Gemini to HTML conversion tool and daemon
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package gmitohtml
import (
"bufio"
"bytes"
"errors"
"fmt"
"html"
"net/url"
"path"
"strings"
"sync"
)
// ErrInvalidURL is the error returned when the URL is invalid.
var ErrInvalidURL = errors.New("invalid URL")
var daemonAddress string
var assetLock sync.Mutex
func rewriteURL(u string, loc *url.URL) string {
if daemonAddress != "" {
scheme := "gemini"
if strings.HasPrefix(loc.Path, "/file/") {
scheme = "file"
}
if strings.HasPrefix(u, "file://") {
if !allowFileAccess {
return "http://" + daemonAddress + "/?FileAccessNotAllowed"
}
return "http://" + daemonAddress + "/file/" + u[7:]
}
offset := 0
if strings.HasPrefix(u, "gemini://") {
offset = 9
}
firstSlash := strings.IndexRune(u[offset:], '/')
if firstSlash != -1 {
u = strings.ToLower(u[:firstSlash+offset]) + u[firstSlash+offset:]
}
if strings.HasPrefix(u, "gemini://") {
return "http://" + daemonAddress + "/gemini/" + u[9:]
} else if strings.Contains(u, "://") {
return u
} else if loc != nil && len(u) > 0 && !strings.HasPrefix(u, "//") {
if u[0] != '/' {
if loc.Path[len(loc.Path)-1] == '/' {
u = path.Join("/", loc.Path, u)
} else {
u = path.Join("/", path.Dir(loc.Path), u)
}
}
return "http://" + daemonAddress + "/" + scheme + "/" + strings.ToLower(loc.Host) + u
}
return "http://" + daemonAddress + "/" + scheme + "/" + u
}
return u
}
func newPage() []byte {
data := []byte(pageHeader)
if daemonAddress != "" {
data = append(data, navHeader...)
}
return append(data, contentHeader...)
}
// Convert converts text/gemini to text/html.
func Convert(page []byte, u string) []byte {
var result []byte
var preformatted bool
parsedURL, err := url.Parse(u)
if err != nil {
parsedURL = nil
err = nil
}
scanner := bufio.NewScanner(bytes.NewReader(page))
for scanner.Scan() {
line := scanner.Bytes()
l := len(line)
if l >= 3 && string(line[0:3]) == "```" {
preformatted = !preformatted
if preformatted {
result = append(result, []byte("<pre>\n")...)
} else {
result = append(result, []byte("</pre>\n")...)
}
continue
}
if preformatted {
result = append(result, html.EscapeString(string(line))...)
result = append(result, []byte("\n")...)
continue
}
if l >= 6 && bytes.HasPrefix(line, []byte("=>")) {
splitStart := 2
if line[splitStart] == ' ' || line[splitStart] == '\t' {
splitStart++
}
var split [][]byte
firstSpace := bytes.IndexRune(line[splitStart:], ' ')
firstTab := bytes.IndexRune(line[splitStart:], '\t')
if firstSpace != -1 && (firstTab == -1 || firstSpace < firstTab) {
split = bytes.SplitN(line[splitStart:], []byte(" "), 2)
} else if firstTab != -1 {
split = bytes.SplitN(line[splitStart:], []byte("\t"), 2)
}
var linkURL []byte
var linkLabel []byte
if len(split) == 2 {
linkURL = split[0]
linkLabel = split[1]
} else {
linkURL = line[splitStart:]
linkLabel = line[splitStart:]
}
link := append([]byte(`<a href="`), html.EscapeString(rewriteURL(string(linkURL), parsedURL))...)
link = append(link, []byte(`">`)...)
link = append(link, html.EscapeString(string(linkLabel))...)
link = append(link, []byte(`</a>`)...)
result = append(result, link...)
result = append(result, []byte("<br>")...)
continue
}
heading := 0
for i := 0; i < l; i++ {
if line[i] == '#' {
heading++
} else {
break
}
}
if heading > 0 {
result = append(result, []byte(fmt.Sprintf("<h%d>%s</h%d>", heading, html.EscapeString(string(line[heading:])), heading))...)
continue
}
result = append(result, html.EscapeString(string(line))...)
result = append(result, []byte("<br>")...)
}
if preformatted {
result = append(result, []byte("</pre>\n")...)
}
data := newPage()
data = append(data, result...)
data = append(data, []byte(pageFooter)...)
return fillTemplateVariables(data, u, false)
}