subaru

defmodule Subaru.Query.Builder do
  @moduledoc """
  A pipe-friendly DSL for building `Subaru.Query` structs.

  This module is intended to be used via the alias `Q`.
  """
  alias Subaru.Query

  @doc """
  Starts a query from a set of vertices.
  """
  def v(schema, filters \\ []) do
    %Query{source: {schema, filters}}
  end

  @doc """
  Adds a step to traverse outgoing edges of the given type.
  """
  def out(%Query{} = query, etype) when is_atom(etype) do
    %{query | steps: query.steps ++ [{:out, etype}]}
  end

  @doc """
  Adds a step to traverse incoming edges of the given type.
  """
  def unquote(:in)(%Query{} = query, etype) when is_atom(etype) do
    %{query | steps: query.steps ++ [{:in, etype}]}
  end

  @doc """
  Adds a step to filter results.
  """
  def filter(%Query{} = query, fun) when is_function(fun, 1) do
    %{query | steps: query.steps ++ [{:filter, fun}]}
  end

  @doc """
  Limits the number of results.
  """
  def limit(%Query{} = query, n) when is_integer(n) do
    %Query{query | limit: n}
  end

  def v(plan_or_graph, label_or_module, opts)
      when is_struct(plan_or_graph, Query) or is_map(plan_or_graph) do
    v(label_or_module, opts)
  end
end