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// Package gemtext contains code related to processing and producing gemtext
// documents.
package gemtext
import (
"bufio"
"errors"
"fmt"
"io"
"net/url"
"path"
"regexp"
"strings"
)
func hasImgExt(p string) bool {
switch path.Ext(strings.ToLower(p)) {
case ".jpg", ".jpeg", ".png", ".gif", ".svg":
return true
default:
return false
}
}
// matches `=> dstURL [optional description]`
var linkRegexp = regexp.MustCompile(`^=>\s+(\S+)\s*(.*?)\s*$`)
// ToMarkdown reads a gemtext formatted body from the Reader and writes
// the markdown version of that body to the Writer.
//
// gmiGateway, if given, is used for all `gemini://` links. The `gemini://`
// prefix will be stripped, and replaced with the given URL.
func ToMarkdown(dst io.Writer, src io.Reader, gmiGateway *url.URL) error {
bufSrc := bufio.NewReader(src)
for {
line, err := bufSrc.ReadString('\n')
if err != nil && !errors.Is(err, io.EOF) {
return fmt.Errorf("reading: %w", err)
}
last := err == io.EOF
if match := linkRegexp.FindStringSubmatch(line); len(match) > 0 {
u, err := url.Parse(match[1])
if err != nil {
return fmt.Errorf("link to invalid url %q: %w", match[1], err)
}
if u.Scheme == "gemini" && gmiGateway != nil {
newUStr := gmiGateway.String() + u.Host + u.Path
if u, err = url.Parse(newUStr); err != nil {
return fmt.Errorf("parsing proxied URL %q: %w", newUStr, err)
}
}
isImg := hasImgExt(u.Path)
descr := match[2]
if descr != "" {
// ok
} else if isImg {
descr = "Image"
} else {
descr = "Link"
}
line = fmt.Sprintf("[%s](%s)\n", descr, u.String())
if isImg {
line = "!" + line
}
}
if _, err := dst.Write([]byte(line)); err != nil {
return fmt.Errorf("writing: %w", err)
}
if last {
return nil
}
}
}
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