defmodule Mobilizon.Service.Formatter.Text do @moduledoc """ Helps to format text blocks Inspired from https://elixirforum.com/t/is-there-are-text-wrapping-library-for-elixir/21733/4 Using the Knuth-Plass Line Wrapping Algorithm https://www.students.cs.ubc.ca/~cs-490/2015W2/lectures/Knuth.pdf """ def quote_paragraph(string, max_line_length) do paragraph(string, max_line_length, "> ") end def paragraph(string, max_line_length, prefix \\ "") do string |> String.split("\n\n", trim: true) |> Enum.map_join("\n#{prefix}\n", &subparagraph(&1, max_line_length, prefix)) end defp subparagraph(string, max_line_length, prefix) do [word | rest] = String.split(string, ~r/\s+/, trim: true) rest |> lines_assemble(max_line_length - String.length(prefix), String.length(word), word, []) |> Enum.map_join("\n", &"#{prefix}#{&1}") end defp lines_assemble([], _, _, line, acc), do: [line | acc] |> Enum.reverse() defp lines_assemble([word | rest], max, line_length, line, acc) do if line_length + 1 + String.length(word) > max do lines_assemble(rest, max, String.length(word), word, [line | acc]) else lines_assemble(rest, max, line_length + 1 + String.length(word), line <> " " <> word, acc) end end end