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118 lines
3.2 KiB
118 lines
3.2 KiB
const { promises: fs } = require('fs');
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const path = require('path');
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const Koa = require('koa');
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const { isObject, mapValues } = require('lodash');
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const CURRENT_STATE_KEY = '__CURRENT__';
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const DEFAULT_STATE_KEY = '__DEFAULT__';
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const FIXTURE_SERVER_HOST = 'localhost';
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const FIXTURE_SERVER_PORT = 12345;
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const fixtureSubstitutionPrefix = '__FIXTURE_SUBSTITUTION__';
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const fixtureSubstitutionCommands = {
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currentDateInMilliseconds: 'currentDateInMilliseconds',
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};
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/**
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* Perform substitutions on a single piece of state.
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*
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* @param {unknown} partialState - The piece of state to perform substitutions on.
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* @returns {unknown} The partial state with substititions performed.
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*/
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function performSubstitution(partialState) {
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if (Array.isArray(partialState)) {
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return partialState.map(performSubstitution);
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} else if (isObject(partialState)) {
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return mapValues(partialState, performSubstitution);
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} else if (
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typeof partialState === 'string' &&
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partialState.startsWith(fixtureSubstitutionPrefix)
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) {
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const substitutionCommand = partialState.substring(
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fixtureSubstitutionPrefix.length,
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);
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if (
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substitutionCommand ===
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fixtureSubstitutionCommands.currentDateInMilliseconds
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) {
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return new Date().getTime();
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}
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throw new Error(`Unknown substitution command: ${substitutionCommand}`);
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}
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return partialState;
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}
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/**
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* Substitute values in the state fixture.
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*
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* @param {object} rawState - The state fixture.
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* @returns {object} The state fixture with substitutions performed.
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*/
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function performStateSubstitutions(rawState) {
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return mapValues(rawState, performSubstitution);
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}
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class FixtureServer {
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constructor() {
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this._app = new Koa();
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this._stateMap = new Map([[DEFAULT_STATE_KEY, Object.create(null)]]);
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this._initialStateCache = new Map();
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this._app.use(async (ctx) => {
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// Firefox is _super_ strict about needing CORS headers
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ctx.set('Access-Control-Allow-Origin', '*');
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if (this._isStateRequest(ctx)) {
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ctx.body = this._stateMap.get(CURRENT_STATE_KEY);
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}
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});
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}
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async start() {
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const options = {
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host: FIXTURE_SERVER_HOST,
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port: FIXTURE_SERVER_PORT,
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exclusive: true,
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};
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return new Promise((resolve, reject) => {
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this._server = this._app.listen(options);
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this._server.once('error', reject);
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this._server.once('listening', resolve);
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});
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}
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async stop() {
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if (!this._server) {
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return;
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}
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await new Promise((resolve, reject) => {
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this._server.close();
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this._server.once('error', reject);
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this._server.once('close', resolve);
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});
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}
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async loadState(directory) {
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const statePath = path.resolve(__dirname, directory, 'state.json');
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let state;
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if (this._initialStateCache.has(statePath)) {
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state = this._initialStateCache.get(statePath);
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} else {
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const data = await fs.readFile(statePath);
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const rawState = JSON.parse(data.toString('utf-8'));
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state = performStateSubstitutions(rawState);
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this._initialStateCache.set(statePath, state);
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}
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this._stateMap.set(CURRENT_STATE_KEY, state);
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}
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_isStateRequest(ctx) {
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return ctx.method === 'GET' && ctx.path === '/state.json';
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}
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}
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module.exports = FixtureServer;
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