module advent_of_code.tasks.day_9.Star2

// UNFINISHED. Submission was found manually.

open System
open System.IO

let stream = new StreamReader("tasks/day-9/input.txt")

type Point2D =
    struct
        val X: int64
        val Y: int64
        new(s: string) =
            let splitS = s.Split(',') |> Array.Parallel.map int64
            let x, y = splitS[0], splitS[1]
            {
                X = x
                Y = y
            }
        
        new(x: int64, y: int64) =
            {
                X = x
                Y = y
            }
            
        override this.ToString() =
            $"Point2D with x = {this.X} y = {this.Y}"
    end

let getRect(p: Point2D * Point2D) =
    let p1, p2 = p.Deconstruct()
    abs (p1.X - p2.X + (1 |> int64)) * abs (p1.Y - p2.Y + (1 |> int64))

let notSame (p: Point2D * Point2D) =
    let p1, p2 = p.Deconstruct()
    p1.X <> p2.X && p1.Y <> p2.Y

let linesIntersect (l1: Point2D * Point2D) (l2: Point2D * Point2D) =
    let (p1, p2) = l1.Deconstruct()
    let (q1, q2) = l2.Deconstruct()
    if q1.X = q2.X then
        q1.X > min p1.X p2.X && q1.X < max p1.X p2.X && min q1.Y q2.Y < max p1.Y p2.Y && max q1.Y q2.Y > min p1.Y p2.Y
    else
        max q1.X q2.X > min p1.X p2.X && min q1.X q2.X < max p1.X p2.X && q1.Y < max p1.Y p2.Y && q1.Y > min p1.Y p2.Y

let isInPoly (polygon: Point2D list) (p: Point2D * Point2D) =
    let edges = List.pairwise polygon @ [List.last polygon, List.head polygon] |> Array.ofList
    edges |> Array.Parallel.forall (linesIntersect p >> not)

let main =
    let points = stream.ReadToEnd().Split('\n') |> Array.Parallel.map Point2D
    let pointList = points |> List.ofArray
    let allRects = (Array.allPairs points points) |> Array.Parallel.filter notSame |> Array.Parallel.filter (isInPoly pointList)
    allRects |> Array.Parallel.maxBy getRect |> getRect