namespace Common

[<StructuralEquality; StructuralComparison>]
type Vec2 =
    | Vec2 of int * int

    static member inline x(Vec2 (x, _)) = x
    static member inline y(Vec2 (_, y)) = y

    static member zero = Vec2(0, 0)
    static member up = Vec2(0, 1)
    static member right = Vec2(1, 0)
    static member down = Vec2(0, -1)
    static member left = Vec2(-1, 0)

    static member upRight = Vec2(1, 1)
    static member upLeft = Vec2(-1, 1)
    static member downLeft = Vec2(-1, -1)
    static member downRight = Vec2(1, -1)

    static member directionsUp =
        Set [ Vec2.upLeft
              Vec2.up
              Vec2.upRight ]

    static member directionsRight =
        Set [ Vec2.upRight
              Vec2.right
              Vec2.downRight ]

    static member directionsDown =
        Set [ Vec2.downLeft
              Vec2.down
              Vec2.downRight ]

    static member directionsLeft =
        Set [ Vec2.upLeft
              Vec2.left
              Vec2.downLeft ]

    static member directions4 =
        Set [ Vec2.up
              Vec2.right
              Vec2.down
              Vec2.left ]

    static member directions8 =
        Set [ Vec2.up
              Vec2.upRight
              Vec2.right
              Vec2.downRight
              Vec2.down
              Vec2.downLeft
              Vec2.left
              Vec2.upLeft ]

    static member inline private _map f (Vec2 (x, y)) = Vec2(f x, f y)
    static member inline private _combine fn (Vec2 (x1, y1)) (Vec2 (x2, y2)) = Vec2(fn x1 x2, fn y1 y2)

    static member inline (~-)(v) = Vec2._map (~-) v
    static member inline (+)(v1, v2) = Vec2._combine (+) v1 v2
    static member inline (-)(v1, v2) = Vec2._combine (-) v1 v2
    static member inline (*)(v1, k) = Vec2._map ((*) k) v1

    static member inline dot (Vec2 (x1, y1)) (Vec2 (x2, y2)) = x1 * x2 + y1 * y2
    static member inline cross (Vec2 (x1, y1)) (Vec2 (x2, y2)) = x1 * y2 - y1 * x2
    static member inline sign = Vec2._map sign
    static member inline lengthSquared(Vec2 (x, y)) = x * x + y * y
    static member mahattanDist (Vec2 (x1, y1)) (Vec2 (x2, y2)) = abs (x2 - x1) + abs (y2 - y1)
    static member chebyshevDist (Vec2 (x1, y1)) (Vec2 (x2, y2)) = max (abs <| x2 - x1) (abs <| y2 - y1)

    static member inline private _nb d v = Set.map ((+) v) d
    static member neighboursUp = Vec2._nb Vec2.directionsUp
    static member neighboursRight = Vec2._nb Vec2.directionsRight
    static member neighboursDown = Vec2._nb Vec2.directionsDown
    static member neighboursLeft = Vec2._nb Vec2.directionsLeft
    static member neighbours4 = Vec2._nb Vec2.directions4
    static member neighbours8 = Vec2._nb Vec2.directions8

    static member boundingRectangle vs =
        (Seq.reduce (Vec2._combine min) vs, Seq.reduce (Vec2._combine max) vs)

    static member lineBetween(Vec2 (x1, y1), Vec2 (x2, y2)) =
        if x1 = x2 then
            Seq.map (fun y -> Vec2(x1, y)) (seq { min y1 y2 .. max y1 y2 })
        elif y1 = y2 then
            Seq.map (fun x -> Vec2(x, y1)) (seq { min x1 x2 .. max x1 x2 })
        else
            failwith "Points must be in a vertical or horizontal line!"

    static member inMatrix matrix (Vec2 (col, row)) =
        col >= 0
        && col < Array2D.length2 matrix
        && row >= 0
        && row < Array2D.length1 matrix

    static member inline toIndexOf matrix (Vec2 (col, row)) = (Array2D.length2 matrix) * row + col