defmodule AntlDateTimeUtils.Ecto.Changeset do
  @moduledoc """
  Utils for Ecto.Changeset around DateTime
  """

  import Ecto.Changeset

  alias AntlDateTimeUtils.Comparison
  alias AntlDateTimeUtils.Period

  @spec validate_datetime_lt(Ecto.Changeset.t(), atom, atom | nil | DateTime.t(), keyword) ::
          Ecto.Changeset.t()
  def validate_datetime_lt(changeset, datetime_key, referal, opts \\ [])

  def validate_datetime_lt(
        %Ecto.Changeset{} = changeset,
        datetime_key,
        referal_datetime_key,
        opts
      )
      when is_atom(datetime_key) and is_atom(referal_datetime_key) and
             not is_nil(referal_datetime_key) do
    opts = Keyword.put_new(opts, :message, "should be before #{referal_datetime_key}")

    {_, referal_datetime} = fetch_field(changeset, referal_datetime_key)

    validate_datetime_lt(changeset, datetime_key, referal_datetime, opts)
  end

  def validate_datetime_lt(
        %Ecto.Changeset{} = changeset,
        datetime_key,
        referal_datetime,
        opts
      )
      when is_atom(datetime_key) do
    message = Keyword.get(opts, :message, "should be before #{referal_datetime}")

    {_, datetime} = fetch_field(changeset, datetime_key)

    if datetime_lt?(datetime, referal_datetime) do
      changeset
    else
      changeset |> add_error(datetime_key, message)
    end
  end

  @spec validate_datetime_lte(Ecto.Changeset.t(), atom, atom | nil | DateTime.t(), keyword) ::
          Ecto.Changeset.t()
  def validate_datetime_lte(changeset, datetime_key, referal, opts \\ [])

  def validate_datetime_lte(
        %Ecto.Changeset{} = changeset,
        datetime_key,
        referal_datetime_key,
        opts
      )
      when is_atom(datetime_key) and is_atom(referal_datetime_key) and
             not is_nil(referal_datetime_key) do
    opts = Keyword.put_new(opts, :message, "should be before or equal to #{referal_datetime_key}")

    {_, referal_datetime} = fetch_field(changeset, referal_datetime_key)

    validate_datetime_lte(changeset, datetime_key, referal_datetime, opts)
  end

  def validate_datetime_lte(%Ecto.Changeset{} = changeset, datetime_key, referal_datetime, opts)
      when is_atom(datetime_key) do
    message = Keyword.get(opts, :message, "should be before or equal to #{referal_datetime}")

    {_, datetime} = fetch_field(changeset, datetime_key)

    if datetime_lte?(datetime, referal_datetime) do
      changeset
    else
      changeset |> add_error(datetime_key, message)
    end
  end

  @spec validate_datetime_gt(Ecto.Changeset.t(), atom() | nil | DateTime.t(), atom(), keyword) ::
          Ecto.Changeset.t()
  def validate_datetime_gt(changeset, datetime_key, referal, opts \\ [])

  def validate_datetime_gt(
        %Ecto.Changeset{} = changeset,
        datetime_key,
        referal_datetime_key,
        opts
      )
      when is_atom(datetime_key) and is_atom(referal_datetime_key) and
             not is_nil(referal_datetime_key) do
    opts = Keyword.put_new(opts, :message, "should be after #{referal_datetime_key}")

    {_, referal_datetime} = fetch_field(changeset, referal_datetime_key)

    validate_datetime_gt(changeset, datetime_key, referal_datetime, opts)
  end

  def validate_datetime_gt(%Ecto.Changeset{} = changeset, datetime_key, referal_datetime, opts)
      when is_atom(datetime_key) do
    message = Keyword.get(opts, :message, "should be after #{referal_datetime}")

    {_, datetime} = fetch_field(changeset, datetime_key)

    if datetime_gt?(datetime, referal_datetime) do
      changeset
    else
      changeset |> add_error(datetime_key, message)
    end
  end

  @spec validate_datetime_gte(Ecto.Changeset.t(), atom() | nil | DateTime.t(), atom(), keyword) ::
          Ecto.Changeset.t()
  def validate_datetime_gte(changeset, datetime_key, referal, opts \\ [])

  def validate_datetime_gte(
        %Ecto.Changeset{} = changeset,
        datetime_key,
        referal_datetime_key,
        opts
      )
      when is_atom(datetime_key) and is_atom(referal_datetime_key) and
             not is_nil(referal_datetime_key) do
    opts = Keyword.put_new(opts, :message, "should be after or equal to #{referal_datetime_key}")

    {_, referal_datetime} = fetch_field(changeset, referal_datetime_key)

    validate_datetime_gte(changeset, datetime_key, referal_datetime, opts)
  end

  def validate_datetime_gte(%Ecto.Changeset{} = changeset, datetime_key, referal_datetime, opts)
      when is_atom(datetime_key) do
    message = Keyword.get(opts, :message, "should be after or equal to #{referal_datetime}")

    {_, datetime} = fetch_field(changeset, datetime_key)

    if datetime_gte?(datetime, referal_datetime) do
      changeset
    else
      changeset |> add_error(datetime_key, message)
    end
  end

  @spec validate_datetime_inclusion(Ecto.Changeset.t(), atom, atom, map, atom, atom) ::
          Ecto.Changeset.t()
  def validate_datetime_inclusion(
        %Ecto.Changeset{} = changeset,
        start_at_key,
        end_at_key,
        period,
        period_start_at_key,
        period_end_at_key
      )
      when is_atom(period_start_at_key) and is_atom(period_end_at_key) do
    container_period = %{
      start_at: Map.get(period, period_start_at_key),
      end_at: Map.get(period, period_end_at_key)
    }

    validate_datetime_inclusion(changeset, start_at_key, end_at_key, container_period)
  end

  @spec validate_datetime_inclusion(Ecto.Changeset.t(), atom, atom, Period.t()) ::
          Ecto.Changeset.t()
  def validate_datetime_inclusion(%Ecto.Changeset{} = changeset, _, _, %{
        start_at: nil,
        end_at: nil
      }) do
    changeset
  end

  def validate_datetime_inclusion(
        %Ecto.Changeset{} = changeset,
        start_at_key,
        end_at_key,
        %{start_at: _, end_at: _} = container_period
      )
      when is_atom(start_at_key) and is_atom(end_at_key) do
    {_, included_start_at} = fetch_field(changeset, start_at_key)
    {_, included_end_at} = fetch_field(changeset, end_at_key)

    included_period = %{start_at: included_start_at, end_at: included_end_at}

    unless Period.included?(included_period, container_period) do
      changeset
      |> add_error(
        start_at_key,
        "#{start_at_key} and #{end_at_key} are out of bound [#{container_period.start_at}, #{
          container_period.end_at
        }]"
      )
    else
      changeset
    end
  end

  defp datetime_gt?(nil, nil), do: true
  defp datetime_gt?(_, nil), do: false
  defp datetime_gt?(nil, %DateTime{}), do: true

  defp datetime_gt?(%DateTime{} = end_at, %DateTime{} = start_at),
    do: Comparison.gt?(end_at, start_at)

  defp datetime_gte?(nil, nil), do: true
  defp datetime_gte?(_, nil), do: false
  defp datetime_gte?(nil, %DateTime{}), do: true

  defp datetime_gte?(%DateTime{} = end_at, %DateTime{} = start_at),
    do: Comparison.gte?(end_at, start_at)

  defp datetime_lt?(nil, nil), do: true
  defp datetime_lt?(_, nil), do: true
  defp datetime_lt?(nil, %DateTime{}), do: false

  defp datetime_lt?(%DateTime{} = end_at, %DateTime{} = start_at),
    do: Comparison.lt?(end_at, start_at)

  defp datetime_lte?(nil, nil), do: true
  defp datetime_lte?(_, nil), do: true
  defp datetime_lte?(nil, %DateTime{}), do: false

  defp datetime_lte?(%DateTime{} = end_at, %DateTime{} = start_at),
    do: Comparison.lte?(end_at, start_at)
end