2 files changed, 160 insertions, 0 deletions
diff --git a/mt4/client.go b/mt4/client.go
new file mode 100644
index 0000000..8a5f388
--- /dev/null
+++ b/mt4/client.go
@@ -0,0 +1,115 @@
+package mt4
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"go.popov.link/metatrader4/internal/conn"
+	"go.popov.link/metatrader4/internal/proto"
+)
+
+// Client provides access to a MetaTrader4 server.
+type Client struct {
+	addr         string
+	port         int
+	dialTimeout  time.Duration
+	readTimeout  time.Duration
+	writeTimeout time.Duration
+	autoClose    bool
+	dialer       net.Dialer
+	c            *conn.Conn
+}
+
+// Option configures the Client.
+type Option func(*Client)
+
+// WithDialTimeout sets timeout for establishing connections.
+func WithDialTimeout(d time.Duration) Option { return func(c *Client) { c.dialTimeout = d } }
+
+// WithReadTimeout sets timeout for reading responses.
+func WithReadTimeout(d time.Duration) Option { return func(c *Client) { c.readTimeout = d } }
+
+// WithWriteTimeout sets timeout for writing requests.
+func WithWriteTimeout(d time.Duration) Option { return func(c *Client) { c.writeTimeout = d } }
+
+// WithAutoClose enables or disables automatic connection close after Execute.
+func WithAutoClose(b bool) Option { return func(c *Client) { c.autoClose = b } }
+
+// NewClient creates a new Client with optional configuration.
+func NewClient(addr string, port int, opts ...Option) *Client {
+	cl := &Client{
+		addr:         addr,
+		port:         port,
+		dialTimeout:  5 * time.Second,
+		readTimeout:  5 * time.Second,
+		writeTimeout: 5 * time.Second,
+		autoClose:    true,
+	}
+	for _, o := range opts {
+		o(cl)
+	}
+	return cl
+}
+
+// Connect establishes connection to the MT4 server if not already connected.
+func (c *Client) Connect(ctx context.Context) error {
+	if c.c != nil {
+		return nil
+	}
+	address := fmt.Sprintf("%s:%d", c.addr, c.port)
+	cn, err := conn.Dial(ctx, address, c.dialTimeout)
+	if err != nil {
+		return err
+	}
+	c.c = cn
+	return nil
+}
+
+// Close closes underlying connection.
+func (c *Client) Close() error {
+	if c.c == nil {
+		return nil
+	}
+	err := c.c.Close()
+	c.c = nil
+	return err
+}
+
+// Execute sends command with params to the server and returns decoded response.
+func (c *Client) Execute(ctx context.Context, command string, params map[string]string) (string, error) {
+	if err := c.Connect(ctx); err != nil {
+		return "", fmt.Errorf("connect: %w", err)
+	}
+
+	encoded, err := proto.EncodeParams(params)
+	if err != nil {
+		if c.autoClose {
+			c.Close()
+		}
+		return "", err
+	}
+	req := proto.BuildRequest(command, encoded, c.autoClose)
+
+	if err := c.c.Send(ctx, req, c.writeTimeout); err != nil {
+		if c.autoClose {
+			c.Close()
+		}
+		return "", fmt.Errorf("send: %w", err)
+	}
+
+	respBytes, err := c.c.Receive(ctx, c.readTimeout)
+	if c.autoClose {
+		c.Close()
+	}
+	if err != nil {
+		return "", fmt.Errorf("receive: %w", err)
+	}
+
+	resp, err := proto.DecodeResponse(string(respBytes))
+	if err != nil {
+		return "", err
+	}
+	return resp, nil
+}
diff --git a/mt4/client_test.go b/mt4/client_test.go
new file mode 100644
index 0000000..9644c9a
--- /dev/null
+++ b/mt4/client_test.go
@@ -0,0 +1,45 @@
+package mt4
+
+import (
+	"context"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	ic "go.popov.link/metatrader4/internal/conn"
+	"go.popov.link/metatrader4/internal/proto"
+)
+
+// mockServer returns net.Pipe connections with server writing resp to client.
+func mockServer(response string) (net.Conn, net.Conn) {
+	server, client := net.Pipe()
+	go func() {
+		defer server.Close()
+		buf := make([]byte, 1024)
+		server.Read(buf) // read request ignoring
+		server.Write([]byte(response))
+	}()
+	return client, server
+}
+
+func TestClientExecute(t *testing.T) {
+	reqParams := map[string]string{"A": "1"}
+	encoded, err := proto.EncodeParams(reqParams)
+	if err != nil {
+		t.Fatalf("encode params: %v", err)
+	}
+	resp := encoded
+	clientConn, _ := mockServer(resp)
+
+	c := &Client{addr: "", port: 0, autoClose: true, readTimeout: time.Second, writeTimeout: time.Second, dialTimeout: time.Second}
+	c.c = ic.FromNetConn(clientConn)
+
+	res, err := c.Execute(context.Background(), "CMD", reqParams)
+	if err != nil {
+		t.Fatalf("execute: %v", err)
+	}
+	if !strings.Contains(res, "1") {
+		t.Fatalf("unexpected response %q", res)
+	}
+}