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# frozen_string_literal: true
module Liquid
class ParseTreeVisitor
def self.for(node, callbacks = Hash.new(proc {}))
if defined?(node.class::ParseTreeVisitor)
node.class::ParseTreeVisitor
else
self
end.new(node, callbacks)
end
def initialize(node, callbacks)
@node = node
@callbacks = callbacks
end
def add_callback_for(*classes, &block)
callback = block
callback = ->(node, _) { yield node } if block.arity.abs == 1
callback = ->(_, _) { yield } if block.arity.zero?
classes.each { |klass| @callbacks[klass] = callback }
self
end
def visit(context = nil)
children.map do |node|
item, new_context = @callbacks[node.class].call(node, context)
[
item,
ParseTreeVisitor.for(node, @callbacks).visit(new_context || context),
]
end
end
protected
def children
@node.respond_to?(:nodelist) ? Array(@node.nodelist) : []
end
end
end
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