do a few

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)
+	}
+}