Virus CoronaVirus

turtles-own
  [ sick?                ;; if true, the turtle is sick
    infected?						 ;; if true, turtle is infected
    remaining-immunity   ;; how many weeks of immunity the turtle has left
    sick-infected-time   ;; how long, in weeks, the turtle has been infectious
    age                  ;; how many weeks old the turtle is
    sick-around          ;; is there anyone sick around the turtle?
    nearest-sick         ;; the nearest sick turtle around the
    full-life            ;; how much the turtle will live
    get-sick-factor      ;; disease recovery changes with age
    reproduce-number     ;; Maximum number of sons/daughers a turtle may generate
]

globals
  [ %infected            ;; what % of the population is infectious
    %sick								 ;; what % of the population is sick
    %immune              ;; what % of the population is immune
    %dead                ;; Sickness death relative to total death (dead-sick / total-dead)
    dead-sick            ;; How many ppl died by sickness
    dead-total           ;; How many ppl died
    births               ;; How many ppl born
    lifespan             ;; the average lifespan of the turtle population
    chance-reproduce     ;; The probability of a turtle being hatched each simulation tick per turtle in the simulation
    reproduce-factor     ;; Factor of reproduction
    carrying-capacity    ;; the number of turtles that can be in the world at one time
    immunity-duration    ;; how many weeks immunity lasts
]

;; The setup is divided into four procedures

to setup
  clear-all
  setup-constants
  setup-turtles
  update-global-variables
  update-display
  reset-ticks
end 

;; We create a variable number of turtles of which 10 are infectious,
;; and distribute them randomly

to setup-turtles
  create-turtles number-people
    [ setxy random-xcor random-ycor
      set age random lifespan ;; Age is
      set full-life random-normal lifespan (10 * 52)
      while [full-life < age]
        [set age random lifespan]
      set sick-infected-time 0
      set remaining-immunity 0
      set infected? false
      update-size  ;; easier to see
      set-get-sick-factor
      set-reproduce-number
      get-healthy ]
  ask n-of 0 turtles
  [ get-infected ]
end 

to setup-constants
  set lifespan 70 * 52      ;; 70 times 52 weeks = 70 years = 3640 weeks old
  set carrying-capacity 2000
  set reproduce-factor 0.1
  set immunity-duration 9999
end 

to go
  update-chance-reproduce
  if random-float 100 < chance-new-infected
    [create-new-infected]
  if random-float 100 < chance-new-sick
    [create-new-sick]

  ask turtles [
    update-size
    set-get-sick-factor
    get-older
    move
    flee
    if infected? [ infect get-sick ]
    if sick? [ recover-or-die ]
    ifelse sick? [ infect ] [ reproduce ]
  ]
  update-global-variables
  update-display
  tick
end 

to set-get-sick-factor
  set get-sick-factor random-normal ( ((age / 52) ^ 6) * (1.78 * (10 ^ -11)) ) ( 0.5 )
end 

to get-sick ;; turtle procedure
  if sick-infected-time > 2 and random-float 100 < (chance-getting-sick * get-sick-factor);;
  	[	set infected? false
  		set sick? true
      set remaining-immunity 0]
  if sick-infected-time > duration
    [become-immune]
end 

to get-infected ;;
  	set infected? true
    set remaining-immunity 0
end 

to get-healthy ;; turtle procedure
  set sick? false
  set infected? false
  set remaining-immunity 0
  set sick-infected-time 0
end 

to become-immune ;; turtle procedure
  set sick? false
  set infected? false
  set sick-infected-time 0
  set remaining-immunity immunity-duration
end 

to update-chance-reproduce
  if count turtles > 0
    ;;[set chance-reproduce random-normal (100 * (reproduce-factor / count turtles) - (reproduce-factor / (count turtles * 10))) (count turtles / 10 ^ 4)] ;; The most ppl on the simulation, lesser is the intention of reproducing. Needs improvement
  [set chance-reproduce 1]
end 

to set-reproduce-number
  ifelse maximum-sons-by-person > 0
    [ set reproduce-number random (maximum-sons-by-person + 1) ] ;; random command excludes the number eg: random 4 generates 0, 1, 2 or 3. So I summed 1 to the variable.
  [ set reproduce-number 0 ]
end 

to create-new-infected
  create-turtles 1
  [ setxy random-xcor random-ycor
    set age random lifespan
    set full-life random-poisson lifespan
    set sick-infected-time 0
    set remaining-immunity 0
    update-size
    set-reproduce-number
    get-healthy
    get-infected
  ]
end 

to create-new-sick
  create-turtles 1
  [ setxy random-xcor random-ycor
    set age random lifespan
    set full-life random-poisson lifespan
    set sick-infected-time 0
    set remaining-immunity 0
    update-size
    set-reproduce-number
    get-healthy
    get-infected
    get-sick
  ]
end 

to flee
  if flee-from-sick?
  [
    find-sicks
    if any? sick-around
        [find-nearest-sick
          if distance nearest-sick < 2
          [ bk 3 ]]
  ]
end 

to find-sicks  ;; Find group of sick ppl next to agent.
  set sick-around other turtles in-radius 5 with [ sick? ]
end 

to find-nearest-sick ;; People Flee from nearest sick in the simulation
  set nearest-sick min-one-of sick-around [distance myself]
end 


;;Turtle counting variables are advanced.

to get-older ;; turtle procedure
  ;; Turtles die of old age once their age exceeds the
  ;; lifespan (set at 50 years in this model).
  set age age + 1
  if age > full-life
    [ set dead-total dead-total + 1
      die ]
  if immune? [ set remaining-immunity remaining-immunity - 1 ]
  if infected? [ set sick-infected-time sick-infected-time + 1 ]
  if sick? [ set sick-infected-time sick-infected-time + 1 ]
end 

;; Turtles move about at random.

to move ;; turtle procedure
  ifelse sick-can-move?
    [ rt random 100
      lt random 100
      ifelse age < (50 * 52)
        [ fd 1.0 ]
        [ fd 0.5 ]
    ]
    [ rt random 100
      lt random 100
      if sick? = false
        [ifelse age < (50 * 52)
          [ fd 1.0 ]
          [ fd 0.5 ]
  ]]
end 

;; If a turtle is sick, it infects other turtles on the same patch.
;; Immune turtles don't get sick.

to infect ;; turtle procedure
  ask other turtles-here with [ not infected? and not immune? and not sick? ]
    [ if random-float 100 < infectiousness
      [ get-infected ] ]
end 

;; Once the turtle has been sick long enough, it
;; either recovers (and becomes immune) or it dies.

to recover-or-die ;; turtle procedure
  if sick-infected-time > duration               ;; If the turtle has survived past the virus' duration, then
    [ ifelse random-float 100 < chance-recover   ;; either recover or die
      [ become-immune ]
      [ set dead-total dead-total + 1
        set dead-sick dead-sick + 1
        die ] ]
end 

;; If there are less turtles than the carrying-capacity
;; then turtles can reproduce.

to reproduce
  if age > (18 * 52) and age < (55 * 52)
    [ if count turtles < carrying-capacity and random-float 100 < chance-reproduce and reproduce-number > 0
      [ set reproduce-number reproduce-number - 1
        set births births + 1
        hatch 1
        [ set age 1
          set full-life random-normal lifespan (25 * 52)
          set-reproduce-number
          update-size
          set-get-sick-factor
          lt 45 fd 1
          get-healthy ] ]
  ]
end 

to update-size
  set size ((age / lifespan) * 1.5) + 0.5
end 

to update-global-variables
  if count turtles > 0
  [ set %infected ((count turtles with [ infected? ] + count turtles with [sick?]) / count turtles) * 100
    set %immune (count turtles with [ immune? ] / count turtles) * 100
    set %sick (count turtles with [sick?] / count turtles) * 100
    if dead-total > 0
      [ set %dead (dead-sick / dead-total) * number-people ]
  ]
end 

to update-display
  ask turtles
    [ if shape != turtle-shape [ set shape turtle-shape ]
      set color ifelse-value infected? [orange] ifelse-value sick? [ red ] [ ifelse-value immune? [ grey ] [ green ] ]
      if age > (55 * 52)
      [set shape "old"]
  ]
end 

to-report immune?
  report remaining-immunity > 0
end 

to startup
  setup-constants ;; so that carrying-capacity can be used as upper bound of number-people slider
end 


; Copyright 1998 Uri Wilensky.
; See Info tab for full copyright and license.