HELP := "
    wrap: A tool for wrapping lines of text

    usage: wrap [--help] [files...] [--width=80] [--inplace=no] [--min_split=3] [--no-rewrap] [--hyphen='-']
        --help: Print this message and exit
        [files...]: The files to wrap (stdin is used if no files are provided)
        --width=N: The width to wrap the text
        --inplace: Whether or not to perform the modification in-place or print the output
        --min-split=N: The minimum amount of text on either end of a hyphenation split
        --rewrap|--no-rewrap: Whether to rewrap text that is already wrapped or only split long lines
        --hyphen='-': The text to use for hyphenation
"

UNICODE_HYPHEN := "\{hyphen}"

func unwrap(text:Text, preserve_paragraphs=yes, hyphen=UNICODE_HYPHEN -> Text)
    if preserve_paragraphs
        paragraphs := text.split($/{2+ nl}/)
        if paragraphs.length > 1
            return "\n\n".join([unwrap(p, hyphen=hyphen, preserve_paragraphs=no) for p in paragraphs])

    return text.replace("$(hyphen)\n", "")

func wrap(text:Text, width:Int, min_split=3, hyphen="-" -> Text)
    if width <= 0
        fail("Width must be a positive integer, not $width")

    if 2*min_split - hyphen.length > width
        fail("
            Minimum word split length ($min_split) is too small for the given wrap width ($width)!

            I can't fit a $(2*min_split - hyphen.length)-wide word on a line without splitting it,
        ... and I can't split it without splitting into chunks smaller than $min_split.
        ")

    lines : @[Text]
    line := ""
    for word in text.split($/{whitespace}/)
        letters := word.split()
        skip if letters.length == 0

        while not _can_fit_word(line, letters, width)
            line_space := width - line.length
            if line != "" then line_space -= 1

            if min_split > 0 and line_space >= min_split + hyphen.length and letters.length >= 2*min_split
                # Split word with a hyphen:
                split := line_space - hyphen.length
                split = split _max_ min_split
                split = split _min_ (letters.length - min_split)
                if line != "" then line ++= " "
                line ++= ((++: letters.to(split)) or "") ++ hyphen
                letters = letters.from(split + 1)
            else if line == ""
                # Force split word without hyphenation:
                if line != "" then line ++= " "
                line ++= (++: letters.to(line_space)) or ""
                letters = letters.from(line_space + 1)
            else
                pass # Move to next line

            lines.insert(line)
            line = ""

        if letters.length > 0
            if line != "" then line ++= " "
            line ++= (++: letters) or ""

    if line != ""
        lines.insert(line)

    return "\n".join(lines)

func _can_fit_word(line:Text, letters:[Text], width:Int -> Bool; inline)
    if line == ""
        return letters.length <= width
    else
        return line.length + 1 + letters.length <= width

func main(files:[Path], width=80, inplace=no, min_split=3, rewrap=yes, hyphen=UNICODE_HYPHEN)
    if files.length == 0
        files = [(/dev/stdin)]

    for file in files
        text := file.read() or exit("Could not read file: $file")

        if rewrap
            text = unwrap(text)

        out := if file.is_file() and inplace
            file
        else
            (/dev/stdout)

        first := yes
        wrapped_paragraphs : @[Text]
        for paragraph in text.split($/{2+ nl}/)
            wrapped_paragraphs.insert(
                wrap(paragraph, width=width, min_split=min_split, hyphen=hyphen)
            )

        out.write("\n\n".join(wrapped_paragraphs[]) ++ "\n")