class Jets::Camelizer

def camelize(value)
  return value if value.is_a?(Integer)
  value = value.to_s.camelize
  special_map[value] || value
end

def camelize_key(k, parent_keys=[])
  k = k.to_s
  if passthrough?(k, parent_keys)
    k # pass through untouch
  elsif parent_keys.last == "EventPattern" # top-level
    k.dasherize
  elsif parent_keys.include?("EventPattern")
    # Any keys at 2nd level under EventPattern will be pascalized
    pascalize(k)
  else
    camelize(k)
  end
end

def pascalize(value)
  new_value = value.camelize
  first_char = new_value[0..0].downcase
  new_value[0] = first_char
  new_value
end

def passthrough?(k, parent_keys)
  # do not transform keys anything under these special keys
  parent_keys.include?("Variables") ||
  parent_keys.include?("ResponseParameters") ||
  parent_keys.include?("Fn::Sub") ||
  k.include?('-') || k.include?('/')
end

def special_map
  {
    "TemplateUrl" => "TemplateURL",
    "Ttl" => "TTL",
    "MaxReceiveCount" => "maxReceiveCount",
    "DeadLetterTargetArn" => "deadLetterTargetArn",
    "DbSubnetGroupDescription" => "DBSubnetGroupDescription",
    "DbSubnetGroupName" => "DBSubnetGroupName",
  }
end

def transform(value, parent_keys=[])
  case value
  when Array
    value.map { |v| transform(v, parent_keys) }
  when Hash
    initializer = value.map do |k, v|
      new_key = camelize_key(k, parent_keys)
      [new_key, transform(v, parent_keys+[new_key])]
    end
    Hash[initializer]
  else
    value # do not transform values
  end
end