Add game clock commands, command completions and Cyrene login tooling

internal/common/game_clock.go

@@ -0,0 +1,104 @@
+package common
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+// Only game-facing calendar time changes. Network timeouts, diagnostics, leases
+// and battle duration measurement continue to use the host's real clock.
+type GameClockState struct {
+	OffsetMS int64 `json:"offset_ms"`
+}
+
+func gameClockPath() (string, error) {
+	cfg, err := LoadRuntimeConfig()
+	if err != nil {
+		return "", err
+	}
+	return cfg.GameClock.StateFile, nil
+}
+
+func ReadGameClock() (GameClockState, error) {
+	path, err := gameClockPath()
+	if err != nil {
+		return GameClockState{}, err
+	}
+	if path == "" {
+		return GameClockState{}, nil
+	}
+	raw, err := os.ReadFile(path)
+	if os.IsNotExist(err) {
+		return GameClockState{}, nil
+	}
+	if err != nil {
+		return GameClockState{}, err
+	}
+	var state GameClockState
+	if err := json.Unmarshal(raw, &state); err != nil {
+		return state, fmt.Errorf("game clock state: %w", err)
+	}
+	return state, nil
+}
+
+func GameTime() (time.Time, error) {
+	s, err := ReadGameClock()
+	if err != nil {
+		return time.Time{}, err
+	}
+	base := time.Now().UnixMilli()
+	if s.OffsetMS < -base || s.OffsetMS > 253402300799999-base {
+		return time.Time{}, fmt.Errorf("game clock outside supported calendar range")
+	}
+	ms := base + s.OffsetMS
+	return time.UnixMilli(ms), nil
+}
+
+func SetGameTime(target *time.Time) (time.Time, error) {
+	path, err := gameClockPath()
+	if err != nil {
+		return time.Time{}, err
+	}
+	if path == "" {
+		return time.Time{}, fmt.Errorf("configure game_clock.state_file or GAC_GAME_CLOCK_STATE_FILE first")
+	}
+	now := time.Now()
+	state := GameClockState{}
+	if target != nil {
+		if target.UnixMilli() < 0 || target.Year() > 9999 {
+			return time.Time{}, fmt.Errorf("game time must be between Unix epoch and year 9999")
+		}
+		state.OffsetMS = target.UnixMilli() - now.UnixMilli()
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
+		return time.Time{}, err
+	}
+	raw, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return time.Time{}, err
+	}
+	f, err := os.CreateTemp(filepath.Dir(path), ".game-clock-*.tmp")
+	if err != nil {
+		return time.Time{}, err
+	}
+	name := f.Name()
+	defer os.Remove(name)
+	if _, err = f.Write(raw); err != nil {
+		f.Close()
+		return time.Time{}, err
+	}
+	if err = f.Sync(); err != nil {
+		f.Close()
+		return time.Time{}, err
+	}
+	if err = f.Close(); err != nil {
+		return time.Time{}, err
+	}
+	if err = os.Rename(name, path); err != nil {
+		return time.Time{}, err
+	}
+	return time.UnixMilli(now.UnixMilli() + state.OffsetMS), nil
+}