Pull request 2383: AGDNS-2743-aghuser

Merge in DNS/adguard-home from AGDNS-2743-aghuser to master

Squashed commit of the following:

commit e3920df62be1625a3cfcc314a4aab3d1a378ca53
Merge: 70ce647f4 106785aab
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Apr 7 19:44:15 2025 +0300

    Merge branch 'master' into AGDNS-2743-aghuser

commit 70ce647f47921f2bb34a561d63de2041f31e6bce
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Fri Apr 4 18:17:09 2025 +0300

    aghuser: imp docs

commit 87f6984248189de4a3dc0f2a245775141ea974d0
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Apr 2 19:03:03 2025 +0300

    aghuser: imp code

commit 636ecae85d1fce1657b5699a29451a9079d40222
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Apr 1 17:30:54 2025 +0300

    all: add tests

commit 5c842e94111123cf988332ccd1eb6754fa45585d
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Mar 27 21:44:25 2025 +0300

    all: aghuser

internal/aghuser/db.go

@@ -0,0 +1,149 @@
+package aghuser
+
+import (
+	"cmp"
+	"context"
+	"fmt"
+	"maps"
+	"slices"
+	"sync"
+
+	"github.com/AdguardTeam/golibs/errors"
+)
+
+// DB is an interface that defines methods for interacting with user
+// information.  All methods must be safe for concurrent use.
+//
+// TODO(s.chzhen):  Use this.
+//
+// TODO(s.chzhen):  Consider updating methods to return a clone.
+type DB interface {
+	// All retrieves all users from the database, sorted by login.
+	//
+	// TODO(s.chzhen):  Consider function signature change to reflect the
+	// in-memory implementation, as it currently always returns nil for error.
+	All(ctx context.Context) (users []*User, err error)
+
+	// ByLogin retrieves a user by their login.  u must not be modified.
+	//
+	// TODO(s.chzhen):  Remove this once user sessions support [UserID].
+	ByLogin(ctx context.Context, login Login) (u *User, err error)
+
+	// ByUUID retrieves a user by their unique identifier.  u must not be
+	// modified.
+	//
+	// TODO(s.chzhen):  Use this.
+	ByUUID(ctx context.Context, id UserID) (u *User, err error)
+
+	// Create adds a new user to the database.  If the credentials already
+	// exist, it returns the [errors.ErrDuplicated] error.  It also can return
+	// an error from the cryptographic randomness reader.  u must not be
+	// modified.
+	Create(ctx context.Context, u *User) (err error)
+}
+
+// DefaultDB is the default in-memory implementation of the [DB] interface.
+type DefaultDB struct {
+	// mu protects all properties below.
+	mu *sync.Mutex
+
+	// loginToUserID maps a web user login to their UserID.  The values must not
+	// be empty.
+	//
+	// TODO(s.chzhen):  Remove this once user sessions support [UserID].
+	loginToUserID map[Login]UserID
+
+	// userIDToUser maps a UserID to a web user.  The values must not be nil.
+	// It must be synchronized with loginToUserID, meaning all UserIDs stored in
+	// loginToUserID must also be stored in this map.
+	userIDToUser map[UserID]*User
+}
+
+// NewDefaultDB returns the new properly initialized *DefaultDB.
+func NewDefaultDB() (db *DefaultDB) {
+	return &DefaultDB{
+		mu:            &sync.Mutex{},
+		loginToUserID: map[Login]UserID{},
+		userIDToUser:  map[UserID]*User{},
+	}
+}
+
+// type check
+var _ DB = (*DefaultDB)(nil)
+
+// All implements the [DB] interface for *DefaultDB.
+func (db *DefaultDB) All(ctx context.Context) (users []*User, err error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if len(db.userIDToUser) == 0 {
+		return nil, nil
+	}
+
+	users = slices.SortedStableFunc(
+		maps.Values(db.userIDToUser),
+		func(a, b *User) (res int) {
+			// TODO(s.chzhen):  Consider adding a custom comparer.
+			return cmp.Compare(a.Login, b.Login)
+		},
+	)
+
+	return users, nil
+}
+
+// ByLogin implements the [DB] interface for *DefaultDB.
+func (db *DefaultDB) ByLogin(ctx context.Context, login Login) (u *User, err error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	id, ok := db.loginToUserID[login]
+	if !ok {
+		return nil, nil
+	}
+
+	u, ok = db.userIDToUser[id]
+	if !ok {
+		// Should not happen.
+		panic(fmt.Errorf("no web user present with login %q", login))
+	}
+
+	return u, nil
+}
+
+// ByUUID implements the [DB] interface for *DefaultDB.
+func (db *DefaultDB) ByUUID(ctx context.Context, id UserID) (u *User, err error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	u, ok := db.userIDToUser[id]
+	if !ok {
+		return nil, nil
+	}
+
+	return u, nil
+}
+
+// Create implements the [DB] interface for *DefaultDB.
+func (db *DefaultDB) Create(ctx context.Context, u *User) (err error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if u.ID == (UserID{}) {
+		return fmt.Errorf("userid: %w", errors.ErrEmptyValue)
+	}
+
+	_, ok := db.userIDToUser[u.ID]
+	if ok {
+		return fmt.Errorf("userid: %w", errors.ErrDuplicated)
+	}
+
+	_, ok = db.loginToUserID[u.Login]
+	if ok {
+		return fmt.Errorf("login: %w", errors.ErrDuplicated)
+	}
+
+	db.userIDToUser[u.ID] = u
+	db.loginToUserID[u.Login] = u.ID
+
+	return nil
+}