createBinaryContent.elm

-- this is early brainstorm stage. Writing to arraybuffers is a mutation and we don't have those in Elm atm
-- aside from via Tasks/Cmds. Can we model mutations as something you build up and then "perform" all at once?
-- I'm not sure we could keep all of Elms guarantees (debugging, replay of actions, ...), but at least this API
-- would try to make the mutations happen in a single place? Or maybe performMutations will have to be a Cmd
-- even though it is all native JS code to satisfy the self imposed Elm constraints?

-- new library functions:
createArrayBuffer : Int -> ArrayBufferMutation
toFloat32Array : ArrayBufferMutation -> Float32ArrayMutation -- creates a typed float32 array
float32map : (Float -> Int -> Float) -> Float32ArrayMutation -> Float32ArrayMutation
fromFloat32Array : Float32ArrayMutation -> ArrayBufferMutation -- noop in JS, exists to satisfy the type checker
performMutations : ArrayBufferMutation -> ArrayBuffer


type alias Frequency = Float
type alias Duration = Float
type alias SampleRate = Int

createPureTone : SampleRate -> Frequency -> Duration -> ArrayBuffer
createPureTone sampleRate frequency duration =
  let
    mutations = 
      createArrayBuffer (sampleRate * duration)
      |> toFloat32Array
      |> float32map (\value index -> sin <| index / sampleRate / (2 * pi) * frequency) -- I'm tired, I hope this makes sense
      |> fromFloat32Array
  in
    performMutations mutations