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package readline
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type SegmentCompleter interface {
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	// a
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	// |- a1
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	// |--- a11
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	// |- a2
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	// b
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	// input:
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	//   DoTree([], 0) [a, b]
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	//   DoTree([a], 1) [a]
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	//   DoTree([a, ], 0) [a1, a2]
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	//   DoTree([a, a], 1) [a1, a2]
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	//   DoTree([a, a1], 2) [a1]
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	//   DoTree([a, a1, ], 0) [a11]
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	//   DoTree([a, a1, a], 1) [a11]
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	DoSegment([][]rune, int) [][]rune
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}
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type dumpSegmentCompleter struct {
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	f func([][]rune, int) [][]rune
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}
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func (d *dumpSegmentCompleter) DoSegment(segment [][]rune, n int) [][]rune {
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	return d.f(segment, n)
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}
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func SegmentFunc(f func([][]rune, int) [][]rune) AutoCompleter {
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	return &SegmentComplete{&dumpSegmentCompleter{f}}
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}
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func SegmentAutoComplete(completer SegmentCompleter) *SegmentComplete {
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	return &SegmentComplete{
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		SegmentCompleter: completer,
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	}
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}
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type SegmentComplete struct {
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	SegmentCompleter
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}
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func RetSegment(segments [][]rune, cands [][]rune, idx int) ([][]rune, int) {
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	ret := make([][]rune, 0, len(cands))
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	lastSegment := segments[len(segments)-1]
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	for _, cand := range cands {
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		if !runes.HasPrefix(cand, lastSegment) {
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			continue
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		}
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		ret = append(ret, cand[len(lastSegment):])
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	}
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	return ret, idx
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}
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func SplitSegment(line []rune, pos int) ([][]rune, int) {
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	segs := [][]rune{}
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	lastIdx := -1
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	line = line[:pos]
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	pos = 0
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	for idx, l := range line {
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		if l == ' ' {
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			pos = 0
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			segs = append(segs, line[lastIdx+1:idx])
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			lastIdx = idx
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		} else {
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			pos++
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		}
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	}
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	segs = append(segs, line[lastIdx+1:])
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	return segs, pos
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}
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func (c *SegmentComplete) Do(line []rune, pos int) (newLine [][]rune, offset int) {
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	segment, idx := SplitSegment(line, pos)
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	cands := c.DoSegment(segment, idx)
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	newLine, offset = RetSegment(segment, cands, idx)
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	for idx := range newLine {
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		newLine[idx] = append(newLine[idx], ' ')
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	}
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	return newLine, offset
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}
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