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package markdown
import "fmt"
type lexerType string
const (
lexerBreak lexerType = "break"
lexerModifier lexerType = "modifier"
lexerCode lexerType = "code"
lexerHeader lexerType = "header"
lexerQuote lexerType = "quote"
lexerList lexerType = "list"
lexerExternal lexerType = "external"
lexerLiteral lexerType = "literal"
)
type lexer struct {
Type lexerType
Value string
}
func (l lexer) String() string {
return fmt.Sprintf("%s(%s)", l.Type, l.Value)
}
type lexers struct {
current int
lexers []lexer
}
func (l *lexers) Next() bool {
l.current++
return !l.Finished()
}
func (l *lexers) Current() lexer {
return l.lexers[l.current]
}
func (l *lexers) Finished() bool {
return l.current >= len(l.lexers)
}
func (l *lexers) Before() bool {
l.current--
return l.current >= 0 && !l.Finished()
}
func (l *lexers) String() string {
s := "Lexers["
for _, l := range l.lexers {
s += l.String() + " "
}
return s + "]"
}
func lex(s string) *lexers {
lxs := &lexers{current: -1}
var lexs []lexer
var currentType lexerType
var previous string
fn := func(c rune, t lexerType, validate func(rune) bool) {
if validate == nil {
validate = func(r rune) bool { return true }
}
if (currentType != t || !validate(c)) && len(previous) > 0 {
lexs = append(lexs, lexer{Type: currentType, Value: previous})
previous = ""
}
currentType = t
previous += string(c)
}
newLine := true
literalNext := false
runes := []rune(s)
for i, c := range runes {
if literalNext {
fn(c, lexerLiteral, nil)
literalNext = false
continue
}
if c == '\\' {
literalNext = true
continue
}
switch c {
case '*', '_':
if c == '*' && newLine && i < len(runes)-1 && runes[i+1] == ' ' {
fn(c, lexerList, nil)
} else {
if (currentType != lexerModifier && len(previous) > 0) ||
(len(previous) > 0 && []rune(previous)[0] != c) ||
len(previous) >= 3 {
lexs = append(lexs, lexer{Type: currentType, Value: previous})
previous = ""
}
currentType = lexerModifier
previous += string(c)
}
newLine = false
case '`':
newLine = false
fn(c, lexerCode, nil)
case '\n':
newLine = true
fn(c, lexerBreak, nil)
case '#':
newLine = false
fn(c, lexerHeader, nil)
case '>':
newLine = false
fn(c, lexerQuote, nil)
case '[', ']', '(', ')', '!':
newLine = false
fn(c, lexerExternal, func(c rune) bool { return validExternal(previous + string(c)) })
case '-', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.':
newLine = false
fn(c, lexerList, nil)
default:
newLine = false
fn(c, lexerLiteral, nil)
}
}
if len(previous) > 0 {
lexs = append(lexs, lexer{Type: currentType, Value: previous})
}
lxs.lexers = lexs
return lxs
}
func validExternal(s string) bool {
switch s {
// start
case "![", "[":
return true
// mid
case "](":
return true
// end
case ")":
return true
default:
return false
}
}
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