defmodule SnapFramework.Engine.Builder do
  @moduledoc """
  ## Overview

  This module is responsible for taking the parsed EEx template and building the graph.
  """

  def build_graph(list, acc \\ %{}) do
    Enum.reduce(list, acc, fn item, acc ->
      case item do
        [type: :graph, opts: opts] -> Scenic.Graph.build(opts)

        [type: :component, module: module, data: data, opts: opts] ->
          children = if opts[:do], do: opts[:do], else: nil
          acc |> module.add_to_graph(data, Keyword.put_new(opts, :children, children))

        [type: :component, module: module, data: data, opts: opts, children: children] ->
          acc |> module.add_to_graph(data, Keyword.put_new(opts, :children, children))

        [type: :primitive, module: module, data: data, opts: opts] ->
          acc |> module.add_to_graph(data, opts)

        [type: :layout, children: children, padding: padding, width: width, height: height, translate: translate] ->
          do_layout(acc, children, padding, width, height, translate).graph

        "\n" -> acc

        list ->
          if is_list(list) do
            build_graph(list, acc)
          else
            acc
          end
      end
    end)
  end

  defp do_layout(%Scenic.Graph{} = graph, children, padding, width, height, {x, y} = translate) do
    layout = %{last_x: x, last_y: y, padding: padding, width: width, height: height, largest_width: 0, largest_height: 0, graph: graph, translate: translate}
    Enum.reduce(children, layout, fn child, layout ->
      case child do
        [type: :component, module: module, data: data, opts: opts] ->
          children = if opts[:do], do: opts[:do], else: nil
          translate_and_render(layout, module, data, Keyword.put_new(opts, :children, children))

        [type: :component, module: module, data: data, opts: opts, children: children] ->

          translate_and_render(layout, module, data, Keyword.put_new(opts, :children, children))

        [type: :primitive, module: _module, data: _data, opts: _opts] ->
          layout

        [type: :layout, children: children, padding: padding, width: width, height: height, translate: translate] ->
          do_layout(layout, children, padding, width, height, translate)

        "\n" -> layout

        list ->
          if is_list(list) do
            do_layout(layout, list, padding, width, height, translate)
          else
            layout
          end
      end
    end)
  end

  defp do_layout(layout, children, padding, width, height, {x, y} = translate) do
    {prev_x, prev_y} = layout.translate
    layout = %{layout | last_x: x + prev_x + layout.padding, last_y: layout.last_y + y + layout.largest_height + layout.padding, padding: padding, width: width, height: height, translate: {x + prev_x, y + prev_y}}
    Enum.reduce(children, layout, fn child, layout ->
      case child do
        [type: :component, module: module, data: data, opts: opts] ->
          children = if opts[:do], do: opts[:do], else: nil
          translate_and_render(layout, module, data, Keyword.put_new(opts, :children, children))

        [type: :component, module: module, data: data, opts: opts, children: children] ->

          translate_and_render(layout, module, data, Keyword.put_new(opts, :children, children))

        [type: :primitive, module: _module, data: _data, opts: _opts] ->
          layout

        [type: :layout, children: children, padding: padding, width: width, height: height, translate: translate] ->
          do_layout(layout, children, padding, width, height, translate)

        "\n" -> layout

        list ->
          if is_list(list) do
            do_layout(layout, list, padding, width, height, translate)
          else
            layout
          end
      end
    end)
  end

  defp translate_and_render(layout, module, data, opts) do
    {l, t, r, b} = get_bounds(module, data, opts)
    {tx, _ty} = layout.translate
    layout =
      case fits_in_x?(r + layout.last_x + layout.padding, layout.width) do
        true ->
          x = l + layout.last_x + layout.padding
          y = layout.last_y
          %{
            layout |
            last_x: r + layout.last_x + layout.padding,
            graph: module.add_to_graph(layout.graph, data, Keyword.merge(opts, translate: {x, y}))
          }
        false ->
          x = l + tx + layout.padding
          y = t + layout.last_y + layout.largest_height + layout.padding
          %{
            layout |
            last_x: l + tx + r + layout.padding,
            last_y: t + layout.last_y + layout.largest_height + layout.padding,
            graph: module.add_to_graph(layout.graph, data, Keyword.merge(opts, translate: {x, y}))
          }
      end

    layout = if r > layout.largest_width, do: %{layout | largest_width: r}, else: layout
    if b > layout.largest_height, do: %{layout | largest_height: b}, else: layout
  end

  defp get_bounds(mod, data, opts) do
    mod.bounds(data, opts)
  end

  defp fits_in_x?(potential_x, max_x), do: potential_x <= max_x

  # defp fits_in_y?(potential_y, max_y), do: potential_y <= max_y
end