Class: StateMate::StateSet

Inherits:
Object
  • Object
show all
Defined in:
lib/state_mate/state_set.rb

Overview

Definitions

Defined Under Namespace

Classes: State

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ StateSet

from_spec



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# File 'lib/state_mate/state_set.rb', line 178

def initialize
  @spec = nil
  @states = []
  @read_values = {}
  @states_to_change = []
  @new_values = []
  @written_states = []
  @write_error = nil
  # map of states to errors raised when trying to rollback
  @rollback_errors = {}
  # report of changes made
  @changes = {}
end

Instance Attribute Details

#changes ⇒ Object (readonly)

Returns the value of attribute changes.



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# File 'lib/state_mate/state_set.rb', line 32

def changes
  @changes
end

#new_values ⇒ Object (readonly)

Returns the value of attribute new_values.



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# File 'lib/state_mate/state_set.rb', line 32

def new_values
  @new_values
end

#read_values ⇒ Object (readonly)

Returns the value of attribute read_values.



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# File 'lib/state_mate/state_set.rb', line 32

def read_values
  @read_values
end

#rollback_errors ⇒ Object (readonly)

Returns the value of attribute rollback_errors.



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# File 'lib/state_mate/state_set.rb', line 32

def rollback_errors
  @rollback_errors
end

#spec ⇒ Object

Returns the value of attribute spec.



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# File 'lib/state_mate/state_set.rb', line 31

def spec
  @spec
end

#states ⇒ Object (readonly)

Returns the value of attribute states.



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# File 'lib/state_mate/state_set.rb', line 32

def states
  @states
end

#states_to_change ⇒ Object (readonly)

Returns the value of attribute states_to_change.



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# File 'lib/state_mate/state_set.rb', line 32

def states_to_change
  @states_to_change
end

#write_error ⇒ Object (readonly)

Returns the value of attribute write_error.



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# File 'lib/state_mate/state_set.rb', line 32

def write_error
  @write_error
end

#written_states ⇒ Object (readonly)

Returns the value of attribute written_states.



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# File 'lib/state_mate/state_set.rb', line 32

def written_states
  @written_states
end

Class Method Details

.from_spec(spec) ⇒ Object 



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# File 'lib/state_mate/state_set.rb', line 48

def self.from_spec spec
  state_set = self.new
  state_set.spec = spec

  unless spec.is_a? Hash
    raise StateMate::Error::TypeError.new spec,
      "spec must be a Hash of adapter names to states"
  end

  spec.each do |adapter_name, states|
    adapter = StateMate::Adapters.get adapter_name

    states = case states
    when Hash
      [states]
    when Array
      states
    else
      raise StateMate::Error::TypeError.new states, <<-BLOCK.unblock
        each value of the spec needs to be a single state hash or an
        array or state
      BLOCK
    end

    states.each do |state|
      unless spec.is_a? Hash
        raise StateMate::Error::TypeError.new state,
          "each state needs to be a Hash"
      end

      key = nil
      directives = []
      type_name = nil
      unset_when_false = false
      
      # the :unset_when option can be provided to change the directive to
      # :unset when the option's value is true.
      # 
      # this is useful for things that should simply unset the key when
      # turned off instead of setting it to false or something.
      # 
      unset_when = nil
      
      options = state['options'] || {}
      
      unless options.is_a? Hash
        raise TypeError.new binding.erb <<-END
          options must be a hash, found <%= options.class %>:
          
          <%= options.inspect %>
          
          state:
          
          <%= state.inspect %>
          
        END
      end
      
      state.each do |k, v|
        # normalize to symbols
        k = k.to_sym if k.is_a? String
        
        if k == :key
          key = v
        elsif k == :options
          # pass, dealt with above
        elsif StateMate::DIRECTIVES.include? k
          directives << [k, v]
        elsif k == :type
          type_name = v
        elsif k == :unset_when_false
          unset_when_false = v
        elsif k == :unset_when
          unset_when = StateMate.cast 'bool', v
        else
          # any other keys are set as options
          # this is a little convenience feature that avoids having to
          # nest inside an `options` key unless your option conflicts
          # with 'key' or a directive.
          #
          # check for conflicts
          if options.key? k
            raise ArgumentError.new binding.erb <<-END
              top-level state key #{ k.inspect } was also provided in the
              options.
              
              state:
              
              <%= state.inspect %>
              
            END
          end
          
          options[k] = v
        end
      end

      directive, value = case directives.length
      when 0
        raise "no directive found in #{ state.inspect }"
      when 1
        directives.first
      else
        raise "multiple directives found in #{ state.inspect }"
      end
      
      # handle :unset_when_false option, which changes the operation to
      # an unset when the *directive value* is explicitly false
      if  unset_when_false &&
          (value === false || ['False', 'false'].include?(value))
        directive = :unset
        value = nil
      
      # handle :unset_when, which also changes the operation to :unset
      # when the option's value is true.
      elsif unset_when
        directive = :unset
        value = nil
        
      elsif type_name
        value = StateMate.cast type_name, value
      end

      state_set.add adapter, key, directive, value, options
    end # state.each
  end # states.each

  state_set
end

Instance Method Details

#add(adapter, key, directive, value, options = {}) ⇒ Object 



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# File 'lib/state_mate/state_set.rb', line 192

def add adapter, key, directive, value, options = {}
  @states << State.new(adapter, key, directive, value, options)
end

#execute ⇒ Object 



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# File 'lib/state_mate/state_set.rb', line 196

def execute
  # find out what needs to be changed
  @states.each do |state|
    # read the current value
    read_value = state.adapter.read state.key, state.options

    # store it for use in the actual change
    @read_values[state] = read_value

    # the test method is the directive with a '?' appended,
    # like `set?` or `array_contains?`
    test_method = StateMate.method "#{ state.directive }?"

    # find out if the state is in sync
    in_sync = test_method.call  state.key,
                                read_value,
                                state.value,
                                state.adapter,
                                state.options

    # add to the list of changes to be made for states that are
    # out of sync
    @states_to_change << state unless in_sync
  end

  # if everything is in sync, no changes need to be attempted
  # reutrn the empty hash of changes
  return @changes if @states_to_change.empty?

  # do the change to each in-memory value
  # this will raise an excption if the operation can't be done for
  # some reason
  states_to_change.each do |state|
    sync_method = StateMate.method state.directive
    # we want to catch any error and report it
    begin
      new_value = sync_method.call  state.key,
                                    @read_values[state],
                                    state.value,
                                    state.options
    rescue Exception => e
      @new_value_error = e
      raise StateMate::Error::ValueSyncError.new binding.erb <<-BLOCK
        an error occured when changing a values:

        <%= @new_value_error.format %>

        no changes were attempted to the system, so there is no rollback
        necessary.
      BLOCK
    end
    # change successful, store the new value along-side the state
    # for use in the next block
    @new_values << [state, new_value]
  end

  new_values.each do |state, new_value|
    begin
      state.adapter.write state.key, new_value, state.options
    rescue Exception => e
      @write_error = e
      rollback
      raise StateMate::Error::WriteError.new binding.erb <<-BLOCK
        an error occured when writing new state values:

        <%= @write_error.format %>

        <% if @written_states.empty? %>
          the error occured on the first write, so no values were rolled
          back.

        <% else %>
          <% if @rollback_errors.empty? %>
            all values were sucessfully rolled back:

          <% else %>
            some values failed to rollback:

          <% end %>

          <% @written_states.each do |state| %>
            <% if @rollback_errors[state] %>
              <% state.key %>: <% @rollback_errors[state].format.indent(8) %>
            <% else %>
              <%= state.key %>: rolled back.
            <% end %>
          <% end %>
        <% end %>
        BLOCK
    else
      @written_states << state
    end # begin / rescue / else
  end # new_values.each

  # ok, we made it. report the changes
  new_values_hash = Hash[@new_values]
  @written_states.each do |state|
    @changes[[state.adapter.name, state.key]] = [@read_values[state], new_values_hash[state]]
  end
  
  @changes
end