Base Prompt System

/**
 * Base class for all prompts providing common functionality
 * @template T - The type of value the prompt will return
 */
class Prompt<T = any> {
  constructor(options: PromptOptions<Prompt>, trackValue?: boolean);
  
  /** Current state of the prompt */
  state: State;
  /** Current error message if any */
  error: string;
  /** Current value of the prompt */
  value: T;
  
  /** Start the prompt and return user input */
  prompt(): Promise<string | symbol>;
  /** Subscribe to prompt events */
  on<K extends keyof ClackEvents>(event: K, cb: ClackEvents[K]): void;
  /** Subscribe to prompt events once */
  once<K extends keyof ClackEvents>(event: K, cb: ClackEvents[K]): void;
  /** Emit prompt events */
  emit<K extends keyof ClackEvents>(event: K, ...data: Parameters<ClackEvents[K]>): void;
}

import { Prompt } from '@clack/core';

// Create a custom prompt by extending Prompt
class CustomPrompt extends Prompt<string> {
  constructor(options: PromptOptions<CustomPrompt>) {
    super(options);
  }
}

// Use with custom render function
const prompt = new CustomPrompt({
  render() {
    return `Custom prompt: ${this.value || '(empty)'}`;
  },
  validate(value) {
    if (!value) return 'Value is required';
  }
});

const result = await prompt.prompt();

/**
 * Base configuration options for all prompt types
 * @template Self - The prompt type being configured
 */
interface PromptOptions<Self> {
  /** Required render function that defines prompt appearance */
  render(this: Omit<Self, 'prompt'>): string | undefined;
  /** Optional placeholder text */
  placeholder?: string;
  /** Optional initial value */
  initialValue?: any;
  /** Optional validation function */
  validate?: (value: any) => string | Error | undefined;
  /** Optional input stream (defaults to stdin) */
  input?: Readable;
  /** Optional output stream (defaults to stdout) */
  output?: Writable;
  /** Optional debug mode */
  debug?: boolean;
  /** Optional abort signal for cancellation */
  signal?: AbortSignal;
}

/**
 * Possible states for a prompt during its lifecycle
 */
type State = 'initial' | 'active' | 'cancel' | 'submit' | 'error';

/**
 * Events that prompts can emit during their lifecycle
 */
interface ClackEvents {
  /** Emitted when prompt is initialized */
  initial: (value?: any) => void;
  /** Emitted when prompt becomes active */
  active: (value?: any) => void;
  /** Emitted when prompt is cancelled */
  cancel: (value?: any) => void;
  /** Emitted when prompt is submitted */
  submit: (value?: any) => void;
  /** Emitted when prompt encounters an error */
  error: (value?: any) => void;
  /** Emitted when cursor position changes */
  cursor: (key?: Action) => void;
  /** Emitted when any key is pressed */
  key: (key?: string) => void;
  /** Emitted when prompt value changes */
  value: (value?: string) => void;
  /** Emitted when confirmation value changes */
  confirm: (value?: boolean) => void;
  /** Emitted when prompt is finalized */
  finalize: () => void;
}

import { TextPrompt } from '@clack/core';

const prompt = new TextPrompt({
  render() {
    return `Enter text: ${this.valueWithCursor}`;
  }
});

// Listen to events
prompt.on('value', (value) => {
  console.log('Value changed:', value);
});

prompt.on('submit', () => {
  console.log('Prompt submitted');
});

prompt.on('cancel', () => {
  console.log('Prompt cancelled');
});

const result = await prompt.prompt();