import type { RequiredKeys } from 'utilium';
import type { FileSystem } from '../filesystem.js';
type OptionType = 'string' | 'number' | 'bigint' | 'boolean' | 'symbol' | 'undefined' | 'object' | 'function';
/**
 * Resolves the type of Backend.options from the options interface
 */
export type OptionsConfig<T> = {
    [K in keyof T]: {
        /**
         * The basic JavaScript type(s) for this option.
         */
        type: OptionType | readonly OptionType[];
        /**
         * Description of the option. Used in error messages and documentation.
         */
        description: string;
        /**
         * Whether or not the option is required (optional can be set to null or undefined). Defaults to false.
         */
        required: K extends RequiredKeys<T> ? true : false;
        /**
         * A custom validation function to check if the option is valid.
         * When async, resolves if valid and rejects if not.
         * When sync, it will throw an error if not valid.
         */
        validator?(opt: T[K]): void | Promise<void>;
    };
};
/**
 * Configuration options shared by backends and `Configuration`
 */
export interface SharedConfig {
    /**
     * If set, disables the sync cache and sync operations on async file systems.
     */
    disableAsyncCache?: boolean;
}
/**
 * A backend
 */
export interface Backend<FS extends FileSystem = FileSystem, TOptions extends object = object> {
    /**
     * Create a new instance of the backend
     */
    create(options: TOptions & Partial<SharedConfig>): FS | Promise<FS>;
    /**
     * A name to identify the backend.
     */
    name: string;
    /**
     * Describes all of the options available for this backend.
     */
    options: OptionsConfig<TOptions>;
    /**
     * Whether the backend is available in the current environment.
     * It supports checking synchronously and asynchronously
     *
     * Returns 'true' if this backend is available in the current
     * environment. For example, a backend using a browser API will return
     * 'false' if the API is unavailable
     *
     */
    isAvailable(): boolean | Promise<boolean>;
}
/**
 * Gets the options type of a backend
 * @internal
 */
export type OptionsOf<T extends Backend> = T extends Backend<FileSystem, infer TOptions> ? TOptions : never;
/**
 * Gets the FileSystem type for a backend
 * @internal
 */
export type FilesystemOf<T extends Backend> = T extends Backend<infer FS> ? FS : never;
/** @internal */
export declare function isBackend(arg: unknown): arg is Backend;
/**
 * Checks that `options` object is valid for the file system options.
 * @internal
 */
export declare function checkOptions<T extends Backend>(backend: T, options: Record<string, unknown>): Promise<void>;
/**
 * Specifies a file system backend type and its options.
 *
 * Individual options can recursively contain BackendConfiguration objects for values that require file systems.
 *
 * The configuration for each file system corresponds to that file system's option object passed to its `create()` method.
 */
export type BackendConfiguration<T extends Backend> = OptionsOf<T> & Partial<SharedConfig> & {
    backend: T;
};
/** @internal */
export declare function isBackendConfig<T extends Backend>(arg: unknown): arg is BackendConfiguration<T>;
export {};