elxlog

defmodule Elxlog do
  @moduledoc """
  Elxlog is main module of Elxlog
  """
  
  def repl() do
    IO.puts("Elxlog ver0.15")
    repl1([])
  end

  defp repl1(def) do
    try do
      IO.write("?- ")
      {s, _} = Read.parse([], :stdin)
      s1 = add_ask(s)
      {s2, _, def1} = Prove.prove_all(s1, [], def, 1)
      Print.print(s2)
      repl1(def1)
    catch
      x ->
        IO.puts(x)

        if x != "goodbye" do
          repl1(def)
        else
          true
        end
    end
  end

  def find_var(x) do
    find_var1(x, []) |> unique() |> Enum.reverse()
  end

  def find_var1([], res) do
    res
  end

  def find_var1(x, res) when is_number(x) do
    res
  end

  def find_var1(x, res) when is_atom(x) do
    if is_var(x) && !Enum.member?(res, x) do
      [x | res]
    else
      res
    end
  end

  def find_var1([x | xs], res) when is_list(x) do
    res1 = find_var1(x, [])
    find_var1(xs, res1 ++ res)
  end

  def find_var1([x | xs], res) do
    if is_var(x) && !Enum.member?(res, x) do
      find_var1(xs, [x | res])
    else
      find_var1(xs, res)
    end
  end

  def unique([]) do
    []
  end

  def unique([x | xs]) do
    if Enum.member?(xs, x) do
      unique(xs)
    else
      [x | unique(xs)]
    end
  end

  def add_ask(x) do
    ask = [:builtin, [:ask | find_var(x)]]

    if is_pred(x) || is_builtin(x) do
      [x] ++ [ask]
    else
      # conjunction
      x ++ [ask]
    end
  end

  # -------------data type------------
  def is_pred([:pred, _]) do
    true
  end

  def is_pred(_) do
    false
  end

  def is_clause([:clause, _, _]) do
    true
  end

  def is_clause(_) do
    false
  end

  def is_builtin([:builtin, _]) do
    true
  end

  def is_builtin(_) do
    false
  end

  def is_compound(x) do
    cond do
      is_pred(x) -> true
      is_builtin(x) -> true
      true -> false
    end
  end

  def is_formula([:formula, _]) do
    true
  end

  def is_formula(_) do
    false
  end

  def is_var(x) do
    if (is_atomvar(x) && !is_anonymous(x)) || is_variant(x) do
      true
    else
      false
    end
  end

  # atom vairable
  def is_atomvar(x) when is_atom(x) do
    x1 = x |> Atom.to_charlist() |> Enum.at(0)

    cond do
      # under bar
      x1 == 95 -> true
      # uppercase
      x1 >= 65 && x1 <= 90 -> true
      true -> false
    end
  end

  def is_atomvar(_) do
    false
  end

  def is_anonymous(:_) do
    true
  end

  def is_anonymous({:_, _}) do
    true
  end

  def is_anonymous(_) do
    false
  end

  # variant variable
  def is_variant({x, y}) when is_integer(y) do
    if is_atomvar(x) do
      true
    else
      false
    end
  end

  def is_variant(_) do
    false
  end

  # Error
  def error(msg, ls) do
    IO.write(msg)
    error1(ls)
    throw(" ")
  end

  defp error1([]) do
    true
  end

  defp error1([x | xs]) do
    Print.print1(x)
    IO.write(" ")
    error1(xs)
  end

  # for debug
  @doc"""
  for debug
  """
  def stop() do
    raise "debug stop"
  end

  # for test
  @doc"""
  for test
  """
  def bar(str) do
    def = []
    {s, _} = Read.parse(Read.tokenize(str, :stdin), :stdin)
    {s1, _, _} = Prove.prove_all([s], [], def, 1)
    Print.print(s1)
  end
end