application/vnd.amundsen.maze+xml

app.rb

require 'sinatra'
require 'sequel'
require 'sqlite3'
require 'nokogiri'

DB = Sequel.sqlite

DB.instance_eval do
  create_table :mazes do
    primary_key :id
    String :name
  end
  
  create_table :cells do
    primary_key :id
    foreign_key :maze_id, :mazes
    Integer :position
    FalseClass :north
    FalseClass :south
    FalseClass :east
    FalseClass :west
  end
end

class Maze < Sequel::Model
  one_to_many :cells
end

class Cell < Sequel::Model
  many_to_one :maze
  
  plugin :list, scope: :maze_id
  plugin :boolean_readers
end

maze = Maze.create name: 'five-by-five'
[
  [1,1,1,0],
  [1,1,1,0],
  [1,1,0,0],
  [0,1,0,1],
  [0,1,1,0],
  [1,0,1,0],
  [1,0,0,1],
  [0,0,1,0],
  [1,1,0,0],
  [0,0,1,1],
  [1,0,0,1],
  [0,1,1,0],
  [1,0,1,1],
  [1,0,0,1],
  [0,1,1,0],
  [1,1,1,0],
  [1,0,1,0],
  [1,1,0,0],
  [0,1,0,1],
  [0,0,1,0],
  [1,0,0,1],
  [0,0,0,1],
  [0,0,1,1],
  [1,1,0,1],
  [0,0,1,1] 
].each_with_index do |cell,i| 
  maze.add_cell(
    position: i, 
    north:  cell[0] == 0, 
    west:   cell[1] == 0, 
    south:  cell[2] == 0, 
    east:   cell[3] == 0
  )
end

before do
  content_type 'application/vnd.amundsen.maze+xml'
end

get '/' do
  nokogiri :collection, locals: { mazes: Maze }
end

before %r{^/(?<maze>[^/]+)} do
  @maze = Maze.first(name: params[:maze]) || not_found
end

get '/:maze' do
  nokogiri :item, locals: { maze: @maze }
end

before %r{^/[^/]+/(?<cell>\d+)} do
  pass if params[:cell].to_i == 999
  @cell = @maze.cells_dataset.first(position: params[:cell]) || not_found
end

get '/:maze/999' do
  nokogiri :exit, locals: {
    maze:  @maze,
    total: 0,
    side:  0,
    exit:  0
  }
end

get '/:maze/:cell' do
  total = @maze.cells.count
  side  = Math.sqrt(total).to_i
  
  nokogiri :cell, locals: {
    maze:  @maze,
    cell:  @cell,
    total: total,
    side:  side,
    north: @cell.position - 1,
    west:  @cell.position - side,
    south: @cell.position + 1,
    east:  @cell.position + side,
    exit:  @cell.position == @cell.last_position
  }
end

__END__
@@collection
xml.collection href: url('/') do
  mazes.each do |maze|
    xml.link rel: 'maze', href: url("/#{maze.name}")
  end
end

@@item
xml.item href: url("/#{maze.name}") do
  xml.link rel: 'start', href: url("/#{maze.name}/0")
  xml.link rel: 'collection', href: url('/')
end

@@cell
xml.cell href: url("/#{maze.name}/#{cell.position}"), rel: 'current', total: total, side: side do
  xml.link href: url("/#{maze.name}/#{north}"), rel: 'north' if cell.north?
  xml.link href: url("/#{maze.name}/#{west}"), rel: 'west' if cell.west?
  xml.link href: url("/#{maze.name}/#{south}"), rel: 'south' if cell.south?
  xml.link href: url("/#{maze.name}/#{east}"), rel: 'east' if cell.east?
  
  if exit
    xml.link href: url("/#{maze.name}/999"), rel: 'exit'
  else
    
  end
  
  xml.link href: url('/'), rel: 'collection'
  xml.link href: url("/#{maze.name}"), rel: 'maze'
end

@@exit
xml.cell href: url("/#{maze.name}/999"), rel: 'current', total: total, side: side do
  xml.link href: url("/#{maze.name}/0"), rel: 'start'
  
  xml.link href: url('/'), rel: 'collection'
  xml.link href: url("/#{maze.name}"), rel: 'maze'
end

@@error
xml.error do
  xml.title title
  xml.code code
  xml.message message
end

@@layout
xml.maze version: '1.0' do
  xml << yield
end