package audit

import "time"

const (
	DefaultRetentionDays = 90
	ForeverRetentionDays = 0
	CleanupHour          = 3
	KeepRecentHours      = 24
	NoSizeLimitGB        = 0
	BytesPerGB           = int64(1) << 30
	RowOverheadBytes     = int64(64)
)

func RetentionOptions() []int {
	return []int{30, 90, 365, ForeverRetentionDays}
}

func ValidateRetentionDays(days int) error {
	for _, option := range RetentionOptions() {
		if option == days {
			return nil
		}
	}
	return ErrInvalidRetention
}

func SizeOptions() []int {
	return []int{NoSizeLimitGB, 1, 5, 10, 25, 50}
}

func ValidateRetentionMaxGB(maxGB int) error {
	for _, option := range SizeOptions() {
		if option == maxGB {
			return nil
		}
	}
	return ErrInvalidRetention
}

type Settings struct {
	RetentionDays      int        `json:"activity_retention_days"`
	RetentionMaxGB     int        `json:"activity_retention_max_gb"`
	LogSizeBytes       int64      `json:"activity_log_size_bytes"`
	LastCleanupAt      *time.Time `json:"activity_last_cleanup_at"`
	LastCleanupRemoved int        `json:"activity_last_cleanup_removed"`
	NextCleanupAt      *time.Time `json:"activity_next_cleanup_at"`
}

func DefaultSettings() Settings {
	return Settings{RetentionDays: DefaultRetentionDays}
}

func (s Settings) HasRetentionLimit() bool {
	return s.RetentionDays != ForeverRetentionDays || s.RetentionMaxGB != NoSizeLimitGB
}

func (s Settings) MaxLogSizeBytes() int64 {
	return int64(s.RetentionMaxGB) * BytesPerGB
}

func (s Settings) CleanupDue(now time.Time) bool {
	todayRun := time.Date(now.Year(), now.Month(), now.Day(), CleanupHour, 0, 0, 0, now.Location())
	if now.Before(todayRun) {
		return false
	}
	return s.LastCleanupAt == nil || s.LastCleanupAt.Before(todayRun)
}

func (s Settings) WithNextCleanup(now time.Time) Settings {
	s.NextCleanupAt = nil
	if !s.HasRetentionLimit() {
		return s
	}
	next := time.Date(now.Year(), now.Month(), now.Day(), CleanupHour, 0, 0, 0, now.Location())
	if !next.After(now) {
		next = time.Date(now.Year(), now.Month(), now.Day()+1, CleanupHour, 0, 0, 0, now.Location())
	}
	s.NextCleanupAt = &next
	return s
}

func ClampCutoff(now time.Time, cutoff time.Time) time.Time {
	newest := now.Add(-KeepRecentHours * time.Hour)
	if cutoff.After(newest) {
		return newest
	}
	return cutoff
}

func GuardCutoff(now time.Time) time.Time {
	return ClampCutoff(now, now)
}

func RetentionCutoff(now time.Time, retentionDays int) time.Time {
	return ClampCutoff(now, now.Add(-time.Duration(retentionDays)*24*time.Hour))
}

type CleanupResult struct {
	Removed int
}