Add db paginate

.eslintrc

@@ -51,7 +51,6 @@
     "no-trailing-spaces": 2,
     "no-underscore-dangle": 0,
     "no-unneeded-ternary": 1,
-    "one-var": 2,
     "quotes": [2, "single", "avoid-escape"],
     "semi": [2, "always"],
     "keyword-spacing": 2,

lib/responses.js

@@ -445,6 +445,47 @@ function expectJSON(fn, res) {
   }).catch(handleError(res));
 }
 
+/**
+ * Checks the page size requested to make sure it's a Number and within the maximum.
+ * Returns the default or 0 if there's no default or size is not a Number.
+ * @param {Object} req
+ * @returns {number}
+ */
+function checkPageSize(req) {
+  // Casts value to a number > 0 or undefined.
+  const toInt = (n) => Math.floor(Math.abs(Number(n))) || undefined;
+
+  const sizeDefault = toInt(process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE);
+  const sizeParam = toInt(req.query.size);
+  const sizeMax = toInt(process.env.CLAY_STORAGE_MAX_PAGE_SIZE);
+
+  const size = sizeParam || sizeDefault;
+
+  if (size) {
+    return Math.min(sizeMax, size) || size;
+  }
+
+  return sizeMax;
+}
+
+/**
+ * Checks whether the previous value for a page request matches up with the uri,
+ * ie. all the ids returned should contain the request uri.
+ * @param {Object} req
+ * @param {Object} res
+ * @returns {string|undefined}
+ */
+function checkPrevious(req, res) {
+  const prefix = req.uri;
+  const previous = req.query.prev;
+
+  if (previous && prefix && !previous.includes(prefix)) {
+    return handleError(res)(Error('Client: Invalid previous'));
+  }
+
+  return previous;
+}
+
 /**
  * List all things in the db
  * @param {object} [options]
@@ -458,7 +499,9 @@ function list(options) {
     let list,
       listOptions = _.assign({
         prefix: req.uri,
-        values: false
+        values: false,
+        previous: checkPrevious(req, res),
+        size: checkPageSize(req)
       }, options);
 
     list = db.list(listOptions);
@@ -478,7 +521,7 @@ function listWithoutVersions() {
       return [filter({wantStrings: true}, function (str) {
         return str.indexOf('@') === -1;
       })];
-    }
+    },
   };
 
   return list(options);
@@ -603,3 +646,5 @@ module.exports.deleteRouteFromDB = deleteRouteFromDB;
 // For testing
 module.exports.setLog = mock => log = mock;
 module.exports.setDb = mock => db = mock;
+module.exports.checkPrevious = checkPrevious;
+module.exports.checkPageSize = checkPageSize;

lib/responses.test.js

@@ -314,6 +314,124 @@ describe(_.startCase(filename), function () {
     });
   });
 
+  describe('checkPageSize', function () {
+    const fn = lib[this.title];
+
+    afterEach(function () {
+      delete process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE;
+      delete process.env.CLAY_STORAGE_MAX_PAGE_SIZE;
+    });
+
+    it('falls back to default if there is no size param', function () {
+      const req = {
+        query: {},
+        uri: 'domain.com/_components/component/instances',
+      };
+
+      const res = createMockRes();
+
+      process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE = '10';
+
+      expect(fn(req, res)).to.equal(10);
+    });
+
+    it('returns max when max is defined and size > max', function () {
+      const req = {
+        query: { size: '300' },
+        uri: 'domain.com/_components/component/instances',
+      };
+
+      const res = createMockRes();
+
+      process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE = '10';
+      process.env.CLAY_STORAGE_MAX_PAGE_SIZE = '100';
+
+      expect(fn(req, res)).to.equal(100);
+    });
+
+    it('returns valid size that is smaller than max', function () {
+      const req = {
+        query: { size: '42' },
+        uri: 'domain.com/_components/component/instances',
+      };
+
+      const res = createMockRes();
+
+      process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE = '10';
+      process.env.CLAY_STORAGE_MAX_PAGE_SIZE = '100';
+
+      expect(fn(req, res)).to.equal(42);
+    });
+
+    it('returns default for an invalid size query param', function () {
+      const req = {
+        query: { size: 'string' },
+        uri: 'domain.com/_components/component/instances',
+      };
+
+      const res = createMockRes();
+
+      process.env.CLAY_STORAGE_DEFAULT_PAGE_SIZE = '10';
+      process.env.CLAY_STORAGE_MAX_PAGE_SIZE = '100';
+
+      expect(fn(req, res)).to.equal(10);
+    });
+
+    it('returns max when no size or default', function () {
+      const req = {
+        query: {},
+        uri: 'domain.com/_components/component/instances',
+      };
+
+      const res = createMockRes();
+
+      process.env.CLAY_STORAGE_MAX_PAGE_SIZE = '100';
+
+      expect(fn(req, res)).to.equal(100);
+    });
+  });
+
+  describe('checkPrevious', function () {
+    const fn = lib[this.title];
+
+    it('returns valid previous query param value', function () {
+      const req = {
+        query: {
+          prev: 'domain.com/_components/component/instances/aaa',
+        },
+        uri: 'domain.com/_components/component/instances',
+      };
+      const res = createMockRes();
+
+      expect(fn(req, res)).to.equal(
+        'domain.com/_components/component/instances/aaa'
+      );
+    });
+
+    it('throws and responds with 400 for an invalid previous value', function () {
+      const req = {
+        query: {
+          prev: 'random value',
+        },
+        uri: 'domain.com/_components/component/instances',
+      };
+      const res = createMockRes();
+
+      expectStatus(res, 400);
+      fn(req, res);
+    });
+
+    it('returns undefined if no previous value', function () {
+      const req = {
+        query: {},
+        uri: 'domain.com/_components/component/instances',
+      };
+      const res = createMockRes();
+
+      expect(fn(req, res)).to.equal(undefined);
+    });
+  });
+
   describe('list', function () {
     const fn = lib[this.title];