Add findUserByEmail (#55)

* Add findUserByEmail

This index already exists, there is just no way to read from it.

* Add unit test for findUserByEmail

Author: Ian Davis

src/user-store.js

@@ -273,6 +273,27 @@ class UserStore {
       })
   }
 
+  /**
+   * Loads and returns a user object for a given email.
+   *
+   * @param email {string}
+   *
+   * @return {Promise<Object>} User info, parsed from a JSON string
+   */
+  findUserByEmail (email) {
+    const emailKey = UserStore.normalizeEmailKey(email)
+
+    return this.backend.get('users-by-email', emailKey)
+      .then(user => {
+        if (user && user.link) {
+          // this is an alias record, fetch the user it points to
+          return this.findUser(user.link)
+        }
+
+        return user
+      })
+  }
+
   /**
    * Creates and returns a salted password hash, for storage with the user
    * record.

test/unit/user-store-test.js

@@ -192,6 +192,21 @@ describe('UserStore', () => {
         })
     })
 
+    it('should look up user record by normalized email', () => {
+      const email = 'alice@example.com'
+      const user = { id: 'abc', email: email }
+
+      store.backend.get = sinon.stub().resolves(user)
+
+      return store.findUserByEmail(email)
+        .then(fetchedUser => {
+          expect(fetchedUser).to.equal(user)
+
+          expect(store.backend.get).to.have.been
+            .calledWith('users-by-email', 'alice%40example.com')
+        })
+    })
+
     it('should look up user record via an alias record', () => {
       const aliasId = 'alice.solidtest.space/profile/card#me'
       const aliasKey = 'alice.solidtest.space%2Fprofile%2Fcard%23me'