this->get_selector_vars_css( $selector, $vars, $form_id ) // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
		);
	}

	/**
	 * Output CSS vars for the form added as a shortcode.
	 *
	 * @since 1.9.7
	 *
	 * @param array $atts Shortcode attributes.
	 */
	public function output_css_vars_for_shortcode( array $atts ): void {

		if ( empty( $atts['id'] ) ) {
			return;
		}

		$form_handler = wpforms()->obj( 'form' );

		if ( ! $form_handler ) {
			return;
		}

		$form_id   = (int) $atts['id'];
		$form_data = $form_handler->get( $form_id, [ 'content_only' => true ] );

		if ( empty( $form_data ) ) {
			return;
		}

		$attr = isset( $form_data['settings']['themes'] ) ? (array) $form_data['settings']['themes'] : [];
		$attr = $this->maybe_override_attributes( $attr );

		$css_vars = $this->get_customized_css_vars( $attr );
		$css_vars = $this->add_css_vars_units( $css_vars );

		$selector = "#wpforms-{$form_id}";
		$style_id = "wpforms-css-vars-{$form_id}";

		$this->output_selector_vars( $selector, $css_vars, $style_id, $form_id );
		$this->output_custom_css( $attr, $selector, $style_id );
	}

	/**
	 * Output custom CSS.
	 *
	 * @since 1.9.7
	 *
	 * @param array  $attr     Attributes.
	 * @param string $selector Selector.
	 * @param string $style_id Style ID.
	 *
	 * @noinspection PhpMissingParamTypeInspection
	 */
	private function output_custom_css( array $attr, string $selector, string $style_id ): void {

		if ( wpforms_get_render_engine() === 'classic' ) {
			return;
		}

		$custom_css = trim( $attr['customCss'] ?? '' );

		if ( empty( $custom_css ) ) {
			return;
		}

		printf(
			'<style id="%1$s-custom-css">
				%2$s {
					%3$s
				}
			</style>',
			sanitize_key( $style_id ),
			$selector, // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
			wp_strip_all_tags( $custom_css ) // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
		);
	}

	/**
	 * Maybe override attributes with themes.json settings.
	 *
	 * @since 1.9.7
	 *
	 * @param array $attr Attributes.
	 *
	 * @return array
	 */
	private function maybe_override_attributes( array $attr ): array {

		$theme_slug = (string) ( $attr['wpformsTheme'] ?? '' );

		if ( empty( $theme_slug ) ) {
			return $attr;
		}

		$attr = $this->normalize_background_url( $attr );

		$theme_data = $this->get_themes_data_object()->get_theme( $theme_slug );
		$settings   = $theme_data['settings'] ?? [];

		return array_merge( $attr, $settings );
	}

	/**
	 * Normalize background URL.
	 *
	 * Check if the background URL is not wrapped in url() and add it if needed.
	 *
	 * @since 1.9.7
	 *
	 * @param array $attr Attributes.
	 */
	private function normalize_background_url( array $attr ): array {

		if ( ! isset( $attr['backgroundUrl'] ) ) {
			return $attr;
		}

		if ( strpos( $attr['backgroundUrl'], 'url(' ) === 0 ) {
			return $attr;
		}

		$attr['backgroundUrl'] = 'url(' . $attr['backgroundUrl'] . ')';

		return $attr;
	}

	/**
	 * Get themes data object.
	 *
	 * @since 1.9.7
	 *
	 * @return ThemesData
	 */
	private function get_themes_data_object(): ThemesData {

		if ( wpforms()->is_pro() ) {
			return new ProThemesData( new StockPhotos() );
		}

		return new LiteThemesData();
	}

	/**
	 * Add CSS vars units.
	 *
	 * Form builder saves values without pixels, we need to add them before outputting as CSS vars.
	 *
	 * @since 1.9.7
	 *
	 * @param array $css_vars CSS vars.
	 *
	 * @return array
	 */
	private function add_css_vars_units( array $css_vars ): array {

		$has_pixels = [
			'field-border-size',
			'field-border-radius',
			'button-border-size',
			'button-border-radius',
			'container-padding',
			'container-border-width',
			'container-border-radius',
		];

		foreach ( $has_pixels as $key ) {
			if ( isset( $css_vars[ $key ] ) && is_numeric( $css_vars[ $key ] ) && $css_vars[ $key ] > 0 ) {
				$css_vars[ $key ] .= 'px';
			}
		}

		return $css_vars;
	}

	/**
	 * Get selector variables CSS.
	 *
	 * @since 1.9.3
	 *
	 * @param string     $selector Selector.
	 * @param array      $vars     Variables data.
	 * @param string|int $form_id  Form ID. Optional. Default is an empty string.
	 *
	 * @return string
	 */
	private function get_selector_vars_css( string $selector, array $vars, $form_id = '' ): string {

		return sprintf(
			'%1$s {
				%2$s
			}',
			$selector, // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
			wp_strip_all_tags( $this->get_vars_css( $vars, $form_id ) )
		);
	}

	/**
	 * Pre print vars filter.
	 *
	 * @since 1.8.8
	 *
	 * @param array      $vars    Variables data.
	 * @param string|int $form_id Form ID. Optional. Default is an empty string.
	 *
	 * @return array
	 */
	private function get_pre_print_vars( array $vars, $form_id = '' ): array {

		// Normalize the `background-url` variable.
		if ( isset( $vars['background-url'] ) ) {
			$vars['background-url'] = $vars['background-url'] === 'url()' ? 'none' : $vars['background-url'];
		}

		/**
		 * Filter CSS variables right before printing the CSS.
		 *
		 * @since 1.8.8
		 *
		 * @param array $vars    CSS variables.
		 * @param int   $form_id Form ID. Optional. Default is an empty string.
		 */
		return (array) apply_filters( 'wpforms_frontend_css_vars_pre_print_filter', $vars, $form_id );
	}

	/**
	 * Generate CSS code from given vars data.
	 *
	 * @since 1.8.1
	 *
	 * @param array      $vars    Variables data.
	 * @param string|int $form_id Form ID. Optional. Default is an empty string.
	 */
	private function get_vars_css( array $vars, $form_id = '' ): string {

		$vars   = $this->get_pre_print_vars( $vars, $form_id );
		$result = '';

		foreach ( $vars as $name => $value ) {
			if ( ! is_string( $value ) ) {
				continue;
			}

			if ( $value === '0' ) {
				$value = '0px';
			}

			$result .= "--wpforms-{$name}: {$value};\n";

			if ( in_array( $name, self::SPARE_VARS, true ) ) {
				$result .= "--wpforms-{$name}-spare: {$value};\n";
			}
		}

		return $result;
	}

	/**
	 * Get customized CSS vars.
	 *
	 * @since 1.8.3
	 *
	 * @param array $attr Attributes passed by integration.
	 *
	 * @return array
	 */
	public function get_customized_css_vars( array $attr ): array { // phpcs:ignore Generic.Metrics.CyclomaticComplexity.TooHigh

		$root_css_vars = $this->get_vars();
		$css_vars      = [];

		foreach ( $attr as $key => $value ) {

			$var_name = strtolower( preg_replace( '/[A-Z]/', '-$0', $key ) );

			// Skip an attribute that is not the CSS var or has the default value.
			if ( empty( $root_css_vars[ $var_name ] ) || $root_css_vars[ $var_name ] === $value ) {
				continue;
			}

			$css_vars[ $var_name ] = $value;
		}

		// Reset border size in case of border style is `none`.
		$css_vars = $this->maybe_reset_border( $css_vars, 'field-border' );
		$css_vars = $this->maybe_reset_border( $css_vars, 'button-border' );

		// Set the button alternative background color and use border color for accent in case of transparent color.
		$button_bg_color = $css_vars['button-background-color'] ?? $root_css_vars['button-background-color'];

		if ( $this->is_transparent_color( $button_bg_color ) ) {
			$css_vars['button-background-color-alt'] = $button_bg_color;

			$border_color = $css_vars['button-border-color'] ?? $root_css_vars['button-border-color'];

			$css_vars['button-background-color'] = $this->is_transparent_color( $border_color ) ? $root_css_vars['button-background-color'] : $border_color;
			$button_bg_color                     = $css_vars['button-background-color'];
		}

		$button_bg_color = strtolower( $button_bg_color );

		// Set the button alternative text color in case if the background and text color are identical.
		$button_text_color = strtolower( $css_vars['button-text-color'] ?? $root_css_vars['button-text-color'] );

		if ( $button_bg_color === $button_text_color || $this->is_transparent_color( $button_text_color ) ) {
			$css_vars['button-text-color-alt'] = $this->get_contrast_color( $button_bg_color );
		}

		$size_css_vars = $this->get_size_css_vars( $attr );

		return array_merge( $css_vars, $size_css_vars );
	}

	/**
	 * Reset border size in case of border style is `none`.
	 *
	 * @since 1.9.7
	 *
	 * @param array  $css_vars CSS vars.
	 * @param string $key      Key.
	 *
	 * @return array
	 */
	private function maybe_reset_border( array $css_vars, string $key ): array {

		$style_key = $key . '-style';
		$size_key  = $key . '-size';

		if ( isset( $css_vars[ $style_key ] ) && $css_vars[ $style_key ] === 'none' ) {
			$css_vars[ $size_key ] = '0px';
		}

		return $css_vars;
	}

	/**
	 * Checks if the provided color has transparency.
	 *
	 * @since 1.8.8
	 *
	 * @param string $color The color to check.
	 *
	 * @return bool
	 */
	private function is_transparent_color( string $color ): bool {

		$rgba = $this->get_color_as_rgb_array( $color );

		$opacity_threshold = 0.33;
		$opacity           = $rgba[3] ?? 1;

		return $opacity < $opacity_threshold;
	}

	/**
	 * Get contrast color relative to a given color.
	 *
	 * @since 1.8.8
	 *
	 * @param string|array $color The color.
	 *
	 * @return string
	 */
	private function get_contrast_color( $color ): string {

		$rgba = is_array( $color ) ? $color : $this->get_color_as_rgb_array( $color );
		$avg  = (int) ( ( ( array_sum( $rgba ) ) / 3 ) * ( $rgba[3] ?? 1 ) );

		return $avg < 128 ? '#ffffff' : '#000000';
	}

	/**
	 * Get size CSS vars.
	 *
	 * @since 1.8.3
	 * @since 1.8.8 Removed $css_vars argument.
	 *
	 * @param array $attr Attributes passed by integration.
	 *
	 * @return array
	 */
	private function get_size_css_vars( array $attr ): array {

		$size_items    = [ 'field', 'label', 'button', 'container-shadow' ];
		$size_css_vars = [];

		foreach ( $size_items as $item ) {

			$item_attr = preg_replace_callback(
				'/-(\w)/',
				static function ( $matches ) {

					return strtoupper( $matches[1] );
				},
				$item
			);

			$item_attr .= 'Size';

			$item_key      = $item . '-size';
			$item_constant = 'self::' . str_replace( '-', '_', strtoupper( $item ) ) . '_SIZE';

			if ( empty( $attr[ $item_attr ] ) ) {
				continue;
			}

			$size_css_vars[] = $this->get_complex_vars( $item_key, constant( $item_constant )[ $attr[ $item_attr ] ] );
		}

		return empty( $size_css_vars ) ? [] : array_merge( ...$size_css_vars );
	}

	/**
	 * Get color as an array of RGB(A) values.
	 *
	 * @since 1.8.8
	 *
	 * @param string $color Color.
	 *
	 * @return array|bool Color as an array of RGBA values. False on error.
	 */
	private function get_color_as_rgb_array( string $color ) {

		// Remove # from the beginning of the string and remove whitespaces.
		$color = preg_replace( '/^#/', '', strtolower( trim( $color ) ) );
		$color = str_replace( ' ', '', (string) $color );

		if ( $color === 'transparent' ) {
			$color = 'rgba(0,0,0,0)';
		}

		$rgba      = $color;
		$rgb_array = [];

		// Check if color is in HEX(A) format.
		$is_hex = preg_match( '/[0-9a-f]{6,8}$/', $rgba );

		if ( $is_hex ) {
			// Search and split HEX(A) color into an array of char couples.
			preg_match_all( '/\w\w/', $rgba, $rgb_array );

			$rgb_array    = array_map(
				static function ( $value ) {

					return hexdec( '0x' . $value );
				},
				$rgb_array[0] ?? []
			);
			$rgb_array[3] = ( $rgb_array[3] ?? 255 ) / 255;
		} else {
			$rgba      = preg_replace( '/[^\d,.]/', '', $rgba );
			$rgb_array = explode( ',', $rgba );
		}

		return $rgb_array;
	}
}