Booktrade

breed [readers reader]
breed [booksellers bookseller]
breed [manuscripts manuscript]

readers-own [
  book-list
  number-of-books
  money
  curiosity
  my-seller
  ]

booksellers-own [
  my-manuscripts
  min-title-diversity
  preferred-print-run
  price-target
  career-span
  capital
  ]



manuscripts-own [
  my-publisher
  title
  editions
  appeal
  price
  depreciation-rate
  book-age-threshold
  earnings
  expenses
  copies-on-the-shelf
  shelf-time
  viable
  failed-solicitations
  ]

to setup
  ca
 
  ; Booksellers publish and distribute manuscripts. They have a capital of money, and if they slip
  ; into too much debt, they go bankrupt and die.
  set-default-shape booksellers "house"
  create-booksellers initial-booksellers [ 
    set color brown
    set size 3
    set career-span 0
    set min-title-diversity 0
    set preferred-print-run 200 - random 190
    set price-target 0.5 + random-gamma 1 2
    set my-manuscripts nobody
    set capital initial-capital
    setxy random-xcor random-ycor
    ]
   
  ; Readers' behavior is controlled by several variables: color, closed-mindedness, and money. All readers will
  ; seek out books of their own color. If they are curious (that is, not incurious) they will also
  ; look for books of different color. They gain money every tick and use money to buy books.
  set-default-shape readers "circle"
  create-readers number-of-readers [
    set color 55 + random-float 4
    set money 0.5 + random-gamma 1 2
    set book-list []
    set size 1.5
    set curiosity random 100
    set my-seller one-of booksellers
    setxy random-xcor random-ycor
  ]
  
  ; Manuscripts are owned by booksellers. They are "published" by hatching
  ; a number of books that share their variables.
  set-default-shape manuscripts "star"

  reset-ticks
end 

; Go activates readers and booksellers.

to go
  tick
  ask readers [ determine-behavior ]
  ask booksellers [manage-inventory check-accounts]
  if not any? booksellers [ stop ]
  if mean [capital] of booksellers > initial-capital * 2 or mean [career-span] of booksellers > 500 [ create-booksellers 1 [
    set color brown
    set size 3
    set career-span 0
    set preferred-print-run 200 - random 190
    set price-target 0.5 + random-gamma 1 2
    set my-manuscripts nobody
    set capital initial-capital
    setxy random-xcor random-ycor ] 
  ]
end 

to determine-behavior
  set curiosity curiosity + 1
  if my-seller = nobody [ set my-seller one-of booksellers ]
  ifelse curiosity > curiosity-threshold 
    [ buy-books ]
    [ move ]
end 

; Readers move about randomly and carry their books with them.

to move                
  rt random 50
  lt random 50
  fd 0.5
end 
   
; Reader look for books to buy. The decision to purchase a book is based on
; a simple randomization of the books' appeal. 

to buy-books
  if my-seller != nobody [ face my-seller ]
  fd 1
  
  if count booksellers in-radius seller-radius > 0 [
  let temp-list [book-list] of self
  let books-to-buy manuscripts in-radius seller-radius with [ ; creates agentset of nearby books   
    copies-on-the-shelf > 0 and                        ; must be owned by bookseller
    not member? title temp-list and
    (appeal + random-float 1 - random-float 1) >= price and  ; appeal (randomly adjusted) must be higher than price
    price <= [money] of myself                               ; reader must have enough money
    ]
  
  let chosen-book one-of books-to-buy                         ; reader chooses one of the eligible books
  ifelse chosen-book != nobody [
    let chosen-seller [my-publisher] of chosen-book
    set book-list fput [title] of chosen-book book-list
    set number-of-books length book-list
    set curiosity 0
    ask chosen-seller [                             
      set capital capital + [price] of chosen-book ]           ; booksellers account is increased
    ask chosen-book [ 
      set earnings earnings + price 
      set copies-on-the-shelf copies-on-the-shelf - 1 ]  
  ] 
  [ 
    set my-seller one-of booksellers 
    ]
  ]
end 

; Booksellers check their inventory.

to manage-inventory
  set capital capital - overhead
  set career-span career-span + 1
  set min-title-diversity abs capital / 100
  set my-manuscripts manuscripts with [my-publisher = myself]
  ask my-manuscripts [update-mss]
  
  if count my-manuscripts with [viable = true] <= min-title-diversity [ acquire-copy ]
  
  if count my-manuscripts with [copies-on-the-shelf > 0] < min-title-diversity [ print-mss ]
end 
  
; When sitting on the shelf, books lose appeal over time.

to update-mss
  set appeal appeal - depreciation-rate
  if earnings >= expenses [ 
    set viable true 
    set shelf-time 0 
    ]
  if expenses > earnings [
    set viable false
    set shelf-time shelf-time + 1 
    ]
  if shelf-time > book-age-threshold [ 
    ask my-publisher [ set capital capital + ([price] of myself * pulp-rate) ]
    die
    ]
  if failed-solicitations > 5 [ die ]
  if appeal < 0 [ die ]
end 

; Bookseller creates a new title.

to acquire-copy
    hatch-manuscripts 1 [
    set size 1
    set color 25 + random-float 4
    set title random-float 100 ; The title create an identifier that can be inherited by copies
    set viable true
    set appeal 1.5 - random-float 1 
    set my-publisher myself
    set price [price-target] of myself - random-float .5
    set depreciation-rate 0.01 - random-float .009
    set book-age-threshold 700 - random 600
    ]
end 

  
; Manuscripts "hatch" copies of themselves as books. When manuscripts hatch books
; those books retain the original's title, appeal, and price.

to print-mss
  let chosen-manuscript one-of my-manuscripts with [ viable = true ]
  if chosen-manuscript != nobody [
  set capital capital - (fixed-cost + ([price] of chosen-manuscript * (preferred-print-run * per-unit-cost)))
  ask chosen-manuscript 
    [
      set expenses expenses + (fixed-cost + ([price] of chosen-manuscript * ([preferred-print-run] of myself * per-unit-cost)))
      set copies-on-the-shelf copies-on-the-shelf + [preferred-print-run] of myself
      ]
  ]
end 

; Booksellers check to see if they have gone bankrupt.

to check-accounts
  if capital < -200 [ 
    ask my-manuscripts [ die ]
    die 
    ]
end