Collections: allow to drag and drop to change book position

internal/routes/collectionaddbookpost.go

@@ -11,6 +11,7 @@ import (
 	"git.artlef.fr/bibliomane/internal/model"
 	"git.artlef.fr/bibliomane/internal/myvalidator"
 	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
 )
 
 func PostCollectionBookHandler(ac appcontext.AppContext) {
@@ -56,7 +57,16 @@ func PostCollectionBookHandler(ac appcontext.AppContext) {
 		return
 	}
 
-	item := model.CollectionItem{Position: 0, BookID: book.ID, CollectionID: collection.ID}
+	//reorder other items
+	q := ac.Db.Model(&model.CollectionItem{})
+	q = q.Where("collection_id = ?", collection.ID)
+	err = q.UpdateColumn("position", gorm.Expr("position + 1")).Error
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	item := model.CollectionItem{Position: 1, BookID: book.ID, CollectionID: collection.ID}
 	ac.Db.Save(&item)
 	ac.C.String(http.StatusOK, "Success")
 }