feat(gallery): image detail view

internal/pkg/templer/middleware.go

@@ -2,8 +2,10 @@ package templer
 
 import (
 	"context"
+	"fmt"
 	"log/slog"
 	"net/http"
+	"net/url"
 	"strings"
 )
 
@@ -25,12 +27,38 @@ func Middleware(next http.Handler) http.HandlerFunc {
 	}
 }
 
-// Path returns the current path without a leading slash
+// Path returns the current path with a leading slash
 func Path(ctx context.Context) string {
 	path, ok := ctx.Value(pathKey).(string)
 	if !ok {
 		slog.Error("could not extract request path from context")
 		return ""
 	}
-	return strings.TrimPrefix(path, "/")
+	return path
+}
+
+func RelativePath(ctx context.Context, relPath string) (path string, err error) {
+	baseStr := Path(ctx)
+
+	if baseStr != "" && !strings.HasSuffix(baseStr, "/") {
+		baseStr += "/"
+	}
+
+	base, err := url.Parse(baseStr)
+	if err != nil {
+		err = fmt.Errorf("could not parse base path: %w", err)
+		return
+	}
+	rel, err := url.Parse(relPath)
+	if err != nil {
+		err = fmt.Errorf("could not parse relative path: %w", err)
+		return
+	}
+
+	// Resolve the relative path against the base
+	path = base.ResolveReference(rel).Path
+	if strings.HasSuffix(path, "/") {
+		path = path[:len(path)-1]
+	}
+	return
 }