module Chart.Model exposing
  ( Chart
  , Serie
  , maxScale
  , Vec2
  , View
  , mkView
  , bounds
  )

import List.Extra as List

type alias Chart =
  { keys : List String
  , series : List Serie
  , size : Vec2
  , title : String
  , scaleColor : String
  , formatOrdinate : Float -> String
  , ordinateLines : Int
  }

type alias Serie =
  { values : List Float
  , color : String
  , label : String
  }

maxScale : Chart -> Float
maxScale { keys, series } =
  List.range 0 (List.length keys - 1)
    |> List.map (\i ->
         series
           |> List.map (truncate << Maybe.withDefault 0 << List.getAt i << .values)
           |> List.maximum
           |> Maybe.withDefault 0
       )
    |> List.maximum
    |> Maybe.withDefault 0
    |> upperBound

upperBound : Int -> Float
upperBound n = toFloat (upperBoundInt 0 n)

upperBoundInt : Int -> Int -> Int
upperBoundInt count n =
  if n < 10
    then
      (n + 1) * (10 ^ count)
    else
      upperBoundInt (count + 1) (n // 10)

type alias Vec2 =
  { x : Float
  , y : Float
  }

type alias View =
  { fx : Float -> Float
  , fy : Float -> Float
  }

mkView : Vec2 -> Vec2 -> View
mkView p1 p2 =
  { fx = \x -> p1.x + x * (p2.x - p1.x)
  , fy = \y -> p1.y + y * (p2.y - p1.y)
  }

bounds : View -> (Vec2, Vec2)
bounds { fx, fy } =
  ( { x = fx 0, y = fy 0 }
  , { x = fx 1, y = fy 1 }
  )