refactor: rename updater package to update

internal/update/apply.go

@@ -0,0 +1,208 @@
+package update
+
+import (
+	"bufio"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"github.com/mathismqn/godeez/internal/buildinfo"
+	"github.com/mathismqn/godeez/internal/fsutil"
+)
+
+var managedPrefixes = []string{
+	"/nix/store",
+	"/opt/homebrew",
+	"/usr/local/Cellar",
+	"/home/linuxbrew",
+	"/snap",
+	"/var/lib/flatpak",
+}
+
+func resolveTarget() (string, error) {
+	if buildinfo.IsDev() {
+		return "", fmt.Errorf("development build cannot self-update. Install a release from https://github.com/%s/%s/releases",
+			repoOwner, repoName)
+	}
+
+	exe, err := os.Executable()
+	if err != nil {
+		return "", fmt.Errorf("failed to locate the running binary: %w", err)
+	}
+
+	target := exe
+	if resolved, err := filepath.EvalSymlinks(exe); err == nil {
+		target = resolved
+	}
+
+	for _, prefix := range managedPrefixes {
+		if strings.HasPrefix(target, prefix) {
+			return "", fmt.Errorf("%s was installed by a package manager. Update it with that instead", target)
+		}
+	}
+
+	return target, nil
+}
+
+func CheckUpdatable() error {
+	_, err := resolveTarget()
+
+	return err
+}
+
+func checkWritable(dir string) error {
+	f, err := os.CreateTemp(dir, tmpPattern)
+	if err != nil {
+		hint := "Re-run with sudo"
+		if runtime.GOOS == "windows" {
+			hint = "Re-run from an elevated prompt"
+		}
+
+		return fmt.Errorf("cannot write to %s: %w. %s", dir, err, hint)
+	}
+
+	name := f.Name()
+	f.Close()
+	os.Remove(name)
+
+	return nil
+}
+
+func (u *Updater) Apply(ctx context.Context, release *Release) error {
+	target, err := resolveTarget()
+	if err != nil {
+		return err
+	}
+
+	dir := filepath.Dir(target)
+	if err := checkWritable(dir); err != nil {
+		return err
+	}
+
+	asset, err := release.assetForRuntime()
+	if err != nil {
+		return err
+	}
+
+	want, err := u.fetchChecksum(ctx, release, asset.Name)
+	if err != nil {
+		return err
+	}
+
+	u.step("Downloading %s", asset.Name)
+	tmp, sum, err := u.download(ctx, dir, asset)
+	if err != nil {
+		return err
+	}
+	defer fsutil.Remove(tmp)
+
+	u.step("Verifying checksum")
+	if sum != want {
+		return fmt.Errorf("checksum mismatch for %s: expected %s, got %s", asset.Name, want, sum)
+	}
+
+	if err := os.Chmod(tmp, 0755); err != nil {
+		return err
+	}
+
+	u.step("Replacing %s", target)
+
+	return replaceBinary(target, tmp)
+}
+
+func (u *Updater) fetchChecksum(ctx context.Context, release *Release, assetName string) (string, error) {
+	asset, ok := release.asset(checksumsAsset)
+	if !ok {
+		return "", fmt.Errorf("release %s does not publish %s", release.TagName, checksumsAsset)
+	}
+
+	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
+	defer cancel()
+
+	body, err := u.get(ctx, asset.URL, nil)
+	if err != nil {
+		return "", err
+	}
+	defer body.Close()
+
+	return parseChecksums(io.LimitReader(body, maxResponseSize), assetName)
+}
+
+func parseChecksums(r io.Reader, name string) (string, error) {
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) != 2 {
+			continue
+		}
+		if strings.TrimPrefix(fields[1], "*") == name {
+			return strings.ToLower(fields[0]), nil
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return "", err
+	}
+
+	return "", fmt.Errorf("no checksum listed for %s", name)
+}
+
+func (u *Updater) download(ctx context.Context, dir string, asset Asset) (string, string, error) {
+	body, err := u.get(ctx, asset.URL, nil)
+	if err != nil {
+		return "", "", err
+	}
+	defer body.Close()
+
+	f, err := os.CreateTemp(dir, tmpPattern)
+	if err != nil {
+		return "", "", err
+	}
+	tmp := f.Name()
+
+	hash := sha256.New()
+	if _, err := io.Copy(io.MultiWriter(f, hash), body); err != nil {
+		f.Close()
+		fsutil.Remove(tmp)
+
+		return "", "", fmt.Errorf("failed to download %s: %w", asset.Name, err)
+	}
+	if err := f.Close(); err != nil {
+		fsutil.Remove(tmp)
+
+		return "", "", err
+	}
+
+	return tmp, hex.EncodeToString(hash.Sum(nil)), nil
+}
+
+func replaceBinary(target, tmp string) error {
+	if runtime.GOOS != "windows" {
+		return os.Rename(tmp, target)
+	}
+
+	old := target + ".old"
+	os.Remove(old)
+
+	if err := os.Rename(target, old); err != nil {
+		return fmt.Errorf("failed to move the current binary aside: %w", err)
+	}
+
+	if err := os.Rename(tmp, target); err != nil {
+		if rollbackErr := os.Rename(old, target); rollbackErr != nil {
+			return fmt.Errorf("failed to install the new binary: %w. The previous one could not be restored from %s: %v",
+				err, old, rollbackErr)
+		}
+
+		return fmt.Errorf("failed to install the new binary: %w", err)
+	}
+
+	os.Remove(old)
+
+	return nil
+}