package croc

import (
	"bytes"
	"crypto/elliptic"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"math"
	"os"
	"path"
	"path/filepath"
	"strings"
	"sync"
	"time"

	log "github.com/cihub/seelog"
	"github.com/denisbrodbeck/machineid"
	"github.com/pkg/errors"
	"github.com/schollz/croc/v6/src/comm"
	"github.com/schollz/croc/v6/src/compress"
	"github.com/schollz/croc/v6/src/crypt"
	"github.com/schollz/croc/v6/src/logger"
	"github.com/schollz/croc/v6/src/message"
	"github.com/schollz/croc/v6/src/models"
	"github.com/schollz/croc/v6/src/tcp"
	"github.com/schollz/croc/v6/src/utils"
	"github.com/schollz/pake"
	"github.com/schollz/progressbar/v2"
	"github.com/schollz/spinner"
)

func init() {
	logger.SetLogLevel("debug")
}

func Debug(debug bool) {
	if debug {
		logger.SetLogLevel("debug")
	} else {
		logger.SetLogLevel("warn")
	}
}

type Options struct {
	IsSender     bool
	SharedSecret string
	Debug        bool
	RelayAddress string
	RelayPorts   []string
	Stdout       bool
	NoPrompt     bool
}

type Client struct {
	Options Options
	Pake    *pake.Pake
	Key     crypt.Encryption

	// steps involved in forming relationship
	Step1ChannelSecured       bool
	Step2FileInfoTransfered   bool
	Step3RecipientRequestFile bool
	Step4FileTransfer         bool
	Step5CloseChannels        bool

	// send / receive information of all files
	FilesToTransfer           []FileInfo
	FilesToTransferCurrentNum int

	// send / receive information of current file
	CurrentFile           *os.File
	CurrentFileChunks     []int64
	TotalSent             int64
	TotalChunksTransfered int
	chunkMap              map[uint64]struct{}

	// tcp connections
	conn []*comm.Comm

	bar       *progressbar.ProgressBar
	spinner   *spinner.Spinner
	machineID string

	mutex *sync.Mutex
	quit  chan bool
}

type Chunk struct {
	Bytes    []byte `json:"b,omitempty"`
	Location int64  `json:"l,omitempty"`
}

type FileInfo struct {
	Name         string    `json:"n,omitempty"`
	FolderRemote string    `json:"fr,omitempty"`
	FolderSource string    `json:"fs,omitempty"`
	Hash         []byte    `json:"h,omitempty"`
	Size         int64     `json:"s,omitempty"`
	ModTime      time.Time `json:"m,omitempty"`
	IsCompressed bool      `json:"c,omitempty"`
	IsEncrypted  bool      `json:"e,omitempty"`
}

type RemoteFileRequest struct {
	CurrentFileChunks         []int64
	FilesToTransferCurrentNum int
}

type SenderInfo struct {
	MachineID       string
	FilesToTransfer []FileInfo
}

// New establishes a new connection for transfering files between two instances.
func New(ops Options) (c *Client, err error) {
	c = new(Client)

	// setup basic info
	c.Options = ops
	Debug(c.Options.Debug)
	log.Debugf("options: %+v", c.Options)

	log.Debug("establishing connection")
	c.conn = make([]*comm.Comm, len(c.Options.RelayPorts))
	// connect to the relay for messaging
	c.conn[0], err = tcp.ConnectToTCPServer(fmt.Sprintf("%s:%s", c.Options.RelayAddress, c.Options.RelayPorts[0]), c.Options.SharedSecret)
	if err != nil {
		err = errors.Wrap(err, fmt.Sprintf("could not connect to %s:%s", c.Options.RelayAddress, c.Options.RelayPorts[0]))
		return
	}
	log.Debugf("connection established: %+v", c.conn[0])

	// use default key (no encryption, until PAKE succeeds)
	c.Key, err = crypt.New(nil, nil)
	if err != nil {
		return
	}

	// initialize pake
	if c.Options.IsSender {
		c.Pake, err = pake.Init([]byte(c.Options.SharedSecret), 1, elliptic.P521(), 1*time.Microsecond)
	} else {
		c.Pake, err = pake.Init([]byte(c.Options.SharedSecret), 0, elliptic.P521(), 1*time.Microsecond)
	}
	if err != nil {
		return
	}

	c.mutex = &sync.Mutex{}
	return
}

// TransferOptions for sending
type TransferOptions struct {
	PathToFiles      []string
	KeepPathInRemote bool
}

// Send will send the specified file
func (c *Client) Send(options TransferOptions) (err error) {
	return c.transfer(options)
}

// Receive will receive a file
func (c *Client) Receive() (err error) {
	return c.transfer(TransferOptions{})
}

func (c *Client) transfer(options TransferOptions) (err error) {
	// connect to the server

	if c.Options.IsSender {
		c.FilesToTransfer = make([]FileInfo, len(options.PathToFiles))
		totalFilesSize := int64(0)
		for i, pathToFile := range options.PathToFiles {
			var fstats os.FileInfo
			var fullPath string
			fullPath, err = filepath.Abs(pathToFile)
			if err != nil {
				return
			}
			fullPath = filepath.Clean(fullPath)
			var folderName string
			folderName, _ = filepath.Split(fullPath)

			fstats, err = os.Stat(fullPath)
			if err != nil {
				return
			}
			c.FilesToTransfer[i] = FileInfo{
				Name:         fstats.Name(),
				FolderRemote: ".",
				FolderSource: folderName,
				Size:         fstats.Size(),
				ModTime:      fstats.ModTime(),
			}
			c.FilesToTransfer[i].Hash, err = utils.HashFile(fullPath)
			totalFilesSize += fstats.Size()
			if err != nil {
				return
			}
			if options.KeepPathInRemote {
				var curFolder string
				curFolder, err = os.Getwd()
				if err != nil {
					return
				}
				curFolder, err = filepath.Abs(curFolder)
				if err != nil {
					return
				}
				if !strings.HasPrefix(folderName, curFolder) {
					err = fmt.Errorf("remote directory must be relative to current")
					return
				}
				c.FilesToTransfer[i].FolderRemote = strings.TrimPrefix(folderName, curFolder)
				c.FilesToTransfer[i].FolderRemote = filepath.ToSlash(c.FilesToTransfer[i].FolderRemote)
				c.FilesToTransfer[i].FolderRemote = strings.TrimPrefix(c.FilesToTransfer[i].FolderRemote, "/")
				if c.FilesToTransfer[i].FolderRemote == "" {
					c.FilesToTransfer[i].FolderRemote = "."
				}
			}
			log.Debugf("file %d info: %+v", i, c.FilesToTransfer[i])
		}
		fname := fmt.Sprintf("%d files", len(c.FilesToTransfer))
		if len(c.FilesToTransfer) == 1 {
			fname = fmt.Sprintf("'%s'", c.FilesToTransfer[0].Name)
		}
		machID, macIDerr := machineid.ID()
		if macIDerr != nil {
			log.Error(macIDerr)
			return
		}
		if len(machID) > 6 {
			machID = machID[:6]
		}
		c.machineID = machID
		fmt.Fprintf(os.Stderr, "Sending %s (%s) from your machine, '%s'\n", fname, utils.ByteCountDecimal(totalFilesSize), machID)
		fmt.Fprintf(os.Stderr, "Code is: %s\nOn the other computer run\n\ncroc %s\n", c.Options.SharedSecret, c.Options.SharedSecret)
		// // c.spinner.Suffix = " waiting for recipient..."
	}
	// c.spinner.Start()
	// create channel for quitting
	// quit with c.quit <- true
	c.quit = make(chan bool)

	// if recipient, initialize with sending pake information
	log.Debug("ready")
	if !c.Options.IsSender && !c.Step1ChannelSecured {
		err = message.Send(c.conn[0], c.Key, message.Message{
			Type:  "pake",
			Bytes: c.Pake.Bytes(),
		})
		if err != nil {
			return
		}
	}

	// listen for incoming messages and process them
	for {
		var data []byte
		var done bool
		data, err = c.conn[0].Receive()
		if err != nil {
			return
		}
		done, err = c.processMessage(data)
		if err != nil {
			return
		}
		if done {
			break
		}
	}
	return
}

func (c *Client) processMessage(payload []byte) (done bool, err error) {
	m, err := message.Decode(c.Key, payload)
	if err != nil {
		return
	}

	switch m.Type {
	case "finished":
		err = message.Send(c.conn[0], c.Key, message.Message{
			Type: "finished",
		})
		done = true
		return
	case "pake":
		// if // c.spinner.Suffix != " performing PAKE..." {
		// 	// c.spinner.Stop()
		// 	// c.spinner.Suffix = " performing PAKE..."
		// 	// c.spinner.Start()
		// }
		notVerified := !c.Pake.IsVerified()
		err = c.Pake.Update(m.Bytes)
		if err != nil {
			return
		}
		if (notVerified && c.Pake.IsVerified() && !c.Options.IsSender) || !c.Pake.IsVerified() {
			err = message.Send(c.conn[0], c.Key, message.Message{
				Type:  "pake",
				Bytes: c.Pake.Bytes(),
			})
		}
		if c.Pake.IsVerified() {
			log.Debug("session key is verified, generating encryption")
			key, err := c.Pake.SessionKey()
			if err != nil {
				return true, err
			}
			c.Key, err = crypt.New(key, []byte(c.Options.SharedSecret))
			if err != nil {
				return true, err
			}

			// connects to the other ports of the server for transfer
			var wg sync.WaitGroup
			wg.Add(len(c.Options.RelayPorts) - 1)
			for i := 1; i < len(c.Options.RelayPorts); i++ {
				go func(j int) {
					defer wg.Done()
					c.conn[j], err = tcp.ConnectToTCPServer(
						fmt.Sprintf("%s:%s", c.Options.RelayAddress, c.Options.RelayPorts[j]),
						fmt.Sprintf("%s-%d", utils.SHA256(c.Options.SharedSecret)[:7], j),
					)
					if err != nil {
						panic(err)
					}
					if !c.Options.IsSender {
						go c.receiveData(j)
					}
				}(i)
			}
			wg.Wait()
			c.Step1ChannelSecured = true
		}
	case "error":
		// c.spinner.Stop()
		fmt.Print("\r")
		err = fmt.Errorf("peer error: %s", m.Message)
		return true, err
	case "fileinfo":
		var senderInfo SenderInfo
		err = json.Unmarshal(m.Bytes, &senderInfo)
		if err != nil {
			log.Error(err)
			return
		}
		c.FilesToTransfer = senderInfo.FilesToTransfer
		fname := fmt.Sprintf("%d files", len(c.FilesToTransfer))
		if len(c.FilesToTransfer) == 1 {
			fname = fmt.Sprintf("'%s'", c.FilesToTransfer[0].Name)
		}
		totalSize := int64(0)
		for _, fi := range c.FilesToTransfer {
			totalSize += fi.Size
		}
		// c.spinner.Stop()
		if !c.Options.NoPrompt {
			fmt.Fprintf(os.Stderr, "\rAccept %s (%s) from machine '%s'? (y/n) ", fname, utils.ByteCountDecimal(totalSize), senderInfo.MachineID)
			if strings.ToLower(strings.TrimSpace(utils.GetInput(""))) != "y" {
				err = message.Send(c.conn[0], c.Key, message.Message{
					Type:    "error",
					Message: "refusing files",
				})
				return true, fmt.Errorf("refused files")
			}
		} else {
			fmt.Fprintf(os.Stderr, "\rReceiving %s (%s) from machine '%s'\n", fname, utils.ByteCountDecimal(totalSize), senderInfo.MachineID)
		}
		log.Debug(c.FilesToTransfer)
		c.Step2FileInfoTransfered = true
	case "recipientready":
		var remoteFile RemoteFileRequest
		err = json.Unmarshal(m.Bytes, &remoteFile)
		if err != nil {
			return
		}
		c.FilesToTransferCurrentNum = remoteFile.FilesToTransferCurrentNum
		c.CurrentFileChunks = remoteFile.CurrentFileChunks
		log.Debugf("current file chunks: %+v", c.CurrentFileChunks)
		c.chunkMap = make(map[uint64]struct{})
		for _, chunk := range c.CurrentFileChunks {
			c.chunkMap[uint64(chunk)] = struct{}{}
		}
		c.Step3RecipientRequestFile = true
	case "close-sender":
		log.Debug("close-sender received...")
		c.Step4FileTransfer = false
		c.Step3RecipientRequestFile = false
		log.Debug("sending close-recipient")
		err = message.Send(c.conn[0], c.Key, message.Message{
			Type: "close-recipient",
		})
	case "close-recipient":
		c.Step4FileTransfer = false
		c.Step3RecipientRequestFile = false
	}
	if err != nil {
		return
	}
	err = c.updateState()

	return
}

func (c *Client) updateState() (err error) {
	if c.Options.IsSender && c.Step1ChannelSecured && !c.Step2FileInfoTransfered {
		var b []byte
		b, err = json.Marshal(SenderInfo{
			MachineID:       c.machineID,
			FilesToTransfer: c.FilesToTransfer,
		})
		if err != nil {
			log.Error(err)
			return
		}
		err = message.Send(c.conn[0], c.Key, message.Message{
			Type:  "fileinfo",
			Bytes: b,
		})
		if err != nil {
			return
		}
		c.Step2FileInfoTransfered = true
	}
	if !c.Options.IsSender && c.Step2FileInfoTransfered && !c.Step3RecipientRequestFile {
		// find the next file to transfer and send that number
		// if the files are the same size, then look for missing chunks
		finished := true
		for i, fileInfo := range c.FilesToTransfer {
			if i < c.FilesToTransferCurrentNum {
				continue
			}
			fileHash, errHash := utils.HashFile(path.Join(fileInfo.FolderRemote, fileInfo.Name))
			if errHash != nil || !bytes.Equal(fileHash, fileInfo.Hash) {
				if !bytes.Equal(fileHash, fileInfo.Hash) {
					log.Debugf("hashes are not equal %x != %x", fileHash, fileInfo.Hash)
				}
				finished = false
				c.FilesToTransferCurrentNum = i
				break
			}
			// TODO: print out something about this file already existing
		}
		if finished {
			// TODO: do the last finishing stuff
			log.Debug("finished")
			err = message.Send(c.conn[0], c.Key, message.Message{
				Type: "finished",
			})
			if err != nil {
				panic(err)
			}
		}

		// start initiating the process to receive a new file
		log.Debugf("working on file %d", c.FilesToTransferCurrentNum)

		// recipient sets the file
		pathToFile := path.Join(
			c.FilesToTransfer[c.FilesToTransferCurrentNum].FolderRemote,
			c.FilesToTransfer[c.FilesToTransferCurrentNum].Name,
		)
		folderForFile, _ := filepath.Split(pathToFile)
		os.MkdirAll(folderForFile, os.ModePerm)
		var errOpen error
		c.CurrentFile, errOpen = os.OpenFile(
			pathToFile,
			os.O_WRONLY, 0666)
		truncate := false
		c.CurrentFileChunks = []int64{}
		if errOpen == nil {
			stat, _ := c.CurrentFile.Stat()
			truncate = stat.Size() != c.FilesToTransfer[c.FilesToTransferCurrentNum].Size
			if truncate == false {
				// recipient requests the file and chunks (if empty, then should receive all chunks)
				// TODO: determine the missing chunks
				c.CurrentFileChunks = utils.MissingChunks(
					pathToFile,
					c.FilesToTransfer[c.FilesToTransferCurrentNum].Size,
					models.TCP_BUFFER_SIZE/2,
				)
			}
		} else {
			c.CurrentFile, errOpen = os.Create(pathToFile)
			if errOpen != nil {
				errOpen = errors.Wrap(errOpen, "could not create "+pathToFile)
				log.Error(errOpen)
				return errOpen
			}
			truncate = true
		}
		if truncate {
			err := c.CurrentFile.Truncate(c.FilesToTransfer[c.FilesToTransferCurrentNum].Size)
			if err != nil {
				err = errors.Wrap(err, "could not truncate "+pathToFile)
				log.Error(err)
				return err
			}
		}

		// setup the progressbar
		c.bar = progressbar.NewOptions64(
			c.FilesToTransfer[c.FilesToTransferCurrentNum].Size,
			progressbar.OptionOnCompletion(func() {
				fmt.Fprintf(os.Stderr, " ✔️\n")
			}),
			progressbar.OptionSetWidth(8),
			progressbar.OptionSetDescription(fmt.Sprintf("%28s", c.FilesToTransfer[c.FilesToTransferCurrentNum].Name)),
			progressbar.OptionSetRenderBlankState(true),
			progressbar.OptionSetBytes64(c.FilesToTransfer[c.FilesToTransferCurrentNum].Size),
			progressbar.OptionSetWriter(os.Stderr),
			progressbar.OptionThrottle(100*time.Millisecond),
		)
		c.bar.Add(len(c.CurrentFileChunks) * models.TCP_BUFFER_SIZE / 2)
		c.TotalSent = 0
		bRequest, _ := json.Marshal(RemoteFileRequest{
			CurrentFileChunks:         c.CurrentFileChunks,
			FilesToTransferCurrentNum: c.FilesToTransferCurrentNum,
		})
		err = message.Send(c.conn[0], c.Key, message.Message{
			Type:  "recipientready",
			Bytes: bRequest,
		})
		if err != nil {
			return
		}
		c.Step3RecipientRequestFile = true
	}
	if c.Options.IsSender && c.Step3RecipientRequestFile && !c.Step4FileTransfer {
		log.Debug("start sending data!")
		c.Step4FileTransfer = true
		// setup the progressbar
		c.bar = progressbar.NewOptions64(
			c.FilesToTransfer[c.FilesToTransferCurrentNum].Size,
			progressbar.OptionOnCompletion(func() {
				fmt.Fprintf(os.Stderr, " ✔️\n")
			}),
			progressbar.OptionSetWidth(8),
			progressbar.OptionSetDescription(fmt.Sprintf("%28s", c.FilesToTransfer[c.FilesToTransferCurrentNum].Name)),
			progressbar.OptionSetRenderBlankState(true),
			progressbar.OptionSetBytes64(c.FilesToTransfer[c.FilesToTransferCurrentNum].Size),
			progressbar.OptionSetWriter(os.Stderr),
			progressbar.OptionThrottle(100*time.Millisecond),
		)
		c.bar.Add(len(c.CurrentFileChunks) * models.TCP_BUFFER_SIZE / 2)
		c.TotalSent = 0
		for i := 1; i < len(c.Options.RelayPorts); i++ {
			go c.sendData(i)
		}
	}
	return
}

func (c *Client) receiveData(i int) {
	for {
		log.Debug("waiting for data")
		data, err := c.conn[i].Receive()
		if err != nil {
			break
		}

		data, err = c.Key.Decrypt(data)
		if err != nil {
			panic(err)
		}
		data = compress.Decompress(data)

		// get position
		var position uint64
		rbuf := bytes.NewReader(data[:8])
		err = binary.Read(rbuf, binary.LittleEndian, &position)
		if err != nil {
			panic(err)
		}
		positionInt64 := int64(position)

		c.mutex.Lock()
		_, err = c.CurrentFile.WriteAt(data[8:], positionInt64)
		c.mutex.Unlock()
		if err != nil {
			panic(err)
		}
		c.bar.Add(len(data[8:]))
		c.TotalSent += int64(len(data[8:]))
		c.TotalChunksTransfered++
		log.Debugf("block: %+v", positionInt64)
		if c.TotalChunksTransfered == len(c.CurrentFileChunks) || c.TotalSent == c.FilesToTransfer[c.FilesToTransferCurrentNum].Size {
			log.Debug("finished receiving!")
			c.CurrentFile.Close()
			log.Debug("sending close-sender")
			err = message.Send(c.conn[0], c.Key, message.Message{
				Type: "close-sender",
			})
			if err != nil {
				panic(err)
			}
		}
	}

	return
}

func (c *Client) sendData(i int) {
	defer func() {
		log.Debugf("finished with %d", i)
	}()
	pathToFile := path.Join(
		c.FilesToTransfer[c.FilesToTransferCurrentNum].FolderSource,
		c.FilesToTransfer[c.FilesToTransferCurrentNum].Name,
	)
	log.Debugf("opening %s to read", pathToFile)
	f, err := os.Open(pathToFile)
	if err != nil {
		panic(err)
	}
	defer f.Close()

	pos := uint64(0)
	curi := float64(0)
	for {
		// Read file
		data := make([]byte, models.TCP_BUFFER_SIZE/2)
		n, err := f.Read(data)
		if err != nil {
			if err == io.EOF {
				break
			}
			panic(err)
		}

		if math.Mod(curi, float64(len(c.Options.RelayPorts)-1))+1 == float64(i) {
			// check to see if this is a chunk that the recipient wants
			usableChunk := true
			c.mutex.Lock()
			if len(c.chunkMap) != 0 {
				if _, ok := c.chunkMap[pos]; !ok {
					usableChunk = false
				} else {
					delete(c.chunkMap, pos)
				}
			}
			c.mutex.Unlock()
			if usableChunk {
				// log.Debugf("sending chunk %d", pos)
				posByte := make([]byte, 8)
				binary.LittleEndian.PutUint64(posByte, pos)

				dataToSend, err := c.Key.Encrypt(
					compress.Compress(
						append(posByte, data[:n]...),
					),
				)
				if err != nil {
					panic(err)
				}

				err = c.conn[i].Send(dataToSend)
				if err != nil {
					panic(err)
				}
				c.bar.Add(n)
				c.TotalSent += int64(n)
				// time.Sleep(100 * time.Millisecond)
			} else {
				// log.Debugf("skipping chunk %d", pos)
			}
		}

		curi++
		pos += uint64(n)
	}

	time.Sleep(10 * time.Second)
	return
}