key ) {
			if ( array_key_exists( $enabled_key, $settings ) ) {
				$sanitized[ $enabled_key ] = $this->to_bool( $settings[ $enabled_key ] );
			}
		}

		return $sanitized;
	}

	/**
	 * Get a bounded integer from settings.
	 *
	 * @param array<string, mixed> $settings Raw settings.
	 * @param string               $key      Setting key.
	 * @param int                  $min      Minimum value.
	 * @param int                  $max      Maximum value.
	 * @param int                  $default_value Default value.
	 */
	private function bounded_int( array $settings, string $key, int $min, int $max, int $default_value ): int {
		if ( ! isset( $settings[ $key ] ) || ! is_scalar( $settings[ $key ] ) ) {
			return $default_value;
		}

		$value = (int) $settings[ $key ];

		if ( $value < $min ) {
			return $min;
		}

		if ( $value > $max ) {
			return $max;
		}

		return $value;
	}

	/**
	 * Get a bounded float from settings.
	 *
	 * @param array<string, mixed> $settings Raw settings.
	 * @param string               $key      Setting key.
	 * @param float                $min      Minimum value.
	 * @param float                $max      Maximum value.
	 * @param float                $default_value Default value.
	 */
	private function bounded_float( array $settings, string $key, float $min, float $max, float $default_value ): float {
		if ( ! isset( $settings[ $key ] ) || ! is_scalar( $settings[ $key ] ) ) {
			return $default_value;
		}

		$value = (float) $settings[ $key ];

		if ( $value < $min ) {
			return $min;
		}

		if ( $value > $max ) {
			return $max;
		}

		return $value;
	}

	/**
	 * Convert a value to a boolean.
	 *
	 * @param mixed $value Raw value.
	 */
	private function to_bool( $value ): bool {
		if ( is_bool( $value ) ) {
			return $value;
		}

		if ( ! is_scalar( $value ) ) {
			return false;
		}

		return in_array( strtolower( (string) $value ), array( '1', 'true', 'yes', 'on' ), true );
	}
}