query.ex

# Core.Query

defmodule Core.Query do
  @type query :: {query_name :: atom(), args :: keyword()}
  @callback composeable_query(queryable :: Ecto.Query.t(), query()) :: Ecto.Query.t()

  @spec compose(
          query :: Ecto.Query.t(),
          module :: module(),
          queries :: list(query())
        ) :: Ecto.Query.t()
  def compose(query, module, queries) do
    queries
    |> Enum.map(fn
      {_query_name, _args} = query ->
        query

      query_name ->
        {query_name, []}
    end)
    |> Enum.reduce(@schema, &__MODULE__.composeable_query/2)
  end
end

# Core.Games.Queries

defmodule Core.Games.Queries do
  @behaviour Core.Query

  @impl true
  def composeable_query(query, {:by_provider, args}), do: where(query, provider: ^args[:provider])

  @impl true
  def composeable_query(query, {:by_category, args}), do: where(query, category: ^args[:category])

  @impl true
  def composeable_query(query, {:enabled, _args}), do: where(query, enabled: true)
end

# Usage
queries = [
  {:by_category, category: "slots"},
  :enabled,
  {:by_provider, provider: "netent"}
]

Core.Games.Queries.compose(Core.Schemas.Game, Core.Games.Queries, queries)