EndLine   int
}

func (p Position) Pos() Position {
	return p
}

type buildState interface {
	blocks() []Block
	pos() Position
	last() Block
	deleteLast()

	link(label string) *Link
	defineLink(label string, link *Link)
	newText(pos Position, text string) *Text
}

type blockBuilder interface {
	extend(p *parseState, s line) (line, bool)
	build(buildState) Block
}

type openBlock struct {

	}

	// Must end line. Already trimmed spaces.
	if i < len(s) && s[i] != '\n' {
		return 0, false
	}
	if i < len(s) {
		i++
	}

	label = normalizeLabel(label)
	if p.link(label) == nil {
		p.defineLink(label, &Link{URL: dest, Title: title, TitleChar: titleChar, corner: corner})
	}
	return i, true
}

func parseLinkTitle(s string, i int) (title string, char byte, next int, found bool) {