(defn node-to-string [node]
  (def attributes @[])
  (if (get node :label)
    (array/push attributes
      (string/format "label=\"%s\"" (get node :label))))
  (if (get node :shape)
    (array/push attributes
      (string/format "shape=%s" (get node :shape))))
  (if (get node :color)
    (array/push attributes
      (string/format "fillcolor=\"%s\" style=filled" (get node :color))))
  (string/format "%s [%s];\n"
    (get node :name)
    (string/join attributes ",")))

(defn relation-to-string [graph_type relations]
  (def oper
    (cond
      (= graph_type :graph) "--"
      (= graph_type :digraph) "->"))
  (string/format "%s;\n"
    (string/join relations oper)))

(defn create-graph [graph_type name &named rankdir]
  (def a @{
    :name name
    :type graph_type
    :nodes @[]
    :relations @[]
    :subgraphs @[] })

  (when rankdir
    (set (a :rankdir) rankdir))

  a)

(defn create-subgraph [name &named rankdir]
  (def s @{
    :name name
    :nodes @[]
    :relations @[]})

  (when rankdir
    (set (s :rankdir) rankdir))

  s)

(defn add-node [graph name &named label shape color]
  (def new_node @{:name name})
  (when label
    (set (new_node :label) label))
  (when shape
    (set (new_node :shape) shape))
  (when color
    (set (new_node :color) color))

  (def nodes (get graph :nodes))
  (array/push nodes new_node))

(defn add-relation [graph & rels]
  (def relations (get graph :relations))
  (array/push relations rels))

(defn add-subgraph [graph subgraph]
  (def subgraphs (get graph :subgraphs))
  (array/push subgraphs subgraph))

(defn write-graph [graph filename]
  (def f (file/open filename :w))

  (def name (get graph :name))
  (def graph_type
    (cond
      (= (get graph :type) :graph) "graph"
      (= (get graph :type) :digraph) "digraph"))

  (file/write f (string/format "%s %s {" graph_type name))

  (if
    (or
      (> (length (get graph :nodes)) 0)
      (> (length (get graph :relations)) 0))
    (do
      (file/write f "\n")
      (when (get graph :rankdir)
        (file/write f (string/format "rankdir=%s;\n" (get graph :rankdir))))))

  (var i 0)
  (def nodes (get graph :nodes))
  (print (length nodes))
  (while (< i (length nodes))
    (file/write f (string/format "\t%s" (node-to-string (get nodes i))))
    (set i (+ i 1)))

  (set i 0)
  (def relations (get graph :relations))
  (while (< i (length relations))
    (file/write f (string/format "\t%s" (relation-to-string
                    (get graph :type)
                    (get relations i))))
    (set i (+ i 1)))

  (set i 0)
  (def subgraphs (get graph :subgraphs))
  (while (< i (length subgraphs))
    (def subgraph (get subgraphs i))
    (file/write f (string/format "\tsubgraph %s {\n" (get subgraph :name)))
    (when (get subgraph :rankdir)
      (file/write f (string/format "\t\trankdir=%s;\n" (get subgraph :rankdir))))
    (var j 0)
    (def nodes (get subgraph :nodes))
    (print (length nodes))
    (while (< j (length nodes))
      (file/write f (string/format "\t\t%s" (node-to-string (get nodes j))))
      (set j (+ j 1)))

    (set j 0)
    (def relations (get subgraph :relations))
    (while (< j (length relations))
      (file/write f (string/format "\t\t%s" (relation-to-string
                      (get graph :type)
                      (get relations j))))
      (set j (+ j 1)))
    (file/write f "\t}\n")
    (set i (+ i 1)))

  (file/write f "}")
  (file/flush f)
  (file/close f))