2 files changed, 115 insertions, 7 deletions
diff --git a/internal/handlers/handlers.go b/internal/handlers/handlers.go
index 0af2bba..f53eced 100644
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -350,9 +350,10 @@ func (h *Handler) aggregateData(ctx context.Context, forceRefresh bool) (*models
 	return data, nil
 }
 
-// fetchTasks fetches tasks from cache or API
+// fetchTasks fetches tasks from cache or API using incremental sync
 func (h *Handler) fetchTasks(ctx context.Context, forceRefresh bool) ([]models.Task, error) {
 	cacheKey := store.CacheKeyTodoistTasks
+	syncService := "todoist"
 
 	// Check cache validity
 	if !forceRefresh {
@@ -362,8 +363,20 @@ func (h *Handler) fetchTasks(ctx context.Context, forceRefresh bool) ([]models.T
 		}
 	}
 
-	// Fetch from API
-	tasks, err := h.todoistClient.GetTasks(ctx)
+	// Get stored sync token (empty string means full sync)
+	syncToken, err := h.store.GetSyncToken(syncService)
+	if err != nil {
+		log.Printf("Failed to get sync token, will do full sync: %v", err)
+		syncToken = ""
+	}
+
+	// Force full sync if requested
+	if forceRefresh {
+		syncToken = ""
+	}
+
+	// Fetch using Sync API
+	syncResp, err := h.todoistClient.Sync(ctx, syncToken)
 	if err != nil {
 		// Try to return cached data even if stale
 		cachedTasks, cacheErr := h.store.GetTasks()
@@ -373,9 +386,41 @@ func (h *Handler) fetchTasks(ctx context.Context, forceRefresh bool) ([]models.T
 		return nil, err
 	}
 
-	// Save to cache
-	if err := h.store.SaveTasks(tasks); err != nil {
-		log.Printf("Failed to save tasks to cache: %v", err)
+	// Build project map from sync response
+	projectMap := api.BuildProjectMapFromSync(syncResp.Projects)
+
+	// Process sync response
+	if syncResp.FullSync {
+		// Full sync: replace all tasks
+		tasks := api.ConvertSyncItemsToTasks(syncResp.Items, projectMap)
+		if err := h.store.SaveTasks(tasks); err != nil {
+			log.Printf("Failed to save tasks to cache: %v", err)
+		}
+	} else {
+		// Incremental sync: merge changes
+		var deletedIDs []string
+		for _, item := range syncResp.Items {
+			if item.IsDeleted || item.IsCompleted {
+				deletedIDs = append(deletedIDs, item.ID)
+			} else {
+				// Upsert active task
+				task := h.convertSyncItemToTask(item, projectMap)
+				if err := h.store.UpsertTask(task); err != nil {
+					log.Printf("Failed to upsert task %s: %v", item.ID, err)
+				}
+			}
+		}
+		// Delete removed tasks
+		if len(deletedIDs) > 0 {
+			if err := h.store.DeleteTasksByIDs(deletedIDs); err != nil {
+				log.Printf("Failed to delete tasks: %v", err)
+			}
+		}
+	}
+
+	// Store the new sync token
+	if err := h.store.SetSyncToken(syncService, syncResp.SyncToken); err != nil {
+		log.Printf("Failed to save sync token: %v", err)
 	}
 
 	// Update cache metadata
@@ -383,7 +428,43 @@ func (h *Handler) fetchTasks(ctx context.Context, forceRefresh bool) ([]models.T
 		log.Printf("Failed to update cache metadata: %v", err)
 	}
 
-	return tasks, nil
+	return h.store.GetTasks()
+}
+
+// convertSyncItemToTask converts a sync item to a Task model
+func (h *Handler) convertSyncItemToTask(item api.SyncItemResponse, projectMap map[string]string) models.Task {
+	task := models.Task{
+		ID:          item.ID,
+		Content:     item.Content,
+		Description: item.Description,
+		ProjectID:   item.ProjectID,
+		ProjectName: projectMap[item.ProjectID],
+		Priority:    item.Priority,
+		Completed:   false,
+		Labels:      item.Labels,
+		URL:         fmt.Sprintf("https://todoist.com/showTask?id=%s", item.ID),
+	}
+
+	if item.AddedAt != "" {
+		if createdAt, err := time.Parse(time.RFC3339, item.AddedAt); err == nil {
+			task.CreatedAt = createdAt
+		}
+	}
+
+	if item.Due != nil {
+		var dueDate time.Time
+		var err error
+		if item.Due.Datetime != "" {
+			dueDate, err = time.Parse(time.RFC3339, item.Due.Datetime)
+		} else if item.Due.Date != "" {
+			dueDate, err = time.Parse("2006-01-02", item.Due.Date)
+		}
+		if err == nil {
+			task.DueDate = &dueDate
+		}
+	}
+
+	return task
 }
 
 // fetchNotes fetches notes from cache or filesystem
diff --git a/internal/handlers/handlers_test.go b/internal/handlers/handlers_test.go
index 3ea2a3e..1aa72cc 100644
--- a/internal/handlers/handlers_test.go
+++ b/internal/handlers/handlers_test.go
@@ -9,6 +9,7 @@ import (
 	"testing"
 	"time"
 
+	"task-dashboard/internal/api"
 	"task-dashboard/internal/config"
 	"task-dashboard/internal/models"
 	"task-dashboard/internal/store"
@@ -82,6 +83,32 @@ func (m *mockTodoistClient) CompleteTask(ctx context.Context, taskID string) err
 	return nil
 }
 
+func (m *mockTodoistClient) Sync(ctx context.Context, syncToken string) (*api.TodoistSyncResponse, error) {
+	if m.err != nil {
+		return nil, m.err
+	}
+	// Return a mock sync response with tasks converted to sync items
+	items := make([]api.SyncItemResponse, 0, len(m.tasks))
+	for _, task := range m.tasks {
+		items = append(items, api.SyncItemResponse{
+			ID:          task.ID,
+			Content:     task.Content,
+			Description: task.Description,
+			ProjectID:   task.ProjectID,
+			Priority:    task.Priority,
+			Labels:      task.Labels,
+			IsCompleted: task.Completed,
+			IsDeleted:   false,
+		})
+	}
+	return &api.TodoistSyncResponse{
+		SyncToken: "test-sync-token",
+		FullSync:  true,
+		Items:     items,
+		Projects:  []api.SyncProjectResponse{},
+	}, nil
+}
+
 // mockTrelloClient creates a mock Trello client for testing
 type mockTrelloClient struct {
 	boards []models.Board