import type { IGameContext, PromptEvent } from 'boardgame-core';

export interface PromptHandlerOptions {
  commands: IGameContext<any>['commands'];
  onPrompt: (prompt: PromptEvent) => void;
  onCancel: (reason?: string) => void;
}

export class PromptHandler {
  private commands: IGameContext<any>['commands'];
  private onPrompt: (prompt: PromptEvent) => void;
  private onCancel: (reason?: string) => void;
  private activePrompt: PromptEvent | null = null;
  private isListening = false;
  private pendingInput: string | null = null;

  constructor(options: PromptHandlerOptions) {
    this.commands = options.commands;
    this.onPrompt = options.onPrompt;
    this.onCancel = options.onCancel;
  }

  start(): void {
    this.isListening = true;
    this.listenForPrompt();
  }

  private listenForPrompt(): void {
    if (!this.isListening) return;

    this.commands.promptQueue.pop()
      .then((promptEvent) => {
        this.activePrompt = promptEvent;

        // 如果有等待的输入，自动提交
        if (this.pendingInput) {
          const input = this.pendingInput;
          this.pendingInput = null;
          const error = this.activePrompt.tryCommit(input);
          if (error === null) {
            this.activePrompt = null;
            this.listenForPrompt();
          } else {
            // 提交失败，把 prompt 交给 UI 显示错误
            this.onPrompt(promptEvent);
          }
          return;
        }

        this.onPrompt(promptEvent);
      })
      .catch((reason) => {
        this.activePrompt = null;
        this.onCancel(reason?.message || 'Cancelled');
      });
  }

  /**
   * Submit an input string to the current prompt.
   * @returns null on success (input accepted), error string on validation failure
   */
  submit(input: string): string | null {
    if (!this.activePrompt) {
      // 没有活跃 prompt，保存为待处理输入
      this.pendingInput = input;
      return null;
    }

    const error = this.activePrompt.tryCommit(input);
    if (error === null) {
      this.activePrompt = null;
      this.listenForPrompt();
    }
    return error;
  }

  cancel(reason?: string): void {
    if (this.activePrompt) {
      this.activePrompt.cancel(reason);
      this.activePrompt = null;
    }
    this.onCancel(reason);
  }

  stop(): void {
    this.isListening = false;
    if (this.activePrompt) {
      this.activePrompt.cancel('Handler stopped');
      this.activePrompt = null;
    }
  }

  destroy(): void {
    this.stop();
  }
}

export function createPromptHandler(
  options: PromptHandlerOptions,
): PromptHandler {
  return new PromptHandler(options);
}