defmodule Image.Color do
  @moduledoc """
  Functions to manage image color and color conversion.

  """

  @typedoc """
  Reference to an ICC color profile

  * `:none` means no profile
  * `:cmyk`, `:srgb` and `:p3` refer to the built-in color profiles
  * `Path.t()` means any file system path. If the path is a relative
    path then is will be loaded from the systems profile directory.

  """
  @type icc_profile :: :none | :cmyk | :srgb | :p3 | Path.t()

  @typedoc """
  An rbg color expressed as a list of numbers.

  The number of list elements and the type
  varies depending on the image format, colorspace
  and dimensions.

  For a common `sRGB` image it will be a list of
  three of four images. If the fourth number is provided
  it will be considered as an alpha transparency band.

  """
  @type rgb_color :: [number()]

  @inbuilt_profiles [:none, :srgb, :cmyk, :p3]

  @doc """
  Guards whether a given value can be interpreted
  as a color value.

  """
  defguard is_color(color)
           when (is_number(color) and color > 0) or (is_list(color) and length(color) == 3)

  @doc """
  Guards whether a given profile is one of the inbuilt
  profiles.

  """
  defguard is_inbuilt_profile(profile) when profile in @inbuilt_profiles

  @doc """
  Returns the list of color profiles built into
  `libvips`.

  """
  def inbuilt_profiles, do: @inbuilt_profiles

  @doc """
  Returns a boolean indicating if the given
  profile is known and can be used for image
  operations.

  """
  def known_icc_profile?(profile) when profile in @inbuilt_profiles do
    true
  end

  def known_icc_profile?(path) do
    case Vix.Vips.Operation.profile_load(path) do
      {:ok, _} -> true
      _other -> false
    end
  end

  @priv_dir :code.priv_dir(:image) |> List.to_string()
  @path Path.join(@priv_dir, "color_map.csv")

  @color_map File.read!(@path)
  |> String.split("\n", trim: true)
  |> Enum.map(&String.split(&1, ", "))
  |> Enum.map(fn [name, hex] ->
    <<"#", r::bytes-2, g::bytes-2, b::bytes-2>> = hex
    rgb = [String.to_integer(r, 16), String.to_integer(g, 16), String.to_integer(b, 16)]
    {String.downcase(name), hex: hex, rgb: rgb}
  end)
  |> Map.new()

  @doc """
  Returns a mapping from CSS color names to CSS hex values
  and RGB triplets as a list.

  """
  def color_map do
    @color_map
  end

  def rgb_color!(color) when is_binary(color) do
    case color do
      <<"#", r::bytes-2, g::bytes-2, b::bytes-2>> ->
        [String.to_integer(r, 16), String.to_integer(g, 16), String.to_integer(b, 16)]

      color ->
        color_map()
        |> Map.fetch!(normalize(color))
        |> Keyword.fetch!(:rgb)
    end
  end

  def rgb_color!(color) when is_color(color) do
    color
  end

  @opacity 255

  def rgba_color!(color, a \\ @opacity)

  def rgba_color!(color, _a) when color in [:none, :transparent] do
    [0.0, 0.0, 0.0, 1.0]
  end

  def rgba_color!(color, a) when is_binary(color) and is_integer(a) do
    [r, g, b] = rgb_color!(color)
    [r, g, b, a]
  end

  def rgba_color!(color, a) when is_binary(color) and is_float(a) and a >= 0.0 and a <= 1.0 do
    a = round(@opacity * a)

    [r, g, b] = rgb_color!(color)
    [r, g, b, a]
  end

  def rgba_color!([r, g, b], a) do
    [r, g, b, a]
  end

  def normalize(color) do
    color
    |> to_string()
    |> String.downcase()
    |> String.replace(["_", "-", " "], "")
  end
end