package park

import (
	"context"
	"encoding/json"
	"time"

	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/lease"
)

// MoveSweepVerifier verifies the newest retired move's durable fence or
// release, covering every moves/<host> version in the complete census.
// A missing history, unresolved writer, or newer unretired move must refuse.
// The caller supplies the current claim and census; a timestamp alone is not
// evidence. Moves Plan 5 supplies this provider from its retained journals.
type MoveSweepVerifier interface {
	VerifyMovesSweep(context.Context, hostclaim.Observed, []lease.ObjectVersion) (MoveSweepProof, error)
}

type MoveSweepProof struct {
	Host, ClaimETag, MoveID, Incarnation string
	RetiredAt                            time.Time
}

// Check permits listing-time evidence only after the newest retired move's
// verified fence or release. Requiring it before listing starts also excludes
// a retirement racing a paginated listing. The queued EvidenceAt is the end
// of that listing and is retained by every retry.
func (p MoveSweepProof) Check(o hostclaim.Observed, incarnation string, listingStarted time.Time) error {
	if o.Absent || o.Claim == nil || o.ETag == "" || p.Host != o.Host || p.ClaimETag != o.ETag || !token(p.MoveID) || p.Incarnation != incarnation || p.RetiredAt.IsZero() || !p.RetiredAt.Before(listingStarted) {
		return ErrUnsafe
	}
	c := o.Claim
	if c.Free() || c.Op.Kind == hostclaim.KindServing {
		return nil
	}
	if c.Holder == nil && c.Op.Kind == hostclaim.KindParking && c.Op.ID != "" && c.Op.Exec == "" && c.Op.Intent["park_sweep"] == "v1" {
		return nil
	}
	return ErrUnsafe
}

// moveSweepObservation keeps a provider's read-only input detached from the CAS.
func moveSweepObservation(o hostclaim.Observed) (hostclaim.Observed, error) {
	raw, err := json.Marshal(o.Claim)
	if err != nil {
		return hostclaim.Observed{}, err
	}
	var c *hostclaim.Claim
	if err := json.Unmarshal(raw, &c); err != nil {
		return hostclaim.Observed{}, err
	}
	o.Claim = c
	return o, nil
}