module December3

open System
open System.IO

let parseLine (line: string) =
    let numbers =
        line.Split([|' '|], StringSplitOptions.RemoveEmptyEntries)
        |> Seq.map Int32.Parse
        |> Seq.take 3
        |> List.ofSeq

    match numbers with
        | [a; b; c] -> Some(a, b, c)
        | _ -> None

let getInput () =
    File.ReadAllLines("input3.txt")
    |> Seq.choose parseLine

let concat (a, b, c) = Seq.concat [a; b; c]

let collectColumns (_as, _bs, _cs) (a, b, c) =
    (a :: _as, b :: _bs, c :: _cs)

let getInput2() =
    File.ReadAllLines("input3.txt")
    |> Seq.choose parseLine
    |> Seq.fold collectColumns ([], [], [])
    |> concat
    |> List.ofSeq

let isTriangle (a, b, c) =
    a + b > c && a + c > b && b + c > a

let getResult () =
    getInput()
    |> Seq.where isTriangle
    |> Seq.length

let rec calculateResult2 sideLengths acc =
    match sideLengths with
        | a :: b :: c :: rest ->
            calculateResult2
                rest
                acc + (if isTriangle (a, b, c) then 1 else 0)
        | _ -> acc

let getResult2() =
    calculateResult2 (getInput2()) 0