Added new methods on TaskList.

README.md

@@ -39,6 +39,15 @@ go-todotxt requires Go1.1 or higher.
 		fmt.Printf("Task 3: %v\n", tasklist[2])
 		fmt.Printf("Task 4, has priority: %v\n\n", tasklist[3].HasPriority())
 		fmt.Print(tasklist)
+
+		// Filter list to get only completed tasks
+		completedList := testTasklist.Filter(func(t Task) bool {
+			if t.Completed {
+				return true
+			}
+			return false
+		})
+		fmt.Print(completedList)
 	}
 ```
 

task.go

@@ -103,10 +103,10 @@ func (task Task) String() string {
 }
 
 // NewTask creates a new empty Task with default values. (CreatedDate is set to Now())
-func NewTask() *Task {
+func NewTask() Task {
 	task := Task{}
 	task.CreatedDate = time.Now()
-	return &task
+	return task
 }
 
 // ParseTask parses the input text string into a Task struct.

todotxt.go

@@ -10,6 +10,7 @@ package todotxt
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -28,7 +29,13 @@ var (
 	IgnoreComments = true
 )
 
-// String returns a complete tasklist string in todo.txt format.
+// NewTaskList creates a new empty TaskList.
+func NewTaskList() TaskList {
+	tasklist := TaskList{}
+	return tasklist
+}
+
+// String returns a complete list of tasks in todo.txt format.
 func (tasklist TaskList) String() (text string) {
 	for _, task := range tasklist {
 		text += fmt.Sprintf("%s\n", task.String())
@@ -36,8 +43,8 @@ func (tasklist TaskList) String() (text string) {
 	return text
 }
 
-// AddTask appends a task to the current TaskList, and takes care to set the Task.Id correctly, modifying the Task by the given pointer!
+// AddTask appends a task to the current TaskList and takes care to set the Task.Id correctly, modifying the Task by the given pointer!
-func (tasklist *TaskList) AddTask(task *Task) (err error) {
+func (tasklist *TaskList) AddTask(task *Task) {
 	task.Id = 0
 	for _, t := range *tasklist {
 		if t.Id > task.Id {
@@ -47,7 +54,70 @@ func (tasklist *TaskList) AddTask(task *Task) (err error) {
 	task.Id += 1
 
 	*tasklist = append(*tasklist, *task)
-	return
+}
+
+// GetTask returns task by given task 'id' from the TaskList. Returns an error if task could not be found.
+func (tasklist *TaskList) GetTask(id int) (*Task, error) {
+	for _, t := range *tasklist {
+		if t.Id == id {
+			return &t, nil
+		}
+	}
+	return nil, errors.New("task not found")
+}
+
+// RemoveTaskById removes any task with given task 'id' from the TaskList.
+// Returns an error if no task was removed.
+func (tasklist *TaskList) RemoveTaskById(id int) error {
+	var newList TaskList
+
+	found := false
+	for _, t := range *tasklist {
+		if t.Id != id {
+			newList = append(newList, t)
+		} else {
+			found = true
+		}
+	}
+	if !found {
+		return errors.New("task not found")
+	}
+
+	*tasklist = newList
+	return nil
+}
+
+// RemoveTask removes any task from the TaskList with the same String representation as the given task.
+// Returns an error if no task was removed.
+func (tasklist *TaskList) RemoveTask(task Task) error {
+	var newList TaskList
+
+	found := false
+	for _, t := range *tasklist {
+		if t.String() != task.String() {
+			newList = append(newList, t)
+		} else {
+			found = true
+		}
+	}
+	if !found {
+		return errors.New("task not found")
+	}
+
+	*tasklist = newList
+	return nil
+}
+
+// Filter filters the current TaskList for the given predicate (a function that takes a task as input and returns a bool),
+// and returns a new TaskList. The original TaskList is not modified.
+func (tasklist *TaskList) Filter(predicate func(Task) bool) *TaskList {
+	var newList TaskList
+	for _, t := range *tasklist {
+		if predicate(t) {
+			newList = append(newList, t)
+		}
+	}
+	return &newList
 }
 
 // LoadFromFile loads a TaskList from *os.File.

todotxt_test.go

@@ -205,7 +205,13 @@ func TestTaskListWriteFilename(t *testing.T) {
 }
 
 func TestNewTaskList(t *testing.T) {
-	t.Fail()
+	testTasklist := NewTaskList()
+
+	testExpected = 0
+	testGot = len(testTasklist)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
 }
 
 func TestTaskListCount(t *testing.T) {
@@ -226,7 +232,8 @@ func TestTaskListAddTask(t *testing.T) {
 	}
 
 	// add new empty task
-	testTasklist.AddTask(NewTask())
+	task := NewTask()
+	testTasklist.AddTask(&task)
 
 	testExpected = 64
 	testGot = len(testTasklist)
@@ -299,21 +306,159 @@ func TestTaskListAddTask(t *testing.T) {
 	taskId++
 }
 
+func TestTaskListGetTask(t *testing.T) {
+	if err := testTasklist.LoadFromFilename(testInputTasklist); err != nil {
+		t.Fatal(err)
+	}
+
+	taskId := 3
+	task, err := testTasklist.GetTask(taskId)
+	if err != nil {
+		t.Error(err)
+	}
+	testExpected = "(B) 2013-12-01 Outline chapter 5 @Computer +Novel Level:5 private:false due:2014-02-17"
+	testGot = task.String()
+	if testGot != testExpected {
+		t.Errorf("Expected Task[%d] to be [%s], but got [%s]", taskId, testExpected, testGot)
+	}
+	testExpected = 3
+	testGot = testTasklist[taskId-1].Id
+	if testGot != testExpected {
+		t.Errorf("Expected Task[%d] to be [%d], but got [%d]", taskId, testExpected, testGot)
+	}
+	taskId++
+}
+
 func TestTaskListRemoveTaskById(t *testing.T) {
-	t.Fail()
+	if err := testTasklist.LoadFromFilename(testInputTasklist); err != nil {
+		t.Fatal(err)
+	}
+
+	taskId := 10
+	if err := testTasklist.RemoveTaskById(taskId); err != nil {
+		t.Error(err)
+	}
+	testExpected = 62
+	testGot = len(testTasklist)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+	task, err := testTasklist.GetTask(taskId)
+	if err == nil || task != nil {
+		t.Errorf("Expected no Task to be found anymore, but got %v", task)
+	}
+
+	taskId = 27
+	if err := testTasklist.RemoveTaskById(taskId); err != nil {
+		t.Error(err)
+	}
+	testExpected = 61
+	testGot = len(testTasklist)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+	task, err = testTasklist.GetTask(taskId)
+	if err == nil || task != nil {
+		t.Errorf("Expected no Task to be found anymore, but got %v", task)
+	}
+
+	taskId = 99
+	if err := testTasklist.RemoveTaskById(taskId); err == nil {
+		t.Errorf("Expected no Task to be found for removal")
+	}
 }
 
 func TestTaskListRemoveTask(t *testing.T) {
-	// removes by comparing Task.String() with each other
+	if err := testTasklist.LoadFromFilename(testInputTasklist); err != nil {
-	t.Fail()
+		t.Fatal(err)
+	}
+
+	taskId := 52 // Is "unique" in tasklist
+	task, err := testTasklist.GetTask(taskId)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if err := testTasklist.RemoveTask(*task); err != nil {
+		t.Error(err)
+	}
+	testExpected = 62
+	testGot = len(testTasklist)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+	task, err = testTasklist.GetTask(taskId)
+	if err == nil || task != nil {
+		t.Errorf("Expected no Task to be found anymore, but got %v", task)
+	}
+
+	taskId = 2 // Exists 3 times in tasklist
+	task, err = testTasklist.GetTask(taskId)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if err := testTasklist.RemoveTask(*task); err != nil {
+		t.Error(err)
+	}
+	testExpected = 59
+	testGot = len(testTasklist)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+	task, err = testTasklist.GetTask(taskId)
+	if err == nil || task != nil {
+		t.Errorf("Expected no Task to be found anymore, but got %v", task)
+	}
+
+	if err := testTasklist.RemoveTask(NewTask()); err == nil {
+		t.Errorf("Expected no Task to be found for removal")
+	}
 }
 
 func TestTaskListFilter(t *testing.T) {
-	t.Fail()
+	if err := testTasklist.LoadFromFilename(testInputTasklist); err != nil {
+		t.Fatal(err)
 	}
 
-func TestTaskListFilterNot(t *testing.T) {
+	// Filter list to get only completed tasks
-	t.Fail()
+	completedList := testTasklist.Filter(func(t Task) bool {
+		if t.Completed {
+			return true
+		}
+		return false
+	})
+	testExpected = 33
+	testGot = len(*completedList)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+
+	// Filter list to get only tasks with a due date
+	dueDateList := testTasklist.Filter(func(t Task) bool {
+		if t.HasDueDate() {
+			return true
+		}
+		return false
+	})
+	testExpected = 26
+	testGot = len(*dueDateList)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
+
+	// Filter list to get only tasks with "B" priority
+	prioBList := testTasklist.Filter(func(t Task) bool {
+		if t.HasPriority() && t.Priority == "B" {
+			return true
+		}
+		return false
+	})
+	testExpected = 17
+	testGot = len(*prioBList)
+	if testGot != testExpected {
+		t.Errorf("Expected TaskList to contain %d tasks, but got %d", testExpected, testGot)
+	}
 }
 
 func TestTaskListReadErrors(t *testing.T) {