From 5064eaecebd1c20e8397dbc0ceb1dc22e3395b6d Mon Sep 17 00:00:00 2001
From: abdfnx <abdfnabd@gmail.com>
Date: Fri, 4 Feb 2022 11:06:53 +0300
Subject: [PATCH] add new constants, build tran sender transfer functions and
 handlers

---
 constants/constants.go  |   3 +
 core/sender/transfer.go | 164 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 167 insertions(+)
 create mode 100644 core/sender/transfer.go

diff --git a/constants/constants.go b/constants/constants.go
index f9fa957..48ab086 100644
--- a/constants/constants.go
+++ b/constants/constants.go
@@ -13,6 +13,9 @@ import (
 const DEFAULT_ADDRESS = "167.71.65.96"
 const DEFAULT_PORT = 80
 
+const MAX_CHUNK_BYTES = 1e6
+const MAX_SEND_CHUNKS = 2e8
+
 const RECEIVER_CONNECT_TIMEOUT time.Duration = 5 * time.Minute
 
 const SEND_TEMP_FILE_NAME_PREFIX = "tran-send-tmp"
diff --git a/core/sender/transfer.go b/core/sender/transfer.go
new file mode 100644
index 0000000..d15ed23
--- /dev/null
+++ b/core/sender/transfer.go
@@ -0,0 +1,164 @@
+package sender
+
+import (
+	"io"
+	"fmt"
+	"log"
+	"bufio"
+	"syscall"
+
+	"github.com/gorilla/websocket"
+	"github.com/abdfnx/tran/tools"
+	"github.com/abdfnx/tran/constants"
+	"github.com/abdfnx/tran/models/protocol"
+)
+
+// Transfer is the file transfer sequence, can be via relay or tranx.
+func (s *Sender) Transfer(wsConn *websocket.Conn) error {
+	s.state = WaitForFileRequest
+
+	for {
+		// Read incoming message.
+		receivedMsg, err := tools.ReadEncryptedMessage(wsConn, s.crypt)
+		if err != nil {
+			wsConn.Close()
+			s.closeServer <- syscall.SIGTERM
+			return fmt.Errorf("shutting down tran due to websocket error: %s", err)
+		}
+
+		// main switch for action based on incoming message.
+		// The states flows from top down. States checks are performend at each step.
+		switch receivedMsg.Type {
+			case protocol.ReceiverRequestPayload:
+				if s.state != WaitForFileRequest {
+					err = tools.WriteEncryptedMessage(wsConn, protocol.TransferMessage{
+						Type:    protocol.TransferError,
+						Payload: fmt.Sprintf("Tran unsynchronized, expected state: %s, actual: %s", WaitForFileRequest.Name(), s.state.Name()),
+					}, s.crypt)
+
+					if err != nil {
+						return err
+					}
+
+					wsConn.Close()
+					s.closeServer <- syscall.SIGTERM
+
+					return NewWrongStateError(WaitForFileRequest, s.state)
+				}
+
+				err = s.streamPayload(wsConn)
+				if err != nil {
+					log.Println("error in payload streaming:", err)
+
+					return err
+				}
+
+				err = tools.WriteEncryptedMessage(wsConn, protocol.TransferMessage{
+					Type:    protocol.SenderPayloadSent,
+					Payload: "Tran transfer completed",
+				}, s.crypt)
+
+				if err != nil {
+					return err
+				}
+
+				s.state = WaitForFileAck
+				s.updateUI()
+
+			case protocol.ReceiverPayloadAck:
+				if s.state != WaitForFileAck {
+					err = tools.WriteEncryptedMessage(wsConn, protocol.TransferMessage{
+						Type:    protocol.TransferError,
+						Payload: fmt.Sprintf("Tran unsynchronized, expected state: %s, actual: %s", WaitForFileAck.Name(), s.state.Name()),
+					}, s.crypt)
+
+					if err != nil {
+						return err
+					}
+
+					wsConn.Close()
+					s.closeServer <- syscall.SIGTERM
+
+					return NewWrongStateError(WaitForFileAck, s.state)
+				}
+
+				s.state = WaitForCloseMessage
+				s.updateUI()
+
+				err = tools.WriteEncryptedMessage(wsConn, protocol.TransferMessage{
+					Type:    protocol.SenderClosing,
+					Payload: "Closing down Tran as requested",
+				}, s.crypt)
+
+				if err != nil {
+					return err
+				}
+
+				s.state = WaitForCloseAck
+				s.updateUI()
+
+			case protocol.ReceiverClosingAck:
+				wsConn.Close()
+				s.closeServer <- syscall.SIGTERM
+
+				if s.state != WaitForCloseAck {
+					return NewWrongStateError(WaitForCloseAck, s.state)
+				}
+
+				return nil
+
+			case protocol.TransferError:
+				s.updateUI()
+				log.Println("Shutting down Tran due to a transfer error")
+				wsConn.Close()
+				s.closeServer <- syscall.SIGTERM
+
+				return fmt.Errorf("TransferError during file transfer")
+		}
+	}
+}
+
+// streamPayload streams the payload over the provided websocket connection while reporting the progress.
+func (s *Sender) streamPayload(wsConn *websocket.Conn) error {
+	bufReader := bufio.NewReader(s.payload)
+	chunkSize := ChunkSize(s.payloadSize)
+	buffer := make([]byte, chunkSize)
+
+	var bytesSent int
+
+	for {
+		n, err := bufReader.Read(buffer)
+		bytesSent += n
+		enc, encErr := s.crypt.Encrypt(buffer[:n])
+
+		if encErr != nil {
+			return encErr
+		}
+
+		wsConn.WriteMessage(websocket.BinaryMessage, enc)
+		progress := float32(bytesSent) / float32(s.payloadSize)
+		s.updateUI(progress)
+
+		if err == io.EOF {
+			break
+		}
+	}
+
+	return nil
+}
+
+// ChunkSize returns an appropriate chunk size for the payload size
+func ChunkSize(payloadSize int64) int64 {
+	// clamp amount of chunks to be at most MAX_SEND_CHUNKS if it exceeds
+	if payloadSize / constants.MAX_CHUNK_BYTES > constants.MAX_SEND_CHUNKS {
+		return int64(payloadSize) / constants.MAX_SEND_CHUNKS
+	}
+	// if not exceeding MAX_SEND_CHUNKS, divide up no. of chunks to MAX_CHUNK_BYTES-sized chunks
+	chunkSize := int64(payloadSize) / constants.MAX_CHUNK_BYTES
+	// clamp amount of chunks to be at least MAX_CHUNK_BYTES
+	if chunkSize <= constants.MAX_CHUNK_BYTES {
+		return constants.MAX_CHUNK_BYTES
+	}
+
+	return chunkSize
+}