main.rb

require 'rubygems'
require 'sinatra'
require 'json'
require 'data_mapper'
require 'dm-migrations'
require 'will_paginate'
require 'will_paginate/collection'
require 'will_paginate/view_helpers'
require 'haml'
require 'active_attr'

# Now using pg locally and on heroku
# First create a unicycle database - you may need to change the local og url
# here or run the app with
# $ DATABASE_URL='postgres://user:pwd@host:port/database' ruby main.rb
database_url = ENV['DATABASE_URL'] || 'postgres://tim@localhost:5432/unicycle'
DataMapper.setup(:default, database_url)

# A model representing a unicode character, maps to a characters table in the database
class Character
  include DataMapper::Resource

  property :id, Serial
  property :code, String
  property :hex, String
  property :ref, String
  property :description, String

  # Helper method to search and return an array of characters
  # paginated usin the will_paginate gem
  def self.paginated_search(params, term)
    per_page = params[:per_page] || 20
    page = params[:page] || 1

    page = page.to_i
    page -= 1
    per_page = per_page.to_i
    offset = per_page * page
    term = term.gsub('#','').upcase

    characters = Character.all

    # apply search term is there is one
    unless term.empty?
      characters = characters.all(:description.like => "%#{term}%") |
                   characters.all(:hex.like => "%#{term}%") |
                   characters.all(:code.like => "%#{term}%")
    end

    # get the current set of characters to display
    characters_on_this_page = characters.all(limit: per_page, offset: offset)

    WillPaginate::Collection.create(page + 1, per_page, characters.count) do |p|
      p.replace characters_on_this_page
    end
  end
end

DataMapper.finalize
DataMapper.auto_upgrade!

# This root url delivers a json-driven page with no server-side view formatting at all
get '/' do
  haml :webapp, format: :html5
  @term = params[:term] || ''
  @characters = Character.paginated_search(params, @term)
  haml :webapp, format: :html5
end

# This url is a web service serving up characters as paginated json
# This is the format of the json returned
# {
#     "characters":
#       [
#         {
#           "code": " ",
#           "id": 1,
#           "hex": "U+0020",
#           "description": "SPACE",
#           "ref": " "
#           },
#           {...}
#       ],
#     "pagination": {
#         "total_entries": 11293,
#         "current_page_number": {
#             "name": "page",
#             "_dc_obj": 1
#         },
#         "total_pages": 565,
#         "previous_page": "",
#         "next_page": "http://unicycle.herokuapp.com/characters.json?page=2&term=",
#         "offset": 0,
#         "current_page": "http://unicycle.herokuapp.com/characters.json?page=1&term="
#     }
# }
get '/characters.json' do
  content_type :json
  @term = params[:term] || ''
  @characters = Character.paginated_search(params, @term)

  pagination = { next_page: url_for_page(@characters.next_page, @term),
                 previous_page: url_for_page(@characters.previous_page, @term),
                 current_page: url_for_page(@characters.current_page, @term),
                 current_page_number: @characters.current_page,
                 offset: @characters.offset,
                 total_entries: @characters.total_entries,
                 total_pages: @characters.total_pages }

  { characters: @characters, pagination: pagination }.to_json
end

# Helper to format urls returned in the pagination json
def url_for_page(page, term)
  if page.nil?
    ''
  else
    "http://#{request.host_with_port}#{request.path_info}?page=#{page}&term=#{term}"
  end
end