// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.

import type { Writer, WriterSync } from "./types.d.ts";

const decoder = new TextDecoder();

/** Writer utility for buffering string chunks */
export class StringWriter implements Writer, WriterSync {
  #chunks: Uint8Array[] = [];
  #byteLength = 0;
  #cache: string | undefined;

  constructor(private base: string = "") {
    const c = new TextEncoder().encode(base);
    this.#chunks.push(c);
    this.#byteLength += c.byteLength;
  }

  write(p: Uint8Array): Promise<number> {
    return Promise.resolve(this.writeSync(p));
  }

  writeSync(p: Uint8Array): number {
    this.#chunks.push(p);
    this.#byteLength += p.byteLength;
    this.#cache = undefined;
    return p.byteLength;
  }

  toString(): string {
    if (this.#cache) {
      return this.#cache;
    }
    const buf = new Uint8Array(this.#byteLength);
    let offs = 0;
    for (const chunk of this.#chunks) {
      buf.set(chunk, offs);
      offs += chunk.byteLength;
    }
    this.#cache = decoder.decode(buf);
    return this.#cache;
  }
}