defmodule Kudos do
  @moduledoc """
  Documentation for Kudos.
  """

  @license_file_names ~w(LICENSE.txt LICENSE.md LICENSE license.txt license.md license LICENSE-2.0.txt)
  @readme_file_names ~w(README.md README.markdown)

  @doc """
  Generates a licenses file in the root dir with the licenses of all deps.

  ## Examples

      iex> Kudos.generate() |> String.length()
      219

      iex> Kudos.generate(false) |> String.length()
      219

      iex> Kudos.generate(true) |> String.length()
      19050

  """
  def generate(include_dev_deps \\ false) do
    load_deps_meta_data(include_dev_deps)
    |> Enum.reduce(header(), fn meta_data, resp ->
      resp <> format(meta_data)
    end)
    |> String.trim()
  end

  defp header() do
    """
    # Project Licenses
    This file was generated by the kudos utility. It contains the name, version and checksum, description, links, maintainers and license information for every dependency in this project.

    ## Dependencies
    """
  end

  defp format(:umbrella) do
    ""
  end

  defp format(:dev) do
    ""
  end

  defp format(meta_data) do
    """
    ### #{meta_data.name} (Version #{meta_data.version} | Checksum: #{checksum(meta_data.checksum)})
    #{meta_data.description}

    Links: #{links(meta_data.links)}

    Maintainers: #{maintainers(meta_data.maintainers)}

    Licenses Used: #{meta_data.licenses}

    #{meta_data.license_file}
    """
  end

  defp checksum(value) when is_list(value) do
    value[:branch]
  end

  defp checksum(value) do
    value
  end

  defp maintainers(values) when is_nil(values) do
    ""
  end

  defp maintainers(values) when is_map(values) do
    Map.to_list(values)
    |> maintainers()
  end

  defp maintainers(values) when is_list(values) do
    Enum.join(values, ", ")
  end

  defp links(values) when is_nil(values) do
    ""
  end

  defp links(values) when is_map(values) do
    Map.to_list(values)
    |> Enum.map(&prepare_link(&1))
    |> Enum.join(", ")
  end

  defp prepare_link(value) when is_tuple(value) do
    "[#{elem(value, 0)}](#{elem(value, 1)})"
  end

  defp prepare_link({key, value}) do
    "[#{key}](#{value})"
  end

  defp load_deps_meta_data(include_dev_deps) do
    Mix.Dep.load_on_environment([])
    |> Enum.map(fn dep ->
      Mix.Dep.in_dependency(dep, fn _ ->
        case is_umbrella?(dep) do
          true ->
            :umbrella

          false ->
            case include_dev_deps || is_prod?(dep) do
              false ->
                :dev

              _ ->
                %{
                  name: Atom.to_string(Mix.Project.config()[:app]),
                  version: Mix.Project.config()[:version],
                  checksum: elem(dep.opts[:lock], 3),
                  description: Mix.Project.config()[:description],
                  source_url: Mix.Project.config()[:source_url],
                  links: get_in(Mix.Project.config(), [:package, :links]),
                  maintainers: get_in(Mix.Project.config(), [:package, :maintainers]),
                  licenses: get_in(Mix.Project.config(), [:package, :licenses]),
                  license_file: get_license_file_content(dep.opts[:dest])
                }
            end
        end
      end)
    end)
  end

  defp is_umbrella?(dep) do
    case List.keyfind(dep.opts, :in_umbrella, 0, {:in_umbrella, false}) do
      {:in_umbrella, true} -> true
      {:in_umbrella, false} -> from_umbrella?(dep)
    end
  end

  defp from_umbrella?(dep) do
    case List.keyfind(dep.opts, :from_umbrella, 0, {:from_umbrella, false}) do
      {:from_umbrella, true} -> true
      {:from_umbrella, false} -> false
    end
  end

  defp is_prod?(dep) do
    only = List.keyfind(dep.opts, :only, 0, [])

    case only do
      [] -> true
      _ -> false
    end
  end

  defp get_license_file_content(path) do
    (File.ls!(path) -- File.ls!(path) -- @license_file_names)
    |> read_license_file(path)
  end

  defp read_license_file([], path) do
    read_license_from_readme_file(path)
  end

  defp read_license_file([first_file_name | _], path) do
    Path.join(path, first_file_name)
    |> File.read!()
  end

  defp read_license_from_readme_file(path) do
    files = File.ls!(path) -- File.ls!(path) -- @readme_file_names
    read_license_from_readme_file(files, path)
  end

  defp read_license_from_readme_file([], _path) do
    "Full license text not found in dependency source."
  end

  defp read_license_from_readme_file([first_file_name | _], path) do
    readme_content =
      Path.join(path, first_file_name)
      |> File.read!()

    case String.split(readme_content, "# License", parts: 2) do
      [_, content] ->
        content

      _ ->
        "Full license text not found in dependency source."
    end
  end
end