defmodule MapSorter do
@moduledoc """
Sorts a list of `maps` per a list of `sort specs`.
Also supports:
- keywords
- structs implementing the [Access](https://hexdocs.pm/elixir/Access.html)
behaviour
- nested maps, keywords or structs implementing the
[Access](https://hexdocs.pm/elixir/Access.html) behaviour
"""
alias __MODULE__.{Log, SortSpecs}
@doc """
Sorts `maps` per the given `sort specs` (compile time or runtime).
Examples of `sort specs` for flat data structures:
```
- implicit: [:dob, :name]
- mixed: [:dob, desc: :name]
- explicit: [asc: :dob, desc: :name]
```
Examples of `sort specs` with a `Date` key for flat data structures:
```
- implicit: [{:dob Date}, :name]
- mixed: [{:dob Date}, desc: :name]
- explicit: [asc: {:dob Date}, desc: :name]
```
Examples of `sort specs` for nested data structures:
```
- implicit: [[:birth, :date], :name]
- mixed : [[:birth, :date], desc: :name]
- explicit: [asc: [:birth, :date], desc: :name]
```
Examples of `sort specs` with a `Date` key for nested data structures:
```
- implicit: [{[:birth, :date], Date}, :name]
- mixed: [{[:birth, :date], Date}, desc: :name]
- explicit: [asc: {[:birth, :date], Date}, desc: :name]
```
## Examples
iex> require MapSorter
iex> people = [
...> %{name: "Mike", likes: "movies" , dob: "1992-04-15"},
...> %{name: "Mary", likes: "travels", dob: "1992-04-15"},
...> %{name: "Bill", likes: "karate" , dob: "1977-08-28"},
...> %{name: "Joe" , likes: "boxing" , dob: "1977-08-28"},
...> %{name: "Jill", likes: "cooking", dob: "1976-09-28"}
...> ]
iex> sort_specs = Tuple.to_list({:dob, {:desc, :likes}})
iex> sorted_people = %{
...> explicit: MapSorter.sort(people, asc: :dob, desc: :likes),
...> mixed: MapSorter.sort(people, [:dob, desc: :likes]),
...> runtime: MapSorter.sort(people, sort_specs)
...> }
iex> sorted_people.explicit == sorted_people.mixed and
...> sorted_people.explicit == sorted_people.runtime and
...> sorted_people.explicit
[
%{name: "Jill", likes: "cooking", dob: "1976-09-28"},
%{name: "Bill", likes: "karate" , dob: "1977-08-28"},
%{name: "Joe" , likes: "boxing" , dob: "1977-08-28"},
%{name: "Mary", likes: "travels", dob: "1992-04-15"},
%{name: "Mike", likes: "movies" , dob: "1992-04-15"}
]
"""
defmacro sort(maps, sort_specs) do
specs =
case sort_specs do
specs when is_list(specs) ->
# [asc: {:dob, {:__aliases__, [line: 7], [:Date]}}] =>
# [asc: {:dob, Date}]
{specs, []} = Code.eval_quoted(specs)
specs
specs ->
# In case any module attributes...
Macro.expand(specs, __CALLER__)
end
:ok = Log.debug(:sort_specs, {sort_specs, specs, __ENV__, __CALLER__})
case SortSpecs.to_quoted(specs) do
{:ok, fun_ast} ->
quote do: Enum.sort(unquote(maps), unquote(fun_ast))
{:error, invalid_specs} ->
:ok = Log.error(:invalid_specs, {invalid_specs, __ENV__, __CALLER__})
maps
end
end
end