Fish Schooling For Predator Avoidance

breed [ prey a-prey ]
breed [ predators predator ]

prey-own [
  schoolmates  ;; agentset of nearby prey fish
  nearest-neighbor  ;; closest one of schoolmates
  speed ;; distance to travel on tick
]

predators-own [
  prey-in-vision ;; prey within vision radius
  nearest-prey ;; shortest distance prey
  prey-in-front  ;; prey within 30 degree vision cone (used to determine bursting)
  target  ;; nearest prey within a 30 degree vision cone
  speed ;; distance to travel on tick
  burst-energy  ;; energy for predators charging at burst speed, negative if recharging
  bursting?  ;; boolean of whether or not predator is bursting towards prey
]

to setup
  ca
  ask patches [ set pcolor sky + 1 ]

  create-prey prey-population [
    set color blue
    set shape "fish"
    rt random 360
    fd (random 5) + 1 ;; distribute randomly in a cluster
    facexy 0 15
    set speed 1
  ]

  create-predators predator-population [
    set color white
    set shape "fish"
    set size 2
    setxy random-xcor random-ycor ;; distribute fully randomly
    set speed 1.6
    set burst-energy predator-burst-energy
  ]

  reset-ticks
end 

to go
  ask prey [
    school
  ]
  ask predators [
    set prey-in-vision prey in-radius predator-vision

    ifelse any? prey-in-vision
    [ chase-nearest-prey ]  ;; point towards nearest prey
    [ wander ] ;; wander if no prey in sight

    adjust-predator-speed  ;; predator will speed up when making an attack
    scare-prey  ;; prey fleeing starts at predator because of control flow (scare-right, scare-left)
    eat ;; eat prey if within neighbors
  ]
  ask turtles [ fd speed ]

  tick
end 

to eat  ;; predator procedure
  let nearby (turtle-set prey-here prey-on neighbors)
  if any? nearby and burst-energy > 0 [ ;; if there is a catch, stop to eat the fish (cannot eat again until burst recharges)
    set burst-energy 0
    set color black
    ask one-of nearby [
      die
    ]
  ]
end 

to adjust-predator-speed ;; predator procedure
  set prey-in-front prey in-cone predator-vision 90 ;; find prey in front of predator

  ifelse any? prey-in-front and burst-energy > 0 ;; burst if there is a target and have energy
  [ set bursting? true ]
  [ set bursting? false ]

  ifelse bursting?
  [ if speed <= max-predator-speed
    [ set speed speed + .3
      set burst-energy burst-energy - 1 ]
    set color white
  ]
  [ ;; else
    set speed min-predator-speed
    if burst-energy = 0 [ set burst-energy -1 - burst-recharge-time ]  ;; energy set to negative recharge time
    if burst-energy < 0 [ set burst-energy burst-energy + 1 ] ;; recharge burst
    if burst-energy = -1 [ set burst-energy predator-burst-energy ] ;; reset burst energy
  ]
end 

to scare-prey ;; predator procedure
  rt 90
  scare-right  ;; prey on right side will flee right
  rt 180
  scare-left  ;; prey on left side will flee left
  rt 90
end 

to scare-right  ;; prey on right side will flee right
  ask prey in-cone prey-vision 180 [
    if any? predators in-cone prey-vision 270 [
      rt (flee-coefficient / 100) * (subtract-headings (towards myself - 90) heading)
      set speed max-prey-speed
      set color red
    ]
  ]
end 

to scare-left ;; prey on left side will flee left
  ask prey in-cone prey-vision 180 [
    if any? predators in-cone prey-vision 270 [
      rt (flee-coefficient / 100) * (subtract-headings (towards myself + 90) heading)
      set speed max-prey-speed
      set color red
    ]
  ]
end 

to chase-nearest-prey ;; predator procedure
  set nearest-prey min-one-of prey-in-vision [distance myself]
  rt (predator-turn-coefficient / 100) * (subtract-headings (towards nearest-prey) heading)
end 

to wander ;; only predators use
  rt (random 30) - 15
end 

to school  ;; prey procedure
  find-schoolmates
  if any? schoolmates
    [
      find-nearest-neighbor
      if distance nearest-neighbor = 0.000 [ die ] ;; bug patch- removes duplicates to fix crash due to same point netlogo error
      ifelse distance nearest-neighbor < minimum-separation ;; see BOIDS paper for schooling basics (separate, align, cohere)
      [ separate ]
      [ cohere
        align ]
      adjust-prey-speed  ;; adjust speed to stay in a school, can be though of as part of "cohere"
  ]
end 

to adjust-prey-speed ;; prey procedure
  ifelse max [speed] of schoolmates > speed + .1
  [ set speed speed + .1 ] ;; speed up if any schoolmate is moving faster (potentially scared by a predator)
  [ if speed > min-prey-speed
    [ set speed speed - .2
      set color blue] ] ;; else slow down (this eventually slows the school to min-speed, sort of its own emergent phenomena)
end 

to find-schoolmates  ;; prey procedure
  set schoolmates other prey in-radius prey-vision
end 

to find-nearest-neighbor ;; prey procedure
  set nearest-neighbor min-one-of schoolmates [distance myself]
end 

;;; SEPARATE

to separate  ;; turtle procedure
  ifelse member? nearest-neighbor schoolmates in-cone minimum-separation 60 ;; if nearest is in front, slow down, else turn to avoid
  [ if speed > min-prey-speed
    [ set speed speed - .1 ]
  ]
  [ rt (separate-coefficient / 100) * (subtract-headings heading (towards nearest-neighbor)) ;; turns a fraction towards the direction facing directly away from nearest neighbor
  ]
end 

;;; ALIGN

to align  ;; turtle procedure
  rt (align-coefficient / 100) * (subtract-headings average-schoolmate-heading heading) ;; asmpytotic approach to perfect alignment
end 

to-report average-schoolmate-heading  ;; prey procedure, borrowed from orignal flocking model, used for align
  let x-component sum [dx] of schoolmates
  let y-component sum [dy] of schoolmates
  ifelse x-component = 0 and y-component = 0
    [ report heading ]
    [ report atan x-component y-component ]
end 

;;; COHERE

to cohere  ;; prey procedure
  rt (cohere-coefficient / 100) * (subtract-headings average-heading-towards-schoolmates heading) ;; asmptotic approach to center of pack, will never reach because of separate
end 

to-report average-heading-towards-schoolmates  ;; prey procedure, borrowed from original flocking model, used for cohere
  let x-component mean [sin (towards myself + 180)] of schoolmates
  let y-component mean [cos (towards myself + 180)] of schoolmates
  ifelse x-component = 0 and y-component = 0
    [ report heading ]
    [ report atan x-component y-component ]
end