defmodule Ymlr do
  @moduledoc """
  Encodes data into YAML documents using the `Ymlr.Encoder`.
  Every document starts with a separator ("---") and can be enhanced with comments.
  """

  alias Ymlr.Encoder

  @type document :: Encoder.data | {binary(), Encoder.data} | {[binary()], Encoder.data}

  @doc """
  Encodes a given data as YAML document with a separator ("---") at the beginning. Raises if it cannot be encoded.

  Optinally you can pass a tuple with comment(s) and data as first argument.

  ## Examples

      iex> Ymlr.document!(%{a: 1})
      "---\\na: 1\\n"

      iex> Ymlr.document!({"comment", %{a: 1}})
      "---\\n# comment\\na: 1\\n"

      iex> Ymlr.document!({["comment 1", "comment 2"], %{a: 1}})
      "---\\n# comment 1\\n# comment 2\\na: 1\\n"

      iex> Ymlr.document!({[], {"a", "b"}})
      ** (ArgumentError) The given data {\"a\", \"b\"} cannot be converted to YAML.
  """
  @spec document!(document) :: binary()
  def document!(document)
  def document!({lines, data}) when is_list(lines) do
    comments = lines
    |> Enum.map(&("# #{&1}\n"))
    |> Enum.join("")
    "---\n" <> comments <> Encoder.to_s!(data) <> "\n"
  end
  def document!({comment, data}), do: document!({[comment], data})

  def document!(data) do
    document!({[], data})
  end

  @doc """
  Encodes a given data as YAML document with a separator ("---") at the beginning.

  Optinally you can pass a tuple with comment(s) and data as first argument.

  ## Examples

      iex> Ymlr.document(%{a: 1})
      {:ok, "---\\na: 1\\n"}

      iex> Ymlr.document({"comment", %{a: 1}})
      {:ok, "---\\n# comment\\na: 1\\n"}

      iex> Ymlr.document({["comment 1", "comment 2"], %{a: 1}})
      {:ok, "---\\n# comment 1\\n# comment 2\\na: 1\\n"}

      iex> Ymlr.document({[], {"a", "b"}})
      {:error, "The given data {\\"a\\", \\"b\\"} cannot be converted to YAML."}
  """
  @spec document(document) :: {:ok, binary()} | {:error, binary()}
  def document(document) do
    yml = document!(document)
    {:ok, yml}
  rescue
    e in ArgumentError -> {:error, e.message}
  end

  @doc """
  Encodes a given list of data as "---" separated YAML documents. Raises if it cannot be encoded.

  ## Examples

      iex> Ymlr.documents!([%{a: 1}])
      "---\\na: 1\\n"

      iex> Ymlr.documents!([%{a: 1}, %{b: 2}])
      "---\\na: 1\\n\\n---\\nb: 2\\n"

      iex> Ymlr.documents!([{[], {"a", "b"}}])
      ** (ArgumentError) The given data {\"a\", \"b\"} cannot be converted to YAML.

      iex> Ymlr.documents!(%{a: "a"})
      ** (ArgumentError) The given argument is not a list of documents. Use document/1, document/2, document!/1 or document!/2 for a single document.
  """
  def documents!(documents) when is_list(documents) do
    documents
    |> Enum.map(&document!/1)
    |> Enum.join("\n")
  end
  def documents!(_documents), do:
    raise(ArgumentError, "The given argument is not a list of documents. Use document/1, document/2, document!/1 or document!/2 for a single document.")

  @doc """
  Encodes a given list of data as "---" separated YAML documents.

  ## Examples

      iex> Ymlr.documents([%{a: 1}])
      {:ok, "---\\na: 1\\n"}

      iex> Ymlr.documents([%{a: 1}, %{b: 2}])
      {:ok, "---\\na: 1\\n\\n---\\nb: 2\\n"}

      iex> Ymlr.documents([{[], {"a", "b"}}])
      {:error, "The given data {\\"a\\", \\"b\\"} cannot be converted to YAML."}

      iex> Ymlr.documents(%{a: "a"})
      {:error, "The given argument is not a list of documents. Use document/1, document/2, document!/1 or document!/2 for a single document."}
  """
  @spec documents([document]) :: {:ok, binary()} | {:error, binary()}
  def documents(documents) do
    yml = documents!(documents)
    {:ok, yml}
  rescue
    e in ArgumentError ->
      {:error, e.message}
  end
end