defmodule MvWeb.MemberLive.Index.DatePresets do
  @moduledoc """
  Relative date-range presets for the date value controls (§1.25/§2.8).

  Each preset resolves against a reference date "today" into a concrete
  `%{from: Date.t(), to: Date.t()}` range. Rolling "last N days/months" presets
  end on today; the "this month/quarter/year" presets run period-to-date from
  the respective period start up to today. Resolving is pure and clock-free —
  the caller passes `today` (defaulting to `Date.utc_today/0`), so the resolved
  bounds are testable and reproducible.

  The resolved bounds feed the same `jd_*` / `ed_*` / `cdf_*` URL params as an
  absolute custom range; presets are purely an input convenience and add no new
  persistence dimension.
  """

  @type preset ::
          :last_7_days
          | :last_30_days
          | :last_3_months
          | :last_12_months
          | :this_month
          | :this_quarter
          | :this_year

  @type range :: %{from: Date.t(), to: Date.t()}

  @presets [
    :last_7_days,
    :last_30_days,
    :last_3_months,
    :last_12_months,
    :this_month,
    :this_quarter,
    :this_year
  ]

  @doc """
  Returns every preset key in display order (rolling windows first, then the
  period-to-date presets), for rendering the preset radio list.
  """
  @spec all() :: [preset()]
  def all, do: @presets

  @doc """
  Whether `key` names a known preset.
  """
  @spec preset?(term()) :: boolean()
  def preset?(key), do: key in @presets

  @doc """
  Resolves a preset to a concrete `{from, to}` range relative to `today`
  (default `Date.utc_today/0`).
  """
  @spec resolve(preset(), Date.t()) :: range()
  def resolve(preset, today \\ Date.utc_today())

  def resolve(:last_7_days, today), do: %{from: Date.add(today, -6), to: today}
  def resolve(:last_30_days, today), do: %{from: Date.add(today, -29), to: today}
  def resolve(:last_3_months, today), do: %{from: Date.shift(today, month: -3), to: today}
  def resolve(:last_12_months, today), do: %{from: Date.shift(today, month: -12), to: today}
  def resolve(:this_month, today), do: %{from: %{today | day: 1}, to: today}

  def resolve(:this_quarter, today) do
    first_month = div(today.month - 1, 3) * 3 + 1
    %{from: Date.new!(today.year, first_month, 1), to: today}
  end

  def resolve(:this_year, today), do: %{from: Date.new!(today.year, 1, 1), to: today}
end