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A toolkit for data mapping and language integrated query for Elixir
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lib/ecto/query/builder/order_by.ex
defmodule Ecto.Query.Builder.OrderBy do
@moduledoc false
alias Ecto.Query.Builder
@doc """
Escapes an order by query.
The query is escaped to a list of `{direction, expression}`
pairs at runtime. Escaping also validates direction is one of
`:asc` or `:desc`.
## Examples
iex> escape(quote do [x.x, desc: 13] end, [x: 0], __ENV__)
{[asc: {:{}, [], [{:{}, [], [:., [], [{:{}, [], [:&, [], [0]]}, :x]]}, [], []]},
desc: 13],
%{}}
"""
@spec escape(Macro.t, Keyword.t, Macro.Env.t) :: Macro.t
def escape({:^, _, [expr]}, _vars, _env) do
{quote(do: Ecto.Query.Builder.OrderBy.order_by!(unquote(expr))), %{}}
end
def escape(expr, vars, env) do
List.wrap(expr)
|> Enum.map_reduce(%{}, &do_escape(&1, &2, vars, env))
end
defp do_escape({dir, {:^, _, [expr]}}, params, _vars, _env) do
{{quoted_dir!(dir), quote(do: Ecto.Query.Builder.OrderBy.field!(unquote(expr)))}, params}
end
defp do_escape({:^, _, [expr]}, params, _vars, _env) do
{{:asc, quote(do: Ecto.Query.Builder.OrderBy.field!(unquote(expr)))}, params}
end
defp do_escape({dir, field}, params, _vars, _env) when is_atom(field) do
{{quoted_dir!(dir), Macro.escape(to_field(field))}, params}
end
defp do_escape(field, params, _vars, _env) when is_atom(field) do
{{:asc, Macro.escape(to_field(field))}, params}
end
defp do_escape({dir, expr}, params, vars, env) do
{ast, params} = Builder.escape(expr, :any, params, vars, env)
{{quoted_dir!(dir), ast}, params}
end
defp do_escape(expr, params, vars, env) do
{ast, params} = Builder.escape(expr, :any, params, vars, env)
{{:asc, ast}, params}
end
@doc """
Checks the variable is a quoted direction at compilation time or
delegate the check to runtime for interpolation.
"""
def quoted_dir!({:^, _, [expr]}),
do: quote(do: Ecto.Query.Builder.OrderBy.dir!(unquote(expr)))
def quoted_dir!(dir) when dir in [:asc, :desc],
do: dir
def quoted_dir!(other),
do: Builder.error!("expected :asc, :desc or interpolated value in `order_by`, got: `#{inspect other}`")
@doc """
Called by at runtime to verify the direction.
"""
def dir!(dir) when dir in [:asc, :desc],
do: dir
def dir!(other),
do: Builder.error!("expected :asc or :desc in `order_by`, got: `#{inspect other}`")
@doc """
Called at runtime to verify a field.
"""
def field!(field) when is_atom(field),
do: to_field(field)
def field!(other),
do: Builder.error!("expected a field as an atom in `order_by`, got: `#{inspect other}`")
@doc """
Called at runtime to verify order_by.
"""
def order_by!(order_by) do
Enum.map List.wrap(order_by), fn
{dir, field} when dir in [:asc, :desc] and is_atom(field) ->
{dir, to_field(field)}
field when is_atom(field) ->
{:asc, to_field(field)}
_ ->
Builder.error!("expected a list or keyword list of fields in `order_by`, got: `#{inspect order_by}`")
end
end
defp to_field(field), do: {{:., [], [{:&, [], [0]}, field]}, [], []}
@doc """
Builds a quoted expression.
The quoted expression should evaluate to a query at runtime.
If possible, it does all calculations at compile time to avoid
runtime work.
"""
@spec build(Macro.t, [Macro.t], Macro.t, Macro.Env.t) :: Macro.t
def build(query, binding, expr, env) do
binding = Builder.escape_binding(binding)
{expr, params} = escape(expr, binding, env)
params = Builder.escape_params(params)
order_by = quote do: %Ecto.Query.QueryExpr{
expr: unquote(expr),
params: unquote(params),
file: unquote(env.file),
line: unquote(env.line)}
Builder.apply_query(query, __MODULE__, [order_by], env)
end
@doc """
The callback applied by `build/4` to build the query.
"""
@spec apply(Ecto.Queryable.t, term) :: Ecto.Query.t
def apply(query, expr) do
query = Ecto.Queryable.to_query(query)
%{query | order_bys: query.order_bys ++ [expr]}
end
end