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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
import Kernel, except: [apply: 2]
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(:order_by, quote do [x.x, desc: 13] end, [x: 0], __ENV__)
{[asc: {:{}, [], [{:{}, [], [:., [], [{:{}, [], [:&, [], [0]]}, :x]]}, [], []]},
desc: 13],
%{}}
"""
@spec escape(:order_by | :distinct, Macro.t, Keyword.t, Macro.Env.t) :: Macro.t
def escape(kind, {:^, _, [expr]}, _vars, _env) do
{quote(do: Ecto.Query.Builder.OrderBy.order_by!(unquote(kind), unquote(expr))), %{}}
end
def escape(kind, expr, vars, env) do
expr
|> List.wrap
|> Enum.map_reduce(%{}, &do_escape(&1, &2, kind, vars, env))
end
defp do_escape({dir, {:^, _, [expr]}}, params, kind, _vars, _env) do
{{quoted_dir!(kind, dir), quote(do: Ecto.Query.Builder.OrderBy.field!(unquote(kind), unquote(expr)))}, params}
end
defp do_escape({:^, _, [expr]}, params, kind, _vars, _env) do
{{:asc, quote(do: Ecto.Query.Builder.OrderBy.field!(unquote(kind), unquote(expr)))}, params}
end
defp do_escape({dir, field}, params, kind, _vars, _env) when is_atom(field) do
{{quoted_dir!(kind, dir), Macro.escape(to_field(field))}, params}
end
defp do_escape(field, params, _kind, _vars, _env) when is_atom(field) do
{{:asc, Macro.escape(to_field(field))}, params}
end
defp do_escape({dir, expr}, params, kind, vars, env) do
{ast, {params, :acc}} = Builder.escape(expr, :any, {params, :acc}, vars, env)
{{quoted_dir!(kind, dir), ast}, params}
end
defp do_escape(expr, params, _kind, vars, env) do
{ast, {params, :acc}} = Builder.escape(expr, :any, {params, :acc}, 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!(kind, {:^, _, [expr]}),
do: quote(do: Ecto.Query.Builder.OrderBy.dir!(unquote(kind), unquote(expr)))
def quoted_dir!(_kind, dir) when dir in [:asc, :desc],
do: dir
def quoted_dir!(kind, other),
do: Builder.error!("expected :asc, :desc or interpolated value in `#{kind}`, got: `#{inspect other}`")
@doc """
Called by at runtime to verify the direction.
"""
def dir!(_kind, dir) when dir in [:asc, :desc],
do: dir
def dir!(kind, other),
do: Builder.error!("expected :asc or :desc in `#{kind}`, got: `#{inspect other}`")
@doc """
Called at runtime to verify a field.
"""
def field!(_kind, field) when is_atom(field) do
to_field(field)
end
def field!(kind, other) do
raise ArgumentError,
"expected a field as an atom, a list or keyword list in `#{kind}`, got: `#{inspect other}`"
end
@doc """
Called at runtime to verify order_by.
"""
def order_by!(kind, exprs) do
Enum.map List.wrap(exprs), fn
{dir, field} when dir in [:asc, :desc] ->
{dir, field!(kind, field)}
field ->
{:asc, field!(kind, field)}
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
{query, binding} = Builder.escape_binding(query, binding)
{expr, params} = escape(:order_by, 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(%Ecto.Query{order_bys: order_bys} = query, expr) do
%{query | order_bys: order_bys ++ [expr]}
end
def apply(query, expr) do
apply(Ecto.Queryable.to_query(query), expr)
end
end