feat(migration/wekan): import attachments from board export

Parse the top-level `attachments` array in WeKan board JSON exports,
group them by card ID, base64-decode the payload, and attach the
resulting files to the generated tasks so they land in Vikunja as
task attachments. Orphaned attachments (cardId with no matching card)
are silently skipped; decode errors are logged and skipped.

pkg/modules/migration/wekan/testdata_wekan_export.json

@@ -63,5 +63,14 @@
   "rules": [],
   "triggers": [],
   "actions": [],
-  "customFields": []
+  "customFields": [],
+  "attachments": [
+    {
+      "_id": "att-1",
+      "cardId": "card-1",
+      "file": "aGVsbG8gd2VrYW4=",
+      "name": "note.txt",
+      "type": "text/plain"
+    }
+  ]
 }

pkg/modules/migration/wekan/wekan.go

@@ -18,11 +18,13 @@ package wekan
 
 import (
 	"bytes"
+	"encoding/base64"
 	"encoding/json"
 	"io"
 	"sort"
 	"time"
 
+	"code.vikunja.io/api/pkg/files"
 	"code.vikunja.io/api/pkg/log"
 	"code.vikunja.io/api/pkg/models"
 	"code.vikunja.io/api/pkg/modules/migration"
@@ -42,6 +44,7 @@ type wekanBoard struct {
 	Checklists     []wekanChecklist     `json:"checklists"`
 	ChecklistItems []wekanChecklistItem `json:"checklistItems"`
 	Comments       []wekanComment       `json:"comments"`
+	Attachments    []wekanAttachment    `json:"attachments"`
 }
 
 type wekanLabel struct {
@@ -96,6 +99,14 @@ type wekanComment struct {
 	CardID    string     `json:"cardId"`
 }
 
+type wekanAttachment struct {
+	ID     string `json:"_id"`
+	CardID string `json:"cardId"`
+	File   string `json:"file"` // base64-encoded file contents
+	Name   string `json:"name"`
+	Type   string `json:"type"` // MIME type
+}
+
 // wekanColorMap maps WeKan label color names to hex values.
 // Values sourced from WeKan's client/components/cards/labels.css.
 var wekanColorMap = map[string]string{
@@ -174,6 +185,12 @@ func convertWekanToVikunja(board *wekanBoard) []*models.ProjectWithTasksAndBucke
 		commentsByCardID[c.CardID] = append(commentsByCardID[c.CardID], c)
 	}
 
+	// Build attachments grouped by card ID
+	attachmentsByCardID := make(map[string][]wekanAttachment)
+	for _, a := range board.Attachments {
+		attachmentsByCardID[a.CardID] = append(attachmentsByCardID[a.CardID], a)
+	}
+
 	// Create buckets from lists, maintaining sort order
 	sortedLists := make([]wekanList, len(board.Lists))
 	copy(sortedLists, board.Lists)
@@ -283,6 +300,25 @@ func convertWekanToVikunja(board *wekanBoard) []*models.ProjectWithTasksAndBucke
 			}
 		}
 
+		// Attachments
+		if attachments, ok := attachmentsByCardID[card.ID]; ok {
+			for _, a := range attachments {
+				decoded, err := base64.StdEncoding.DecodeString(a.File)
+				if err != nil {
+					log.Errorf("[WeKan migration] Error decoding attachment %s on card %s: %s", a.ID, card.ID, err.Error())
+					continue
+				}
+				task.Attachments = append(task.Attachments, &models.TaskAttachment{
+					File: &files.File{
+						Name:        a.Name,
+						Mime:        a.Type,
+						Size:        uint64(len(decoded)),
+						FileContent: decoded,
+					},
+				})
+			}
+		}
+
 		tasks = append(tasks, task)
 	}
 
@@ -330,7 +366,7 @@ func (m *Migrator) Name() string {
 
 // Migrate takes a WeKan board JSON export and imports it into Vikunja.
 // @Summary Import all projects, tasks etc. from a WeKan board export
-// @Description Imports all projects, tasks, labels, checklists, and comments from a WeKan board JSON export into Vikunja.
+// @Description Imports all projects, tasks, labels, checklists, comments, and attachments from a WeKan board JSON export into Vikunja.
 // @tags migration
 // @Accept x-www-form-urlencoded
 // @Produce json

pkg/modules/migration/wekan/wekan_test.go

@@ -141,6 +141,57 @@ func TestConvertWekanToVikunja(t *testing.T) {
 	assert.Equal(t, int64(1), task3.BucketID) // To Do
 }
 
+func TestParseWekanJSON_ParsesAttachments(t *testing.T) {
+	raw := []byte(`{
+		"_id": "b1",
+		"title": "B",
+		"lists": [],
+		"cards": [],
+		"attachments": [
+			{"_id": "a1", "cardId": "c1", "file": "aGVsbG8=", "name": "hi.txt", "type": "text/plain"}
+		]
+	}`)
+
+	board, err := parseWekanJSON(bytes.NewReader(raw))
+	require.NoError(t, err)
+	require.Len(t, board.Attachments, 1)
+	assert.Equal(t, "a1", board.Attachments[0].ID)
+	assert.Equal(t, "c1", board.Attachments[0].CardID)
+	assert.Equal(t, "aGVsbG8=", board.Attachments[0].File)
+	assert.Equal(t, "hi.txt", board.Attachments[0].Name)
+	assert.Equal(t, "text/plain", board.Attachments[0].Type)
+}
+
+func TestConvertWekanToVikunja_Attachments(t *testing.T) {
+	// "hello" in base64 is "aGVsbG8="
+	board := &wekanBoard{
+		ID:    "b1",
+		Title: "B",
+		Lists: []wekanList{{ID: "l1", Title: "L", Sort: 0}},
+		Cards: []wekanCard{{ID: "c1", Title: "Card", ListID: "l1"}},
+		Attachments: []wekanAttachment{
+			{ID: "a1", CardID: "c1", File: "aGVsbG8=", Name: "hi.txt", Type: "text/plain"},
+			{ID: "a2", CardID: "c1", File: "d29ybGQ=", Name: "w.txt", Type: "text/plain"},
+			{ID: "a3", CardID: "missing", File: "aGVsbG8=", Name: "orphan.txt", Type: "text/plain"},
+		},
+	}
+
+	projects := convertWekanToVikunja(board)
+	require.Len(t, projects, 1)
+	require.Len(t, projects[0].Tasks, 1)
+
+	task := projects[0].Tasks[0]
+	require.Len(t, task.Attachments, 2)
+
+	assert.Equal(t, "hi.txt", task.Attachments[0].File.Name)
+	assert.Equal(t, "text/plain", task.Attachments[0].File.Mime)
+	assert.Equal(t, []byte("hello"), task.Attachments[0].File.FileContent)
+	assert.Equal(t, uint64(5), task.Attachments[0].File.Size)
+
+	assert.Equal(t, "w.txt", task.Attachments[1].File.Name)
+	assert.Equal(t, []byte("world"), task.Attachments[1].File.FileContent)
+}
+
 func TestMigrateValidJSON(t *testing.T) {
 	validJSON := `{
 		"_id": "board1",
@@ -315,6 +366,12 @@ func TestConvertWekanFromFixtureFile(t *testing.T) {
 	require.Len(t, task1.Comments, 1)
 	assert.False(t, task1.Done)
 
+	// Attachment on card 1
+	require.Len(t, task1.Attachments, 1)
+	assert.Equal(t, "note.txt", task1.Attachments[0].File.Name)
+	assert.Equal(t, "text/plain", task1.Attachments[0].File.Mime)
+	assert.Equal(t, []byte("hello wekan"), task1.Attachments[0].File.FileContent)
+
 	// Card 3 - archived
 	task3 := project.Tasks[2]
 	assert.Equal(t, "Update README", task3.Title)