defmodule Plausible.Funnels do
  @moduledoc """
  This module implements contextual Funnel interface, allowing listing,
  creating and deleting funnel definitions.

  For brief explanation of what a Funnel is, please see `Plausible.Funnel` schema.
  See `Plausible.Stats.Funnel` for the evaluation logic.
  """

  use Plausible.Funnel

  alias Plausible.Repo

  import Ecto.Query

  @spec create(Plausible.Site.t(), String.t(), [map()], Keyword.t()) ::
          {:ok, Funnel.t()}
          | {:error, Ecto.Changeset.t() | :invalid_funnel_size | :upgrade_required}
  def create(site, name, steps, opts \\ [])

  def create(site, name, steps, opts)
      when is_list(steps) and length(steps) in Funnel.min_steps()..Funnel.max_steps() do
    site = Plausible.Repo.preload(site, :team)

    case Plausible.Billing.Feature.Funnels.check_availability(site.team) do
      {:error, _} = error ->
        error

      :ok ->
        site
        |> create_changeset(name, steps, opts)
        |> Repo.insert()
    end
  end

  def create(_site, _name, _goals, _opts) do
    {:error, :invalid_funnel_size}
  end

  @spec update(Funnel.t(), String.t(), [map()], Keyword.t()) ::
          {:ok, Funnel.t()}
          | {:error, Ecto.Changeset.t() | :invalid_funnel_size | :upgrade_required}
  def update(funnel, name, steps, opts \\ []) do
    site = Plausible.Repo.preload(funnel, site: :team).site

    case Plausible.Billing.Feature.Funnels.check_availability(site.team) do
      {:error, _} = error ->
        error

      :ok ->
        funnel
        |> edit_changeset(name, steps,
          strict_order?: Keyword.get(opts, :strict_order?, !!funnel.strict_order)
        )
        |> Repo.update()
    end
  end

  @spec create_changeset(Plausible.Site.t(), String.t(), [map()], Keyword.t()) ::
          Ecto.Changeset.t()
  def create_changeset(site, name, steps, opts \\ []) do
    Funnel.changeset(%Funnel{site_id: site.id}, %{
      name: name,
      steps: steps,
      strict_order: Keyword.get(opts, :strict_order?, false)
    })
  end

  @spec edit_changeset(Plausible.Funnel.t(), String.t(), [map()], Keyword.t()) ::
          Ecto.Changeset.t()
  def edit_changeset(funnel, name, steps, opts) do
    Funnel.changeset(funnel, %{
      name: name,
      steps: steps,
      strict_order: Keyword.get(opts, :strict_order?, false)
    })
  end

  @spec ephemeral_definition(Plausible.Site.t(), String.t(), [map()], Keyword.t()) :: Funnel.t()
  def ephemeral_definition(site, name, steps, opts \\ []) do
    site
    |> create_changeset(name, steps, opts)
    |> Ecto.Changeset.apply_changes()
  end

  @spec list(Plausible.Site.t()) :: [
          %{name: String.t(), id: pos_integer(), steps_count: pos_integer()}
        ]
  def list(%Plausible.Site{} = site) do
    q =
      from(f in Funnel,
        inner_join: steps in assoc(f, :steps),
        where: f.site_id == ^site.id,
        group_by: f.id,
        order_by: [desc: :id],
        select: %{name: f.name, id: f.id, steps_count: count(steps)}
      )

    Repo.all(q)
  end

  @spec delete(Plausible.Site.t() | pos_integer(), pos_integer()) :: :ok
  def delete(%Plausible.Site{id: site_id}, funnel_id) do
    delete(site_id, funnel_id)
  end

  def delete(site_id, funnel_id) do
    Repo.delete_all(
      from(f in Funnel,
        where: f.site_id == ^site_id,
        where: f.id == ^funnel_id
      )
    )

    :ok
  end

  @spec get(Plausible.Site.t() | pos_integer(), pos_integer() | String.t()) ::
          Funnel.t() | nil
  def get(%Plausible.Site{id: site_id}, by) do
    get(site_id, by)
  end

  def get(site_id, funnel_name) when is_integer(site_id) and is_binary(funnel_name) do
    site_id |> base_get_query() |> where([f], f.name == ^funnel_name) |> Repo.one()
  end

  def get(site_id, funnel_id) when is_integer(site_id) and is_integer(funnel_id) do
    site_id |> base_get_query() |> where([f], f.id == ^funnel_id) |> Repo.one()
  end

  @spec with_goals_query(Plausible.Site.t()) :: Ecto.Query.t()
  def with_goals_query(site) do
    from(f in Funnel,
      inner_join: steps in assoc(f, :steps),
      where: f.site_id == ^site.id,
      group_by: f.id,
      order_by: [desc: :id],
      preload: [steps: :goal]
    )
  end

  defp base_get_query(site_id) do
    from(f in Funnel,
      where: f.site_id == ^site_id,
      inner_join: steps in assoc(f, :steps),
      inner_join: goal in assoc(steps, :goal),
      order_by: steps.step_order,
      preload: [
        steps: {steps, goal: goal}
      ]
    )
  end
end