defmodule AshPostgres.Repo do
  @moduledoc """
  Resources that use the `AshPostgres` data layer use a `Repo` to access the database.

  This repo is a slightly modified version of an `Ecto.Repo`.

  You can use `Ecto.Repo`'s `init/2` to configure your repo like normal, but
  instead of returning `{:ok, config}`, use `super(config)` to pass the
  configuration to the `AshPostgres.Repo` implementation.

  ## Installed Extensions

  To configure your list of installed extensions, define `installed_extensions/0`

  Extensions that are relevant to ash_postgres:

  * "ash-functions" - This isn't really an extension, but it expresses that certain functions
    should be added when generating migrations, to support the `||` and `&&` operators in expressions.
  * `"uuid-ossp"` - Sets UUID primary keys defaults in the migration generator
  * `"pg_trgm"` - Makes the `AshPostgres.Predicates.Trigram` custom predicate available
  * "citext" - Allows case insensitive fields to be used

  ```
  def installed_extensions() do
    ["pg_trgm", "uuid-ossp"]
  end
  ```
  """

  @doc "Use this to inform the data layer about what extensions are installed"
  @callback installed_extensions() :: [String.t()]
  @doc "Return a list of all schema names (only relevant for a multitenant implementation)"
  @callback all_tenants() :: [String.t()]
  @doc "The path where your tenant migrations are stored (only relevant for a multitenant implementation)"
  @callback tenant_migrations_path() :: String.t()
  @doc "The path where your migrations are stored"
  @callback migrations_path() :: String.t()
  @doc "The default prefix(postgres schema) to use when building queries"
  @callback default_prefix() :: String.t()
  @doc "Allows overriding a given migration type for *all* fields, for example if you wanted to always use :timestamptz for :utc_datetime fields"
  @callback override_migration_type(atom) :: atom

  defmacro __using__(opts) do
    quote bind_quoted: [opts: opts] do
      otp_app = opts[:otp_app] || raise("Must configure OTP app")

      use Ecto.Repo,
        adapter: Ecto.Adapters.Postgres,
        otp_app: otp_app

      def installed_extensions, do: []
      def tenant_migrations_path, do: nil
      def migrations_path, do: nil
      def default_prefix, do: "public"
      def override_migration_type(type), do: type

      def all_tenants do
        raise """
        `#{inspect(__MODULE__)}.all_tenants/0` was called, but was not defined. In order to migrate tenants, you must define this function.
        For example, you might say:

          def all_tenants do
            for org <- MyApp.Accounts.all_organizations!() do
              org.schema
            end
          end
        """
      end

      def init(_, config) do
        new_config =
          config
          |> Keyword.put(:installed_extensions, installed_extensions())
          |> Keyword.put(:tenant_migrations_path, tenant_migrations_path())
          |> Keyword.put(:migrations_path, migrations_path())
          |> Keyword.put(:default_prefix, default_prefix())

        {:ok, new_config}
      end

      defoverridable init: 2,
                     installed_extensions: 0,
                     all_tenants: 0,
                     tenant_migrations_path: 0,
                     default_prefix: 0,
                     override_migration_type: 1
    end
  end
end