refactor: simplify template by using a view model

Convert the raw OPDS format to a view model that
is easier to work with. Biggest change is that
we construct a single "Link" from an entry with
an array of Links with different "TypeLinks" and "Rel"
attributes.

html/feed.html

@@ -1,20 +1,24 @@
+{{define "title"}}{{.Title}}{{end}}
 {{define "content"}}
 <ul>
-    {{range .Feed.Links}}
-       <li><a href="{{.Href}}" rel="{{.Rel}}">{{.Title}}{{.Rel}}</a></li>  
+    {{if .Search }}
+       <li><a href="{{.Search}}">Search</a></li>  
     {{end}}
 
-    {{range .Feed.Entries}}
+    {{range .Navigation}}
+       <li><a href="{{.Href}}">{{.Label}}</a></li>  
+    {{end}}
+
+    {{range .Links}}
         <li class="link">
-            {{$title := .Title}}
-            {{range .Links}}
-                {{if .IsImage "image/thumbnail"}}
-                    <img src="/acquisition{{.Href}}" alt="{{$title}}" height="40">
-                {{else if .IsDownload}} 
-                    <a href="/acquisition{{.Href}}" download>{{$title}}</a>
-                {{else if .IsNavigation }}
-                    <a href="{{.Href}}">{{$title}}</a>
-                {{end}}
+            {{if .ImageURL}}
+                <img src="/acquisition{{.ImageURL}}" alt="{{.Title}}" height="40">
+            {{end}}
+
+            {{if .IsDownload}} 
+                <a href="/acquisition{{.Href}}" download>{{.Title}}</a>
+            {{else}}
+                <a href="{{.Href}}">{{.Title}}</a>
             {{end}}
         </li>
     {{end}}

html/html.go

@@ -4,6 +4,7 @@ import (
 	"embed"
 	"html/template"
 	"io"
+	"strings"
 
 	"github.com/evan-buss/kobo-opds-proxy/opds"
 )
@@ -23,12 +24,91 @@ type FeedParams struct {
 	Feed *opds.Feed
 }
 
+type FeedViewModel struct {
+	Title      string
+	Search     string
+	Navigation []NavigationViewModel
+	Links      []LinkViewModel
+}
+type NavigationViewModel struct {
+	Href  string
+	Label string
+}
+
+type LinkViewModel struct {
+	Title      string
+	ImageURL   string
+	Content    string
+	Href       string
+	IsDownload bool
+}
+
+func convertFeed(feed *opds.Feed) FeedViewModel {
+	vm := FeedViewModel{
+		Title:      feed.Title,
+		Search:     "",
+		Links:      make([]LinkViewModel, 0),
+		Navigation: make([]NavigationViewModel, 0),
+	}
+
+	for _, link := range feed.Links {
+		if link.Rel == "search" {
+			vm.Search = link.Href
+		}
+
+		if link.TypeLink == "application/atom+xml;type=feed;profile=opds-catalog" {
+			vm.Navigation = append(vm.Navigation, NavigationViewModel{
+				Href:  link.Href,
+				Label: strings.ToUpper(link.Rel[:1]) + link.Rel[1:],
+			})
+		}
+	}
+
+	for _, entry := range feed.Entries {
+		vm.Links = append(vm.Links, constructLink(entry))
+	}
+
+	return vm
+}
+
+func constructLink(entry opds.Entry) LinkViewModel {
+	vm := LinkViewModel{
+		Title:   entry.Title,
+		Content: entry.Content.Content,
+	}
+
+	for _, link := range entry.Links {
+		if link.IsNavigation() || link.IsDownload() {
+			vm.Href = link.Href
+		}
+
+		// Prefer the first "thumbnail" image we find
+		if vm.ImageURL == "" && link.IsImage("thumbnail") {
+			vm.ImageURL = link.Href
+		}
+	}
+
+	// If we didn't find a thumbnail, use the first image we find
+	if vm.ImageURL == "" {
+		for _, link := range entry.Links {
+			if link.IsImage("") {
+				vm.ImageURL = link.Href
+				break
+			}
+		}
+	}
+
+	return vm
+}
+
 func Feed(w io.Writer, p FeedParams, partial string) error {
 	if partial == "" {
 		partial = "layout.html"
 	}
 
-	return feed.ExecuteTemplate(w, partial, p)
+	vm := convertFeed(p.Feed)
+
+	return feed.ExecuteTemplate(w, partial, vm)
 }
 
 func StaticFiles() embed.FS {

html/static/style.css

@@ -18,7 +18,8 @@
 
 #container > ul > li {
   display: flex;
-  justify-content: space-between;
+  justify-content: start;
+  gap: 16px;
   align-items: center;
   padding: 0.5rem 1rem;
 }

opds/opds.go

@@ -17,22 +17,16 @@ func ParseFeed(r io.Reader) (*Feed, error) {
 	return &feed, nil
 }
 
-func (link Link) IsDownload() string {
-	if link.Rel == "http://opds-spec.org/acquisition" {
-		return link.Href
-	}
-
-	return ""
+func (link Link) IsDownload() bool {
+	return link.Rel == "http://opds-spec.org/acquisition"
 }
 
-func (link Link) IsImage(category string) string {
+func (link Link) IsImage(category string) bool {
 	if strings.HasPrefix(link.TypeLink, "image") {
-		if strings.Contains(link.Rel, category) {
-			return link.Href
-		}
+		return strings.Contains(link.Rel, category)
 	}
 
-	return ""
+	return false
 }
 
 func (link Link) IsNavigation() bool {