Class: Janeway::Interpreters::DescendantSegmentInterpreter

Inherits:
Base
  • Object
show all
Defined in:
lib/janeway/interpreters/descendant_segment_interpreter.rb

Overview

Find all descendants of the current input that match the selector in the DescendantSegment

Constant Summary

Constants inherited from Base

Base::NOTHING

Instance Attribute Summary

Attributes inherited from Base

#next, #node

Instance Method Summary collapse

Methods inherited from Base

#as_json, #initialize, #selector, #to_s, #type

Constructor Details

This class inherits a constructor from Janeway::Interpreters::Base

Instance Method Details

#interpret(input, parent, root, path) ⇒ Array<AST::Expression>

Find all descendants of the current input that match the selector in the DescendantSegment

Parameters:

  • input (Array, Hash) —

    the results of processing so far

  • parent (Array, Hash) —

    parent of the input object

  • root (Array, Hash) —

    the entire input

  • path (Array<String>) —

    elements of normalized path to the current input

Returns:



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# File 'lib/janeway/interpreters/descendant_segment_interpreter.rb', line 18

def interpret(input, parent, root, path)
  visit(input, parent, path) do |node, parent_of_node, sub_path|
    @next.interpret(node, parent_of_node, root, sub_path)
  end
end

#visit(input, parent, path) ⇒ Object

Visit all descendants of input and concatenate the results of block at each node. Iterative depth-first pre-order — a recursive implementation would risk SystemStackError on deep JSON and allocated an array-per-node plus a flatten pass.

Parameters:

  • input (Array, Hash) —

    the results of processing so far

  • parent (Array, Hash) —

    parent of the input object

  • path (Array<String>) —

    elements of normalized path to the current input



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# File 'lib/janeway/interpreters/descendant_segment_interpreter.rb', line 32

def visit(input, parent, path)
  results = []
  stack = [[input, parent, path]]
  until stack.empty?
    node, node_parent, node_path = stack.pop
    results.concat(yield(node, node_parent, node_path))

    case node
    when Array
      # Push in reverse so the leftmost child is popped first (pre-order).
      i = node.size - 1
      while i >= 0
        stack.push([node[i], node, node_path + [i]])
        i -= 1
      end
    when Hash
      # Iterate to an array once so we can walk it in reverse.
      pairs = node.to_a
      i = pairs.size - 1
      while i >= 0
        k, v = pairs[i]
        stack.push([v, node, node_path + [k]])
        i -= 1
      end
    end
    # Basic (non-container) types have no descendants — nothing to push.
  end
  results
end