app.rb

## Device
# RESTful API example
# - manages single resource called Device /device
# - all results (including error messages) returned as JSON (Accept header)

## requires
require 'sinatra'
require 'json'
require 'time'
require 'pp'

### datamapper requires
require 'data_mapper'
require 'dm-types'
require 'dm-timestamps'
require 'dm-validations'

## model
### helper modules
#### StandardProperties
module StandardProperties
  def self.included(other)
    other.class_eval do
      property :id, other::Serial
      property :created_at, DateTime
      property :updated_at, DateTime
    end
  end
end

#### Validations
module Validations
  def valid_id?(id)
    id && id.to_s =~ /^\d+$/
  end
end

### Device
class Device
  include DataMapper::Resource
  include StandardProperties
  extend Validations

  property :name, String, :required => true
  property :status, String
  property :operatingSystem, String
  property :version, String
end

## set up db
env = ENV["RACK_ENV"]
puts "RACK_ENV: #{env}"
if env.to_s.strip == ""
  abort "Must define RACK_ENV (used for db name)"
end

case env
when "test"
  DataMapper.setup(:default, "sqlite3::memory:")
else
  DataMapper.setup(:default, "sqlite3:#{ENV["RACK_ENV"]}.db")
end

## create schema if necessary
DataMapper.auto_upgrade!

## logger
def logger
  @logger ||= Logger.new(STDOUT)
end

## DeviceResource application
class DeviceResource < Sinatra::Base
  set :methodoverride, true

  ## helpers

  def self.put_or_post(*a, &b)
    put *a, &b
    post *a, &b
  end

  helpers do
    def json_status(code, reason)
      status code
      {
        :status => code,
        :reason => reason
      }.to_json
    end

    def accept_params(params, *fields)
      h = { }
      fields.each do |name|
        h[name] = params[name] if params[name]
      end
      h
    end
  end

  ## GET /devices - return all devices
  get "/devices/?", :provides => :json do
    content_type :json

    if devices = Device.all
      devices.to_json
    else
      json_status 404, "Not found"
    end
  end

  ## GET /device/:id - return device with specified id
  get "/devices/:id", :provides => :json do
    content_type :json

    # check that :id param is an integer
    if Device.valid_id?(params[:id])
      if device = Device.first(:id => params[:id].to_i)
        device.to_json
      else
        json_status 404, "Not found"
      end
    else
      # TODO: find better error for this (id not an integer)
      json_status 404, "Not found"
    end
  end

  ## POST /device/ - create new device
  post "/devices/?", :provides => :json do
    content_type :json

    new_params = accept_params(params, :name, :status, :operatingSystem, :version)
    device = Device.new(new_params)
    if device.save
      headers["Location"] = "/devices/#{device.id}"
      # http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.5
      status 201 # Created
      device.to_json
    else
      json_status 400, device.errors.to_hash
    end
  end

  ## PUT /device/:id/:status - change a device's status
  put_or_post "/devices/:id/status/:status", :provides => :json do
    content_type :json

    if Device.valid_id?(params[:id])
      if device = Device.first(:id => params[:id].to_i)
        device.status = params[:status]
        if device.save
          device.to_json
        else
          json_status 400, device.errors.to_hash
        end
      else
        json_status 404, "Not found"
      end
    else
      json_status 404, "Not found"
    end
  end

  ## PUT /device/:id - change or create a device
  put "/devices/:id", :provides => :json do
    content_type :json

    new_params = accept_params(params, :name, :status, :operatingSystem, :version)

    if Device.valid_id?(params[:id])
      if device = Device.first_or_create(:id => params[:id].to_i)
        device.attributes = device.attributes.merge(new_params)
        if device.save
          device.to_json
        else
          json_status 400, device.errors.to_hash
        end
      else
        json_status 404, "Not found"
      end
    else
      json_status 404, "Not found"
    end
  end

  ## DELETE /device/:id - delete a specific device
  delete "/devices/:id/?", :provides => :json do
    content_type :json

    if device = Device.first(:id => params[:id].to_i)
      device.destroy!
      # http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.7
      status 204 # No content
    else
      # http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2
      # Note: section 9.1.2 states:
      #   Methods can also have the property of "idempotence" in that
      #   (aside from error or expiration issues) the side-effects of
      #   N > 0 identical requests is the same as for a single
      #   request.
      # i.e that the /side-effects/ are idempotent, not that the
      # result of the /request/ is idempotent, so I think it's correct
      # to return a 404 here.
      json_status 404, "Not found"
    end
  end

  ## misc handlers: error, not_found, etc.
  get "*" do
    status 404
  end

  put_or_post "*" do
    status 404
  end

  delete "*" do
    status 404
  end

  not_found do
    json_status 404, "Not found"
  end

  error do
    json_status 500, env['sinatra.error'].message
  end

end