121 lines
2.7 KiB
JavaScript
121 lines
2.7 KiB
JavaScript
// Note: Only handled objects and primitives are allowed to be set/pushed/mapped
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import { inspect } from 'node:util';
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class Not_Storable_Error extends Error {
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constructor({ storage, value, prop, id }) {
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const type = value === null ? 'null' : typeof value;
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const location = prop ? `property "${prop}" of record #${id}` : `record #${id}`;
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super(`Cannot store value of type "${type}" in ${location}: ${inspect(value)}`);
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this.name = 'Not_Storable_Error';
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this.storage = storage;
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this.value = value;
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}
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}
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class Not_Mutable_Error extends Error {
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constructor({ storage, value, prop, id }) {
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const type = value === null ? 'null' : typeof value;
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const location = prop ? `property "${prop}" of record #${id}` : `record #${id}`;
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super(`Cannot set ${location}: record is immutable (tried to store value of type "${type}": ${inspect(value)})`);
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this.name = 'Not_Mutable_Error';
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this.storage = storage;
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this.value = value;
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}
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}
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function load_descriptor({ type, value }, { storage, mutable }) {
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if (type === 'primitive') {
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return value;
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} else {
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throw new Error('not implemented');
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}
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}
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const Record_Handler = {
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get(target, prop, receiver) {
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const { storage, id, mutable } = target;
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const result_descriptor = storage.get_record_property(id, prop);
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if (result_descriptor) {
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return load_descriptor(result_descriptor, { storage, mutable });
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} else {
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return undefined;
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}
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},
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set(target, prop, value) {
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const { storage, id, mutable } = target;
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if (!mutable) {
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throw new Not_Mutable_Error({ storage, id, prop, value });
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}
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if (!storage.can_be_stored(value)) {
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throw new Not_Storable_Error({ storage, id, prop, value });
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}
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storage.set_record_property(id, prop, value);
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return true;
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}
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};
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class Storage {
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#pending_id = 1;
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#records = new Map();
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create_record(data=undefined, mutable=true) {
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const id = this.acquire_new_id();
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const property_bag = {};
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const result = new Proxy({
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storage: this,
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id,
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property_bag,
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mutable,
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}, Record_Handler);
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this.#records.set(id, property_bag);
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if (data !== undefined) {
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Object.assign(result, data);
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}
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return result;
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}
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get_record_property(item_id, property) {
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console.log("Should get record property", { item_id, property });
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return { type: 'primitive', value: 'Hello' };
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}
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set_record_property(item_id, property, value) {
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console.log("Should set record property", { item_id, property, value });
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}
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can_be_stored(value) {
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if (typeof value === 'string') {
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return true;
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} else {
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return false;
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}
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}
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acquire_new_id() {
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return this.#pending_id++;
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}
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};
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const s1 = new Storage();
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const p1 = s1.create_record({stuff: 'hello'}, true);
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console.log(p1.blargh);
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//p1.stuff = ['hello', 'world'];
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