do a few

.gitignore

@@ -0,0 +1,2 @@
+.gocache
+protohacking

Justfile

@@ -0,0 +1,19 @@
+# this is my deploy script, u dont need to worry abt this
+
+# if ur wondering im on an arm macbook so when i deploy
+# i need to compile to amd64, so i just do it in a docker container
+build:
+	docker run \
+		-v "$(pwd):/src" \
+		--platform linux/amd64 \
+		--rm \
+		-w /src \
+		golang:1.24-alpine \
+		/src/build.sh
+purge-remote:
+	ssh redbox "sudo rm /usr/local/bin/protohacking || true"
+upload:
+	dd if=protohacking | ssh redbox "sudo dd of=/usr/local/bin/protohacking && sudo chmod 755 /usr/local/bin/protohacking"
+push: build purge-remote upload
+start-remote: push
+	ssh redbox "protohacking"

build.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env ash
+GOCACHE=/src/.gocache go build -o protohacking -ldflags "-s -w" .

cmd/budgetchat.go

@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"git.red-panda.pet/pandaware/protohacking/x/budgetchat"
+	"github.com/spf13/cobra"
+)
+
+var budgetChat = &cobra.Command{
+	Use:     "budgetchat",
+	Aliases: []string{"p3"},
+	Short:   "Problem 3: Budget Chat",
+	Run: func(cmd *cobra.Command, args []string) {
+		runServer(budgetchat.New)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(budgetChat)
+}

cmd/meanstoanend.go

@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"git.red-panda.pet/pandaware/protohacking/x/meanstoanend"
+	"github.com/spf13/cobra"
+)
+
+var meansToAnEnd = &cobra.Command{
+	Use:     "meanstoanend",
+	Aliases: []string{"p2"},
+	Short:   "Problem 2: Means to an End",
+	Run: func(cmd *cobra.Command, args []string) {
+		runServer(meanstoanend.New)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(meansToAnEnd)
+}

cmd/root.go

@@ -0,0 +1,37 @@
+package cmd
+
+import (
+	"log"
+	"net"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	ip    net.IP
+	port  uint16
+	proto string
+	v6    bool
+)
+
+var rootCmd = &cobra.Command{
+	Use:   "protohacking",
+	Short: "Protohackers challenge servers",
+	Run: func(cmd *cobra.Command, args []string) {
+		cmd.Help()
+	},
+}
+
+func init() {
+	pflags := rootCmd.PersistentFlags()
+	pflags.Uint16VarP(&port, "port", "p", 8088, "Port to TCP listen on")
+	pflags.IPVarP(&ip, "ip", "i", net.IPv6unspecified, "Address to listen on")
+	pflags.BoolVarP(&v6, "v6", "6", true, "Whether to use IPv6")
+	pflags.StringVar(&proto, "proto", "tcp", "Either tcp or udp")
+}
+
+func Execute() {
+	if err := rootCmd.Execute(); err != nil {
+		log.Fatal("fatal error", "err", err)
+	}
+}

cmd/smoke-test.go

@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"git.red-panda.pet/pandaware/protohacking/x/smoketest"
+	"github.com/spf13/cobra"
+)
+
+var smokeTest = &cobra.Command{
+	Use:     "smoketest",
+	Aliases: []string{"p0"},
+	Short:   "Problem 0: Smoke Test",
+	Run: func(cmd *cobra.Command, args []string) {
+		runServer(smoketest.New)
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(smokeTest)
+}

cmd/util.go

@@ -0,0 +1,37 @@
+package cmd
+
+import (
+	"net"
+	"net/netip"
+
+	"github.com/charmbracelet/log"
+)
+
+func runServer(server func(net.Listener) error) {
+	if proto != "tcp" && proto != "udp" {
+		log.Fatal("unsupported protocol, must be either tcp or udp")
+	}
+
+	if v6 {
+		proto += "6"
+	}
+
+	addr, ok := netip.AddrFromSlice(ip)
+	if !ok {
+		log.Fatal("invalid ip")
+	}
+
+	ap := netip.AddrPortFrom(addr, port)
+
+	listener, err := net.Listen(proto, ap.String())
+	if err != nil {
+		log.Fatal("unable to listen", "err", err)
+	}
+
+	log.Info("starting server", "proto", proto, "ip", ip, "port", port)
+
+	err = server(listener)
+	if err != nil {
+		log.Fatal("error while handling connections", "err", err)
+	}
+}

go.mod

@@ -1,3 +1,28 @@
-module git.red-panda.pet/red/protohacking
+module git.red-panda.pet/pandaware/protohacking
 
 go 1.24.3
+
+require (
+	github.com/charmbracelet/log v0.4.2
+	github.com/spf13/cobra v1.9.1
+)
+
+require (
+	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
+	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
+	github.com/charmbracelet/lipgloss v1.1.0 // indirect
+	github.com/charmbracelet/x/ansi v0.8.0 // indirect
+	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
+	github.com/charmbracelet/x/term v0.2.1 // indirect
+	github.com/go-logfmt/logfmt v0.6.0 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-runewidth v0.0.16 // indirect
+	github.com/muesli/termenv v0.16.0 // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/spf13/pflag v1.0.6 // indirect
+	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
+	golang.org/x/exp v0.0.0-20231006140011-7918f672742d // indirect
+	golang.org/x/sys v0.30.0 // indirect
+)

go.sum

@@ -0,0 +1,51 @@
+github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
+github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
+github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc h1:4pZI35227imm7yK2bGPcfpFEmuY1gc2YSTShr4iJBfs=
+github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc/go.mod h1:X4/0JoqgTIPSFcRA/P6INZzIuyqdFY5rm8tb41s9okk=
+github.com/charmbracelet/lipgloss v1.1.0 h1:vYXsiLHVkK7fp74RkV7b2kq9+zDLoEU4MZoFqR/noCY=
+github.com/charmbracelet/lipgloss v1.1.0/go.mod h1:/6Q8FR2o+kj8rz4Dq0zQc3vYf7X+B0binUUBwA0aL30=
+github.com/charmbracelet/log v0.4.2 h1:hYt8Qj6a8yLnvR+h7MwsJv/XvmBJXiueUcI3cIxsyig=
+github.com/charmbracelet/log v0.4.2/go.mod h1:qifHGX/tc7eluv2R6pWIpyHDDrrb/AG71Pf2ysQu5nw=
+github.com/charmbracelet/x/ansi v0.8.0 h1:9GTq3xq9caJW8ZrBTe0LIe2fvfLR/bYXKTx2llXn7xE=
+github.com/charmbracelet/x/ansi v0.8.0/go.mod h1:wdYl/ONOLHLIVmQaxbIYEC/cRKOQyjTkowiI4blgS9Q=
+github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd h1:vy0GVL4jeHEwG5YOXDmi86oYw2yuYUGqz6a8sLwg0X8=
+github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd/go.mod h1:xe0nKWGd3eJgtqZRaN9RjMtK7xUYchjzPr7q6kcvCCs=
+github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
+github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
+github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-logfmt/logfmt v0.6.0 h1:wGYYu3uicYdqXVgoYbvnkrPVXkuLM1p1ifugDMEdRi4=
+github.com/go-logfmt/logfmt v0.6.0/go.mod h1:WYhtIu8zTZfxdn5+rREduYbwxfcBr/Vr6KEVveWlfTs=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
+github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
+github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/muesli/termenv v0.16.0 h1:S5AlUN9dENB57rsbnkPyfdGuWIlkmzJjbFf0Tf5FWUc=
+github.com/muesli/termenv v0.16.0/go.mod h1:ZRfOIKPFDYQoDFF4Olj7/QJbW60Ol/kL1pU3VfY/Cnk=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
+github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.9.1 h1:CXSaggrXdbHK9CF+8ywj8Amf7PBRmPCOJugH954Nnlo=
+github.com/spf13/cobra v1.9.1/go.mod h1:nDyEzZ8ogv936Cinf6g1RU9MRY64Ir93oCnqb9wxYW0=
+github.com/spf13/pflag v1.0.6 h1:jFzHGLGAlb3ruxLB8MhbI6A8+AQX/2eW4qeyNZXNp2o=
+github.com/spf13/pflag v1.0.6/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavMF/ppJZNG9ZpyihvCd0w101no=
+github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -0,0 +1,7 @@
+package main
+
+import "git.red-panda.pet/pandaware/protohacking/cmd"
+
+func main() {
+	cmd.Execute()
+}

x/budgetchat/server.go

@@ -0,0 +1,250 @@
+package budgetchat
+
+import (
+	"bufio"
+	"errors"
+	"net"
+	"strings"
+	"sync"
+
+	"github.com/charmbracelet/log"
+)
+
+func isGoodAscii(str string) bool {
+	// we disallow anything outside the printable ascii range
+	// that means no control characters
+	for _, c := range str {
+		if c < ' ' || c > '~' {
+			return false
+		}
+	}
+
+	return true
+}
+
+type client struct {
+	id     uint
+	name   string
+	conn   net.Conn
+	reader *bufio.Reader
+	bad    bool
+}
+
+func (c *client) read() (string, error) {
+	// get the client's name
+	line, err := c.reader.ReadString('\n')
+	if err != nil {
+		log.Error("unable to read name from client", "err", err)
+		c.conn.Close()
+		return "", err
+	}
+
+	return line[:len(line)-1], nil
+}
+
+func (c *client) send(msg string) error {
+	if c.bad {
+		log.Warn("not sending to bad client", "remote", c.conn.RemoteAddr())
+		return errors.New("trying to send to a bad client")
+	}
+
+	_, err := c.conn.Write([]byte(msg))
+	if err != nil {
+		c.bad = true
+		log.Warn("marking client as bad", "err", err)
+		c.conn.Close()
+		return err
+	}
+
+	return nil
+}
+
+type room struct {
+	inc     uint
+	lock    *sync.RWMutex
+	clients []*client
+}
+
+func (r *room) whoishere() string {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	builder := new(strings.Builder)
+	builder.WriteString("* Currently online: ")
+	if len(r.clients) == 0 {
+		log.Info("nobody is here!")
+		builder.WriteString("nobody!\n")
+		return builder.String()
+	}
+
+	for i, client := range r.clients {
+		if client == nil {
+			continue
+		}
+
+		builder.WriteString(client.name)
+		if i != len(r.clients) {
+			builder.WriteString(", ")
+		}
+	}
+
+	builder.WriteRune('\n')
+	return builder.String()
+}
+
+func (r *room) leave(client *client) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	leaveMsg := "* " + client.name + " went offline!\n"
+
+	// loop over the current clients, saving the index of the one we're removing
+	// and messaging everyone else that they left
+	removable := []int{}
+	for i, c := range r.clients {
+		if c.bad || c.id == client.id {
+			removable = append(removable, i)
+		} else {
+			c.send(leaveMsg)
+		}
+	}
+
+	// remove the client who left and any bad connections
+	for _, index := range removable {
+		r.clients[index] = r.clients[len(r.clients)-1]
+		r.clients = r.clients[:len(r.clients)-1]
+	}
+}
+
+func (r *room) addClient(client *client) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	client.id = r.inc
+	r.inc += 1
+	r.clients = append(r.clients, client)
+}
+
+func (r *room) join(conn net.Conn) {
+	log := log.Default().WithPrefix(conn.RemoteAddr().String())
+
+	log.Info("client connecting")
+	client := new(client)
+	client.conn = conn
+	client.reader = bufio.NewReader(conn)
+	client.bad = false
+
+	// start by asking for a name
+	err := client.send("* Welcome, what's your name?\n")
+	if err != nil {
+		log.Warn("kicking client: unable to write welcome", "err", err)
+		conn.Close()
+		return
+	}
+
+	// get the client's name
+	name, err := client.read()
+	if err != nil {
+		log.Warn("kicking client: unable to read name", "err", err)
+		return
+	}
+
+	// check to make sure the name is ok
+	if len(name) > 64 {
+		log.Warn("kicking client: name too long")
+		client.send("* You've been kicked: name too long\n")
+		conn.Close()
+		return
+	}
+
+	if !isGoodAscii(name) {
+		log.Warn("kicking client: name contains illegal characters")
+		client.send("* You've been kicked: name contains illegal characters\n")
+		conn.Close()
+		return
+	}
+
+	// establish the name
+	client.name = name
+	log.Info("name established", "name", client.name)
+
+	log.Info("sending room membership")
+	err = client.send(r.whoishere())
+	if err != nil {
+
+	}
+
+	// announce the new client
+	joinMsg := "* " + client.name + " is now online\n"
+	for _, c := range r.clients {
+		c.send(joinMsg)
+	}
+
+	// add the client to the room
+	r.addClient(client)
+
+	log.Info("assigned id", "id", client.id)
+
+	// start message loop
+	for {
+		line, err := client.read()
+		if err != nil {
+			break
+		}
+
+		err = r.message(client, line)
+		// if they send a bad message we tell them and kick them
+		if err != nil {
+			log.Warn("kicking client: bad message", "err", err)
+			client.send("* You've been kicked: " + err.Error() + "\n")
+			break
+		}
+	}
+
+	r.leave(client)
+
+	return
+}
+
+func (r *room) message(from *client, msg string) error {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	if len(msg) > 1000 {
+		return errors.New("message too long")
+	}
+
+	if !isGoodAscii(msg) {
+		return errors.New("message contains illegal characters")
+	}
+
+	out := "[" + from.name + "] " + msg + "\n"
+
+	for _, client := range r.clients {
+		if client == nil {
+			continue
+		}
+
+		if client.id == from.id {
+			continue
+		}
+
+		client.send(out)
+	}
+
+	return nil
+}
+
+func New(listener net.Listener) error {
+	room := new(room)
+	room.lock = new(sync.RWMutex)
+	room.clients = []*client{}
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			return err
+		}
+		go room.join(conn)
+	}
+}

x/meanstoanend/server.go

@@ -0,0 +1,106 @@
+package meanstoanend
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+	"net"
+
+	"github.com/charmbracelet/log"
+)
+
+type message struct {
+	a int32
+	b int32
+}
+
+type client struct {
+	conn   net.Conn
+	prices map[int32]int32
+	log    *log.Logger
+	buf    []byte
+}
+
+func (c *client) handleMessage() error {
+	_, err := io.ReadFull(c.conn, c.buf)
+	if err != nil {
+		return err
+	}
+
+	msg := new(message)
+
+	_, err = binary.Decode(c.buf[1:5], binary.BigEndian, &msg.a)
+	if err != nil {
+		return err
+	}
+
+	_, err = binary.Decode(c.buf[5:], binary.BigEndian, &msg.b)
+	if err != nil {
+		return err
+	}
+
+	switch c.buf[0] {
+	case 'I':
+		c.prices[msg.a] = msg.b
+	case 'Q':
+		var i int64
+		var mean int64
+
+		for k, v := range c.prices {
+			if k >= msg.a && k <= msg.b {
+				mean += int64(v)
+				i += 1
+			}
+		}
+
+		if i > 0 {
+			mean /= i
+		}
+
+		binary.Write(c.conn, binary.BigEndian, int32(mean))
+	default:
+		c.conn.Close()
+		return errors.New("bad message")
+	}
+
+	return nil
+}
+
+func acceptConn(conn net.Conn) {
+	log.Info("accepting connection", "remote", conn.RemoteAddr())
+
+	var err error
+
+	c := new(client)
+	c.log = log.Default().WithPrefix(conn.RemoteAddr().String())
+
+	c.buf = make([]byte, 9)
+	c.conn = conn
+	c.prices = map[int32]int32{}
+
+	defer c.conn.Close()
+
+	for {
+		c.log.Debug("waiting for message", "remote", conn.RemoteAddr())
+		err = c.handleMessage()
+		if err != nil {
+			if err != io.EOF {
+				c.log.Error("unable to read data", "err", err)
+			}
+			break
+		}
+	}
+
+	c.log.Info("released connection")
+}
+
+func New(listener net.Listener) error {
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			return err
+		}
+
+		go acceptConn(conn)
+	}
+}

x/smoketest/server.go

@@ -0,0 +1,32 @@
+package smoketest
+
+import (
+	"bytes"
+	"io"
+	"net"
+)
+
+func handleConn(conn net.Conn) error {
+	buf := &bytes.Buffer{}
+
+	_, err := buf.ReadFrom(conn)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(conn, buf)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func New(listener net.Listener) error {
+	for {
+		conn, err := listener.Accept()
+		if err == nil {
+			go handleConn(conn)
+		}
+	}
+}