From fa21dfea991fd1a15edbe499e3a14c602ddf4f95 Mon Sep 17 00:00:00 2001
From: William Reid <william.reid@uconn.edu>
Date: Thu, 6 Dec 2018 19:41:36 -0500
Subject: [PATCH] Example exercise message sender and data types added

---
 README.md                | Bin 42 -> 6324 bytes
 data-types/data-types.go |  15 ++++
 hello.go                 |   9 ---
 sender/sender.go         | 161 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 176 insertions(+), 9 deletions(-)
 create mode 100644 data-types/data-types.go
 delete mode 100644 hello.go
 create mode 100644 sender/sender.go

diff --git a/README.md b/README.md
index 863462b85441d6dc9406d334cc0e10e5eda013c4..42732fcd6777f360eac34dba791a4f5d3a0448ae 100644
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diff --git a/data-types/data-types.go b/data-types/data-types.go
new file mode 100644
index 0000000..5f0982a
--- /dev/null
+++ b/data-types/data-types.go
@@ -0,0 +1,15 @@
+package data_types
+
+// This file contains data types that are shared between the sender and the responder you will write.
+
+// Struct to manage responses we get
+type ResponseStruct struct {
+	ID int `json:"id"`
+}
+
+// Struct to manage data we're sending
+type DataStruct struct {
+	ID       int `json:"id"`
+	Duration int `json:"duration"`
+	Stamp    int `json:"stamp"`
+}
diff --git a/hello.go b/hello.go
deleted file mode 100644
index 17957ee..0000000
--- a/hello.go
+++ /dev/null
@@ -1,9 +0,0 @@
-package main
-
-import (
-	"fmt"
-)
-
-func main() {
-	fmt.Printf("hello, world\n")
-}
diff --git a/sender/sender.go b/sender/sender.go
new file mode 100644
index 0000000..d4e4fd2
--- /dev/null
+++ b/sender/sender.go
@@ -0,0 +1,161 @@
+package main
+
+import (
+	"fmt"
+	"generator-server/data-types"
+	"github.com/gorilla/websocket"
+	"math/rand"
+	"strconv"
+	"sync"
+	"time"
+)
+
+/* This file tries to make a websocket connection to your server, and then sends it 100 messages at varying intervals
+ * that request a response after a certain duration. Your server will read the messages, wait that amount of time,
+ * and then send a message back with the IDs of the messages it has waited for.
+ */
+
+var globalwait sync.WaitGroup
+
+func main() {
+	// Initialize the waitgroup that will keep this running until the senders are done
+	globalwait = sync.WaitGroup{}
+
+	// Create and start some senders
+	for i := 0; i < 5; i++ {
+		// Try to get a websocket connection
+		c, _, err := websocket.DefaultDialer.Dial("ws://localhost:3000/v1/ws", nil)
+		if err != nil {
+			fmt.Println(err.Error())
+			return
+		}
+
+		// Name the senders 0-4
+		sender := NewSender(strconv.Itoa(i), c)
+		sender.run()
+		time.Sleep(3 * time.Second)
+
+	}
+
+	// Wait on the waitgroup
+	globalwait.Wait()
+}
+
+// Struct to manage our data senders
+type sender struct {
+	name  string
+	conn  *websocket.Conn
+	lock  sync.RWMutex
+	check *checker
+}
+
+// Initialize and return a sender
+func NewSender(n string, conn *websocket.Conn) *sender {
+	return &sender{name: n, conn: conn, lock: sync.RWMutex{}, check: NewChecker()}
+}
+
+// Wrapper around the async run routine that tells globalwait there's something going on and starts the sender
+func (s *sender) run() {
+	globalwait.Add(1)
+	go s._run()
+}
+
+// main sender routine
+func (s *sender) _run() {
+
+	// Need to wait on checker, then close the connection and tell globalwait we're done
+	defer func() {
+		s.check.wg.Wait()
+		s.conn.WriteMessage(websocket.CloseMessage, nil)
+		s.conn.Close()
+		globalwait.Done()
+	}()
+
+	// Start the listener for this sender
+	go s.listen()
+
+	// Change the seed so we don't get the same thing every time
+	rand.Seed(int64(time.Now().Unix()))
+
+	// Loop and send packets
+	for i := 0; i < 100; i++ {
+		// Get a random duration
+		d := rand.Intn(3)
+
+		// Send ID, duration, timestamp
+		ds := &data_types.DataStruct{ID: i, Duration: d, Stamp: int(time.Now().Unix())}
+
+		// Tell the sender to send the packet
+		go s.send(ds)
+
+		// Wait a random amount of time
+		time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
+	}
+}
+
+// Main thread for listening for responses
+func (s *sender) listen() {
+
+	// initialize a response struct to unpack response into
+	var r data_types.ResponseStruct
+
+	// while loop -- repeat indefinitely
+	for {
+		err := s.conn.ReadJSON(&r)
+		if err != nil {
+			if websocket.IsUnexpectedCloseError(err) {
+				fmt.Printf("Sender %v lost reading connection: %v\n", s.name, err.Error())
+			}
+			break
+		}
+
+		// Tell the checker we got a response
+		s.received(r.ID)
+	}
+}
+
+// type for our response checking management
+type checker struct {
+	m    map[int]*data_types.DataStruct
+	lock sync.RWMutex
+	wg   sync.WaitGroup
+}
+
+// Method to get a new, empty checker
+func NewChecker() *checker {
+	return &checker{m: make(map[int]*data_types.DataStruct), lock: sync.RWMutex{}, wg: sync.WaitGroup{}}
+}
+
+// Tell the checker we sent something
+func (s *sender) send(ds *data_types.DataStruct) {
+
+	// Add to wait group
+	s.check.wg.Add(1)
+
+	// Send the message, lock to be safe
+	s.lock.Lock()
+	if err := s.conn.WriteJSON(ds); err != nil {
+		fmt.Printf("Sender %v error writing: %v", s.name, err.Error())
+	}
+	s.lock.Unlock()
+
+	// Add to checker map, lock to be safe
+	s.check.lock.Lock()
+	s.check.m[ds.ID] = ds
+	s.check.lock.Unlock()
+}
+
+// Tell the checker we got something
+func (s *sender) received(i int) {
+
+	// Grab the data entry and then delete it, locking for safe map access
+	s.check.lock.Lock()
+	ds := s.check.m[i]
+	delete(s.check.m, i)
+	s.check.lock.Unlock()
+	s.check.wg.Done()
+
+	// Check how long ago we sent this
+	diff := int(time.Now().Unix()) - ds.Stamp
+	fmt.Printf("sender %v received response for %v at %v seconds later than expected\n", s.name, i, diff-ds.Duration)
+}