defmodule Polyn.SchemaStore do
  # Persisting and interacting with persisted schemas
  @moduledoc false

  alias Jetstream.API.KV

  @store_name "POLYN_SCHEMAS"

  @doc """
  Persist a schema. In prod/dev schemas should have already been persisted via
  the Polyn CLI.
  """
  @spec save(conn :: Gnat.t(), type :: binary(), schema :: map()) :: :ok
  @spec save(conn :: Gnat.t(), type :: binary(), schema :: map(), opts :: keyword()) :: :ok
  def save(conn, type, schema, opts \\ []) when is_map(schema) do
    is_json_schema?(schema)
    KV.create_key(conn, store_name(opts), type, encode(schema))
  end

  defp is_json_schema?(schema) do
    ExJsonSchema.Schema.resolve(schema)
  rescue
    ExJsonSchema.Schema.InvalidSchemaError ->
      reraise Polyn.SchemaException,
              [message: "Schemas must be valid JSONSchema documents, got #{inspect(schema)}"],
              __STACKTRACE__
  end

  defp encode(schema) do
    case Jason.encode(schema) do
      {:ok, encoded} -> encoded
      {:error, reason} -> raise Polyn.SchemaException, inspect(reason)
    end
  end

  @doc """
  Remove a schema
  """
  @spec delete(conn :: Gnat.t(), type :: binary()) :: :ok
  @spec delete(conn :: Gnat.t(), type :: binary(), opts :: keyword()) :: :ok
  def delete(conn, type, opts \\ []) do
    KV.purge_key(conn, store_name(opts), type)
  end

  @doc """
  Get the schema for an event
  """
  @spec get(conn :: Gnat.t(), type :: binary()) :: nil | map()
  @spec get(conn :: Gnat.t(), type :: binary(), opts :: keyword()) :: nil | map()
  def get(conn, type, opts \\ []) do
    case KV.get_value(conn, store_name(opts), type) do
      {:error, %{"description" => "no message found"}} ->
        nil

      {:error, %{"description" => "stream not found"}} ->
        raise Polyn.SchemaException,
              "The Schema Store has not been setup on your NATS server. " <>
                "Make sure you use the Polyn CLI to create it"

      {:error, reason} ->
        raise Polyn.SchemaException, inspect(reason)

      nil ->
        nil

      schema ->
        Jason.decode!(schema)
    end
  end

  @doc """
  Create the schema store if it doesn't exist already. In prod/dev the the store
  creation should have already been done via the Polyn CLI
  """
  @spec create_store(conn :: Gnat.t()) :: :ok
  @spec create_store(conn :: Gnat.t(), opts :: keyword()) :: :ok
  def create_store(conn, opts \\ []) do
    result =
      KV.create_bucket(conn, store_name(opts),
        description: "Contains Schemas for all events on the server"
      )

    case result do
      {:ok, _info} -> :ok
      # If some other client created the store first, with a slightly different
      # description or config we'll just use the existing one
      {:error, %{"description" => "stream name already in use"}} -> :ok
      {:error, reason} -> raise Polyn.SchemaException, inspect(reason)
    end
  end

  @doc """
  Delete the schema store. Useful for test
  """
  @spec delete_store(conn :: Gnat.t()) :: :ok
  @spec delete_store(conn :: Gnat.t(), opts :: keyword()) :: :ok
  def delete_store(conn, opts \\ []) do
    KV.delete_bucket(conn, store_name(opts))
  end

  @doc """
  Get a configured store name or the default
  """
  def store_name(opts \\ []) do
    Keyword.get(opts, :name, @store_name)
  end
end