Revalidation request

index.js

@@ -347,4 +347,29 @@ module.exports = class CachePolicy {
             reqcc: this._reqcc,
         };
     }
+
+    validationRequest(req) {
+        this._assertRequestHasHeaders(req);
+        if (!(this._resHeaders.etag || this._resHeaders["last-modified"])) {
+            return null; // no validators available
+        }
+        // revalidation allowed via HEAD
+        if (!this._requestMatches(req, true)) {
+            return null; // not for the same resource
+        }
+        const vreq = Object.assign({}, req);
+        vreq.headers = Object.assign({}, req.headers);
+
+        /* MUST send that entity-tag in any cache validation request (using If-Match or If-None-Match) if an entity-tag has been provided by the origin server. */
+        if (this._resHeaders.etag) {
+            vreq.headers['if-none-match'] = this._resHeaders.etag;
+        }
+        /* SHOULD send the Last-Modified value in non-subrange cache validation requests (using If-Modified-Since) if only a Last-Modified value has been provided by the origin server.
+        Note: This implementation does not understand partial responses (206) */
+        if (this._resHeaders['last-modified']) {
+            vreq.headers['if-modified-since'] = this._resHeaders['last-modified'];
+        }
+
+        return vreq;
+    }
 };

test/revalidatetest.js

@@ -0,0 +1,65 @@
+'use strict';
+
+const assert = require('assert');
+const CachePolicy = require('..');
+
+const simpleRequest = {method:'GET',headers:{host:'www.w3c.org'},url:'/Protocols/rfc2616/rfc2616-sec14.html'};
+const simpleRequestBut = overrides=>Object.assign({},simpleRequest,overrides);
+
+const cacheableResponse = {headers:{'cache-control':'max-age=111'}};
+const etaggedResponse = {headers:Object.assign({'etag':'"123456789"'},cacheableResponse.headers)};
+const lastModifiedResponse = {headers:Object.assign({'last-modified':'Tue, 15 Nov 1994 12:45:26 GMT'},cacheableResponse.headers)};
+const multiValidatorResponse = {headers:Object.assign({},etaggedResponse.headers,lastModifiedResponse.headers)};
+const alwaysVariableResponse = {headers:Object.assign({'vary':'*'},cacheableResponse.headers)};
+
+describe('Can be revalidated?', function() {
+    it('ok if method changes to HEAD',function(){
+       const cache = new CachePolicy(simpleRequest,etaggedResponse);
+       assert(cache.validationRequest(simpleRequestBut({method:'HEAD'})));
+    });
+    it('not if method mismatch (other than HEAD)',function(){
+       const cache = new CachePolicy(simpleRequest,etaggedResponse);
+       assert(!cache.validationRequest(simpleRequestBut({method:'POST'})));
+    });
+    it('not if url mismatch',function(){
+       const cache = new CachePolicy(simpleRequest,etaggedResponse);
+       assert(!cache.validationRequest(simpleRequestBut({url:'/yomomma'}))); 
+    });
+    it('not if host mismatch',function(){
+        const cache = new CachePolicy(simpleRequest,etaggedResponse);
+        assert(!cache.validationRequest(simpleRequestBut({headers:{host:'www.w4c.org'}})))
+    });
+    it('not if vary fields prevent',function(){
+       const cache = new CachePolicy(simpleRequest,alwaysVariableResponse);
+       assert(!cache.validationRequest(simpleRequest));
+    });
+    it('when entity tag validator is present', function() {
+        const cache = new CachePolicy(simpleRequest, etaggedResponse);
+        assert(cache.validationRequest(simpleRequest));
+    });
+    it('when last-modified validator is present', function() {
+       const cache = new CachePolicy(simpleRequest, lastModifiedResponse);
+       assert(cache.validationRequest(simpleRequest));
+    });
+    it('not without validators', function() {
+        const cache = new CachePolicy(simpleRequest, cacheableResponse);
+        assert(!cache.validationRequest(simpleRequest));
+    })
+
+});
+
+describe('Validation request', function(){
+    it('must contain any etag',function(){
+        const cache = new CachePolicy(simpleRequest,multiValidatorResponse);
+        const expected = multiValidatorResponse.headers.etag;
+        const actual = cache.validationRequest(simpleRequest).headers['if-none-match'];
+        assert.equal(actual,expected);
+    });
+    it('should send the Last-Modified value',function(){
+        const cache = new CachePolicy(simpleRequest,multiValidatorResponse);
+        const expected = multiValidatorResponse.headers['last-modified'];
+        const actual = cache.validationRequest(simpleRequest).headers['if-modified-since'];
+        assert.equal(actual,expected);
+    });
+    
+});