globals
[ ;; for farm color assignments
  new-color ;; the last color provided by the next-color utility
  new-color-inc ;; the direction (plus or minus) to shift the shade
  new-color-base ;; the shade of gray that is the base color for the current color series
  stop?
]


patches-own
[ farm-id
]


breed [ farms farm ]

farms-own
[ farm-root
  farm-patches
  farm-size
]

to start-up
  setup-farms
end 

to reset
   ;; (for this model to work with NetLogo's new plotting features,
  ;; __clear-all-and-reset-ticks should be replaced with clear-all at
  ;; the beginning of your setup procedure and reset-ticks at the end
  ;; of the procedure.)
  ;; sanity check on mean-farm-size
  if desired-mean-farm-size < min-farm-size and seek-mean-farm-size?
  [ user-message (word "The desired mean farm size can't be less than the minimum farm size,\n"
    "or the desired mean can never be reached!\n\n"
                          "Please change either the minimum farm size or the desired mean farm size."
    )
    stop
  ]
  clear-all
  set stop? false
  reset-ticks
end 

to go
end 

to setup-farms
  reset
  ;; create the initial farm
  ask patch min-pxcor min-pycor
  [ sprout-farms 1
    [ set farm-size world-width
       initialize-farm
    ]
  ]
  while [ stop? != true ]
  [ build-farm
    tick
  ]
  histogram-farm-size
end 

to build-farm
  ;; first, enforce MAX-FARM-SIZE, split any farms over the max size.
   ;; using ONE-OF just to slow things down in demo!
   ;; --remove for production model
   ( ifelse
    ( any? large-farms )
    [ ask one-of large-farms [ split-farm ] ]
    ( seek-mean-farm-size?)
    [ ifelse ( mean [ farm-size ] of farms > desired-mean-farm-size and any? splittable-farms )
      [ ask one-of splittable-farms [ split-farm ] ]
      [ set stop? true ]
    ]
    [ ;; otherwise
      ;; enforce MIN-FARM-COUNT
      ;; split randomly, until at least enough farms
      ifelse ( count farms < desired-min-farm-count and any? splittable-farms )
      [ ask one-of splittable-farms [ split-farm ]
      ]
      [ set stop? true ]
    ]
   )
end 

to position-farm
   let scale farm-size / 2
   set size scale
   setxy ( [ pxcor ] of farm-root + scale )
         ( [ pycor ] of farm-root + scale )
end 

to highlight-borders
   ask farm-patches with [ any? neighbors4 with [ farm-id != [ farm-id ] of myself ] ]
   [ set pcolor [ color + 3 ] of farm-id ]
end 

to-report large-farms
   report farms with [ farm-size > max-farm-size ]
end 

to-report splittable-farms
   report (farms with [ farm-size > min-farm-size ] )
end 

to split-farm
   ;; do not even try to split if this farm is only 1 unit wide.
   if farm-size <= 1 [ stop ]

   ;; OK, split!
   let xx 0
   let yy 0
   let new-size farm-size / 2
   ;; create new farm-roots relative to current farm root
   ;; (do this relative to farm-root so that farm turtle's location is coupled to
   ;; determinig patches for splitting, etc)
   let new-farm-roots [ patches at-points map [ ?1 -> (list (first ?1 * new-size) (last ?1 * new-size) ) ] [ [ 0 0 ] [ 0 1 ] [ 1 1 ] [ 1 0 ] ] ] of farm-root
   ask new-farm-roots
   [ sprout-farms 1
     [ set farm-size new-size
       initialize-farm
     ]
   ]
   ;; this farm is removed
   die
end 

to initialize-farm
    ;; store ID of this patch,
    ;; so we can use farm-root to id the lower-left corner of farm
    ;; letting us put farm turtle anywhere, if we =hoose.
    set farm-root patch-here
    set farm-patches patches with [ pxcor >= [ xcor ] of myself and pxcor < [ xcor + farm-size] of myself
                            and pycor >= [ ycor ] of myself and pycor < [ ycor + farm-size] of myself
                            ]
    set shape "farm"
    set color next-color
    ask farm-patches [ set pcolor [ color ] of myself set farm-id myself ]

    position-farm
end 

to-report next-color
   ifelse new-color = 0 [ set new-color gray ]
   [ set new-color wrap-color (new-color + 10 ) ]
   report new-color
end 

to-report between [ value minimum maximum ]
   report (minimum <= value and value <= maximum)
end 

to histogram-farm-size
   set-current-plot "by farm size"
   histogram [ log farm-size 2] of farms
end