// Package inbound is the Fabric → Plexum message pump. For each
// (agent, guild) it maintains a long-lived socket.io connection to the
// guild's /realtime namespace, joins every channel the agent has
// membership in (resyncing periodically + on push events), and dispatches
// matching message.created events through a per-channel serial queue.
//
// Wakeup gate matches openclaw's plugin: dispatch iff
//   - m.xType == "dm" (any non-self message), OR
//   - m.wakeup == true.
//
// Other inbounds (non-dm with wakeup != true) are dropped silently
// (Plexum has no "record-only history injection" equivalent in v1;
// future phase can add it).
package inbound

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"sync"
	"time"

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

// ChannelSyncInterval is how often the supervisor diffs joined channels
// against /api/channels to catch newly-membership-bestowed channels
// that arrived without a push event. Matches openclaw's 60s.
const ChannelSyncInterval = 60 * time.Second

// ReconnectBackoffInitial / Max / Factor drive exponential backoff
// between reconnect attempts. Starts at 1s, doubles up to 60s; resets
// on successful connect (signalled by connectOnce returning after at
// least one event was received — proxied via wall-clock duration).
const (
	ReconnectBackoffInitial = 1 * time.Second
	ReconnectBackoffMax     = 60 * time.Second
	ReconnectBackoffFactor  = 2.0
	// ReconnectResetAfter: if the previous connection survived at least
	// this long, reset the backoff to Initial (we made meaningful
	// progress; transient drop, not a flapping-failure loop).
	ReconnectResetAfter = 30 * time.Second
)

// Notifier pushes one inbound message to the Plexum host. The plugin
// main wires this to HostAPI.EmitNotification. media items are
// passed through as `media` field in the channel-inbound notification
// (Plexum's channel manager turns them into canonical.ImageBlock
// content on the user message).
type Notifier func(channelName, message, sessionID string, media []MediaItem)

// MediaItem is one attachment file already downloaded to a local path.
// Mirrors the host's channel.MediaRef wire shape (path/media_type/name).
type MediaItem struct {
	Path      string
	MediaType string
	Name      string
}

// Supervisor owns the per-(agent, guild) socket.io connections. Run
// blocks until ctx is cancelled.
type Supervisor struct {
	Client      *fabric.Client
	Tokens      *tokens.Cache
	Bindings    []config.FabricBinding
	ByFabric    config.ByFabricChannel // (guild_node, channel_id) → binding
	AgentIDs    []string               // unique agents to bring up
	Notify      Notifier
	Logger      *slog.Logger
	// Attachments, if non-nil, downloads message attachments to a temp
	// dir and appends paths to the message body before notify. nil →
	// attachments are dropped silently (warning logged).
	Attachments *attachments.Downloader

	// Deduplicate (agentID, messageId) → already dispatched. Bounded
	// to ~5000 entries (matches openclaw).
	dedupMu sync.Mutex
	seen    map[string]struct{}

	// Per-channel serial chain: each channel id maps to a chan of
	// queued task funcs. Channel goroutine drains them in order.
	chainMu sync.Mutex
	chains  map[string]chan func()
}

// New constructs a Supervisor with deduped agentIDs derived from bindings.
func New(client *fabric.Client, tokenCache *tokens.Cache, bindings []config.FabricBinding,
	notify Notifier, logger *slog.Logger) *Supervisor {
	agentSet := map[string]struct{}{}
	for _, b := range bindings {
		agentSet[b.AgentID] = struct{}{}
	}
	agents := make([]string, 0, len(agentSet))
	for a := range agentSet {
		agents = append(agents, a)
	}
	return &Supervisor{
		Client: client, Tokens: tokenCache,
		Bindings: bindings, ByFabric: config.Index(bindings),
		AgentIDs: agents, Notify: notify, Logger: logger,
		seen:   map[string]struct{}{},
		chains: map[string]chan func(){},
	}
}

// Run blocks: spawns one goroutine per (agent, guild) socket.io
// supervisor. Each supervisor reconnects on drop until ctx cancels.
// Returns when ctx is cancelled and all supervisors have exited.
func (s *Supervisor) Run(ctx context.Context) error {
	var wg sync.WaitGroup
	for _, agentID := range s.AgentIDs {
		sess, err := s.Tokens.Get(ctx, agentID)
		if err != nil {
			s.Logger.Warn("inbound: skip agent (no session)", "agent", agentID, "err", err)
			continue
		}
		for _, g := range sess.Guilds {
			if g.Endpoint == "" {
				continue
			}
			wg.Add(1)
			go func(agentID string, guild fabric.GuildInfo) {
				defer wg.Done()
				s.runAgentGuild(ctx, agentID, guild)
			}(agentID, g)
		}
	}
	wg.Wait()
	return nil
}

// runAgentGuild keeps one socket.io connection alive for (agent, guild)
// until ctx cancels. Reconnects with fresh auth on every drop using
// exponential backoff (resets if the previous session survived long
// enough to look healthy).
func (s *Supervisor) runAgentGuild(ctx context.Context, agentID string, guild fabric.GuildInfo) {
	logger := s.Logger.With("agent", agentID, "guild", guild.NodeID)
	backoff := ReconnectBackoffInitial
	for {
		if err := ctx.Err(); err != nil {
			return
		}
		startedAt := time.Now()
		err := s.connectOnce(ctx, agentID, guild, logger)
		if ctx.Err() != nil {
			return
		}
		// Reset backoff if the prior session was meaningfully long
		// (proxy for "we connected + did work" — not a flap loop).
		if time.Since(startedAt) > ReconnectResetAfter {
			backoff = ReconnectBackoffInitial
		}
		errStr := "(nil)"
		if err != nil {
			errStr = err.Error()
		}
		logger.Warn("inbound: socket ended; reconnecting",
			"err", errStr, "backoff", backoff.String())
		select {
		case <-time.After(backoff):
		case <-ctx.Done():
			return
		}
		backoff = time.Duration(float64(backoff) * ReconnectBackoffFactor)
		if backoff > ReconnectBackoffMax {
			backoff = ReconnectBackoffMax
		}
	}
}

// connectOnce opens one socket connection, runs the read loop, and
// returns the terminating error (nil on graceful close).
func (s *Supervisor) connectOnce(ctx context.Context, agentID string, guild fabric.GuildInfo, logger *slog.Logger) error {
	authFn := func(authCtx context.Context) (map[string]any, error) {
		// Always fetch a fresh token before the CONNECT — fixes the
		// stale-JWT-on-reconnect bug openclaw documented.
		s.Tokens.Invalidate(agentID)
		tok, err := s.Tokens.GuildToken(authCtx, agentID, guild.NodeID)
		if err != nil {
			return nil, err
		}
		return map[string]any{"token": tok}, nil
	}
	cli, err := socketio.New(guild.Endpoint, "/socket.io/", "/realtime", authFn)
	if err != nil {
		return err
	}

	// Tracked subscriptions for this connection. Cleared on each
	// reconnect (server forgets join_channel state).
	joined := map[string]struct{}{}
	var joinedMu sync.Mutex

	// Initial sync + periodic resync runs in a goroutine; it reads
	// channels from REST and emits join_channel for new + leave_channel
	// for gone.
	syncCtx, cancelSync := context.WithCancel(ctx)
	defer cancelSync()
	syncOnce := func(kind string) {
		tok, err := s.Tokens.GuildToken(syncCtx, agentID, guild.NodeID)
		if err != nil {
			logger.Warn("inbound: sync token", "err", err)
			return
		}
		channels, err := s.Client.ListChannels(syncCtx, guild.Endpoint, tok, guild.NodeID)
		if err != nil {
			logger.Warn("inbound: list channels", "err", err)
			return
		}
		current := map[string]struct{}{}
		for _, c := range channels {
			current[c.ID] = struct{}{}
		}
		var added, removed int
		joinedMu.Lock()
		for id := range current {
			if _, ok := joined[id]; !ok {
				_ = cli.Emit(syncCtx, "join_channel", map[string]any{"channelId": id})
				joined[id] = struct{}{}
				added++
			}
		}
		for id := range joined {
			if _, ok := current[id]; !ok {
				_ = cli.Emit(syncCtx, "leave_channel", map[string]any{"channelId": id})
				delete(joined, id)
				removed++
			}
		}
		size := len(joined)
		joinedMu.Unlock()
		if kind == "initial" {
			logger.Info("inbound: channels joined", "n", size)
		} else if added > 0 || removed > 0 {
			logger.Info("inbound: channels resync", "added", added, "removed", removed, "now", size)
		}
	}

	// Event handlers. Registered BEFORE Connect so we don't miss the
	// first events the server pushes right after handshake.
	cli.On("connect", func([]json.RawMessage) { /* no-op; server CONNECT ack */ })

	cli.On("channel.joined", func(args []json.RawMessage) {
		var evt struct {
			ChannelID string `json:"channelId"`
		}
		if len(args) == 0 {
			return
		}
		_ = json.Unmarshal(args[0], &evt)
		if evt.ChannelID == "" {
			return
		}
		joinedMu.Lock()
		if _, already := joined[evt.ChannelID]; already {
			joinedMu.Unlock()
			return
		}
		joined[evt.ChannelID] = struct{}{}
		joinedMu.Unlock()
		_ = cli.Emit(syncCtx, "join_channel", map[string]any{"channelId": evt.ChannelID})
		logger.Info("inbound: channel.joined push", "channel", evt.ChannelID)
	})

	cli.On("channel.left", func(args []json.RawMessage) {
		var evt struct {
			ChannelID string `json:"channelId"`
		}
		if len(args) == 0 {
			return
		}
		_ = json.Unmarshal(args[0], &evt)
		if evt.ChannelID == "" {
			return
		}
		joinedMu.Lock()
		if _, present := joined[evt.ChannelID]; !present {
			joinedMu.Unlock()
			return
		}
		delete(joined, evt.ChannelID)
		joinedMu.Unlock()
		_ = cli.Emit(syncCtx, "leave_channel", map[string]any{"channelId": evt.ChannelID})
		logger.Info("inbound: channel.left push", "channel", evt.ChannelID)
	})

	// Capture self user id from current cached session for the
	// self-author filter.
	sess := s.Tokens.Peek(agentID)
	var selfUserID string
	if sess != nil {
		selfUserID = sess.User.ID
	}

	cli.On("message.created", func(args []json.RawMessage) {
		var m FabricMessage
		if len(args) == 0 {
			return
		}
		if err := json.Unmarshal(args[0], &m); err != nil {
			logger.Warn("inbound: bad message.created", "err", err)
			return
		}
		s.dispatch(agentID, guild.NodeID, guild.Endpoint, selfUserID, &m, logger)
	})

	// Periodic resync goroutine.
	syncTimer := time.NewTicker(ChannelSyncInterval)
	defer syncTimer.Stop()
	go func() {
		// Wait for connect to complete; we kick the initial sync from
		// within Connect's startup. Use the ticker for the periodic.
		for {
			select {
			case <-syncCtx.Done():
				return
			case <-syncTimer.C:
				syncOnce("resync")
			}
		}
	}()

	// On connect, fire the initial sync. The socketio client doesn't
	// fire a Go-side "connect" event before Connect returns; we
	// schedule the initial sync to run shortly after Connect starts.
	go func() {
		time.Sleep(100 * time.Millisecond)
		select {
		case <-syncCtx.Done():
			return
		default:
		}
		syncOnce("initial")
	}()

	return cli.Connect(ctx)
}

// dispatch applies self-author filter, dedup, channel-binding lookup,
// wakeup gate, then notifies Plexum.
func (s *Supervisor) dispatch(agentID, guildNodeID, guildEndpoint, selfUserID string, m *FabricMessage, logger *slog.Logger) {
	if m.ChannelID == "" {
		return
	}
	// Self-author filter: skip messages this user wrote.
	if m.AuthorUserID != "" && m.AuthorUserID == selfUserID {
		return
	}
	// Dedup per (agent, messageId).
	key := agentID + ":" + m.MessageID
	s.dedupMu.Lock()
	if _, dup := s.seen[key]; dup {
		s.dedupMu.Unlock()
		return
	}
	s.seen[key] = struct{}{}
	if len(s.seen) > 5000 {
		s.seen = map[string]struct{}{} // simple bounded reset
	}
	s.dedupMu.Unlock()

	// Channel-binding lookup. We only deliver messages for channels
	// the operator has bound to a Plexum agent in channels/*.json.
	binding, ok := s.ByFabric[config.Key(guildNodeID, m.ChannelID)]
	if !ok {
		return
	}
	// The binding must point at THIS agent (a guild may have several
	// agents; an inbound on agent A's socket for a channel bound to
	// agent B is ignored — agent B has their own socket for it).
	if binding.AgentID != agentID {
		return
	}

	// Wakeup gate (decision #36-equivalent on the openclaw side):
	//   dm channel → always deliver
	//   other      → wakeup must be true
	if m.XType != "dm" && !m.Wakeup {
		logger.Debug("inbound: skip (no wakeup)",
			"channel", m.ChannelID, "agent", agentID, "msg", m.MessageID)
		return
	}

	logger.Info("inbound: dispatch",
		"channel", m.ChannelID, "agent", agentID, "msg", m.MessageID, "xtype", m.XType,
		"attachments", len(m.Attachments))

	// Per-channel serial queue. Concurrent inbounds on the same channel
	// must run one at a time so Plexum's state machine sees clean turns.
	sessionID := "s_fab_" + m.ChannelID
	body := m.Content
	plexumChannel := binding.PlexumChannelName
	var media []MediaItem
	// Download attachments to local paths so the host can hand them
	// to provider plugins as canonical.ImageBlock (Plexum host-side
	// media block support).
	if len(m.Attachments) > 0 && s.Attachments != nil {
		tok, terr := s.Tokens.GuildToken(context.Background(), agentID, guildNodeID)
		if terr == nil {
			refs := make([]attachments.AttachmentRef, len(m.Attachments))
			for i, a := range m.Attachments {
				// Fabric returns attachment URLs as RELATIVE paths
				// (`/api/files/<id>`); resolve against the guild endpoint
				// before fetching.
				absURL := a.URL
				if absURL != "" && absURL[0] == '/' {
					absURL = guildEndpoint + absURL
				}
				refs[i] = attachments.AttachmentRef{
					URL: absURL, Name: a.Name, MimeType: a.MimeType,
				}
			}
			files := s.Attachments.FetchAll(context.Background(), tok, m.MessageID, refs)
			for _, f := range files {
				media = append(media, MediaItem{
					Path: f.LocalPath, MediaType: f.MimeType, Name: f.Name,
				})
			}
			if len(files) < len(refs) {
				logger.Warn("inbound: some attachments failed to download",
					"requested", len(refs), "got", len(files))
			}
		} else {
			logger.Warn("inbound: attachment guild token failed", "err", terr)
		}
	}
	s.enqueueChannel(m.ChannelID, func() {
		s.Notify(plexumChannel, body, sessionID, media)
	})
}

// enqueueChannel chains a task onto the per-channel queue. If no chain
// exists, spawn the drain goroutine. Drain goroutine exits when the
// channel goes idle for >5s to avoid leaking goroutines per channel.
func (s *Supervisor) enqueueChannel(channelID string, task func()) {
	s.chainMu.Lock()
	ch, ok := s.chains[channelID]
	if !ok {
		ch = make(chan func(), 32)
		s.chains[channelID] = ch
		go s.drainChannel(channelID, ch)
	}
	s.chainMu.Unlock()
	select {
	case ch <- task:
	default:
		// Backlog full (32+) — log + drop. Shouldn't happen unless
		// the bound agent is hopelessly behind.
		s.Logger.Warn("inbound: per-channel queue full; dropping",
			"channel", channelID)
	}
}

func (s *Supervisor) drainChannel(channelID string, ch chan func()) {
	idle := time.NewTimer(5 * time.Second)
	defer idle.Stop()
	for {
		select {
		case task, open := <-ch:
			if !open {
				return
			}
			if !idle.Stop() {
				<-idle.C
			}
			task()
			idle.Reset(5 * time.Second)
		case <-idle.C:
			s.chainMu.Lock()
			delete(s.chains, channelID)
			s.chainMu.Unlock()
			return
		}
	}
}

// FabricMessage is the wire shape of Fabric's message.created event.
// Mirror of FabricMessage type in openclaw's inbound.ts.
type FabricMessage struct {
	MessageID    string             `json:"messageId"`
	Seq          int                `json:"seq"`
	Content      string             `json:"content"`
	AuthorUserID string             `json:"authorUserId,omitempty"`
	CreatedAt    string             `json:"createdAt,omitempty"`
	ChannelID    string             `json:"channelId,omitempty"`
	Attachments  []FabricAttachment `json:"attachments,omitempty"`
	Wakeup       bool               `json:"wakeup,omitempty"`
	// XType matches the Fabric channel's x-type field. 'dm' bypasses
	// the wakeup gate.
	XType string `json:"xType,omitempty"`
}

// FabricAttachment is the wire shape of one attachment ref. v1
// (Phase F-2) doesn't download these; F-8 will.
type FabricAttachment struct {
	URL      string `json:"url"`
	Name     string `json:"name,omitempty"`
	MimeType string `json:"mimeType,omitempty"`
}

// Equality check used for tests.
func (a FabricAttachment) Equal(b FabricAttachment) bool {
	return a.URL == b.URL && a.Name == b.Name && a.MimeType == b.MimeType
}

// Sanity: ensure FabricMessage stays serializable.
var _ = fmt.Sprint