import type { Context } from "./deps.node.js";
/** Current data version of this plugin */
export declare const PLUGIN_DATA_VERSION = 0;
/**
 * A value with a version.
 *
 * The version consists of two pieces.
 *
 * The first piece is a number that is defined by the plugin internally and
 * cannot be changed. When the plugin is updated and it changes its internal
 * data format, then it can use this part of the version to detect and
 * automatically migrate the versioned state as necessary.
 *
 * The second piece is a number or a string and can be set by the developer. It
 * should be changed whenever the application code changes in a way that
 * invalidates the state. The plugin can then discard and re-create the state as
 * necesarry.
 *
 * Versioned states are typically created via the {@link pinVersion} function.
 *
 * @typeParam S The type of the state to be versioned
 */
export interface VersionedState<S> {
    /** The version of the state */
    version: [typeof PLUGIN_DATA_VERSION, string | number];
    /** The state to be versioned */
    state: S;
}
/**
 * A container for two functions that are pinned to a specific version. The two
 * functions can be used to add the bound version to data, and to unpack the
 * data again. This container is typically created using {@link pinVersion}.
 */
export interface PinnedVersion {
    /**
     * Adds a version to some data.
     *
     * @param state Some data
     */
    versionify<S>(state: S): VersionedState<S>;
    /**
     * Unpacks some versioned data. Returns the original data if the data is
     * correct, and `undefined` otherwise. If `undefined` is passed, then
     * `undefined` will be returned.
     *
     * @param data Some versioned data or `undefined`
     */
    unpack<S>(data?: VersionedState<S>): S | undefined;
}
/**
 * Takes a version number and state management functions that are pinned to this
 * version.
 *
 * The two functions it returns are `versionify` and `unpack`. The former can be
 * used to add a version to some data. The latter can be used to unpack the data
 * again, validating the version on the fly.
 *
 * ```ts
 * import { assert } from "jsr:@std/assert";
 *
 * const { versionify, unpack } = pinVersion(42);
 *
 * const data = { prop: "pizza" };
 * const versioned = versionify(data);
 * const unpacked = unpack(versioned);
 * assert(data === unpacked);
 * ```
 *
 * @param version the version to use for pinning
 */
export declare function pinVersion(version: string | number): PinnedVersion;
/**
 * A value or a promise of a value.
 *
 * @typeParam T The type of value
 */
export type MaybePromise<T> = T | Promise<T>;
/**
 * A storage for versioned state.
 *
 * Specify this to define how to persist data.
 *
 * This type is a union of three types, each representing a different way to
 * store data.
 *
 * 1. A {@link VersionedStateStorage} directly provides definitions for reading,
 *    writing, and deleting data based on `ctx.chatId`. No versions can be
 *    specified and the storage key function cannot be changed.
 * 2. A {@link ConversationKeyStorage}, disambiguated via `{ type: "key" }`, is
 *    more general. It supports versioning the data and changing the storage key
 *    function.
 * 3. A {@link ConversationContextStorage}, disambiguated via `{ type: "context"
 *    }`, is even more general. It no longer needs a storage key function.
 *    Instead, it provides read, write, and delete operations for data based on
 *    the context object directly. It also supports versioning data.
 *
 * @typeParam C A custom context type
 * @typeParam S A type for the state to version and store
 */
export type ConversationStorage<C extends Context, S> = {
    type?: never;
    version?: never;
} & VersionedStateStorage<string, S> | ConversationContextStorage<C, S> | ConversationKeyStorage<C, S>;
/**
 * An object that defines how to read, write, and delete versioned data based on
 * a key.
 *
 * @typeParam K The type of key to use
 * @typeParam S The type of data to store
 */
export interface VersionedStateStorage<K, S> {
    /**
     * Reads the data for a given key.
     *
     * @param key A key to identify the data
     */
    read(key: K): MaybePromise<VersionedState<S> | undefined>;
    /**
     * Writes some data to the storage for a given key.
     *
     * @param key A key to identify the data
     * @param state The data to write
     */
    write(key: K, state: VersionedState<S>): MaybePromise<void>;
    /**
     * Deletes some data from the storage for a given key.
     *
     * @param key A key to identify the data
     */
    delete(key: K): MaybePromise<void>;
}
/**
 * An object that defines how to read, write, or delete versioned data based on
 * a context object.
 */
export interface ConversationContextStorage<C extends Context, S> {
    /** The type of storage, always `"context"` */
    type: "context";
    /** An optional version for the data, defaults to `0` */
    version?: string | number;
    /** The underlying storage that defines how to read and write raw data */
    adapter: VersionedStateStorage<C, S>;
}
export interface ConversationKeyStorage<C extends Context, S> {
    /** The type of storage, always `"key"` */
    type: "key";
    /** An optional version for the data, defaults to `0` */
    version?: string | number;
    /** An optional prefix to prepend to the storage key */
    prefix?: string;
    /** An optional storage key function, defaults to `ctx.chatId` */
    getStorageKey?(ctx: C): string | undefined;
    /** The underlying storage that defines how to read and write raw data */
    adapter: VersionedStateStorage<string, S>;
}
/**
 * Coerces different storages to a single uniform abstraction.
 *
 * This function takes a {@link ConversationStorage} object and unifies its
 * union members behind a common abstraction that simply exposes a read, write,
 * and delete method for a given context object.
 *
 * @param storage An object defining how to store data
 */
export declare function uniformStorage<C extends Context, S>(storage?: ConversationStorage<C, S>): (ctx: C) => {
    read: () => MaybePromise<S | undefined>;
    write: (state: S) => MaybePromise<void>;
    delete: () => MaybePromise<void>;
};