package ownership

import (
	"context"
	"errors"
	"time"
)

var (
	ErrInvalidOwnership     = errors.New("invalid proxy ownership request")
	ErrOwnershipUnavailable = errors.New("proxy is unavailable for ownership")
	ErrAlreadyOwned         = errors.New("proxy is already owned")
	ErrStaleAssignment      = errors.New("proxy ownership assignment is stale")
	ErrNotDraining          = errors.New("proxy ownership is not draining")
	ErrDrainNotReady        = errors.New("proxy still has active or reserved runtime")
	ErrInvalidDrainTicket   = errors.New("invalid drain ticket request")
)

type Assignment struct {
	ProxyID   string
	WorkerID  string
	Epoch     uint64
	Version   uint64
	ExpiresAt time.Time
	Draining  bool
}

// DrainTicket records a pending removal after an ownership assignment enters
// draining. RequiredSnapshotEpoch fences the first complete Worker snapshot
// that may prove the proxy was excluded.
type DrainTicket struct {
	ProxyID               string
	WorkerID              string
	AssignmentEpoch       uint64
	RequiredSnapshotEpoch uint64
}

// DrainTicketStore exposes bounded, Worker-local pending drain tickets. It
// deliberately does not finalize ownership: a later runtime transaction must
// prove both an acknowledged exclusion snapshot and zero live counters.
type DrainTicketStore interface {
	PendingDrains(context.Context, string, int) ([]DrainTicket, error)
}

// Repository is the shared authority for ownership changes. Implementations
// that also support extraction must serialize both operations transactionally.
type Repository interface {
	Assign(context.Context, time.Time, string, string, time.Duration) (Assignment, error)
	Renew(context.Context, time.Time, string, string, uint64, time.Duration) (Assignment, error)
	BeginDrain(context.Context, string, string, uint64) (Assignment, error)
	AcknowledgeDrain(context.Context, string, string, uint64, int64, int64) error
	Get(context.Context, string) (Assignment, bool, error)
	Expire(context.Context, time.Time, int) ([]Assignment, error)
}