Class: Nanoc::Core::ItemRepSelector::ItemRepPriorityQueue

Inherits:
Object
  • Object
show all
Defined in:
lib/nanoc/core/item_rep_selector.rb

Overview

A priority queue that tracks dependencies and can detect circular dependencies.

Instance Method Summary collapse

Constructor Details

#initialize(outdated_reps:, reps:, dependency_store:) ⇒ ItemRepPriorityQueue

Returns a new instance of ItemRepPriorityQueue.



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# File 'lib/nanoc/core/item_rep_selector.rb', line 16

def initialize(outdated_reps:, reps:, dependency_store:)
  @reps = reps
  @dependency_store = dependency_store

  # Prio A: most important; prio C: least important.
  @prio_a = nil
  @prio_b = outdated_reps.dup
  @prio_c = []

  # List of reps that we’ve already seen. Reps from `reps` will end up
  # in here. Reps can end up in here even *before* they come from
  # `reps`, when they are part of a dependency.
  @seen = Set.new

  # List of reps that have already been completed (yielded followed by
  # `#mark_ok`).
  @completed = Set.new

  # Record (hard) dependencies. Used for detecting cycles.
  @dependencies = Hash.new { |hash, key| hash[key] = Set.new }
end

Instance Method Details

#mark_failed(needed_rep:) ⇒ Object 



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# File 'lib/nanoc/core/item_rep_selector.rb', line 67

def mark_failed(needed_rep:)
  record_dependency(needed_rep)

  # `@this` depends on `needed_rep`, so `needed_rep` has to be compiled
  # first. Thus, move `@this` into priority C, and `needed_rep` into
  # priority A.

  # Put `@this` (item rep that needs `needed_rep` to be compiled first)
  # into priority C (lowest prio).
  @prio_c.push(@this) unless @prio_c.include?(@this)

  # Put `needed_rep` (item rep that needs to be compiled first, before
  # `@this`) into priority A (highest prio).
  @prio_a = needed_rep

  # Remember that we’ve prioritised `needed_rep`. This particular
  # element will come from @prio_b at some point in the future, so we’ll
  # have to skip it then.
  @seen << needed_rep

  # Add everything else that `@this` depends on to the queue. It is OK
  # if there are duplicates; `#next` will filter them out.
  @dependency_store.objects_causing_outdatedness_of(@this.item).each do |obj|
    if obj.is_a?(Nanoc::Core::Item)
      item = obj

      @reps[item].each do |rep|
        @prio_b.unshift(rep)
      end
    end
  end
end

#mark_ok ⇒ Object 



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# File 'lib/nanoc/core/item_rep_selector.rb', line 63

def mark_ok
  @completed << @this
end

#next ⇒ Object 



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# File 'lib/nanoc/core/item_rep_selector.rb', line 38

def next
  # Read prio A
  @this = @prio_a
  if @this
    @prio_a = nil
    return @this
  end

  # Read prio B
  @this = @prio_b.shift
  @this = @prio_b.shift while @seen.include?(@this) || @completed.include?(@this)
  if @this
    return @this
  end

  # Read prio C
  @this = @prio_c.pop
  @this = @prio_c.pop while @completed.include?(@this)
  if @this
    return @this
  end

  nil
end