import { Interface as ReadlineInterface } from "readline";
import { Observable } from "rxjs";
import { ThroughStream } from "through";
import Choice = require("./lib/objects/choice");
import Choices = require("./lib/objects/choices");
import "./lib/objects/separator";
import "./lib/prompts/base";
import CheckboxPrompt = require("./lib/prompts/checkbox");
import ConfirmPrompt = require("./lib/prompts/confirm");
import EditorPrompt = require("./lib/prompts/editor");
import ExpandPrompt = require("./lib/prompts/expand");
import InputPrompt = require("./lib/prompts/input");
import ListPrompt = require("./lib/prompts/list");
import NumberPrompt = require("./lib/prompts/number");
import PasswordPrompt = require("./lib/prompts/password");
import RawListPrompt = require("./lib/prompts/rawlist");
import UI = require("./lib/ui/baseUI");
import "./lib/ui/bottom-bar";
import "./lib/ui/prompt";
import "./lib/utils/events";
import "./lib/utils/paginator";
import "./lib/utils/readline";
import "./lib/utils/screen-manager";

/**
 * Represents a union which preserves autocompletion.
 *
 * @template T
 * The keys which are available for autocompletion.
 *
 * @template F
 * The fallback-type.
 */
type LiteralUnion<T extends F, F = string> = T | (F & {});

/**
 * Represents a function for prompting questions to the user.
 */
export interface PromptFunction {
    /**
     * Prompts the questions to the user.
     */
    <T extends Answers = Answers>(questions: QuestionCollection<T>, initialAnswers?: Partial<T>): Promise<T>;
}

/**
 * Provides prompts for answering questions.
 */
export interface PromptModuleBase extends PromptFunction {
    /**
     * Registers a new prompt-type.
     *
     * @param name
     * The name of the prompt.
     *
     * @param prompt
     * The constructor of the prompt.
     */
    registerPrompt(name: string, prompt: prompts.PromptConstructor): void;

    /**
     * Registers the default prompts.
     */
    restoreDefaultPrompts(): void;
}

/**
 * Represents a function for registering a prompt.
 */
type RegisterFunction = PromptModuleBase["registerPrompt"];

/**
 * Represents a function for restoring a prompt.
 */
type RestoreFunction = PromptModuleBase["restoreDefaultPrompts"];

/**
 * Represents a list-based question.
 *
 * @template T
 * The type of the answers.
 *
 * @template TChoiceMap
 * The valid choices for the question.
 */
interface ListQuestionOptionsBase<T extends Answers, TChoiceMap> extends Question<T> {
    /**
     * The choices of the prompt.
     */
    choices?: AsyncDynamicQuestionProperty<ReadonlyArray<DistinctChoice<T, TChoiceMap>>, T> | undefined;

    /**
     * The number of elements to show on each page.
     */
    pageSize?: number | undefined;
}

/**
 * Represents either a key of {@link T `T`} or a {@link String `string`}.
 *
 * @template T
 * The type of the keys to suggest.
 */
export type KeyUnion<T> = LiteralUnion<Extract<keyof T, string>>;

/**
 * Converts the specified union-type {@link U `U`} to an intersection-type.
 *
 * @template U
 * The union to convert to an intersection.
 */
export type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I
    : never;

/**
 * A set of answers.
 */
export interface Answers extends Record<string, any> {}

/**
 * Provides the functionality to validate answers.
 *
 * @template T
 * The type of the answers.
 */
export type Validator<T extends Answers = Answers> = Question<T>["validate"];

/**
 * Provides the functionality to transform an answer.
 *
 * @template T
 * The type of the answers.
 */
export type Transformer<T extends Answers = Answers> = InputQuestionOptions<T>["transformer"];

/**
 * Represents a dynamic property for a question.
 *
 * @template T
 * The type of the property.
 *
 * @template TAnswers
 * The type of the answers.
 */
export type DynamicQuestionProperty<T, TAnswers extends Answers = Answers> = T | ((answers: TAnswers) => T);

/**
 * Represents a dynamic property for a question which can be fetched asynchronously.
 *
 * @template T
 * The type of the property.
 *
 * @template TAnswers
 * The type of the answers.
 */
export type AsyncDynamicQuestionProperty<T, TAnswers extends Answers = Answers> = DynamicQuestionProperty<
    T | Promise<T>,
    TAnswers
>;

/**
 * Represents a choice-item.
 */
export interface ChoiceBase {
    /**
     * The type of the choice.
     */
    type?: string | undefined;
}

/**
 * Provides options for a choice of the {@link ListPrompt `ListPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ListChoiceOptions<T extends Answers = Answers> extends ChoiceOptions {
    /**
     * A value indicating whether the choice is disabled.
     */
    disabled?: DynamicQuestionProperty<boolean | string, T> | undefined;
}

/**
 * Provides options for a choice of the {@link CheckboxPrompt `CheckboxPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface CheckboxChoiceOptions<T extends Answers = Answers> extends ListChoiceOptions<T> {
    /**
     * A value indicating whether the choice should be initially checked.
     */
    checked?: boolean | undefined;
}

/**
 * Provides options for a choice of the {@link ExpandPrompt `ExpandPrompt<TQuestion>`}.
 */
export interface ExpandChoiceOptions extends ChoiceOptions {
    /**
     * The key to press for selecting the choice.
     */
    key?: string | undefined;
}

/**
 * Represents a separator.
 */
export interface SeparatorOptions extends ChoiceBase {
    /**
     * Gets the type of the choice.
     */
    type: "separator";

    /**
     * Gets or sets the text of the separator.
     */
    line?: string | undefined;
}

/**
 * Provides options for a choice.
 */
export interface ChoiceOptions extends ChoiceBase {
    /**
     * @inheritdoc
     */
    type?: "choice" | undefined;

    /**
     * The name of the choice to show to the user.
     */
    name?: string | undefined;

    /**
     * The value of the choice.
     */
    value?: any;

    /**
     * The short form of the name of the choice.
     */
    short?: string | undefined;

    /**
     * The extra properties of the choice.
     */
    extra?: any;
}

/**
 * Provides all valid choice-types for any kind of question.
 *
 * @template T
 * The type of the answers.
 */
export interface BaseChoiceMap<T extends Answers = Answers> {
    Choice: Choice<T>;
    ChoiceOptions: ChoiceOptions;
    Separator: Separator;
    SeparatorOptions: SeparatorOptions;
}

/**
 * Provides all valid choice-types for the {@link ListQuestion `ListQuestion<T>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ListChoiceMap<T extends Answers = Answers> extends BaseChoiceMap<T> {
    ListChoiceOptions: ListChoiceOptions<T>;
}

/**
 * Provides all valid choice-types for the {@link CheckboxQuestion `CheckboxQuestion<T>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface CheckboxChoiceMap<T extends Answers = Answers> extends BaseChoiceMap<T> {
    CheckboxChoiceOptions: CheckboxChoiceOptions<T>;
}

/**
 * Provides all valid choice-types for the {@link ExpandQuestion `ExpandQuestion<T>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ExpandChoiceMap<T extends Answers = Answers> extends BaseChoiceMap<T> {
    ExpandChoiceOptions: ExpandChoiceOptions;
}

/**
 * Provides all valid choice-types.
 *
 * @template T
 * The type of the answers.
 */
export interface AllChoiceMap<T extends Answers = Answers> {
    BaseChoiceMap: BaseChoiceMap<T>[keyof BaseChoiceMap<T>];
    ListChoiceMap: ListChoiceMap<T>[keyof ListChoiceMap<T>];
    CheckboxChoiceMap: CheckboxChoiceMap<T>[keyof CheckboxChoiceMap<T>];
    ExpandChoiceMap: ExpandChoiceMap<T>[keyof ExpandChoiceMap<T>];
}

/**
 * Provides valid choices for the question of the {@link TChoiceMap `TChoiceMap`}.
 *
 * @template TAnswers
 * The type of the answers.
 *
 * @template TChoiceMap
 * The choice-types to provide.
 */
export type DistinctChoice<TAnswers extends Answers = Answers, TChoiceMap = AllChoiceMap<TAnswers>> =
    | string
    | TChoiceMap[keyof TChoiceMap];

/**
 * Represents a set of choices.
 *
 * @template T
 * The type of the answers.
 */
export type ChoiceCollection<T extends Answers = Answers> = Array<DistinctChoice<AllChoiceMap<T>>>;

/**
 * Provides options for a question.
 *
 * @template T
 * The type of the answers.
 */
export interface Question<T extends Answers = Answers> {
    /**
     * The type of the question.
     */
    type?: string | undefined;

    /**
     * The key to save the answer to the answers-hash.
     */
    name?: KeyUnion<T> | undefined;

    /**
     * The message to show to the user.
     */
    message?: AsyncDynamicQuestionProperty<string, T> | undefined;

    /**
     * The default value of the question.
     */
    default?: AsyncDynamicQuestionProperty<any, T> | undefined;

    /**
     * The prefix of the {@link message `message`}.
     */
    prefix?: string | undefined;

    /**
     * The suffix of the {@link message `message`}.
     */
    suffix?: string | undefined;

    /**
     * Post-processes the answer.
     *
     * @param input
     * The answer provided by the user.
     *
     * @param answers
     * The answers provided by the user.
     */
    filter?(input: any, answers: T): any;

    /**
     * A value indicating whether the question should be prompted.
     */
    when?: AsyncDynamicQuestionProperty<boolean, T> | undefined;

    /**
     * Validates the integrity of the answer.
     *
     * @param input
     * The answer provided by the user.
     *
     * @param answers
     * The answers provided by the user.
     *
     * @returns
     * Either a value indicating whether the answer is valid or a {@link String `string`} which describes the error.
     */
    validate?(input: any, answers?: T): boolean | string | Promise<boolean | string>;

    /**
     * Force to prompt the question if the answer already exists.
     */
    askAnswered?: boolean;
}

/**
 * Represents the possible answers of each question in the prompt
 */
export type QuestionAnswer<T extends Answers = Answers> = {
    [K in keyof T]: {
        name: K;
        answer: T[K];
    };
}[keyof T];

/**
 * Provides options for a question for the {@link InputPrompt `InputPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface InputQuestionOptions<T extends Answers = Answers> extends Question<T> {
    /**
     * Transforms the value to display to the user.
     *
     * @param input
     * The input provided by the user.
     *
     * @param answers
     * The answers provided by the users.
     *
     * @param flags
     * Additional information about the value.
     *
     * @returns
     * The value to display to the user.
     */
    transformer?(input: any, answers: T, flags: { isFinal?: boolean | undefined }): string | Promise<string>;
}

/**
 * Provides options for a question for the {@link InputPrompt `InputPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface InputQuestion<T extends Answers = Answers> extends InputQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type?: "input" | undefined;
}

/**
 * Provides options for a question for the {@link NumberPrompt `NumberPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface NumberQuestionOptions<T extends Answers = Answers> extends InputQuestionOptions<T> {}

/**
 * Provides options for a question for the {@link NumberPrompt `NumberPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface NumberQuestion<T extends Answers = Answers> extends NumberQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "number";
}

/**
 * Provides options for a question for the {@link PasswordPrompt `PasswordPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface PasswordQuestionOptions<T extends Answers = Answers> extends InputQuestionOptions<T> {
    /**
     * The character to replace the user-input.
     */
    mask?: string | undefined;
}

/**
 * Provides options for a question for the {@link PasswordPrompt `PasswordPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface PasswordQuestion<T extends Answers = Answers> extends PasswordQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "password";
}

/**
 * Represents a list-based question that can loop.
 *
 * @template T
 * The type of the answers.
 *
 * @template TChoiceMap
 * The valid choices for the question.
 */
export interface LoopableListQuestionOptionsBase<T extends Answers, TChoiceMap>
    extends ListQuestionOptionsBase<T, TChoiceMap>
{
    /**
     * A value indicating whether choices in a list should be looped.
     */
    loop?: boolean | undefined;
}

/**
 * Provides options for a question for the {@link ListPrompt `ListPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ListQuestionOptions<T extends Answers = Answers>
    extends LoopableListQuestionOptionsBase<T, ListChoiceMap<T>>
{}

/**
 * Provides options for a question for the {@link ListPrompt `ListPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ListQuestion<T extends Answers = Answers> extends ListQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "list";
}

/**
 * Provides options for a question for the {@link RawListPrompt `RawListPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface RawListQuestionOptions<T extends Answers = Answers> extends ListQuestionOptions<T> {}

/**
 * Provides options for a question for the {@link RawListPrompt `RawListPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface RawListQuestion<T extends Answers = Answers> extends RawListQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "rawlist";
}

/**
 * Provides options for a question for the {@link ExpandPrompt `ExpandPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ExpandQuestionOptions<T extends Answers = Answers>
    extends ListQuestionOptionsBase<T, ExpandChoiceMap<T>>
{}

/**
 * Provides options for a question for the {@link ExpandPrompt `ExpandPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ExpandQuestion<T extends Answers = Answers> extends ExpandQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "expand";
}

/**
 * Provides options for a question for the {@link CheckboxPrompt `CheckboxPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface CheckboxQuestionOptions<T extends Answers = Answers>
    extends LoopableListQuestionOptionsBase<T, CheckboxChoiceMap<T>>
{}

/**
 * Provides options for a question for the {@link CheckboxPrompt `CheckboxPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface CheckboxQuestion<T extends Answers = Answers> extends CheckboxQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "checkbox";
}

/**
 * Provides options for a question for the {@link ConfirmPrompt `ConfirmPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ConfirmQuestionOptions<T extends Answers = Answers> extends Question<T> {}

/**
 * Provides options for a question for the {@link ConfirmPrompt `ConfirmPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface ConfirmQuestion<T extends Answers = Answers> extends ConfirmQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "confirm";
}

/**
 * Provides options for a question for the {@link EditorPrompt `EditorPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface EditorQuestionOptions<T extends Answers = Answers> extends Question<T> {
    /**
     * The postfix of the file being edited.
     *
     * Adding this will add color highlighting to the file content in most editors.
     */
    postfix?: string;
}

/**
 * Provides options for a question for the {@link EditorPrompt `EditorPrompt<TQuestion>`}.
 *
 * @template T
 * The type of the answers.
 */
export interface EditorQuestion<T extends Answers = Answers> extends EditorQuestionOptions<T> {
    /**
     * @inheritdoc
     */
    type: "editor";
}

/**
 * Provides the available question-types.
 *
 * @template T
 * The type of the answers.
 */
export interface QuestionMap<T extends Answers = Answers> {
    /**
     * The {@link InputQuestion `InputQuestion<T>`} type.
     */
    input: InputQuestion<T>;

    /**
     * The {@link NumberQuestion `NumberQuestion<T>`} type.
     */
    number: NumberQuestion<T>;

    /**
     * The {@link PasswordQuestion `PasswordQuestion<T>`} type.
     */
    password: PasswordQuestion<T>;

    /**
     * The {@link ListQuestion `ListQuestion<T>`} type.
     */
    list: ListQuestion<T>;

    /**
     * The {@link RawListQuestion `RawListQuestion<T>`} type.
     */
    rawList: RawListQuestion<T>;

    /**
     * The {@link ExpandQuestion `ExpandQuestion<T>`} type.
     */
    expand: ExpandQuestion<T>;

    /**
     * The {@link CheckboxQuestion `CheckboxQuestion<T>`} type.
     */
    checkbox: CheckboxQuestion<T>;

    /**
     * The {@link ConfirmQuestion `ConfirmQuestion<T>`} type.
     */
    confirm: ConfirmQuestion<T>;

    /**
     * The {@link EditorQuestion `EditorQuestion<T>`} type.
     */
    editor: EditorQuestion<T>;
}

/**
 * Represents one of the available questions.
 *
 * @template T
 * The type of the answers.
 */
export type DistinctQuestion<T extends Answers = Answers> = QuestionMap<T>[keyof QuestionMap<T>];

/**
 * Indicates the type of a question
 */
export type QuestionTypeName = DistinctQuestion["type"];

/**
 * Represents a collection of questions.
 *
 * @template T
 * The type of the answers.
 */
export type QuestionCollection<T extends Answers = Answers> =
    | DistinctQuestion<T>
    | ReadonlyArray<DistinctQuestion<T>>
    | Observable<DistinctQuestion<T>>
    | { [P in KeyUnion<T>]?: (DistinctQuestion<T> & { name?: never }) };

/**
 * Provides an input and an output-stream.
 */
export interface StreamOptions {
    /**
     * A stream to read the input from.
     */
    input?: NodeJS.ReadStream | undefined;

    /**
     * A stream to write the output to.
     */
    output?: NodeJS.WriteStream | undefined;

    /**
     * Whether to display prompts if input is not a TTY.
     */
    skipTTYChecks?: boolean | undefined;
}

/**
 * Provides the functionality to prompt questions to the user.
 */
export interface PromptModule extends PromptModuleBase {
    /**
     * The prompts of the prompt-module.
     */
    prompts: prompts.PromptCollection;

    /**
     * Prompts the questions to the user.
     */
    <T extends Answers = Answers>(
        questions: QuestionCollection<T>,
        initialAnswers?: Partial<T>,
    ): Promise<T> & { ui: ui.Prompt<T> };

    /**
     * Registers a new prompt-type.
     *
     * @param name
     * The name of the prompt.
     *
     * @param prompt
     * The constructor of the prompt.
     */
    registerPrompt(name: string, prompt: prompts.PromptConstructor): this;
}

/**
 * Provides components for the prompts.
 */
export namespace prompts {
    /**
     * Provides options for a prompt.
     *
     * @template T
     * The type of the answers.
     */
    type PromptOptions<T extends Question = Question> = T & {
        /**
         * The choices of the prompt.
         */
        choices: Choices;
    };

    /**
     * Represents the state of a prompt.
     */
    type PromptState = LiteralUnion<"pending" | "idle" | "loading" | "answered" | "done">;

    /**
     * Represents a prompt.
     */
    interface PromptBase {
        /**
         * Gets or sets a string which represents the state of the prompt.
         */
        status: PromptState;

        /**
         * Runs the prompt.
         *
         * @returns
         * The result of the prompt.
         */
        run(): Promise<any>;
    }

    /**
     * Provides the functionality to initialize new prompts.
     */
    interface PromptConstructor {
        /**
         * Initializes a new instance of a prompt.
         *
         * @param question
         * The question to prompt.
         *
         * @param readLine
         * An object for reading from the command-line.
         *
         * @param answers
         * The answers provided by the user.
         */
        new(question: any, readLine: ReadlineInterface, answers: Answers): PromptBase;
    }

    /**
     * Provides a set of prompt-constructors.
     */
    type PromptCollection = Record<string, PromptConstructor>;

    /**
     * Provides data about the state of a prompt.
     */
    interface PromptStateData {
        /**
         * Either a {@link String `string`} which describes the error of the prompt or a {@link Boolean `boolean`} indicating whether the prompt-value is valid.
         */
        isValid: string | boolean;
    }

    /**
     * Provides data about the successful state of a prompt.
     *
     * @param T
     * The type of the answer.
     */
    interface SuccessfulPromptStateData<T = any> extends PromptStateData {
        /**
         * @inheritdoc
         */
        isValid: true;

        /**
         * The value of the prompt.
         */
        value: T;
    }

    /**
     * Provides data about the failed state of a prompt.
     */
    interface FailedPromptStateData extends PromptStateData {
        /**
         * @inheritdoc
         */
        isValid: false | string;
    }

    /**
     * Provides pipes for handling events of a prompt.
     *
     * @param T
     * The type of the answer.
     */
    interface PromptEventPipes<T = any> {
        /**
         * A pipeline for successful inputs.
         */
        success: Observable<SuccessfulPromptStateData<T>>;

        /**
         * An object representing an error.
         */
        error: Observable<FailedPromptStateData>;
    }
}

/**
 * Provides components for the ui.
 */
export namespace ui {
    /**
     * Represents the bottom-bar UI.
     */
    class BottomBar extends UI {
        /**
         * Gets or sets a stream to write logs to.
         */
        log: ThroughStream;

        /**
         * Initializes a new instance of the {@link BottomBar `BottomBar`} class.
         *
         * @param options
         * Provides options for the bottom-bar ui.
         */
        constructor(options?: BottomBarOptions);

        /**
         * Renders the specified {@link text `text`} to the bottom bar.
         *
         * @param text
         * The text to print to the bottom bar.
         */
        updateBottomBar(text: string): this;

        /**
         * Renders the bottom bar.
         */
        protected render(): this;

        /**
         * Cleans the bottom bar.
         */
        protected clean(): this;

        /**
         * Writes a message to the bottom bar.
         *
         * @param message
         * The message to write.
         */
        protected write(message: string): void;

        /**
         * Writes the specified {@link data `data`} to the log-zone.
         *
         * @param data
         * The data to write to the log-zone.
         */
        protected writeLog(data: any): this;

        /**
         * Fixes the new-line characters of the specified {@link text `text`}.
         *
         * @param text
         * The text to process.
         */
        protected enforceLF(text: string): string;
    }

    /**
     * Represents the prompt ui.
     */
    class Prompt<T extends Answers = Answers> extends UI {
        /**
         * Gets or sets the prompts of the ui.
         */
        prompts: prompts.PromptCollection;

        /**
         * Gets or sets the answers provided by the user.
         */
        answers: T;

        /**
         * Gets or sets the event-flow of the process.
         */
        process: Observable<QuestionAnswer<T>>;

        /**
         * Initializes a new instance of the {@link Prompt `Prompt`} class.
         *
         * @param prompts
         * The prompts for the ui.
         *
         * @param options
         * The input- and output-stream of the ui.
         */
        constructor(prompts: prompts.PromptCollection, options?: StreamOptions);

        /**
         * Runs the prompt-UI.
         *
         * @param questions
         * The questions to prompt the user to answer.
         *
         * @returns
         * The answers provided by the user.
         */
        run(questions: Array<DistinctQuestion<T>>): Promise<T>;

        /**
         * Finishes the process.
         */
        protected onCompletion(): T;

        /**
         * Processes a question.
         *
         * @param question
         * The question to process.
         *
         * @returns
         * The answer to the question.
         */
        protected processQuestion(
            question: DistinctQuestion<T>,
        ): Observable<FetchedAnswer>;

        /**
         * Fetches the answer to a question.
         *
         * @param question
         * The question to fetch the answer for.
         *
         * @returns
         * The answer to the question.
         */
        protected fetchAnswer(
            question: FetchedQuestion<T>,
        ): Observable<FetchedAnswer>;

        /**
         * Sets the type of the question if no question-type is specified.
         *
         * @param question
         * The question to set the default type for.
         *
         * @returns
         * The processed question.
         */
        protected setDefaultType(
            question: DistinctQuestion<T>,
        ): Observable<DistinctQuestion<T>>;

        /**
         * Filters the question if it is runnable.
         *
         * @param question
         * The question to filter.
         *
         * @returns
         * Either the event-flow of the question if it is runnable or an empty event-flow.
         */
        protected filterIfRunnable(
            question: DistinctQuestion<T>,
        ): Observable<DistinctQuestion<T>>;
    }

    /**
     * Provides options for the bottom-bar UI.
     */
    interface BottomBarOptions extends StreamOptions {
        /**
         * The initial text to display.
         */
        bottomBar?: string | undefined;
    }

    /**
     * Represents a fetched answer.
     *
     * @template T
     * The type of the answers.
     */
    type FetchedQuestion<T extends Answers = Answers> = DistinctQuestion<T> & {
        /**
         * The type of the question.
         */
        type: string;

        /**
         * The message to show to the user.
         */
        message: string;

        /**
         * The default value of the question.
         */
        default: any;

        /**
         * The choices of the question.
         */
        choices: ChoiceCollection<T>;
    };

    /**
     * Represents a fetched answer.
     */
    interface FetchedAnswer {
        /**
         * The name of the answer.
         */
        name: string;

        /**
         * The value of the answer.
         */
        answer: any;
    }
}

/**
 * Represents a choice-item separator.
 */
export class Separator implements SeparatorOptions {
    /**
     * @inheritdoc
     */
    readonly type: "separator";

    /**
     * @inheritdoc
     */
    line: string;

    /**
     * Initializes a new instance of the {@link Separator `Separator`} class.
     *
     * @param line
     * The text of the separator.
     */
    constructor(line?: string);

    /**
     * Checks whether the specified {@link item `item`} is not a separator.
     *
     * @param item
     * The item to check.
     *
     * @returns
     * A value indicating whether the item is not a separator.
     */
    static exclude(item: any): boolean;
}

/**
 * Registers a new prompt-type.
 *
 * @param name
 * The name of the prompt.
 *
 * @param prompt
 * The constructor of the prompt.
 */
export let registerPrompt: RegisterFunction;

/**
 * Registers the default prompts.
 */
export let restoreDefaultPrompts: RestoreFunction;

/**
 * Creates a prompt-module.
 *
 * @param opt
 * The streams for the prompt-module.
 *
 * @returns
 * The new prompt-module.
 */
export function createPromptModule(opt?: StreamOptions): PromptModule;

/**
 * The default prompt-module.
 */
export let prompt: PromptModule;

/**
 * The prompts of the default prompt-module.
 *
 * @deprecated
 */
export let prompts: {};

export {};