import Ecs from '@/ecs/ecs.js';
import Script from '@/util/script.js';

import {LRUCache} from 'lru-cache';

const cache = new LRUCache({
  max: 128,
});

export default class ClientEcs extends Ecs {
  async readAsset(uri) {
    if (!cache.has(uri)) {
      let promise, resolve, reject;
      promise = new Promise((res, rej) => {
        resolve = res;
        reject = rej;
      });
      cache.set(uri, promise);
      fetch(new URL(uri, window.location.origin))
        .then(async (response) => {
          resolve(response.ok ? response.arrayBuffer() : new ArrayBuffer(0));
        })
        .catch(reject);
    }
    return cache.get(uri);
  }
  async readJson(uri) {
    const key = ['$$json', uri].join(':');
    if (!cache.has(key)) {
      let promise, resolve, reject;
      promise = new Promise((res, rej) => {
        resolve = res;
        reject = rej;
      });
      cache.set(key, promise);
      this.readAsset(uri)
        .then((chars) => {
          resolve(chars.byteLength > 0 ? JSON.parse((new TextDecoder()).decode(chars)) : {});
        })
        .catch(reject);
    }
    return cache.get(key);
  }
  async readScript(uriOrCode, context = {}) {
    if (!uriOrCode) {
      return undefined;
    }
    let code = '';
    if (!uriOrCode.startsWith('/')) {
      code = uriOrCode;
    }
    else {
      const buffer = await this.readAsset(uriOrCode);
      if (buffer.byteLength > 0) {
        code = (new TextDecoder()).decode(buffer);
      }
    }
    if (code) {
      return Script.fromCode(code, context);
    }
  }
}