# == FieldManager
#
# The FieldManager provides a way of accessing a hash of constants. These are
# useful for storing configuration data seperately from recipes. # Fields are
# typically stored in a Project's <tt>config/fields.yml</tt> file.
#
# Fields can also be queried from the Unix shell using +aifield+, run
# <tt>aifield --help</tt> for details.
class AutomateIt::FieldManager < AutomateIt::Plugin::Manager
  alias_methods :lookup

  # Lookup a field.
  #
  # For example, consider a <tt>field.yml</tt> that contains YAML like:
  #   foo: bar
  #   my_app:
  #     my_key: my_value
  #
  # With the above file, we can query the fields like this:
  #   lookup(:foo) # => "bar"
  #   lookup("foo") # => "bar"
  #   lookup("my_app#my_key") # => "my_value"
  #   lookup("my_app#my_branch") # => "my_value"
  #
  # You can get a reference to the entire hash:
  #   lookup("*")
  #
  # If a field isn't found, a IndexError is raised.
  def lookup(search=nil) dispatch(search) end
end

# == FieldManager::BaseDriver
#
# Base class for all FieldManager drivers.
class AutomateIt::FieldManager::BaseDriver < AutomateIt::Plugin::Driver
end

# == FieldManager::Struct
#
# A FileManager driver that queries a data structure.
class AutomateIt::FieldManager::Struct < AutomateIt::FieldManager::BaseDriver
  depends_on :nothing

  def suitability(method, *args) # :nodoc:
    return 1
  end

  # Options:
  # * :struct -- Hash to use as the fields data structure.
  def setup(opts={})
    super(opts)

    if opts[:struct]
      @struct = opts[:struct]
    else
      @struct ||= {}
    end
  end

  # See FieldManager#lookup
  def lookup(search=nil)
    return @struct if search.nil? or search == "*"
    ref = @struct
    for key in search.to_s.split("#")
      ref = ref[key]
    end
    if ref
      return ref
    else
      raise IndexError.new("can't find value for: #{search}")
    end
  end
end

# == FieldManager::YAML
#
# A FieldManager driver that reads its data structure from a file.
class AutomateIt::FieldManager::YAML < AutomateIt::FieldManager::Struct
  depends_on :nothing

  def suitability(method, *args) # :nodoc:
    return 5
  end

  # Options:
  # * :file -- Filename to read data structure from. Contents will be
  #   parsed with ERB and then handed to YAML.
  def setup(opts={})
    if filename = opts.delete(:file)
      contents = _read(filename)
      binder = interpreter.instance_eval { binding() }
      output = HelpfulERB.new(contents, filename).result(binder)

      opts[:struct] = ::YAML::load(output)
    end
    super(opts)
  end

  def _read(filename)
    return File.read(filename)
  end
  private :_read
end