defmodule ArcadiaCloud.Subscriptions do
  @moduledoc """
  Subscriptions bind a deployment to a plan version. One subscription per
  deployment. Addons attach with their price + qty SNAPSHOTTED, so a
  later catalog price change doesn't retroactively reprice an existing
  subscriber.
  """

  import Ecto.Query, warn: false

  alias ArcadiaCloud.Repo
  alias ArcadiaCloud.Catalog
  alias ArcadiaCloud.Billing.{Subscription, SubscriptionAddon}

  @doc """
  Create a subscription for a deployment on a plan version. Period
  defaults to the current calendar month.
  """
  def create_subscription(deployment_id, plan_version_id, opts \\ []) do
    {period_start, period_end} = opts[:period] || current_month()

    %Subscription{}
    |> Subscription.changeset(%{
      deployment_id: deployment_id,
      plan_version_id: plan_version_id,
      status: opts[:status] || "active",
      current_period_start: period_start,
      current_period_end: period_end,
      trial_ends_at: opts[:trial_ends_at]
    })
    |> Repo.insert()
  end

  def get_subscription(id) do
    case Repo.get(Subscription, id) do
      nil -> nil
      sub -> Repo.preload(sub, [:addons, :plan_version])
    end
  end

  def get_subscription_for_deployment(deployment_id) do
    case Repo.get_by(Subscription, deployment_id: deployment_id) do
      nil -> nil
      sub -> Repo.preload(sub, [:addons, :plan_version])
    end
  end

  def list_active_subscriptions do
    from(s in Subscription, where: s.status == "active", preload: [:addons, :plan_version])
    |> Repo.all()
  end

  def update_subscription(%Subscription{} = sub, attrs) do
    sub
    |> Subscription.changeset(attrs)
    |> Repo.update()
  end

  @doc """
  Migrate a subscription to a different plan version (e.g. a price
  change, or an up/downgrade). The change takes effect from the next
  period unless `:immediate` is set.
  """
  def change_plan_version(%Subscription{} = sub, new_plan_version_id) do
    update_subscription(sub, %{plan_version_id: new_plan_version_id})
  end

  # ---- addons ---------------------------------------------------------------

  @doc """
  Attach an addon to a subscription, snapshotting its current price + qty.
  `addon` may be an Addon struct or an addon code string.
  """
  def attach_addon(%Subscription{id: sub_id}, addon) do
    addon = resolve_addon(addon)

    %SubscriptionAddon{}
    |> SubscriptionAddon.changeset(%{
      subscription_id: sub_id,
      addon_id: addon.id,
      resource_kind: addon.resource_kind,
      qty: addon.qty,
      price_cents: addon.price_cents,
      currency: addon.currency,
      attached_at: DateTime.utc_now() |> DateTime.truncate(:second)
    })
    |> Repo.insert()
  end

  def detach_addon(%SubscriptionAddon{} = sa), do: Repo.delete(sa)

  def list_addons(subscription_id) do
    from(sa in SubscriptionAddon, where: sa.subscription_id == ^subscription_id, preload: [:addon])
    |> Repo.all()
  end

  defp resolve_addon(%ArcadiaCloud.Catalog.Addon{} = addon), do: addon

  defp resolve_addon(code) when is_binary(code) do
    [addon] = Catalog.get_addons([code])
    addon
  end

  # ---- helpers --------------------------------------------------------------

  defp current_month do
    today = Date.utc_today()
    {Date.beginning_of_month(today), Date.end_of_month(today)}
  end
end