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|
package parser
import (
"bufio"
"bytes"
"fmt"
"io"
"unicode"
)
const (
HTML_LEAD = "<"
YAML_LEAD = "-"
YAML_DELIM_UNIX = "---\n"
YAML_DELIM_DOS = "---\r\n"
TOML_LEAD = "+"
TOML_DELIM_UNIX = "+++\n"
TOML_DELIM_DOS = "+++\r\n"
JSON_LEAD = "{"
)
var (
delims = [][]byte{
[]byte(YAML_DELIM_UNIX),
[]byte(YAML_DELIM_DOS),
[]byte(TOML_DELIM_UNIX),
[]byte(TOML_DELIM_DOS),
[]byte(JSON_LEAD),
}
unixEnding = []byte("\n")
dosEnding = []byte("\r\n")
)
type FrontMatter []byte
type Content []byte
type Page interface {
FrontMatter() FrontMatter
Content() Content
IsRenderable() bool
}
type page struct {
render bool
frontmatter FrontMatter
content Content
}
func (p *page) Content() Content {
return p.content
}
func (p *page) FrontMatter() FrontMatter {
return p.frontmatter
}
func (p *page) IsRenderable() bool {
return p.render
}
// ReadFrom reads the content from an io.Reader and constructs a page.
func ReadFrom(r io.Reader) (p Page, err error) {
reader := bufio.NewReader(r)
if err = chompWhitespace(reader); err != nil && err != io.EOF {
return
}
firstLine, err := peekLine(reader)
if err != nil && err != io.EOF {
return
}
newp := new(page)
newp.render = shouldRender(firstLine)
if newp.render && isFrontMatterDelim(firstLine) {
left, right := determineDelims(firstLine)
fm, err := extractFrontMatterDelims(reader, left, right)
if err != nil {
return nil, err
}
newp.frontmatter = fm
}
content, err := extractContent(reader)
if err != nil {
return nil, err
}
newp.content = content
return newp, nil
}
func chompWhitespace(r io.RuneScanner) (err error) {
for {
c, _, err := r.ReadRune()
if err != nil {
return err
}
if !unicode.IsSpace(c) {
r.UnreadRune()
return nil
}
}
}
func peekLine(r *bufio.Reader) (line []byte, err error) {
firstFive, err := r.Peek(5)
if err != nil {
return
}
idx := bytes.IndexByte(firstFive, '\n')
if idx == -1 {
return firstFive, nil
}
idx += 1 // include newline.
return firstFive[:idx], nil
}
func shouldRender(lead []byte) (frontmatter bool) {
if len(lead) <= 0 {
return
}
if bytes.Equal(lead[:1], []byte(HTML_LEAD)) {
return
}
return true
}
func isFrontMatterDelim(data []byte) bool {
for _, d := range delims {
if bytes.HasPrefix(data, d) {
return true
}
}
return false
}
func determineDelims(firstLine []byte) (left, right []byte) {
switch len(firstLine) {
case 4:
if firstLine[0] == YAML_LEAD[0] {
return []byte(YAML_DELIM_UNIX), []byte(YAML_DELIM_UNIX)
}
return []byte(TOML_DELIM_UNIX), []byte(TOML_DELIM_UNIX)
case 5:
if firstLine[0] == YAML_LEAD[0] {
return []byte(YAML_DELIM_DOS), []byte(YAML_DELIM_DOS)
}
return []byte(TOML_DELIM_DOS), []byte(TOML_DELIM_DOS)
case 3:
fallthrough
case 2:
fallthrough
case 1:
return []byte(JSON_LEAD), []byte("}")
default:
panic(fmt.Sprintf("Unable to determine delims from %q", firstLine))
}
}
func extractFrontMatterDelims(r *bufio.Reader, left, right []byte) (fm FrontMatter, err error) {
var (
c byte
level int = 0
bytesRead int = 0
sameDelim = bytes.Equal(left, right)
)
wr := new(bytes.Buffer)
for {
if c, err = r.ReadByte(); err != nil {
return nil, fmt.Errorf("Unable to read frontmatter at filepos %d: %s", bytesRead, err)
}
bytesRead += 1
switch c {
case left[0]:
var (
buf []byte = []byte{c}
remaining []byte
)
if remaining, err = r.Peek(len(left) - 1); err != nil {
return nil, err
}
buf = append(buf, remaining...)
if bytes.Equal(buf, left) {
if sameDelim {
if level == 0 {
level = 1
} else {
level = 0
}
} else {
level += 1
}
}
if _, err = wr.Write([]byte{c}); err != nil {
return nil, err
}
if level == 0 {
if _, err = r.Read(remaining); err != nil {
return nil, err
}
if _, err = wr.Write(remaining); err != nil {
return nil, err
}
}
case right[0]:
match, err := matches(r, wr, []byte{c}, right)
if err != nil {
return nil, err
}
if match {
level -= 1
}
default:
if err = wr.WriteByte(c); err != nil {
return nil, err
}
}
if level == 0 && !unicode.IsSpace(rune(c)) {
if err = chompWhitespace(r); err != nil {
if err != io.EOF {
return nil, err
}
}
return wr.Bytes(), nil
}
}
}
func matches_quick(buf, expected []byte) (ok bool, err error) {
return bytes.Equal(expected, buf), nil
}
func matches(r *bufio.Reader, wr io.Writer, c, expected []byte) (ok bool, err error) {
if len(expected) == 1 {
if _, err = wr.Write(c); err != nil {
return
}
return bytes.Equal(c, expected), nil
}
buf := make([]byte, len(expected)-1)
if buf, err = r.Peek(len(expected) - 1); err != nil {
return
}
buf = append(c, buf...)
return bytes.Equal(expected, buf), nil
}
func extractContent(r io.Reader) (content Content, err error) {
wr := new(bytes.Buffer)
if _, err = wr.ReadFrom(r); err != nil {
return
}
return wr.Bytes(), nil
}
|
