combinations.ex
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	# Pleroma: A lightweight social networking server
	# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
	# SPDX-License-Identifier: AGPL-3.0-only

	defmodule Pleroma.Emoji.Combinations do
	# FE0F is the emoji variation sequence. It is used for fully-qualifying
	# emoji, and that includes emoji combinations.
	# This code generates combinations per emoji: for each FE0F, all possible
	# combinations of the character being removed or staying will be generated.
	# This is made as an attempt to find all partially-qualified and unqualified
	# versions of a fully-qualified emoji.
	# I have found no cases for which this would be a problem, after browsing
	# the entire emoji list in emoji-test.txt. This is safe, and, sadly, most
	# likely sane too.

	defp qualification_combinations(codepoints) do
	qualification_combinations([[]], codepoints)
	end

	defp qualification_combinations(acc, []), do: acc

	defp qualification_combinations(acc, ["\uFE0F" \| tail]) do
	acc
	\|> Enum.flat_map(fn x -> [x, x ++ ["\uFE0F"]] end)
	\|> qualification_combinations(tail)
	end

	defp qualification_combinations(acc, [codepoint \| tail]) do
	acc
	\|> Enum.map(&Kernel.++(&1, [codepoint]))
	\|> qualification_combinations(tail)
	end

	def variate_emoji_qualification(emoji) when is_binary(emoji) do
	emoji
	\|> String.codepoints()
	\|> qualification_combinations()
	\|> Enum.map(&List.to_string/1)
	end

	def variate_emoji_qualification(emoji) when is_list(emoji) do
	emoji
	\|> Enum.map(fn emoji -> {emoji, variate_emoji_qualification(emoji)} end)
	end
	end