require 'rubygems'
  require 'sinatra'

  DATAFILE = "hostdata.yml"
  def get_data
    if File.readable?(DATAFILE)
      @hosts, @errors = YAML.load_file(DATAFILE)
    else
      @hosts = {}
      @errors = []
    end
  end
  def save_data
    File.open(DATAFILE,"w") do |out|
      YAML.dump([@hosts,@errors], out)
    end
  end
  
  get '/' do
    get_data
    erb <<-END
      <p>Hosts so far:</p>
      <ul>
       <% @hosts.keys.sort.each do |mac|
             host = @hosts[mac] %>
         <li><%=mac%> -> name=<%=host[:name]%> ip=<%=host[:ip]%> updated at <%=host[:time]%></li>
       <% end %>
      </ul>
      <hr/>
      <p>Errors logged:</p>
      <ul>
      <% @errors.each do |line| %>
         <li><%=line%></li>
      <% end %>
      </ul>
      <hr/>
      <form action='/' method="POST">
        mac:<input type="text" name="mac" />
        name:<input type="text" name="name" />
        ip:<input type="text" name="ip" />
        <input type="submit" value="Submit a host" />
      </form>
    END
  end

  get '/hosts' do
    headers 'Content-Type' => 'text/plain'
    get_data
    resp = "\# Host file data created by fakedns.rb\n"
    @hosts.keys.sort.each do |mac|
       host = @hosts[mac]
       resp += "#{host[:ip]} #{host[:name]}\n"
    end
    resp
  end
  
  post '/' do
    get_data
    mac = params[:mac].strip
    name = params[:name].strip
    ip = params[:ip].strip
    @new_errors = []
    if mac.size == 0 || name.size == 0 || ip.size == 0
      errormsg = "#{Time.now}: Error adding host '#{name}' with ip '#{ip}' from mac address '#{mac}' - all parameters must be supplied"
      @new_errors << errormsg
      @errors << errormsg
    end
    @hosts.each do |other_mac, other_host|
      if other_host[:name] == name && other_mac != mac
        errormsg = "#{Time.now}: Error adding host '#{name}' with ip '#{ip}' from mac address '#{mac}' - collides with host '#{other_host[:name]}' with ip '#{other_host[:ip]}' from mac address '#{other_mac}'"
        @new_errors << errormsg
        @errors << errormsg
      end
    end
    if @new_errors.size == 0
      @hosts[mac] = {:name => name, :ip => ip, :time => Time.now.to_s}
    end
    save_data
    if @new_errors.size > 0
      status 500
      erb <<-END
      <p>Errors occurred:</p>
      <ul>
       <% @new_errors.each do |error| %>
       <li><%=error%></li>
       <% end %>
      </ul>
     END
    else
      'ok - go to <a href="/">main page</a> for results, or <a href="/hosts">/hosts</a> for hosts file snippet.'
    end
  end