feat: init go project

internal/app/app.go

@@ -0,0 +1,39 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+type Options struct {
+	ConfigPath string
+	Stdout     io.Writer
+}
+
+func Run(ctx context.Context, opts Options) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
+	if opts.ConfigPath == "" {
+		return errors.New("config path is required")
+	}
+
+	if opts.Stdout == nil {
+		opts.Stdout = io.Discard
+	}
+
+	if _, err := os.Stat(opts.ConfigPath); err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("config file %q does not exist; copy config.example.yaml to config.yaml and fill credentials", opts.ConfigPath)
+		}
+
+		return fmt.Errorf("check config file %q: %w", opts.ConfigPath, err)
+	}
+
+	fmt.Fprintf(opts.Stdout, "overnight trading bot initialized with config %q\n", opts.ConfigPath)
+	return nil
+}

internal/app/app_test.go

@@ -0,0 +1,51 @@
+package app
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestRunRequiresConfigPath(t *testing.T) {
+	err := Run(context.Background(), Options{})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+
+	if !strings.Contains(err.Error(), "config path is required") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestRunReportsMissingConfig(t *testing.T) {
+	err := Run(context.Background(), Options{ConfigPath: "missing.yaml"})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+
+	if !strings.Contains(err.Error(), "does not exist") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestRunUsesExistingConfig(t *testing.T) {
+	touch := t.TempDir() + "/config.yaml"
+	if err := os.WriteFile(touch, []byte("instruments: []\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	var stdout bytes.Buffer
+	err := Run(context.Background(), Options{
+		ConfigPath: touch,
+		Stdout:     &stdout,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !strings.Contains(stdout.String(), "initialized") {
+		t.Fatalf("unexpected stdout: %q", stdout.String())
+	}
+}