monadic_tracktor

gistfile1.txt

require 'rubygems'

require 'deterministic'
include Deterministic::Prelude::Result

Operator = Class.new
Visitor = Class.new

fetch_operator = Proc.new {|request|
  Operator.new
}

fetch_visitor = Proc.new {|request|
  Success(Visitor.new)
  # Failure("No such visitor")
}

start_engagement = Proc.new {|request|
  puts "Starting engagement"
  Success(request)
  # Failure("bad engagement")
}

render_response = Proc.new {|request|
  operator = request.fetch(:operator)
  visitor = request.fetch(:visitor)
  {message: "#{operator.class.name} ##{operator.object_id} started engagement with #{visitor.class.name} ##{visitor.object_id}"}
}

store_operator = Proc.new {|request|
  puts "Storing operator"
}

notify_participants = Proc.new {|request|
  puts "Notifying participants"
}

def Merge(key, fn)
  Proc.new {|request|
    fn.call(request)
      .map {|result| Success(request.merge(key => result)) }
  }
end

def OnSuccess(block)
  Proc.new {|request|
    block.call(request)
    Success(request)
  }
end

def Pure(block)
  Proc.new {|request|
    Success(block.call(request))
  }
end

def Chain(*steps)
  Proc.new {|request|
    steps.reduce(Success(request)) {|acc, step| acc >> step }
  }
end

start_engagement = Chain(
  Merge(:operator, Pure(fetch_operator)),
  Merge(:visitor, fetch_visitor),
  start_engagement,
  OnSuccess(notify_participants),
  OnSuccess(store_operator),
  Pure(render_response)
)

tracktor = Proc.new {
  # Very similar to current substation solution
  request = {operator_id: 5, visitor_id: 6}
  response = start_engagement.call(request)
  puts response.inspect
}
tracktor.call