/// m06 view: the picture is plain data (a list of shapes); drawing it is somebody else's job (m07).
module Snake.View

open Snake.Model

/// A thing to draw.
type Shape =
    | Rect of x: int * y: int * w: int * h: int * color: string
    | Text of x: int * y: int * text: string * color: string * size: int * align: string

/// A picture: shapes drawn in order.
type Scene = Shape list

let CELL = 20

let private text x y str size align = Text(x, y, str, "#ffffff", size, align)

// One cell, inset by 1px so neighbouring segments show a gap.
let private cell (p: Point) color =
    Rect(p.X * CELL + 1, p.Y * CELL + 1, CELL - 2, CELL - 2, color)

let private overlay (state: GameState) : Scene =
    let cx = state.Width * CELL / 2
    let cy = state.Height * CELL / 2
    let banner title hint = [ text cx cy title 32 "center"; text cx (cy + 30) hint 16 "center" ]

    match state.Status with
    | Paused -> banner "Paused" "Press Space to resume"
    | GameOver -> banner "Game Over" "Press R to restart"
    | Won -> banner "You Win!" "Press R to restart"
    | Playing -> []

let view (state: GameState) : Scene =
    [ Rect(0, 0, state.Width * CELL, state.Height * CELL, "#111111") ]
    @ (state.Apple |> Option.map (fun a -> cell a "#e53935") |> Option.toList)
    @ (state.Snake |> List.mapi (fun i p -> cell p (if i = 0 then "#7cb342" else "#43a047")))
    @ [ text 6 18 $"Score: {state.Score}" 16 "left" ]
    @ overlay state