package pb

import (
	"fmt"
	"io"
	"math"
	"strings"
	"sync"
	"sync/atomic"
	"time"
)

const (
	// Default refresh rate - 200ms
	DEFAULT_REFRESH_RATE = time.Millisecond * 200
	FORMAT               = "[=>-]"
)

// DEPRECATED
// variables for backward compatibility, from now do not work
// use pb.Format and pb.SetRefreshRate
var (
	DefaultRefreshRate                         = DEFAULT_REFRESH_RATE
	BarStart, BarEnd, Empty, Current, CurrentN string
)

// Create new progress bar object
func New(total int) *ProgressBar {
	return New64(int64(total))
}

// Create new progress bar object uding int64 as total
func New64(total int64) *ProgressBar {
	pb := &ProgressBar{
		Total:         total,
		RefreshRate:   DEFAULT_REFRESH_RATE,
		ShowPercent:   true,
		ShowCounters:  true,
		ShowBar:       true,
		ShowTimeLeft:  true,
		ShowFinalTime: true,
		Units:         U_NO,
		ManualUpdate:  false,
		isFinish:      make(chan struct{}),
		currentValue:  -1,
	}
	return pb.Format(FORMAT)
}

// Create new object and start
func StartNew(total int) *ProgressBar {
	return New(total).Start()
}

// Callback for custom output
// For example:
// bar.Callback = func(s string) {
//     mySuperPrint(s)
// }
//
type Callback func(out string)

type ProgressBar struct {
	current int64 // current must be first member of struct (https://code.google.com/p/go/issues/detail?id=5278)

	Total                            int64
	RefreshRate                      time.Duration
	ShowPercent, ShowCounters        bool
	ShowSpeed, ShowTimeLeft, ShowBar bool
	ShowFinalTime                    bool
	Output                           io.Writer
	Callback                         Callback
	NotPrint                         bool
	Units                            Units
	Width                            int
	ForceWidth                       bool
	ManualUpdate                     bool

	finishOnce sync.Once //Guards isFinish
	isFinish   chan struct{}

	startTime    time.Time
	startValue   int64
	currentValue int64

	prefix, postfix string

	BarStart string
	BarEnd   string
	Empty    string
	Current  string
	CurrentN string
}

// Start print
func (pb *ProgressBar) Start() *ProgressBar {
	pb.startTime = time.Now()
	pb.startValue = pb.current
	if pb.Total == 0 {
		pb.ShowBar = false
		pb.ShowTimeLeft = false
		pb.ShowPercent = false
	}	
	if !pb.ManualUpdate {
		go pb.writer()
	}
	return pb
}

// Increment current value
func (pb *ProgressBar) Increment() int {
	return pb.Add(1)
}

// Set current value
func (pb *ProgressBar) Set(current int) *ProgressBar {
	return pb.Set64(int64(current))
}

// Set64 sets the current value as int64
func (pb *ProgressBar) Set64(current int64) *ProgressBar {
	atomic.StoreInt64(&pb.current, current)
	return pb
}

// Add to current value
func (pb *ProgressBar) Add(add int) int {
	return int(pb.Add64(int64(add)))
}

func (pb *ProgressBar) Add64(add int64) int64 {
	return atomic.AddInt64(&pb.current, add)
}

// Set prefix string
func (pb *ProgressBar) Prefix(prefix string) *ProgressBar {
	pb.prefix = prefix
	return pb
}

// Set postfix string
func (pb *ProgressBar) Postfix(postfix string) *ProgressBar {
	pb.postfix = postfix
	return pb
}

// Set custom format for bar
// Example: bar.Format("[=>_]")
func (pb *ProgressBar) Format(format string) *ProgressBar {
	formatEntries := strings.Split(format, "")
	if len(formatEntries) == 5 {
		pb.BarStart = formatEntries[0]
		pb.BarEnd = formatEntries[4]
		pb.Empty = formatEntries[3]
		pb.Current = formatEntries[1]
		pb.CurrentN = formatEntries[2]
	}
	return pb
}

// Set bar refresh rate
func (pb *ProgressBar) SetRefreshRate(rate time.Duration) *ProgressBar {
	pb.RefreshRate = rate
	return pb
}

// Set units
// bar.SetUnits(U_NO) - by default
// bar.SetUnits(U_BYTES) - for Mb, Kb, etc
func (pb *ProgressBar) SetUnits(units Units) *ProgressBar {
	pb.Units = units
	return pb
}

// Set max width, if width is bigger than terminal width, will be ignored
func (pb *ProgressBar) SetMaxWidth(width int) *ProgressBar {
	pb.Width = width
	pb.ForceWidth = false
	return pb
}

// Set bar width
func (pb *ProgressBar) SetWidth(width int) *ProgressBar {
	pb.Width = width
	pb.ForceWidth = true
	return pb
}

// End print
func (pb *ProgressBar) Finish() {
	//Protect multiple calls
	pb.finishOnce.Do(func() {
		close(pb.isFinish)
		pb.write(atomic.LoadInt64(&pb.current))
		if !pb.NotPrint {
			fmt.Println()
		}
	})
}

// End print and write string 'str'
func (pb *ProgressBar) FinishPrint(str string) {
	pb.Finish()
	fmt.Println(str)
}

// implement io.Writer
func (pb *ProgressBar) Write(p []byte) (n int, err error) {
	n = len(p)
	pb.Add(n)
	return
}

// implement io.Reader
func (pb *ProgressBar) Read(p []byte) (n int, err error) {
	n = len(p)
	pb.Add(n)
	return
}

// Create new proxy reader over bar
func (pb *ProgressBar) NewProxyReader(r io.Reader) *Reader {
	return &Reader{r, pb}
}

func (pb *ProgressBar) write(current int64) {
	width := pb.getWidth()

	var percentBox, countersBox, timeLeftBox, speedBox, barBox, end, out string

	// percents
	if pb.ShowPercent {
		percent := float64(current) / (float64(pb.Total) / float64(100))
		percentBox = fmt.Sprintf(" %#.02f %% ", percent)
	}
	
	// counters
	if pb.ShowCounters {
		if pb.Total > 0 {
			countersBox = fmt.Sprintf("%s / %s ", Format(current, pb.Units), Format(pb.Total, pb.Units))
		} else {
			countersBox = Format(current, pb.Units) + " "
		}
	}

	// time left
	fromStart := time.Now().Sub(pb.startTime)
	currentFromStart := current - pb.startValue
	select {
	case <-pb.isFinish:
		if pb.ShowFinalTime {
			left := (fromStart / time.Second) * time.Second
			timeLeftBox = left.String()
		}
	default:
		if pb.ShowTimeLeft && currentFromStart > 0 {
			perEntry := fromStart / time.Duration(currentFromStart)
			left := time.Duration(pb.Total-currentFromStart) * perEntry
			left = (left / time.Second) * time.Second
			timeLeftBox = left.String()
		}
	}

	// speed
	if pb.ShowSpeed && currentFromStart > 0 {
		fromStart := time.Now().Sub(pb.startTime)
		speed := float64(currentFromStart) / (float64(fromStart) / float64(time.Second))
		speedBox = Format(int64(speed), pb.Units) + "/s "
	}

	// bar
	if pb.ShowBar {
		size := width - len(countersBox+pb.BarStart+pb.BarEnd+percentBox+timeLeftBox+speedBox+pb.prefix+pb.postfix)
		if size > 0 {
			curCount := int(math.Ceil((float64(current) / float64(pb.Total)) * float64(size)))
			emptCount := size - curCount
			barBox = pb.BarStart
			if emptCount < 0 {
				emptCount = 0
			}
			if curCount > size {
				curCount = size
			}
			if emptCount <= 0 {
				barBox += strings.Repeat(pb.Current, curCount)
			} else if curCount > 0 {
				barBox += strings.Repeat(pb.Current, curCount-1) + pb.CurrentN
			}

			barBox += strings.Repeat(pb.Empty, emptCount) + pb.BarEnd
		}
	}

	// check len
	out = pb.prefix + countersBox + barBox + percentBox + speedBox + timeLeftBox + pb.postfix
	if len(out) < width {
		end = strings.Repeat(" ", width-len(out))
	}

	// and print!
	switch {
	case pb.Output != nil:
		fmt.Fprint(pb.Output, "\r"+out+end)
	case pb.Callback != nil:
		pb.Callback(out + end)
	case !pb.NotPrint:
		fmt.Print("\r" + out + end)
	}
}

func (pb *ProgressBar) getWidth() int {
	if pb.ForceWidth {
		return pb.Width
	}

	width := pb.Width
	termWidth, _ := terminalWidth()
	if width == 0 || termWidth <= width {
		width = termWidth
	}

	return width
}

// Write the current state of the progressbar
func (pb *ProgressBar) Update() {
	c := atomic.LoadInt64(&pb.current)
	if c != pb.currentValue {
		pb.write(c)
		pb.currentValue = c
	}
}

// Internal loop for writing progressbar
func (pb *ProgressBar) writer() {
	pb.Update()
	for {
		select {
		case <-pb.isFinish:
			return
		case <-time.After(pb.RefreshRate):
			pb.Update()
		}
	}
}

type window struct {
	Row    uint16
	Col    uint16
	Xpixel uint16
	Ypixel uint16
}
