Compare commits
10 Commits
d8f5c27bd4
...
e998fbd230
| Author | SHA1 | Date | |
|---|---|---|---|
| e998fbd230 | |||
| c93b38e8ec | |||
| 76215f14bd | |||
| 5e76ca2514 | |||
| d026a30927 | |||
| e523297d5f | |||
| aee33003bf | |||
| 616017267e | |||
| b94670f138 | |||
| 623bc075eb |
19
AGENTS.md
Normal file
19
AGENTS.md
Normal file
@ -0,0 +1,19 @@
|
||||
# Agent Guidelines for clink
|
||||
|
||||
## Build & Test Commands
|
||||
- Build: `go build -o clink .`
|
||||
- Cross-compile: `./build.sh` (creates binaries in `dist/` for all platforms)
|
||||
- Run client: `go run . -host localhost:9000`
|
||||
- Run server: `go run . -server -host localhost:9000`
|
||||
- Test: `go test ./...` (currently no tests)
|
||||
- Format: `gofmt -w .`
|
||||
- Lint: `go vet ./...`
|
||||
|
||||
## Code Style
|
||||
- **Imports**: Standard library first, then third-party (blank line between), use named imports for clarity (e.g., `tea "github.com/charmbracelet/bubbletea"`)
|
||||
- **Formatting**: Use `gofmt`, tabs for indentation
|
||||
- **Types**: Explicit types, struct fields exported when needed for JSON/external use
|
||||
- **Naming**: CamelCase for exports, camelCase for private, descriptive names (e.g., `connectedMsg`, `fetchMenuCmd`)
|
||||
- **Error handling**: Check all errors explicitly, wrap with `fmt.Errorf("context: %w", err)` for context
|
||||
- **Comments**: Minimal, only for public APIs or complex logic
|
||||
- **Concurrency**: Use channels and goroutines for I/O operations (see `connectCmd`, `Hub.Run`)
|
||||
664
README.md
Normal file
664
README.md
Normal file
@ -0,0 +1,664 @@
|
||||
# Clink - TCP Socket-Based Order System
|
||||
|
||||
## Overview
|
||||
|
||||
Clink is a real-time order management system demonstrating TCP socket programming concepts in Go. The application consists of a TCP server that manages client connections and broadcasts order updates, and a Terminal User Interface (TUI) client that connects to the server to place orders and receive real-time updates from all connected clients.
|
||||
|
||||
**Main Topic:** Socket Programming with TCP in Go
|
||||
|
||||
---
|
||||
|
||||
## Architecture
|
||||
|
||||
### Components
|
||||
|
||||
1. **TCP Server** (`server.go`) - Multi-client socket server with broadcast capability
|
||||
2. **TUI Client** (`main.go`) - Interactive terminal client using TCP sockets
|
||||
3. **Protocol** - Custom text-based protocol over TCP
|
||||
|
||||
---
|
||||
|
||||
## Socket Programming Concepts Demonstrated
|
||||
|
||||
### 1. TCP Server Socket Creation
|
||||
|
||||
**Location:** `server.go:252-256`
|
||||
|
||||
```go
|
||||
func startTCPServer(addr string) error {
|
||||
ln, err := net.Listen("tcp", addr)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
```
|
||||
|
||||
- Uses `net.Listen()` to create a TCP listener socket
|
||||
- Binds to the specified address (default: `localhost:9000`)
|
||||
- Returns a `net.Listener` that can accept incoming connections
|
||||
|
||||
---
|
||||
|
||||
### 2. Accepting Client Connections
|
||||
|
||||
**Location:** `server.go:261-268`
|
||||
|
||||
```go
|
||||
for {
|
||||
c, err := ln.Accept()
|
||||
if err != nil {
|
||||
log.Printf("accept error: %v", err)
|
||||
continue
|
||||
}
|
||||
go handleConn(hub, c)
|
||||
}
|
||||
```
|
||||
|
||||
- `Accept()` blocks until a client connects
|
||||
- Each connection is handled in a separate goroutine
|
||||
- This enables concurrent handling of multiple clients
|
||||
|
||||
---
|
||||
|
||||
### 3. Client Socket Connection
|
||||
|
||||
**Location:** `main.go:484-493`
|
||||
|
||||
```go
|
||||
func connectCmd(addr string) tea.Cmd {
|
||||
return func() tea.Msg {
|
||||
conn, err := net.DialTimeout("tcp", addr, 3*time.Second)
|
||||
if err != nil {
|
||||
return statusMsg(fmt.Sprintf("Connect failed: %v", err))
|
||||
}
|
||||
return connectedMsg{conn: conn}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
- Uses `net.DialTimeout()` to establish TCP connection
|
||||
- Includes 3-second timeout to prevent indefinite blocking
|
||||
- Returns `net.Conn` interface for bidirectional communication
|
||||
|
||||
---
|
||||
|
||||
### 4. Buffered Reading from Socket
|
||||
|
||||
**Location:** `main.go:148-150`
|
||||
|
||||
```go
|
||||
case connectedMsg:
|
||||
m.conn = msg.conn
|
||||
m.reader = bufio.NewReader(m.conn)
|
||||
```
|
||||
|
||||
**Why Buffered Reading?**
|
||||
- Raw socket reads are byte-level and inefficient
|
||||
- `bufio.Reader` provides buffering and line-reading capabilities
|
||||
- **Critical:** Single `bufio.Reader` instance per connection prevents data corruption
|
||||
- Multiple readers on the same socket would compete for bytes
|
||||
|
||||
---
|
||||
|
||||
### 5. Reading Greeting Messages
|
||||
|
||||
**Location:** `main.go:153-159`
|
||||
|
||||
```go
|
||||
_ = m.conn.SetReadDeadline(time.Now().Add(500 * time.Millisecond))
|
||||
for i := 0; i < 2; i++ {
|
||||
if _, err := m.reader.ReadString('\n'); err != nil {
|
||||
break
|
||||
}
|
||||
}
|
||||
_ = m.conn.SetReadDeadline(time.Time{})
|
||||
```
|
||||
|
||||
- Server sends 2 greeting lines upon connection (lines 131-132 in `server.go`)
|
||||
- Client consumes these to prevent interference with protocol messages
|
||||
- **Socket Deadline:** Temporary 500ms timeout prevents indefinite blocking
|
||||
- Deadline is reset to zero (no timeout) after consuming greetings
|
||||
|
||||
---
|
||||
|
||||
### 6. Writing to Socket
|
||||
|
||||
**Location:** `main.go:506`, `main.go:544`
|
||||
|
||||
```go
|
||||
// Sending MENU request
|
||||
fmt.Fprintln(conn, "MENU")
|
||||
|
||||
// Sending ORDER request
|
||||
fmt.Fprintf(conn, "ORDER %s\n", string(b))
|
||||
```
|
||||
|
||||
**Location:** `server.go:155`, `server.go:211`
|
||||
|
||||
```go
|
||||
// Server responses
|
||||
fmt.Fprintln(c, string(b)) // MENU response
|
||||
fmt.Fprintf(c, "OK|%.2f\n", total) // ORDER response
|
||||
```
|
||||
|
||||
- `fmt.Fprintln()` and `fmt.Fprintf()` write to any `io.Writer`, including sockets
|
||||
- Newline-delimited protocol (each message ends with `\n`)
|
||||
- Text-based protocol for simplicity and debuggability
|
||||
|
||||
---
|
||||
|
||||
### 7. Socket Read Deadlines (Timeouts)
|
||||
|
||||
**Location:** `main.go:510-511`, `main.go:550-551`, `main.go:581-583`
|
||||
|
||||
```go
|
||||
// Set 3-second timeout for MENU
|
||||
_ = conn.SetReadDeadline(time.Now().Add(3 * time.Second))
|
||||
defer func() { _ = conn.SetReadDeadline(time.Time{}) }()
|
||||
|
||||
// Set 5-second timeout for ORDER
|
||||
_ = conn.SetReadDeadline(time.Now().Add(5 * time.Second))
|
||||
|
||||
// Set 100ms timeout for broadcasts (polling)
|
||||
_ = conn.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
|
||||
```
|
||||
|
||||
**Why Different Timeouts?**
|
||||
- **MENU/ORDER (3-5s):** Synchronous request-response, expect immediate reply
|
||||
- **Broadcasts (100ms):** Asynchronous polling loop, short timeout prevents blocking
|
||||
- Deadlines prevent reads from blocking forever if server stops responding
|
||||
|
||||
**Deadline vs Timeout:**
|
||||
- `SetReadDeadline()` sets an absolute time
|
||||
- After deadline expires, read returns `net.Error` with `Timeout() == true`
|
||||
|
||||
---
|
||||
|
||||
### 8. Handling Timeout Errors
|
||||
|
||||
**Location:** `main.go:585-589`
|
||||
|
||||
```go
|
||||
if err != nil {
|
||||
if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
|
||||
return broadcastMsg("") // Timeout is expected, continue polling
|
||||
}
|
||||
return statusMsg(fmt.Sprintf("Connection closed: %v", err))
|
||||
}
|
||||
```
|
||||
|
||||
- Type assertion to check if error is `net.Error`
|
||||
- Distinguish between timeout (expected) and connection failure
|
||||
- Timeouts in broadcast loop are normal behavior (polling mechanism)
|
||||
|
||||
---
|
||||
|
||||
### 9. Concurrent Socket Communication Challenge
|
||||
|
||||
**The Problem:** Race condition between synchronous requests and asynchronous broadcasts
|
||||
|
||||
**Location:** `main.go:130`, `main.go:548`, `main.go:213-215`
|
||||
|
||||
```go
|
||||
// Before ORDER: Pause broadcast listener
|
||||
m.pauseBroadcast = true
|
||||
|
||||
// Wait for broadcast listener's current read to timeout
|
||||
time.Sleep(150 * time.Millisecond)
|
||||
|
||||
// Broadcast handler: Slow down polling when paused
|
||||
if m.pauseBroadcast {
|
||||
time.Sleep(50 * time.Millisecond)
|
||||
}
|
||||
```
|
||||
|
||||
**Why This Is Needed:**
|
||||
- Single TCP socket shared between request-response and broadcast listening
|
||||
- Only one goroutine can read from socket at a time
|
||||
- Without coordination, broadcast listener might consume ORDER response
|
||||
- Solution: Coordinate reads using pause flag and timeouts
|
||||
|
||||
**Timeline Without Coordination:**
|
||||
```
|
||||
Time Action
|
||||
t=0 ORDER sent
|
||||
t=1 Broadcast listener reads "OK|9.00" (WRONG!)
|
||||
t=3000 submitOrderCmd times out (never got response)
|
||||
```
|
||||
|
||||
**Timeline With Coordination:**
|
||||
```
|
||||
Time Action
|
||||
t=0 pauseBroadcast = true
|
||||
t=0 ORDER sent
|
||||
t=150 Broadcast listener's 100ms timeout expires
|
||||
t=150 Broadcast listener sees pause, sleeps 50ms
|
||||
t=150 submitOrderCmd reads "OK|9.00" (SUCCESS!)
|
||||
t=200 Broadcast listener resumes with pause = false
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### 10. Hub Pattern for Broadcasting
|
||||
|
||||
**Location:** `server.go:36-80`
|
||||
|
||||
```go
|
||||
type Hub struct {
|
||||
mu sync.Mutex
|
||||
conns map[net.Conn]struct{}
|
||||
joinCh chan net.Conn
|
||||
leaveCh chan net.Conn
|
||||
msgCh chan broadcast
|
||||
}
|
||||
|
||||
func (h *Hub) Run() {
|
||||
for {
|
||||
select {
|
||||
case c := <-h.joinCh:
|
||||
h.mu.Lock()
|
||||
h.conns[c] = struct{}{}
|
||||
h.mu.Unlock()
|
||||
case c := <-h.leaveCh:
|
||||
h.mu.Lock()
|
||||
if _, ok := h.conns[c]; ok {
|
||||
delete(h.conns, c)
|
||||
_ = c.Close()
|
||||
}
|
||||
h.mu.Unlock()
|
||||
case msg := <-h.msgCh:
|
||||
h.mu.Lock()
|
||||
for c := range h.conns {
|
||||
if msg.exclude != nil && c == msg.exclude {
|
||||
continue
|
||||
}
|
||||
fmt.Fprintln(c, msg.text) // Write to each socket
|
||||
}
|
||||
h.mu.Unlock()
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Pattern Benefits:**
|
||||
- Centralized connection management
|
||||
- Thread-safe access to connection map using mutex
|
||||
- Fan-out broadcast to all connected sockets
|
||||
- Optional exclusion (don't echo back to sender)
|
||||
|
||||
**Broadcasting an Order:** `server.go:207-209`
|
||||
```go
|
||||
h.msgCh <- broadcast{
|
||||
text: fmt.Sprintf("[order] %s ordered %d × %s ($%.2f)",
|
||||
ord.Name, ord.Quantity, chosen.Name, total),
|
||||
}
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### 11. Per-Connection Handler
|
||||
|
||||
**Location:** `server.go:115-248`
|
||||
|
||||
```go
|
||||
func handleConn(h *Hub, c net.Conn) {
|
||||
defer func() { h.leaveCh <- c }()
|
||||
h.joinCh <- c
|
||||
|
||||
scanner := bufio.NewScanner(c)
|
||||
scanner.Buffer(make([]byte, 0, 1024), 64*1024)
|
||||
|
||||
for scanner.Scan() {
|
||||
line := strings.TrimSpace(scanner.Text())
|
||||
// Protocol handling...
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Key Points:**
|
||||
- Runs in separate goroutine per connection
|
||||
- `defer` ensures cleanup when connection closes
|
||||
- Uses `bufio.Scanner` for line-by-line reading
|
||||
- Handles multiple protocol commands: `MENU`, `ORDER`, `/name`, `/quit`
|
||||
|
||||
---
|
||||
|
||||
### 12. Connection Lifecycle
|
||||
|
||||
**Server Side:**
|
||||
1. `ln.Accept()` - Accept incoming connection (`server.go:262`)
|
||||
2. `h.joinCh <- c` - Register connection in hub (`server.go:117`)
|
||||
3. Send greeting messages (`server.go:131-132`)
|
||||
4. Process commands in loop (`server.go:141-240`)
|
||||
5. `h.leaveCh <- c` - Unregister and close (`server.go:116`)
|
||||
|
||||
**Client Side:**
|
||||
1. `net.DialTimeout()` - Establish connection (`main.go:487`)
|
||||
2. Create `bufio.Reader` (`main.go:150`)
|
||||
3. Consume greeting messages (`main.go:153-159`)
|
||||
4. Send protocol commands (`MENU`, `ORDER`)
|
||||
5. Listen for broadcasts (`main.go:570-593`)
|
||||
6. `conn.Close()` - Close on quit (`main.go:234`)
|
||||
|
||||
---
|
||||
|
||||
## Protocol Specification
|
||||
|
||||
### Text-Based Protocol over TCP
|
||||
|
||||
All messages are newline-delimited (`\n`).
|
||||
|
||||
#### Client → Server
|
||||
|
||||
**1. MENU Request**
|
||||
- Format: `MENU\n`
|
||||
- Location: `main.go:506`
|
||||
- Server handler: `server.go:149-157`
|
||||
- Response: JSON array of menu items
|
||||
|
||||
**Example:**
|
||||
```
|
||||
Client: MENU
|
||||
Server: [{"id":"latte","name":"Caffè Latte","price":4.5},...]
|
||||
```
|
||||
|
||||
**2. ORDER Request**
|
||||
- Format: `ORDER <json>\n`
|
||||
- Location: `main.go:544`
|
||||
- Server handler: `server.go:160-213`
|
||||
- Response: `OK|<total>\n`
|
||||
|
||||
**Example:**
|
||||
```
|
||||
Client: ORDER {"name":"Alice","itemId":"latte","quantity":2}
|
||||
Server: OK|9.00
|
||||
```
|
||||
|
||||
#### Server → Client (Broadcasts)
|
||||
|
||||
**1. Order Broadcast**
|
||||
- Format: `[order] <name> ordered <qty> × <item> ($<total>)\n`
|
||||
- Location: `server.go:207-209`
|
||||
- Client handler: `main.go:205-216`
|
||||
|
||||
**Example:**
|
||||
```
|
||||
[order] Alice ordered 2 × Caffè Latte ($9.00)
|
||||
```
|
||||
|
||||
**2. Join/Leave Broadcasts**
|
||||
- Format: `[join] <username> (<id>)\n` or `[leave] <username> (<id>)\n`
|
||||
- Location: `server.go:135`, `server.go:247`
|
||||
|
||||
---
|
||||
|
||||
## Application Flow
|
||||
|
||||
### Server Startup Flow
|
||||
|
||||
```
|
||||
1. main() [server.go:595]
|
||||
└─ Parse flags: --server
|
||||
|
||||
2. startTCPServer() [server.go:251]
|
||||
└─ net.Listen("tcp", addr)
|
||||
|
||||
3. hub.Run() [server.go:54]
|
||||
└─ Goroutine: Handle join/leave/broadcast channels
|
||||
|
||||
4. Accept loop [server.go:261-268]
|
||||
└─ For each connection:
|
||||
└─ go handleConn(hub, conn)
|
||||
├─ Register: hub.joinCh <- conn
|
||||
├─ Send greeting [131-132]
|
||||
├─ Process commands [141-240]
|
||||
│ ├─ MENU → JSON response [149-157]
|
||||
│ ├─ ORDER → Validate, broadcast, ack [160-213]
|
||||
│ └─ /name, /quit [216-236]
|
||||
└─ Cleanup: hub.leaveCh <- conn [116]
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### Client Startup Flow
|
||||
|
||||
```
|
||||
1. main() [main.go:595]
|
||||
└─ tea.NewProgram(initialModel(host))
|
||||
|
||||
2. Init() [main.go:88-91]
|
||||
└─ Return connectCmd(host)
|
||||
|
||||
3. connectCmd() [main.go:484-493]
|
||||
└─ net.DialTimeout("tcp", addr, 3s)
|
||||
└─ Return connectedMsg{conn}
|
||||
|
||||
4. Update(connectedMsg) [main.go:148-161]
|
||||
├─ Create bufio.Reader(conn)
|
||||
├─ Consume 2 greeting lines
|
||||
└─ Status: "Connected"
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### Order Submission Flow (Client)
|
||||
|
||||
```
|
||||
1. User presses 'n' [main.go:247]
|
||||
└─ If menu cached: Show form
|
||||
└─ Else: fetchMenuCmd()
|
||||
|
||||
2. fetchMenuCmd() [main.go:500-527]
|
||||
├─ Write: "MENU\n"
|
||||
├─ SetReadDeadline(3s)
|
||||
└─ Read JSON response
|
||||
|
||||
3. Update(menuLoadedMsg) [main.go:163-175]
|
||||
└─ Build and show order form
|
||||
|
||||
4. User fills form [name, item, quantity, confirm]
|
||||
└─ Form completed [main.go:107-135]
|
||||
|
||||
5. If confirmed:
|
||||
├─ Set pauseBroadcast = true [130]
|
||||
└─ submitOrderCmd() [534-567]
|
||||
├─ Marshal order to JSON
|
||||
├─ Write: "ORDER <json>\n"
|
||||
├─ Sleep 150ms (coordination)
|
||||
├─ SetReadDeadline(5s)
|
||||
└─ Read: "OK|<total>\n"
|
||||
|
||||
6. Update(orderSubmittedMsg) [main.go:177-203]
|
||||
├─ Set pauseBroadcast = false
|
||||
├─ Display success status
|
||||
├─ If first order:
|
||||
│ └─ Start broadcast listener
|
||||
└─ Else:
|
||||
└─ Resume broadcast listener
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### Broadcast Listening Flow (Client)
|
||||
|
||||
```
|
||||
1. Start after first order [main.go:192-194]
|
||||
└─ Set broadcastListening = true
|
||||
|
||||
2. listenForBroadcastsCmd() [main.go:570-593]
|
||||
├─ SetReadDeadline(100ms) # Poll with timeout
|
||||
├─ line, err := reader.ReadString('\n')
|
||||
└─ Three outcomes:
|
||||
├─ Timeout → Return broadcastMsg("")
|
||||
├─ Error → Connection closed
|
||||
└─ Success → Return broadcastMsg(line)
|
||||
|
||||
3. Update(broadcastMsg) [main.go:205-216]
|
||||
├─ If "[order]" prefix:
|
||||
│ └─ Append to broadcasts list (max 10)
|
||||
├─ If pauseBroadcast:
|
||||
│ └─ Sleep 50ms (slow down polling)
|
||||
└─ Restart: listenForBroadcastsCmd()
|
||||
```
|
||||
|
||||
**Polling Loop Visualization:**
|
||||
```
|
||||
Time (ms) Action
|
||||
0 SetReadDeadline(+100ms)
|
||||
0-100 Blocking read...
|
||||
100 Timeout → broadcastMsg("")
|
||||
100 Handle message, restart
|
||||
100 SetReadDeadline(+100ms)
|
||||
100-200 Blocking read...
|
||||
150 [Data arrives: "[order] Alice..."]
|
||||
150 Success → broadcastMsg("[order]...")
|
||||
150 Handle message, append to list
|
||||
150 Restart loop
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### Order Processing Flow (Server)
|
||||
|
||||
```
|
||||
1. Receive: "ORDER <json>\n" [server.go:160]
|
||||
|
||||
2. Parse and validate [server.go:161-203]
|
||||
├─ json.Unmarshal(raw, &ord)
|
||||
├─ Check: ord.Name != ""
|
||||
├─ Check: ord.Quantity > 0
|
||||
└─ Lookup: Find menuItem by ord.ItemID
|
||||
|
||||
3. Calculate total [server.go:205]
|
||||
└─ total = quantity × price
|
||||
|
||||
4. Broadcast to all clients [server.go:207-209]
|
||||
└─ hub.msgCh <- broadcast{...}
|
||||
└─ Hub writes to ALL sockets [server.go:68-77]
|
||||
└─ fmt.Fprintln(c, msg.text)
|
||||
|
||||
5. Acknowledge to sender [server.go:211]
|
||||
└─ Write: "OK|<total>\n"
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Key Socket Programming Challenges & Solutions
|
||||
|
||||
### Challenge 1: Single Socket, Dual Purpose
|
||||
|
||||
**Problem:** Same socket used for:
|
||||
- Synchronous request-response (MENU, ORDER)
|
||||
- Asynchronous broadcast receiving
|
||||
|
||||
**Solution:**
|
||||
- Broadcast listener uses short (100ms) timeouts
|
||||
- Before synchronous requests: pause broadcast polling
|
||||
- Coordination via `pauseBroadcast` flag and sleep delays
|
||||
- Locations: `main.go:130`, `main.go:548`, `main.go:213-215`
|
||||
|
||||
---
|
||||
|
||||
### Challenge 2: Buffered Reader Data Corruption
|
||||
|
||||
**Problem:** Multiple `bufio.Reader` instances on same socket would:
|
||||
- Compete for bytes from socket buffer
|
||||
- Corrupt message boundaries
|
||||
- Cause incomplete/split messages
|
||||
|
||||
**Solution:**
|
||||
- Single `bufio.Reader` created once at connection (`main.go:150`)
|
||||
- Shared across all read operations
|
||||
- Passed to all command functions
|
||||
|
||||
---
|
||||
|
||||
### Challenge 3: Greeting Message Interference
|
||||
|
||||
**Problem:** Server sends 2 greeting lines on connect
|
||||
- Would be parsed as protocol responses
|
||||
- MENU/ORDER reads would get greeting instead of response
|
||||
|
||||
**Solution:**
|
||||
- Consume greetings immediately after connect (`main.go:153-159`)
|
||||
- Use short deadline (500ms) to prevent blocking
|
||||
- Clear socket buffer before protocol starts
|
||||
|
||||
---
|
||||
|
||||
### Challenge 4: Connection Cleanup
|
||||
|
||||
**Problem:** Connections must be cleaned up on:
|
||||
- Client disconnect
|
||||
- Server shutdown
|
||||
- Network errors
|
||||
|
||||
**Solution (Server):**
|
||||
- `defer func() { h.leaveCh <- c }()` guarantees cleanup (`server.go:116`)
|
||||
- Hub centralizes close logic (`server.go:61-67`)
|
||||
|
||||
**Solution (Client):**
|
||||
- Detect "Connection closed" in status messages (`main.go:220-227`)
|
||||
- Reset all socket-related state: `conn`, `reader`, `broadcastListening`
|
||||
|
||||
---
|
||||
|
||||
## Summary
|
||||
|
||||
This application demonstrates:
|
||||
|
||||
1. **TCP Client-Server Architecture**
|
||||
- Server: `net.Listen()`, `Accept()`, per-connection goroutines
|
||||
- Client: `net.DialTimeout()`, shared connection
|
||||
|
||||
2. **Custom Text Protocol**
|
||||
- Newline-delimited messages
|
||||
- Request-response (MENU, ORDER)
|
||||
- Server-initiated broadcasts
|
||||
|
||||
3. **Concurrent Socket Communication**
|
||||
- Multiple clients handled concurrently (server)
|
||||
- Synchronous + asynchronous reads on single socket (client)
|
||||
|
||||
4. **Socket I/O Techniques**
|
||||
- Buffered reading with `bufio.Reader`
|
||||
- Read deadlines for timeouts
|
||||
- Formatted writing with `fmt.Fprintf()`
|
||||
|
||||
5. **Broadcast Pattern**
|
||||
- Hub with channels for thread-safe fan-out
|
||||
- Write to multiple sockets from single goroutine
|
||||
|
||||
6. **Real-World Challenges**
|
||||
- Read coordination between sync/async operations
|
||||
- Connection lifecycle management
|
||||
- Error handling and recovery
|
||||
|
||||
---
|
||||
|
||||
## Running the Application
|
||||
|
||||
**Start Server:**
|
||||
```bash
|
||||
go run . -server -host localhost:9000
|
||||
```
|
||||
|
||||
**Start Client(s):**
|
||||
```bash
|
||||
go run . -host localhost:9000
|
||||
```
|
||||
|
||||
**Client Controls:**
|
||||
- `n` - New order (loads menu if needed)
|
||||
- `r` - Reconnect
|
||||
- `q` - Quit
|
||||
|
||||
---
|
||||
|
||||
## File Structure
|
||||
|
||||
```
|
||||
clink/
|
||||
├── main.go # TUI client with socket operations
|
||||
├── server.go # TCP server with hub pattern
|
||||
└── README.md # This documentation
|
||||
```
|
||||
795
main.go
795
main.go
@ -2,282 +2,675 @@ package main
|
||||
|
||||
import (
|
||||
"bufio"
|
||||
|
||||
"encoding/json"
|
||||
"errors"
|
||||
"flag"
|
||||
"fmt"
|
||||
"io"
|
||||
"net"
|
||||
"regexp"
|
||||
|
||||
"strconv"
|
||||
"strings"
|
||||
"time"
|
||||
|
||||
"github.com/charmbracelet/bubbles/textarea"
|
||||
"github.com/charmbracelet/bubbles/viewport"
|
||||
tea "github.com/charmbracelet/bubbletea"
|
||||
"github.com/charmbracelet/huh"
|
||||
"github.com/charmbracelet/lipgloss"
|
||||
)
|
||||
|
||||
// colorizeLine applies ANSI styling to usernames based on 6-hex-digit id from the server.
|
||||
func colorizeLine(s string) string {
|
||||
reChat := regexp.MustCompile(`^(.+?) \(([0-9a-fA-F]{6})\):[ \t]*(.*)$`)
|
||||
if m := reChat.FindStringSubmatch(s); m != nil {
|
||||
id := strings.ToLower(m[2])
|
||||
nameStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#" + id)).Bold(true)
|
||||
name := nameStyle.Render(m[1])
|
||||
rest := strings.TrimSpace(m[3])
|
||||
return fmt.Sprintf("%s: %s", name, rest)
|
||||
}
|
||||
|
||||
reJoinLeave := regexp.MustCompile(`^\[(join|leave)\] (.+?) \(([0-9a-fA-F]{6})\)$`)
|
||||
if m := reJoinLeave.FindStringSubmatch(s); m != nil {
|
||||
id := strings.ToLower(m[3])
|
||||
nameStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#" + id)).Bold(true)
|
||||
uname := nameStyle.Render(m[2])
|
||||
return fmt.Sprintf("[%s] %s", m[1], uname)
|
||||
}
|
||||
|
||||
reRename := regexp.MustCompile(`^\[rename\] (.+?) \(([0-9a-fA-F]{6})\) -> (.+)$`)
|
||||
if m := reRename.FindStringSubmatch(s); m != nil {
|
||||
id := strings.ToLower(m[2])
|
||||
nameStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#" + id)).Bold(true)
|
||||
oldN := nameStyle.Render(m[1])
|
||||
newN := nameStyle.Render(m[3])
|
||||
return fmt.Sprintf("[rename] %s -> %s", oldN, newN)
|
||||
}
|
||||
|
||||
reWelcome := regexp.MustCompile(`^Welcome (.+?) \(([0-9a-fA-F]{6})\)$`)
|
||||
if m := reWelcome.FindStringSubmatch(s); m != nil {
|
||||
id := strings.ToLower(m[2])
|
||||
nameStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("#" + id)).Bold(true)
|
||||
uname := nameStyle.Render(m[1])
|
||||
return fmt.Sprintf("Welcome %s", uname)
|
||||
}
|
||||
|
||||
return s
|
||||
type menuItem struct {
|
||||
ID string `json:"id"`
|
||||
Name string `json:"name"`
|
||||
Price float64 `json:"price"`
|
||||
}
|
||||
|
||||
type netMsg string
|
||||
type connectedMsg struct{ conn net.Conn }
|
||||
type disconnectedMsg struct{}
|
||||
type errorMsg struct{ err error }
|
||||
// order represents the payload we submit back to the server.
|
||||
|
||||
type model struct {
|
||||
vp viewport.Model
|
||||
input textarea.Model
|
||||
messages []string
|
||||
|
||||
conn net.Conn
|
||||
server string
|
||||
// messages used by Bubble Tea
|
||||
type (
|
||||
connectedMsg struct{ conn net.Conn }
|
||||
menuLoadedMsg struct {
|
||||
items []menuItem
|
||||
err error
|
||||
}
|
||||
orderSubmittedMsg struct {
|
||||
ack string
|
||||
total float64
|
||||
err error
|
||||
}
|
||||
broadcastMsg string
|
||||
statusMsg string
|
||||
serverLineMsg string
|
||||
)
|
||||
|
||||
type FormFields struct {
|
||||
name string
|
||||
itemID string
|
||||
quantityStr string
|
||||
confirm bool
|
||||
}
|
||||
|
||||
func initialModel(serverAddr string) model {
|
||||
vp := viewport.New(80, 20)
|
||||
vp.Style = lipgloss.NewStyle().Border(lipgloss.NormalBorder()).Padding(0, 1).BorderForeground(lipgloss.Color("#bada55"))
|
||||
// model holds the TUI state.
|
||||
type model struct {
|
||||
host string
|
||||
conn net.Conn
|
||||
|
||||
ta := textarea.New()
|
||||
ta.FocusedStyle.CursorLine = lipgloss.NewStyle()
|
||||
ta.Placeholder = "Type message and press Enter..."
|
||||
ta.Focus()
|
||||
ta.Prompt = "┃ "
|
||||
ta.CharLimit = 0
|
||||
ta.SetHeight(2)
|
||||
ta.ShowLineNumbers = false
|
||||
title string
|
||||
status string
|
||||
loading bool
|
||||
err error
|
||||
lastOrder *order
|
||||
broadcasts []string
|
||||
|
||||
form *huh.Form
|
||||
formFields *FormFields
|
||||
menu []menuItem
|
||||
name string
|
||||
itemID string
|
||||
quantityStr string
|
||||
confirm bool
|
||||
|
||||
width int
|
||||
height int
|
||||
|
||||
reader *bufio.Reader
|
||||
broadcastListening bool
|
||||
pauseBroadcast bool
|
||||
}
|
||||
|
||||
// initialModel creates a base model.
|
||||
func initialModel(host string) model {
|
||||
return model{
|
||||
vp: vp,
|
||||
input: ta,
|
||||
messages: []string{},
|
||||
server: serverAddr,
|
||||
host: host,
|
||||
title: "Order Console",
|
||||
formFields: &FormFields{},
|
||||
}
|
||||
}
|
||||
|
||||
func (m model) Init() tea.Cmd {
|
||||
if m.conn != nil {
|
||||
return tea.Batch(textarea.Blink, readLineCmd(m.conn))
|
||||
}
|
||||
return tea.Batch(textarea.Blink, connectCmd(m.server))
|
||||
// Connect on startup
|
||||
return connectCmd(m.host)
|
||||
}
|
||||
|
||||
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
|
||||
var cmds []tea.Cmd
|
||||
|
||||
// If a form is active, delegate to it first.
|
||||
if m.form != nil {
|
||||
var cmd tea.Cmd
|
||||
form, cmd := m.form.Update(msg)
|
||||
|
||||
if f, ok := form.(*huh.Form); ok {
|
||||
m.form = f
|
||||
cmds = append(cmds, cmd)
|
||||
}
|
||||
|
||||
if m.form.State == huh.StateCompleted {
|
||||
// Parse and submit order if confirmed.
|
||||
qty, err := strconv.Atoi(strings.TrimSpace(m.formFields.quantityStr))
|
||||
if err != nil || qty <= 0 {
|
||||
m.err = fmt.Errorf("invalid quantity: %v", m.formFields.quantityStr)
|
||||
m.form = nil
|
||||
return m, nil
|
||||
}
|
||||
ord := &order{
|
||||
Name: strings.TrimSpace(m.formFields.name),
|
||||
ItemID: m.formFields.itemID,
|
||||
Quantity: qty,
|
||||
}
|
||||
m.lastOrder = ord
|
||||
m.form = nil
|
||||
|
||||
if m.formFields.confirm {
|
||||
if m.conn == nil {
|
||||
m.status = "Not connected. Unable to submit order."
|
||||
return m, nil
|
||||
}
|
||||
m.err = nil
|
||||
m.loading = true
|
||||
m.pauseBroadcast = true
|
||||
m.status = "Submitting order..."
|
||||
return m, submitOrderCmd(m.conn, *ord, m.reader)
|
||||
}
|
||||
m.status = "Order canceled."
|
||||
if m.broadcastListening {
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, cmd
|
||||
}
|
||||
|
||||
if m.form.State == huh.StateAborted {
|
||||
m.status = "Order form aborted."
|
||||
m.form = nil
|
||||
if m.broadcastListening {
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, cmd
|
||||
}
|
||||
|
||||
return m, tea.Batch(cmds...)
|
||||
}
|
||||
|
||||
switch msg := msg.(type) {
|
||||
case connectedMsg:
|
||||
m.conn = msg.conn
|
||||
m.reader = bufio.NewReader(m.conn)
|
||||
m.status = fmt.Sprintf("Connected to %s", m.host)
|
||||
|
||||
_ = m.conn.SetReadDeadline(time.Now().Add(500 * time.Millisecond))
|
||||
for i := 0; i < 2; i++ {
|
||||
if _, err := m.reader.ReadString('\n'); err != nil {
|
||||
break
|
||||
}
|
||||
}
|
||||
_ = m.conn.SetReadDeadline(time.Time{})
|
||||
|
||||
m.broadcastListening = true
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
|
||||
case menuLoadedMsg:
|
||||
m.loading = false
|
||||
m.pauseBroadcast = false
|
||||
if msg.err != nil {
|
||||
m.err = msg.err
|
||||
m.status = "Failed to load menu."
|
||||
if m.broadcastListening {
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
m.err = nil
|
||||
m.menu = msg.items
|
||||
m.status = "Menu loaded."
|
||||
|
||||
m.form = m.buildForm()
|
||||
if m.broadcastListening {
|
||||
return m, tea.Batch(m.form.Init(), listenForBroadcastsCmd(m.conn, m.reader))
|
||||
}
|
||||
return m, m.form.Init()
|
||||
|
||||
case orderSubmittedMsg:
|
||||
m.loading = false
|
||||
m.pauseBroadcast = false
|
||||
if msg.err != nil {
|
||||
m.err = msg.err
|
||||
m.status = "Order submission failed."
|
||||
if m.broadcastListening {
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, nil
|
||||
}
|
||||
m.err = nil
|
||||
if msg.total > 0 {
|
||||
m.status = fmt.Sprintf("Order submitted. Total: $%.2f", msg.total)
|
||||
|
||||
if !m.broadcastListening {
|
||||
m.broadcastListening = true
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
} else if msg.ack != "" {
|
||||
m.status = fmt.Sprintf("Order submitted. Server says: %s", msg.ack)
|
||||
}
|
||||
if m.broadcastListening {
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
}
|
||||
return m, nil
|
||||
|
||||
case broadcastMsg:
|
||||
msgText := string(msg)
|
||||
if msgText != "" && strings.HasPrefix(msgText, "[order]") {
|
||||
m.broadcasts = append(m.broadcasts, msgText)
|
||||
if len(m.broadcasts) > 10 {
|
||||
m.broadcasts = m.broadcasts[1:]
|
||||
}
|
||||
}
|
||||
if m.pauseBroadcast {
|
||||
return m, nil
|
||||
}
|
||||
return m, listenForBroadcastsCmd(m.conn, m.reader)
|
||||
case statusMsg:
|
||||
msgStr := string(msg)
|
||||
m.status = msgStr
|
||||
if strings.Contains(msgStr, "Connection closed") {
|
||||
if m.conn != nil {
|
||||
_ = m.conn.Close()
|
||||
m.conn = nil
|
||||
}
|
||||
m.broadcastListening = false
|
||||
m.reader = nil
|
||||
}
|
||||
return m, nil
|
||||
|
||||
case tea.KeyMsg:
|
||||
switch msg.String() {
|
||||
case "q", "ctrl+c", "esc":
|
||||
if m.conn != nil {
|
||||
_ = m.conn.Close()
|
||||
}
|
||||
return m, tea.Quit
|
||||
case "r":
|
||||
// Reconnect
|
||||
if m.conn != nil {
|
||||
_ = m.conn.Close()
|
||||
m.conn = nil
|
||||
}
|
||||
m.broadcastListening = false
|
||||
m.reader = nil
|
||||
m.status = "Reconnecting..."
|
||||
return m, connectCmd(m.host)
|
||||
case "n":
|
||||
if m.loading || m.form != nil {
|
||||
return m, nil
|
||||
}
|
||||
if m.conn == nil {
|
||||
m.status = "Not connected. Press 'r' to reconnect."
|
||||
return m, nil
|
||||
}
|
||||
m.err = nil
|
||||
if len(m.menu) > 0 {
|
||||
m.form = m.buildForm()
|
||||
return m, m.form.Init()
|
||||
}
|
||||
m.loading = true
|
||||
m.pauseBroadcast = true
|
||||
m.status = "Loading menu..."
|
||||
return m, fetchMenuCmd(m.conn, m.reader)
|
||||
}
|
||||
|
||||
case tea.WindowSizeMsg:
|
||||
m.width = msg.Width
|
||||
m.height = msg.Height
|
||||
}
|
||||
|
||||
return m, nil
|
||||
}
|
||||
|
||||
func (m model) renderHeader() string {
|
||||
titleStyle := lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("212"))
|
||||
hostStyle := lipgloss.NewStyle().Faint(true)
|
||||
|
||||
title := titleStyle.Render(m.title)
|
||||
host := hostStyle.Render(m.host)
|
||||
|
||||
header := lipgloss.JoinVertical(lipgloss.Center, title, host)
|
||||
return lipgloss.NewStyle().Width(m.width).Align(lipgloss.Center).Render(header)
|
||||
}
|
||||
|
||||
func (m model) renderLeftColumn() string {
|
||||
lines := []string{}
|
||||
|
||||
if m.loading {
|
||||
loadingText := "Loading..."
|
||||
if m.status != "" {
|
||||
loadingText = m.status
|
||||
}
|
||||
lines = append(lines, "Status: "+lipgloss.NewStyle().Foreground(lipgloss.Color("178")).Render(loadingText))
|
||||
} else if m.status != "" {
|
||||
lines = append(lines, "Status: "+m.status)
|
||||
}
|
||||
|
||||
if m.err != nil {
|
||||
lines = append(lines, lipgloss.NewStyle().Foreground(lipgloss.Color("9")).Render(fmt.Sprintf("Error: %v", m.err)))
|
||||
}
|
||||
|
||||
if m.lastOrder != nil {
|
||||
lines = append(lines, "", lipgloss.NewStyle().Bold(true).Render("Last Order:"))
|
||||
lines = append(lines, fmt.Sprintf(" Name: %s", m.lastOrder.Name))
|
||||
var label string
|
||||
for _, it := range m.menu {
|
||||
if it.ID == m.lastOrder.ItemID {
|
||||
label = it.Name
|
||||
break
|
||||
}
|
||||
}
|
||||
if label != "" {
|
||||
lines = append(lines, fmt.Sprintf(" Item: %s", label))
|
||||
} else {
|
||||
lines = append(lines, fmt.Sprintf(" Item: %s", m.lastOrder.ItemID))
|
||||
}
|
||||
lines = append(lines, fmt.Sprintf(" Quantity: %d", m.lastOrder.Quantity))
|
||||
}
|
||||
|
||||
content := lipgloss.JoinVertical(lipgloss.Left, lines...)
|
||||
return lipgloss.NewStyle().
|
||||
Width(m.width/2 - 2).
|
||||
Height(m.height - 6).
|
||||
Padding(1).
|
||||
Border(lipgloss.RoundedBorder()).
|
||||
Render(content)
|
||||
}
|
||||
|
||||
func (m model) renderRightColumn() string {
|
||||
lines := []string{}
|
||||
headerStyle := lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("212"))
|
||||
lines = append(lines, headerStyle.Render("Recent Orders:"))
|
||||
lines = append(lines, "")
|
||||
|
||||
if len(m.broadcasts) == 0 {
|
||||
lines = append(lines, lipgloss.NewStyle().Faint(true).Render("No orders yet..."))
|
||||
} else {
|
||||
bulletStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("141"))
|
||||
nameStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("86")).Bold(true)
|
||||
itemStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("117"))
|
||||
priceStyle := lipgloss.NewStyle().Foreground(lipgloss.Color("220")).Bold(true)
|
||||
|
||||
for _, b := range m.broadcasts {
|
||||
msg := strings.TrimPrefix(b, "[order] ")
|
||||
parts := strings.SplitN(msg, " ordered ", 2)
|
||||
if len(parts) == 2 {
|
||||
customer := parts[0]
|
||||
orderDetails := parts[1]
|
||||
|
||||
line := fmt.Sprintf("%s %s ordered %s",
|
||||
bulletStyle.Render("•"),
|
||||
nameStyle.Render(customer),
|
||||
itemStyle.Render(orderDetails))
|
||||
|
||||
if idx := strings.Index(orderDetails, "($"); idx != -1 {
|
||||
priceStart := idx
|
||||
priceEnd := strings.Index(orderDetails[priceStart:], ")")
|
||||
if priceEnd != -1 {
|
||||
priceEnd += priceStart + 1
|
||||
beforePrice := orderDetails[:priceStart]
|
||||
priceText := orderDetails[priceStart:priceEnd]
|
||||
|
||||
line = fmt.Sprintf("%s %s ordered %s %s",
|
||||
bulletStyle.Render("•"),
|
||||
nameStyle.Render(customer),
|
||||
itemStyle.Render(beforePrice),
|
||||
priceStyle.Render(priceText))
|
||||
}
|
||||
}
|
||||
|
||||
lines = append(lines, line)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
content := lipgloss.JoinVertical(lipgloss.Left, lines...)
|
||||
return lipgloss.NewStyle().
|
||||
Width(m.width/2 - 2).
|
||||
Height(m.height - 6).
|
||||
Padding(1).
|
||||
Border(lipgloss.RoundedBorder()).
|
||||
Render(content)
|
||||
}
|
||||
|
||||
func (m model) renderFooter() string {
|
||||
connStatus := ""
|
||||
if m.conn != nil {
|
||||
connStatus = lipgloss.NewStyle().Foreground(lipgloss.Color("10")).Render("● Connected")
|
||||
} else {
|
||||
connStatus = lipgloss.NewStyle().Foreground(lipgloss.Color("9")).Render("● Disconnected")
|
||||
}
|
||||
|
||||
controls := lipgloss.NewStyle().Faint(true).Render("n: New Order r: Reconnect q: Quit")
|
||||
|
||||
leftSide := connStatus
|
||||
rightSide := controls
|
||||
|
||||
footer := lipgloss.JoinHorizontal(lipgloss.Top,
|
||||
lipgloss.NewStyle().Width(m.width/2).Render(leftSide),
|
||||
lipgloss.NewStyle().Width(m.width/2).Align(lipgloss.Right).Render(rightSide),
|
||||
)
|
||||
|
||||
return lipgloss.NewStyle().Width(m.width).Render(footer)
|
||||
}
|
||||
|
||||
func (m model) View() string {
|
||||
if m.width == 0 || m.height == 0 {
|
||||
return "Loading..."
|
||||
}
|
||||
|
||||
header := m.renderHeader()
|
||||
|
||||
var leftCol string
|
||||
if m.form != nil {
|
||||
formView := m.form.WithHeight(m.height - 10).View()
|
||||
leftCol = lipgloss.NewStyle().
|
||||
Width(m.width/2 - 2).
|
||||
Height(m.height - 6).
|
||||
Padding(1).
|
||||
Border(lipgloss.RoundedBorder()).
|
||||
Render(formView)
|
||||
} else {
|
||||
leftCol = m.renderLeftColumn()
|
||||
}
|
||||
|
||||
rightCol := m.renderRightColumn()
|
||||
body := lipgloss.JoinHorizontal(lipgloss.Top, leftCol, rightCol)
|
||||
|
||||
footer := m.renderFooter()
|
||||
|
||||
return lipgloss.JoinVertical(lipgloss.Left,
|
||||
header,
|
||||
"",
|
||||
body,
|
||||
"",
|
||||
footer,
|
||||
)
|
||||
}
|
||||
|
||||
// buildForm constructs the order form: Input (name) -> Select (menu) -> Input (qty) -> Confirm.
|
||||
func (m *model) buildForm() *huh.Form {
|
||||
opts := make([]huh.Option[string], 0, len(m.menu))
|
||||
for _, it := range m.menu {
|
||||
opts = append(opts, huh.NewOption(fmt.Sprintf("%s - $%.2f", it.Name, it.Price), it.ID))
|
||||
}
|
||||
|
||||
// Reset bound fields for a fresh form
|
||||
m.formFields.name = ""
|
||||
m.formFields.itemID = ""
|
||||
m.formFields.quantityStr = ""
|
||||
m.formFields.confirm = false
|
||||
|
||||
f := huh.NewForm(
|
||||
huh.NewGroup(
|
||||
huh.NewInput().
|
||||
Title("Your name").
|
||||
Prompt("> ").
|
||||
Placeholder("Jane Doe").
|
||||
Value(&m.formFields.name).
|
||||
Validate(func(s string) error {
|
||||
if strings.TrimSpace(s) == "" {
|
||||
return errors.New("name is required")
|
||||
}
|
||||
return nil
|
||||
}),
|
||||
huh.NewSelect[string]().
|
||||
Title("Menu item").
|
||||
Options(opts...).
|
||||
Value(&m.formFields.itemID).
|
||||
Validate(func(v string) error {
|
||||
if v == "" {
|
||||
return errors.New("please select a menu item")
|
||||
}
|
||||
return nil
|
||||
}),
|
||||
),
|
||||
huh.NewGroup(
|
||||
huh.NewInput().
|
||||
Title("Quantity").
|
||||
Prompt("> ").
|
||||
Placeholder("1").
|
||||
Value(&m.formFields.quantityStr).
|
||||
Validate(func(s string) error {
|
||||
n, err := strconv.Atoi(strings.TrimSpace(s))
|
||||
if err != nil || n <= 0 {
|
||||
return errors.New("enter a positive integer")
|
||||
}
|
||||
return nil
|
||||
}),
|
||||
huh.NewConfirm().
|
||||
Title("Place order?").
|
||||
Affirmative("Yes").
|
||||
Negative("No").
|
||||
Value(&m.formFields.confirm),
|
||||
),
|
||||
).WithTheme(huh.ThemeBase())
|
||||
|
||||
return f
|
||||
}
|
||||
|
||||
// connectCmd connects to the TCP server.
|
||||
func connectCmd(addr string) tea.Cmd {
|
||||
return func() tea.Msg {
|
||||
conn, err := net.DialTimeout("tcp", addr, 3*time.Second)
|
||||
if err != nil {
|
||||
return netMsg(fmt.Sprintf("[error] connect: %v", err))
|
||||
return statusMsg(fmt.Sprintf("Connect failed: %v", err))
|
||||
}
|
||||
|
||||
return connectedMsg{conn: conn}
|
||||
}
|
||||
}
|
||||
|
||||
func readLineCmd(conn net.Conn) tea.Cmd {
|
||||
// fetchMenuCmd asks the server for a menu via the TCP connection.
|
||||
// Protocol (proposed):
|
||||
// - client: "MENU\n"
|
||||
// - server: single line JSON array: [{"id":"x","name":"..."}]\n
|
||||
func fetchMenuCmd(conn net.Conn, reader *bufio.Reader) tea.Cmd {
|
||||
return func() tea.Msg {
|
||||
if conn == nil {
|
||||
return disconnectedMsg{}
|
||||
if conn == nil || reader == nil {
|
||||
return menuLoadedMsg{err: errors.New("not connected")}
|
||||
}
|
||||
|
||||
reader := bufio.NewReader(conn)
|
||||
line, err := reader.ReadString('\n')
|
||||
time.Sleep(150 * time.Millisecond)
|
||||
|
||||
if _, err := fmt.Fprintln(conn, "MENU"); err != nil {
|
||||
return menuLoadedMsg{err: fmt.Errorf("send MENU: %w", err)}
|
||||
}
|
||||
|
||||
_ = conn.SetReadDeadline(time.Now().Add(3 * time.Second))
|
||||
defer func() { _ = conn.SetReadDeadline(time.Time{}) }()
|
||||
|
||||
var line string
|
||||
for {
|
||||
l, err := reader.ReadString('\n')
|
||||
if err != nil {
|
||||
if errors.Is(err, io.EOF) {
|
||||
return disconnectedMsg{}
|
||||
return menuLoadedMsg{err: fmt.Errorf("read MENU: %w", err)}
|
||||
}
|
||||
return netMsg(fmt.Sprintf("[error] read: %v", err))
|
||||
l = strings.TrimRight(l, "\r\n")
|
||||
if strings.HasPrefix(l, "[join]") || strings.HasPrefix(l, "[leave]") || strings.HasPrefix(l, "[rename]") || strings.HasPrefix(l, "[order]") {
|
||||
continue
|
||||
}
|
||||
line = l
|
||||
break
|
||||
}
|
||||
|
||||
return netMsg(strings.TrimRight(line, "\r\n"))
|
||||
if strings.HasPrefix(line, "[error]") {
|
||||
return menuLoadedMsg{err: fmt.Errorf("server: %s", line)}
|
||||
}
|
||||
|
||||
var items []menuItem
|
||||
if err := json.Unmarshal([]byte(line), &items); err != nil {
|
||||
return menuLoadedMsg{err: fmt.Errorf("invalid menu JSON: %w", err)}
|
||||
}
|
||||
return menuLoadedMsg{items: items}
|
||||
}
|
||||
}
|
||||
|
||||
func sendCmd(conn net.Conn, text string) tea.Cmd {
|
||||
// submitOrderCmd sends the order over TCP.
|
||||
// Protocol (proposed):
|
||||
// - client: "ORDER <json>\n"
|
||||
// - server: a single line acknowledgement (freeform), e.g. "OK\n"
|
||||
func submitOrderCmd(conn net.Conn, ord order, reader *bufio.Reader) tea.Cmd {
|
||||
return func() tea.Msg {
|
||||
if conn == nil {
|
||||
return netMsg("[error] not connected")
|
||||
if conn == nil || reader == nil {
|
||||
return orderSubmittedMsg{err: errors.New("not connected")}
|
||||
}
|
||||
b, err := json.Marshal(ord)
|
||||
if err != nil {
|
||||
return orderSubmittedMsg{err: fmt.Errorf("marshal order: %w", err)}
|
||||
}
|
||||
|
||||
_, err := fmt.Fprintln(conn, text)
|
||||
if err != nil {
|
||||
return netMsg(fmt.Sprintf("[error] send: %v", err))
|
||||
if _, err := fmt.Fprintf(conn, "ORDER %s\n", string(b)); err != nil {
|
||||
return orderSubmittedMsg{err: fmt.Errorf("send ORDER: %w", err)}
|
||||
}
|
||||
|
||||
time.Sleep(150 * time.Millisecond)
|
||||
|
||||
_ = conn.SetReadDeadline(time.Now().Add(5 * time.Second))
|
||||
defer func() { _ = conn.SetReadDeadline(time.Time{}) }()
|
||||
|
||||
var line string
|
||||
for {
|
||||
l, err := reader.ReadString('\n')
|
||||
if err != nil {
|
||||
return orderSubmittedMsg{err: fmt.Errorf("read ORDER ack: %w", err)}
|
||||
}
|
||||
l = strings.TrimRight(l, "\r\n")
|
||||
if strings.HasPrefix(l, "[join]") || strings.HasPrefix(l, "[leave]") || strings.HasPrefix(l, "[rename]") || strings.HasPrefix(l, "[order]") {
|
||||
continue
|
||||
}
|
||||
line = l
|
||||
break
|
||||
}
|
||||
|
||||
parts := strings.Split(line, "|")
|
||||
ack := parts[0]
|
||||
var total float64
|
||||
if len(parts) > 1 {
|
||||
if t, err := strconv.ParseFloat(parts[1], 64); err == nil {
|
||||
total = t
|
||||
}
|
||||
}
|
||||
return orderSubmittedMsg{ack: ack, total: total}
|
||||
}
|
||||
}
|
||||
|
||||
func listenForBroadcastsCmd(conn net.Conn, reader *bufio.Reader) tea.Cmd {
|
||||
return func() tea.Msg {
|
||||
defer func() {
|
||||
if r := recover(); r != nil {
|
||||
return
|
||||
}
|
||||
}()
|
||||
if conn == nil || reader == nil {
|
||||
return nil
|
||||
}
|
||||
}
|
||||
|
||||
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
|
||||
var cmds []tea.Cmd
|
||||
_ = conn.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
|
||||
line, err := reader.ReadString('\n')
|
||||
_ = conn.SetReadDeadline(time.Time{})
|
||||
|
||||
switch msg := msg.(type) {
|
||||
|
||||
case connectedMsg:
|
||||
m.conn = msg.conn
|
||||
m.messages = append(m.messages, "[connected]")
|
||||
m.refreshViewport()
|
||||
|
||||
return m, readLineCmd(m.conn)
|
||||
|
||||
case disconnectedMsg:
|
||||
m.messages = append(m.messages, "[disconnected]")
|
||||
if m.conn != nil {
|
||||
_ = m.conn.Close()
|
||||
m.conn = nil
|
||||
if err != nil {
|
||||
if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
|
||||
return broadcastMsg("")
|
||||
}
|
||||
m.refreshViewport()
|
||||
return m, nil
|
||||
|
||||
case netMsg:
|
||||
m.messages = append(m.messages, colorizeLine(string(msg)))
|
||||
m.refreshViewport()
|
||||
|
||||
if m.conn != nil && !strings.HasPrefix(string(msg), "[error] read") {
|
||||
cmds = append(cmds, readLineCmd(m.conn))
|
||||
return statusMsg(fmt.Sprintf("Connection closed: %v", err))
|
||||
}
|
||||
|
||||
case tea.KeyMsg:
|
||||
switch msg.Type {
|
||||
case tea.KeyCtrlC, tea.KeyEsc:
|
||||
if m.conn != nil {
|
||||
_ = m.conn.Close()
|
||||
return broadcastMsg(strings.TrimRight(line, "\r\n"))
|
||||
}
|
||||
return m, tea.Quit
|
||||
case tea.KeyEnter:
|
||||
text := m.input.Value()
|
||||
if text != "" {
|
||||
cmds = append(cmds, sendCmd(m.conn, text))
|
||||
m.input.SetValue("")
|
||||
m.refreshViewport()
|
||||
}
|
||||
return m, tea.Batch(cmds...)
|
||||
}
|
||||
|
||||
case tea.WindowSizeMsg:
|
||||
// Allocate space: viewport above, input below
|
||||
m.vp.Width = msg.Width
|
||||
m.vp.Height = msg.Height - 4
|
||||
m.input.SetWidth(msg.Width - 2)
|
||||
m.refreshViewport()
|
||||
}
|
||||
|
||||
// Let textarea handle remaining keys
|
||||
var cmd tea.Cmd
|
||||
m.input, cmd = m.input.Update(msg)
|
||||
if cmd != nil {
|
||||
cmds = append(cmds, cmd)
|
||||
}
|
||||
|
||||
return m, tea.Batch(cmds...)
|
||||
}
|
||||
|
||||
func (m *model) refreshViewport() {
|
||||
contentWidth := m.vp.Width - m.vp.Style.GetHorizontalFrameSize()
|
||||
|
||||
var b strings.Builder
|
||||
for _, line := range m.messages {
|
||||
wrapped := lipgloss.NewStyle().Width(contentWidth).Render(line)
|
||||
b.WriteString(wrapped)
|
||||
if !strings.HasSuffix(wrapped, "\n") {
|
||||
b.WriteString("\n")
|
||||
}
|
||||
}
|
||||
m.vp.SetContent(b.String())
|
||||
m.vp.GotoBottom()
|
||||
}
|
||||
|
||||
func (m model) View() string {
|
||||
header := lipgloss.NewStyle().Width(m.vp.Width).Padding(0, 1).Align(lipgloss.Center).Foreground(lipgloss.Color("241")).Bold(true).Render(m.server)
|
||||
return lipgloss.JoinVertical(
|
||||
lipgloss.Left,
|
||||
header,
|
||||
m.vp.View(),
|
||||
m.input.View(),
|
||||
)
|
||||
}
|
||||
|
||||
func main() {
|
||||
var (
|
||||
host string
|
||||
serverOnly bool
|
||||
menuJSON string
|
||||
)
|
||||
|
||||
flag.StringVar(&host, "host", "localhost:9000", "host:port to connect to or bind the server on")
|
||||
flag.BoolVar(&serverOnly, "server", false, "run only the server")
|
||||
flag.StringVar(&menuJSON, "menu", "", "JSON array of menu items (server mode only), e.g. '[{\"id\":\"tea\",\"name\":\"Green Tea\",\"price\":2.5}]'")
|
||||
flag.Parse()
|
||||
|
||||
if serverOnly {
|
||||
if err := startTCPServer(host); err != nil {
|
||||
var menu []menuItem
|
||||
if menuJSON != "" {
|
||||
if err := json.Unmarshal([]byte(menuJSON), &menu); err != nil {
|
||||
fmt.Printf("Invalid menu JSON: %v\n", err)
|
||||
return
|
||||
}
|
||||
}
|
||||
if err := startTCPServer(host, menu); err != nil {
|
||||
fmt.Println("Server error:", err)
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
time.Sleep(200 * time.Millisecond)
|
||||
|
||||
// Pre-connect and read initial welcome/instruction before starting UI
|
||||
var preConn net.Conn
|
||||
var preMsgs []string
|
||||
if conn, err := net.DialTimeout("tcp", host, 3*time.Second); err == nil {
|
||||
preConn = conn
|
||||
// Read up to two initial lines with a short deadline
|
||||
_ = conn.SetReadDeadline(time.Now().Add(1 * time.Second))
|
||||
r := bufio.NewReader(conn)
|
||||
for i := 0; i < 2; i++ {
|
||||
line, err := r.ReadString('\n')
|
||||
if err != nil {
|
||||
break
|
||||
}
|
||||
preMsgs = append(preMsgs, strings.TrimRight(line, "\r\n"))
|
||||
}
|
||||
_ = conn.SetReadDeadline(time.Time{})
|
||||
}
|
||||
|
||||
m := initialModel(host)
|
||||
if preConn != nil {
|
||||
m.conn = preConn
|
||||
m.messages = append(m.messages, preMsgs...)
|
||||
}
|
||||
|
||||
p := tea.NewProgram(m, tea.WithAltScreen(), tea.WithMouseCellMotion())
|
||||
p := tea.NewProgram(m, tea.WithAltScreen())
|
||||
if _, err := p.Run(); err != nil {
|
||||
fmt.Println("Error:", err)
|
||||
fmt.Println("error:", err)
|
||||
}
|
||||
}
|
||||
|
||||
95
server.go
95
server.go
@ -2,15 +2,32 @@ package main
|
||||
|
||||
import (
|
||||
"bufio"
|
||||
"encoding/json"
|
||||
"fmt"
|
||||
"log"
|
||||
"net"
|
||||
"strconv"
|
||||
"strings"
|
||||
"sync"
|
||||
|
||||
gonanoid "github.com/matoous/go-nanoid/v2"
|
||||
)
|
||||
|
||||
var defaultMenu = []menuItem{
|
||||
{ID: "latte", Name: "Caffè Latte", Price: 4.50},
|
||||
{ID: "cap", Name: "Cappuccino", Price: 4.00},
|
||||
{ID: "esp", Name: "Espresso", Price: 3.00},
|
||||
}
|
||||
|
||||
var serverMenu []menuItem
|
||||
|
||||
// order is the structure the server expects for ORDER.
|
||||
type order struct {
|
||||
Name string `json:"name"`
|
||||
ItemID string `json:"itemId"`
|
||||
Quantity int `json:"quantity"`
|
||||
}
|
||||
|
||||
// broadcast represents a line to send to all connections with the ability
|
||||
// to exclude a single connection (e.g., exclude self on join).
|
||||
type broadcast struct {
|
||||
@ -129,7 +146,75 @@ func handleConn(h *Hub, c net.Conn) {
|
||||
continue
|
||||
}
|
||||
|
||||
// Commands
|
||||
// New protocol commands:
|
||||
// MENU -> server returns single-line JSON array of menuItem
|
||||
if strings.EqualFold(line, "MENU") {
|
||||
b, err := json.Marshal(serverMenu)
|
||||
if err != nil {
|
||||
fmt.Fprintln(c, `[error] failed to encode menu`)
|
||||
continue
|
||||
}
|
||||
fmt.Fprintln(c, string(b))
|
||||
continue
|
||||
}
|
||||
|
||||
// ORDER <json> -> server validates and replies with a single-line ack
|
||||
if strings.HasPrefix(line, "ORDER") {
|
||||
raw := strings.TrimSpace(line[len("ORDER"):])
|
||||
var ord order
|
||||
if err := json.Unmarshal([]byte(raw), &ord); err != nil {
|
||||
fmt.Fprintln(c, "[error] invalid order json")
|
||||
continue
|
||||
}
|
||||
ord.Name = strings.TrimSpace(ord.Name)
|
||||
log.Printf("ORDER parsed: name=%q itemId=%q qty=%d", ord.Name, ord.ItemID, ord.Quantity)
|
||||
if ord.Name == "" {
|
||||
fmt.Fprintln(c, "[error] missing name")
|
||||
continue
|
||||
}
|
||||
// Fallback handling: accept numeric strings or floats for quantity
|
||||
if ord.Quantity <= 0 {
|
||||
var generic map[string]any
|
||||
if err := json.Unmarshal([]byte(raw), &generic); err == nil {
|
||||
if v, ok := generic["quantity"]; ok {
|
||||
switch t := v.(type) {
|
||||
case string:
|
||||
if n, err := strconv.Atoi(strings.TrimSpace(t)); err == nil {
|
||||
ord.Quantity = n
|
||||
}
|
||||
case float64:
|
||||
ord.Quantity = int(t)
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
if ord.Quantity <= 0 {
|
||||
fmt.Fprintln(c, "[error] invalid quantity")
|
||||
continue
|
||||
}
|
||||
var chosen *menuItem
|
||||
for i := range serverMenu {
|
||||
if serverMenu[i].ID == ord.ItemID {
|
||||
chosen = &serverMenu[i]
|
||||
break
|
||||
}
|
||||
}
|
||||
if chosen == nil {
|
||||
fmt.Fprintln(c, "[error] unknown item")
|
||||
continue
|
||||
}
|
||||
|
||||
total := float64(ord.Quantity) * chosen.Price
|
||||
|
||||
h.msgCh <- broadcast{
|
||||
text: fmt.Sprintf("[order] %s ordered %d × %s ($%.2f)", ord.Name, ord.Quantity, chosen.Name, total),
|
||||
}
|
||||
|
||||
fmt.Fprintf(c, "OK|%.2f\n", total)
|
||||
continue
|
||||
}
|
||||
|
||||
// Chat commands
|
||||
if line == "/quit" {
|
||||
break // unified leave handling below
|
||||
}
|
||||
@ -165,12 +250,18 @@ func handleConn(h *Hub, c net.Conn) {
|
||||
}
|
||||
|
||||
// startTCPServer starts a TCP chat server and never returns unless an error occurs.
|
||||
func startTCPServer(addr string) error {
|
||||
func startTCPServer(addr string, menu []menuItem) error {
|
||||
if len(menu) == 0 {
|
||||
menu = defaultMenu
|
||||
}
|
||||
serverMenu = menu
|
||||
|
||||
ln, err := net.Listen("tcp", addr)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
log.Printf("TCP chat server listening on %s", ln.Addr())
|
||||
log.Printf("Menu items: %d", len(serverMenu))
|
||||
|
||||
hub := NewHub()
|
||||
go hub.Run()
|
||||
|
||||
Loading…
Reference in New Issue
Block a user