From 99f8c1188ccd1580f58ad4c21cece040ed8e874c Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Fri, 20 May 2022 17:24:52 -0600
Subject: Add RSS feed generator

---
 srv/src/http/api.go                | 21 +++++++++++--
 srv/src/http/feed.go               | 63 ++++++++++++++++++++++++++++++++++++++
 srv/src/mailinglist/mailinglist.go |  5 +--
 3 files changed, 84 insertions(+), 5 deletions(-)
 create mode 100644 srv/src/http/feed.go

(limited to 'srv/src')

diff --git a/srv/src/http/api.go b/srv/src/http/api.go
index ab0e972..83ea8ab 100644
--- a/srv/src/http/api.go
+++ b/srv/src/http/api.go
@@ -10,7 +10,9 @@ import (
 	"html/template"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/mediocregopher/blog.mediocregopher.com/srv/cfg"
@@ -40,6 +42,9 @@ type Params struct {
 	GlobalRoom       chat.Room
 	UserIDCalculator *chat.UserIDCalculator
 
+	// PublicURL is the base URL which site visitors can navigate to.
+	PublicURL *url.URL
+
 	// ListenProto and ListenAddr are passed into net.Listen to create the
 	// API's listener. Both "tcp" and "unix" protocols are explicitly
 	// supported.
@@ -57,6 +62,9 @@ type Params struct {
 
 // 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")
+
 	cfg.StringVar(&p.ListenProto, "http-listen-proto", "tcp", "Protocol to listen for HTTP requests with")
 	cfg.StringVar(&p.ListenAddr, "http-listen-addr", ":4000", "Address/path to listen for HTTP requests on")
 
@@ -76,15 +84,21 @@ func (p *Params) SetupCfg(cfg *cfg.Cfg) {
 			return fmt.Errorf("unmarshaling -http-auth-ratelimit: %w", err)
 		}
 
+		*publicURLStr = strings.TrimSuffix(*publicURLStr, "/")
+		if p.PublicURL, err = url.Parse(*publicURLStr); err != nil {
+			return fmt.Errorf("parsing -http-public-url: %w", err)
+		}
+
 		return nil
 	})
 }
 
 // Annotate implements mctx.Annotator interface.
 func (p *Params) Annotate(a mctx.Annotations) {
-	a["listenProto"] = p.ListenProto
-	a["listenAddr"] = p.ListenAddr
-	a["authRatelimit"] = p.AuthRatelimit
+	a["httpPublicURL"] = p.PublicURL
+	a["httpListenProto"] = p.ListenProto
+	a["httpListenAddr"] = p.ListenAddr
+	a["httpAuthRatelimit"] = p.AuthRatelimit
 }
 
 // API will listen on the port configured for it, and serve HTTP requests for
@@ -218,6 +232,7 @@ func (a *api) handler() http.Handler {
 
 	mux.Handle("/static/", http.FileServer(http.FS(staticFS)))
 	mux.Handle("/follow", a.renderDumbTplHandler("follow.html"))
+	mux.Handle("/feed.xml", a.renderFeedHandler())
 	mux.Handle("/", a.renderIndexHandler())
 
 	var globalHandler http.Handler = mux
diff --git a/srv/src/http/feed.go b/srv/src/http/feed.go
new file mode 100644
index 0000000..8c0ef1c
--- /dev/null
+++ b/srv/src/http/feed.go
@@ -0,0 +1,63 @@
+package http
+
+import (
+	"fmt"
+	"net/http"
+	"path/filepath"
+
+	"github.com/gorilla/feeds"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/http/apiutil"
+)
+
+func (a *api) renderFeedHandler() http.Handler {
+
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+
+		author := &feeds.Author{
+			Name: "mediocregopher",
+		}
+
+		publicURL := a.params.PublicURL.String()
+
+		feed := feeds.Feed{
+			Title:       "Mediocre Blog",
+			Link:        &feeds.Link{Href: publicURL + "/"},
+			Description: "A mix of tech, art, travel, and who knows what else.",
+			Author:      author,
+		}
+
+		recentPosts, _, err := a.params.PostStore.WithOrderDesc().Get(0, 20)
+		if err != nil {
+			apiutil.InternalServerError(rw, r, fmt.Errorf("fetching recent posts: %w", err))
+			return
+		}
+
+		for _, post := range recentPosts {
+
+			if post.PublishedAt.After(feed.Updated) {
+				feed.Updated = post.PublishedAt
+			}
+
+			if post.LastUpdatedAt.After(feed.Updated) {
+				feed.Updated = post.LastUpdatedAt
+			}
+
+			postURL := publicURL + filepath.Join("/posts", post.ID)
+
+			feed.Items = append(feed.Items, &feeds.Item{
+				Title:       post.Title,
+				Link:        &feeds.Link{Href: postURL},
+				Author:      author,
+				Description: post.Description,
+				Id:          postURL,
+				Updated:     post.LastUpdatedAt,
+				Created:     post.PublishedAt,
+			})
+		}
+
+		if err := feed.WriteAtom(rw); err != nil {
+			apiutil.InternalServerError(rw, r, fmt.Errorf("writing atom feed: %w", err))
+			return
+		}
+	})
+}
diff --git a/srv/src/mailinglist/mailinglist.go b/srv/src/mailinglist/mailinglist.go
index fc6e014..28b44b0 100644
--- a/srv/src/mailinglist/mailinglist.go
+++ b/srv/src/mailinglist/mailinglist.go
@@ -57,8 +57,9 @@ func (p *Params) SetupCfg(cfg *cfg.Cfg) {
 
 	cfg.OnInit(func(ctx context.Context) error {
 		var err error
+		*publicURLStr = strings.TrimSuffix(*publicURLStr, "/")
 		if p.PublicURL, err = url.Parse(*publicURLStr); err != nil {
-			return fmt.Errorf("parsing -public-url: %w", err)
+			return fmt.Errorf("parsing -ml-public-url: %w", err)
 		}
 
 		return nil
@@ -67,7 +68,7 @@ func (p *Params) SetupCfg(cfg *cfg.Cfg) {
 
 // Annotate implements mctx.Annotator interface.
 func (p *Params) Annotate(a mctx.Annotations) {
-	a["publicURL"] = p.PublicURL
+	a["mlPublicURL"] = p.PublicURL
 }
 
 // New initializes and returns a MailingList instance using the given Params.
-- 
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