Pull request 1897: nextapi-write-conf

Squashed commit of the following:

commit 72f25ffe73d6b8216b01e590fba66fb5f6944113
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Jun 28 21:29:04 2023 +0300

    next: add conf writing, validation

internal/next/configmgr/configmgr.go

@@ -1,5 +1,7 @@
 // Package configmgr defines the AdGuard Home on-disk configuration entities and
 // configuration manager.
+//
+// TODO(a.garipov): Add tests.
 package configmgr
 
 import (
@@ -14,6 +16,10 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/next/dnssvc"
 	"github.com/AdguardTeam/AdGuardHome/internal/next/websvc"
 	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/timeutil"
+	"github.com/google/renameio/maybe"
+	"golang.org/x/exp/slices"
 	"gopkg.in/yaml.v3"
 )
 
@@ -39,17 +45,58 @@ type Manager struct {
 	fileName string
 }
 
+// Validate returns an error if the configuration file with the given name does
+// not exist or is invalid.
+func Validate(fileName string) (err error) {
+	conf, err := read(fileName)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return err
+	}
+
+	// Don't wrap the error, because it's informative enough as is.
+	return conf.validate()
+}
+
 // New creates a new *Manager that persists changes to the file pointed to by
 // fileName.  It reads the configuration file and populates the service fields.
 // start is the startup time of AdGuard Home.
 func New(
+	ctx context.Context,
 	fileName string,
 	frontend fs.FS,
 	start time.Time,
 ) (m *Manager, err error) {
+	conf, err := read(fileName)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, err
+	}
+
+	err = conf.validate()
+	if err != nil {
+		return nil, fmt.Errorf("validating config: %w", err)
+	}
+
+	m = &Manager{
+		updMu:    &sync.RWMutex{},
+		current:  conf,
+		fileName: fileName,
+	}
+
+	err = m.assemble(ctx, conf, frontend, start)
+	if err != nil {
+		return nil, fmt.Errorf("creating config manager: %w", err)
+	}
+
+	return m, nil
+}
+
+// read reads and decodes configuration from the provided filename.
+func read(fileName string) (conf *config, err error) {
 	defer func() { err = errors.Annotate(err, "reading config: %w") }()
 
-	conf := &config{}
+	conf = &config{}
 	f, err := os.Open(fileName)
 	if err != nil {
 		// Don't wrap the error, because it's informative enough as is.
@@ -63,27 +110,7 @@ func New(
 		return nil, err
 	}
 
-	// TODO(a.garipov): Validate the configuration structure.  Return an error
-	// if it's incorrect.
-
-	m = &Manager{
-		updMu:    &sync.RWMutex{},
-		current:  conf,
-		fileName: fileName,
-	}
-
-	// TODO(a.garipov): Get the context with the timeout from the arguments?
-	const assemblyTimeout = 5 * time.Second
-	ctx, cancel := context.WithTimeout(context.Background(), assemblyTimeout)
-	defer cancel()
-
-	err = m.assemble(ctx, conf, frontend, start)
-	if err != nil {
-		// Don't wrap the error, because it's informative enough as is.
-		return nil, err
-	}
-
-	return m, nil
+	return conf, nil
 }
 
 // assemble creates all services and puts them into the corresponding fields.
@@ -128,6 +155,23 @@ func (m *Manager) assemble(
 	return nil
 }
 
+// write writes the current configuration to disk.
+func (m *Manager) write() (err error) {
+	b, err := yaml.Marshal(m.current)
+	if err != nil {
+		return fmt.Errorf("encoding: %w", err)
+	}
+
+	err = maybe.WriteFile(m.fileName, b, 0o755)
+	if err != nil {
+		return fmt.Errorf("writing: %w", err)
+	}
+
+	log.Info("configmgr: written to %q", m.fileName)
+
+	return nil
+}
+
 // DNS returns the current DNS service.  It is safe for concurrent use.
 func (m *Manager) DNS() (dns agh.ServiceWithConfig[*dnssvc.Config]) {
 	m.updMu.RLock()
@@ -150,7 +194,9 @@ func (m *Manager) UpdateDNS(ctx context.Context, c *dnssvc.Config) (err error) {
 		return fmt.Errorf("reassembling dnssvc: %w", err)
 	}
 
-	return nil
+	m.updateCurrentDNS(c)
+
+	return m.write()
 }
 
 // updateDNS recreates the DNS service.  m.updMu is expected to be locked.
@@ -172,6 +218,17 @@ func (m *Manager) updateDNS(ctx context.Context, c *dnssvc.Config) (err error) {
 	return nil
 }
 
+// updateCurrentDNS updates the DNS configuration in the current config.
+func (m *Manager) updateCurrentDNS(c *dnssvc.Config) {
+	m.current.DNS.Addresses = slices.Clone(c.Addresses)
+	m.current.DNS.BootstrapDNS = slices.Clone(c.BootstrapServers)
+	m.current.DNS.UpstreamDNS = slices.Clone(c.UpstreamServers)
+	m.current.DNS.DNS64Prefixes = slices.Clone(c.DNS64Prefixes)
+	m.current.DNS.UpstreamTimeout = timeutil.Duration{Duration: c.UpstreamTimeout}
+	m.current.DNS.BootstrapPreferIPv6 = c.BootstrapPreferIPv6
+	m.current.DNS.UseDNS64 = c.UseDNS64
+}
+
 // Web returns the current web service.  It is safe for concurrent use.
 func (m *Manager) Web() (web agh.ServiceWithConfig[*websvc.Config]) {
 	m.updMu.RLock()
@@ -194,7 +251,9 @@ func (m *Manager) UpdateWeb(ctx context.Context, c *websvc.Config) (err error) {
 		return fmt.Errorf("reassembling websvc: %w", err)
 	}
 
-	return nil
+	m.updateCurrentWeb(c)
+
+	return m.write()
 }
 
 // updateWeb recreates the web service.  m.upd is expected to be locked.
@@ -213,3 +272,11 @@ func (m *Manager) updateWeb(ctx context.Context, c *websvc.Config) (err error) {
 
 	return nil
 }
+
+// updateCurrentWeb updates the web configuration in the current config.
+func (m *Manager) updateCurrentWeb(c *websvc.Config) {
+	m.current.HTTP.Addresses = slices.Clone(c.Addresses)
+	m.current.HTTP.SecureAddresses = slices.Clone(c.SecureAddresses)
+	m.current.HTTP.Timeout = timeutil.Duration{Duration: c.Timeout}
+	m.current.HTTP.ForceHTTPS = c.ForceHTTPS
+}