gristlabs_grist-core/app/client/models/gristConfigCache.ts

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/**
* When app.html is fetched, the results for the API calls for getDoc() and getWorker() are
* embedded into the page using window.gristConfig object. When making these calls on the client,
* we check gristConfig to see if we can use these cached values.
*
* Usage is simply:
* getDoc(api, docId)
* getWorker(api, assignmentId)
*
* The cached value is used once only (and reset in gristConfig) and only if marked with a recent
* timestamp. This optimizes the case of loading the page. On subsequent use, these calls will
* translate to the usual api.getDoc(), api.getWorker() calls.
*/
import {urlState} from 'app/client/models/gristUrlState';
import {getWeakestRole} from 'app/common/roles';
import {getGristConfig} from 'app/common/urlUtils';
import {Document, UserAPI} from 'app/common/UserAPI';
// tslint:disable:no-console
const MaxGristConfigAgeMs = 5000;
export async function getDoc(api: UserAPI, docId: string): Promise<Document> {
const value = findAndResetInGristConfig('getDoc', docId);
const result = await (value || api.getDoc(docId));
const mode = urlState().state.get().mode;
if (mode === 'view') {
// This mode will be honored by the websocket; here we make sure the rest of the
// client knows about it too.
result.access = getWeakestRole(result.access, 'viewers');
}
return result;
}
export async function getWorker(api: UserAPI, assignmentId: string): Promise<string> {
const value = findAndResetInGristConfig('getWorker', assignmentId);
return value || api.getWorker(assignmentId);
}
type CallType = "getDoc" | "getWorker";
function findAndResetInGristConfig(method: "getDoc", id: string): Document|null;
function findAndResetInGristConfig(method: "getWorker", id: string): string|null;
function findAndResetInGristConfig(method: CallType, id: string): any {
const gristConfig = getGristConfig();
const methodCache = gristConfig[method];
if (!methodCache || !methodCache[id]) {
console.log(`gristConfigCache ${method}[${id}]: not found`);
return null;
}
// Ignores difference between client and server timestamps, but doing better seems difficult.
const timeSinceServer = Date.now() - gristConfig.timestampMs;
if (timeSinceServer >= MaxGristConfigAgeMs) {
console.log(`gristConfigCache ${method}[${id}]: ${gristConfig.timestampMs} is stale (${timeSinceServer})`);
return null;
}
const value = methodCache[id];
delete methodCache[id]; // To be used only once.
console.log(`gristConfigCache ${method}[${id}]: found and deleted value`, value);
return value;
}