Unify backend open config construction

internal/app/backends.go

@@ -37,6 +37,22 @@ type backendFactory struct {
 	readOnlyKnownHosts bool
 }
 
+type backendOpenSpec struct {
+	role        string
+	backend     string
+	path        string
+	host        string
+	user        string
+	port        int
+	ssh         config.SSH
+	endpoint    string
+	bucket      string
+	prefix      string
+	region      string
+	forcePath   *bool
+	credentials config.Credentials
+}
+
 func newBackendFactory() *backendFactory {
 	return newBackendFactoryWithEnvironment(config.ProcessEnvironment())
 }
@@ -91,25 +107,11 @@ func newBackendFactoryWithEnvironment(environment config.Environment) *backendFa
 }
 
 func (f *backendFactory) openSource(ctx context.Context, source config.Backend) (storage.Backend, error) {
-	if source.Backend != config.BackendLocal && source.Backend != config.BackendSSH && source.Backend != config.BackendS3 {
-		return nil, fmt.Errorf("source backend %s is not implemented for execution", source.Backend)
-	}
-	openConfig, err := f.sourceOpenConfig(source)
-	if err != nil {
-		return nil, err
-	}
-	return f.registry.Open(ctx, source.Backend, openConfig)
+	return f.openBackend(ctx, backendOpenSpecFromSource(source))
 }
 
 func (f *backendFactory) openDestination(ctx context.Context, destination config.Destination) (storage.Backend, error) {
-	if destination.Backend != config.BackendLocal && destination.Backend != config.BackendSSH && destination.Backend != config.BackendS3 {
-		return nil, fmt.Errorf("backend %s is not implemented for execution", destination.Backend)
-	}
-	openConfig, err := f.destinationOpenConfig(destination)
-	if err != nil {
-		return nil, err
-	}
-	return f.registry.Open(ctx, destination.Backend, openConfig)
+	return f.openBackend(ctx, backendOpenSpecFromDestination(destination))
 }
 
 func (f *backendFactory) openLocalPath(ctx context.Context, path string) (storage.Backend, error) {
@@ -120,40 +122,51 @@ func (f *backendFactory) resolveCredentials(creds config.Credentials) (config.Re
 	return f.environment.ResolveCredentials(creds)
 }
 
-func (f *backendFactory) sourceOpenConfig(source config.Backend) (storage.OpenConfig, error) {
-	cfg := sourceOpenConfig(source)
-	if source.Backend == config.BackendS3 {
-		if err := f.addS3Config(cfg, source.Endpoint, source.Bucket, source.Prefix, source.Region, source.ForcePath, source.Creds); err != nil {
+func (f *backendFactory) openBackend(ctx context.Context, spec backendOpenSpec) (storage.Backend, error) {
+	if !backendExecutable(spec.backend) {
+		if spec.role == "source" {
+			return nil, fmt.Errorf("source backend %s is not implemented for execution", spec.backend)
+		}
+		return nil, fmt.Errorf("backend %s is not implemented for execution", spec.backend)
+	}
+	openConfig, err := f.openConfig(spec)
+	if err != nil {
+		return nil, err
+	}
+	return f.registry.Open(ctx, spec.backend, openConfig)
+}
+
+func backendExecutable(name string) bool {
+	return name == config.BackendLocal || name == config.BackendSSH || name == config.BackendS3
+}
+
+func (f *backendFactory) openConfig(spec backendOpenSpec) (storage.OpenConfig, error) {
+	cfg := storage.OpenConfig{storagePathKey: spec.path}
+	switch spec.backend {
+	case config.BackendSSH:
+		cfg[sshHostKey] = spec.host
+		cfg[sshUserKey] = spec.user
+		cfg[sshPortKey] = strconv.Itoa(spec.port)
+		cfg[sshKeyFileKey] = spec.ssh.KeyFile
+		cfg[sshKnownHostsKey] = spec.ssh.KnownHosts
+		cfg[sshHostKeyPolicyKey] = string(spec.ssh.HostKeyPolicy)
+		cfg[sshReadOnlyHostsKey] = strconv.FormatBool(f.readOnlyKnownHosts)
+	case config.BackendS3:
+		if err := f.addS3Config(cfg, spec); err != nil {
 			return nil, err
 		}
 	}
-	if source.Backend == config.BackendSSH {
-		cfg[sshReadOnlyHostsKey] = strconv.FormatBool(f.readOnlyKnownHosts)
-	}
 	return cfg, nil
 }
 
-func (f *backendFactory) destinationOpenConfig(destination config.Destination) (storage.OpenConfig, error) {
-	cfg := destinationOpenConfig(destination)
-	if destination.Backend == config.BackendS3 {
-		if err := f.addS3Config(cfg, destination.Endpoint, destination.Bucket, destination.Prefix, destination.Region, destination.ForcePath, destination.Creds); err != nil {
-			return nil, err
-		}
-	}
-	if destination.Backend == config.BackendSSH {
-		cfg[sshReadOnlyHostsKey] = strconv.FormatBool(f.readOnlyKnownHosts)
-	}
-	return cfg, nil
-}
-
-func (f *backendFactory) addS3Config(cfg storage.OpenConfig, endpoint, bucket, prefix, region string, forcePath *bool, creds config.Credentials) error {
-	cfg[s3EndpointKey] = endpoint
-	cfg[s3BucketKey] = bucket
-	cfg[s3PrefixKey] = prefix
-	cfg[s3RegionKey] = region
-	cfg[s3ForcePathStyleKey] = strconv.FormatBool(config.ForcePathStyle(forcePath))
-	if creds.AccessKeyIDEnv != "" || creds.SecretAccessKeyEnv != "" {
-		resolved, err := f.resolveCredentials(creds)
+func (f *backendFactory) addS3Config(cfg storage.OpenConfig, spec backendOpenSpec) error {
+	cfg[s3EndpointKey] = spec.endpoint
+	cfg[s3BucketKey] = spec.bucket
+	cfg[s3PrefixKey] = spec.prefix
+	cfg[s3RegionKey] = spec.region
+	cfg[s3ForcePathStyleKey] = strconv.FormatBool(config.ForcePathStyle(spec.forcePath))
+	if spec.credentials.AccessKeyIDEnv != "" || spec.credentials.SecretAccessKeyEnv != "" {
+		resolved, err := f.resolveCredentials(spec.credentials)
 		if err != nil {
 			return err
 		}
@@ -163,30 +176,38 @@ func (f *backendFactory) addS3Config(cfg storage.OpenConfig, endpoint, bucket, p
 	return nil
 }
 
-func sourceOpenConfig(source config.Backend) storage.OpenConfig {
-	cfg := storage.OpenConfig{storagePathKey: source.Path}
-	if source.Backend == config.BackendSSH {
-		cfg[sshHostKey] = source.Host
-		cfg[sshUserKey] = source.User
-		cfg[sshPortKey] = strconv.Itoa(source.Port)
-		cfg[sshKeyFileKey] = source.SSH.KeyFile
-		cfg[sshKnownHostsKey] = source.SSH.KnownHosts
-		cfg[sshHostKeyPolicyKey] = string(source.SSH.HostKeyPolicy)
-		cfg[sshReadOnlyHostsKey] = "false"
+func backendOpenSpecFromSource(source config.Backend) backendOpenSpec {
+	return backendOpenSpec{
+		role:        "source",
+		backend:     source.Backend,
+		path:        source.Path,
+		host:        source.Host,
+		user:        source.User,
+		port:        source.Port,
+		ssh:         source.SSH,
+		endpoint:    source.Endpoint,
+		bucket:      source.Bucket,
+		prefix:      source.Prefix,
+		region:      source.Region,
+		forcePath:   source.ForcePath,
+		credentials: source.Creds,
 	}
-	return cfg
 }
 
-func destinationOpenConfig(destination config.Destination) storage.OpenConfig {
-	cfg := storage.OpenConfig{storagePathKey: destination.Path}
-	if destination.Backend == config.BackendSSH {
-		cfg[sshHostKey] = destination.Host
-		cfg[sshUserKey] = destination.User
-		cfg[sshPortKey] = strconv.Itoa(destination.Port)
-		cfg[sshKeyFileKey] = destination.SSH.KeyFile
-		cfg[sshKnownHostsKey] = destination.SSH.KnownHosts
-		cfg[sshHostKeyPolicyKey] = string(destination.SSH.HostKeyPolicy)
-		cfg[sshReadOnlyHostsKey] = "false"
+func backendOpenSpecFromDestination(destination config.Destination) backendOpenSpec {
+	return backendOpenSpec{
+		role:        "destination",
+		backend:     destination.Backend,
+		path:        destination.Path,
+		host:        destination.Host,
+		user:        destination.User,
+		port:        destination.Port,
+		ssh:         destination.SSH,
+		endpoint:    destination.Endpoint,
+		bucket:      destination.Bucket,
+		prefix:      destination.Prefix,
+		region:      destination.Region,
+		forcePath:   destination.ForcePath,
+		credentials: destination.Creds,
 	}
-	return cfg
 }