Graph

breed [nodes node]
directed-link-breed [edges edge]

globals [
  ; mouse-globals
  mouse-clicked? %mouse-down? %mouse-time
  
  ; edge-creation-globals
  first-node]

to setup
  set %mouse-down? false
end 

; Mouse-Utility
;  Set mouse-clicked to true when the mouse is released
;  Use it within a "forever"-command

to go-mouse
  ifelse mouse-down? [
    set %mouse-down? true
  ] [
    ifelse %mouse-down? = true [
      set mouse-clicked? true
    ] [
      set mouse-clicked? false
    ]
    set %mouse-down? false
  ]
end 

; Create nodes

to node-creation
  go-mouse
  if mouse-clicked? = true [
    let nh false
    ask patch (round mouse-xcor) (round mouse-ycor) [
      ifelse any? nodes-here
        [ set nh true ]
        [ set nh false]
      ifelse nh [ask nodes-on patch (round mouse-xcor) (round mouse-ycor) [die]
      ] [sprout-nodes 1 [setxy mouse-xcor mouse-ycor
                         set shape "dot"
                         show who]
        ]
    ]
  ]
end 

; Create Edges

to edge-creation
  go-mouse
  if mouse-clicked? = true [
    ifelse not is-agent? first-node [
      ; mark first node
      let nh false
      ask patch (round mouse-xcor) (round mouse-ycor) [
        ifelse any? nodes-here [ set nh true ] [ set nh false]
        if nh [set first-node one-of nodes-here]
      ]
    ] [
      ; mark second node
      let nh false
      ask patch (round mouse-xcor) (round mouse-ycor) [
        ifelse any? nodes-here [ set nh true ] [ set nh false]
        if nh [ ask one-of nodes-here [ let edge-exists false ask first-node [set edge-exists out-link-neighbor? myself ]
                                        ifelse edge-exists [ask in-edge-from first-node [die] ]
                                         [create-edge-from first-node]] set first-node false ]
      ]
    ]
  ]
end 

to make-input
  let input []
  let kv-pair []
  let neighs []
  ask nodes [
    set kv-pair []
    set neighs []
    set kv-pair fput who kv-pair
    ask out-edge-neighbors [set neighs fput who neighs]
    set kv-pair lput neighs kv-pair
    set input fput kv-pair input
  ]
  show input
end