Added the DiffTasks function definition in the diff_types file

Signed-off-by: Lorygold <lory.goldoni@gmail.com>

Author: Lorygold

internal/diff_types.go

@@ -1,5 +1,10 @@
 package internal
 
+import (
+	"fmt"
+	"reflect"
+)
+
 // DiffStatus describes how a task changed between two checkpoints
 type DiffStatus string
 
@@ -42,3 +47,88 @@ type DiffChange struct {
 	// Value in checkpoint B
 	After any `json:"after,omitempty"`
 }
+
+// DiffTasks compares two sets of tasks and returns their differences.
+func DiffTasks(
+	tasksA []*Task,
+	tasksB []*Task,
+	psTreeCmd bool,
+	psTreeEnv bool,
+	files bool,
+	sockets bool,
+) ([]DiffTask, error) {
+
+	if tasksA == nil || tasksB == nil {
+		return nil, fmt.Errorf("nil task list provided")
+	}
+
+	// Index tasks by CheckpointFilePath for matching
+	indexA := make(map[string]*Task)
+	indexB := make(map[string]*Task)
+
+	for _, t := range tasksA {
+		indexA[t.CheckpointFilePath] = t
+	}
+	for _, t := range tasksB {
+		indexB[t.CheckpointFilePath] = t
+	}
+
+	var diffs []DiffTask
+
+	// Tasks present in A
+	for id, taskA := range indexA {
+		taskB, exists := indexB[id]
+
+		if !exists {
+			// Removed task
+			diffs = append(diffs, DiffTask{
+				ID:     id,
+				Status: Removed,
+				Before: taskA,
+			})
+			continue
+		}
+
+		// Exists in both → compare
+		if reflect.DeepEqual(taskA, taskB) {
+			diffs = append(diffs, DiffTask{
+				ID:     id,
+				Status: Unchanged,
+				Before: taskA,
+				After:  taskB,
+			})
+			continue
+		}
+
+		// Modified task
+		diffs = append(diffs, DiffTask{
+			ID:     id,
+			Status: Modified,
+			Before: taskA,
+			After:  taskB,
+			Changes: []DiffChange{
+				{
+					Category: "task",
+					Field:    "struct",
+					Before:   taskA,
+					After:    taskB,
+				},
+			},
+		})
+	}
+
+	// Tasks only in B → Added
+	for id, taskB := range indexB {
+		if _, exists := indexA[id]; exists {
+			continue
+		}
+
+		diffs = append(diffs, DiffTask{
+			ID:     id,
+			Status: Added,
+			After:  taskB,
+		})
+	}
+
+	return diffs, nil
+}