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