Commit b304d412 authored by Winnie Hellmann's avatar Winnie Hellmann Committed by Clement Ho

Track pending requests in AjaxCache

parent cb2f739d
const AjaxCache = {
internalStorage: { },
class AjaxCache {
constructor() {
this.internalStorage = { };
this.pendingRequests = { };
}
get(endpoint) {
return this.internalStorage[endpoint];
},
}
hasData(endpoint) {
return Object.prototype.hasOwnProperty.call(this.internalStorage, endpoint);
},
purge(endpoint) {
}
remove(endpoint) {
delete this.internalStorage[endpoint];
},
}
retrieve(endpoint) {
if (AjaxCache.hasData(endpoint)) {
return Promise.resolve(AjaxCache.get(endpoint));
if (this.hasData(endpoint)) {
return Promise.resolve(this.get(endpoint));
}
return new Promise((resolve, reject) => {
$.ajax(endpoint) // eslint-disable-line promise/catch-or-return
.then(data => resolve(data),
(jqXHR, textStatus, errorThrown) => {
const error = new Error(`${endpoint}: ${errorThrown}`);
error.textStatus = textStatus;
reject(error);
},
);
})
.then((data) => { this.internalStorage[endpoint] = data; })
.then(() => AjaxCache.get(endpoint));
},
};
export default AjaxCache;
let pendingRequest = this.pendingRequests[endpoint];
if (!pendingRequest) {
pendingRequest = new Promise((resolve, reject) => {
// jQuery 2 is not Promises/A+ compatible (missing catch)
$.ajax(endpoint) // eslint-disable-line promise/catch-or-return
.then(data => resolve(data),
(jqXHR, textStatus, errorThrown) => {
const error = new Error(`${endpoint}: ${errorThrown}`);
error.textStatus = textStatus;
reject(error);
},
);
})
.then((data) => {
this.internalStorage[endpoint] = data;
delete this.pendingRequests[endpoint];
})
.catch((error) => {
delete this.pendingRequests[endpoint];
throw error;
});
this.pendingRequests[endpoint] = pendingRequest;
}
return pendingRequest.then(() => this.get(endpoint));
}
}
export default new AjaxCache();
......@@ -5,19 +5,13 @@ describe('AjaxCache', () => {
const dummyResponse = {
important: 'dummy data',
};
let ajaxSpy = (url) => {
expect(url).toBe(dummyEndpoint);
const deferred = $.Deferred();
deferred.resolve(dummyResponse);
return deferred.promise();
};
beforeEach(() => {
AjaxCache.internalStorage = { };
spyOn(jQuery, 'ajax').and.callFake(url => ajaxSpy(url));
AjaxCache.pendingRequests = { };
});
describe('#get', () => {
describe('get', () => {
it('returns undefined if cache is empty', () => {
const data = AjaxCache.get(dummyEndpoint);
......@@ -41,7 +35,7 @@ describe('AjaxCache', () => {
});
});
describe('#hasData', () => {
describe('hasData', () => {
it('returns false if cache is empty', () => {
expect(AjaxCache.hasData(dummyEndpoint)).toBe(false);
});
......@@ -59,9 +53,9 @@ describe('AjaxCache', () => {
});
});
describe('#purge', () => {
describe('remove', () => {
it('does nothing if cache is empty', () => {
AjaxCache.purge(dummyEndpoint);
AjaxCache.remove(dummyEndpoint);
expect(AjaxCache.internalStorage).toEqual({ });
});
......@@ -69,7 +63,7 @@ describe('AjaxCache', () => {
it('does nothing if cache contains no matching data', () => {
AjaxCache.internalStorage['not matching'] = dummyResponse;
AjaxCache.purge(dummyEndpoint);
AjaxCache.remove(dummyEndpoint);
expect(AjaxCache.internalStorage['not matching']).toBe(dummyResponse);
});
......@@ -77,14 +71,27 @@ describe('AjaxCache', () => {
it('removes matching data', () => {
AjaxCache.internalStorage[dummyEndpoint] = dummyResponse;
AjaxCache.purge(dummyEndpoint);
AjaxCache.remove(dummyEndpoint);
expect(AjaxCache.internalStorage).toEqual({ });
});
});
describe('#retrieve', () => {
describe('retrieve', () => {
let ajaxSpy;
beforeEach(() => {
spyOn(jQuery, 'ajax').and.callFake(url => ajaxSpy(url));
});
it('stores and returns data from Ajax call if cache is empty', (done) => {
ajaxSpy = (url) => {
expect(url).toBe(dummyEndpoint);
const deferred = $.Deferred();
deferred.resolve(dummyResponse);
return deferred.promise();
};
AjaxCache.retrieve(dummyEndpoint)
.then((data) => {
expect(data).toBe(dummyResponse);
......@@ -94,6 +101,28 @@ describe('AjaxCache', () => {
.catch(fail);
});
it('makes no Ajax call if request is pending', () => {
const responseDeferred = $.Deferred();
ajaxSpy = (url) => {
expect(url).toBe(dummyEndpoint);
// neither reject nor resolve to keep request pending
return responseDeferred.promise();
};
const unexpectedResponse = data => fail(`Did not expect response: ${data}`);
AjaxCache.retrieve(dummyEndpoint)
.then(unexpectedResponse)
.catch(fail);
AjaxCache.retrieve(dummyEndpoint)
.then(unexpectedResponse)
.catch(fail);
expect($.ajax.calls.count()).toBe(1);
});
it('returns undefined if Ajax call fails and cache is empty', (done) => {
const dummyStatusText = 'exploded';
const dummyErrorMessage = 'server exploded';
......
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