scenic_clock

#
#  Created by Boyd Multerer on August 8, 2018.
#  Copyright © 2018 Kry10 Industries. All rights reserved.
#


defmodule Scenic.Clock.Digital do
  @moduledoc """
  A component that runs an digital clock.

  See the [Components](Scenic.Clock.Components.html#digital_clock/2) module for useage


  """
  use Scenic.Component, has_children: false

  alias Scenic.Graph
  # alias Scenic.Primitive.Style.Theme


  # alias Scenic.Component.Input.Dropdown
  import Scenic.Primitives, only: [ {:text, 2}, {:text, 3} ]

  # import IEx

  # formats setup
  @default_format   "%a %l:%M %p"

  @default_timezone "GMT"

  # theme
  # @default_theme    :dark

  #--------------------------------------------------------
  @doc false
  def verify( nil ), do: {:ok, nil}
  def verify( _ ), do: :invalid_data

  #--------------------------------------------------------
  @doc false
  def init( _, opts ) do
    styles = opts[:styles]

    # get the timezone
    timezone = case  Enum.member?(Timex.timezones(), styles[:timezone]) do
      true -> styles[:timezone]
      false -> Timex.Timezone.local() || @default_timezone
    end

    # get and validate the requested time format
    format =case styles[:format] do
      format when is_bitstring(format) ->
        # doubleck check that is is a valid
        Timex.now(timezone)
        |> Timex.format( format, :strftime )
        |> case do
          {:ok, _} -> format
          _ -> @default_format
        end
      _ -> @default_format
    end

    # set up the requested graph
    graph = Graph.build(styles: styles)
    # |> text("", fill: theme.text, id: :time)
    |> text("", id: :time)

    state = %{
      graph: graph,
      format: format,
      timezone: timezone,
      timer: nil,
      last: nil,
      seconds: !!styles[:seconds]
    }
    # start up the graph
    |> update_time()

    # send a message to self to start the clock a fraction of a second
    # into the future to hopefully line it up closer to when the seconds
    # actually are. Note that I want it to arrive just slightly after
    # the one second mark, which is way better than just slighty before.
    # avoid trunc errors and such that way even if it means the second
    # timer is one millisecond behind the actual time.
    {microseconds,_} = Time.utc_now.microsecond
    Process.send_after(self(), :start_clock, 1001 - trunc(microseconds / 1000) )

    {:ok, state }
  end

  #--------------------------------------------------------
  @doc false
  # should be shortly after the actual one-second mark
  def handle_info( :start_clock, state ) do
    # start the timer on a one-second interval
    {:ok, timer} = :timer.send_interval(1000, :second)

    # update the clock
    state = update_time( state )

    {:noreply, %{state | timer: timer} }
  end

  #--------------------------------------------------------
  def handle_info( :second, state ) do
    {:noreply, update_time( state )}
  end

  #--------------------------------------------------------
  defp squash(string) do
    string
    |> String.trim
    |> String.replace(~r/\s{2,}/, " ")
  end

  #--------------------------------------------------------
  defp update_time( %{
    format: format,
    graph: graph,
    timezone: timezone,
    last: last
  } = state ) do
    {:ok, time} = Timex.now(timezone)
    |> Timex.format( format, :strftime )
    time = squash(time)

    if time != last do
      Graph.modify(graph, :time, &text(&1, time))
      |> push_graph()
    end

    %{state | last: time}
  end


end