class Arel::Visitors::Dot

def accept(object, collector)
  visit object
  collector << to_dot
end

def edge(name)
  edge = Edge.new(name, @node_stack.last)
  @edge_stack.push edge
  @edges << edge
  yield
  @edge_stack.pop
end

def initialize
  super()
  @nodes      = []
  @edges      = []
  @node_stack = []
  @edge_stack = []
  @seen       = {}
end

def quote(string)
  string.to_s.gsub('"', '\"')
end

def to_dot
  "digraph \"Arel\" {\nnode [width=0.375,height=0.25,shape=record];\n" +
    @nodes.map { |node|
      label = "<f0>#{node.name}"
      node.fields.each_with_index do |field, i|
        label += "|<f#{i + 1}>#{quote field}"
      end
      "#{node.id} [label=\"#{label}\"];"
    }.join("\n") + "\n" + @edges.map { |edge|
      "#{edge.from.id} -> #{edge.to.id} [label=\"#{edge.name}\"];"
    }.join("\n") + "\n}"
end

def visit(o)
  if node = @seen[o.object_id]
    @edge_stack.last.to = node
    return
  end
  node = Node.new(o.class.name, o.object_id)
  @seen[node.id] = node
  @nodes << node
  with_node node do
    super
  end
end

def visit_ActiveModel_Attribute(o)
  visit_edge(o, "value_before_type_cast")
end

def visit_Arel_Attributes_Attribute(o)
  visit_edge o, "relation"
  visit_edge o, "name"
end

def visit_Arel_Nodes_Binary(o)
  visit_edge o, "left"
  visit_edge o, "right"
end

def visit_Arel_Nodes_BindParam(o)
  visit_edge(o, "value")
end

def visit_Arel_Nodes_Case(o)
  visit_edge(o, "case")
  visit_edge(o, "conditions")
  visit_edge(o, "default")
end

def visit_Arel_Nodes_Casted(o)
  visit_edge o, "value"
  visit_edge o, "attribute"
end

def visit_Arel_Nodes_Comment(o)
  visit_edge(o, "values")
end

def visit_Arel_Nodes_Count(o)
  visit_edge o, "expressions"
  visit_edge o, "distinct"
end

def visit_Arel_Nodes_DeleteStatement(o)
  visit_edge o, "relation"
  visit_edge o, "wheres"
  visit_edge o, "orders"
  visit_edge o, "limit"
  visit_edge o, "offset"
  visit_edge o, "key"
end

def visit_Arel_Nodes_Extract(o)
  visit_edge o, "expressions"
  visit_edge o, "alias"
end

def visit_Arel_Nodes_Function(o)
  visit_edge o, "expressions"
  visit_edge o, "distinct"
  visit_edge o, "alias"
end

def visit_Arel_Nodes_HomogeneousIn(o)
  visit_edge o, "values"
  visit_edge o, "type"
  visit_edge o, "attribute"
end

def visit_Arel_Nodes_InfixOperation(o)
  visit_edge o, "operator"
  visit_edge o, "left"
  visit_edge o, "right"
end

def visit_Arel_Nodes_InsertStatement(o)
  visit_edge o, "relation"
  visit_edge o, "columns"
  visit_edge o, "values"
  visit_edge o, "select"
end

def visit_Arel_Nodes_NamedFunction(o)
  visit_edge o, "name"
  visit_edge o, "expressions"
  visit_edge o, "distinct"
  visit_edge o, "alias"
end

def visit_Arel_Nodes_NamedWindow(o)
  visit_edge o, "partitions"
  visit_edge o, "orders"
  visit_edge o, "framing"
  visit_edge o, "name"
end

def visit_Arel_Nodes_Ordering(o)
  visit_edge o, "expr"
end

def visit_Arel_Nodes_SelectCore(o)
  visit_edge o, "source"
  visit_edge o, "projections"
  visit_edge o, "wheres"
  visit_edge o, "windows"
  visit_edge o, "groups"
  visit_edge o, "comment"
  visit_edge o, "havings"
  visit_edge o, "set_quantifier"
  visit_edge o, "optimizer_hints"
end

def visit_Arel_Nodes_SelectStatement(o)
  visit_edge o, "cores"
  visit_edge o, "limit"
  visit_edge o, "orders"
  visit_edge o, "offset"
  visit_edge o, "lock"
  visit_edge o, "with"
end

def visit_Arel_Nodes_StringJoin(o)
  visit_edge o, "left"
end

def visit_Arel_Nodes_TableAlias(o)
  visit_edge o, "name"
  visit_edge o, "relation"
end

def visit_Arel_Nodes_Unary(o)
  visit_edge o, "expr"
end

def visit_Arel_Nodes_UnaryOperation(o)
  visit_edge o, "operator"
  visit_edge o, "expr"
end

def visit_Arel_Nodes_UpdateStatement(o)
  visit_edge o, "relation"
  visit_edge o, "wheres"
  visit_edge o, "values"
  visit_edge o, "orders"
  visit_edge o, "limit"
  visit_edge o, "offset"
  visit_edge o, "key"
end

def visit_Arel_Nodes_ValuesList(o)
  visit_edge o, "rows"
end

def visit_Arel_Nodes_Window(o)
  visit_edge o, "partitions"
  visit_edge o, "orders"
  visit_edge o, "framing"
end

def visit_Arel_Table(o)
  visit_edge o, "name"
end

def visit_Array(o)
  o.each_with_index do |member, i|
    edge(i) { visit member }
  end
end

def visit_Hash(o)
  o.each_with_index do |pair, i|
    edge("pair_#{i}") { visit pair }
  end
end

def visit_String(o)
  @node_stack.last.fields << o
end

def visit__children(o)
  o.children.each_with_index do |child, i|
    edge(i) { visit child }
  end
end

def visit__no_edges(o)
  # intentionally left blank
end

def visit__regexp(o)
  visit_edge o, "left"
  visit_edge o, "right"
  visit_edge o, "case_sensitive"
end

def visit_edge(o, method)
  edge(method) { visit o.send(method) }
end

def with_node(node)
  if edge = @edge_stack.last
    edge.to = node
  end
  @node_stack.push node
  yield
  @node_stack.pop
end