package messaging

import "strings"

// sanitizeSubjectToken replaces NATS-reserved characters in a subject token.
// NATS uses '.' as hierarchy delimiter and '*'/'>' as wildcards.
func sanitizeSubjectToken(s string) string {
	r := strings.NewReplacer(".", "-", "*", "-", ">", "-", " ", "-", "\t", "-", "\n", "-")
	return r.Replace(s)
}

// NATS subject constants for the distributed architecture.
// Following the notetaker pattern: <entity>.<action>

// Job Distribution (Queue Groups — load-balanced, one consumer gets each message)
const (
	SubjectJobsNew      = "jobs.new"
	SubjectMCPCIJobsNew = "jobs.mcp-ci.new"
	SubjectAgentExecute = "agent.execute"
	QueueWorkers        = "workers"
)

// Status Updates (Pub/Sub — all subscribers get every message, for SSE bridging)
// These use parameterized subjects: e.g. SubjectAgentEvents("myagent", "user1")
const (
	subjectAgentEventsPrefix = "agent."
	subjectJobProgressPrefix = "jobs."
	subjectFineTunePrefix    = "finetune."
	subjectGalleryPrefix     = "gallery."
)

// SubjectAgentEvents returns the NATS subject for agent SSE events.
func SubjectAgentEvents(agentName, userID string) string {
	if userID == "" {
		userID = "anonymous"
	}
	return subjectAgentEventsPrefix + sanitizeSubjectToken(agentName) + ".events." + sanitizeSubjectToken(userID)
}

// SubjectJobProgress returns the NATS subject for job progress updates.
func SubjectJobProgress(jobID string) string {
	return subjectJobProgressPrefix + sanitizeSubjectToken(jobID) + ".progress"
}

// SubjectJobResult returns the NATS subject for the final job result (terminal state).
func SubjectJobResult(jobID string) string {
	return subjectJobProgressPrefix + sanitizeSubjectToken(jobID) + ".result"
}

// MCP Tool Execution (Request-Reply via NATS — load-balanced across agent workers)
const (
	SubjectMCPToolExecute = "mcp.tools.execute"
	SubjectMCPDiscovery   = "mcp.discovery"
	QueueAgentWorkers     = "agent-workers"
)

// SubjectFineTuneProgress returns the NATS subject for fine-tune progress.
func SubjectFineTuneProgress(jobID string) string {
	return subjectFineTunePrefix + sanitizeSubjectToken(jobID) + ".progress"
}

// SubjectGalleryProgress returns the NATS subject for gallery download progress.
func SubjectGalleryProgress(opID string) string {
	return subjectGalleryPrefix + sanitizeSubjectToken(opID) + ".progress"
}

// SubjectGalleryOpStart and SubjectGalleryOpEnd are broadcast subjects for the
// in-memory OpCache lifecycle. Frontend replicas publish to these when an
// admin admits a new install/delete (Start) and when an operation is
// dismissed (End), so peer replicas can keep their OpCache in sync without
// hitting PostgreSQL on every UI poll.
const (
	SubjectGalleryOpStart = "gallery.opcache.start"
	SubjectGalleryOpEnd   = "gallery.opcache.end"
)

// Control Signals (Pub/Sub — targeted cancellation)
const (
	subjectJobCancelPrefix      = "jobs."
	subjectAgentCancelPrefix    = "agent."
	subjectFineTuneCancelPrefix = "finetune."
	subjectGalleryCancelPrefix  = "gallery."
)

// Wildcard subjects for NATS subscriptions that match all IDs.
const (
	SubjectJobCancelWildcard       = "jobs.*.cancel"
	SubjectJobResultWildcard       = "jobs.*.result"
	SubjectJobProgressWildcard     = "jobs.*.progress"
	SubjectAgentCancelWildcard     = "agent.*.cancel"
	SubjectGalleryCancelWildcard   = "gallery.*.cancel"
	SubjectGalleryProgressWildcard = "gallery.*.progress"
)

// SubjectJobCancel returns the NATS subject to cancel a running job.
func SubjectJobCancel(jobID string) string {
	return subjectJobCancelPrefix + sanitizeSubjectToken(jobID) + ".cancel"
}

// SubjectAgentCancel returns the NATS subject to cancel agent execution.
func SubjectAgentCancel(agentID string) string {
	return subjectAgentCancelPrefix + sanitizeSubjectToken(agentID) + ".cancel"
}

// SubjectFineTuneCancel returns the NATS subject to stop fine-tuning.
func SubjectFineTuneCancel(jobID string) string {
	return subjectFineTuneCancelPrefix + sanitizeSubjectToken(jobID) + ".cancel"
}

// SubjectGalleryCancel returns the NATS subject to cancel a gallery download.
func SubjectGalleryCancel(opID string) string {
	return subjectGalleryCancelPrefix + sanitizeSubjectToken(opID) + ".cancel"
}

// Node Backend Lifecycle (Pub/Sub — targeted to specific nodes)
//
// These subjects control the backend *process* lifecycle on a serve-backend node,
// mirroring how the local ModelLoader uses startProcess() / deleteProcess().
//
// Model loading (LoadModel gRPC) is done via direct gRPC calls to the node's
// address — no NATS needed for that, same as local mode.
const (
	subjectNodePrefix = "nodes."
)

// SubjectNodeBackendInstall tells a worker node to install a backend and start its gRPC process.
// Uses NATS request-reply: the SmartRouter sends the request, the worker installs
// the backend from gallery (if not already installed), starts the gRPC process,
// and replies when ready.
func SubjectNodeBackendInstall(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.install"
}

// BackendInstallRequest is the payload for a backend.install NATS request.
type BackendInstallRequest struct {
	Backend          string `json:"backend"`
	ModelID          string `json:"model_id,omitempty"`
	BackendGalleries string `json:"backend_galleries,omitempty"`
	// URI is set for external installs (OCI image, URL, or path). When non-empty
	// the worker routes to InstallExternalBackend instead of the gallery lookup.
	URI   string `json:"uri,omitempty"`
	Name  string `json:"name,omitempty"`
	Alias string `json:"alias,omitempty"`
	// ReplicaIndex selects which slot on the worker this load occupies, so two
	// concurrent backend.install requests for the same model land on distinct
	// gRPC processes and ports. Workers older than this field treat it as 0
	// (single-replica behavior — no collision because the controller never
	// asks for replica > 0 on a node whose MaxReplicasPerModel is 1).
	ReplicaIndex int32 `json:"replica_index,omitempty"`
	// Force is retained on the wire only for backward compatibility with
	// pre-2026-05-08 masters that did not know about backend.upgrade. New
	// callers MUST send to SubjectNodeBackendUpgrade instead. Workers continue
	// to honor Force=true here so a rolling update with new master + old
	// worker still works (the master's install fallback path also uses this
	// when backend.upgrade returns nats.ErrNoResponders).
	Force bool `json:"force,omitempty"`
	// OpID identifies the admin-side operation. When non-empty the worker
	// publishes BackendInstallProgressEvent values to
	// SubjectNodeBackendInstallProgress(nodeID, OpID) while the install is
	// running, debounced to roughly 250ms. Empty means the caller is a
	// reconciler-driven retry that does not need progress streamed.
	OpID string `json:"op_id,omitempty"`
}

// BackendInstallReply is the response from a backend.install NATS request.
type BackendInstallReply struct {
	Success bool   `json:"success"`
	Address string `json:"address,omitempty"` // gRPC address of the backend process (host:port)
	Error   string `json:"error,omitempty"`
}

// SubjectNodeBackendUpgrade tells a worker node to force-reinstall a backend
// from the gallery, stop every running process for that backend, and restart.
// Uses NATS request-reply with a long deadline (gallery image pulls can take
// many minutes on slow links). Routine model loads use SubjectNodeBackendInstall
// instead — this subject exists so the slow path doesn't head-of-line-block
// the fast one through a shared subscription goroutine.
func SubjectNodeBackendUpgrade(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.upgrade"
}

// BackendUpgradeRequest is the payload for a backend.upgrade NATS request.
// It is intentionally a strict subset of BackendInstallRequest — there is no
// Force field because the upgrade subject IS the force semantics; no ModelID
// because upgrade is backend-scoped (it stops every replica using the binary
// before re-installing). Per-replica restart happens on the next routine load.
type BackendUpgradeRequest struct {
	Backend          string `json:"backend"`
	BackendGalleries string `json:"backend_galleries,omitempty"`
	URI              string `json:"uri,omitempty"`
	Name             string `json:"name,omitempty"`
	Alias            string `json:"alias,omitempty"`
	// ReplicaIndex is informational — upgrade stops all replicas regardless,
	// but the field lets future per-replica metadata (e.g. progress reporting
	// scoped to a slot) ride the same wire without a v3 type.
	ReplicaIndex int32 `json:"replica_index,omitempty"`
}

// BackendUpgradeReply mirrors BackendInstallReply minus Address — upgrade does
// not start a process, so there is no port to advertise. The subsequent
// routine load will re-bind via backend.install and learn the new address.
type BackendUpgradeReply struct {
	Success bool   `json:"success"`
	Error   string `json:"error,omitempty"`
}

// SubjectNodeBackendList queries a worker node for its installed backends.
// Uses NATS request-reply.
func SubjectNodeBackendList(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.list"
}

// BackendListRequest is the payload for a backend.list NATS request.
type BackendListRequest struct{}

// BackendListReply is the response from a backend.list NATS request.
type BackendListReply struct {
	Backends []NodeBackendInfo `json:"backends"`
	Error    string            `json:"error,omitempty"`
}

// NodeBackendInfo describes a backend installed on a worker node.
type NodeBackendInfo struct {
	Name        string `json:"name"`
	IsSystem    bool   `json:"is_system"`
	IsMeta      bool   `json:"is_meta"`
	InstalledAt string `json:"installed_at,omitempty"`
	GalleryURL  string `json:"gallery_url,omitempty"`
	// Version, URI and Digest enable cluster-wide upgrade detection —
	// without them, the frontend cannot tell whether the installed OCI
	// image matches the gallery entry, and upgrades silently never surface.
	Version string `json:"version,omitempty"`
	URI     string `json:"uri,omitempty"`
	Digest  string `json:"digest,omitempty"`
}

// SubjectNodeBackendStop tells a worker node to stop its gRPC backend process.
// Equivalent to the local deleteProcess(). The node will:
// 1. Best-effort Free() via gRPC
// 2. Kill the backend process
// 3. Can be restarted via another backend.start event.
func SubjectNodeBackendStop(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.stop"
}

// SubjectNodeBackendDelete tells a worker node to delete a backend (stop + remove files).
// Uses NATS request-reply.
func SubjectNodeBackendDelete(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".backend.delete"
}

// BackendDeleteRequest is the payload for a backend.delete NATS request.
type BackendDeleteRequest struct {
	Backend string `json:"backend"`
}

// BackendDeleteReply is the response from a backend.delete NATS request.
type BackendDeleteReply struct {
	Success bool   `json:"success"`
	Error   string `json:"error,omitempty"`
}

// SubjectNodeModelUnload tells a worker node to unload a model (gRPC Free) without killing the backend.
// Uses NATS request-reply.
func SubjectNodeModelUnload(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".model.unload"
}

// ModelUnloadRequest is the payload for a model.unload NATS request.
type ModelUnloadRequest struct {
	ModelName string `json:"model_name"`
	Address   string `json:"address,omitempty"` // gRPC address of the backend process to unload from
}

// ModelUnloadReply is the response from a model.unload NATS request.
type ModelUnloadReply struct {
	Success bool   `json:"success"`
	Error   string `json:"error,omitempty"`
}

// SubjectNodeModelDelete tells a worker node to delete model files from disk.
// Uses NATS request-reply.
func SubjectNodeModelDelete(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".model.delete"
}

// ModelDeleteRequest is the payload for a model.delete NATS request.
type ModelDeleteRequest struct {
	ModelName string `json:"model_name"`
}

// ModelDeleteReply is the response from a model.delete NATS request.
type ModelDeleteReply struct {
	Success bool   `json:"success"`
	Error   string `json:"error,omitempty"`
}

// SubjectNodeStop tells a serve-backend node to shut down entirely
// (deregister + exit). The node will not restart the backend process.
func SubjectNodeStop(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".stop"
}

// File Staging (Request-Reply — targeted to specific nodes)
// These subjects use request-reply for synchronous file operations.

// SubjectNodeFilesEnsure tells a serve-backend node to download an S3 key to its local cache.
// Reply: {local_path, error}
func SubjectNodeFilesEnsure(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".files.ensure"
}

// SubjectNodeFilesStage tells a serve-backend node to upload a local file to S3.
// Reply: {key, error}
func SubjectNodeFilesStage(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".files.stage"
}

// SubjectNodeFilesTemp tells a serve-backend node to allocate a temp file.
// Reply: {local_path, error}
func SubjectNodeFilesTemp(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".files.temp"
}

// SubjectNodeFilesListDir tells a serve-backend node to list files in a directory.
// Reply: {files: [...], error}
func SubjectNodeFilesListDir(nodeID string) string {
	return subjectNodePrefix + sanitizeSubjectToken(nodeID) + ".files.listdir"
}

// Cache Invalidation (Pub/Sub — broadcast to all instances)
const (
	SubjectCacheInvalidateSkills = "cache.invalidate.skills"
	// SubjectCacheInvalidateModels is broadcast by the replica that completed
	// a model install/delete. Peers subscribe and re-run
	// ModelConfigLoader.LoadModelConfigsFromPath so a chat completion routed
	// to a different replica can find the newly installed model.
	SubjectCacheInvalidateModels = "cache.invalidate.models"
	// SubjectCacheInvalidateBackends is broadcast after a backend
	// install/upgrade/delete. Peers retrigger their UpgradeChecker so the
	// 6-hour upgrade-available cache flips to fresh on every replica, not
	// just the one that handled the request.
	SubjectCacheInvalidateBackends = "cache.invalidate.backends"
)

// CacheInvalidateEvent is the payload for cache invalidation broadcasts.
// Element names a specific model/backend when known; empty means "the whole
// set was touched, do a full reload."
type CacheInvalidateEvent struct {
	Element string `json:"element,omitempty"`
	Op      string `json:"op,omitempty"` // "install" | "delete" | "upgrade"
}

// SubjectCacheInvalidateCollection returns the NATS subject for collection cache invalidation.
func SubjectCacheInvalidateCollection(name string) string {
	return "cache.invalidate.collections." + sanitizeSubjectToken(name)
}

// Prefix-Cache Routing Sync (Pub/Sub - broadcast to all frontends)
//
// Frontends share prefix-cache observations so a request routed to any replica
// benefits from the prefix-affinity another replica already learned. This
// mirrors the OpCache live-sync pattern: plain NATS Core pub/sub, no JetStream.
const (
	SubjectPrefixCacheObserve    = "prefixcache.observe"
	SubjectPrefixCacheInvalidate = "prefixcache.invalidate"
)

// PrefixCacheObserveEvent announces that the replica (NodeID, Replica) served a
// request whose prefix chain ends at the given hashes for model. Chain is the
// full shallow-to-deep hash chain so peers can insert the same path. Affinity is
// per replica (a backend process with its own KV cache), not per node, so the
// replica index is carried so peers attribute the observation to the same one.
type PrefixCacheObserveEvent struct {
	Model   string   `json:"model"`
	Chain   []uint64 `json:"chain"`
	NodeID  string   `json:"node_id"`
	Replica int      `json:"replica"`
}

// PrefixCacheInvalidateEvent tells peers to drop entries for a replica. When
// Replica >= 0 it targets the single replica (Model, NodeID, Replica). When
// Replica < 0 it targets ALL replicas of (Model, NodeID), for example when a
// whole node goes offline.
type PrefixCacheInvalidateEvent struct {
	Model   string `json:"model"`
	NodeID  string `json:"node_id"`
	Replica int    `json:"replica"`
}