feat: game lobby service

lobby/internal/adapters/idgen/generator.go

@@ -0,0 +1,144 @@
+// Package idgen provides the default crypto/rand-backed implementation of
+// ports.IDGenerator for Game Lobby Service.
+package idgen
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"fmt"
+	"io"
+	"strings"
+
+	"galaxy/lobby/internal/domain/common"
+)
+
+// gameIDTokenBytes stores the number of random bytes consumed per
+// NewGameID call. Ten bytes produce a 16-character base32 suffix, which
+// gives 80 bits of entropy — well above the birthday-collision bound for the
+// expected Game Lobby record volume.
+const gameIDTokenBytes = 10
+
+// applicationIDTokenBytes mirrors gameIDTokenBytes for application records.
+// 80 bits of entropy is well above the birthday-collision bound for the
+// expected application volume.
+const applicationIDTokenBytes = 10
+
+// inviteIDTokenBytes mirrors gameIDTokenBytes for invite records.
+const inviteIDTokenBytes = 10
+
+// membershipIDTokenBytes mirrors gameIDTokenBytes for membership records.
+const membershipIDTokenBytes = 10
+
+// base32NoPadding is the standard RFC 4648 base32 alphabet without padding,
+// matching the identifier shape used by `galaxy/user/internal/adapters/local`.
+var base32NoPadding = base32.StdEncoding.WithPadding(base32.NoPadding)
+
+// Generator is the default opaque-identifier generator for Game Lobby
+// records. Zero value is ready for use and draws randomness from
+// crypto/rand.Reader.
+type Generator struct {
+	// reader stores the cryptographic randomness source. A nil reader falls
+	// back to crypto/rand.Reader.
+	reader io.Reader
+}
+
+// Option configures an optional Generator setting.
+type Option func(*Generator)
+
+// WithRandomSource overrides the cryptographic randomness source. It is
+// intended for deterministic tests; production code relies on the default
+// crypto/rand.Reader.
+func WithRandomSource(reader io.Reader) Option {
+	return func(gen *Generator) {
+		gen.reader = reader
+	}
+}
+
+// NewGenerator constructs one Generator with the supplied options applied.
+func NewGenerator(opts ...Option) *Generator {
+	gen := &Generator{}
+	for _, opt := range opts {
+		opt(gen)
+	}
+
+	return gen
+}
+
+// NewGameID returns one newly generated opaque game identifier with the
+// frozen `game-*` prefix.
+func (gen *Generator) NewGameID() (common.GameID, error) {
+	token, err := gen.randomToken(gameIDTokenBytes)
+	if err != nil {
+		return "", fmt.Errorf("generate game id: %w", err)
+	}
+
+	gameID := common.GameID("game-" + token)
+	if err := gameID.Validate(); err != nil {
+		return "", fmt.Errorf("generate game id: %w", err)
+	}
+
+	return gameID, nil
+}
+
+// NewApplicationID returns one newly generated opaque application
+// identifier with the frozen `application-*` prefix.
+func (gen *Generator) NewApplicationID() (common.ApplicationID, error) {
+	token, err := gen.randomToken(applicationIDTokenBytes)
+	if err != nil {
+		return "", fmt.Errorf("generate application id: %w", err)
+	}
+
+	applicationID := common.ApplicationID("application-" + token)
+	if err := applicationID.Validate(); err != nil {
+		return "", fmt.Errorf("generate application id: %w", err)
+	}
+
+	return applicationID, nil
+}
+
+// NewInviteID returns one newly generated opaque invite identifier with the
+// frozen `invite-*` prefix.
+func (gen *Generator) NewInviteID() (common.InviteID, error) {
+	token, err := gen.randomToken(inviteIDTokenBytes)
+	if err != nil {
+		return "", fmt.Errorf("generate invite id: %w", err)
+	}
+
+	inviteID := common.InviteID("invite-" + token)
+	if err := inviteID.Validate(); err != nil {
+		return "", fmt.Errorf("generate invite id: %w", err)
+	}
+
+	return inviteID, nil
+}
+
+// NewMembershipID returns one newly generated opaque membership identifier
+// with the frozen `membership-*` prefix.
+func (gen *Generator) NewMembershipID() (common.MembershipID, error) {
+	token, err := gen.randomToken(membershipIDTokenBytes)
+	if err != nil {
+		return "", fmt.Errorf("generate membership id: %w", err)
+	}
+
+	membershipID := common.MembershipID("membership-" + token)
+	if err := membershipID.Validate(); err != nil {
+		return "", fmt.Errorf("generate membership id: %w", err)
+	}
+
+	return membershipID, nil
+}
+
+// randomToken returns one lowercase base32 token of the specified byte
+// entropy.
+func (gen *Generator) randomToken(byteCount int) (string, error) {
+	buffer := make([]byte, byteCount)
+	reader := gen.reader
+	if reader == nil {
+		reader = rand.Reader
+	}
+	if _, err := io.ReadFull(reader, buffer); err != nil {
+		return "", err
+	}
+
+	return strings.ToLower(base32NoPadding.EncodeToString(buffer)), nil
+}