package snapshot

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"sync"
	"sync/atomic"
	"syscall"
	"time"

	"github.com/dustin/go-humanize"
	"sneak.berlin/go/vaultik/internal/log"
)

const (
	// SummaryInterval defines how often one-line status updates are printed.
	// These updates show current progress, ETA, and the file being processed.
	SummaryInterval = 10 * time.Second

	// DetailInterval defines how often multi-line detailed status reports are
	// printed. These reports include comprehensive statistics about files,
	// chunks, blobs, and uploads.
	DetailInterval = 60 * time.Second

	// UploadProgressInterval defines how often upload progress messages are logged.
	UploadProgressInterval = 15 * time.Second
)

const (
	// bitsPerByte converts byte counts to bit counts for speed display.
	bitsPerByte = 8

	// percentScale converts a ratio to a percentage.
	percentScale = 100

	// currentFileMaxLen is the display width used for current-file paths.
	currentFileMaxLen = 40

	// secondsPerMinute and minutesPerHour are used for duration formatting.
	secondsPerMinute = 60
	minutesPerHour   = 60

	// Bit-rate thresholds for human-readable upload speed formatting.
	bitsPerGbit = 1e9
	bitsPerMbit = 1e6
	bitsPerKbit = 1e3

	// ellipsis prefixes truncated paths and suffixes shortened hashes.
	ellipsis = "..."

	// hashPrefixLen is how many hex characters of a blob hash to show in logs.
	hashPrefixLen = 8
)

// ProgressStats holds atomic counters for progress tracking
type ProgressStats struct {
	FilesScanned     atomic.Int64 // Total files seen during scan (includes skipped)
	FilesProcessed   atomic.Int64 // Files actually processed in phase 2
	FilesSkipped     atomic.Int64 // Files skipped due to no changes
	BytesScanned     atomic.Int64 // Bytes from new/changed files only
	BytesSkipped     atomic.Int64 // Bytes from unchanged files
	BytesProcessed   atomic.Int64 // Actual bytes processed (for ETA calculation)
	ChunksCreated    atomic.Int64
	BlobsCreated     atomic.Int64
	BlobsUploaded    atomic.Int64
	BytesUploaded    atomic.Int64
	UploadDurationMs atomic.Int64 // Total milliseconds spent uploading
	CurrentFile      atomic.Value // stores string
	TotalSize        atomic.Int64 // Total size to process (set after scan phase)
	TotalFiles       atomic.Int64 // Total files to process in phase 2
	ProcessStartTime atomic.Value // stores time.Time when processing starts
	StartTime        time.Time
	mu               sync.RWMutex
	lastDetailTime   time.Time

	// Upload tracking
	CurrentUpload    atomic.Value // stores *UploadInfo
	lastChunkingTime time.Time    // Track when we last showed chunking progress
}

// UploadInfo tracks current upload progress
type UploadInfo struct {
	BlobHash    string
	Size        int64
	StartTime   time.Time
	LastLogTime time.Time
}

// ProgressReporter handles periodic progress reporting
type ProgressReporter struct {
	stats         *ProgressStats
	ctx           context.Context //nolint:containedctx // bound at construction
	cancel        context.CancelFunc
	wg            sync.WaitGroup
	detailTicker  *time.Ticker
	summaryTicker *time.Ticker
	sigChan       chan os.Signal
}

// NewProgressReporter creates a new progress reporter
func NewProgressReporter() *ProgressReporter {
	stats := &ProgressStats{
		StartTime:      time.Now().UTC(),
		lastDetailTime: time.Now().UTC(),
	}
	stats.CurrentFile.Store("")

	ctx, cancel := context.WithCancel(context.Background())

	pr := &ProgressReporter{
		stats:         stats,
		ctx:           ctx,
		cancel:        cancel,
		summaryTicker: time.NewTicker(SummaryInterval),
		detailTicker:  time.NewTicker(DetailInterval),
		sigChan:       make(chan os.Signal, 1),
	}

	// Register for SIGUSR1
	signal.Notify(pr.sigChan, syscall.SIGUSR1)

	return pr
}

// Start begins the progress reporting
func (pr *ProgressReporter) Start() {
	pr.wg.Add(1)
	go pr.run()

	// Print initial multi-line status
	pr.printDetailedStatus()
}

// Stop stops the progress reporting
func (pr *ProgressReporter) Stop() {
	pr.cancel()
	pr.summaryTicker.Stop()
	pr.detailTicker.Stop()
	signal.Stop(pr.sigChan)
	close(pr.sigChan)
	pr.wg.Wait()
}

// GetStats returns the progress stats for updating
func (pr *ProgressReporter) GetStats() *ProgressStats {
	return pr.stats
}

// SetTotalSize sets the total size to process (after scan phase)
func (pr *ProgressReporter) SetTotalSize(size int64) {
	pr.stats.TotalSize.Store(size)
	pr.stats.ProcessStartTime.Store(time.Now().UTC())
}

// Helper functions

func formatDuration(d time.Duration) string {
	if d < 0 {
		return "unknown"
	}

	if d < time.Minute {
		return fmt.Sprintf("%ds", int(d.Seconds()))
	}

	if d < time.Hour {
		return fmt.Sprintf("%dm%ds", int(d.Minutes()), int(d.Seconds())%secondsPerMinute)
	}

	return fmt.Sprintf("%dh%dm", int(d.Hours()), int(d.Minutes())%minutesPerHour)
}

func formatPercent(numerator, denominator int64) string {
	if denominator == 0 {
		return "0.0%"
	}

	return fmt.Sprintf("%.1f%%", float64(numerator)/float64(denominator)*percentScale)
}

func formatRatio(compressed, uncompressed int64) string {
	if uncompressed == 0 {
		return "1.00"
	}

	ratio := float64(compressed) / float64(uncompressed)

	return fmt.Sprintf("%.2f", ratio)
}

func truncatePath(path string, maxLen int) string {
	if len(path) <= maxLen {
		return path
	}
	// Keep the last maxLen-len(ellipsis) characters and prepend the ellipsis.
	return ellipsis + path[len(path)-(maxLen-len(ellipsis)):]
}

// safeUint64 converts a non-negative int64 counter to uint64 for display,
// clamping negative values to zero.
func safeUint64(n int64) uint64 {
	if n < 0 {
		return 0
	}

	return uint64(n)
}

// ReportUploadStart marks the beginning of a blob upload
func (pr *ProgressReporter) ReportUploadStart(blobHash string, size int64) {
	info := &UploadInfo{
		BlobHash:  blobHash,
		Size:      size,
		StartTime: time.Now().UTC(),
	}
	pr.stats.CurrentUpload.Store(info)

	// Log the start of upload
	log.Info("Starting blob upload",
		"hash", blobHash[:hashPrefixLen]+ellipsis,
		"size", humanize.Bytes(safeUint64(size)))
}

// ReportUploadComplete marks the completion of a blob upload
func (pr *ProgressReporter) ReportUploadComplete(
	blobHash string, size int64, duration time.Duration,
) {
	// Clear current upload
	pr.stats.CurrentUpload.Store((*UploadInfo)(nil))

	// Add to total upload duration
	pr.stats.UploadDurationMs.Add(duration.Milliseconds())

	// Calculate speed
	if duration < time.Millisecond {
		duration = time.Millisecond
	}

	bytesPerSec := float64(size) / duration.Seconds()
	bitsPerSec := bytesPerSec * bitsPerByte

	// Format speed
	var speedStr string

	switch {
	case bitsPerSec >= bitsPerGbit:
		speedStr = fmt.Sprintf("%.1fGbit/sec", bitsPerSec/bitsPerGbit)
	case bitsPerSec >= bitsPerMbit:
		speedStr = fmt.Sprintf("%.0fMbit/sec", bitsPerSec/bitsPerMbit)
	case bitsPerSec >= bitsPerKbit:
		speedStr = fmt.Sprintf("%.0fKbit/sec", bitsPerSec/bitsPerKbit)
	default:
		speedStr = fmt.Sprintf("%.0fbit/sec", bitsPerSec)
	}

	log.Info("Blob upload completed",
		"hash", blobHash[:hashPrefixLen]+ellipsis,
		"size", humanize.Bytes(safeUint64(size)),
		"duration", formatDuration(duration),
		"speed", speedStr)
}

// UpdateChunkingActivity updates the last chunking time
func (pr *ProgressReporter) UpdateChunkingActivity() {
	pr.stats.mu.Lock()
	pr.stats.lastChunkingTime = time.Now().UTC()
	pr.stats.mu.Unlock()
}

// ReportUploadProgress reports current upload progress with instantaneous speed
func (pr *ProgressReporter) ReportUploadProgress(
	blobHash string, bytesUploaded, totalSize int64, instantSpeed float64,
) {
	// Update the current upload info with progress
	uploadInfo, ok := pr.stats.CurrentUpload.Load().(*UploadInfo)
	if ok && uploadInfo != nil {
		now := time.Now()

		// Only log at the configured interval
		if now.Sub(uploadInfo.LastLogTime) >= UploadProgressInterval {
			// Format speed in bits/second using humanize
			bitsPerSec := instantSpeed * bitsPerByte
			speedStr := humanize.SI(bitsPerSec, "bit/sec")

			percent := float64(bytesUploaded) / float64(totalSize) * percentScale

			// Calculate ETA based on current speed
			etaStr := "unknown"

			if instantSpeed > 0 && bytesUploaded < totalSize {
				remainingBytes := totalSize - bytesUploaded
				remainingSeconds := float64(remainingBytes) / instantSpeed
				eta := time.Duration(remainingSeconds * float64(time.Second))
				etaStr = formatDuration(eta)
			}

			log.Info("Blob upload progress",
				"hash", blobHash[:hashPrefixLen]+ellipsis,
				"progress", fmt.Sprintf("%.1f%%", percent),
				"uploaded", humanize.Bytes(safeUint64(bytesUploaded)),
				"total", humanize.Bytes(safeUint64(totalSize)),
				"speed", speedStr,
				"eta", etaStr)

			uploadInfo.LastLogTime = now
		}
	}
}

// run is the main progress reporting loop
func (pr *ProgressReporter) run() {
	defer pr.wg.Done()

	for {
		select {
		case <-pr.ctx.Done():
			return
		case <-pr.summaryTicker.C:
			pr.printSummaryStatus()
		case <-pr.detailTicker.C:
			pr.printDetailedStatus()
		case <-pr.sigChan:
			// SIGUSR1 received, print detailed status
			log.Info("SIGUSR1 received, printing detailed status")
			pr.printDetailedStatus()
		}
	}
}

// printSummaryStatus prints a one-line status update
func (pr *ProgressReporter) printSummaryStatus() {
	// Check if we're currently uploading
	uploadInfo, ok := pr.stats.CurrentUpload.Load().(*UploadInfo)
	if ok && uploadInfo != nil {
		// Show upload progress instead
		pr.printUploadProgress(uploadInfo)

		return
	}

	// Only show chunking progress if we've done chunking recently
	pr.stats.mu.RLock()
	timeSinceLastChunk := time.Since(pr.stats.lastChunkingTime)
	pr.stats.mu.RUnlock()

	if timeSinceLastChunk > SummaryInterval*2 {
		// No recent chunking activity, don't show progress
		return
	}

	elapsed := time.Since(pr.stats.StartTime)
	bytesScanned := pr.stats.BytesScanned.Load()
	bytesSkipped := pr.stats.BytesSkipped.Load()
	bytesProcessed := pr.stats.BytesProcessed.Load()
	totalSize := pr.stats.TotalSize.Load()
	currentFile, _ := pr.stats.CurrentFile.Load().(string)

	// Calculate ETA if we have total size and are processing
	etaStr := ""

	if totalSize > 0 && bytesProcessed > 0 {
		processStart, ok := pr.stats.ProcessStartTime.Load().(time.Time)
		if ok && !processStart.IsZero() {
			processElapsed := time.Since(processStart)

			rate := float64(bytesProcessed) / processElapsed.Seconds()
			if rate > 0 {
				remainingBytes := totalSize - bytesProcessed
				remainingSeconds := float64(remainingBytes) / rate
				eta := time.Duration(remainingSeconds * float64(time.Second))
				etaStr = " | ETA: " + formatDuration(eta)
			}
		}
	}

	rate := float64(bytesScanned+bytesSkipped) / elapsed.Seconds()

	// Show files processed / total files to process
	filesProcessed := pr.stats.FilesProcessed.Load()
	totalFiles := pr.stats.TotalFiles.Load()

	status := fmt.Sprintf("Snapshot progress: %d/%d files, %s/%s (%.1f%%), %s/s%s",
		filesProcessed,
		totalFiles,
		humanize.Bytes(safeUint64(bytesProcessed)),
		humanize.Bytes(safeUint64(totalSize)),
		float64(bytesProcessed)/float64(totalSize)*percentScale,
		humanize.Bytes(uint64(rate)),
		etaStr,
	)

	if currentFile != "" {
		status += " | Current: " + truncatePath(currentFile, currentFileMaxLen)
	}

	log.Info(status)
}

// printDetailedStatus prints a multi-line detailed status
func (pr *ProgressReporter) printDetailedStatus() {
	pr.stats.mu.Lock()
	pr.stats.lastDetailTime = time.Now().UTC()
	pr.stats.mu.Unlock()

	elapsed := time.Since(pr.stats.StartTime)
	filesScanned := pr.stats.FilesScanned.Load()
	filesSkipped := pr.stats.FilesSkipped.Load()
	bytesScanned := pr.stats.BytesScanned.Load()
	bytesSkipped := pr.stats.BytesSkipped.Load()
	bytesProcessed := pr.stats.BytesProcessed.Load()
	totalSize := pr.stats.TotalSize.Load()
	chunksCreated := pr.stats.ChunksCreated.Load()
	blobsCreated := pr.stats.BlobsCreated.Load()
	blobsUploaded := pr.stats.BlobsUploaded.Load()
	bytesUploaded := pr.stats.BytesUploaded.Load()
	currentFile, _ := pr.stats.CurrentFile.Load().(string)

	totalBytes := bytesScanned + bytesSkipped
	rate := float64(totalBytes) / elapsed.Seconds()

	log.Notice("=== Snapshot Progress Report ===")
	log.Info("Elapsed time", "duration", formatDuration(elapsed))

	// Calculate and show ETA if we have data
	if totalSize > 0 && bytesProcessed > 0 {
		processStart, ok := pr.stats.ProcessStartTime.Load().(time.Time)
		if ok && !processStart.IsZero() {
			processElapsed := time.Since(processStart)

			processRate := float64(bytesProcessed) / processElapsed.Seconds()
			if processRate > 0 {
				remainingBytes := totalSize - bytesProcessed
				remainingSeconds := float64(remainingBytes) / processRate
				eta := time.Duration(remainingSeconds * float64(time.Second))
				percentComplete := float64(bytesProcessed) / float64(totalSize) * percentScale
				log.Info("Overall progress",
					"percent", fmt.Sprintf("%.1f%%", percentComplete),
					"processed", humanize.Bytes(safeUint64(bytesProcessed)),
					"total", humanize.Bytes(safeUint64(totalSize)),
					"rate", humanize.Bytes(uint64(processRate))+"/s",
					"eta", formatDuration(eta))
			}
		}
	}

	log.Info("Files processed",
		"scanned", filesScanned,
		"skipped", filesSkipped,
		"total", filesScanned,
		"skip_rate", formatPercent(filesSkipped, filesScanned))
	log.Info("Data scanned",
		"new", humanize.Bytes(safeUint64(bytesScanned)),
		"skipped", humanize.Bytes(safeUint64(bytesSkipped)),
		"total", humanize.Bytes(safeUint64(totalBytes)),
		"scan_rate", humanize.Bytes(uint64(rate))+"/s")
	log.Info("Chunks created", "count", chunksCreated)
	log.Info("Blobs status",
		"created", blobsCreated,
		"uploaded", blobsUploaded,
		"pending", blobsCreated-blobsUploaded)
	log.Info("Total uploaded to remote",
		"uploaded", humanize.Bytes(safeUint64(bytesUploaded)),
		"compression_ratio", formatRatio(bytesUploaded, bytesScanned))

	if currentFile != "" {
		log.Info("Current file", "path", currentFile)
	}

	log.Notice("=============================")
}

// printUploadProgress prints upload progress
func (pr *ProgressReporter) printUploadProgress(_ *UploadInfo) {
	// This function is called repeatedly during upload, not just at start
	// Don't print anything here - the actual progress is shown by ReportUploadProgress
}