Automatically bridge gemini links to a gateway on http site

2 files changed, 37 insertions, 7 deletions

diff --git a/src/gmi/gemtext.go b/src/gmi/gemtext.go
index a1136bd..3e5f6fc 100644
--- a/src/gmi/gemtext.go
+++ b/src/gmi/gemtext.go
@@ -5,8 +5,9 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"log"
+	"net/url"
 	"path"
+	"path/filepath"
 	"regexp"
 	"strings"
 )
@@ -25,7 +26,10 @@ var linkRegexp = regexp.MustCompile(`^=>\s+(\S+)\s*(.*?)\s*$`)
 
 // GemtextToMarkdown reads a gemtext formatted body from the Reader and writes
 // the markdown version of that body to the Writer.
-func GemtextToMarkdown(dst io.Writer, src io.Reader) error {
+//
+// gmiGateway, if given, is used for all `gemini://` links. The `gemini://`
+// prefix will be stripped, and replaced with the given URL.
+func GemtextToMarkdown(dst io.Writer, src io.Reader, gmiGateway *url.URL) error {
 
 	bufSrc := bufio.NewReader(src)
 
@@ -40,7 +44,20 @@ func GemtextToMarkdown(dst io.Writer, src io.Reader) error {
 
 		if match := linkRegexp.FindStringSubmatch(line); len(match) > 0 {
 
-			isImg := hasImgExt(match[1])
+			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 {
+
+				newU := *gmiGateway
+				newU.Path = filepath.Join(newU.Path, u.Host, u.Path)
+				newU.RawQuery = u.RawQuery
+				u = &newU
+			}
+
+			isImg := hasImgExt(u.Path)
 
 			descr := match[2]
 
@@ -52,9 +69,7 @@ func GemtextToMarkdown(dst io.Writer, src io.Reader) error {
 				descr = "Link"
 			}
 
-			log.Printf("descr:%q", descr)
-
-			line = fmt.Sprintf("[%s](%s)\n", descr, match[1])
+			line = fmt.Sprintf("[%s](%s)\n", descr, u.String())
 
 			if isImg {
 				line = "!" + line
diff --git a/src/gmi/gemtext_test.go b/src/gmi/gemtext_test.go
index 23cb97f..75da9df 100644
--- a/src/gmi/gemtext_test.go
+++ b/src/gmi/gemtext_test.go
@@ -2,6 +2,7 @@ package gmi
 
 import (
 	"bytes"
+	"net/url"
 	"strconv"
 	"testing"
 
@@ -10,6 +11,8 @@ import (
 
 func TestGemtextToMarkdown(t *testing.T) {
 
+	gmiGateway, _ := url.Parse("https://gateway.com/x/")
+
 	tests := []struct {
 		in, exp string
 	}{
@@ -37,13 +40,25 @@ func TestGemtextToMarkdown(t *testing.T) {
 			in:  "=> img.png description is here   ",
 			exp: "![description is here](img.png)\n",
 		},
+		{
+			in:  "=> gemini://somewhere.com/foo Somewhere",
+			exp: "[Somewhere](https://gateway.com/x/somewhere.com/foo)\n",
+		},
+		{
+			in:  "=> gemini://somewhere.com:420/foo Somewhere",
+			exp: "[Somewhere](https://gateway.com/x/somewhere.com:420/foo)\n",
+		},
+		{
+			in:  "=> gemini://somewhere.com:420/foo?bar=baz Somewhere",
+			exp: "[Somewhere](https://gateway.com/x/somewhere.com:420/foo?bar=baz)\n",
+		},
 	}
 
 	for i, test := range tests {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 
 			got := new(bytes.Buffer)
-			err := GemtextToMarkdown(got, bytes.NewBufferString(test.in))
+			err := GemtextToMarkdown(got, bytes.NewBufferString(test.in), gmiGateway)
 			assert.NoError(t, err)
 			assert.Equal(t, test.exp, got.String())
 		})