package mesh

import (
	"encoding/json"
	"errors"
	"time"
)

const ProtocolVersion = "mesh-control-v1"

var (
	ErrClusterMismatch               = errors.New("mesh peer cluster mismatch")
	ErrNodeMismatch                  = errors.New("mesh peer node mismatch")
	ErrForwardDisabled               = errors.New("production payload forwarding is disabled by mesh production gate")
	ErrForwardRuntimeUnavailable     = errors.New("production mesh forwarding runtime is unavailable for this route or stage")
	ErrForwardPeerUnavailable        = errors.New("production mesh next peer is unavailable")
	ErrForwardEnvelopeInvalid        = errors.New("production mesh envelope is invalid")
	ErrForwardObservationFailed      = errors.New("production mesh envelope observation failed")
	ErrMeshRuntimeDisabled           = errors.New("mesh synthetic runtime is disabled")
	ErrUnsupportedSyntheticMessage   = errors.New("unsupported synthetic mesh message")
	ErrRouteIDRequired               = errors.New("mesh synthetic route id is required")
	ErrRouteNotFound                 = errors.New("mesh synthetic route not found")
	ErrInvalidRoutePath              = errors.New("mesh synthetic route path is invalid")
	ErrRouteExpired                  = errors.New("mesh synthetic route is expired")
	ErrTTLExhausted                  = errors.New("mesh synthetic route ttl exhausted")
	ErrLoopDetected                  = errors.New("mesh synthetic route loop detected")
	ErrUnauthorizedChannel           = errors.New("mesh synthetic channel is not authorized")
	ErrSyntheticPeerUnavailable      = errors.New("mesh synthetic next peer is unavailable")
	ErrNoHealthySyntheticRoute       = errors.New("mesh synthetic no healthy route available")
	ErrSyntheticRelayQueueFull       = errors.New("mesh synthetic relay queue is full")
	ErrSyntheticRelayQueueEmpty      = errors.New("mesh synthetic relay queue is empty")
	ErrSyntheticPayloadTooLarge      = errors.New("mesh synthetic payload is too large")
	ErrSyntheticOrganizationMismatch = errors.New("mesh synthetic organization mismatch")
	ErrUnsupportedSyntheticService   = errors.New("unsupported synthetic test service")
	ErrSyntheticRequestInvalid       = errors.New("mesh synthetic request is invalid")
)

const (
	SyntheticMessageProbe          = "fabric.probe"
	SyntheticMessageProbeAck       = "fabric.probe_ack"
	SyntheticMessageRouteHealth    = "fabric.route_health"
	SyntheticMessageRouteHealthAck = "fabric.route_health_ack"
	SyntheticMessageTelemetry      = "fabric.telemetry"
	SyntheticMessageTestService    = "fabric.test_service"
	SyntheticMessageTestServiceAck = "fabric.test_service_ack"

	SyntheticTestServiceType            = "synthetic.echo"
	SyntheticDefaultTestOrganizationID  = "org-test"
	SyntheticDefaultMaxTestPayloadBytes = 4096

	SyntheticChannelFabricControl = "fabric_control"
	SyntheticChannelRouteControl  = "route_control"
	SyntheticChannelTelemetry     = "telemetry"

	SyntheticRouteStateUnknown  = "unknown"
	SyntheticRouteStateHealthy  = "healthy"
	SyntheticRouteStateDegraded = "degraded"
	SyntheticRouteStateFailed   = "failed"

	ProductionChannelFabricControl    = "fabric_control"
	ProductionMessageFabricControl    = "fabric.control"
	MaxProductionEnvelopePayloadBytes = 4096
	MaxProductionEnvelopeFutureSkew   = time.Minute
)

type PeerIdentity struct {
	ClusterID string `json:"cluster_id"`
	NodeID    string `json:"node_id"`
}

type SyntheticRoute struct {
	RouteID              string    `json:"route_id"`
	ClusterID            string    `json:"cluster_id"`
	SourceNodeID         string    `json:"source_node_id"`
	DestinationNodeID    string    `json:"destination_node_id"`
	Hops                 []string  `json:"hops"`
	AllowedChannels      []string  `json:"allowed_channels"`
	ExpiresAt            time.Time `json:"expires_at"`
	MaxTTL               int       `json:"max_ttl"`
	MaxHops              int       `json:"max_hops"`
	RouteVersion         string    `json:"route_version,omitempty"`
	PolicyVersion        string    `json:"policy_version,omitempty"`
	PeerDirectoryVersion string    `json:"peer_directory_version,omitempty"`
}

type SyntheticEnvelope struct {
	ProtocolVersion string          `json:"protocol_version"`
	RouteID         string          `json:"route_id"`
	ClusterID       string          `json:"cluster_id"`
	From            PeerIdentity    `json:"from"`
	To              PeerIdentity    `json:"to"`
	Channel         string          `json:"channel"`
	MessageType     string          `json:"message_type"`
	TTL             int             `json:"ttl"`
	HopCount        int             `json:"hop_count"`
	Visited         []string        `json:"visited"`
	Sequence        uint64          `json:"sequence"`
	SentAt          time.Time       `json:"sent_at"`
	Payload         json.RawMessage `json:"payload,omitempty"`
}

type SyntheticProbePayload struct {
	ProbeID string    `json:"probe_id"`
	SentAt  time.Time `json:"sent_at"`
}

type SyntheticProbeAckPayload struct {
	ProbeID    string    `json:"probe_id"`
	Path       []string  `json:"path"`
	AcceptedAt time.Time `json:"accepted_at"`
}

type SyntheticRouteObservation struct {
	RouteID              string    `json:"route_id"`
	State                string    `json:"state"`
	LastSuccessAt        time.Time `json:"last_success_at,omitempty"`
	LastFailureAt        time.Time `json:"last_failure_at,omitempty"`
	LastFailureReason    string    `json:"last_failure_reason,omitempty"`
	SuccessCount         uint64    `json:"success_count"`
	FailureCount         uint64    `json:"failure_count"`
	LastLatencyMs        int64     `json:"last_latency_ms,omitempty"`
	RouteVersion         string    `json:"route_version,omitempty"`
	PolicyVersion        string    `json:"policy_version,omitempty"`
	PeerDirectoryVersion string    `json:"peer_directory_version,omitempty"`
}

type SyntheticRouteHealthResult struct {
	RequestedRouteID string                    `json:"requested_route_id"`
	SelectedRouteID  string                    `json:"selected_route_id"`
	FallbackUsed     bool                      `json:"fallback_used"`
	Ack              SyntheticEnvelope         `json:"ack"`
	Observation      SyntheticRouteObservation `json:"observation"`
}

type SyntheticTestServiceRequest struct {
	RequestID      string    `json:"request_id"`
	OrganizationID string    `json:"organization_id"`
	ServiceType    string    `json:"service_type"`
	Payload        string    `json:"payload"`
	SentAt         time.Time `json:"sent_at"`
}

type SyntheticTestServiceResponse struct {
	RequestID      string    `json:"request_id"`
	OrganizationID string    `json:"organization_id"`
	ServiceType    string    `json:"service_type"`
	EchoPayload    string    `json:"echo_payload"`
	Path           []string  `json:"path"`
	AcceptedAt     time.Time `json:"accepted_at"`
}

type SyntheticTestServiceResult struct {
	RequestedRouteID string                       `json:"requested_route_id"`
	SelectedRouteID  string                       `json:"selected_route_id"`
	FallbackUsed     bool                         `json:"fallback_used"`
	Ack              SyntheticEnvelope            `json:"ack"`
	Response         SyntheticTestServiceResponse `json:"response"`
	Observation      SyntheticRouteObservation    `json:"observation"`
}

type SyntheticRouteCacheVersion struct {
	RouteVersion         string `json:"route_version,omitempty"`
	PolicyVersion        string `json:"policy_version,omitempty"`
	PeerDirectoryVersion string `json:"peer_directory_version,omitempty"`
}

type SyntheticRelayQueuePolicy struct {
	Channel   string `json:"channel"`
	Capacity  int    `json:"capacity"`
	Droppable bool   `json:"droppable"`
}

type SyntheticRelayEnqueueResult struct {
	Channel          string `json:"channel"`
	QueueDepth       int    `json:"queue_depth"`
	QueueCapacity    int    `json:"queue_capacity"`
	Dropped          bool   `json:"dropped"`
	DroppedSequence  uint64 `json:"dropped_sequence,omitempty"`
	AcceptedSequence uint64 `json:"accepted_sequence"`
}

type SyntheticRelayQueueMetrics struct {
	Enqueued         uint64         `json:"enqueued"`
	Dequeued         uint64         `json:"dequeued"`
	Dropped          uint64         `json:"dropped"`
	Rejected         uint64         `json:"rejected"`
	LastRejectReason string         `json:"last_reject_reason,omitempty"`
	QueueDepths      map[string]int `json:"queue_depths"`
}

type HealthMessage struct {
	ProtocolVersion string       `json:"protocol_version"`
	From            PeerIdentity `json:"from"`
	To              PeerIdentity `json:"to"`
	ObservedAt      time.Time    `json:"observed_at"`
	LinkStatus      string       `json:"link_status"`
	LatencyMs       *int         `json:"latency_ms,omitempty"`
	QualityScore    *int         `json:"quality_score,omitempty"`
}

type HealthAck struct {
	ProtocolVersion string       `json:"protocol_version"`
	Accepted        bool         `json:"accepted"`
	By              PeerIdentity `json:"by"`
}

type ProductionEnvelope struct {
	FabricProtocolVersion string          `json:"fabric_protocol_version"`
	MessageID             string          `json:"message_id"`
	RouteID               string          `json:"route_id"`
	ClusterID             string          `json:"cluster_id"`
	SourceNodeID          string          `json:"source_node_id"`
	DestinationNodeID     string          `json:"destination_node_id"`
	CurrentHopNodeID      string          `json:"current_hop_node_id"`
	NextHopNodeID         string          `json:"next_hop_node_id"`
	RoutePath             []string        `json:"route_path,omitempty"`
	VisitedNodeIDs        []string        `json:"visited_node_ids,omitempty"`
	ChannelClass          string          `json:"channel_class"`
	MessageType           string          `json:"message_type"`
	TTL                   int             `json:"ttl"`
	HopCount              int             `json:"hop_count"`
	CreatedAt             time.Time       `json:"created_at"`
	ExpiresAt             time.Time       `json:"expires_at"`
	PayloadLength         int             `json:"payload_length"`
	PayloadHash           string          `json:"payload_hash"`
	Payload               json.RawMessage `json:"payload,omitempty"`
}

type ProductionEnvelopeObservation struct {
	MessageID         string    `json:"message_id"`
	RouteID           string    `json:"route_id"`
	ClusterID         string    `json:"cluster_id"`
	SourceNodeID      string    `json:"source_node_id"`
	DestinationNodeID string    `json:"destination_node_id"`
	CurrentHopNodeID  string    `json:"current_hop_node_id"`
	NextHopNodeID     string    `json:"next_hop_node_id"`
	RoutePath         []string  `json:"route_path,omitempty"`
	VisitedNodeIDs    []string  `json:"visited_node_ids,omitempty"`
	ChannelClass      string    `json:"channel_class"`
	MessageType       string    `json:"message_type"`
	TTL               int       `json:"ttl"`
	HopCount          int       `json:"hop_count"`
	PayloadLength     int       `json:"payload_length"`
	PayloadHash       string    `json:"payload_hash"`
	ObservedAt        time.Time `json:"observed_at"`
}

type ProductionForwardResult struct {
	Accepted   bool         `json:"accepted"`
	Delivered  bool         `json:"delivered"`
	Forwarded  bool         `json:"forwarded"`
	By         PeerIdentity `json:"by"`
	MessageID  string       `json:"message_id"`
	RouteID    string       `json:"route_id"`
	NextNodeID string       `json:"next_node_id,omitempty"`
}

type ProductionForwardLogEntry struct {
	Event             string    `json:"event"`
	RouteID           string    `json:"route_id,omitempty"`
	MessageID         string    `json:"message_id,omitempty"`
	ClusterID         string    `json:"cluster_id,omitempty"`
	LocalNodeID       string    `json:"local_node_id,omitempty"`
	SourceNodeID      string    `json:"source_node_id,omitempty"`
	DestinationNodeID string    `json:"destination_node_id,omitempty"`
	CurrentHopNodeID  string    `json:"current_hop_node_id,omitempty"`
	NextHopNodeID     string    `json:"next_hop_node_id,omitempty"`
	ChannelClass      string    `json:"channel_class,omitempty"`
	MessageType       string    `json:"message_type,omitempty"`
	Reason            string    `json:"reason,omitempty"`
	StatusCode        int       `json:"status_code,omitempty"`
	TTL               int       `json:"ttl,omitempty"`
	HopCount          int       `json:"hop_count,omitempty"`
	RoutePathLength   int       `json:"route_path_length,omitempty"`
	VisitedCount      int       `json:"visited_count,omitempty"`
	PayloadLength     int       `json:"payload_length,omitempty"`
	OccurredAt        time.Time `json:"occurred_at"`
}

func ValidatePeer(local PeerIdentity, remote PeerIdentity) error {
	if local.ClusterID == "" || remote.ClusterID == "" || local.ClusterID != remote.ClusterID {
		return ErrClusterMismatch
	}
	if remote.NodeID == "" {
		return ErrNodeMismatch
	}
	return nil
}