/*
  Pominal
  Copyright (C) 2019  Daniel Anglin

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package main

import (
	"flag"
	"fmt"
	"math"
	"os"
	"os/exec"
	"os/signal"
	"syscall"
	"time"
)

const (
	workTimerLabel       string = "Work"
	shortBreakTimerLabel string = "Short break"
	longBreakTimerLabel  string = "Long break"
)

var (
	workTimer       string
	shortBreakTimer string
	longBreakTimer  string
	maxWorkCycles   int
	printVersion    bool
)

func init() {
	flag.StringVar(&workTimer, "work-timer", "25m", "sets the timer for your work session.")
	flag.StringVar(&shortBreakTimer, "short-break-timer", "5m", "sets the timer for your short break.")
	flag.StringVar(&longBreakTimer, "long-break-timer", "20m", "sets the timer for your long break.")
	flag.IntVar(&maxWorkCycles, "max-work-cycles", 4, "sets the maximum number of work cycles to complete before taking a long break.")
	flag.BoolVar(&printVersion, "version", false, "print version and exit.")
	flag.Parse()
}

type Pominal struct {
	timer         *time.Timer
	finish        time.Time
	work          time.Duration
	shortBreak    time.Duration
	longBreak     time.Duration
	maxWorkCycles int
	session       int
	label         string
}

func main() {

	if printVersion {
		Version()
		os.Exit(0)
	}

	workTimeDuration, err := time.ParseDuration(workTimer)
	if err != nil {
		fmt.Printf("ERROR: Unable to set the work timer. %s", err.Error())
		os.Exit(1)
	}

	shortBreakTimeDuration, err := time.ParseDuration(shortBreakTimer)
	if err != nil {
		fmt.Printf("ERROR: Unable to set the work timer. %s", err.Error())
		os.Exit(1)
	}

	longBreakTimeDuration, err := time.ParseDuration(longBreakTimer)
	if err != nil {
		fmt.Printf("ERROR: Unable to set the work timer. %s", err.Error())
		os.Exit(1)
	}

	pominal := NewPominal(workTimeDuration, shortBreakTimeDuration, longBreakTimeDuration, maxWorkCycles)

	pominal.Run()
}

// NewPominal creates a new pominal instance
func NewPominal(w, s, l time.Duration, m int) Pominal {

	return Pominal{
		work:          w,
		shortBreak:    s,
		longBreak:     l,
		maxWorkCycles: m,
		session:       1,
	}
}

// Run Pominal
func (p *Pominal) Run() {
	workCycleCount := 1
	t := time.NewTicker(1 * time.Second)
	s := make(chan os.Signal, 1)

	signal.Notify(s, syscall.SIGINT, syscall.SIGTERM)
	p.Start(workTimerLabel, workCycleCount)

infinite:
	for {
		select {
		case sig := <-s:
			fmt.Printf("\n\nReceived signal '%s'. Closing Pominal.\n", sig)
			p.timer.Stop()
			t.Stop()
			break infinite
		case <-t.C:
			printScreen(p.TimeRemaining(), p.session, workCycleCount, p.maxWorkCycles, p.label)
		case <-p.timer.C:
			fmt.Printf("\n%s timer has finished\n", p.label)
			p.timer.Stop()
			t.Stop()
			time.Sleep(2 * time.Second)
			switch p.label {
			case workTimerLabel:
				if workCycleCount >= p.maxWorkCycles {
					p.Start(longBreakTimerLabel, workCycleCount)
				} else {
					p.Start(shortBreakTimerLabel, workCycleCount)
				}
			case shortBreakTimerLabel:
				workCycleCount++
				p.Start(workTimerLabel, workCycleCount)
			case longBreakTimerLabel:
				workCycleCount = 1
				p.IncrementCount()
				p.Start(workTimerLabel, workCycleCount)
			}
			t = time.NewTicker(1 * time.Second)
		}
	}
}

// Start begins the timer specified by the
// label argument.
func (p *Pominal) Start(label string, workCycleCount int) {
	var d time.Duration

	switch label {
	case workTimerLabel:
		d = p.work
	case shortBreakTimerLabel:
		d = p.shortBreak
	case longBreakTimerLabel:
		d = p.longBreak
	}

	p.label = label
	if p.timer == nil {
		p.timer = time.NewTimer(d)
	} else {
		p.timer.Reset(d)
	}

	p.finish = time.Now().Add(d)
}

// IncrementCount increments the pominal session count
func (p *Pominal) IncrementCount() {
	p.session++
}

// TimeRemaining returns the remaining time left
// on the timer
func (p *Pominal) TimeRemaining() float64 {
	return p.finish.Sub(time.Now()).Seconds()
}

// printScreen prints the details of the Pominal session on screen including
// the current work cycle number, the timer's current label and the time remaining
// on the timer.
func printScreen(remaining float64, pominalCount, workCycle, maxWorkCycle int, label string) {
	clearScreen()
	remainingSecs := int(math.Ceil(remaining))
	fmt.Printf("Pominal session: %d\nWork cycle: %d of %d\n\n", pominalCount, workCycle, maxWorkCycle)
	fmt.Printf("Timer: %s\nTime remaining: %02d:%02d", label, (remainingSecs/60)%60, remainingSecs%60)
}

// clearScreen clears the terminal screen
func clearScreen() {
	cmd := exec.Command("clear")
	cmd.Stdout = os.Stdout
	cmd.Run()
}