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map_sorter
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Sorts a list of maps per a list of sort specs.
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lib/map_sorter.ex
defmodule MapSorter do
@moduledoc """
Sorts a list of `maps` as per a list of `sort specs`
(ascending/descending keys).
Also supports:
- keywords
- structs implementing the Access behaviour
- nested maps, keywords or structs implementing the Access behaviour
"""
alias MapSorter.SortSpec
require Logger
@doc """
Sorts `maps` as per the given `sort specs` (compile time or runtime).
Examples of `sort specs` for flat data structures:
- implicit: [:dob, :name] ≡ [_asc:_ :dob, _asc:_ :name]
- mixed: [:dob, desc: :name] ≡ [_asc:_ :dob, desc: :name]
- explicit: [asc: :dob, 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
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 = [: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
Logger.debug("sort specs: #{inspect(sort_specs)}...")
specs =
case sort_specs do
specs when is_list(specs) -> specs
specs -> Macro.expand(specs, __CALLER__) # in case module attribute
end
case SortSpec.to_quoted(specs) do
{:ok, comp_fun} -> quote do: Enum.sort(unquote(maps), unquote(comp_fun))
{:error, bad_specs} ->
Logger.warn("bad sort specs: #{inspect(bad_specs)}")
maps
end
end
# @doc """
# Allows to change the log `level` at compile time.
# """
@doc false
defmacro log_level(level), do: Logger.configure(level: level)
end