From 4a5dad998cf97b879e88c8dc1ce025432dfc90cb Mon Sep 17 00:00:00 2001
From: tjpcc <tjp@ctrl-c.club>
Date: Sat, 26 Aug 2023 09:22:25 -0600
Subject: AutoAtom: middleware that supports adding .atom to any gemtext path

---
 gemini/gemtext/sub.go      | 49 ++++++++++++++++++++++++++++++
 gemini/gemtext/sub_test.go | 75 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+)

(limited to 'gemini')

diff --git a/gemini/gemtext/sub.go b/gemini/gemtext/sub.go
index 365d41b..5030291 100644
--- a/gemini/gemtext/sub.go
+++ b/gemini/gemtext/sub.go
@@ -2,13 +2,18 @@ package gemtext
 
 import (
 	"bytes"
+	"context"
 	"html/template"
 	"io"
+	"mime"
 	"net/url"
 	"regexp"
 	"strconv"
 	"strings"
 	"time"
+
+	"tildegit.org/tjp/sliderule/gemini"
+	"tildegit.org/tjp/sliderule/internal/types"
 )
 
 // GmisubToAtom converts a gemini document to Atom format.
@@ -28,6 +33,50 @@ func GmisubToAtom(doc Document, location url.URL, out io.Writer) error {
 	return nil
 }
 
+// AutoAtom is a middleware which builds atom feeds for any gemtext pages.
+//
+// It looks for requests ending with the '.atom' extension, passes through the request
+// with the extension clipped off, then if the response is in gemtext it converts it to
+// an Atom feed according to the gmisub spec at
+// gemini://gemini.circumlunar.space/docs/companion/subscription.gmi
+var AutoAtom = types.Middleware(func(h types.Handler) types.Handler {
+	return types.HandlerFunc(func(ctx context.Context, request *types.Request) *types.Response {
+		if !strings.HasSuffix(request.Path, ".atom") {
+			return h.Handle(ctx, request)
+		}
+
+		req := *request
+		u := *request.URL
+		u.Path = strings.TrimSuffix(u.Path, ".atom")
+		req.URL = &u
+
+		response := h.Handle(ctx, &req)
+		if response.Status != gemini.StatusSuccess {
+			return response
+		}
+
+		mtype, _, err := mime.ParseMediaType(response.Meta.(string))
+		if err != nil || mtype != "text/gemini" {
+			return response
+		}
+
+		defer func() {
+			_ = response.Close()
+		}()
+
+		doc, err := Parse(response.Body)
+		if err != nil {
+			return gemini.Failure(err)
+		}
+
+		buf := &bytes.Buffer{}
+		if err := GmisubToAtom(doc, *request.URL, buf); err != nil {
+			return gemini.Failure(err)
+		}
+		return gemini.Success("application/atom+xml; charset=utf-8", buf)
+	})
+})
+
 type gmiSub struct {
 	ID       template.URL
 	Title    string
diff --git a/gemini/gemtext/sub_test.go b/gemini/gemtext/sub_test.go
index f080705..9e0fcc8 100644
--- a/gemini/gemtext/sub_test.go
+++ b/gemini/gemtext/sub_test.go
@@ -2,8 +2,15 @@ package gemtext
 
 import (
 	"bytes"
+	"context"
+	"fmt"
+	"io"
 	"net/url"
 	"testing"
+
+	"tildegit.org/tjp/sliderule"
+	"tildegit.org/tjp/sliderule/gemini"
+	"tildegit.org/tjp/sliderule/internal/types"
 )
 
 func TestGemsubToAtom(t *testing.T) {
@@ -61,3 +68,71 @@ func TestGemsubToAtom(t *testing.T) {
 		})
 	}
 }
+
+func TestAutoAtom(t *testing.T) {
+	rout := &sliderule.Router{}
+
+	rout.Route("/foo.gmi", types.HandlerFunc(func(ctx context.Context, request *types.Request) *types.Response {
+		return gemini.Success("text/gemini", bytes.NewBufferString(`
+# This is my gemini page
+
+## a subtitle
+
+=> ./first-post.gmi 2023-05-17 - My first post
+=> ./second-post.gmi 2023-06-02 second-ever post
+`[1:]))
+	}))
+
+	rout.Route("/bar.gmi", types.HandlerFunc(func(ctx context.Context, request *types.Request) *types.Response {
+		return gemini.Success("text/gemini", bytes.NewBufferString(`
+# Another homepage
+
+=> ./first-post.gmi 2023-05-17 - first post
+=> ./second-post.gmi 2023-06-02 second post
+`[1:]))
+	}))
+
+	h := AutoAtom(rout.Handler())
+
+	response := h.Handle(context.Background(), &types.Request{URL: &url.URL{
+		Scheme: "gemini",
+		Host:   "127.0.0.1",
+		Path:   "/foo.gmi.atom",
+	}})
+	if response.Status != gemini.StatusSuccess {
+		t.Fatal("bad response code")
+	}
+
+	result, err := io.ReadAll(response.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	target := `
+<?xml version="1.0" encoding="utf-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+  <id>gemini://127.0.0.1/foo.gmi.atom</id>
+  <link href="gemini://127.0.0.1/foo.gmi.atom"/>
+  <title>This is my gemini page</title>
+  <subtitle>a subtitle</subtitle>
+  <updated>2023-06-02T12:00:00Z</updated>
+  <entry>
+    <id>./first-post.gmi</id>
+    <link rel="alternate" href="./first-post.gmi"/>
+    <title>My first post</title>
+    <updated>2023-05-17T12:00:00Z</updated>
+  </entry>
+  <entry>
+    <id>./second-post.gmi</id>
+    <link rel="alternate" href="./second-post.gmi"/>
+    <title>second-ever post</title>
+    <updated>2023-06-02T12:00:00Z</updated>
+  </entry>
+</feed>
+`[1:]
+	if string(result) != target {
+		fmt.Println(target)
+		fmt.Println(string(result))
+		t.Fatal("response body")
+	}
+}
-- 
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