2021-07-05 08:36:20 +03:00
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package mdproc
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import (
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"bytes"
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"regexp"
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"github.com/n0x1m/md2gmi/pipe"
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)
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// state function.
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type stateFn func(*fsm, []byte) stateFn
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// state machine.
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type fsm struct {
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state stateFn
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i int
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out chan pipe.StreamItem
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// combining multiple input lines
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blockBuffer []byte
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sendBuffer []byte
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// if we have a termination rule to abide, e.g. implied code fences
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pending []byte
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}
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func Preproc() pipe.Pipeline {
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return (&fsm{}).pipeline
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}
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func (m *fsm) pipeline(in chan pipe.StreamItem) chan pipe.StreamItem {
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m.out = make(chan pipe.StreamItem)
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go func() {
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for m.state = normal; m.state != nil; {
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b, ok := <-in
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if !ok {
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m.blockFlush()
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m.sync()
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close(m.out)
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m.state = nil
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continue
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}
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m.state = m.state(m, b.Payload())
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m.sync()
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}
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}()
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return m.out
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}
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func (m *fsm) sync() {
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if len(m.sendBuffer) > 0 {
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m.sendBuffer = append(m.sendBuffer, '\n')
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m.out <- pipe.NewItem(m.i, m.sendBuffer)
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m.sendBuffer = m.sendBuffer[:0]
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m.i++
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}
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}
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func (m *fsm) blockFlush() {
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// blockBuffer to sendbuffer
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m.sendBuffer = append(m.sendBuffer, m.blockBuffer...)
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m.blockBuffer = m.blockBuffer[:0]
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2021-07-05 19:42:21 +03:00
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// pending to sendbuffer too
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2021-07-05 08:36:20 +03:00
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if len(m.pending) > 0 {
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m.sendBuffer = append(m.sendBuffer, m.pending...)
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m.pending = m.pending[:0]
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}
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}
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func triggerBreak(data []byte) bool {
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return len(data) == 0 || data[len(data)-1] == '.'
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}
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func isTerminated(data []byte) bool {
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return len(data) > 0 && data[len(data)-1] != '.'
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}
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func handleList(data []byte) ([]byte, bool) {
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2021-07-05 20:01:29 +03:00
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re := regexp.MustCompile(`^([ \t]*[-*^]{1,1})[^*-]`)
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2021-07-05 08:36:20 +03:00
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sub := re.FindSubmatch(data)
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// if lists, collapse to single level
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if len(sub) > 1 {
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return bytes.Replace(data, sub[1], []byte("-"), 1), true
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}
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return data, false
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}
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func isFence(data []byte) bool {
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return len(data) >= 3 && string(data[0:3]) == "```"
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}
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func needsFence(data []byte) bool {
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return len(data) >= 4 && string(data[0:4]) == " "
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}
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2021-07-06 13:39:27 +03:00
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func normalText(m *fsm, data []byte) stateFn {
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2021-07-05 20:01:29 +03:00
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if len(bytes.TrimSpace(data)) == 0 {
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2021-07-05 17:43:46 +03:00
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return normal
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}
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2021-07-05 20:06:41 +03:00
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2021-07-05 08:36:20 +03:00
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if data, isList := handleList(data); isList {
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2021-07-05 20:01:29 +03:00
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m.blockBuffer = append(m.blockBuffer, data...)
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2021-07-05 08:36:20 +03:00
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m.blockFlush()
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2021-07-05 20:01:29 +03:00
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return list
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2021-07-05 08:36:20 +03:00
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}
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if isFence(data) {
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m.blockBuffer = append(data, '\n')
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return fence
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}
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if needsFence(data) {
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m.blockBuffer = append(m.blockBuffer, []byte("```\n")...)
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m.blockBuffer = append(m.blockBuffer, append(data[4:], '\n')...)
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m.pending = []byte("```\n")
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return toFence
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}
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if isTerminated(data) {
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m.blockBuffer = append(m.blockBuffer, data...)
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m.blockBuffer = append(m.blockBuffer, ' ')
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return paragraph
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}
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m.blockBuffer = append(m.blockBuffer, append(data, '\n')...)
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m.blockFlush()
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return normal
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}
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2021-07-06 13:39:27 +03:00
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func normal(m *fsm, data []byte) stateFn {
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return normalText(m, data)
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}
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2021-07-05 20:01:29 +03:00
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func list(m *fsm, data []byte) stateFn {
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if data, isList := handleList(data); isList {
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2021-07-06 13:39:27 +03:00
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data = append(data, '\n')
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2021-07-05 20:01:29 +03:00
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m.blockBuffer = append(m.blockBuffer, data...)
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return list
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}
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m.blockFlush()
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2021-07-06 13:39:27 +03:00
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return normalText(m, data)
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2021-07-05 20:01:29 +03:00
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}
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2021-07-05 08:36:20 +03:00
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func fence(m *fsm, data []byte) stateFn {
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m.blockBuffer = append(m.blockBuffer, append(data, '\n')...)
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// second fence returns to normal
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if isFence(data) {
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m.blockFlush()
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return normal
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}
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return fence
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}
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func toFence(m *fsm, data []byte) stateFn {
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if needsFence(data) {
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m.blockBuffer = append(m.blockBuffer, append(data[4:], '\n')...)
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return toFence
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}
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m.blockFlush()
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2021-07-06 13:39:27 +03:00
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return normalText(m, data)
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2021-07-05 08:36:20 +03:00
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}
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func paragraph(m *fsm, data []byte) stateFn {
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if triggerBreak(data) {
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m.blockBuffer = append(m.blockBuffer, data...)
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m.blockBuffer = bytes.TrimSpace(m.blockBuffer)
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2021-07-05 19:42:21 +03:00
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// TODO, remove double spaces inside paragraphs
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2021-07-05 08:36:20 +03:00
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m.blockBuffer = append(m.blockBuffer, '\n')
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m.blockFlush()
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return normal
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}
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m.blockBuffer = append(m.blockBuffer, data...)
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m.blockBuffer = append(m.blockBuffer, []byte(" ")...)
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return paragraph
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}
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