feat(backend): cover/file/pages endpoints — immutable URLs, Range, disk+redis caches

backend/internal/api/books.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -10,15 +11,20 @@ import (
 	"time"
 
 	"github.com/gin-gonic/gin"
+	"github.com/jackc/pgx/v5"
 
 	"booklib/internal/bookfile"
 	"booklib/internal/store"
 )
 
 func (a *api) getBookRow(c *gin.Context, id int64) (store.Book, bool) {
-	b, perr := a.st.GetBook(c, id)
-	if perr != nil {
-		err(c, http.StatusNotFound, "not_found", "no such book")
+	b, e := a.st.GetBook(c, id)
+	if e != nil {
+		if errors.Is(e, pgx.ErrNoRows) {
+			err(c, http.StatusNotFound, "not_found", "no such book")
+			return store.Book{}, false
+		}
+		err(c, http.StatusInternalServerError, "internal", "db error")
 		return store.Book{}, false
 	}
 	return b, true