defmodule Gulib.List do

  # list_a与list_b是否有交集
  def mixed?(list_a, list_b) do
    Enum.reduce(list_a, false, fn(i, mixed) ->
      mixed || Enum.member?(list_b, i)
    end)
  end

  def index_by(list, key) do
    list |> Enum.map(fn(item) -> {Map.get(item, key), item} end) |> Map.new
  end

  def compact list do
    list |> Enum.filter(fn(item) -> !!item end)
  end

  def find_index(list, ele) when is_list(list) do
    Enum.find_index(list, fn(x) -> x == ele end) || -1
  end

  def max([]), do: nil
  def max(list) do
    Enum.max(list)
  end

  def min([]), do: nil
  def min(list) do
    Enum.min(list)
  end

  def sample([]), do: nil
  def sample([item]), do: item
  def sample(list) do
    list |> sample(1) |> List.first
  end
  def sample(list, count) do
    Enum.take_random(list, count)
  end

  def sort_by_values(records, values, field_key) do
    Enum.sort(records, fn(a, b) ->
      find_index(values, a |> Map.get(field_key)) < find_index(values, b |> Map.get(field_key))
    end)
  end

end