defmodule Minipeg.Combinators do
  use Minipeg.Types

  alias Minipeg.{Cache, Failure, Input, Parser, Success}

  import Failure, only: [fail: 3]
  import Parser, only: [new: 2, parse: 3]
  import Success, only: [succeed: 3]
  # import Success, only: [succeed: 3]

  @moduledoc ~S"""
  All public functions in this module take a parser and potentially more parameters and
  return a new parser
  """

  @type wrapped_parser_t :: ( -> Parser.t )

  @typep upto_behavior_t :: :keep | :include | :discard

  @doc ~S"""
  Just parses with `parser` but displays, input and result to stderr
  """
  @spec debug(Parser.t, binary?) :: Parser.t
  def debug(parser, name \\ nil) do
    new(name||parser.name,
      fn input, cache, _ ->
        result = parse(parser, input, cache)
        IO.puts(:stderr, inspect(%{name: name || parser.name, input: input, cache: cache}))
        IO.puts(:stderr, inspect(result))
        result
      end
    )
  end

  @doc ~S"""
  Parsers a string that would be parsed by parser but ignoring leading whitespace, if you also want to
  ignore whitespace after the parsed string use `tokenized`
  """
  @spec ignore_ws(Parser.t, binary?(), boolean()) :: Parser.t
  def ignore_ws(parser, name \\ nil, skip_newlines \\ false) do
    name1 = name || "ignore_ws"
    new(
      name1,
      fn input, cache, _ ->
        {next, input1} = Input.take(input)
        case next do
          "" -> parse(parser, input, cache)
          " " -> parse(ignore_ws(parser, name1, skip_newlines), input1, cache)
          "\t" -> parse(ignore_ws(parser, name1, skip_newlines), input1, cache)
          "\n" when skip_newlines -> parse(ignore_ws(parser, name1, skip_newlines), input1, cache)
          _ -> parse(parser, input, cache)
        end
      end
    )
  end

  @spec in_between_parser(Parser.t, Parser.t, Parser.t, binary?()) :: Parser.t
  def in_between_parser(ignored_start_parser, inside_parser, ignored_end_parser, name \\ nil) do
    name1 = name ||
      "in_between_parser(#{ignored_start_parser.name}, #{inside_parser.name}, #{ignored_end_parser.name})"

    sequence([
      ignored_start_parser, inside_parser, ignored_end_parser
    ], name1)
    |> map(fn [_, ast, _] -> ast end, name1)
  end

  @doc ~S"""
  Unwrapps a wrapped parser and parses with it
  """
  @spec lazy(wrapped_parser_t(), binary?()) :: Parser.t
  def lazy(wrapped_parser, name \\ nil) do
    name1 = name || "lazy"
    new(
      name1,
      fn input, cache, _ ->
        parse(wrapped_parser.(), input, cache)
      end
    )
  end

  @doc ~S"""
  Parses a list defined by an `element_parser` and a `seperator_parser`
  """
  @spec list_parser(Parser.t, Parser.t, binary?(), non_neg_integer()) :: Parser.t
  def list_parser(element_parser, seperator_parser, name \\ nil, min_count \\ 0) do
    name1 = name || "list_parser(#{element_parser.name}, #{seperator_parser.name})"
    maybe(
      sequence([
        element_parser,
        many(
          sequence([
            seperator_parser,
            element_parser
          ])
        )
      ])
    )
    |> map(&_flatten_list/1)
    |> satisfy(fn list ->
      if Enum.count(list) >= min_count do
        {:ok, list}
      else
        {:error, "Parser #{name1} only parsed #{Enum.count(list)} element(s) but #{min_count} were needed"}
      end
    end)
  end

  @doc ~S"""
  Applies a parser as many times as possible, can use `min_count` (defaulting to 0) to
  fail unless the parser could parse `min_count` times
  """
  @spec many(Parser.t(), maybe(binary), non_neg_integer()) :: Parser.t()
  def many(parser, name \\ nil, min_count \\ 0) do
    name1 = name || parser.name

    new(
      name1,
      &_many(parser, min_count, &1, &1, &2, &3)
    )
  end

  @spec many_sel(list(Parser.t), binary?(), non_neg_integer()) :: Parser.t
  def many_sel(parsers, name \\ nil, min_count \\ 0) do
    name1 = name || ( "many_sel:[ #{parsers |> Enum.map(&(&1.name)) |> Enum.join("|")} ]" )

    many(select(parsers), name1, min_count)
  end

  @spec many_seq(list(Parser.t()), binary?(), non_neg_integer()) :: Parser.t()
  def many_seq(parsers, name \\ nil, min_count \\ 0) do
    name1 = name || ( "many_seq:[ #{parsers |> Enum.map(&(&1.name)) |> Enum.join("...")} ]" )

    many(sequence(parsers), name1, min_count)
  end

  @doc ~S"""
  Succeeds if `parser` succeeds, but maps the ast with `mapper_fun`.
  If `parser` fails, it just fails
  """
  @spec map(Parser.t(), (ast_t() -> ast_t()), maybe(binary)) :: Parser.t()
  def map(parser, mapper_fun, name \\ nil) do
    name1 = name || parser.name

    new(
      name1,
      fn input, cache, _ ->
        case parse(parser, input, cache) do
          %Failure{} = f -> f
          %Success{ast: ast} = s -> %{s | ast: mapper_fun.(ast)}
        end
      end
    )
  end

  @doc ~S"""
  parses iff `parser` parses then maps the ast to a string with `IO.chardata_to_string/1`
  The ast must therefore be of type `IO data`
  """
  @spec map_to_string(Parser.t, binary?()) :: Parser.t
  def map_to_string(parser, name \\ nil) do
    name1 = name || "map_to_string(#{parser.name})"

    parser
    |> map(&IO.chardata_to_string/1, name1)
  end

  @spec maybe(Parser.t(), binary?) :: Parser.t()
  def maybe(parser, name \\ nil) do
    name1 = name || "maybe(#{parser.name})"

    new(
      name1,
      &_maybe(parser, &1, &2, &3)
    )
  end

  @doc ~S"""
  Returns a parser that only succeeds if the original parser succeeds **and**
  the satisfier function that is called with the ast of the original result
  returns {:ok, value}. It also changes the original ast with value in the
  final result.
  """
  @spec satisfy(Parser.t(), satisfier_t(), binary?) :: Parser.t()
  def satisfy(parser, satisfier, name \\ nil) do
    name1 = name || parser.name

    new(
      name1,
      &_satisfy(parser, satisfier, &1, &2, &3)
    )
  end

  @doc ~S"""
  Looks into the cache (for this parsing position) before parsing,
  if no result found parses and puts the result into the cache (for this parsing position)
  """
  @spec savepoint(Parser.t(), binary?, binary?) :: Parser.t()
  def savepoint(parser, sp_name \\ nil, name \\ nil) do
    sp_name1 = sp_name || parser.name
    name1 = name || parser.name

    new(
      name1,
      &_savepoint(parser, sp_name1, &1, &2, &3)
    )
  end

  @spec select(list(Parser.t()), binary?()) :: Parser.t()
  def select(parsers, name \\ nil) do
    name1 = name || "select"

    new(
      name1,
      &_select(parsers, name, &1, &2, &3)
    )
  end

  @spec option(list(Parser.t()), binary?()) :: Parser.t
  defdelegate option(parsers, name \\ nil), to: __MODULE__, as: :select

  @spec sequence(list(Parser.t()), binary?) :: Parser.t()
  def sequence(parsers, name \\ nil) do
    name1 = name || "sequence"

    new(
      name1,
      &_sequence(parsers, &1, &1, &2, &3)
    )
  end

  @spec tokenize(Parser.t) :: Parser.t()
  def tokenize(parser) do
    in_between_parser(Minipeg.Parsers.ws_parser(), parser, Minipeg.Parsers.ws_parser())
  end

  @doc ~S"""
  Consume chars until `parser` parses and return them as parsed ast, fails if parser never succeeds
  can add the delimiter to the ast or leave it on the input stream
  """
  @spec upto_parser_parser(Parser.t, binary?(), upto_behavior_t()) :: Parser.t
  def upto_parser_parser(parser, name \\ nil, parse_behavior \\ :keep) do
    name1 = name || "upto_parser_parser(#{parser.name}, #{parse_behavior})"
    new(
      name1,
      &_upto_parser_parser(&1, &2, &3, name1, parse_behavior, parser)
    )
  end

  @spec _flatten_list(maybe(list(ast_t()))) :: list(ast_t())
  defp _flatten_list(list_ast)
  # The list_ast is of form [fst_element, [sep, snd_element], ... ] or nil
  defp _flatten_list(nil), do: []
  defp _flatten_list([fst_ele, rest_list]) do
    [ 
      fst_ele | rest_list |> Enum.map(&Enum.at(&1, 1))
    ]
  end

  @spec _many(Parser.t(), integer(), Input.t(), Input.t(), Cache.t(), binary(), list()) ::
  result_t()
  defp _many(parser, min_count, input, curr_input, cache, name, result \\ []) do
    case parse(parser, curr_input, cache) do
      %Success{} = s ->
        _many(parser, min_count - 1, input, s.rest, s.cache, name, [s.ast | result])

      %Failure{} = f ->
        if min_count > 0 do
          fail("Missing #{min_count} parses in many in #{name}", input, cache)
        else
          succeed(Enum.reverse(result), curr_input, f.cache)
        end
    end
  end

  @spec _maybe(Parser.t(), Input.t(), Cache.t(), binary()) :: result_t
  defp _maybe(parser, input, cache, _name) do
    case parse(parser, input, cache) do
      %Success{} = s -> s
      %Failure{} -> succeed(nil, input, cache)
    end
  end

  @spec _satisfy(Parser.t(), satisfier_t(), Input.t(), Cache.t(), any()) :: result_t
  defp _satisfy(parser, satisfier, input, cache, _name) do
    case parse(parser, input, cache) do
      %Failure{} = f ->
        f

      %Success{ast: ast} = s ->
        case satisfier.(ast) do
          {:ok, ast1} -> %{s | ast: ast1}
          {:error, reason} -> fail(reason, input, cache)
        end
    end
  end

  @spec _savepoint(Parser.t(), binary(), Input.t(), Cache.t(), binary()) :: result_t
  defp _savepoint(parser, sp_name, input, cache, _name) do
    case Cache.lookup(cache, input, sp_name) do
      nil ->
        result = parse(parser, input, cache)
        %{result | cache: Cache.update(cache, Input.position(input), sp_name, result)}

      result ->
        result
    end
  end

  @spec _select(list(Parser.t()), binary(), Input.t(), Cache.t(), binary?) :: result_t
  defp _select(parsers, name, input, cache, _name) do
    case parsers do
      [] ->
        fail("no alternative could be parsed in #{name}", input, cache)

      [parser | alt_parsers] ->
        case parse(parser, input, cache) do
          %Failure{cache: cache1} -> _select(alt_parsers, name, input, cache1, nil)
          %Success{} = s -> s
        end
    end
  end

  @spec _sequence(list(Parser.t()), Input.t(), Input.t(), Cache.t(), binary(), list(ast_t())) ::
  result_t
  defp _sequence(parsers, input, current_input, cache, name, result \\ []) do
    case parsers do
      [] ->
        succeed(Enum.reverse(result), current_input, cache)

      [parser | other_parsers] ->
        case parse(parser, current_input, cache) do
          %Failure{reason: reason, cache: cache1} ->
            fail("#{reason} in #{name}", input, cache1)

          %Success{ast: ast, rest: rest, cache: cache2} ->
            _sequence(other_parsers, input, rest, cache2, name, [ast | result])
        end
    end
  end

  @spec _upto_parser_parser(Input.t(), Cache.t(), binary(), binary(), upto_behavior_t(), Parser.t(), ast_t()) :: result_t()
  defp _upto_parser_parser(input, cache, name, _name, parse_delim, parser, ast \\ [])
  defp _upto_parser_parser(input, cache, name, _name, :discard, parser, ast) do
    case parse(parser, input, cache) do
      %Success{rest: new_input} -> succeed(ast|>Enum.reverse|>Enum.join, new_input, cache)
      _ -> _upto_parser_repeat(input, cache, name, parser, :discard, ast)
    end
  end
  defp _upto_parser_parser(input, cache, name, _name, :include, parser, ast) do
    case parse(parser, input, cache) do
      %Success{ast: delim_ast, rest: new_input} -> succeed({ast|>Enum.reverse|>Enum.join, delim_ast}, new_input, cache)
      _ -> _upto_parser_repeat(input, cache, name, parser, :include, ast)
    end
  end
  defp _upto_parser_parser(input, cache, name, _name, :keep, parser, ast) do
    case parse(parser, input, cache) do
      %Success{} -> succeed(ast|>Enum.reverse|>Enum.join, input, cache)
      _ -> _upto_parser_repeat(input, cache, name, parser, :keep, ast)
    end
  end

  @spec _upto_parser_repeat(Input.t(), Cache.t(), binary(), Parser.t(), upto_behavior_t(), ast_t()) :: result_t()
  defp _upto_parser_repeat(input, cache, name, parser, type, ast) do
    {next, rest} = Input.take(input)
    case next do
      "" -> fail("encountered end of input in #{name}", input, cache)
      h -> _upto_parser_parser(rest, cache, name, name, type, parser, [h|ast])
    end
  end
end

# SPDX-License-Identifier: Apache-2.0