caterpiller

;; caterpillars  are  breeds of turtle.
breed [ caterpillars caterpillar ]  ;; 
turtles-own [energy]       ;; caterpillars have energy
patches-own [countdown]

to setup
  clear-all
  ask patches [ set pcolor green ]
  ;; check GRASS? switch.
  ;; if it is true, then grass grows and the caterpillars eat it
  ;; if it false, then the caterpillars don't need to eat
  if grass? [
    ask patches [
      set countdown random grass-regrowth-time ;; initialize grass grow clocks randomly
      set pcolor one-of [green brown]
    ]
  ]
  set-default-shape caterpillars "caterpillar"
  create-caterpillars initial-number-caterpillar  ;; create the caterpillarss, then initialize their variables
  [
        set size 4  ;; easier to see
    set label-color white
    set energy random (10 * caterpillar-gain-from-food)
    setxy random-xcor random-ycor
  ]
    display-labels
  update-plot
end 

to go
  if not any? turtles [ stop ]
  ask caterpillars [
    move
    if grass? [
      set energy energy - 2  ;; deduct energy for caterpillars only if grass? switch is on
      eat-grass
    ]
    reproduce-caterpillars
    death
  ]
    if grass? [ ask patches [ grow-grass ] ]
  tick
  update-plot
  display-labels
end 

to move  ;; turtle procedure
  rt random 50
  lt random 50
  fd 2
end 

to eat-grass  ;; caterpillars procedure
  ;; caterpillars eat grass, turn the patch brown
  if pcolor = green [
    set pcolor brown
    set energy energy + caterpillar-gain-from-food  ;; caterpillars gain energy by eating
  ]
end 

to reproduce-caterpillars  ;; caterpillars procedure
  if random-float 100 < caterpillar-reproduce [  ;; throw "dice" to see if you will reproduce
    set energy (energy / 10)                ;; divide energy between parent and offspring
    hatch 1 [ rt random-float 360 fd 1 ]   ;; hatch an offspring and move it forward 1 step
  ]
end 

to death  ;; turtle procedure
  ;; when energy dips below zero, die
  if energy < 0 [ die ]
end 

to grow-grass  ;; patch procedure
  ;; countdown on brown patches: if reach 0, grow some grass
  if pcolor = brown [
    ifelse countdown <= 0
      [ set pcolor green
        set countdown grass-regrowth-time ]
      [ set countdown countdown - 1 ]
  ]
end 

to update-plot
  set-current-plot "populations"
  set-current-plot-pen "caterpillars"
  plot count caterpillars
  if grass? [
    set-current-plot-pen "grass"
    plot count patches with [pcolor = green]  ;; divide by four to keep it within similar
    ]
end 

to display-labels
  ask turtles [ set label "" ]
  if show-energy? [
     if grass? [ ask caterpillars [ set label round energy ] ]
  ]
end