JSON roundtrippin

README.md

@@ -76,6 +76,10 @@ It generally means the response can't be used any more without revalidation with
 
 Returns number of *milliseconds* until the response becomes stale. After that time (when `timeToLive() <= 0`) the response won't be usable without revalidation.
 
+### `toObject()`/`fromObject(json)`
+
+Chances are you'll want to store the `CachePolicy` object along with the cached response. `obj = policy.toObject()` gives a plain JSON-serializable object. `policy = CachePolicy.fromObject(obj)` creates an instance from it.
+
 # Yo, FRESH
 
 ![satisfiesWithoutRevalidation](fresh.jpg)

index.js

@@ -23,7 +23,12 @@ function parseCacheControl(header) {
 }
 
 module.exports = class CachePolicy {
-    constructor(req, res, {shared, cacheHeuristic} = {}) {
+    constructor(req, res, {shared, cacheHeuristic, _fromObject} = {}) {
+        if (_fromObject) {
+            this._fromObject(_fromObject);
+            return;
+        }
+
         if (!res || !res.headers) {
             throw Error("Response headers missing");
         }
@@ -240,4 +245,44 @@ module.exports = class CachePolicy {
     stale() {
         return this.maxAge() <= this.age();
     }
+
+    static fromObject(obj) {
+        return new this(undefined, undefined, {_fromObject:obj});
+    }
+
+    _fromObject(obj) {
+        if (this._responseTime) throw Error("Reinitialized");
+        if (!obj || obj.v !== 1) throw Error("Invalid serialization");
+
+        this._responseTime = obj.t;
+        this._isShared = obj.sh;
+        this._cacheHeuristic = obj.ch;
+        this._status = obj.st;
+        this._resHeaders = obj.resh;
+        this._rescc = obj.rescc;
+        this._method = obj.m;
+        this._url = obj.u;
+        this._host = obj.h;
+        this._noAuthorization = obj.a;
+        this._reqHeaders = obj.reqh;
+        this._reqcc = obj.reqcc;
+    }
+
+    toObject() {
+        return {
+            v:1,
+            t: this._responseTime,
+            sh: this._isShared,
+            ch: this._cacheHeuristic,
+            st: this._status,
+            resh: this._resHeaders,
+            rescc: this._rescc,
+            m: this._method,
+            u: this._url,
+            h: this._host,
+            a: this._noAuthorization,
+            reqh: this._reqHeaders,
+            reqcc: this._reqcc,
+        };
+    }
 };

test/requesttest.js

@@ -35,6 +35,11 @@ describe('Request properties', function() {
         const cache = new CachePolicy({method:'GET',headers:{'authorization': 'test'}}, {headers:{'cache-control':'max-age=0,s-maxage=12'}});
         assert(!cache.stale());
         assert(cache.storable());
+
+        const cache2 = CachePolicy.fromObject(JSON.parse(JSON.stringify(cache.toObject())));
+        assert(cache2 instanceof CachePolicy);
+        assert(!cache2.stale());
+        assert(cache2.storable());
     });
 
     it('Private auth is OK', function() {

test/responsetest.js

@@ -21,6 +21,11 @@ describe('Response headers', function() {
         const cache = new CachePolicy(req, {headers:{'cache-control': ',,,,max-age =  456      ,'}});
         assert(!cache.stale());
         assert.equal(cache.maxAge(), 456);
+
+        const cache2 = CachePolicy.fromObject(JSON.parse(JSON.stringify(cache.toObject())));
+        assert(cache2 instanceof CachePolicy);
+        assert(!cache2.stale());
+        assert.equal(cache2.maxAge(), 456);
     });
 
     it('quoted syntax', function() {
@@ -277,5 +282,10 @@ describe('Response headers', function() {
         assert.equal(h.custom, 'header');
         assert.equal(h.age, '11');
         assert.equal(res.headers.age, '10');
+
+        const cache2 = TimeTravellingPolicy.fromObject(JSON.parse(JSON.stringify(cache.toObject())));
+        assert(cache2 instanceof TimeTravellingPolicy);
+        const h2 = cache2.responseHeaders();
+        assert.deepEqual(h, h2);
     });
 });