49 lines
1.4 KiB
JavaScript
49 lines
1.4 KiB
JavaScript
import assert from "assert";
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import establishedDatabase from "../database/database";
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class Cache {
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constructor(database) {
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this.database = database || establishedDatabase;
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this.queries = {
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read:
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'SELECT value, time_to_live, created_at, DATETIME("now", "localtime") as now, ' +
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'DATETIME(created_at, "+" || time_to_live || " seconds") as expires ' +
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"FROM cache WHERE key = ? AND now < expires",
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create:
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"INSERT OR REPLACE INTO cache (key, value, time_to_live) VALUES (?, ?, ?)"
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};
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}
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/**
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* Retrieve an unexpired cache entry by key.
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* @param {String} key of the cache entry
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* @returns {Object}
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*/
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get(key) {
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return Promise.resolve()
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.then(() => this.database.get(this.queries.read, [key]))
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.then(row => {
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assert(row, "Could not find cache entry with that key.");
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return JSON.parse(row.value);
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});
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}
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/**
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* Insert cache entry with key and value.
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* @param {String} key of the cache entry
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* @param {String} value of the cache entry
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* @param {Number} timeToLive the number of seconds before entry expires
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* @returns {Object}
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*/
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set(key, value, timeToLive = 10800) {
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const json = JSON.stringify(value);
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return Promise.resolve()
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.then(() =>
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this.database.run(this.queries.create, [key, json, timeToLive])
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)
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.then(() => value);
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}
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}
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export default Cache;
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