refactor: home page / url passing

We now allow multiple OPDS feeds to be pre-defined and displayed
on the homepage. As a result we need to pass the feed navigation
URLs via query parameter rather than a subpath which would only
support proxying to a single OPDS feed.

The feed is passed via the q= query parameter and any relative
links from the OPDS XML are resolved to a complete URL with
domain / scheme.

We also check the "Content-Type" header in the response
received from the OPDS feed to determine whether to parse
an OPDS catalog or just proxy the raw response back (images / files).

.vscode/launch.json

@@ -0,0 +1,16 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Launch Package",
+            "type": "go",
+            "request": "launch",
+            "mode": "auto",
+            "program": "${workspaceFolder}"
+        }
+
+    ]
+}

html/feed.html

@@ -25,8 +25,9 @@
   {{end}}
 
   <div class="nav-controls">
+    <a tabindex="-1" href="/">Home</a>
     {{range .Navigation}}
-    <a tabindex="-1" href="{{.Href}}">{{.Label}}</a>
+    <a tabindex="-1" href="?q={{.Href}}">{{.Label}}</a>
     {{end}}
   </div>
 </nav>
@@ -35,14 +36,14 @@
   {{range .Links}}
   <li class="link">
     {{if .ImageURL}}
-    <img src="/acquisition{{.ImageURL}}" alt="{{.Title}}" height="40" />
+    <img src="?q={{.ImageURL}}" alt="{{.Title}}" height="40" />
     {{end}}
 
     <div class="info">
       {{if .IsDownload}}
-      <a href="/acquisition{{.Href}}" download>{{.Title}}</a>
+      <a href="?q={{.Href}}" download>{{.Title}}</a>
       {{else}}
-      <a href="{{.Href}}">{{.Title}}</a>
+      <a href="?q={{.Href}}">{{.Title}}</a>
       {{end}}
       <p>{{.Author}}</p>
     </div>

html/home.html

@@ -0,0 +1,9 @@
+{{define "content"}}
+<ul>
+  {{range .}}
+  <li class="link">
+    <a href="/feed?q={{.URL}}">{{.Title}}</a>
+  </li>
+  {{end}}
+</ul>
+{{end}}

html/html.go

@@ -2,8 +2,11 @@ package html
 
 import (
 	"embed"
+	"fmt"
 	"html/template"
 	"io"
+	"log"
+	"net/url"
 	"strings"
 
 	"github.com/evan-buss/kobo-opds-proxy/opds"
@@ -13,6 +16,7 @@ import (
 var files embed.FS
 
 var (
+	home = parse("home.html")
 	feed = parse("feed.html")
 )
 
@@ -21,6 +25,7 @@ func parse(file string) *template.Template {
 }
 
 type FeedParams struct {
+	URL  string
 	Feed *opds.Feed
 }
 
@@ -44,7 +49,7 @@ type LinkViewModel struct {
 	IsDownload bool
 }
 
-func convertFeed(feed *opds.Feed) FeedViewModel {
+func convertFeed(url string, feed *opds.Feed) FeedViewModel {
 	vm := FeedViewModel{
 		Title:      feed.Title,
 		Search:     "",
@@ -54,25 +59,25 @@ func convertFeed(feed *opds.Feed) FeedViewModel {
 
 	for _, link := range feed.Links {
 		if link.Rel == "search" {
-			vm.Search = link.Href
+			vm.Search = resolveHref(url, link.Href)
 		}
 
 		if link.TypeLink == "application/atom+xml;type=feed;profile=opds-catalog" {
 			vm.Navigation = append(vm.Navigation, NavigationViewModel{
-				Href:  link.Href,
+				Href:  resolveHref(url, link.Href),
 				Label: strings.ToUpper(link.Rel[:1]) + link.Rel[1:],
 			})
 		}
 	}
 
 	for _, entry := range feed.Entries {
-		vm.Links = append(vm.Links, constructLink(entry))
+		vm.Links = append(vm.Links, constructLink(url, entry))
 	}
 
 	return vm
 }
 
-func constructLink(entry opds.Entry) LinkViewModel {
+func constructLink(url string, entry opds.Entry) LinkViewModel {
 	vm := LinkViewModel{
 		Title:   entry.Title,
 		Content: entry.Content.Content,
@@ -87,13 +92,12 @@ func constructLink(entry opds.Entry) LinkViewModel {
 	for _, link := range entry.Links {
 		vm.IsDownload = link.IsDownload()
 		if link.IsNavigation() || link.IsDownload() {
-			vm.Href = link.Href
+			vm.Href = resolveHref(url, link.Href)
-
 		}
 
 		// Prefer the first "thumbnail" image we find
 		if vm.ImageURL == "" && link.IsImage("thumbnail") {
-			vm.ImageURL = link.Href
+			vm.ImageURL = resolveHref(url, link.Href)
 		}
 	}
 
@@ -101,7 +105,7 @@ func constructLink(entry opds.Entry) LinkViewModel {
 	if vm.ImageURL == "" {
 		for _, link := range entry.Links {
 			if link.IsImage("") {
-				vm.ImageURL = link.Href
+				vm.ImageURL = resolveHref(url, link.Href)
 				break
 			}
 		}
@@ -109,17 +113,40 @@ func constructLink(entry opds.Entry) LinkViewModel {
 
 	return vm
 }
+func resolveHref(feedUrl string, relativePath string) string {
+	baseUrl, err := url.Parse(feedUrl)
+	if err != nil {
+		log.Fatal(err)
+	}
+	relativeUrl, err := url.Parse(relativePath)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	resolved := baseUrl.ResolveReference(relativeUrl).String()
+	fmt.Println("Resolved URL: ", resolved)
+	return resolved
+}
 
 func Feed(w io.Writer, p FeedParams, partial string) error {
 	if partial == "" {
 		partial = "layout.html"
 	}
 
-	vm := convertFeed(p.Feed)
+	vm := convertFeed(p.URL, p.Feed)
 
 	return feed.ExecuteTemplate(w, partial, vm)
 }
 
+type FeedInfo struct {
+	Title string
+	URL   string
+}
+
+func Home(w io.Writer, p []FeedInfo) error {
+	return home.ExecuteTemplate(w, "layout.html", p)
+}
+
 func StaticFiles() embed.FS {
 	return files
 }

main.go

@@ -4,6 +4,7 @@ import (
 	"io"
 	"log"
 	"log/slog"
+	"mime"
 	"net/http"
 	"time"
 
@@ -11,55 +12,78 @@ import (
 	"github.com/evan-buss/kobo-opds-proxy/opds"
 )
 
-const baseUrl = "http://calibre.terminus"
-
 func main() {
 	router := http.NewServeMux()
-	router.HandleFunc("GET /", handleFeed())
+	router.HandleFunc("GET /{$}", handleHome())
-	router.HandleFunc("GET /acquisition/{path...}", handleAcquisition())
+	router.HandleFunc("GET /feed", handleFeed())
 	router.Handle("GET /static/", http.FileServer(http.FS(html.StaticFiles())))
 
 	slog.Info("Starting server", slog.String("port", "8080"))
 	log.Fatal(http.ListenAndServe(":8080", router))
 }
 
-func handleFeed() http.HandlerFunc {
+func handleHome() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		opdsUrl := baseUrl + r.URL.RequestURI()
+		slog.Info("Rendering home page")
-
+		feeds := []html.FeedInfo{
-		slog.Info("Fetching feed", slog.String("path", opdsUrl))
+			{
-
+				Title: "Evan's Library",
-		feed, err := fetchFeed(opdsUrl)
+				URL:   "http://calibre.terminus/opds",
-		if err != nil {
+			},
-			slog.Error("Failed to parse feed", slog.String("path", r.URL.RawPath), slog.Any("error", err))
+			{
-			http.Error(w, "An unexpected error occurred", http.StatusInternalServerError)
+				Title: "Project Gutenberg",
-			return
+				URL:   "https://m.gutenberg.org/ebooks.opds/",
-		}
+			},
-
-		err = html.Feed(w, html.FeedParams{Feed: feed}, "")
-		if err != nil {
-			slog.Error("Failed to render feed", slog.String("path", r.URL.RawPath), slog.Any("error", err))
-			http.Error(w, "An unexpected error occurred", http.StatusInternalServerError)
-			return
 		}
+		html.Home(w, feeds)
 	}
 }
 
-func handleAcquisition() http.HandlerFunc {
+func handleFeed() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		opdsUrl := baseUrl + "/" + r.PathValue("path")
+		queryURL := r.URL.Query().Get("q")
-		resp, err := fetchFromUrl(opdsUrl)
+		if queryURL == "" {
-		if err != nil {
+			http.Error(w, "No feed specified", http.StatusBadRequest)
-			slog.Error("Failed to fetch acquisition", slog.String("path", opdsUrl), slog.Any("error", err))
-			http.Error(w, "An unexpected error occurred", http.StatusInternalServerError)
 			return
 		}
 
+		slog.Info("Fetching feed", slog.String("path", queryURL))
+
+		resp, err := fetchFromUrl(queryURL)
+		if err != nil {
+			handleError(r, w, "Failed to fetch feed", err)
+			return
+		}
+
+		defer resp.Body.Close()
+
+		contentType := resp.Header.Get("Content-Type")
+		mimeType, _, err := mime.ParseMediaType(contentType)
+		if err != nil {
+			handleError(r, w, "Failed to parse content type", err)
+		}
+
+		if mimeType == "application/atom+xml" {
+			feed, err := opds.ParseFeed(resp.Body)
+
+			if err != nil {
+				handleError(r, w, "Failed to parse feed", err)
+				return
+			}
+
+			err = html.Feed(w, html.FeedParams{URL: queryURL, Feed: feed}, "")
+			if err != nil {
+				handleError(r, w, "Failed to render feed", err)
+				return
+			}
+		}
+
 		for k, v := range resp.Header {
 			w.Header()[k] = v
 		}
 
 		io.Copy(w, resp.Body)
+
 	}
 }
 
@@ -77,12 +101,7 @@ func fetchFromUrl(url string) (*http.Response, error) {
 	return client.Do(req)
 }
 
-func fetchFeed(url string) (*opds.Feed, error) {
+func handleError(r *http.Request, w http.ResponseWriter, message string, err error) {
-	r, err := fetchFromUrl(url)
+	slog.Error(message, slog.String("path", r.URL.RawPath), slog.Any("error", err))
-	if err != nil {
+	http.Error(w, "An unexpected error occurred", http.StatusInternalServerError)
-		return nil, err
-	}
-	defer r.Body.Close()
-
-	return opds.ParseFeed(r.Body)
 }

opds/opds.go

@@ -22,7 +22,7 @@ func (link Link) IsDownload() bool {
 }
 
 func (link Link) IsImage(category string) bool {
-	if strings.HasPrefix(link.TypeLink, "image") {
+	if strings.HasPrefix(link.TypeLink, "image") && !strings.HasPrefix(link.Href, "data") {
 		return strings.Contains(link.Rel, category)
 	}
 
@@ -30,5 +30,5 @@ func (link Link) IsImage(category string) bool {
 }
 
 func (link Link) IsNavigation() bool {
-	return link.TypeLink == "application/atom+xml;type=feed;profile=opds-catalog"
+	return link.TypeLink == "application/atom+xml;type=feed;profile=opds-catalog" || link.Rel == "subsection"
 }