view: Replace edit by view parameter

The old edit URL parameter allowed to select one different HTML
template. A more generic approach is to provide a view parameter which
allows to use multiple alternative HTML templates for the same data
defined by the Go struct.

This makes implementing additional pages like a confirm page for recipe
deletion easier.

2 files changed, 25 insertions, 6 deletions

diff --git a/view/html/recipe.html b/view/html/recipe.html
index a6588e6..43bbb2e 100644
--- a/view/html/recipe.html
+++ b/view/html/recipe.html
@@ -13,7 +13,7 @@
 			<p>Portions: {{.Portions}}</p>
 			<p><a href="{{.Url}}">original recipe</a></p>
 			<p>{{.Notes}}</p>
-			<a href="/recipe/{{.Id}}?edit=true"><button>edit</button></a>
+			<a href="/recipe/{{.Id}}?view=recipe-edit"><button>edit</button></a>
 		</main>
 		{{ template "footer" }}
 	</body>
diff --git a/view/recipe.go b/view/recipe.go
index 1dd6045..25abc6b 100644
--- a/view/recipe.go
+++ b/view/recipe.go
@@ -18,13 +18,32 @@ func Recipe(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	tmpl := "recipe"
-	edit, ok := r.URL.Query()["edit"]
-	if ok && len(edit) == 1 && edit[0] == "true" {
-		tmpl = "recipe-edit"
+	template := "recipe"
+	view, ok := r.URL.Query()["view"]
+	if ok {
+		if len(view) > 1 {
+			http.Error(w, "More than one 'view' parameter given in URL", http.StatusBadRequest)
+			return
+		}
+		template = view[0]
 	}
 
-	err = html.ExecuteTemplate(w, tmpl, recipe)
+	is_valid := false
+	valid_templates := []string{
+		"recipe",
+		"recipe-edit",
+	}
+	for _, v := range valid_templates {
+		if template == v {
+			is_valid = true
+		}
+	}
+	if !is_valid {
+		http.Error(w, "Unsupported view: " + template, http.StatusBadRequest)
+		return
+	}
+
+	err = html.ExecuteTemplate(w, template, recipe)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return