/// <reference no-default-lib="true" />
/// <reference lib="esnext" />
/// <reference lib="dom" />

import { textInput } from "../scrapbox-userscript-std/dom.ts";
import { promisify } from "../async-lib/mod.ts";
import { stringify } from "../vim-like-key-notation/mod.ts";

export const KeyWatcher = class {
  private sequence = "";
  private adaptor = promisify<
      KeyboardEvent | CompositionEvent
    >({ maxQueued: 0 });
  private keyWatcher = this.adaptor[0];
  private handleKey = this.adaptor[1];
  private handleKeydown = (e: KeyboardEvent) => {
    if (e.isComposing) return;
    this.handleKey(e);
  };
  
  constructor(private dom: HTMLElement | Document | (typeof globalThis) = globalThis) {
    this.dom.addEventListener("keydown", this.handleKeydown as EventListener);
    textInput()!.addEventListener("compositionstart", this.handleKey);
  }
  
  public reset(): void {
    this.sequence = "";
  }

  private dispose (): void {
    this.dom.removeEventListener("keydown", this.handleKeydown as EventListener);
    textInput()!.removeEventListener("compositionstart", this.handleKey);
  };
  
  public async* listen(): AsyncGenerator<string> {
    while (true) {
      const event = await this.keyWatcher();
      if (event instanceof KeyboardEvent) {
        this.sequence += stringify(event);
      } else {
        // 入力が確定したときのみ取得する
        const { data } = await new Promise<CompositionEvent>((resolve) => {
          textInput()!.addEventListener("compositionend", resolve, { once: true });
        });
        this.sequence += data;
      }
      yield this.sequence;
    }
  }
};