package backup

import (
	"context"
	"io"
	"sync"
	"time"

	"github.com/restic/restic/internal/archiver"
	"github.com/restic/restic/internal/restic"
	"github.com/restic/restic/internal/ui/signals"
)

// A ProgressPrinter can print various progress messages.
// It must be safe to call its methods from concurrent goroutines.
type ProgressPrinter interface {
	Update(total, processed Counter, errors uint, currentFiles map[string]struct{}, start time.Time, secs uint64)
	Error(item string, err error) error
	ScannerError(item string, err error) error
	CompleteItem(messageType string, item string, previous, current *restic.Node, s archiver.ItemStats, d time.Duration)
	ReportTotal(item string, start time.Time, s archiver.ScanStats)
	Finish(snapshotID restic.ID, start time.Time, summary *Summary, dryRun bool)
	Reset()

	// ui.StdioWrapper
	Stdout() io.WriteCloser
	Stderr() io.WriteCloser

	P(msg string, args ...interface{})
	V(msg string, args ...interface{})
}

type Counter struct {
	Files, Dirs, Bytes uint64
}

type Summary struct {
	Files, Dirs struct {
		New       uint
		Changed   uint
		Unchanged uint
	}
	ProcessedBytes uint64
	archiver.ItemStats
}

// Progress reports progress for the `backup` command.
type Progress struct {
	mu sync.Mutex

	interval time.Duration
	start    time.Time

	scanStarted, scanFinished bool

	currentFiles     map[string]struct{}
	processed, total Counter
	errors           uint

	closed chan struct{}

	summary Summary
	printer ProgressPrinter
}

func NewProgress(printer ProgressPrinter, interval time.Duration) *Progress {
	return &Progress{
		interval: interval,
		start:    time.Now(),

		currentFiles: make(map[string]struct{}),
		closed:       make(chan struct{}),

		printer: printer,
	}
}

// Run regularly updates the status lines. It should be called in a separate
// goroutine.
func (p *Progress) Run(ctx context.Context) {
	defer close(p.closed)
	// Reset status when finished
	defer p.printer.Reset()

	var tick <-chan time.Time
	if p.interval != 0 {
		t := time.NewTicker(p.interval)
		defer t.Stop()
		tick = t.C
	}

	signalsCh := signals.GetProgressChannel()

	for {
		var now time.Time
		select {
		case <-ctx.Done():
			return
		case now = <-tick:
		case <-signalsCh:
			now = time.Now()
		}

		p.mu.Lock()
		if !p.scanStarted {
			p.mu.Unlock()
			continue
		}

		var secondsRemaining uint64
		if p.scanFinished {
			secs := float64(now.Sub(p.start) / time.Second)
			todo := float64(p.total.Bytes - p.processed.Bytes)
			secondsRemaining = uint64(secs / float64(p.processed.Bytes) * todo)
		}

		p.printer.Update(p.total, p.processed, p.errors, p.currentFiles, p.start, secondsRemaining)
		p.mu.Unlock()
	}
}

// Error is the error callback function for the archiver, it prints the error and returns nil.
func (p *Progress) Error(item string, err error) error {
	p.mu.Lock()
	p.errors++
	p.scanStarted = true
	p.mu.Unlock()

	return p.printer.Error(item, err)
}

// StartFile is called when a file is being processed by a worker.
func (p *Progress) StartFile(filename string) {
	p.mu.Lock()
	defer p.mu.Unlock()
	p.currentFiles[filename] = struct{}{}
}

func (p *Progress) addProcessed(c Counter) {
	p.processed.Files += c.Files
	p.processed.Dirs += c.Dirs
	p.processed.Bytes += c.Bytes
	p.scanStarted = true
}

// CompleteBlob is called for all saved blobs for files.
func (p *Progress) CompleteBlob(bytes uint64) {
	p.mu.Lock()
	p.addProcessed(Counter{Bytes: bytes})
	p.mu.Unlock()
}

// CompleteItem is the status callback function for the archiver when a
// file/dir has been saved successfully.
func (p *Progress) CompleteItem(item string, previous, current *restic.Node, s archiver.ItemStats, d time.Duration) {
	p.mu.Lock()
	p.summary.ItemStats.Add(s)

	// for the last item "/", current is nil
	if current != nil {
		p.summary.ProcessedBytes += current.Size
	}

	p.mu.Unlock()

	if current == nil {
		// error occurred, tell the status display to remove the line
		p.mu.Lock()
		delete(p.currentFiles, item)
		p.mu.Unlock()
		return
	}

	switch current.Type {
	case "dir":
		p.mu.Lock()
		p.addProcessed(Counter{Dirs: 1})
		p.mu.Unlock()

		switch {
		case previous == nil:
			p.printer.CompleteItem("dir new", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Dirs.New++
			p.mu.Unlock()

		case previous.Equals(*current):
			p.printer.CompleteItem("dir unchanged", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Dirs.Unchanged++
			p.mu.Unlock()

		default:
			p.printer.CompleteItem("dir modified", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Dirs.Changed++
			p.mu.Unlock()
		}

	case "file":
		p.mu.Lock()
		p.addProcessed(Counter{Files: 1})
		delete(p.currentFiles, item)
		p.mu.Unlock()

		switch {
		case previous == nil:
			p.printer.CompleteItem("file new", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Files.New++
			p.mu.Unlock()

		case previous.Equals(*current):
			p.printer.CompleteItem("file unchanged", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Files.Unchanged++
			p.mu.Unlock()

		default:
			p.printer.CompleteItem("file modified", item, previous, current, s, d)
			p.mu.Lock()
			p.summary.Files.Changed++
			p.mu.Unlock()
		}
	}
}

// ReportTotal sets the total stats up to now
func (p *Progress) ReportTotal(item string, s archiver.ScanStats) {
	p.mu.Lock()
	defer p.mu.Unlock()

	p.total = Counter{Files: uint64(s.Files), Dirs: uint64(s.Dirs), Bytes: s.Bytes}
	p.scanStarted = true

	if item == "" {
		p.printer.ReportTotal(item, p.start, s)
	}
}

// Finish prints the finishing messages.
func (p *Progress) Finish(snapshotID restic.ID, dryrun bool) {
	// wait for the status update goroutine to shut down
	<-p.closed
	p.printer.Finish(snapshotID, p.start, &p.summary, dryrun)
}
