defmodule GithubIssues.CLI do
  @default_count 4
  import GithubIssues.TableFormatter
  @moduledoc """
  Handle the command line parsing and the dispatch to
  the various functions that end up generating a
  table of the last_n_issues in a github project
  """

  def main(argv) do
    argv
    |> parse_args
    |> process
  end

  def process(:unknown) do
    IO.puts "Unknown command, please try again"
    System.halt(0)
  end

  def process(:help) do
    IO.puts """
    usage: issues <user> <project> [count | # {@default_count} ]
    """
    System.halt(0)
  end

  def process({user, project, count}) do
    GithubIssues.Engine.fetch(user, project)
    |> decode_response
    |> convert_to_list_of_maps
    |> sort_into_asc_order
    |> Enum.take(count)
    |> print_table_for_columns(["number", "created_at", "title"])
  end

  def decode_response({:ok, body}) do
    body
  end

  def decode_response({:error, error}) do
    {_, message} = List.keyfind(error, "message", 0)
    IO.puts "Error fetching from Github: #{message}"
    System.halt(2)
  end

  def convert_to_list_of_maps(list) do
    list
    |> Enum.map(&Enum.into(&1, Map.new))
  end

  def sort_into_asc_order(list) do
    Enum.sort(list, fn(e1, e2) -> e1["created_at"] <= e2["created_at"] end)    
  end

  def parse_args(argv) do
    parse = OptionParser.parse(argv, switches: [help: :boolean], aliases: [h: :help])
    case parse do
      {[help: true], _, _} -> :help
      {_, [user, project, count], _} -> {user, project, String.to_integer(count)}
      {_, [user, project], _} -> {user, project, @default_count}
      _ -> :unknown
    end
  end
end