defmodule QuackDB.Interval do
  @moduledoc """
  DuckDB interval value preserving month, day, and microsecond components.

  DuckDB stores intervals as three independent components instead of a single
  duration because months and days do not have fixed microsecond lengths.
  """

  defstruct months: 0, days: 0, microseconds: 0

  @type t :: %__MODULE__{months: integer(), days: integer(), microseconds: integer()}

  @doc "Builds a DuckDB interval value."
  @spec new(integer(), integer(), integer()) :: t()
  def new(months \\ 0, days \\ 0, microseconds \\ 0)
      when is_integer(months) and is_integer(days) and is_integer(microseconds) do
    %__MODULE__{months: months, days: days, microseconds: microseconds}
  end

  @doc "Returns the interval as `{months, days, microseconds}`."
  @spec to_tuple(t()) :: {integer(), integer(), integer()}
  def to_tuple(%__MODULE__{} = interval) do
    {interval.months, interval.days, interval.microseconds}
  end
end

if Code.ensure_loaded?(Inspect) do
  defimpl Inspect, for: QuackDB.Interval do
    import Inspect.Algebra

    def inspect(interval, opts) do
      concat([
        string("#QuackDB.Interval<"),
        to_doc(interval.months, opts),
        string(" months, "),
        to_doc(interval.days, opts),
        string(" days, "),
        to_doc(interval.microseconds, opts),
        string(" microseconds>")
      ])
    end
  end
end