engine

type Engine interface {
	// Burns down all grants in the defined period by the usage amounts.
	//
	// When the engine outputs a balance, it doesn't discriminate what should be in that balance.
	// If a grant is inactive at the end of the period, it will still be in the output.
	Run(ctx context.Context, params RunParams) (RunResult, error)
}

type EngineConfig struct {
	Granularity meter.WindowSize
	QueryUsage  QueryUsageFn
}

type GrantBurnDownHistory struct {
	// contains filtered or unexported fields
}

type GrantBurnDownHistorySegment struct {
	timeutil.ClosedPeriod
	BalanceAtStart     balance.Map
	TerminationReasons SegmentTerminationReason // Reason why the segment was terminated (could be multiple taking effect at same time)
	TotalUsage         float64                  // Total usage of the feature in the Period
	OverageAtStart     float64                  // Usage beyond what could be burnt down from the grants in the previous segment (if any)
	Overage            float64                  // Usage beyond what cloud be burnt down from the grants
	GrantUsages        []GrantUsage             // Grant usages in the segment order by grant priority
}

type GrantUsage struct {
	GrantID           string
	Usage             float64
	TerminationReason GrantUsageTerminationReason
}

type GrantUsageTerminationReason string

type QueryUsageFn func(ctx context.Context, from, to time.Time) (float64, error)

type RunParams struct {
	// List of all grants that are active at the relevant period at some point.
	Grants []grant.Grant
	// End of the period to burn down the grants for.
	Until time.Time
	// Starting snapshot of the balances at the START OF THE PERIOD.
	StartingSnapshot balance.Snapshot
	// ResetBehavior defines the behavior of the engine when a reset is encountered.
	ResetBehavior grant.ResetBehavior
	// Timeline of the resets that occurred in the period.
	// The resets must occur AFTER the starting snapshot and NOT AFTER the until time. (exclusive - inclusive)
	Resets timeutil.SimpleTimeline
}

type RunResult struct {
	// Snapshot of the balances at the END OF THE PERIOD.
	Snapshot balance.Snapshot
	// History of the grant burn down.
	History GrantBurnDownHistory
}

type SegmentTerminationReason struct {
	PriorityChange bool
	Recurrence     []string // Grant IDs
	UsageReset     bool
}