package actor

import (
	"context"
	"io"
	"net/http"

	"google.golang.org/protobuf/proto"
)

type MutationResult[V any] struct {
	Result    V             `json:"result"`
	Mutations []ApplyResult `json:"mutations,omitempty"`
}

type GrainPool[V any] interface {
	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*MutationResult[V], error)
	Get(ctx context.Context, id uint64) (*V, error)
	OwnerHost(id uint64) (Host[V], bool)
	Hostname() string
	TakeOwnership(id uint64)
	// HandleOwnershipChange processes a remote first-touch ownership
	// claim. lastChanges is the parallel []int64 of UnixNano stamps from
	// the announcer; -1 entries fall back to the pre-arbitration
	// "always accept remote" behaviour so mixed-version rollouts
	// remain safe.
	HandleOwnershipChange(host string, ids []uint64, lastChanges []int64) error
	HandleRemoteExpiry(host string, ids []uint64, lastChanges []int64) error
	Negotiate(otherHosts []string)
	GetLocalIds() []uint64
	IsHealthy() bool
	Close()
	IsKnown(string) bool
	RemoveHost(host string)
	AddRemoteHost(host string)
}

// Host abstracts a remote node capable of proxying cart requests.
type Host[V any] interface {
	// AnnounceExpiry broadcasts per-id eviction decisions. lastChanges is
	// a parallel []int64 of UnixNano stamps taken at the moment the
	// grain was dropped from the local cache; it is informational on
	// this path (the receiver just removes the id from its remoteOwners
	// map) but kept in the wire signature for symmetry with
	// AnnounceOwnership.
	AnnounceExpiry(ids []uint64, lastChanges []int64)
	Negotiate(otherHosts []string) ([]string, error)
	Name() string
	Proxy(id uint64, w http.ResponseWriter, r *http.Request, customBody io.Reader) (bool, error)
	Apply(ctx context.Context, id uint64, mutation ...proto.Message) (*MutationResult[V], error)
	Get(ctx context.Context, id uint64) (*V, error)
	GetActorIds() []uint64
	Close() error
	Ping() bool
	IsHealthy() bool
	// AnnounceOwnership broadcasts a first-touch ownership claim.
	// lastChanges is a parallel []int64 of UnixNano stamps of the
	// announcing pod's local grain's GetLastChange() at the moment of
	// broadcast; receivers use it as the first-spawn-wins oracle for
	// concurrent cold-cache first-touch (smaller stamp = older spawn =
	// owns the grain; on equal stamps the lexicographically smaller
	// hostname wins). A stamp of -1 means "no local grain to back this
	// id" — receivers treat that as legacy/no-arbitration and accept
	// the remote claim as before.
	AnnounceOwnership(ownerHost string, ids []uint64, lastChanges []int64)
}