refactor: move timer function to method

- introduce Timer struct to manage timer state
- update RunPomodoro to use Timer methods for starting, stopping, and pausing
- remove unused pomodoro channels

internal/pomodoro/pomodoro.go

@@ -6,11 +6,8 @@ import (
 	"time"
 )
 
-var pomodoroResetChannel = make(chan bool, 1)
-var pomodoroPauseChannel = make(chan bool, 1)
-var pomodoroResumeChannel = make(chan bool, 1)
-
 var mu sync.Mutex // to synchronize access to shared state
+var timer Timer
 
 // RunPomodoro iterates the Pomodoro work/break sessions.
 func RunPomodoro() {
@@ -22,26 +19,29 @@ func RunPomodoro() {
 	pomodoroConfig := shared.Message.PomodoroSettings
 
 	for session := 1; session <= pomodoroConfig.Sessions; session++ {
+		timer = timer.Init()
+
 		shared.Message.Session = session
+
 		shared.Message.Mode = "Work"
-		if !startTimer(pomodoroConfig.Work) {
+		if !timer.Start(pomodoroConfig.Work) {
 			break
 		}
-		if session == pomodoroConfig.Sessions {
-			shared.Message.Mode = "LongBreak"
-			if !startTimer(pomodoroConfig.LongBreak) {
-				break
-			}
-		} else {
-			shared.Message.Mode = "ShortBreak"
-			if !startTimer(pomodoroConfig.ShortBreak) {
-				break
-			}
-		}
-		shared.Message.Mode = "End"
-	}
 
-	time.Sleep(time.Second)
+		if session > pomodoroConfig.Sessions {
+			shared.Message.Mode = "ShortBreak"
+			if !timer.Start(pomodoroConfig.ShortBreak) {
+				break
+			}
+		} else { // last phase, prepare for finish
+			shared.Message.Mode = "LongBreak"
+			if !timer.Start(pomodoroConfig.LongBreak) {
+				break
+			}
+			shared.Message.Mode = "End"
+			time.Sleep(time.Second)
+		}
+	}
 
 	mu.Lock()
 	shared.Message.Ongoing = false
@@ -53,12 +53,8 @@ func RunPomodoro() {
 	shared.Message.TimeLeft = shared.Message.PomodoroSettings.Work
 }
 
-// Stops and resets the running Pomodoro
 func ResetPomodoro() {
-	shared.Message.Mode = "Idle"
-	shared.Message.Session = 0
-	shared.Message.TimeLeft = shared.Message.PomodoroSettings.Work
-	pomodoroResetChannel <- true
+	timer.Stop()
 }
 
 func PausePomodoro() {
@@ -66,14 +62,14 @@ func PausePomodoro() {
 	shared.Message.Paused = true
 	mu.Unlock()
 
-	pomodoroPauseChannel <- true
+	timer.Pause()
 }
 
 func ResumePomodoro() {
 	mu.Lock()
 	shared.Message.Paused = false
 	mu.Unlock()
-	pomodoroResumeChannel <- true
+	timer.Resume()
 }
 
 func IsPomodoroOngoing() bool {