package state

import (
	"github.com/hashicorp/consul/acl"
	"github.com/hashicorp/consul/agent/consul/stream"
	"github.com/hashicorp/consul/agent/structs"
	"github.com/hashicorp/consul/proto/private/pbsubscribe"
)

// EventTopicCARoots is the streaming topic to which events will be published
// when the list of active CA Roots changes. Each event payload contains the
// full list of roots.
//
// Note: topics are ordinarily defined in subscribe.proto, but this one isn't
// currently available via the Subscribe endpoint.
const EventTopicCARoots stream.StringTopic = "CARoots"

type EventPayloadCARoots struct {
	CARoots structs.CARoots
}

func (e EventPayloadCARoots) Subject() stream.Subject { return stream.SubjectNone }

func (e EventPayloadCARoots) HasReadPermission(authz acl.Authorizer) bool {
	// Require `service:write` on any service in any partition and namespace.
	var authzContext acl.AuthorizerContext
	structs.WildcardEnterpriseMetaInPartition(structs.WildcardSpecifier).
		FillAuthzContext(&authzContext)

	return authz.ServiceWriteAny(&authzContext) == acl.Allow
}

func (e EventPayloadCARoots) ToSubscriptionEvent(idx uint64) *pbsubscribe.Event {
	panic("EventPayloadCARoots does not implement ToSubscriptionEvent")
}

// caRootsChangeEvents returns an event on EventTopicCARoots whenever the list
// of active CA Roots changes.
func caRootsChangeEvents(tx ReadTxn, changes Changes) ([]stream.Event, error) {
	var rootsChanged bool
	for _, c := range changes.Changes {
		if c.Table == tableConnectCARoots {
			rootsChanged = true
			break
		}
	}
	if !rootsChanged {
		return nil, nil
	}

	_, roots, err := caRootsTxn(tx, nil)
	if err != nil {
		return nil, err
	}

	return []stream.Event{
		{
			Topic:   EventTopicCARoots,
			Index:   changes.Index,
			Payload: EventPayloadCARoots{CARoots: roots},
		},
	}, nil
}

// caRootsSnapshot returns a stream.SnapshotFunc that provides a snapshot of
// the current active list of CA Roots.
func (s *Store) CARootsSnapshot(_ stream.SubscribeRequest, buf stream.SnapshotAppender) (uint64, error) {
	tx := s.db.ReadTxn()
	defer tx.Abort()

	idx, roots, err := caRootsTxn(tx, nil)
	if err != nil {
		return 0, err
	}

	buf.Append([]stream.Event{
		{
			Topic:   EventTopicCARoots,
			Index:   idx,
			Payload: EventPayloadCARoots{CARoots: roots},
		},
	})
	return idx, nil
}