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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