Automatically bridge gemini links to a gateway on http site

flake.nix

@@ -43,6 +43,7 @@
         export MEDIOCRE_BLOG_HTTP_PUBLIC_URL="$MEDIOCRE_BLOG_ML_PUBLIC_URL"
         export MEDIOCRE_BLOG_HTTP_LISTEN_PROTO="tcp"
         export MEDIOCRE_BLOG_HTTP_LISTEN_ADDR=":4000"
+        export MEDIOCRE_BLOG_HTTP_GEMINI_GATEWAY_URL="https://nightfall.city/x/"
 
         # http auth
         # (password is "bar". This should definitely be changed for prod.)

src/cmd/load-test-data/test-data.yml

@@ -104,6 +104,12 @@ published_posts:
 
       Edgy.
 
+      => / Here's a link within the site
+
+      => gemini://mediocregopher.com And here's a link to a gemini capsule
+
+      => https://mediocregopher.com And here's a link to an https site
+
       #### Side-note
 
       Did you know that the terms "cyberspace" and "matrix" are attributable to a book from 1984 called _Neuromancer_?
@@ -117,8 +123,6 @@ published_posts:
 
       This has been a great post.
 
-      => / Here's a link outa here!
-
   - id: empty-markdown-test
     title: Empty Markdown Test
     description:

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, u.String())
-
-			line = fmt.Sprintf("[%s](%s)\n", descr, match[1])
 
 			if isImg {
 				line = "!" + line

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())
 		})

src/http/http.go

@@ -56,12 +56,17 @@ type Params struct {
 	// AuthRatelimit indicates how much time must pass between subsequent auth
 	// attempts.
 	AuthRatelimit time.Duration
+
+	// GeminiGatewayURL will be used to translate links for `gemini://` into
+	// `http(s)://`. See gmi.GemtextToMarkdown.
+	GeminiGatewayURL *url.URL
 }
 
 // SetupCfg implement the cfg.Cfger interface.
 func (p *Params) SetupCfg(cfg *cfg.Cfg) {
 
 	publicURLStr := cfg.String("http-public-url", "http://localhost:4000", "URL this service is accessible at")
+	geminiGatewayURLStr := cfg.String("http-gemini-gateway-url", "", "Optional URL to prefix to all gemini:// links, to make them accessible over https")
 
 	cfg.StringVar(&p.ListenProto, "http-listen-proto", "tcp", "Protocol to listen for HTTP requests with")
 	cfg.StringVar(&p.ListenAddr, "http-listen-addr", ":4000", "Address/unix socket path to listen for HTTP requests on")
@@ -87,6 +92,12 @@ func (p *Params) SetupCfg(cfg *cfg.Cfg) {
 			return fmt.Errorf("parsing -http-public-url: %w", err)
 		}
 
+		if *geminiGatewayURLStr != "" {
+			if p.GeminiGatewayURL, err = url.Parse(*geminiGatewayURLStr); err != nil {
+				return fmt.Errorf("parsing -http-gemini-gateway-url: %w", err)
+			}
+		}
+
 		return nil
 	})
 }

src/http/posts.go

@@ -96,7 +96,11 @@ func (a *api) postToPostTplPayload(storedPost post.StoredPost) (postTplPayload,
 		prevBodyBuf := bodyBuf
 		bodyBuf = new(bytes.Buffer)
 
-		if err := gmi.GemtextToMarkdown(bodyBuf, prevBodyBuf); err != nil {
+		err := gmi.GemtextToMarkdown(
+			bodyBuf, prevBodyBuf, a.params.GeminiGatewayURL,
+		)
+
+		if err != nil {
 			return postTplPayload{}, fmt.Errorf("converting gemtext to markdown: %w", err)
 		}
 	}