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/*
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 *  This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
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 *  License: MS-RSL – see LICENSE.md for details
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 */
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/*
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Very, very simple key:value store.
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The keys can be arbitrary json-able objects.
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A frozen copy of the object is saved in the key:value store,
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so it won't get mutated.
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*/
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import json0 from "json-stable-stringify";
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function json(x) {
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  return json0(x) ?? "";
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}
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export const key_value_store = () => new KeyValueStore();
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class KeyValueStore {
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  private _data?: object;
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  constructor() {
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    this.set = this.set.bind(this);
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    this.get = this.get.bind(this);
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    this.delete = this.delete.bind(this);
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    this.close = this.close.bind(this);
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    this._data = {};
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  }
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  assert_not_closed() {
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    if (this._data == null) {
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      throw Error("closed -- KeyValueStore");
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    }
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  }
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  set(key, value) {
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    this.assert_not_closed();
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    if (value.freeze != null) {
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      // supported by modern browsers
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      value = value.freeze(); // so doesn't get mutated
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    }
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    if (this._data) this._data[json(key)!] = value;
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  }
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  get(key) {
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    this.assert_not_closed();
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    return this._data?.[json(key)!];
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  }
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  delete(key) {
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    this.assert_not_closed();
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    delete this._data?.[json(key)!];
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  }
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  close() {
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    delete this._data;
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  }
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}
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