126 lines
2.3 KiB
Go
126 lines
2.3 KiB
Go
package main
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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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out chan []byte
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// combining multiple input lines
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buffer []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 NewPreproc() *fsm {
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return &fsm{}
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}
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func (m *fsm) Process(in chan []byte) chan []byte {
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m.out = make(chan []byte)
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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.flush()
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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)
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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) flush() {
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if len(m.pending) > 0 {
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m.out <- append(m.pending, '\n')
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m.pending = m.pending[:0]
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}
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}
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func isBlank(data []byte) bool {
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return len(data) == 0
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}
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func isHeader(data []byte) bool {
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return len(data) > 0 && data[0] == '#'
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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 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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func normal(m *fsm, data []byte) stateFn {
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m.flush()
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// blank line
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if isBlank(data) {
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m.out <- []byte("\n")
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return normal
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}
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// header
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if isHeader(data) {
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m.out <- append(data, '\n')
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return normal
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}
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if isFence(data) {
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m.out <- 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.out <- []byte("```\n")
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m.out <- append(data[4:], '\n')
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m.pending = []byte("```")
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return toFence
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}
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if data[len(data)-1] != '.' {
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m.buffer = append(m.buffer, data...)
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m.buffer = append(m.buffer, []byte(" ")...)
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return paragraph
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}
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// TODO
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// collapse lists
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m.out <- append(data, '\n')
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return normal
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}
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func fence(m *fsm, data []byte) stateFn {
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m.out <- append(data, '\n')
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if isFence(data) {
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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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m.out <- append(data[4:], '\n')
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if needsFence(data) {
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return toFence
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}
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return normal
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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.buffer = append(m.buffer, data...)
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m.out <- append(m.buffer, '\n')
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m.buffer = m.buffer[:0]
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return normal
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}
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m.buffer = append(m.buffer, data...)
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m.buffer = append(m.buffer, []byte(" ")...)
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return paragraph
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}
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