block.go
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block.go
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	//
	// Blackfriday Markdown Processor
	// Available at http://github.com/russross/blackfriday
	//
	// Copyright © 2011 Russ Ross <russ@russross.com>.
	// Distributed under the Simplified BSD License.
	// See README.md for details.
	//

	//
	// Functions to parse block-level elements.
	//

	package blackfriday

	import (
	"bytes"

	"github.com/shurcooL/sanitized_anchor_name"
	)

	// Parse block-level data.
	// Note: this function and many that it calls assume that
	// the input buffer ends with a newline.
	func (p parser) block(out bytes.Buffer, data []byte) {
	if len(data) == 0 \|\| data[len(data)-1] != '\n' {
	panic("block input is missing terminating newline")
	}

	// this is called recursively: enforce a maximum depth
	if p.nesting >= p.maxNesting {
	return
	}
	p.nesting++

	// parse out one block-level construct at a time
	for len(data) > 0 {
	// prefixed header:
	//
	// # Header 1
	// ## Header 2
	// ...
	// ###### Header 6
	if p.isPrefixHeader(data) {
	data = data[p.prefixHeader(out, data):]
	continue
	}

	// block of preformatted HTML:
	//
	// <div>
	// ...
	// </div>
	if data[0] == '<' {
	if i := p.html(out, data, true); i > 0 {
	data = data[i:]
	continue
	}
	}

	// title block
	//
	// % stuff
	// % more stuff
	// % even more stuff
	if p.flags&EXTENSION_TITLEBLOCK != 0 {
	if data[0] == '%' {
	if i := p.titleBlock(out, data, true); i > 0 {
	data = data[i:]
	continue
	}
	}
	}

	// blank lines. note: returns the # of bytes to skip
	if i := p.isEmpty(data); i > 0 {
	data = data[i:]
	continue
	}

	// fenced code block:
	//
	// ``` go
	// func fact(n int) int {
	// if n <= 1 {
	// return n
	// }
	// return n * fact(n-1)
	// }
	// ```
	if p.flags&EXTENSION_FENCED_CODE != 0 {
	if i := p.fencedCodeBlock(out, data, true); i > 0 {
	data = data[i:]
	continue
	}
	}

	// horizontal rule:
	//
	// ------
	if p.isHRule(data) {
	p.r.HRule(out)
	var i int
	for i = 0; data[i] != '\n'; i++ {
	}
	data = data[i:]
	continue
	}

	// block quote:
	//
	// > A big quote I found somewhere
	// > on the web
	if p.quotePrefix(data) > 0 {
	data = data[p.quote(out, data):]
	continue
	}

	// table:
	//
	// Name \| Age \| Phone
	// ------\|-----\|---------
	// Bob \| 31 \| 555-1234
	// Alice \| 27 \| 555-4321
	if p.flags&EXTENSION_TABLES != 0 {
	if i := p.table(out, data); i > 0 {
	data = data[i:]
	continue
	}
	}

	// an itemized/unordered list:
	//
	// * Item 1
	// * Item 2
	//
	// also works with + or -
	if p.uliPrefix(data) > 0 {
	data = data[p.list(out, data, 0):]
	continue
	}

	// a numbered/ordered list:
	//
	// 1. Item 1
	// 2. Item 2
	if p.oliPrefix(data) > 0 {
	data = data[p.list(out, data, LIST_TYPE_ORDERED):]
	continue
	}

	// definition lists:
	//
	// Term 1
	// : Definition a
	// : Definition b
	//
	// Term 2
	// : Definition c
	if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
	if p.dliPrefix(data) > 0 {
	data = data[p.list(out, data, LIST_TYPE_DEFINITION):]
	continue
	}
	}

	// anything else must look like a normal paragraph
	// note: this finds underlined headers, too
	data = data[p.paragraph(out, data):]
	}

	p.nesting--
	}

	func (p *parser) isPrefixHeader(data []byte) bool {
	if data[0] != '#' {
	return false
	}

	if p.flags&EXTENSION_SPACE_HEADERS != 0 {
	level := 0
	for level < 6 && data[level] == '#' {
	level++
	}
	if data[level] != ' ' {
	return false
	}
	}
	return true
	}

	func (p parser) prefixHeader(out bytes.Buffer, data []byte) int {
	level := 0
	for level < 6 && data[level] == '#' {
	level++
	}
	i := skipChar(data, level, ' ')
	end := skipUntilChar(data, i, '\n')
	skip := end
	id := ""
	if p.flags&EXTENSION_HEADER_IDS != 0 {
	j, k := 0, 0
	// find start/end of header id
	for j = i; j < end-1 && (data[j] != '{' \|\| data[j+1] != '#'); j++ {
	}
	for k = j + 1; k < end && data[k] != '}'; k++ {
	}
	// extract header id iff found
	if j < end && k < end {
	id = string(data[j+2 : k])
	end = j
	skip = k + 1
	for end > 0 && data[end-1] == ' ' {
	end--
	}
	}
	}
	for end > 0 && data[end-1] == '#' {
	if isBackslashEscaped(data, end-1) {
	break
	}
	end--
	}
	for end > 0 && data[end-1] == ' ' {
	end--
	}
	if end > i {
	if id == "" && p.flags&EXTENSION_AUTO_HEADER_IDS != 0 {
	id = sanitized_anchor_name.Create(string(data[i:end]))
	}
	work := func() bool {
	p.inline(out, data[i:end])
	return true
	}
	p.r.Header(out, work, level, id)
	}
	return skip
	}

	func (p *parser) isUnderlinedHeader(data []byte) int {
	// test of level 1 header
	if data[0] == '=' {
	i := skipChar(data, 1, '=')
	i = skipChar(data, i, ' ')
	if data[i] == '\n' {
	return 1
	} else {
	return 0
	}
	}

	// test of level 2 header
	if data[0] == '-' {
	i := skipChar(data, 1, '-')
	i = skipChar(data, i, ' ')
	if data[i] == '\n' {
	return 2
	} else {
	return 0
	}
	}

	return 0
	}

	func (p parser) titleBlock(out bytes.Buffer, data []byte, doRender bool) int {
	if data[0] != '%' {
	return 0
	}
	splitData := bytes.Split(data, []byte("\n"))
	var i int
	for idx, b := range splitData {
	if !bytes.HasPrefix(b, []byte("%")) {
	i = idx // - 1
	break
	}
	}

	data = bytes.Join(splitData[0:i], []byte("\n"))
	p.r.TitleBlock(out, data)

	return len(data)
	}

	func (p parser) html(out bytes.Buffer, data []byte, doRender bool) int {
	var i, j int

	// identify the opening tag
	if data[0] != '<' {
	return 0
	}
	curtag, tagfound := p.htmlFindTag(data[1:])

	// handle special cases
	if !tagfound {
	// check for an HTML comment
	if size := p.htmlComment(out, data, doRender); size > 0 {
	return size
	}

	// check for an <hr> tag
	if size := p.htmlHr(out, data, doRender); size > 0 {
	return size
	}

	// check for HTML CDATA
	if size := p.htmlCDATA(out, data, doRender); size > 0 {
	return size
	}

	// no special case recognized
	return 0
	}

	// look for an unindented matching closing tag
	// followed by a blank line
	found := false
	/*
	closetag := []byte("\n</" + curtag + ">")
	j = len(curtag) + 1
	for !found {
	// scan for a closing tag at the beginning of a line
	if skip := bytes.Index(data[j:], closetag); skip >= 0 {
	j += skip + len(closetag)
	} else {
	break
	}

	// see if it is the only thing on the line
	if skip := p.isEmpty(data[j:]); skip > 0 {
	// see if it is followed by a blank line/eof
	j += skip
	if j >= len(data) {
	found = true
	i = j
	} else {
	if skip := p.isEmpty(data[j:]); skip > 0 {
	j += skip
	found = true
	i = j
	}
	}
	}
	}
	*/

	// if not found, try a second pass looking for indented match
	// but not if tag is "ins" or "del" (following original Markdown.pl)
	if !found && curtag != "ins" && curtag != "del" {
	i = 1
	for i < len(data) {
	i++
	for i < len(data) && !(data[i-1] == '<' && data[i] == '/') {
	i++
	}

	if i+2+len(curtag) >= len(data) {
	break
	}

	j = p.htmlFindEnd(curtag, data[i-1:])

	if j > 0 {
	i += j - 1
	found = true
	break
	}
	}
	}

	if !found {
	return 0
	}

	// the end of the block has been found
	if doRender {
	// trim newlines
	end := i
	for end > 0 && data[end-1] == '\n' {
	end--
	}
	p.r.BlockHtml(out, data[:end])
	}

	return i
	}

	func (p parser) renderHTMLBlock(out bytes.Buffer, data []byte, start int, doRender bool) int {
	// html block needs to end with a blank line
	if i := p.isEmpty(data[start:]); i > 0 {
	size := start + i
	if doRender {
	// trim trailing newlines
	end := size
	for end > 0 && data[end-1] == '\n' {
	end--
	}
	p.r.BlockHtml(out, data[:end])
	}
	return size
	}
	return 0
	}

	// HTML comment, lax form
	func (p parser) htmlComment(out bytes.Buffer, data []byte, doRender bool) int {
	i := p.inlineHTMLComment(out, data)
	return p.renderHTMLBlock(out, data, i, doRender)
	}

	// HTML CDATA section
	func (p parser) htmlCDATA(out bytes.Buffer, data []byte, doRender bool) int {
	const cdataTag = "<![cdata["
	const cdataTagLen = len(cdataTag)
	if len(data) < cdataTagLen+1 {
	return 0
	}
	if !bytes.Equal(bytes.ToLower(data[:cdataTagLen]), []byte(cdataTag)) {
	return 0
	}
	i := cdataTagLen
	// scan for an end-of-comment marker, across lines if necessary
	for i < len(data) && !(data[i-2] == ']' && data[i-1] == ']' && data[i] == '>') {
	i++
	}
	i++
	// no end-of-comment marker
	if i >= len(data) {
	return 0
	}
	return p.renderHTMLBlock(out, data, i, doRender)
	}

	// HR, which is the only self-closing block tag considered
	func (p parser) htmlHr(out bytes.Buffer, data []byte, doRender bool) int {
	if data[0] != '<' \|\| (data[1] != 'h' && data[1] != 'H') \|\| (data[2] != 'r' && data[2] != 'R') {
	return 0
	}
	if data[3] != ' ' && data[3] != '/' && data[3] != '>' {
	// not an <hr> tag after all; at least not a valid one
	return 0
	}

	i := 3
	for data[i] != '>' && data[i] != '\n' {
	i++
	}

	if data[i] == '>' {
	return p.renderHTMLBlock(out, data, i+1, doRender)
	}

	return 0
	}

	func (p *parser) htmlFindTag(data []byte) (string, bool) {
	i := 0
	for isalnum(data[i]) {
	i++
	}
	key := string(data[:i])
	if _, ok := blockTags[key]; ok {
	return key, true
	}
	return "", false
	}

	func (p *parser) htmlFindEnd(tag string, data []byte) int {
	// assume data[0] == '<' && data[1] == '/' already tested

	// check if tag is a match
	closetag := []byte("</" + tag + ">")
	if !bytes.HasPrefix(data, closetag) {
	return 0
	}
	i := len(closetag)

	// check that the rest of the line is blank
	skip := 0
	if skip = p.isEmpty(data[i:]); skip == 0 {
	return 0
	}
	i += skip
	skip = 0

	if i >= len(data) {
	return i
	}

	if p.flags&EXTENSION_LAX_HTML_BLOCKS != 0 {
	return i
	}
	if skip = p.isEmpty(data[i:]); skip == 0 {
	// following line must be blank
	return 0
	}

	return i + skip
	}

	func (*parser) isEmpty(data []byte) int {
	// it is okay to call isEmpty on an empty buffer
	if len(data) == 0 {
	return 0
	}

	var i int
	for i = 0; i < len(data) && data[i] != '\n'; i++ {
	if data[i] != ' ' && data[i] != '\t' {
	return 0
	}
	}
	return i + 1
	}

	func (*parser) isHRule(data []byte) bool {
	i := 0

	// skip up to three spaces
	for i < 3 && data[i] == ' ' {
	i++
	}

	// character must be a hyphen, otherwise not HR
	if data[i] != '-' {
	return false
	}
	c := data[i]

	// the whole line must be the char or whitespace
	n := 0
	for data[i] != '\n' {
	switch {
	case data[i] == c:
	n++
	case data[i] != ' ':
	return false
	}
	i++
	}

	return n >= 3
	}

	// isFenceLine checks if there's a fence line (e.g., ``` or ``` go) at the beginning of data,
	// and returns the end index if so, or 0 otherwise. It also returns the marker found.
	// If syntax is not nil, it gets set to the syntax specified in the fence line.
	// A final newline is mandatory to recognize the fence line, unless newlineOptional is true.
	func isFenceLine(data []byte, syntax *string, oldmarker string, newlineOptional bool) (end int, marker string) {
	i, size := 0, 0

	// skip up to three spaces
	for i < len(data) && i < 3 && data[i] == ' ' {
	i++
	}

	// check for the marker characters: ~ or `
	if i >= len(data) {
	return 0, ""
	}
	if data[i] != '~' && data[i] != '`' {
	return 0, ""
	}

	c := data[i]

	// the whole line must be the same char or whitespace
	for i < len(data) && data[i] == c {
	size++
	i++
	}

	// the marker char must occur at least 3 times
	if size < 3 {
	return 0, ""
	}
	marker = string(data[i-size : i])

	// if this is the end marker, it must match the beginning marker
	if oldmarker != "" && marker != oldmarker {
	return 0, ""
	}

	// TODO(shurcooL): It's probably a good idea to simplify the 2 code paths here
	// into one, always get the syntax, and discard it if the caller doesn't care.
	if syntax != nil {
	syn := 0
	i = skipChar(data, i, ' ')

	if i >= len(data) {
	if newlineOptional && i == len(data) {
	return i, marker
	}
	return 0, ""
	}

	syntaxStart := i

	if data[i] == '{' {
	i++
	syntaxStart++

	for i < len(data) && data[i] != '}' && data[i] != '\n' {
	syn++
	i++
	}

	if i >= len(data) \|\| data[i] != '}' {
	return 0, ""
	}

	// strip all whitespace at the beginning and the end
	// of the {} block
	for syn > 0 && isspace(data[syntaxStart]) {
	syntaxStart++
	syn--
	}

	for syn > 0 && isspace(data[syntaxStart+syn-1]) {
	syn--
	}

	i++
	} else {
	for i < len(data) && !isspace(data[i]) {
	syn++
	i++
	}
	}

	*syntax = string(data[syntaxStart : syntaxStart+syn])
	}

	i = skipChar(data, i, ' ')
	if i >= len(data) \|\| data[i] != '\n' {
	if newlineOptional && i == len(data) {
	return i, marker
	}
	return 0, ""
	}

	return i + 1, marker // Take newline into account.
	}

	// fencedCodeBlock returns the end index if data contains a fenced code block at the beginning,
	// or 0 otherwise. It writes to out if doRender is true, otherwise it has no side effects.
	// If doRender is true, a final newline is mandatory to recognize the fenced code block.
	func (p parser) fencedCodeBlock(out bytes.Buffer, data []byte, doRender bool) int {
	var syntax string
	beg, marker := isFenceLine(data, &syntax, "", false)
	if beg == 0 \|\| beg >= len(data) {
	return 0
	}

	var work bytes.Buffer

	for {
	// safe to assume beg < len(data)

	// check for the end of the code block
	newlineOptional := !doRender
	fenceEnd, _ := isFenceLine(data[beg:], nil, marker, newlineOptional)
	if fenceEnd != 0 {
	beg += fenceEnd
	break
	}

	// copy the current line
	end := skipUntilChar(data, beg, '\n') + 1

	// did we reach the end of the buffer without a closing marker?
	if end >= len(data) {
	return 0
	}

	// verbatim copy to the working buffer
	if doRender {
	work.Write(data[beg:end])
	}
	beg = end
	}

	if doRender {
	p.r.BlockCode(out, work.Bytes(), syntax)
	}

	return beg
	}

	func (p parser) table(out bytes.Buffer, data []byte) int {
	var header bytes.Buffer
	i, columns := p.tableHeader(&header, data)
	if i == 0 {
	return 0
	}

	var body bytes.Buffer

	for i < len(data) {
	pipes, rowStart := 0, i
	for ; data[i] != '\n'; i++ {
	if data[i] == '\|' {
	pipes++
	}
	}

	if pipes == 0 {
	i = rowStart
	break
	}

	// include the newline in data sent to tableRow
	i++
	p.tableRow(&body, data[rowStart:i], columns, false)
	}

	p.r.Table(out, header.Bytes(), body.Bytes(), columns)

	return i
	}

	// check if the specified position is preceded by an odd number of backslashes
	func isBackslashEscaped(data []byte, i int) bool {
	backslashes := 0
	for i-backslashes-1 >= 0 && data[i-backslashes-1] == '\\' {
	backslashes++
	}
	return backslashes&1 == 1
	}

	func (p parser) tableHeader(out bytes.Buffer, data []byte) (size int, columns []int) {
	i := 0
	colCount := 1
	for i = 0; data[i] != '\n'; i++ {
	if data[i] == '\|' && !isBackslashEscaped(data, i) {
	colCount++
	}
	}

	// doesn't look like a table header
	if colCount == 1 {
	return
	}

	// include the newline in the data sent to tableRow
	header := data[:i+1]

	// column count ignores pipes at beginning or end of line
	if data[0] == '\|' {
	colCount--
	}
	if i > 2 && data[i-1] == '\|' && !isBackslashEscaped(data, i-1) {
	colCount--
	}

	columns = make([]int, colCount)

	// move on to the header underline
	i++
	if i >= len(data) {
	return
	}

	if data[i] == '\|' && !isBackslashEscaped(data, i) {
	i++
	}
	i = skipChar(data, i, ' ')

	// each column header is of form: / :?-+:? \|/ with # dashes + # colons >= 3
	// and trailing \| optional on last column
	col := 0
	for data[i] != '\n' {
	dashes := 0

	if data[i] == ':' {
	i++
	columns[col] \|= TABLE_ALIGNMENT_LEFT
	dashes++
	}
	for data[i] == '-' {
	i++
	dashes++
	}
	if data[i] == ':' {
	i++
	columns[col] \|= TABLE_ALIGNMENT_RIGHT
	dashes++
	}
	for data[i] == ' ' {
	i++
	}

	// end of column test is messy
	switch {
	case dashes < 3:
	// not a valid column
	return

	case data[i] == '\|' && !isBackslashEscaped(data, i):
	// marker found, now skip past trailing whitespace
	col++
	i++
	for data[i] == ' ' {
	i++
	}

	// trailing junk found after last column
	if col >= colCount && data[i] != '\n' {
	return
	}

	case (data[i] != '\|' \|\| isBackslashEscaped(data, i)) && col+1 < colCount:
	// something else found where marker was required
	return

	case data[i] == '\n':
	// marker is optional for the last column
	col++

	default:
	// trailing junk found after last column
	return
	}
	}
	if col != colCount {
	return
	}

	p.tableRow(out, header, columns, true)
	size = i + 1
	return
	}

	func (p parser) tableRow(out bytes.Buffer, data []byte, columns []int, header bool) {
	i, col := 0, 0
	var rowWork bytes.Buffer

	if data[i] == '\|' && !isBackslashEscaped(data, i) {
	i++
	}

	for col = 0; col < len(columns) && i < len(data); col++ {
	for data[i] == ' ' {
	i++
	}

	cellStart := i

	for (data[i] != '\|' \|\| isBackslashEscaped(data, i)) && data[i] != '\n' {
	i++
	}

	cellEnd := i

	// skip the end-of-cell marker, possibly taking us past end of buffer
	i++

	for cellEnd > cellStart && data[cellEnd-1] == ' ' {
	cellEnd--
	}

	var cellWork bytes.Buffer
	p.inline(&cellWork, data[cellStart:cellEnd])

	if header {
	p.r.TableHeaderCell(&rowWork, cellWork.Bytes(), columns[col])
	} else {
	p.r.TableCell(&rowWork, cellWork.Bytes(), columns[col])
	}
	}

	// pad it out with empty columns to get the right number
	for ; col < len(columns); col++ {
	if header {
	p.r.TableHeaderCell(&rowWork, nil, columns[col])
	} else {
	p.r.TableCell(&rowWork, nil, columns[col])
	}
	}

	// silently ignore rows with too many cells

	p.r.TableRow(out, rowWork.Bytes())
	}

	// returns blockquote prefix length
	func (p *parser) quotePrefix(data []byte) int {
	i := 0
	for i < 3 && data[i] == ' ' {
	i++
	}
	if data[i] == '>' {
	if data[i+1] == ' ' {
	return i + 2
	}
	return i + 1
	}
	return 0
	}

	// blockquote ends with at least one blank line
	// followed by something without a blockquote prefix
	func (p *parser) terminateBlockquote(data []byte, beg, end int) bool {
	if p.isEmpty(data[beg:]) <= 0 {
	return false
	}
	if end >= len(data) {
	return true
	}
	return p.quotePrefix(data[end:]) == 0 && p.isEmpty(data[end:]) == 0
	}

	// parse a blockquote fragment
	func (p parser) quote(out bytes.Buffer, data []byte) int {
	var raw bytes.Buffer
	beg, end := 0, 0
	for beg < len(data) {
	end = beg
	// Step over whole lines, collecting them. While doing that, check for
	// fenced code and if one's found, incorporate it altogether,
	// irregardless of any contents inside it
	for data[end] != '\n' {
	if p.flags&EXTENSION_FENCED_CODE != 0 {
	if i := p.fencedCodeBlock(out, data[end:], false); i > 0 {
	// -1 to compensate for the extra end++ after the loop:
	end += i - 1
	break
	}
	}
	end++
	}
	end++

	if pre := p.quotePrefix(data[beg:]); pre > 0 {
	// skip the prefix
	beg += pre
	} else if p.terminateBlockquote(data, beg, end) {
	break
	}

	// this line is part of the blockquote
	raw.Write(data[beg:end])
	beg = end
	}

	var cooked bytes.Buffer
	p.block(&cooked, raw.Bytes())
	p.r.BlockQuote(out, cooked.Bytes())
	return end
	}

	// returns prefix length for block code
	func (p *parser) codePrefix(data []byte) int {
	if data[0] == ' ' && data[1] == ' ' && data[2] == ' ' && data[3] == ' ' {
	return 4
	}
	return 0
	}

	func (p parser) code(out bytes.Buffer, data []byte) int {
	var work bytes.Buffer

	i := 0
	for i < len(data) {
	beg := i
	for data[i] != '\n' {
	i++
	}
	i++

	blankline := p.isEmpty(data[beg:i]) > 0
	if pre := p.codePrefix(data[beg:i]); pre > 0 {
	beg += pre
	} else if !blankline {
	// non-empty, non-prefixed line breaks the pre
	i = beg
	break
	}

	// verbatim copy to the working buffeu
	if blankline {
	work.WriteByte('\n')
	} else {
	work.Write(data[beg:i])
	}
	}

	// trim all the \n off the end of work
	workbytes := work.Bytes()
	eol := len(workbytes)
	for eol > 0 && workbytes[eol-1] == '\n' {
	eol--
	}
	if eol != len(workbytes) {
	work.Truncate(eol)
	}

	work.WriteByte('\n')

	p.r.BlockCode(out, work.Bytes(), "")

	return i
	}

	// returns unordered list item prefix
	func (p *parser) uliPrefix(data []byte) int {
	i := 0

	// start with up to 3 spaces
	for i < 3 && data[i] == ' ' {
	i++
	}

	// need a *, +, or - followed by a space
	if (data[i] != '*' && data[i] != '+' && data[i] != '-') \|\|
	data[i+1] != ' ' {
	return 0
	}
	return i + 2
	}

	// returns ordered list item prefix
	func (p *parser) oliPrefix(data []byte) int {
	i := 0

	// start with up to 3 spaces
	for i < 3 && data[i] == ' ' {
	i++
	}

	// count the digits
	start := i
	for data[i] >= '0' && data[i] <= '9' {
	i++
	}

	// we need >= 1 digits followed by a dot and a space
	if start == i \|\| data[i] != '.' \|\| data[i+1] != ' ' {
	return 0
	}
	return i + 2
	}

	// returns definition list item prefix
	func (p *parser) dliPrefix(data []byte) int {
	i := 0

	// need a : followed by a spaces
	if data[i] != ':' \|\| data[i+1] != ' ' {
	return 0
	}
	for data[i] == ' ' {
	i++
	}
	return i + 2
	}

	// parse ordered or unordered list block
	func (p parser) list(out bytes.Buffer, data []byte, flags int) int {
	i := 0
	flags \|= LIST_ITEM_BEGINNING_OF_LIST
	work := func() bool {
	for i < len(data) {
	skip := p.listItem(out, data[i:], &flags)
	i += skip

	if skip == 0 \|\| flags&LIST_ITEM_END_OF_LIST != 0 {
	break
	}
	flags &= ^LIST_ITEM_BEGINNING_OF_LIST
	}
	return true
	}

	p.r.List(out, work, flags)
	return i
	}

	// Parse a single list item.
	// Assumes initial prefix is already removed if this is a sublist.
	func (p parser) listItem(out bytes.Buffer, data []byte, flags *int) int {
	// keep track of the indentation of the first line
	itemIndent := 0
	for itemIndent < 3 && data[itemIndent] == ' ' {
	itemIndent++
	}

	i := p.uliPrefix(data)
	if i == 0 {
	i = p.oliPrefix(data)
	}
	if i == 0 {
	i = p.dliPrefix(data)
	// reset definition term flag
	if i > 0 {
	*flags &= ^LIST_TYPE_TERM
	}
	}
	if i == 0 {
	// if in defnition list, set term flag and continue
	if *flags&LIST_TYPE_DEFINITION != 0 {
	*flags \|= LIST_TYPE_TERM
	} else {
	return 0
	}
	}

	// skip leading whitespace on first line
	for data[i] == ' ' {
	i++
	}

	// find the end of the line
	line := i
	for i > 0 && data[i-1] != '\n' {
	i++
	}

	// get working buffer
	var raw bytes.Buffer

	// put the first line into the working buffer
	raw.Write(data[line:i])
	line = i

	// process the following lines
	containsBlankLine := false
	sublist := 0

	gatherlines:
	for line < len(data) {
	i++

	// find the end of this line
	for data[i-1] != '\n' {
	i++
	}

	// if it is an empty line, guess that it is part of this item
	// and move on to the next line
	if p.isEmpty(data[line:i]) > 0 {
	containsBlankLine = true
	raw.Write(data[line:i])
	line = i
	continue
	}

	// calculate the indentation
	indent := 0
	for indent < 4 && line+indent < i && data[line+indent] == ' ' {
	indent++
	}

	chunk := data[line+indent : i]

	// evaluate how this line fits in
	switch {
	// is this a nested list item?
	case (p.uliPrefix(chunk) > 0 && !p.isHRule(chunk)) \|\|
	p.oliPrefix(chunk) > 0 \|\|
	p.dliPrefix(chunk) > 0:

	if containsBlankLine {
	// end the list if the type changed after a blank line
	if indent <= itemIndent &&
	((*flags&LIST_TYPE_ORDERED != 0 && p.uliPrefix(chunk) > 0) \|\|
	(*flags&LIST_TYPE_ORDERED == 0 && p.oliPrefix(chunk) > 0)) {

	*flags \|= LIST_ITEM_END_OF_LIST
	break gatherlines
	}
	*flags \|= LIST_ITEM_CONTAINS_BLOCK
	}

	// to be a nested list, it must be indented more
	// if not, it is the next item in the same list
	if indent <= itemIndent {
	break gatherlines
	}

	// is this the first item in the nested list?
	if sublist == 0 {
	sublist = raw.Len()
	}

	// is this a nested prefix header?
	case p.isPrefixHeader(chunk):
	// if the header is not indented, it is not nested in the list
	// and thus ends the list
	if containsBlankLine && indent < 4 {
	*flags \|= LIST_ITEM_END_OF_LIST
	break gatherlines
	}
	*flags \|= LIST_ITEM_CONTAINS_BLOCK

	// anything following an empty line is only part
	// of this item if it is indented 4 spaces
	// (regardless of the indentation of the beginning of the item)
	case containsBlankLine && indent < 4:
	if *flags&LIST_TYPE_DEFINITION != 0 && i < len(data)-1 {
	// is the next item still a part of this list?
	next := i
	for data[next] != '\n' {
	next++
	}
	for next < len(data)-1 && data[next] == '\n' {
	next++
	}
	if i < len(data)-1 && data[i] != ':' && data[next] != ':' {
	*flags \|= LIST_ITEM_END_OF_LIST
	}
	} else {
	*flags \|= LIST_ITEM_END_OF_LIST
	}
	break gatherlines

	// a blank line means this should be parsed as a block
	case containsBlankLine:
	*flags \|= LIST_ITEM_CONTAINS_BLOCK
	}

	containsBlankLine = false

	// add the line into the working buffer without prefix
	raw.Write(data[line+indent : i])

	line = i
	}

	// If reached end of data, the Renderer.ListItem call we're going to make below
	// is definitely the last in the list.
	if line >= len(data) {
	*flags \|= LIST_ITEM_END_OF_LIST
	}

	rawBytes := raw.Bytes()

	// render the contents of the list item
	var cooked bytes.Buffer
	if flags&LIST_ITEM_CONTAINS_BLOCK != 0 && flags&LIST_TYPE_TERM == 0 {
	// intermediate render of block item, except for definition term
	if sublist > 0 {
	p.block(&cooked, rawBytes[:sublist])
	p.block(&cooked, rawBytes[sublist:])
	} else {
	p.block(&cooked, rawBytes)
	}
	} else {
	// intermediate render of inline item
	if sublist > 0 {
	p.inline(&cooked, rawBytes[:sublist])
	p.block(&cooked, rawBytes[sublist:])
	} else {
	p.inline(&cooked, rawBytes)
	}
	}

	// render the actual list item
	cookedBytes := cooked.Bytes()
	parsedEnd := len(cookedBytes)

	// strip trailing newlines
	for parsedEnd > 0 && cookedBytes[parsedEnd-1] == '\n' {
	parsedEnd--
	}
	p.r.ListItem(out, cookedBytes[:parsedEnd], *flags)

	return line
	}

	// render a single paragraph that has already been parsed out
	func (p parser) renderParagraph(out bytes.Buffer, data []byte) {
	if len(data) == 0 {
	return
	}

	beg := 0

	// trim trailing newline
	end := len(data) - 1

	// trim trailing spaces
	for end > beg && data[end-1] == ' ' {
	end--
	}

	work := func() bool {
	p.inline(out, data[beg:end])
	return true
	}
	p.r.Paragraph(out, work)
	}

	func (p parser) paragraph(out bytes.Buffer, data []byte) int {
	// prev: index of 1st char of previous line
	// line: index of 1st char of current line
	// i: index of cursor/end of current line
	var prev, line, i int

	// keep going until we find something to mark the end of the paragraph
	for i < len(data) {
	// mark the beginning of the current line
	prev = line
	current := data[i:]
	line = i

	// did we find a blank line marking the end of the paragraph?
	if n := p.isEmpty(current); n > 0 {
	// did this blank line followed by a definition list item?
	if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
	if i < len(data)-1 && data[i+1] == ':' {
	return p.list(out, data[prev:], LIST_TYPE_DEFINITION)
	}
	}

	p.renderParagraph(out, data[:i])
	return i + n
	}

	// an underline under some text marks a header, so our paragraph ended on prev line
	// -- But we don't want Setext-style headers on Write.as. atx is great.
	/*
	if i > 0 {
	if level := p.isUnderlinedHeader(current); level > 0 {
	// render the paragraph
	p.renderParagraph(out, data[:prev])

	// ignore leading and trailing whitespace
	eol := i - 1
	for prev < eol && data[prev] == ' ' {
	prev++
	}
	for eol > prev && data[eol-1] == ' ' {
	eol--
	}

	// render the header
	// this ugly double closure avoids forcing variables onto the heap
	work := func(o bytes.Buffer, pp parser, d []byte) func() bool {
	return func() bool {
	pp.inline(o, d)
	return true
	}
	}(out, p, data[prev:eol])

	id := ""
	if p.flags&EXTENSION_AUTO_HEADER_IDS != 0 {
	id = sanitized_anchor_name.Create(string(data[prev:eol]))
	}

	p.r.Header(out, work, level, id)

	// find the end of the underline
	for data[i] != '\n' {
	i++
	}
	return i
	}
	}
	*/

	// if the next line starts a block of HTML, then the paragraph ends here
	if p.flags&EXTENSION_LAX_HTML_BLOCKS != 0 {
	if data[i] == '<' && p.html(out, current, false) > 0 {
	// rewind to before the HTML block
	p.renderParagraph(out, data[:i])
	return i
	}
	}

	// if there's a prefixed header or a horizontal rule after this, paragraph is over
	if p.isPrefixHeader(current) \|\| p.isHRule(current) {
	p.renderParagraph(out, data[:i])
	return i
	}

	// if there's a fenced code block, paragraph is over
	if p.flags&EXTENSION_FENCED_CODE != 0 {
	if p.fencedCodeBlock(out, current, false) > 0 {
	p.renderParagraph(out, data[:i])
	return i
	}
	}

	// if there's a definition list item, prev line is a definition term
	if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
	if p.dliPrefix(current) != 0 {
	return p.list(out, data[prev:], LIST_TYPE_DEFINITION)
	}
	}

	// if there's a list after this, paragraph is over
	if p.flags&EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK != 0 {
	if p.uliPrefix(current) != 0 \|\|
	p.oliPrefix(current) != 0 \|\|
	p.quotePrefix(current) != 0 \|\|
	p.codePrefix(current) != 0 {
	p.renderParagraph(out, data[:i])
	return i
	}
	}

	// otherwise, scan to the beginning of the next line
	for data[i] != '\n' {
	i++
	}
	i++
	}

	p.renderParagraph(out, data[:i])
	return i
	}

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