// Package presence is the F-5b presence-sync loop. Every tick it
// queries the host for each bound agent's sm.Machine state, maps to
// Fabric's 6-status enum, and PUTs diffs to each guild the agent
// belongs to.
//
// Semantic mapping (sm.State → fabric presence) lives in StateToFabric:
//
//	idle    → "idle"      (waiting for work)
//	working → "on_call"   (running a single turn; available to receive)
//	busy    → "busy"      (workflow stacked; do not deliver announce)
//	offline → "offline"   (process down / never booted / rate-limited)
//
// "exhausted" + "unknown" are reserved for backend-side fallbacks; we
// never push them — they'd require info Plexum doesn't track.
//
// Tick model mirrors openclaw's Fabric.OpenclawPlugin.presence-sync.ts:
// 30s ticker, inflight mutex (serial ticks may span multiple seconds
// over many agents + guilds; overlapping ticks cause the backend
// upsert race described in agent-presence.service.ts), and diff-gating
// so we only PUT when state actually changed.
package presence

import (
	"context"
	"sync"
	"time"

	plugin "git.hangman-lab.top/hzhang/Plexum-sdk-go/plugin"

	"git.hangman-lab.top/hzhang/Plexum-fabric-channel-plugin/internal/config"
	"git.hangman-lab.top/hzhang/Plexum-fabric-channel-plugin/internal/fabric"
	"git.hangman-lab.top/hzhang/Plexum-fabric-channel-plugin/internal/identity"
	"git.hangman-lab.top/hzhang/Plexum-fabric-channel-plugin/internal/tokens"
)

// DefaultInterval matches openclaw's 30s cadence. State transitions are
// rare so any longer interval is fine — Fabric backends treat missing
// rows as 'unknown' (not-busy) so a delayed update can't deliver a
// message wrongly, only fail to suppress one.
const DefaultInterval = 30 * time.Second

// Sync drives the presence-sync loop. One instance per plugin process;
// owns the lastStatus diff cache + the inflight mutex.
type Sync struct {
	Host       plugin.HostAPI
	Client     *fabric.Client
	Tokens     *tokens.Cache
	Identities *identity.Registry
	Bindings   []config.FabricBinding
	Interval   time.Duration // ≤0 → DefaultInterval

	mu         sync.Mutex
	lastStatus map[string]string // by agent_id+guild_node_id → fabric status
	inflight   bool
}

// Start launches the ticker; runs until ctx cancels. Fires one tick
// immediately so initial state lands fast.
func (s *Sync) Start(ctx context.Context) {
	if s.Interval <= 0 {
		s.Interval = DefaultInterval
	}
	if s.lastStatus == nil {
		s.lastStatus = map[string]string{}
	}
	go func() {
		t := time.NewTicker(s.Interval)
		defer t.Stop()
		s.tick(ctx)
		for {
			select {
			case <-ctx.Done():
				return
			case <-t.C:
				s.tick(ctx)
			}
		}
	}()
}

// tick runs one presence-sync pass. Skips if a previous tick is still
// running (drop overlapping ticks — see openclaw incident note).
func (s *Sync) tick(ctx context.Context) {
	s.mu.Lock()
	if s.inflight {
		s.mu.Unlock()
		return
	}
	s.inflight = true
	s.mu.Unlock()
	defer func() {
		s.mu.Lock()
		s.inflight = false
		s.mu.Unlock()
	}()

	// Dedupe (agent_id, guild_node_id) pairs across bindings —
	// multiple channels in the same guild for the same agent → one PUT.
	type target struct {
		agentID     string
		guildNodeID string
	}
	seen := map[target]struct{}{}
	for _, b := range s.Bindings {
		key := target{b.AgentID, b.FabricGuildNodeID}
		if _, ok := seen[key]; ok {
			continue
		}
		seen[key] = struct{}{}
		s.syncOne(ctx, b)
	}
}

func (s *Sync) syncOne(ctx context.Context, b config.FabricBinding) {
	entry := s.Identities.Lookup(b.AgentID)
	if entry == nil || !entry.Enabled {
		return
	}
	if entry.FabricUserID == "" {
		// Without the userId we can't PUT. Operator should re-register
		// to populate it; log once and move on.
		s.Host.Log("debug", "fabric presence-sync: no fabric_user_id",
			map[string]any{"agent": b.AgentID})
		return
	}

	snap, err := s.Host.ReadAgentState(ctx, b.AgentID)
	if err != nil {
		s.Host.Log("warn", "fabric presence-sync: ReadAgentState failed",
			map[string]any{"agent": b.AgentID, "err": err.Error()})
		return
	}
	status := StateToFabric(snap.State)
	if status == "" {
		return // unmappable state → skip
	}

	cacheKey := b.AgentID + "|" + b.FabricGuildNodeID
	s.mu.Lock()
	prev, ok := s.lastStatus[cacheKey]
	s.mu.Unlock()
	if ok && prev == status {
		return // no change
	}

	guildToken, err := s.Tokens.GuildToken(ctx, b.AgentID, b.FabricGuildNodeID)
	if err != nil {
		s.Host.Log("warn", "fabric presence-sync: guild token",
			map[string]any{"agent": b.AgentID, "guild": b.FabricGuildNodeID, "err": err.Error()})
		return
	}
	guildEndpoint, err := s.resolveGuildEndpoint(ctx, b.AgentID, b.FabricGuildNodeID)
	if err != nil {
		s.Host.Log("warn", "fabric presence-sync: guild endpoint",
			map[string]any{"agent": b.AgentID, "guild": b.FabricGuildNodeID, "err": err.Error()})
		return
	}

	if err := s.Client.SetAgentPresence(ctx, guildEndpoint, guildToken,
		entry.FabricUserID, status, "plexum-host"); err != nil {
		s.Host.Log("warn", "fabric presence-sync: PUT failed",
			map[string]any{"agent": b.AgentID, "status": status, "err": err.Error()})
		// 401 → token rotated; drop cache so the next tick re-logs in.
		s.Tokens.Invalidate(b.AgentID)
		return
	}
	s.mu.Lock()
	s.lastStatus[cacheKey] = status
	s.mu.Unlock()
	s.Host.Log("info", "fabric presence-sync",
		map[string]any{"agent": b.AgentID, "guild": b.FabricGuildNodeID, "status": status})
}

// resolveGuildEndpoint walks the cached session's guilds list to find
// the endpoint URL matching guildNodeID.
func (s *Sync) resolveGuildEndpoint(ctx context.Context, agentID, guildNodeID string) (string, error) {
	sess, err := s.Tokens.Get(ctx, agentID)
	if err != nil {
		return "", err
	}
	for _, g := range sess.Guilds {
		if g.NodeID == guildNodeID {
			return g.Endpoint, nil
		}
	}
	return "", errGuildNotInSession
}

// errGuildNotInSession is sentinel for resolveGuildEndpoint misses;
// callers log + skip, no retry needed (operator config mismatch).
var errGuildNotInSession = sentinel("agent session has no matching guild")

type sentinel string

func (s sentinel) Error() string { return string(s) }

// StateToFabric maps a Plexum sm.State string to the Fabric agent
// presence enum. Empty return = unmappable (caller skips).
//
//	idle    → "idle"
//	working → "on_call"
//	busy    → "busy"
//	offline → "offline"
//
// Plexum's working == "in a turn, still able to receive" (notifications
// merge with the in-flight turn). HF's "on_call" carried the same
// "active but receptive" meaning, so the mapping is direct.
func StateToFabric(plexumState string) string {
	switch plexumState {
	case "idle":
		return "idle"
	case "working":
		return "on_call"
	case "busy":
		return "busy"
	case "offline":
		return "offline"
	}
	return ""
}