package lib

import (
	"os"
	"path/filepath"
	"time"
)

type NoTimerActiveError struct{}

func (e *NoTimerActiveError) Error() string {
	return "No timer is currently active."
}

// StartTimer starts a new timer.
func StartTimer() (*Time, error) {
	// Stop active timer
	activeTimer, _ := GetTimer()
	if activeTimer != nil {
		timer, stopErr := StopTimer()
		if stopErr != nil {
			return timer, stopErr
		}
	}

	// Start new timer
	newTimer := Time{
		Start: time.Now(),
	}

	setErr := setTimer(&newTimer)
	if setErr != nil {
		return nil, setErr
	}

	return &newTimer, nil
}

// UpdateTimer sets the project and activity on the current timer.
func UpdateTimer(project *Project, activity *Activity) (*Time, error) {
	timer, timerErr := GetTimer()
	if timerErr != nil {
		return timer, timerErr
	}
	if timer == nil {
		return nil, &NoTimerActiveError{}
	}

	timer.ProjectID = project.ID
	timer.ActivityID = activity.ID

	setError := setTimer(timer)
	if setError != nil {
		return timer, setError
	}

	return timer, nil
}

// StopTimer stops the current timer and records the resulting time entry.
func StopTimer() (*Time, error) {
	timer, timerErr := GetTimer()
	if timerErr != nil {
		return timer, timerErr
	}
	if timer == nil {
		return nil, &NoTimerActiveError{}
	}

	timer.End = time.Now()
	recordErr := SetTime(timer)
	if recordErr != nil {
		return timer, recordErr
	}

	file, fileErr := getTimerFile()
	if fileErr != nil {
		return timer, fileErr
	}

	removeErr := os.Remove(file)
	if removeErr != nil {
		return timer, removeErr
	}

	return nil, nil
}

// GetTimer returns the active timer.
func GetTimer() (*Time, error) {
	file, fileErr := getTimerFile()
	if fileErr != nil {
		return nil, fileErr
	}

	return readTime(file)
}

// setTimer persists a time entry as current timer. If there is already a current timer, it will be overwritten.
func setTimer(entry *Time) error {
	file, fileErr := getTimerFile()
	if fileErr != nil {
		return fileErr
	}

	return writeTime(entry, file)
}

// getTimerFile returns the file name for the timer.
func getTimerFile() (string, error) {
	folder, err := getDataDir("time")
	if err != nil {
		return "", err
	}

	return filepath.Join(folder, "timer.json"), nil
}