Add "update" command

README.md

@@ -23,6 +23,16 @@ make build
 cp bin/bwai ~/.local/bin/
 ```
 
+## Update
+
+To update `bwai` to the latest release:
+
+```sh
+bwai update
+```
+
+This downloads the latest binary from [GitHub releases](https://github.com/umago/bubblewrap-ai/releases), verifies its SHA-256 digest, and replaces the running binary in-place.
+
 ## Usage
 
 Run `bwai` from inside the project directory you want to give the agent access to:

cmd/bwai/main.go

@@ -11,6 +11,16 @@ import (
 )
 
 func main() {
+	// Subcommand dispatch (before flag parsing to avoid flag conflicts)
+	if len(os.Args) > 1 && os.Args[1] == "update" {
+		fs := flag.NewFlagSet("update", flag.ExitOnError)
+		if err := fs.Parse(os.Args[2:]); err != nil {
+			os.Exit(1)
+		}
+		runUpdate()
+		return
+	}
+
 	versionFlag := flag.Bool("version", false, "Print version and exit")
 	dumpConfig := flag.Bool("dump-config", false, "Print the default configuration JSON and exit")
 	configFlag := flag.String("config", "", "Path to a config file (overrides ~/.bwai.json)")

cmd/bwai/update.go

@@ -0,0 +1,198 @@
+package main
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+	"syscall"
+	"time"
+)
+
+const releasesAPI = "https://api.github.com/repos/umago/bubblewrap-ai/releases/latest"
+
+const maxBinarySize = 10 << 20 // 10 MB
+
+var (
+	apiClient      = &http.Client{Timeout: 30 * time.Second}
+	downloadClient = &http.Client{Timeout: 120 * time.Second}
+)
+
+type githubRelease struct {
+	TagName string        `json:"tag_name"`
+	Assets  []githubAsset `json:"assets"`
+}
+
+type githubAsset struct {
+	Name               string `json:"name"`
+	BrowserDownloadURL string `json:"browser_download_url"`
+	Digest             string `json:"digest"`
+}
+
+// runUpdate downloads the latest bwai binary from GitHub releases,
+// verifies its SHA-256 digest, and replaces the current binary in-place.
+func runUpdate() {
+	currentExe, err := os.Executable()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "bwai: cannot determine current executable: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Println("Checking for latest release...")
+
+	release, err := fetchLatestRelease()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "bwai: %v\n", err)
+		os.Exit(1)
+	}
+
+	asset := findAsset(release.Assets, "bwai")
+	if asset == nil {
+		fmt.Fprintf(os.Stderr, "bwai: no 'bwai' asset found in release %s\n", release.TagName)
+		os.Exit(1)
+	}
+
+	fmt.Printf("Downloading bwai %s...\n", release.TagName)
+
+	data, err := downloadAsset(asset.BrowserDownloadURL)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "bwai: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("Downloaded %d bytes.\n", len(data))
+
+	if asset.Digest == "" {
+		fmt.Fprintln(os.Stderr, "bwai: no digest available — refusing to install unverified binary")
+		os.Exit(1)
+	}
+	if err := verifyDigest(data, asset.Digest); err != nil {
+		fmt.Fprintf(os.Stderr, "bwai: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Println("SHA-256 digest verified.")
+
+	if err := replaceBinary(data, currentExe); err != nil {
+		fmt.Fprintf(os.Stderr, "bwai: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("bwai updated successfully (%s → %s).\n", version, release.TagName)
+}
+
+func fetchLatestRelease() (*githubRelease, error) {
+	resp, err := apiClient.Get(releasesAPI)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch latest release: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GitHub API returned HTTP %d", resp.StatusCode)
+	}
+
+	var release githubRelease
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return nil, fmt.Errorf("failed to parse release response: %w", err)
+	}
+	return &release, nil
+}
+
+func findAsset(assets []githubAsset, name string) *githubAsset {
+	for i := range assets {
+		if assets[i].Name == name {
+			return &assets[i]
+		}
+	}
+	return nil
+}
+
+func downloadAsset(url string) ([]byte, error) {
+	resp, err := downloadClient.Get(url)
+	if err != nil {
+		return nil, fmt.Errorf("failed to download binary: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("download failed with HTTP %d", resp.StatusCode)
+	}
+
+	data, err := io.ReadAll(io.LimitReader(resp.Body, maxBinarySize+1))
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response body: %w", err)
+	}
+	if int64(len(data)) > maxBinarySize {
+		return nil, fmt.Errorf("downloaded binary exceeds max size of %d bytes", maxBinarySize)
+	}
+	return data, nil
+}
+
+// verifyDigest compares the SHA-256 of data against the expected digest.
+// The digest from GitHub is in the format "sha256:hex...".
+func verifyDigest(data []byte, expected string) error {
+	colon := strings.Index(expected, ":")
+	if colon >= 0 {
+		expected = expected[colon+1:]
+	}
+
+	hash := sha256.Sum256(data)
+	actual := hex.EncodeToString(hash[:])
+
+	if actual != expected {
+		return fmt.Errorf("digest mismatch: expected %s, got %s", expected, actual)
+	}
+	return nil
+}
+
+// replaceBinary writes the new binary data to the current executable path.
+// The current binary is renamed to .old first to avoid ETXTBSY on Linux.
+func replaceBinary(data []byte, currentExe string) error {
+	oldExe := currentExe + ".old"
+
+	// Clean up leftover from a previous failed update
+	if _, err := os.Stat(oldExe); err == nil {
+		if err := os.Remove(oldExe); err != nil {
+			return fmt.Errorf("failed to remove stale backup %s: %w", oldExe, err)
+		}
+	}
+
+	// Rename current binary out of the way
+	if _, err := os.Stat(currentExe); err == nil {
+		if err := os.Rename(currentExe, oldExe); err != nil {
+			return fmt.Errorf("failed to rename %s: %w", currentExe, err)
+		}
+	}
+
+	// Write the new binary
+	if err := os.WriteFile(currentExe, data, 0o755); err != nil {
+		// Try to restore the old binary
+		if _, statErr := os.Stat(oldExe); statErr == nil {
+			if renameErr := os.Rename(oldExe, currentExe); renameErr != nil {
+				fmt.Fprintf(os.Stderr, "bwai: CRITICAL — failed to restore backup after write error: %v\n", renameErr)
+			}
+		}
+		return fmt.Errorf("failed to write new binary to %s: %w", currentExe, err)
+	}
+
+	// Preserve ownership from the old binary
+	if info, err := os.Stat(oldExe); err == nil {
+		if stat, ok := info.Sys().(*syscall.Stat_t); ok {
+			if err := os.Chown(currentExe, int(stat.Uid), int(stat.Gid)); err != nil {
+				if renameErr := os.Rename(oldExe, currentExe); renameErr != nil {
+					fmt.Fprintf(os.Stderr, "bwai: CRITICAL — failed to restore backup after chown error: %v\n", renameErr)
+				}
+				return fmt.Errorf("failed to chown new binary: %w", err)
+			}
+		}
+	}
+
+	// Delete the old backup
+	_ = os.Remove(oldExe)
+
+	return nil
+}

cmd/bwai/update_test.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestVerifyDigest_MatchingSHA256(t *testing.T) {
+	data := []byte("hello world")
+	hash := sha256.Sum256(data)
+	expected := "sha256:" + hex.EncodeToString(hash[:])
+
+	if err := verifyDigest(data, expected); err != nil {
+		t.Fatalf("expected no error, got: %v", err)
+	}
+}
+
+func TestVerifyDigest_BareHex(t *testing.T) {
+	data := []byte("hello world")
+	hash := sha256.Sum256(data)
+	expected := hex.EncodeToString(hash[:])
+
+	if err := verifyDigest(data, expected); err != nil {
+		t.Fatalf("expected no error, got: %v", err)
+	}
+}
+
+func TestVerifyDigest_Mismatch(t *testing.T) {
+	data := []byte("hello world")
+	expected := "sha256:0000000000000000000000000000000000000000000000000000000000000000"
+
+	err := verifyDigest(data, expected)
+	if err == nil {
+		t.Fatal("expected error on digest mismatch, got nil")
+	}
+	if !strings.Contains(err.Error(), "digest mismatch") {
+		t.Errorf("error should mention 'digest mismatch', got: %v", err)
+	}
+}
+
+func TestFindAsset_Found(t *testing.T) {
+	assets := []githubAsset{
+		{Name: "checksums.txt"},
+		{Name: "bwai", BrowserDownloadURL: "https://example.com/bwai"},
+	}
+	a := findAsset(assets, "bwai")
+	if a == nil {
+		t.Fatal("expected to find 'bwai' asset")
+	}
+	if a.BrowserDownloadURL != "https://example.com/bwai" {
+		t.Errorf("unexpected URL: %s", a.BrowserDownloadURL)
+	}
+}
+
+func TestFindAsset_NotFound(t *testing.T) {
+	assets := []githubAsset{
+		{Name: "checksums.txt"},
+	}
+	if findAsset(assets, "bwai") != nil {
+		t.Fatal("expected nil for missing asset")
+	}
+}
+
+func TestReplaceBinary_Basic(t *testing.T) {
+	dir := t.TempDir()
+	current := filepath.Join(dir, "bwai")
+
+	if err := os.WriteFile(current, []byte("old version"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := replaceBinary([]byte("new version"), current); err != nil {
+		t.Fatalf("replaceBinary failed: %v", err)
+	}
+
+	content, err := os.ReadFile(current)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(content) != "new version" {
+		t.Errorf("expected 'new version', got %q", content)
+	}
+
+	// Old backup should be cleaned up
+	if _, err := os.Stat(current + ".old"); !os.IsNotExist(err) {
+		t.Error("old backup should have been removed")
+	}
+}
+
+func TestReplaceBinary_NoExistingFile(t *testing.T) {
+	dir := t.TempDir()
+	current := filepath.Join(dir, "bwai")
+
+	if err := replaceBinary([]byte("fresh install"), current); err != nil {
+		t.Fatalf("replaceBinary failed: %v", err)
+	}
+
+	content, err := os.ReadFile(current)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(content) != "fresh install" {
+		t.Errorf("expected 'fresh install', got %q", content)
+	}
+}
+
+func TestReplaceBinary_Permissions(t *testing.T) {
+	dir := t.TempDir()
+	current := filepath.Join(dir, "bwai")
+
+	if err := os.WriteFile(current, []byte("old version"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := replaceBinary([]byte("new version"), current); err != nil {
+		t.Fatalf("replaceBinary failed: %v", err)
+	}
+
+	info, err := os.Stat(current)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if info.Mode().Perm() != 0o755 {
+		t.Errorf("expected 0o755 permissions, got %o", info.Mode().Perm())
+	}
+}
+
+func TestReplaceBinary_CleansStaleBackup(t *testing.T) {
+	dir := t.TempDir()
+	current := filepath.Join(dir, "bwai")
+
+	if err := os.WriteFile(current, []byte("current"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(current+".old", []byte("stale"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := replaceBinary([]byte("new"), current); err != nil {
+		t.Fatalf("replaceBinary failed: %v", err)
+	}
+
+	if _, err := os.Stat(current + ".old"); !os.IsNotExist(err) {
+		t.Error("stale backup should have been removed before update")
+	}
+}