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module txtar
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// Ported from https://cs.opensource.google/go/x/tools/+/master:txtar/archive.go
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import strings
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// Archive is a collection of files
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pub struct Archive {
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pub mut:
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	comment string // the start of the archive; contains potentially multiple lines, before the files
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	files   []File // a series of files
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}
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// File is a single file in an Archive. Each starting with a `-- FILENAME --` line.
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pub struct File {
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pub mut:
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	path    string // 'abc/def.v' from the `-- abc/def.v --` header
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	content string // everything after that, till the next `-- name --` line.
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}
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// str returns a string representation of the `a` Archive.
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// It is suitable for storing in a text file.
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// It is also in the same format, that txtar.parse/1 expects.
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pub fn (a &Archive) str() string {
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	mut sb := strings.new_builder(a.comment.len + 200 * a.files.len)
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	sb.write_string(fix_nl(a.comment))
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	for f in a.files {
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		sb.write_string('-- ${f.path} --\n')
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		sb.write_string(fix_nl(f.content))
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	}
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	return sb.str()
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}
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// parse parses the serialized form of an Archive.
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// The returned Archive holds slices of data.
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pub fn parse(content string) Archive {
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	mut a := Archive{}
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	comment, mut name, mut data := find_file_marker(content)
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	a.comment = comment
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	for name != '' {
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		mut f := File{name, ''}
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		f.content, name, data = find_file_marker(data)
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		a.files << f
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	}
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	return a
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}
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const nlm = '\n-- '
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const mstart = '-- '
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const mend = ' --'
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// find_file_marker finds the next file marker in data, extracts the file name,
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// and returns the data before the marker, the file name, and the data after the marker.
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// If there is no next marker, find_file_marker returns fixNL(data), '', ''.
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fn find_file_marker(data string) (string, string, string) {
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	mut i := 0
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	for i < data.len {
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		name, after := is_marker(data[i..])
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		if name != '' {
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			return data[..i], name, after
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		}
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		j := data[i..].index(nlm) or { return fix_nl(data), '', '' }
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		i += j + 1 // positioned at start of new possible marker
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	}
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	return '', '', ''
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}
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// is_marker checks whether the data begins with a file marker line.
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// If so, it returns the name from the line, and the data after the line.
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// Otherwise it returns name == "".
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fn is_marker(data string) (string, string) {
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	if !data.starts_with(mstart) {
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		return '', ''
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	}
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	mut ndata := data
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	mut after := ''
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	i := data.index_u8(`\n`)
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	if i >= 0 {
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		ndata, after = data[..i], data[i + 1..]
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	}
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	if !(ndata.ends_with(mend) && ndata.len >= mstart.len + mend.len) {
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		return '', ''
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	}
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	name := ndata[mstart.len..ndata.len - mend.len].trim_space()
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	return name, after
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}
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// fix_nl returns the data, if it is empty, or if it ends in \n.
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// Otherwise it returns data + a final \n added.
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fn fix_nl(data string) string {
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	if data.len == 0 || data[data.len - 1] == `\n` {
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		return data
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	}
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	return '${data}\n'
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}
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