package main

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"github.com/dustin/go-humanize"
	"github.com/gotd/td/telegram/message"
	"github.com/gotd/td/tg"
)

const processStartStr = "🔍 Getting information..."
const processStr = "🔨 Processing"
const uploadStr = "☁️ Uploading"
const uploadDoneStr = "🏁 Uploading"
const errorStr = "❌ Error"
const canceledStr = "❌ Canceled"

const maxProgressPercentUpdateInterval = time.Second
const progressBarLength = 10

type DownloadQueueEntry struct {
	URL    string
	Format string

	// IsVideoMessage is true if this entry is for a video message download
	IsVideoMessage bool
	// VideoDocument stores the video document info for video messages
	VideoDocument *tg.Document

	OrigEntities  tg.Entities
	OrigMsgUpdate *tg.UpdateNewMessage
	OrigMsg       *tg.Message
	FromUser      *tg.PeerUser
	FromGroup     *tg.PeerChat

	Reply    *message.Builder
	ReplyMsg *tg.UpdateShortSentMessage

	Ctx       context.Context
	CtxCancel context.CancelFunc
	Canceled  bool
}

func (e *DownloadQueueEntry) sendTypingAction(ctx context.Context) {
}

func (e *DownloadQueueEntry) sendTypingCancelAction(ctx context.Context) {
}

func (e *DownloadQueueEntry) editReply(ctx context.Context, s string) {
	_, _ = e.Reply.Edit(e.ReplyMsg.ID).Text(ctx, s)
	e.sendTypingAction(ctx)
}

type currentlyDownloadedEntryType struct {
	disableProgressPercentUpdate bool
	progressPercentUpdateMutex   sync.Mutex
	lastProgressPercentUpdateAt  time.Time
	lastProgressPercent          int
	lastDisplayedProgressPercent int
	progressUpdateTimer          *time.Timer

	sourceCodecInfo string
	progressInfo    string
}

type DownloadQueue struct {
	ctx context.Context

	mutex          sync.Mutex
	entries        []DownloadQueueEntry
	processReqChan chan bool

	currentlyDownloadedEntry currentlyDownloadedEntryType
}

func (e *DownloadQueue) getQueuePositionString(pos int) string {
	return "👨‍👦‍👦 Request queued at position #" + fmt.Sprint(pos)
}

func (q *DownloadQueue) Add(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage, url, format string) {
	q.addEntry(ctx, entities, u, url, format, false, nil)
}

// AddVideo adds a video message download to the queue
func (q *DownloadQueue) AddVideo(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage, videoDocument *tg.Document) {
	q.addEntry(ctx, entities, u, "", "", true, videoDocument)
}

func (q *DownloadQueue) addEntry(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage, url, format string, isVideo bool, videoDocument *tg.Document) {
	q.mutex.Lock()

	var replyStr string
	if len(q.entries) == 0 {
		if isVideo {
			replyStr = "⬇️ Downloading video..."
		} else {
			replyStr = processStartStr
		}
	} else {
		fmt.Println("  queueing request at position #", len(q.entries))
		replyStr = q.getQueuePositionString(len(q.entries))
	}

	newEntry := DownloadQueueEntry{
		URL:              url,
		Format:           format,
		IsVideoMessage:   isVideo,
		VideoDocument:    videoDocument,
		OrigEntities:     entities,
		OrigMsgUpdate:    u,
		OrigMsg:          u.Message.(*tg.Message),
	}

	newEntry.Reply = telegramSender.Reply(entities, u)
	replyText, _ := newEntry.Reply.Text(ctx, replyStr)
	newEntry.ReplyMsg = replyText.(*tg.UpdateShortSentMessage)

	newEntry.FromUser, newEntry.FromGroup = resolveMsgSrc(newEntry.OrigMsg)

	q.entries = append(q.entries, newEntry)
	q.mutex.Unlock()

	select {
	case q.processReqChan <- true:
	default:
	}
}

func (q *DownloadQueue) CancelCurrentEntry(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage, url string) {
	q.mutex.Lock()
	if len(q.entries) > 0 {
		q.entries[0].Canceled = true
		q.entries[0].CtxCancel()
	} else {
		fmt.Println("  no active request to cancel")
		_, _ = telegramSender.Reply(entities, u).Text(ctx, errorStr+": no active request to cancel")
	}
	q.mutex.Unlock()
}

func (q *DownloadQueue) updateProgress(ctx context.Context, qEntry *DownloadQueueEntry, progressStr string, progressPercent int) {
	if progressPercent < 0 {
		qEntry.editReply(ctx, progressStr+"... (no progress available)\n"+q.currentlyDownloadedEntry.sourceCodecInfo)
		return
	}
	if progressPercent == 0 {
		qEntry.editReply(ctx, progressStr+"..."+q.currentlyDownloadedEntry.progressInfo+"\n"+q.currentlyDownloadedEntry.sourceCodecInfo)
		return
	}
	fmt.Print("  progress: ", progressPercent, "%\n")
	qEntry.editReply(ctx, progressStr+": "+getProgressbar(progressPercent, progressBarLength)+q.currentlyDownloadedEntry.progressInfo+"\n"+q.currentlyDownloadedEntry.sourceCodecInfo)
	q.currentlyDownloadedEntry.lastDisplayedProgressPercent = progressPercent
}

func (q *DownloadQueue) HandleProgressPercentUpdate(progressStr string, progressPercent int) {
	q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
	defer q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()

	if q.currentlyDownloadedEntry.disableProgressPercentUpdate || q.currentlyDownloadedEntry.lastProgressPercent == progressPercent {
		return
	}
	q.currentlyDownloadedEntry.lastProgressPercent = progressPercent
	if progressPercent < 0 {
		q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
		q.updateProgress(q.ctx, &q.entries[0], progressStr, progressPercent)
		return
	}

	if q.currentlyDownloadedEntry.progressUpdateTimer != nil {
		q.currentlyDownloadedEntry.progressUpdateTimer.Stop()
		select {
		case <-q.currentlyDownloadedEntry.progressUpdateTimer.C:
		default:
		}
	}

	timeElapsedSinceLastUpdate := time.Since(q.currentlyDownloadedEntry.lastProgressPercentUpdateAt)
	if timeElapsedSinceLastUpdate < maxProgressPercentUpdateInterval {
		q.currentlyDownloadedEntry.progressUpdateTimer = time.AfterFunc(maxProgressPercentUpdateInterval-timeElapsedSinceLastUpdate, func() {
			q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
			if !q.currentlyDownloadedEntry.disableProgressPercentUpdate {
				q.updateProgress(q.ctx, &q.entries[0], progressStr, progressPercent)
				q.currentlyDownloadedEntry.lastProgressPercentUpdateAt = time.Now()
			}
			q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
		})
		return
	}
	q.updateProgress(q.ctx, &q.entries[0], progressStr, progressPercent)
	q.currentlyDownloadedEntry.lastProgressPercentUpdateAt = time.Now()
}

func (q *DownloadQueue) processQueueEntry(ctx context.Context, qEntry *DownloadQueueEntry) {
	fromUsername := getFromUsername(qEntry.OrigEntities, qEntry.FromUser.UserID)
	fmt.Print("processing request by")
	if fromUsername != "" {
		fmt.Print(" from ", fromUsername, "#", qEntry.FromUser.UserID)
	}

	// Handle video message downloads differently
	if qEntry.IsVideoMessage {
		fmt.Println(": [video message]")
		q.processVideoMessageEntry(ctx, qEntry)
		return
	}

	fmt.Println(":", qEntry.URL)
	qEntry.editReply(ctx, processStartStr)

	downloader := Downloader{
		ConvertStartFunc: func(ctx context.Context, videoCodecs, audioCodecs, convertActionsNeeded string) {
			q.currentlyDownloadedEntry.sourceCodecInfo = "🎬 Source: " + videoCodecs
			if audioCodecs == "" {
				q.currentlyDownloadedEntry.sourceCodecInfo += ", no audio"
			} else {
				if videoCodecs != "" {
					q.currentlyDownloadedEntry.sourceCodecInfo += " / "
				}
				q.currentlyDownloadedEntry.sourceCodecInfo += audioCodecs
			}
			if convertActionsNeeded == "" {
				q.currentlyDownloadedEntry.sourceCodecInfo += " (no conversion needed)"
			} else {
				q.currentlyDownloadedEntry.sourceCodecInfo += " (converting: " + convertActionsNeeded + ")"
			}
			qEntry.editReply(ctx, "🎬 Preparing download...\n"+q.currentlyDownloadedEntry.sourceCodecInfo)
		},
		UpdateProgressPercentFunc: q.HandleProgressPercentUpdate,
	}

	// Download the file to SAVE_DIR
	dlResult, err := downloader.DownloadAndConvertURL(qEntry.Ctx, qEntry.OrigMsg.Message, qEntry.Format)
	if err != nil {
		fmt.Println("  error downloading:", err)
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
		q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
		qEntry.editReply(ctx, fmt.Sprint(errorStr+": ", err))
		return
	}

	// Probe the downloaded file to check codec compatibility
	conv := Converter{
		Format:                        qEntry.Format,
		UpdateProgressPercentCallback: q.HandleProgressPercentUpdate,
	}

	if err := conv.ProbeFile(dlResult.FilePath); err != nil {
		fmt.Println("  error probing file:", err)
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
		q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
		qEntry.editReply(ctx, fmt.Sprint(errorStr+": ", err))
		return
	}

	// Update codec info in UI
	if downloader.ConvertStartFunc != nil {
		downloader.ConvertStartFunc(ctx, conv.VideoCodecs, conv.AudioCodecs, conv.GetActionsNeeded())
	}

	// Check if file is small enough to upload to Telegram (<512MB)
	if dlResult.FileSize >= telegramUploadThreshold {
		// File too large, only save to disk
		fmt.Printf("  file too large (%s >= 512MB), skipping Telegram upload\n", humanize.Bytes(uint64(dlResult.FileSize)))
		qEntry.editReply(ctx, fmt.Sprintf("✅ Saved to server\n📁 %s\n💾 Size: %s\n⚠️ File too large for Telegram upload (>512MB)",
			dlResult.FilePath, humanize.Bytes(uint64(dlResult.FileSize))))
		qEntry.sendTypingCancelAction(ctx)
		return
	}

	// File is small enough, process for upload
	fmt.Println("  processing for upload...")
	q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
	q.updateProgress(ctx, qEntry, processStr, q.currentlyDownloadedEntry.lastProgressPercent)
	q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()

	// Convert if needed, then upload
	uploadPath := dlResult.FilePath
	uploadFormat := "mkv"
	if qEntry.Format == "mp3" {
		uploadFormat = "mp3"
	}

	// For video format, determine the actual format from filename
	if qEntry.Format != "mp3" {
		ext := filepath.Ext(uploadPath)
		if ext != "" {
			uploadFormat = ext[1:] // Remove the leading dot
		}
	}

	if conv.NeedConvert() {
		// Need conversion
		outputPath, outputFormat, err := conv.ConvertIfNeeded(qEntry.Ctx, dlResult.FilePath, params.SaveDir)
		if err != nil {
			fmt.Println("  error converting:", err)
			q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
			q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
			q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
			qEntry.editReply(ctx, fmt.Sprint(errorStr+": ", err))
			return
		}
		uploadPath = outputPath
		uploadFormat = outputFormat
		// Keep both original and converted files
	}

	// Open file for upload
	file, err := os.Open(uploadPath)
	if err != nil {
		fmt.Println("  error opening file:", err)
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
		q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
		qEntry.editReply(ctx, fmt.Sprint(errorStr+": ", err))
		return
	}
	defer file.Close()

	// Upload to Telegram with video dimensions
	err = dlUploader.UploadFile(qEntry.Ctx, qEntry.OrigEntities, qEntry.OrigMsgUpdate, file, uploadFormat, dlResult.Title, conv.VideoWidth, conv.VideoHeight)
	if err != nil {
		fmt.Println("  error uploading:", err)
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
		q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
		q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
		file.Close()
		qEntry.editReply(ctx, fmt.Sprint(errorStr+": ", err))
		return
	}
	file.Close()

	// Remove the uploaded file (since it's saved in SAVE_DIR, we keep it only if needed)
	// Actually, we keep the file in SAVE_DIR as requested

	q.currentlyDownloadedEntry.progressPercentUpdateMutex.Lock()
	q.currentlyDownloadedEntry.disableProgressPercentUpdate = true
	if qEntry.Canceled {
		fmt.Print("  canceled\n")
		q.updateProgress(ctx, qEntry, canceledStr, q.currentlyDownloadedEntry.lastProgressPercent)
	} else if q.currentlyDownloadedEntry.lastDisplayedProgressPercent < 100 {
		fmt.Print("  progress: 100%\n")
		q.updateProgress(ctx, qEntry, uploadDoneStr, 100)
	}
	q.currentlyDownloadedEntry.progressPercentUpdateMutex.Unlock()
	qEntry.sendTypingCancelAction(ctx)
}

func (q *DownloadQueue) processVideoMessageEntry(ctx context.Context, qEntry *DownloadQueueEntry) {
	videoFile := qEntry.VideoDocument
	if videoFile == nil {
		qEntry.editReply(ctx, errorStr+": could not get video info")
		return
	}

	// Get file name
	var fileName string
	for _, attr := range videoFile.Attributes {
		if docAttr, ok := attr.(*tg.DocumentAttributeFilename); ok {
			fileName = docAttr.FileName
			break
		}
	}
	if fileName == "" {
		fileName = fmt.Sprintf("video_%d.mp4", time.Now().Unix())
	}

	// Create safe filename with date prefix: YYYY-MM-DD-{timestamp}-{filename}.{ext}
	now := time.Now()
	dateStr := now.Format("2006-01-02")
	timestamp := now.Unix()
	ext := filepath.Ext(fileName)
	if ext == "" {
		ext = ".mp4"
	}
	safeFileName := fmt.Sprintf("%s-%d%s", dateStr, timestamp, ext)
	filePath := filepath.Join(params.SaveDir, safeFileName)

	// Check if file already exists
	if _, err := os.Stat(filePath); err == nil {
		for i := 1; i < 1000; i++ {
			safeFileName = fmt.Sprintf("%s-%d-%d%s", dateStr, timestamp, i, ext)
			filePath = filepath.Join(params.SaveDir, safeFileName)
			if _, err := os.Stat(filePath); os.IsNotExist(err) {
				break
			}
		}
	}

	// Update progress message
	qEntry.editReply(ctx, "⬇️ Downloading video...")

	// Get file size
	fileSize := videoFile.Size

	// Download file using Telegram client
	fileLoc := &tg.InputDocumentFileLocation{
		ID:            videoFile.ID,
		AccessHash:    videoFile.AccessHash,
		FileReference: videoFile.FileReference,
	}
	fmt.Printf("  downloading video: %s (size: %s)\n", fileName, humanize.Bytes(uint64(fileSize)))

	file, err := os.Create(filePath)
	if err != nil {
		qEntry.editReply(ctx, errorStr+": could not create file")
		return
	}

	// Download with progress
	offset := int64(0)
	chunkSize := int64(1024 * 1024) // 1MB chunks
	lastPercent := 0
	written := int64(0)

	for offset < fileSize {
		select {
		case <-qEntry.Ctx.Done():
			file.Close()
			os.Remove(filePath)
			qEntry.editReply(ctx, "❌ Canceled")
			qEntry.Canceled = true
			return
		default:
		}

		if offset+chunkSize > fileSize {
			chunkSize = fileSize - offset
		}
		// Telegram API requires limit to be divisible by 1KB
		if chunkSize%1024 != 0 {
			// Round down to nearest 1KB boundary
			chunkSize = (chunkSize / 1024) * 1024
			if chunkSize == 0 {
				// If remaining data is less than 1KB, round up to 1KB
				// The API will return the actual remaining bytes
				chunkSize = 1024
			}
		}

		loc := &tg.InputDocumentFileLocation{
			ID:            videoFile.ID,
			AccessHash:    videoFile.AccessHash,
			FileReference: fileLoc.FileReference,
		}

		chunk, err := telegramClient.API().UploadGetFile(qEntry.Ctx, &tg.UploadGetFileRequest{
			Location:     loc,
			Offset:       offset,
			Limit:        int(chunkSize),
			Precise:      true,
			CDNSupported: false,
		})
		if err != nil {
			file.Close()
			os.Remove(filePath)
			qEntry.editReply(ctx, errorStr+": failed to download chunk: "+err.Error())
			return
		}

		chunkData, ok := chunk.(*tg.UploadFile)
		if !ok {
			file.Close()
			os.Remove(filePath)
			qEntry.editReply(ctx, errorStr+": unexpected response type")
			return
		}

		n, err := file.Write(chunkData.Bytes)
		if err != nil {
			file.Close()
			os.Remove(filePath)
			qEntry.editReply(ctx, errorStr+": failed to write to file")
			return
		}

		offset += int64(n)
		written += int64(n)

		// Update progress
		if fileSize > 0 {
			percent := int(float64(written) * 100 / float64(fileSize))
			if percent != lastPercent && percent%10 == 0 {
				lastPercent = percent
				progressBar := getProgressbar(percent, progressBarLength)
				qEntry.editReply(ctx, "⬇️ Downloading video...\n"+progressBar)
			}
		}
	}

	file.Close()

	// Send success message
	savedMsg := fmt.Sprintf("✅ Video saved\n📁 %s\n💾 Size: %s", safeFileName, humanize.Bytes(uint64(written)))
	qEntry.editReply(ctx, savedMsg)

	fmt.Printf("  video saved to: %s\n", filePath)
}

func (q *DownloadQueue) processor() {
	for {
		q.mutex.Lock()
		if (len(q.entries)) == 0 {
			q.mutex.Unlock()
			<-q.processReqChan
			continue
		}

		// Updating queue positions for all waiting entries.
		for i := 1; i < len(q.entries); i++ {
			q.entries[i].editReply(q.ctx, q.getQueuePositionString(i))
			q.entries[i].sendTypingCancelAction(q.ctx)
		}

		q.entries[0].Ctx, q.entries[0].CtxCancel = context.WithTimeout(q.ctx, downloadAndConvertTimeout)

		qEntry := &q.entries[0]
		q.mutex.Unlock()

		q.currentlyDownloadedEntry = currentlyDownloadedEntryType{}

		q.processQueueEntry(q.ctx, qEntry)

		q.mutex.Lock()
		q.entries[0].CtxCancel()
		q.entries = q.entries[1:]
		if len(q.entries) == 0 {
			fmt.Print("finished queue processing\n")
		}
		q.mutex.Unlock()
	}
}

func (q *DownloadQueue) Init(ctx context.Context) {
	q.ctx = ctx
	q.processReqChan = make(chan bool)
	go q.processor()
}