Gemini to HTML conversion tool and daemon
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package gmitohtml
import (
"bytes"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"html"
"io/ioutil"
"log"
"net/http"
"net/url"
"path"
"sort"
"strings"
"time"
)
var lastRequestTime = time.Now().Unix()
var (
clientCerts = make(map[string]tls.Certificate)
bookmarks = make(map[string]string)
bookmarksSorted []string
allowFileAccess bool
onBookmarksChanged func()
)
var defaultBookmarks = map[string]string{
"gemini://gemini.circumlunar.space/": "Project Gemini",
"gemini://gus.guru/": "GUS - Gemini Universal Search",
}
// ErrInvalidCertificate is the error returned when an invalid certificate is provided.
var ErrInvalidCertificate = errors.New("invalid certificate")
func bookmarksList() []byte {
fakeURL, _ := url.Parse("/") // Always succeeds
var b bytes.Buffer
b.Write([]byte(`<ul>`))
for _, u := range bookmarksSorted {
b.Write([]byte(fmt.Sprintf(`<li><a href="%s">%s</a></li>`, rewriteURL(u, fakeURL), bookmarks[u])))
}
b.Write([]byte("</ul>"))
return b.Bytes()
}
// fetch downloads and converts a Gemini page.
func fetch(u string) ([]byte, []byte, error) {
if u == "" {
return nil, nil, ErrInvalidURL
}
requestURL, err := url.ParseRequestURI(u)
if err != nil {
return nil, nil, err
}
if requestURL.Scheme == "" {
requestURL.Scheme = "gemini"
}
host := requestURL.Host
if strings.IndexRune(host, ':') == -1 {
host += ":1965"
}
tlsConfig := &tls.Config{
// This must be enabled until most sites have transitioned away from
// using self-signed certificates.
InsecureSkipVerify: true,
}
certHost := requestURL.Hostname()
if strings.HasPrefix(certHost, "www.") {
certHost = certHost[4:]
}
clientCert, certAvailable := clientCerts[certHost]
if certAvailable {
tlsConfig.Certificates = []tls.Certificate{clientCert}
}
conn, err := tls.Dial("tcp", host, tlsConfig)
if err != nil {
return nil, nil, err
}
// Send request header
conn.Write([]byte(requestURL.String() + "\r\n"))
data, err := ioutil.ReadAll(conn)
if err != nil {
return nil, nil, err
}
firstNewLine := -1
l := len(data)
if l > 2 {
for i := 1; i < l; i++ {
if data[i] == '\n' && data[i-1] == '\r' {
firstNewLine = i
break
}
}
}
var header []byte
if firstNewLine > -1 {
header = data[:firstNewLine]
data = data[firstNewLine+1:]
}
requestInput := bytes.HasPrefix(header, []byte("1"))
if requestInput {
requestSensitiveInput := bytes.HasPrefix(header, []byte("11"))
data = newPage()
data = append(data, []byte(inputPrompt)...)
data = bytes.Replace(data, []byte("~GEMINIINPUTFORM~"), []byte(html.EscapeString(rewriteURL(u, requestURL))), 1)
prompt := "(No input prompt)"
if len(header) > 3 {
prompt = string(header[3:])
}
data = bytes.Replace(data, []byte("~GEMINIINPUTPROMPT~"), []byte(prompt), 1)
inputType := "text"
if requestSensitiveInput {
inputType = "password"
}
data = bytes.Replace(data, []byte("~GEMINIINPUTTYPE~"), []byte(inputType), 1)
return header, fillTemplateVariables(data, u, false), nil
}
if !bytes.HasPrefix(header, []byte("2")) {
errorPage := newPage()
errorPage = append(errorPage, []byte(fmt.Sprintf("Server sent unexpected header:<br><br><b>%s</b>", header))...)
errorPage = append(errorPage, []byte(pageFooter)...)
return header, fillTemplateVariables(errorPage, u, false), nil
}
if bytes.HasPrefix(header, []byte("20 text/html")) {
return header, data, nil
}
return header, Convert(data, requestURL.String()), nil
}
func handleIndex(writer http.ResponseWriter, request *http.Request) {
address := request.FormValue("address")
if address != "" {
http.Redirect(writer, request, rewriteURL(address, request.URL), http.StatusSeeOther)
return
}
page := newPage()
page = append(page, bookmarksList()...)
page = append(page, pageFooter...)
writer.Write(fillTemplateVariables(page, request.URL.String(), true))
}
func fillTemplateVariables(data []byte, currentURL string, autofocus bool) []byte {
if strings.HasPrefix(currentURL, "gemini://") {
currentURL = currentURL[9:]
}
if currentURL == "/" {
currentURL = ""
}
data = bytes.ReplaceAll(data, []byte("~GEMINICURRENTURL~"), []byte(currentURL))
autofocusValue := ""
if autofocus {
autofocusValue = "autofocus"
}
data = bytes.ReplaceAll(data, []byte("~GEMINIAUTOFOCUS~"), []byte(autofocusValue))
return data
}
func handleRequest(writer http.ResponseWriter, request *http.Request) {
defer request.Body.Close()
lastRequestTime = time.Now().Unix()
if request.URL == nil {
return
}
if request.URL.Path == "/" {
handleIndex(writer, request)
return
}
pathSplit := strings.Split(request.URL.Path, "/")
if len(pathSplit) < 2 || (pathSplit[1] != "gemini" && (!allowFileAccess || pathSplit[1] != "file")) {
writer.Write([]byte("Error: invalid protocol, only Gemini is supported"))
return
}
scheme := "gemini://"
if pathSplit[1] == "file" {
scheme = "file://"
}
u, err := url.ParseRequestURI(scheme + strings.Join(pathSplit[2:], "/"))
if err != nil {
writer.Write([]byte("Error: invalid URL"))
return
}
if request.URL.RawQuery != "" {
u.RawQuery = request.URL.RawQuery
}
inputText := request.PostFormValue("input")
if inputText != "" {
u.RawQuery = inputText
http.Redirect(writer, request, rewriteURL(u.String(), u), http.StatusSeeOther)
return
}
var header []byte
var data []byte
if scheme == "gemini://" {
header, data, err = fetch(u.String())
if err != nil {
fmt.Fprintf(writer, "Error: failed to fetch %s: %s", u, err)
return
}
} else if allowFileAccess && scheme == "file://" {
header = []byte("20 text/gemini; charset=utf-8")
data, err = ioutil.ReadFile(path.Join("/", strings.Join(pathSplit[2:], "/")))
if err != nil {
fmt.Fprintf(writer, "Error: failed to read file %s: %s", u, err)
return
}
data = Convert(data, u.String())
} else {
writer.Write([]byte("Error: invalid URL"))
return
}
if len(header) > 0 && header[0] == '3' {
split := bytes.SplitN(header, []byte(" "), 2)
if len(split) == 2 {
http.Redirect(writer, request, rewriteURL(string(split[1]), u), http.StatusSeeOther)
return
}
}
if len(header) > 3 && !bytes.HasPrefix(header[3:], []byte("text/gemini")) {
writer.Header().Set("Content-Type", string(header[3:]))
} else {
writer.Header().Set("Content-Type", "text/html; charset=utf-8")
}
writer.Write(data)
}
func handleAssets(writer http.ResponseWriter, request *http.Request) {
assetLock.Lock()
defer assetLock.Unlock()
writer.Header().Set("Cache-Control", "max-age=86400")
http.FileServer(fs).ServeHTTP(writer, request)
}
func handleBookmarks(writer http.ResponseWriter, request *http.Request) {
writer.Header().Set("Content-Type", "text/html; charset=utf-8")
var data []byte
postAddress := request.PostFormValue("address")
postLabel := request.PostFormValue("label")
if postLabel == "" && postAddress != "" {
postLabel = postAddress
}
editBookmark := request.FormValue("edit")
if editBookmark != "" {
if postLabel == "" {
label, ok := bookmarks[editBookmark]
if !ok {
writer.Write([]byte("<h1>Error: bookmark not found</h1>"))
return
}
data = newPage()
data = append(data, []byte(fmt.Sprintf(`<form method="post" action="%s"><h3>Edit bookmark</h3><input type="text" size="40" name="address" placeholder="Address" value="%s" autofocus><br><br><input type="text" size="40" name="label" placeholder="Label" value="%s"><br><br><input type="submit" value="Update"></form>`, request.URL.Path+"?"+request.URL.RawQuery, html.EscapeString(editBookmark), html.EscapeString(label)))...)
data = append(data, []byte(pageFooter)...)
writer.Write(fillTemplateVariables(data, "", false))
return
}
if editBookmark != postAddress || bookmarks[editBookmark] != postLabel {
RemoveBookmark(editBookmark)
AddBookmark(postAddress, postLabel)
}
} else if postLabel != "" {
AddBookmark(postAddress, postLabel)
}
deleteBookmark := request.FormValue("delete")
if deleteBookmark != "" {
RemoveBookmark(deleteBookmark)
}
data = newPage()
addBookmark := request.FormValue("add")
addressFocus := "autofocus"
labelFocus := ""
if addBookmark != "" {
addressFocus = ""
labelFocus = "autofocus"
}
data = append(data, []byte(fmt.Sprintf(`<form method="post" action="/bookmarks"><h3>Add bookmark</h3><input type="text" size="40" name="address" placeholder="Address" value="%s" %s><br><br><input type="text" size="40" name="label" placeholder="Label" %s><br><br><input type="submit" value="Add"></form>`, html.EscapeString(addBookmark), addressFocus, labelFocus))...)
if len(bookmarks) > 0 && addBookmark == "" {
fakeURL, _ := url.Parse("/") // Always succeeds
data = append(data, []byte(`<br><h3>Bookmarks</h3><table border="1" cellpadding="5">`)...)
for _, u := range bookmarksSorted {
data = append(data, []byte(fmt.Sprintf(`<tr><td>%s<br><a href="%s">%s</a></td><td><a href="/bookmarks?edit=%s" class="navlink">Edit</a></td><td><a href="/bookmarks?delete=%s" onclick="return confirm('Are you sure you want to delete this bookmark?')" class="navlink">Delete</a></td></tr>`, html.EscapeString(bookmarks[u]), html.EscapeString(rewriteURL(u, fakeURL)), html.EscapeString(u), html.EscapeString(url.PathEscape(u)), html.EscapeString(url.PathEscape(u))))...)
}
data = append(data, []byte(`</table>`)...)
}
data = append(data, []byte(pageFooter)...)
writer.Write(fillTemplateVariables(data, "", false))
}
// SetOnBookmarksChanged sets the function called when a bookmark is changed.
func SetOnBookmarksChanged(f func()) {
onBookmarksChanged = f
}
// StartDaemon starts the page conversion daemon.
func StartDaemon(address string, hostname string, allowFile bool) error {
daemonAddress = address
if hostname != "" {
daemonAddress = hostname
}
allowFileAccess = allowFile
loadAssets()
if len(bookmarks) == 0 {
for u, label := range defaultBookmarks {
AddBookmark(u, label)
}
}
handler := http.NewServeMux()
handler.HandleFunc("/assets/style.css", handleAssets)
handler.HandleFunc("/bookmarks", handleBookmarks)
handler.HandleFunc("/", handleRequest)
go func() {
log.Fatal(http.ListenAndServe(address, handler))
}()
return nil
}
// LastRequestTime returns the time of the last request.
func LastRequestTime() int64 {
return lastRequestTime
}
// SetClientCertificate sets the client certificate to use for a domain.
func SetClientCertificate(domain string, certificate []byte, privateKey []byte) error {
if len(certificate) == 0 || len(privateKey) == 0 {
delete(clientCerts, domain)
return nil
}
clientCert, err := tls.X509KeyPair(certificate, privateKey)
if err != nil {
return ErrInvalidCertificate
}
leafCert, err := x509.ParseCertificate(clientCert.Certificate[0])
if err == nil {
clientCert.Leaf = leafCert
}
clientCerts[domain] = clientCert
return nil
}
// AddBookmark adds a bookmark.
func AddBookmark(u string, label string) {
parsed, err := url.Parse(u)
if err != nil {
return
}
if parsed.Scheme == "" {
parsed.Scheme = "gemini"
}
parsed.Host = strings.ToLower(parsed.Host)
bookmarks[parsed.String()] = label
bookmarksUpdated()
}
// GetBookmarks returns all bookmarks.
func GetBookmarks() map[string]string {
return bookmarks
}
// RemoveBookmark removes a bookmark.
func RemoveBookmark(u string) {
delete(bookmarks, u)
bookmarksUpdated()
}
func bookmarksUpdated() {
var allURLs []string
for u := range bookmarks {
allURLs = append(allURLs, u)
}
sort.Slice(allURLs, func(i, j int) bool {
return strings.ToLower(bookmarks[allURLs[i]]) < strings.ToLower(bookmarks[allURLs[j]])
})
bookmarksSorted = allURLs
if onBookmarksChanged != nil {
onBookmarksChanged()
}
}