package qq_obv11

// This file holds the message-flow half of the Adapter: the inbound read loop
// (server/client mode sessions, reconnect, dispatch) and the outbound send path
// (rate limit, chunk to the connection). It is split out of adapter.go to keep
// each file under the project's 500-line limit.

import (
	"context"
	"fmt"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/adapter"
)

// ReadMessages registers emit as the pull-based sink and blocks until ctx is
// canceled. Inbound events arrive via the read loop and are dispatched to
// SetMessageHandler (push) when set, otherwise to emit.
func (a *Adapter) ReadMessages(ctx context.Context, emit func(adapter.UnifiedMessage)) {
	a.emitMu.Lock()
	a.emit = emit
	a.emitMu.Unlock()
	defer func() {
		a.emitMu.Lock()
		a.emit = nil
		a.emitMu.Unlock()
	}()
	<-ctx.Done()
}

// SendMessage delivers a reply (possibly several messages) to the channel,
// subject to the send rate limit.
func (a *Adapter) SendMessage(ctx context.Context, resp adapter.UnifiedResponse) error {
	if err := ctx.Err(); err != nil {
		return fmt.Errorf("qq-obv11: send message: %w", err)
	}
	conn := a.currentConn()
	if conn == nil {
		return fmt.Errorf("qq-obv11: send message: %w", adapter.ErrNotConnected)
	}
	for i, msg := range resp.Messages {
		if err := a.sendMessage(ctx, conn, msg); err != nil {
			return fmt.Errorf("qq-obv11: send message #%d: %w", i, err)
		}
	}
	return nil
}

// SendProactive pushes a message not triggered by a recent inbound. It is
// rate limited (see design/08 section 3: OneBot needs a rate limit to avoid
// unusual burst patterns).
func (a *Adapter) SendProactive(ctx context.Context, msg adapter.UnifiedMessage) error {
	if err := ctx.Err(); err != nil {
		return fmt.Errorf("qq-obv11: send proactive: %w", err)
	}
	conn := a.currentConn()
	if conn == nil {
		return fmt.Errorf("qq-obv11: send proactive: %w", adapter.ErrNotConnected)
	}
	return a.sendMessage(ctx, conn, msg)
}

// SetMessageHandler installs the push-style inbound callback. A nil fn clears it.
func (a *Adapter) SetMessageHandler(fn adapter.MessageHandler) {
	a.handlerMu.Lock()
	a.handler = fn
	a.handlerMu.Unlock()
}

// Capabilities declares what the QQ OneBot v11 adapter supports.
func (a *Adapter) Capabilities() adapter.Capabilities {
	return adapter.Capabilities{
		MaxMessageLength:  defaultMaxMessageLength,
		Markdown:          true,
		Image:             true,
		Voice:             true,
		Reaction:          false,
		TypingHint:        false,
		RecommendBurstMax: defaultRecommendBurstMax,
		Proactive:         true,
	}.Normalize()
}

// ListChannels returns the groups the adapter currently knows about. Enumerating
// friends / full group list requires the OneBot HTTP API, which is out of scope
// for the WebSocket-only M6 adapter; it is reported as a follow-up.
func (a *Adapter) ListChannels(ctx context.Context) ([]adapter.ChannelInfo, error) {
	a.groupMu.RLock()
	defer a.groupMu.RUnlock()
	out := make([]adapter.ChannelInfo, 0, len(a.groups))
	for id, name := range a.groups {
		out = append(out, adapter.ChannelInfo{
			ChannelID:   id,
			ChannelType: adapter.ChannelGroup,
			ChannelName: name,
			GroupID:     id,
			GroupName:   name,
		})
	}
	return out, nil
}

// Addr returns the bound listen address in server mode ("" when not serving).
func (a *Adapter) Addr() string {
	a.mu.RLock()
	defer a.mu.RUnlock()
	if a.ln == nil {
		return ""
	}
	return a.ln.Addr().String()
}

// readLoop is the single inbound-reader goroutine. It reads frames from the
// active connection, dispatching message events; in client mode it reconnects
// after drops, in server mode it waits for a new OneBot client.
func (a *Adapter) readLoop(ctx context.Context) {
	for {
		conn := a.currentConn()
		if conn == nil {
			if a.cfg.Mode == "client" {
				if err := a.connectClient(ctx); err != nil {
					a.log.Warn("onebot reconnect failed", "err", err)
					if !sleepCtx(ctx, 3*time.Second) {
						return
					}
					continue
				}
			} else if !a.waitConn(ctx) {
				return
			}
			conn = a.currentConn()
		}
		a.readConn(ctx, conn)
		if ctx.Err() != nil {
			return
		}
	}
}

// readConn reads frames from conn until it closes, the context is canceled, or
// a close frame is received, marking the adapter disconnected on exit.
func (a *Adapter) readConn(ctx context.Context, conn *wsConn) {
	watchDone := make(chan struct{})
	go func() {
		select {
		case <-ctx.Done():
			_ = conn.Close()
		case <-watchDone:
		}
	}()
	defer close(watchDone)

	for {
		opcode, payload, err := conn.ReadMessage()
		if err != nil {
			a.setDisconnected()
			return
		}
		switch opcode {
		case opPing:
			_ = conn.WriteMessage(opPong, payload)
		case opText, opBinary:
			a.handlePayload(ctx, payload)
		case opClose:
			_ = conn.WriteMessage(opClose, nil)
			a.setDisconnected()
			return
		}
	}
}

// handlePayload parses a text frame, converting message events into normalized
// UnifiedMessage and dispatching them.
func (a *Adapter) handlePayload(ctx context.Context, payload []byte) {
	ev, err := parseEvent(payload)
	if err != nil {
		a.log.Debug("non-event payload ignored", "err", err)
		return
	}
	if ev.PostType != "message" {
		return
	}
	msg := a.toUnified(ev, payload)
	if err := msg.Validate(); err != nil {
		a.log.Warn("invalid unified message dropped", "err", err)
		return
	}
	a.dispatch(ctx, msg)
}

// dispatch routes an inbound message to the registered push handler, falling
// back to the ReadMessages sink.
func (a *Adapter) dispatch(ctx context.Context, msg adapter.UnifiedMessage) {
	a.handlerMu.RLock()
	fn := a.handler
	a.handlerMu.RUnlock()
	if fn != nil {
		fn(ctx, msg)
		return
	}
	a.emitMu.Lock()
	emit := a.emit
	a.emitMu.Unlock()
	if emit != nil {
		emit(msg)
	}
}

// sendMessage builds and writes a single send_msg request, enforcing the rate
// limit and writing the payload to the connection.
func (a *Adapter) sendMessage(ctx context.Context, conn *wsConn, msg adapter.UnifiedMessage) error {
	segs, err := outboundSegments(msg)
	if err != nil {
		return err
	}
	messageType, userID, groupID, err := resolveTarget(msg)
	if err != nil {
		return err
	}
	echo := fmt.Sprintf("echo_%d", time.Now().UnixNano())
	payload, err := buildSendReq(messageType, userID, groupID, segs, echo)
	if err != nil {
		return err
	}
	if a.cfg.SendInterval > 0 {
		if err := a.waitSendInterval(ctx); err != nil {
			return err
		}
	}
	if err := a.tryAcquireSend(msg); err != nil {
		return err
	}
	if err := conn.WriteMessage(opText, payload); err != nil {
		a.setDisconnected()
		return fmt.Errorf("qq-obv11: write send_msg: %w", err)
	}
	a.mu.Lock()
	a.lastSend = time.Now()
	a.mu.Unlock()
	return nil
}

// waitSendInterval sleeps so consecutive sends are at least SendInterval apart.
func (a *Adapter) waitSendInterval(ctx context.Context) error {
	for {
		a.mu.RLock()
		last := a.lastSend
		a.mu.RUnlock()
		if last.IsZero() {
			return nil
		}
		wait := a.cfg.SendInterval - time.Since(last)
		if wait <= 0 {
			return nil
		}
		select {
		case <-ctx.Done():
			return fmt.Errorf("qq-obv11: send interval: %w", ctx.Err())
		case <-time.After(wait):
		}
	}
}

// tryAcquireSend 检查本条出站消息所属会话（群聊/私聊）的发送滑窗，额度用尽时返回
// ErrRateLimited。额度按会话独立计数（裁决 06.4.3）：给 A 群发消息不占用 B 群或私聊
// 的额度，键口径与入站滑窗一致（adapter.ConversationKey）。适配器仍保留账号级的
// SendInterval 发送间隔（更保守，只收紧不放宽）。
func (a *Adapter) tryAcquireSend(msg adapter.UnifiedMessage) error {
	if !a.limiter.allow(adapter.ConversationKey(msg), time.Now()) {
		return fmt.Errorf("qq-obv11: %w", ErrRateLimited)
	}
	return nil
}

// setConn installs a new active connection, closing any previous one and waking
// the read loop (server mode).
func (a *Adapter) setConn(conn *wsConn) {
	a.mu.Lock()
	old := a.conn
	a.conn = conn
	a.connected = true
	a.mu.Unlock()
	if old != nil && old != conn {
		_ = old.Close()
	}
	select {
	case a.newConn <- struct{}{}:
	default:
	}
}

// setDisconnected marks the session down, dropping the current connection.
func (a *Adapter) setDisconnected() {
	a.mu.Lock()
	if a.conn != nil {
		_ = a.conn.Close()
		a.conn = nil
	}
	a.connected = false
	a.mu.Unlock()
}

// currentConn returns the active wsConn, or nil.
func (a *Adapter) currentConn() *wsConn {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return a.conn
}

// waitConn blocks in server mode until a OneBot client connects or ctx ends.
func (a *Adapter) waitConn(ctx context.Context) bool {
	for a.currentConn() == nil {
		select {
		case <-a.newConn:
		case <-ctx.Done():
			return false
		case <-time.After(time.Second):
		}
	}
	return true
}

func (a *Adapter) rememberGroup(id, name string) {
	if id == "" {
		return
	}
	a.groupMu.Lock()
	a.groups[id] = name
	a.groupMu.Unlock()
}

func (a *Adapter) groupName(id string) string {
	if id == "" {
		return ""
	}
	a.groupMu.RLock()
	defer a.groupMu.RUnlock()
	return a.groups[id]
}

func sleepCtx(ctx context.Context, d time.Duration) bool {
	select {
	case <-ctx.Done():
		return false
	case <-time.After(d):
		return true
	}
}