From 178c688203797ed741f410d58318abf0cf10c0e5 Mon Sep 17 00:00:00 2001
From: Arthur Lefebvre <artlef@protonmail.com>
Date: Sun, 12 Apr 2026 01:44:25 +0200
Subject: [PATCH] Collections: allow to drag and drop to change book position

---
 demodata.sql                                  |  12 +-
 front/src/CollectionForm.vue                  |  54 ++++++++-
 front/src/CollectionFormElement.vue           |  14 ++-
 front/src/api.js                              |  10 +-
 internal/adapter/adapter.go                   |   1 +
 internal/apitest/fetchallcollections_test.go  |   4 +-
 .../post_collection_changeposition_test.go    | 113 ++++++++++++++++++
 internal/dto/in.go                            |   5 +
 internal/dto/out.go                           |   1 +
 internal/i18nresource/locale.en.toml          |   1 +
 internal/i18nresource/locale.fr.toml          |   1 +
 internal/query/querycollections.go            |   3 +-
 internal/routes/collectionaddbookpost.go      |  12 +-
 .../routes/collectionchangepositionpost.go    | 106 ++++++++++++++++
 internal/setup/setup.go                       |   3 +
 15 files changed, 328 insertions(+), 12 deletions(-)
 create mode 100644 internal/apitest/post_collection_changeposition_test.go
 create mode 100644 internal/routes/collectionchangepositionpost.go

diff --git a/demodata.sql b/demodata.sql
index 6c5cdee..3ea576a 100644
--- a/demodata.sql
+++ b/demodata.sql
@@ -131,6 +131,7 @@ INSERT INTO collections(name, user_id) VALUES ('Littérature française',(SELECT
 INSERT INTO collections(name, user_id) VALUES ('Nouvelles',(SELECT id FROM users WHERE name = 'demo'));
 INSERT INTO collections(name, user_id) VALUES ('Non fiction',(SELECT id FROM users WHERE name = 'demo2'));
 INSERT INTO collections(name, user_id) VALUES ('Empty',(SELECT id FROM users WHERE name = 'demo'));
+INSERT INTO collections(name, user_id) VALUES ('Lu récemment',(SELECT id FROM users WHERE name = 'demo'));
 
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Littérature française'), (SELECT id FROM books WHERE title = 'Nord'), 1);
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Littérature française'), (SELECT id FROM books WHERE title = 'Gargantua'), 2);
@@ -142,8 +143,17 @@ INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT i
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Nouvelles'), (SELECT id FROM books WHERE title = 'Dojoji et autres nouvelles'), 1);
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Nouvelles'), (SELECT id FROM books WHERE title = 'Le meurtre d''O-tsuya'), 2);
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Nouvelles'), (SELECT id FROM books WHERE title = 'Le coup de pistolet'), 3);
-INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Nouvelles'), (SELECT id FROM books WHERE title = 'Duo'), 3);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Nouvelles'), (SELECT id FROM books WHERE title = 'Duo'), 4);
 
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Non fiction'), (SELECT id FROM books WHERE title = 'Recherches philosophiques'), 1);
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Non fiction'), (SELECT id FROM books WHERE title = 'De sang-froid'), 2);
 INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Non fiction'), (SELECT id FROM books WHERE title = 'The Life of Jesus'), 3);
+
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'L''Homme sans qualités, tome 1'), 1);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Iliade'), 2);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Duo'), 3);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'De sang-froid'), 4);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Le Pavillon d''or'), 5);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Recherches philosophiques'), 6);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Dojoji et autres nouvelles'), 7);
+INSERT INTO collection_items(collection_id, book_id, position) VALUES ((SELECT id FROM collections WHERE name = 'Lu récemment'), (SELECT id FROM books WHERE title = 'Le château'), 8);
diff --git a/front/src/CollectionForm.vue b/front/src/CollectionForm.vue
index 1c25056..bdcd2c2 100644
--- a/front/src/CollectionForm.vue
+++ b/front/src/CollectionForm.vue
@@ -1,6 +1,6 @@
 <script setup>
 import { computed, ref } from 'vue'
-import { getCollection } from './api.js'
+import { getCollection, postCollectionChangePosition } from './api.js'
 import CollectionFormElement from './CollectionFormElement.vue'
 import AddBookToCollection from './AddBookToCollection.vue'
 import Pagination from './Pagination.vue'
@@ -17,6 +17,10 @@ const offset = computed(() => (pageNumber.value - 1) * limit)
 const data = ref(null)
 const error = ref(null)
 
+const itemIdBeingGrabbed = ref(null)
+
+const itemIdBeingOvered = ref(null)
+
 let totalElementsNumber = computed(() =>
   typeof data != 'undefined' && data.value != null ? data.value['count'] : 0,
 )
@@ -35,15 +39,59 @@ function pageChange(newPageNumber) {
 function fetchCollection() {
   pageChange(1)
 }
+
+function onDragStart(event, id) {
+  event.dataTransfer.effectAllowed = 'move'
+  // Custom type to identify a collectionitem drag
+  event.dataTransfer.setData('collectionitem', '')
+  itemIdBeingGrabbed.value = id
+}
+
+function onDragover(event) {
+  if (event.dataTransfer.types.includes('collectionitem')) {
+    event.preventDefault()
+  }
+}
+
+function onDrop(id, position) {
+  if (id == itemIdBeingGrabbed.value) {
+    //nothing to do
+    return
+  }
+  postCollectionChangePosition(props.id, itemIdBeingGrabbed.value, position).then((res) => {
+    if (res.ok) {
+      fetchCollection()
+    } else {
+      res.json().then((json) => {
+        error.value = json
+      })
+    }
+  })
+}
+
+function onDragend() {
+  itemIdBeingGrabbed.value = null
+  itemIdBeingOvered.value = null
+}
 </script>
 
 <template>
-  <div v-if="error">{{ $t('bookform.error', { error: error.message }) }}</div>
+  <div v-if="error">{{ $t('collection.error', { error: error }) }}</div>
   <div v-if="data">
     <h2 class="title">{{ data.name }}</h2>
     <AddBookToCollection :collection-id="props.id" @created="fetchCollection" />
     <div>
-      <CollectionFormElement v-for="item in data.items" :key="item.id" v-bind="item" />
+      <CollectionFormElement
+        @drop="onDrop(item.id, item.position)"
+        @dragstart="(e) => onDragStart(e, item.id)"
+        @dragend="onDragend"
+        @dragover="onDragover"
+        @dragenter="itemIdBeingOvered = item.id"
+        v-for="item in data.items"
+        :key="item.id"
+        :is-dragover="itemIdBeingOvered === item.id"
+        v-bind="item"
+      />
     </div>
     <Pagination
       class="mt-5"
diff --git a/front/src/CollectionFormElement.vue b/front/src/CollectionFormElement.vue
index 9b56413..86c0aa8 100644
--- a/front/src/CollectionFormElement.vue
+++ b/front/src/CollectionFormElement.vue
@@ -2,12 +2,14 @@
 import BookListElement from './BookListElement.vue'
 
 const props = defineProps({
+  isDragover: Boolean,
+  id: Number,
   position: Number,
   book: Array,
 })
 </script>
 <template>
-  <div class="collectionitembox">
+  <div :class="isDragover ? 'dragover' : ''" draggable="true" class="collectionitembox">
     <BookListElement v-bind="props.book">
       <div class="separator" />
       <div class="positionindicator centered is-narrow">
@@ -50,9 +52,15 @@ const props = defineProps({
   margin-right: 30px;
   border-top-right-radius: var(--bulma-box-radius);
   border-bottom-right-radius: var(--bulma-box-radius);
+  cursor: grab;
 }
 
-.positionwidget:hover {
-  cursor: move;
+.positionwidget:active {
+  cursor: grabbing;
+}
+
+.dragover {
+  border: 3px solid var(--bulma-primary);
+  border-radius: 10px;
 }
 </style>
diff --git a/front/src/api.js b/front/src/api.js
index edffebd..a1db6fa 100644
--- a/front/src/api.js
+++ b/front/src/api.js
@@ -130,7 +130,7 @@ export function postCollection(collection) {
   return genericPayloadCall('/ws/collection', collection, 'POST')
 }
 
-export function postCollectionAddBook(collectionId, bookId) {
+export function postCollectionAddBook(collectionId, position) {
   return genericPayloadCall(
     '/ws/collection/' + collectionId + '/addbook',
     { bookId: bookId },
@@ -138,6 +138,14 @@ export function postCollectionAddBook(collectionId, bookId) {
   )
 }
 
+export function postCollectionChangePosition(collectionId, itemId, position) {
+  return genericPayloadCall(
+    '/ws/collection/' + collectionId + '/changeposition',
+    { itemId: itemId, position: position },
+    'POST',
+  )
+}
+
 export function putBook(id, book) {
   return genericPayloadCall('/ws/book/edit/' + id, book.value, 'PUT')
 }
diff --git a/internal/adapter/adapter.go b/internal/adapter/adapter.go
index bef0656..1f7d4ab 100644
--- a/internal/adapter/adapter.go
+++ b/internal/adapter/adapter.go
@@ -28,6 +28,7 @@ func CollectionItemsQueryToDto(itemsQueryResult []query.CollectionItemQueryResul
 		}
 		dtoItems = append(dtoItems,
 			dto.CollectionItemGet{
+				ID:       queryResult.ItemID,
 				Position: queryResult.Position,
 				Book:     bookItem,
 			})
diff --git a/internal/apitest/fetchallcollections_test.go b/internal/apitest/fetchallcollections_test.go
index d01fa93..4eadc6d 100644
--- a/internal/apitest/fetchallcollections_test.go
+++ b/internal/apitest/fetchallcollections_test.go
@@ -12,8 +12,8 @@ import (
 func TestFetchAllCollections_OK(t *testing.T) {
 	status, res := testFetchCollections(t, "10", "0")
 	assert.Equal(t, http.StatusOK, status)
-	assert.Equal(t, int64(3), res.Count)
-	assert.Equal(t, 3, len(res.Collections))
+	assert.Equal(t, int64(4), res.Count)
+	assert.Equal(t, 4, len(res.Collections))
 }
 
 func testFetchCollections(t *testing.T, limit string, offset string) (int, dto.CollectionItemsGet) {
diff --git a/internal/apitest/post_collection_changeposition_test.go b/internal/apitest/post_collection_changeposition_test.go
new file mode 100644
index 0000000..711ca3f
--- /dev/null
+++ b/internal/apitest/post_collection_changeposition_test.go
@@ -0,0 +1,113 @@
+package apitest
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"git.artlef.fr/bibliomane/internal/testutils"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPostCollectionChangePositionHandler_PositionOk(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 14,
+			"position": 2
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusOK, status)
+	_, collection := testGetCollection(t, collectionId, "10", "0")
+	assert.Equal(t, uint(1), collection.Items[0].Position)
+	assert.Equal(t, uint(2), collection.Items[1].Position)
+	assert.Equal(t, uint(3), collection.Items[2].Position)
+	assert.Equal(t, uint(4), collection.Items[3].Position)
+}
+
+func TestPostCollectionChangePositionHandler_ChangeOtherElement(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 17,
+			"position": 3
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusOK, status)
+	_, collection := testGetCollection(t, collectionId, "10", "0")
+	assert.Equal(t, "Duo", collection.Items[3].Book.Title)
+}
+
+func TestPostCollectionChangePositionHandler_LastPosition(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 19,
+			"position": 546
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusOK, status)
+	_, collection := testGetCollection(t, collectionId, "10", "0")
+	assert.Equal(t, "Recherches philosophiques", collection.Items[7].Book.Title)
+	assert.Equal(t, "Le château", collection.Items[6].Book.Title)
+}
+
+func TestPostCollectionChangePositionHandler_FirstPosition(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 16,
+			"position": 1
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusOK, status)
+	_, collection := testGetCollection(t, collectionId, "10", "0")
+	assert.Equal(t, "Duo", collection.Items[0].Book.Title)
+}
+
+func TestPostCollectionChangePositionHandler_WrongPosition(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 9,
+			"position": 0
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusBadRequest, status)
+}
+
+func TestPostCollectionChangePositionHandler_MissingPosition(t *testing.T) {
+	payload :=
+		`{
+			"itemId": 9
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusBadRequest, status)
+}
+
+func TestPostCollectionChangePositionWrongCollection(t *testing.T) {
+	payload :=
+		`{
+		  "itemId": 1,
+			"position": 9
+		}`
+	collectionId := "5"
+	status := testPostCollectionChangePositionHandler(collectionId, payload)
+	assert.Equal(t, http.StatusInternalServerError, status)
+}
+
+func testPostCollectionChangePositionHandler(collectionId string, payload string) int {
+	router := testutils.TestSetup()
+	w := httptest.NewRecorder()
+
+	token := testutils.ConnectDemoUser(router)
+	req, _ := http.NewRequest("POST", "/ws/collection/"+collectionId+"/changeposition",
+		strings.NewReader(payload))
+	req.Header.Add("Authorization", fmt.Sprintf("Bearer %s", token))
+	router.ServeHTTP(w, req)
+
+	return w.Code
+}
diff --git a/internal/dto/in.go b/internal/dto/in.go
index 10fc867..c2c320d 100644
--- a/internal/dto/in.go
+++ b/internal/dto/in.go
@@ -51,6 +51,11 @@ type CollectionBook struct {
 	BookID uint `json:"bookId" binding:"required"`
 }
 
+type CollectionItemPosition struct {
+	Position uint `json:"position" binding:"required,gte=1"`
+	ItemID   uint `json:"itemId" binding:"required"`
+}
+
 type FileInfoPost struct {
 	FileID   uint   `json:"fileId"`
 	FilePath string `json:"filepath"`
diff --git a/internal/dto/out.go b/internal/dto/out.go
index 42cc1fc..8769c7a 100644
--- a/internal/dto/out.go
+++ b/internal/dto/out.go
@@ -51,6 +51,7 @@ type CollectionGet struct {
 }
 
 type CollectionItemGet struct {
+	ID       uint        `json:"id"`
 	Position uint        `json:"position"`
 	Book     BookItemGet `json:"book"`
 }
diff --git a/internal/i18nresource/locale.en.toml b/internal/i18nresource/locale.en.toml
index 0132d7a..d27ef44 100644
--- a/internal/i18nresource/locale.en.toml
+++ b/internal/i18nresource/locale.en.toml
@@ -10,3 +10,4 @@ RegistrationDisabled = "Registration has been disabled on this instance."
 UserAlreadyExists = "An user with this name already exists."
 ErrorWhenCreatingUserFromStr = "Error when creating user from string %s"
 Unauthorized = "You are not allowed to access this document."
+ItemDoesNotBelongToCollection = "Item does not belong to the collection."
diff --git a/internal/i18nresource/locale.fr.toml b/internal/i18nresource/locale.fr.toml
index c2be96d..d23962d 100644
--- a/internal/i18nresource/locale.fr.toml
+++ b/internal/i18nresource/locale.fr.toml
@@ -10,3 +10,4 @@ RegistrationDisabled = "La création de nouveaux comptes a été désactivée su
 UserAlreadyExists = "Un utilisateur avec le même nom existe déjà."
 ErrorWhenCreatingUserFromStr = "Erreur lors de la création de l'utilisateur %s"
 Unauthorized = "Vous n'êtes pas autorisé à accéder à cette page."
+ItemDoesNotBelongToCollection = "Cet élément n'appartient pas à la liste."
diff --git a/internal/query/querycollections.go b/internal/query/querycollections.go
index 7d6a51d..a19a365 100644
--- a/internal/query/querycollections.go
+++ b/internal/query/querycollections.go
@@ -81,6 +81,7 @@ func fetchCollections(db *gorm.DB, userId uint) *gorm.DB {
 }
 
 type CollectionItemQueryResult struct {
+	ItemID              uint
 	Position            uint
 	ID                  uint
 	Title               string
@@ -113,7 +114,7 @@ func FetchCollectionBooksCount(db *gorm.DB, userId uint, collectionId uint) (int
 
 func fetchCollectionBooksQuery(db *gorm.DB, userId uint, collectionId uint) *gorm.DB {
 	query := db.Model(&model.CollectionItem{})
-	query = query.Select("collection_items.position, " + selectBookItem())
+	query = query.Select("collection_items.position, collection_items.ID as item_id, " + selectBookItem())
 	query = query.Joins("left join collections on (collection_items.collection_id = collections.id)")
 	query = query.Joins("left join books on (books.id = collection_items.book_id)")
 	query = joinAuthors(query)
diff --git a/internal/routes/collectionaddbookpost.go b/internal/routes/collectionaddbookpost.go
index a656b11..a2633d8 100644
--- a/internal/routes/collectionaddbookpost.go
+++ b/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")
 }
diff --git a/internal/routes/collectionchangepositionpost.go b/internal/routes/collectionchangepositionpost.go
new file mode 100644
index 0000000..030729f
--- /dev/null
+++ b/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")
+}
diff --git a/internal/setup/setup.go b/internal/setup/setup.go
index 3b78a4c..e20cebc 100644
--- a/internal/setup/setup.go
+++ b/internal/setup/setup.go
@@ -87,6 +87,9 @@ func Setup(config *config.Config) *gin.Engine {
 	ws.POST("/collection/:id/addbook", func(c *gin.Context) {
 		routes.PostCollectionBookHandler(appcontext.AppContext{C: c, Db: db, I18n: bundle, Config: config})
 	})
+	ws.POST("/collection/:id/changeposition", func(c *gin.Context) {
+		routes.PostCollectionChangePositionHandler(appcontext.AppContext{C: c, Db: db, I18n: bundle, Config: config})
+	})
 	ws.POST("/collection", func(c *gin.Context) {
 		routes.PostCollectionHandler(appcontext.AppContext{C: c, Db: db, I18n: bundle, Config: config})
 	})