open System
open System.Collections.Generic

// Pokemon Catch Simulator. Version 1.1
// This program simulates how many Pokeballs it will take to catch a Pokemon.
// In Pokemon, you are able to catch Pokemon you find in the wild and tame them.

// In the game, you simply throw a Pokeball and hope for the best. The Pokemon will enter the ball, shake three times,
// and will display a message saying the Pokemon was caught... if you're lucky.
// The odds of catching a Pokemon increase if the Pokemon's health is low, if it is afflicted with a status condition
// such as sleep, paralysis, burn, etc. The odds of catching a Pokemon also depend on that specific Pokemon's catch rate.
// I am specifically using this calculation here:
// https://bulbapedia.bulbagarden.net/wiki/Catch_rate#Capture_method_.28Generation_III-IV.29

// ----------------------------------------------------------------------------

// BEGIN CITATION: This following code was authored by Tomas Petricek. This code snippet implements the "break" and "continue" keywords in F#.
// Retrieved from http://tomasp.net/blog/imperative-ii-break.aspx/

type ImperativeResult<'T> =
  | ImpValue of 'T
  | ImpJump of int * bool
  | ImpNone

type Imperative<'T> = unit -> ImperativeResult<'T>

type ImperativeBuilder() =
  member x.Combine(a, b) = (fun () ->
    match a() with
    | ImpNone -> b()
    | res -> res)
  member x.Delay(f:unit -> Imperative<_>) = (fun () -> f()())
  member x.Return(v) : Imperative<_> = (fun () -> ImpValue(v))
  member x.Zero() = (fun () -> ImpNone)
  member x.Run<'T>(imp) =
    match imp() with
    | ImpValue(v) -> v
    | ImpJump _ -> failwith "Invalid use of break/continue!"
    | _ when typeof<'T> = typeof<unit> -> Unchecked.defaultof<'T>
    | _ -> failwith "No value has been returend!"


// Add special Combine for loops and implement loops
// Add Bind to enable using of break and continue

type ImperativeBuilder with
  member x.CombineLoop(a, b) = (fun () ->
    match a() with
    | ImpValue(v) -> ImpValue(v)
    | ImpJump(0, false) -> ImpNone
    | ImpJump(0, true)
    | ImpNone -> b()
    | ImpJump(depth, b) -> ImpJump(depth - 1, b))
  member x.For(inp:seq<_>, f) =
    let rec loop(en:IEnumerator<_>) =
      if not(en.MoveNext()) then x.Zero() else
        x.CombineLoop(f(en.Current), x.Delay(fun () -> loop(en)))
    loop(inp.GetEnumerator())
  member x.While(gd, body) =
    let rec loop() =
      if not(gd()) then x.Zero() else
        x.CombineLoop(body, x.Delay(fun () -> loop()))
    loop()
  member x.Bind(v:Imperative<unit>, f : unit -> Imperative<_>) = (fun () ->
    match v() with
    | ImpJump(depth, kind) -> ImpJump(depth, kind)
    | _ -> f()() )

let imperative = new ImperativeBuilder()
let break = (fun () -> ImpJump(0, false))
let continue = (fun () -> ImpJump(0, true))
let breakn(n) = (fun () -> ImpJump(n, false))
let continuen(n) = (fun () -> ImpJump(n, true))

// END CITATION.

// ----------------------------------------------------------------------------


let HPcurrent = 20.0 // The current health of the Pokemon.
let HPmax = 180.0 // The maximum health the Pokemon can have.
let ball = 1.0 // The type of Pokeball to be used (1 = standard Pokeball, 1.5 = Great Ball, 2 = Ultra Ball)
let status = 1.5 // Status affliction of the Pokemon (1 = no affliction, 1.5 = poisoned/burned/paralyzed, 2 = asleep/frozen)
let rate = 3.0 // the catch rate of the Pokemon (a value between 1 and 255)

// Do NOT mess with these:
let mutable counter = 0 // this will be used to keep track of how many balls were used.
let mutable caught = false // Boolean to keep track of whether or not the Pokemon is captured.
let mutable a = (((3.0*HPmax - 2.0*HPcurrent) * rate * ball )/(3.0*HPmax)) * status // The calcuation of the modified catch rate given all the properties above.
let b = Math.Floor (1048560.0 / sqrt (sqrt (16711680.0/a))) // Ball shake probability. It's actually supposed to floor every division and square root, but this will do.
let mutable x = 0.0 // number that will be randomly generated


// Display User-inputted information the program will run with.
printfn "HP of Pokemon: %.0f/%.0f" HPcurrent HPmax
if ball = 1.0 then printfn "Using Poke Ball."
elif ball = 1.5 then printfn "Using Great Ball."
elif ball = 2.0 then printfn "Using Ultra Ball."
if status = 1.0 then printfn "Pokemon has no status affliction."
elif status = 1.5 then printfn "Pokemon is paralyzed/burned/poisoned."
elif status = 2.0 then printfn "Pokemon is asleep/frozen."
printfn "Catch rate of Pokemon: %.0f" rate
printfn "a = %.0f" a
printfn "b = %.0f" b
printfn "Press any key to begin..."

Console.ReadKey() |> ignore

let catch_the_monster() = imperative {
    if HPcurrent <> 0.0 || HPmax <> 0.0 || ball <> 0.0 || status <> 0.0 || rate <> 0.0 then
        if a < 1.0 then // if modified catch rate is less than 1, it is set to 1.
            a <- 1.0
        while not caught do
            let rand = Random() // initialize RNG
            for i in 0 .. 3 do //perform four shake checks
                x <- double (rand.Next(0,65535)) // pick a number between 1-65535
                printfn "Ball number %d / shake number %d / random number %.0f" counter i x
                if i = 0 && x >= b then // first shake check
                    printfn "Oh no! The Pokemon broke free!"
                    counter <- counter + 1
                    do! break
                elif i = 1 && x >= b then // second shake check
                    printfn "Aww! It appeared to be caught!"
                    counter <- counter + 1
                    do! break
                elif i = 2 && x >= b then // third shake check
                    printfn "Aargh! Almost had it!"
                    counter <- counter + 1
                    do! break
                elif i = 3 && x >= b then // fails third shake check
                    printfn "Shoot! It was so close, too!"
                    counter <- counter + 1
                    do! break
                elif i = 3 && x < b then // passes third shake check
                    caught <- true
                    printfn "Gotcha! The Pokemon was caught!"
                    counter <- counter + 1
        printfn "It was caught after %d balls" counter
    else
        printfn "Something doesn't seem right. Check the properties of the Pokemon. Make sure nothing is set to zero." }
catch_the_monster()


Console.ReadKey() |> ignore