Add message IDs, transport interface, client package, extract protocol headers

lib/client/client.go

@@ -0,0 +1,90 @@
+package client
+
+import (
+	"fmt"
+	"sync/atomic"
+	"time"
+
+	"github.com/theater/picomap/lib/halfsiphash"
+	"github.com/theater/picomap/lib/msgpack"
+	"github.com/theater/picomap/lib/transport"
+)
+
+var HashKey = [8]byte{}
+
+type Client struct {
+	transport transport.Transport
+	timeout   time.Duration
+	nextID    atomic.Uint32
+}
+
+func New(t transport.Transport, timeout time.Duration) *Client {
+	return &Client{transport: t, timeout: timeout}
+}
+
+func (c *Client) Close() error {
+	return c.transport.Close()
+}
+
+func (c *Client) send(msg any) (uint32, error) {
+	id := c.nextID.Add(1)
+	payload, err := msgpack.Marshal(msg)
+	if err != nil {
+		return 0, fmt.Errorf("encode inner: %w", err)
+	}
+	checksum := halfsiphash.Sum32(payload, HashKey)
+	env := Envelope{MessageID: id, Checksum: checksum, Payload: payload}
+	data, err := msgpack.Marshal(&env)
+	if err != nil {
+		return 0, fmt.Errorf("encode envelope: %w", err)
+	}
+	return id, c.transport.Send(data)
+}
+
+func (c *Client) receive(expectedID uint32) (any, error) {
+	data, err := c.transport.Receive(c.timeout)
+	if err != nil {
+		return nil, fmt.Errorf("receive: %w", err)
+	}
+	if len(data) == 0 {
+		return nil, fmt.Errorf("no response")
+	}
+	var env Envelope
+	if err := msgpack.Unmarshal(data, &env); err != nil {
+		return nil, fmt.Errorf("decode envelope: %w", err)
+	}
+	if env.MessageID != expectedID {
+		return nil, fmt.Errorf("message id mismatch: got %d, want %d", env.MessageID, expectedID)
+	}
+	expected := halfsiphash.Sum32(env.Payload, HashKey)
+	if env.Checksum != expected {
+		return nil, fmt.Errorf("checksum mismatch: got %08x, want %08x", env.Checksum, expected)
+	}
+	var inner any
+	if err := msgpack.Unmarshal(env.Payload, &inner); err != nil {
+		return nil, fmt.Errorf("decode inner: %w", err)
+	}
+	if devErr, ok := inner.(*DeviceError); ok {
+		return nil, devErr
+	}
+	return inner, nil
+}
+
+func (c *Client) roundTrip(req any) (any, error) {
+	id, err := c.send(req)
+	if err != nil {
+		return nil, err
+	}
+	return c.receive(id)
+}
+
+func (c *Client) BOOTSEL() error {
+	resp, err := c.roundTrip(&RequestBOOTSEL{})
+	if err != nil {
+		return err
+	}
+	if _, ok := resp.(*ResponseBOOTSEL); !ok {
+		return fmt.Errorf("unexpected response: %T", resp)
+	}
+	return nil
+}