Collections: allow to drag and drop to change book position

internal/routes/collectionchangepositionpost.go

@@ -0,0 +1,106 @@
+package routes
+
+import (
+	"errors"
+	"net/http"
+	"strconv"
+
+	"git.artlef.fr/bibliomane/internal/appcontext"
+	"git.artlef.fr/bibliomane/internal/dto"
+	"git.artlef.fr/bibliomane/internal/i18nresource"
+	"git.artlef.fr/bibliomane/internal/model"
+	"git.artlef.fr/bibliomane/internal/myvalidator"
+	"git.artlef.fr/bibliomane/internal/query"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+func PostCollectionChangePositionHandler(ac appcontext.AppContext) {
+	collectionId, err := strconv.ParseUint(ac.C.Param("id"), 10, 64)
+	if err != nil {
+		ac.C.JSON(http.StatusBadRequest, gin.H{"error": err})
+		return
+	}
+
+	user, err := ac.GetAuthenticatedUser()
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	var collection model.Collection
+	err = ac.Db.First(&collection, collectionId).Error
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	if collection.UserID != user.ID {
+		err := myvalidator.HttpError{
+			StatusCode: http.StatusUnauthorized,
+			Err:        errors.New(i18nresource.GetTranslatedMessage(&ac, "Unauthorized")),
+		}
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	var collectionBookPosition dto.CollectionItemPosition
+	err = ac.C.ShouldBindJSON(&collectionBookPosition)
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	var item model.CollectionItem
+	err = ac.Db.First(&item, collectionBookPosition.ItemID).Error
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	if collection.ID != item.CollectionID {
+		err := myvalidator.HttpError{
+			StatusCode: http.StatusInternalServerError,
+			Err:        errors.New(i18nresource.GetTranslatedMessage(&ac, "ItemDoesNotBelongToCollection")),
+		}
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+	count, err := query.FetchCollectionBooksCount(ac.Db, user.ID, item.CollectionID)
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+	newPosition := collectionBookPosition.Position
+	if int64(newPosition) > count {
+		newPosition = uint(count)
+	}
+
+	if item.Position == collectionBookPosition.Position {
+		//nothing to do
+		ac.C.String(http.StatusOK, "Success")
+		return
+	}
+	lowerPosition := item.Position + 1
+	higherPosition := item.Position - 1
+	operationToDo := ""
+	if item.Position < collectionBookPosition.Position {
+		higherPosition = collectionBookPosition.Position
+		operationToDo = "position - 1"
+	} else {
+		lowerPosition = collectionBookPosition.Position
+		operationToDo = "position + 1"
+	}
+
+	q := ac.Db.Model(&model.CollectionItem{})
+	q = q.Where("collection_id = ? AND position BETWEEN ? AND ?", collection.ID, lowerPosition, higherPosition)
+	err = q.UpdateColumn("position", gorm.Expr(operationToDo)).Error
+	if err != nil {
+		myvalidator.ReturnErrorsAsJsonResponse(&ac, err)
+		return
+	}
+
+	item.Position = collectionBookPosition.Position
+	ac.Db.Save(&item)
+	ac.C.String(http.StatusOK, "Success")
+}