Fibonacci Web Service
------------------------
this is a project written with play framework 2.4 to demonstrate a simple
fibonacci web service. it lightly touches the following key points of designing
a web service project:

    - scalability  (service interface + impl design)
    - input boundary check / error handling / i18n error messages
    - performance
    - usability (providing several APIs for all kinds of requirement)
    - UI (for easy usage too)
    - audit / statistic
    - test
      * function test
      * performance test
      * integration test

possible enhancement in the future:
    - pagination
    - prevent DOS attack (leverage the implemented audit logging function above)
    - etc.

Prerequisite
============
- requires Java 1.8. To check that you have the latest JDK, please run:
  java -version
  to check java version.

How to Run
============

- change directory to fibonacciWS

- compile with below command, it will take a while, as the process will download dependencies.
  on linux / mac, enter "./activator compile"
  on windows, enter ".\activator.bat compile"

- run test
  on linux / mac, enter "./activator test"
  on windows, enter ".\activator.bat test"

- run application
  on linux / mac, enter "./activator run"
  on windows, enter ".\activator.bat run"

- verify
  visit "http://localhost:9000/fibonacci/number/10" in browser to get "55" back as response

- UI (for usability)
  for easy use, provide a UI page for user to see how the 3 API be used.
  visit "http://localhost:9000"


Design Description
----------------------

Controllers
===========

- FibonacciController.java:
  implement 3 RESTful APIs for fibonacci web service

    1. GET /fibonacci/number/{i}
       get the i-th Fibonacci number

    2. GET /fibonacci/list/{i}
       get a list Fibonacci numbers, from the 0-th to i-th.
       result format as: "[0,1,1,2,3 ...]"

    3. GET /fibonacci/range?start={i}&size={s}
       get specify range of Fibonacci numbers, from the i-th to {i+s}-th.
       result format as:
       "[{"index":5,"value":5},{"index":6,"value":8},{"index":7,"value":13}]"

Services
===========

- Fibonacci.java:
  interface to define fibonacci service. allow different implementaion for
  scalability consideration

- FibonacciMapImpl.java
  use HashMap as cache to implement Fibonacci interface to boost performance.
  also provide an option to decide if pre-compute the sequence and fill the cache.
  seen from log, every request took only about 10ms.

- FibonacciPair.java
  for supporting return a range of Fibonacci numbers.


Filters
=======

- utils.LoggingFilter.java
  logging time spent of every request, could be used for:
    * identify time-consuming requests
    * statistics for APIs called
    * audit for error requests and find where they are from

   log format as follow:
   [info] - application - GET /fibonacci/list/10 from 0:0:0:0:0:0:0:1 start at 2016-04-09 10:13:35.275 took 11ms and returned 200
   [info] - application - GET /fibonacci/list/1000 from 0:0:0:0:0:0:0:1 start at 2016-04-09 10:13:58.362 took 10ms and returned 200
   [info] - application - GET /fibonacci/range?start=10000&size=3 from 0:0:0:0:0:0:0:1 start at 2016-04-09 10:28:25.598 took 13ms and returned 200


Exceptions and i18n Messages
========

- messages / messages.cn
  if user input is not a number or out of support range, the returned error message  i18n.


UI
========

- views.index.scala.html
- public/javascripts/fibonacci.js
  provide a form to construct fibonacci web service url based on input values. which help user to
  visualize what the APIs look like.