Class: Jrf::Stage

Inherits:
Object
  • Object
show all
Defined in:
lib/jrf/stage.rb

Defined Under Namespace

Classes: MapReducer, ReducerToken

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ctx, block, src: nil) ⇒ Stage

Returns a new instance of Stage.



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# File 'lib/jrf/stage.rb', line 25

def initialize(ctx, block, src: nil)
  @ctx = ctx
  @block = block
  @src = src
  @reducers = []
  @cursor = 0
  @template = nil
  @mode = nil # nil=unknown, :reducer, :passthrough
  @map_transforms = {}
end

Instance Attribute Details

#src ⇒ Object (readonly)

Returns the value of attribute src.



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# File 'lib/jrf/stage.rb', line 10

def src
  @src
end

Class Method Details

.resolve_template(template, reducers) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 12

def self.resolve_template(template, reducers)
  if template.is_a?(ReducerToken)
    rows = reducers.fetch(template.index).finish
    rows.length == 1 ? rows.first : rows
  elsif template.is_a?(Array)
    template.map { |v| resolve_template(v, reducers) }
  elsif template.is_a?(Hash)
    template.transform_values { |v| resolve_template(v, reducers) }
  else
    template
  end
end

Instance Method Details

#allocate_group_by(key, &block) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 111

def allocate_group_by(key, &block)
  idx = @cursor
  map_reducer = (@reducers[idx] ||= MapReducer.new(:hash))

  row = @ctx._
  slot = map_reducer.slot(key)
  with_scoped_reducers(slot.reducers) do
    result = block.call(row)
    slot.template ||= result
  end

  @cursor += 1
  ReducerToken.new(idx)
end

#allocate_map(type, collection, &block) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 61

def allocate_map(type, collection, &block)
  idx = @cursor
  @cursor += 1

  # Transformation mode (detected on first call)
  if @map_transforms[idx]
    case type
    when :array then return collection.map(&block)
    when :hash then return collection.transform_values(&block)
    end
  end

  map_reducer = (@reducers[idx] ||= MapReducer.new(type))

  case type
  when :array
    raise TypeError, "map expects Array, got #{collection.class}" unless collection.is_a?(Array)
    collection.each_with_index do |v, i|
      slot = map_reducer.slot(i)
      with_scoped_reducers(slot.reducers) do
        result = block.call(v)
        slot.template ||= result
      end
    end
  when :hash
    raise TypeError, "map_values expects Hash, got #{collection.class}" unless collection.is_a?(Hash)
    collection.each do |k, v|
      slot = map_reducer.slot(k)
      with_scoped_reducers(slot.reducers) do
        result = block.call(v)
        slot.template ||= result
      end
    end
  end

  # Detect transformation: no reducers were allocated in any slot
  if @mode.nil? && map_reducer.slots.values.all? { |s| s.reducers.empty? }
    @map_transforms[idx] = true
    @reducers[idx] = nil
    case type
    when :array
      return map_reducer.slots.sort_by { |k, _| k }.map { |_, s| s.template }
    when :hash
      return map_reducer.slots.transform_values(&:template)
    end
  end

  ReducerToken.new(idx)
end

#allocate_reducer(value, initial:, finish: nil, &step_fn) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 52

def allocate_reducer(value, initial:, finish: nil, &step_fn)
  idx = @cursor
  finish_rows = finish || ->(acc) { [acc] }
  @reducers[idx] ||= Reducers.reduce(initial, finish: finish_rows, &step_fn)
  @reducers[idx].step(value)
  @cursor += 1
  ReducerToken.new(idx)
end

#call(input) ⇒ Object 



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# File 'lib/jrf/stage.rb', line 36

def call(input)
  @ctx.reset(input)
  @cursor = 0
  @ctx.__jrf_current_stage = self
  result = @ctx.instance_eval(&@block)

  if @mode.nil? && @reducers.any?
    @mode = :reducer
    @template = result
  elsif @mode.nil?
    @mode = :passthrough
  end

  (@mode == :reducer) ? Control::DROPPED : result
end

#finish ⇒ Object 



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# File 'lib/jrf/stage.rb', line 126

def finish
  return [] unless @mode == :reducer && @reducers.any?

  if @template.is_a?(ReducerToken)
    @reducers.fetch(@template.index).finish
  else
    [self.class.resolve_template(@template, @reducers)]
  end
end