defmodule RDF.Vocabulary.Namespace do
  @moduledoc """
  A RDF vocabulary as a `RDF.Namespace`.

  `RDF.Vocabulary.Namespace` modules represent a RDF vocabulary as a `RDF.Namespace`.
  They can be defined with the `defvocab/2` macro of this module.

  RDF.ex comes with predefined modules for some fundamental vocabularies in
  the `RDF.NS` module.
  """

  alias RDF.Description
  alias RDF.Utils.ResourceClassifier

  import RDF.Utils, only: [downcase?: 1]

  @type t :: module

  @vocabs_dir "priv/vocabs"

  defmacro __using__(_opts) do
    quote do
      import unquote(__MODULE__)
    end
  end

  @doc """
  Defines a `RDF.Namespace` module for a RDF vocabulary.
  """
  defmacro defvocab(name, opts) do
    strict = strict?(opts)
    base_iri = base_iri!(opts)
    file = filename!(opts)

    {terms, data} =
      case source!(opts) do
        {:terms, terms} -> {terms, nil}
        {:data, data} -> {rdf_data_vocab_terms(data, base_iri), data}
      end

    unless Mix.env() == :test do
      IO.puts("Compiling vocabulary namespace for #{base_iri}")
    end

    ignored_terms = ignored_terms!(opts)

    terms =
      terms
      |> term_mapping!(opts)
      |> Map.drop(MapSet.to_list(ignored_terms))
      |> validate_terms!
      |> validate_characters!(opts)
      |> validate_case!(data, base_iri, opts)

    case_separated_terms = group_terms_by_case(terms)
    lowercased_terms = Map.get(case_separated_terms, :lowercased, %{})

    quote do
      vocabdoc = Module.delete_attribute(__MODULE__, :vocabdoc)

      defmodule unquote(name) do
        @moduledoc vocabdoc

        @behaviour Elixir.RDF.Namespace

        if unquote(file) do
          @external_resource unquote(file)
        end

        @base_iri unquote(base_iri)
        @spec __base_iri__ :: String.t()
        def __base_iri__, do: @base_iri

        @strict unquote(strict)
        @spec __strict__ :: boolean
        def __strict__, do: @strict

        @terms unquote(Macro.escape(terms))
        @impl Elixir.RDF.Namespace
        def __terms__, do: @terms |> Map.keys()

        @spec __term_aliases__ :: [atom]
        def __term_aliases__ do
          @terms
          |> Enum.filter(fn {_, term} -> term != true end)
          |> Enum.map(fn {alias, _} -> alias end)
        end

        @ignored_terms unquote(Macro.escape(ignored_terms))

        @doc """
        Returns all known IRIs of the vocabulary.
        """
        @spec __iris__ :: [Elixir.RDF.IRI.t()]
        def __iris__ do
          @terms
          |> Enum.map(fn
            {term, true} -> term_to_iri(@base_iri, term)
            {_alias, term} -> term_to_iri(@base_iri, term)
          end)
          |> Enum.uniq()
        end

        define_vocab_terms(unquote(lowercased_terms), unquote(base_iri))

        @impl Elixir.RDF.Namespace
        @dialyzer {:nowarn_function, __resolve_term__: 1}
        def __resolve_term__(term) do
          case @terms[term] do
            nil ->
              if @strict or MapSet.member?(@ignored_terms, term) do
                {:error,
                 %Elixir.RDF.Namespace.UndefinedTermError{
                   message: "undefined term #{term} in strict vocabulary #{__MODULE__}"
                 }}
              else
                {:ok, term_to_iri(@base_iri, term)}
              end

            true ->
              {:ok, term_to_iri(@base_iri, term)}

            original_term ->
              {:ok, term_to_iri(@base_iri, original_term)}
          end
        end

        if not @strict do
          def unquote(:"$handle_undefined_function")(term, []) do
            if MapSet.member?(@ignored_terms, term) do
              raise UndefinedFunctionError
            else
              term_to_iri(@base_iri, term)
            end
          end

          def unquote(:"$handle_undefined_function")(term, [subject | objects]) do
            objects =
              case objects do
                [objects] when is_list(objects) -> objects
                _ -> objects
              end

            if MapSet.member?(@ignored_terms, term) do
              raise UndefinedFunctionError
            else
              case subject do
                %Description{} -> subject
                _ -> Description.new(subject)
              end
              |> Description.add({term_to_iri(@base_iri, term), objects})
            end
          end
        end
      end
    end
  end

  @doc false
  defmacro define_vocab_terms(terms, base_iri) do
    terms
    |> Stream.filter(fn
      {term, true} -> valid_term?(term)
      {_, _} -> true
    end)
    |> Stream.map(fn
      {term, true} -> {term, term}
      {term, original_term} -> {term, original_term}
    end)
    |> Enum.map(fn {term, iri_suffix} ->
      iri = term_to_iri(base_iri, iri_suffix)

      quote do
        @doc "<#{unquote(to_string(iri))}>"
        def unquote(term)(), do: unquote(Macro.escape(iri))

        @doc "`RDF.Description` builder for `#{unquote(term)}/0`"
        def unquote(term)(subject, object)

        def unquote(term)(%Description{} = subject, object) do
          Description.add(subject, {unquote(Macro.escape(iri)), object})
        end

        def unquote(term)(subject, object) do
          Description.new(subject, init: {unquote(Macro.escape(iri)), object})
        end

        # Is there a better way to support multiple objects via arguments?
        @doc false
        def unquote(term)(subject, o1, o2),
          do: unquote(term)(subject, [o1, o2])

        @doc false
        def unquote(term)(subject, o1, o2, o3),
          do: unquote(term)(subject, [o1, o2, o3])

        @doc false
        def unquote(term)(subject, o1, o2, o3, o4),
          do: unquote(term)(subject, [o1, o2, o3, o4])

        @doc false
        def unquote(term)(subject, o1, o2, o3, o4, o5),
          do: unquote(term)(subject, [o1, o2, o3, o4, o5])
      end
    end)
  end

  defp strict?(opts),
    do: Keyword.get(opts, :strict, true)

  defp base_iri!(opts) do
    base_iri = Keyword.fetch!(opts, :base_iri)

    unless is_binary(base_iri) and String.ends_with?(base_iri, ~w[/ # .]) do
      raise RDF.Namespace.InvalidVocabBaseIRIError,
            "a base_iri without a trailing '/' or '#' is invalid"
    else
      base_iri
    end
  end

  defp source!(opts) do
    cond do
      Keyword.has_key?(opts, :file) ->
        {:data, filename!(opts) |> RDF.read_file!()}

      rdf_data = Keyword.get(opts, :data) ->
        {:data, raw_rdf_data(rdf_data)}

      terms = Keyword.get(opts, :terms) ->
        {:terms, terms_from_user_input!(terms)}

      true ->
        raise KeyError, key: ~w[terms data file], term: opts
    end
  end

  defp terms_from_user_input!(terms) do
    # TODO: find an alternative to Code.eval_quoted - We want to support that the terms can be given as sigils ...
    {terms, _} = Code.eval_quoted(terms, [], rdf_data_env())

    Enum.map(terms, fn
      term when is_atom(term) ->
        term

      term when is_binary(term) ->
        String.to_atom(term)

      term ->
        raise RDF.Namespace.InvalidTermError,
              "'#{term}' is not a valid vocabulary term"
    end)
  end

  defp raw_rdf_data(%Description{} = rdf_data), do: rdf_data
  defp raw_rdf_data(%RDF.Graph{} = rdf_data), do: rdf_data
  defp raw_rdf_data(%RDF.Dataset{} = rdf_data), do: rdf_data

  defp raw_rdf_data(rdf_data) do
    # TODO: find an alternative to Code.eval_quoted
    {rdf_data, _} = Code.eval_quoted(rdf_data, [], rdf_data_env())
    rdf_data
  end

  defp ignored_terms!(opts) do
    # TODO: find an alternative to Code.eval_quoted - We want to support that the terms can be given as sigils ...
    with terms = Keyword.get(opts, :ignore, []) do
      {terms, _} = Code.eval_quoted(terms, [], rdf_data_env())

      terms
      |> Enum.map(fn
        term when is_atom(term) -> term
        term when is_binary(term) -> String.to_atom(term)
        term -> raise RDF.Namespace.InvalidTermError, inspect(term)
      end)
      |> MapSet.new()
    end
  end

  defp term_mapping!(terms, opts) do
    terms =
      Map.new(terms, fn
        term when is_atom(term) -> {term, true}
        term -> {String.to_atom(term), true}
      end)

    Keyword.get(opts, :alias, [])
    |> Enum.reduce(terms, fn {alias, original_term}, terms ->
      term = String.to_atom(original_term)

      cond do
        not valid_characters?(alias) ->
          raise RDF.Namespace.InvalidAliasError,
                "alias '#{alias}' contains invalid characters"

        Map.get(terms, alias) == true ->
          raise RDF.Namespace.InvalidAliasError,
                "alias '#{alias}' already defined"

        strict?(opts) and not Map.has_key?(terms, term) ->
          raise RDF.Namespace.InvalidAliasError,
                "term '#{original_term}' is not a term in this vocabulary"

        Map.get(terms, term, true) != true ->
          raise RDF.Namespace.InvalidAliasError,
                "'#{original_term}' is already an alias"

        true ->
          Map.put(terms, alias, to_string(original_term))
      end
    end)
  end

  defp aliased_terms(terms) do
    terms
    |> Map.values()
    |> MapSet.new()
    |> MapSet.delete(true)
    |> Enum.map(&String.to_atom/1)
  end

  @invalid_terms MapSet.new(~w[
    and
    or
    xor
    in
    fn
    def
    when
    if
    for
    case
    with
    quote
    unquote
    unquote_splicing
    alias
    import
    require
    super
    __aliases__
  ]a)

  def invalid_terms, do: @invalid_terms

  defp validate_terms!(terms) do
    with aliased_terms = aliased_terms(terms) do
      for {term, _} <- terms, term not in aliased_terms and not valid_term?(term) do
        term
      end
      |> handle_invalid_terms!
    end

    terms
  end

  defp valid_term?(term), do: term not in @invalid_terms

  defp handle_invalid_terms!([]), do: nil

  defp handle_invalid_terms!(invalid_terms) do
    raise RDF.Namespace.InvalidTermError, """
    The following terms can not be used, because they conflict with the Elixir semantics:

    - #{Enum.join(invalid_terms, "\n- ")}

    You have the following options:

    - define an alias with the :alias option on defvocab
    - ignore the resource with the :ignore option on defvocab
    """
  end

  defp validate_characters!(terms, opts) do
    if (handling = Keyword.get(opts, :invalid_characters, :fail)) == :ignore do
      terms
    else
      terms
      |> detect_invalid_characters
      |> handle_invalid_characters(handling, terms)
    end
  end

  defp detect_invalid_characters(terms) do
    with aliased_terms = aliased_terms(terms) do
      for {term, _} <- terms, term not in aliased_terms and not valid_characters?(term), do: term
    end
  end

  defp handle_invalid_characters([], _, terms), do: terms

  defp handle_invalid_characters(invalid_terms, :fail, _) do
    raise RDF.Namespace.InvalidTermError, """
    The following terms contain invalid characters:

    - #{Enum.join(invalid_terms, "\n- ")}

    You have the following options:

    - if you are in control of the vocabulary, consider renaming the resource
    - define an alias with the :alias option on defvocab
    - change the handling of invalid characters with the :invalid_characters option on defvocab
    - ignore the resource with the :ignore option on defvocab
    """
  end

  defp handle_invalid_characters(invalid_terms, :warn, terms) do
    Enum.each(invalid_terms, fn term ->
      IO.warn("'#{term}' is not valid term, since it contains invalid characters")
    end)

    terms
  end

  defp valid_characters?(term) when is_atom(term),
    do: valid_characters?(Atom.to_string(term))

  defp valid_characters?(term),
    do: Regex.match?(~r/^[a-zA-Z_]\w*$/, term)

  defp validate_case!(terms, nil, _, _), do: terms

  defp validate_case!(terms, data, base_iri, opts) do
    if (handling = Keyword.get(opts, :case_violations, :warn)) == :ignore do
      terms
    else
      terms
      |> detect_case_violations(data, base_iri)
      |> group_case_violations
      |> handle_case_violations(handling, terms, base_iri, opts)
    end
  end

  defp detect_case_violations(terms, data, base_iri) do
    aliased_terms = aliased_terms(terms)

    terms
    |> Enum.filter(fn {term, _} ->
      not (Atom.to_string(term) |> String.starts_with?("_"))
    end)
    |> Enum.filter(fn
      {term, true} ->
        if term not in aliased_terms do
          proper_case?(term, base_iri, Atom.to_string(term), data)
        end

      {term, original_term} ->
        proper_case?(term, base_iri, original_term, data)
    end)
  end

  defp proper_case?(term, base_iri, iri_suffix, data) do
    case ResourceClassifier.property?(term_to_iri(base_iri, iri_suffix), data) do
      true -> not downcase?(term)
      false -> downcase?(term)
      nil -> downcase?(term)
    end
  end

  defp group_case_violations(violations) do
    violations
    |> Enum.group_by(fn
      {term, true} ->
        if downcase?(term),
          do: :lowercased_term,
          else: :capitalized_term

      {term, _original} ->
        if downcase?(term),
          do: :lowercased_alias,
          else: :capitalized_alias
    end)
  end

  defp handle_case_violations(%{} = violations, _, terms, _, _) when map_size(violations) == 0,
    do: terms

  defp handle_case_violations(violations, :fail, _, base_iri, _) do
    resource_name_violations = fn violations ->
      violations
      |> Enum.map(fn {term, true} -> term_to_iri(base_iri, term) end)
      |> Enum.map(&to_string/1)
      |> Enum.join("\n- ")
    end

    alias_violations = fn violations ->
      violations
      |> Enum.map(fn {term, original} ->
        "alias #{term} for #{term_to_iri(base_iri, original)}"
      end)
      |> Enum.join("\n- ")
    end

    violation_error_lines =
      violations
      |> Enum.map(fn
        {:capitalized_term, violations} ->
          """
          Terms for properties should be lowercased, but the following properties are
          capitalized:

          - #{resource_name_violations.(violations)}

          """

        {:lowercased_term, violations} ->
          """
          Terms for non-property resource should be capitalized, but the following
          non-properties are lowercased:

          - #{resource_name_violations.(violations)}

          """

        {:capitalized_alias, violations} ->
          """
          Terms for properties should be lowercased, but the following aliases for
          properties are capitalized:

          - #{alias_violations.(violations)}

          """

        {:lowercased_alias, violations} ->
          """
          Terms for non-property resource should be capitalized, but the following
          aliases for non-properties are lowercased:

          - #{alias_violations.(violations)}

          """
      end)
      |> Enum.join()

    raise RDF.Namespace.InvalidTermError, """
    Case violations detected

    #{violation_error_lines}
    You have the following options:

    - if you are in control of the vocabulary, consider renaming the resource
    - define a properly cased alias with the :alias option on defvocab
    - change the handling of case violations with the :case_violations option on defvocab
    - ignore the resource with the :ignore option on defvocab
    """
  end

  defp handle_case_violations(violations, :warn, terms, base_iri, _) do
    for {type, violations} <- violations,
        {term, original} <- violations do
      case_violation_warning(type, term, original, base_iri)
    end

    terms
  end

  defp case_violation_warning(:capitalized_term, term, _, base_iri) do
    IO.warn("'#{term_to_iri(base_iri, term)}' is a capitalized property")
  end

  defp case_violation_warning(:lowercased_term, term, _, base_iri) do
    IO.warn("'#{term_to_iri(base_iri, term)}' is a lowercased non-property resource")
  end

  defp case_violation_warning(:capitalized_alias, term, _, _) do
    IO.warn("capitalized alias '#{term}' for a property")
  end

  defp case_violation_warning(:lowercased_alias, term, _, _) do
    IO.warn("lowercased alias '#{term}' for a non-property resource")
  end

  defp filename!(opts) do
    if filename = Keyword.get(opts, :file) do
      cond do
        File.exists?(filename) ->
          filename

        File.exists?(expanded_filename = Path.expand(filename, @vocabs_dir)) ->
          expanded_filename

        true ->
          raise File.Error, path: filename, action: "find", reason: :enoent
      end
    end
  end

  defp rdf_data_env do
    import RDF.Sigils, warn: false
    __ENV__
  end

  defp rdf_data_vocab_terms(data, base_iri) do
    data
    |> RDF.Data.resources()
    |> Stream.filter(fn
      %RDF.IRI{} -> true
      _ -> false
    end)
    |> Stream.map(&to_string/1)
    |> Stream.map(&strip_base_iri(&1, base_iri))
    |> Stream.filter(&vocab_term?/1)
    |> Enum.map(&String.to_atom/1)
  end

  defp group_terms_by_case(terms) do
    terms
    |> Enum.group_by(fn {term, _} ->
      if downcase?(term),
        do: :lowercased,
        else: :capitalized
    end)
    |> Map.new(fn {group, term_mapping} ->
      {group, Map.new(term_mapping)}
    end)
  end

  defp strip_base_iri(iri, base_iri) do
    if String.starts_with?(iri, base_iri) do
      String.replace_prefix(iri, base_iri, "")
    end
  end

  defp vocab_term?(""), do: false

  defp vocab_term?(term) when is_binary(term) do
    not String.contains?(term, "/")
  end

  defp vocab_term?(_), do: false

  @doc false
  @spec term_to_iri(String.t(), String.t() | atom) :: RDF.IRI.t()
  def term_to_iri(base_iri, term) when is_atom(term),
    do: term_to_iri(base_iri, Atom.to_string(term))

  def term_to_iri(base_iri, term),
    do: RDF.iri(base_iri <> term)

  @doc false
  @spec vocabulary_namespace?(module) :: boolean
  def vocabulary_namespace?(name) do
    case Code.ensure_compiled(name) do
      {:module, name} -> function_exported?(name, :__base_iri__, 0)
      _ -> false
    end
  end
end