class Dentaku::PrintVisitor

def initialize(node)
  @output = ''
  node.accept(self)
end

def should_output?(node, precedence, output_on_equal)
  return false unless node.is_a?(Dentaku::AST::Operation)
  target_precedence = node.class.precedence
  target_precedence < precedence || (output_on_equal && target_precedence == precedence)
end

def to_s
  @output
end

def visit_access(node)
  node.structure.accept(self)
  @output << "["
  node.index.accept(self)
  @output << "]"
end

def visit_array(node)
  @output << node.value.to_s
end

def visit_case(node)
  @output << "CASE "
  node.switch.accept(self)
  node.conditions.each { |c| c.accept(self) }
  node.else && node.else.accept(self)
  @output << " END"
end

def visit_case_conditional(node)
  node.when.accept(self)
  node.then.accept(self)
end

def visit_else(node)
  @output << " ELSE "
  node.node.accept(self)
end

def visit_function(node)
  @output << node.name
  @output << "("
  arg_count = node.args.length
  node.args.each_with_index do |a, index|
    a.accept(self)
    @output << ", " unless index >= arg_count - 1
  end
  @output << ")"
end

def visit_identifier(node)
  @output << node.identifier
end

def visit_literal(node)
  @output << node.quoted
end

def visit_negation(node)
  @output << "-"
  @output << "(" unless node.node.is_a? Dentaku::AST::Literal
  node.node.accept(self)
  @output << ")" unless node.node.is_a? Dentaku::AST::Literal
end

def visit_nil(node)
  @output << "NULL"
end

def visit_operand(node, precedence, prefix: "", suffix: "", dir: :none)
  @output << prefix
  @output << "(" if should_output?(node, precedence, dir == :right)
  node.accept(self)
  @output << ")" if should_output?(node, precedence, dir == :right)
  @output << suffix
end

def visit_operation(node)
  if node.left
    visit_operand(node.left, node.class.precedence, suffix: " ", dir: :left)
  end
  @output << node.display_operator
  if node.right
    visit_operand(node.right, node.class.precedence, prefix: " ", dir: :right)
  end
end

def visit_switch(node)
  node.node.accept(self)
end

def visit_then(node)
  @output << " THEN "
  node.node.accept(self)
end

def visit_when(node)
  @output << " WHEN "
  node.node.accept(self)
end