fix: add circular dependency detection for tasks

backend/controllers/add_task.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 )
 
 var GlobalJobQueue *JobQueue
@@ -62,9 +63,27 @@ func AddTaskHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		// Validate dependencies
-		if err := utils.ValidateDependencies(depends, ""); err != nil {
-			http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
-			return
+		origin := os.Getenv("CONTAINER_ORIGIN")
+		existingTasks, err := tw.FetchTasksFromTaskwarrior(email, encryptionSecret, origin, uuid)
+		if err != nil {
+			if err := utils.ValidateDependencies(depends, ""); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
+		} else {
+			taskDeps := make([]utils.TaskDependency, len(existingTasks))
+			for i, task := range existingTasks {
+				taskDeps[i] = utils.TaskDependency{
+					UUID:    task.UUID,
+					Depends: task.Depends,
+					Status:  task.Status,
+				}
+			}
+
+			if err := utils.ValidateCircularDependencies(depends, "", taskDeps); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
 		}
 		var dueDateStr string
 		if dueDate != nil && *dueDate != "" {

backend/controllers/edit_task.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 )
 
 // EditTaskHandler godoc
@@ -62,9 +63,27 @@ func EditTaskHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		// Validate dependencies
-		if err := utils.ValidateDependencies(depends, uuid); err != nil {
-			http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
-			return
+		origin := os.Getenv("CONTAINER_ORIGIN")
+		existingTasks, err := tw.FetchTasksFromTaskwarrior(email, encryptionSecret, origin, uuid)
+		if err != nil {
+			if err := utils.ValidateDependencies(depends, uuid); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
+		} else {
+			taskDeps := make([]utils.TaskDependency, len(existingTasks))
+			for i, task := range existingTasks {
+				taskDeps[i] = utils.TaskDependency{
+					UUID:    task.UUID,
+					Depends: task.Depends,
+					Status:  task.Status,
+				}
+			}
+
+			if err := utils.ValidateCircularDependencies(depends, uuid, taskDeps); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
 		}
 
 		logStore := models.GetLogStore()

backend/controllers/modify_task.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 )
 
 // ModifyTaskHandler godoc
@@ -61,9 +62,27 @@ func ModifyTaskHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		// Validate dependencies
-		if err := utils.ValidateDependencies(depends, uuid); err != nil {
-			http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
-			return
+		origin := os.Getenv("CONTAINER_ORIGIN")
+		existingTasks, err := tw.FetchTasksFromTaskwarrior(email, encryptionSecret, origin, uuid)
+		if err != nil {
+			if err := utils.ValidateDependencies(depends, uuid); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
+		} else {
+			taskDeps := make([]utils.TaskDependency, len(existingTasks))
+			for i, task := range existingTasks {
+				taskDeps[i] = utils.TaskDependency{
+					UUID:    task.UUID,
+					Depends: task.Depends,
+					Status:  task.Status,
+				}
+			}
+
+			if err := utils.ValidateCircularDependencies(depends, uuid, taskDeps); err != nil {
+				http.Error(w, fmt.Sprintf("Invalid dependencies: %v", err), http.StatusBadRequest)
+				return
+			}
 		}
 
 		// if err := tw.ModifyTaskInTaskwarrior(uuid, description, project, priority, status, due, email, encryptionSecret, taskID); err != nil {

backend/utils/utils_test.go

@@ -85,16 +85,42 @@ func Test_ExecCommandForOutputInDir(t *testing.T) {
 	}
 }
 
-func Test_ValidateDependencies_ValidDependencies(t *testing.T) {
-	depends := []string{"task-uuid-1", "task-uuid-2"}
-	currentTaskUUID := "current-task-uuid"
-	err := ValidateDependencies(depends, currentTaskUUID)
-	assert.NoError(t, err)
-}
-
 func Test_ValidateDependencies_EmptyList(t *testing.T) {
 	depends := []string{}
 	currentTaskUUID := "current-task-uuid"
 	err := ValidateDependencies(depends, currentTaskUUID)
 	assert.NoError(t, err)
 }
+
+// Circular Dependency Detection Tests
+func Test_detectCycle_NoCycle(t *testing.T) { //A -> B -> C
+	graph := map[string][]string{
+		"A": {"B"},
+		"B": {"C"},
+		"C": {},
+	}
+
+	hasCycle := detectCycle(graph, "A")
+	assert.False(t, hasCycle, "Should not detect cycle in linear dependency")
+}
+
+func Test_detectCycle_SimpleCycle(t *testing.T) { // A -> B -> A
+	graph := map[string][]string{
+		"A": {"B"},
+		"B": {"A"},
+	}
+
+	hasCycle := detectCycle(graph, "A")
+	assert.True(t, hasCycle, "Should detect simple cycle A -> B -> A")
+}
+
+func Test_detectCycle_ComplexCycle(t *testing.T) { // A -> B -> C -> A
+	graph := map[string][]string{
+		"A": {"B"},
+		"B": {"C"},
+		"C": {"A"},
+	}
+
+	hasCycle := detectCycle(graph, "A")
+	assert.True(t, hasCycle, "Should detect complex cycle A -> B -> C -> A")
+}

backend/utils/validation.go

@@ -19,3 +19,67 @@ func ValidateDependencies(depends []string, currentTaskUUID string) error {
 
 	return nil
 }
+
+type TaskDependency struct {
+	UUID    string   `json:"uuid"`
+	Depends []string `json:"depends"`
+	Status  string   `json:"status"`
+}
+
+func ValidateCircularDependencies(depends []string, currentTaskUUID string, existingTasks []TaskDependency) error {
+	if len(depends) == 0 {
+		return nil
+	}
+
+	dependencyGraph := make(map[string][]string)
+	for _, task := range existingTasks {
+		if task.Status == "pending" {
+			dependencyGraph[task.UUID] = task.Depends
+		}
+	}
+
+	dependencyGraph[currentTaskUUID] = depends
+
+	if hasCycle := detectCycle(dependencyGraph, currentTaskUUID); hasCycle {
+		return fmt.Errorf("circular dependency detected: adding these dependencies would create a cycle")
+	}
+
+	return nil
+}
+
+// (0): unvisited,  (1): visiting,(2): visited
+func detectCycle(graph map[string][]string, startNode string) bool {
+	color := make(map[string]int)
+
+	for node := range graph {
+		color[node] = 0
+	}
+
+	for _, deps := range graph {
+		for _, dep := range deps {
+			if _, exists := color[dep]; !exists {
+				color[dep] = 0
+			}
+		}
+	}
+
+	return dfsHasCycle(graph, startNode, color)
+}
+
+func dfsHasCycle(graph map[string][]string, node string, color map[string]int) bool {
+	color[node] = 1
+
+	for _, dep := range graph[node] {
+		if color[dep] == 1 {
+			return true
+		}
+		if color[dep] == 0 {
+			if dfsHasCycle(graph, dep, color) {
+				return true
+			}
+		}
+	}
+
+	color[node] = 2
+	return false
+}