import { Directive } from '@alwatr/directive';
import { type BindingValue } from './main.js';
/**
 * A declarative DOM directive that binds DOM element attributes to view model properties.
 *
 * Syntax: `bind_attrib="attributeName=[!]namespace.propertyName; anotherAttribute=[!]namespace.anotherProperty"`
 *
 * Supports binding multiple attributes on the same element separated by semicolons (`;`).
 *
 * Behavior:
 * - `boolean` value: Toggles the presence of the attribute (idiomatic for boolean attributes like `disabled`, `hidden`, `readonly`, `checked`).
 * - `null` / `undefined` value: Removes the attribute from the element.
 * - Negation (`!`): Prefixing the property with `!` (e.g., `!namespace.prop`) will negate the value (coerced as boolean).
 * - Any other type: Coerced via `String(value)` and set as the attribute's value.
 *
 * Includes a redundant write guard (via `lastValues_`) that skips calls to the DOM if the property value hasn't changed.
 * Supports deferred viewport initialization if the `lazy_bind` attribute is present on the element.
 *
 * @example
 * ```html
 * <!-- Binds presence of 'disabled' to cart emptiness and 'aria-busy' to loading state -->
 * <button bind_attrib="disabled=user.cartIsEmpty; aria-busy=ui.loading">Checkout</button>
 *
 * <!-- Binds 'hidden' to the negation of isPlaying -->
 * <div bind_attrib="hidden=!player.isPlaying">Player is paused</div>
 *
 * <!-- Binds 'src' and 'alt' attributes -->
 * <img bind_attrib="src=user.avatarUrl; alt=user.fullName" />
 *
 * <!-- Lazy attribute binding -->
 * <iframe bind_attrib="src=video.embedUrl" lazy_bind></iframe>
 * ```
 */
export declare class BindAttribDirective extends Directive {
    /**
     * Attribute flag used to defer binding initialization until the element enters the viewport.
     * If `lazy_bind` attribute exists, this is non-null.
     */
    protected accessor lazyBinding_: null | string;
    /**
     * Initializes the directive.
     * Checks if lazy binding is enabled via `lazy_bind`.
     * If yes, delegates the initialization to `lazyInit_`; otherwise, initializes immediately.
     */
    protected init_(): void;
    /**
     * Cache of the last applied values to guard against redundant DOM modifications.
     */
    protected lastValues_: Record<string, BindingValue>;
    /**
     * Main binding initialization logic. Parses each attribute-binding pair,
     * retrieves the corresponding ViewModel signals, subscribes to updates,
     * and applies the initial attribute state.
     */
    protected bindingInit_(): void;
    /**
     * Applies the bound value to a specific DOM attribute on the element.
     *
     * @param attributeName The name of the target attribute (e.g., `'src'`, `'disabled'`).
     * @param value The value to apply.
     */
    protected applyAttribute_(attributeName: string, value: BindingValue): void;
}
/**
 * Helper to register `BindAttribDirective` lazily under the `bind_attrib` attribute.
 */
export declare const registerBindAttribDirective: import("@alwatr/directive").RegisterDirectiveFunction;
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