package nixmsg

import (
	"context"
	"encoding/json"
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"github.com/google/uuid"
)

type pendingReq struct {
	rid string
	ch  chan respFrame
}

type sendItem struct {
	frame    map[string]any
	payload  []byte
	id       string
	sendAtMs *int64
	result   chan sendOutcome
	inflight bool
}

type sendOutcome struct {
	res SendResult
	err error
}

type dedupState int

const (
	dedupDelivered dedupState = iota + 1
	dedupAcked
)

type dedupEntry struct {
	state dedupState
	from  string
	id    string
}

// Client NixMsg 客户端。
type Client struct {
	opts       Options
	endpointID string
	url        string
	credKind   string
	transport  transport
	backoff    *reconnectBackoff

	mu            sync.Mutex
	state         ConnectionState
	handshook     bool
	limits        HandshakeLimits
	clockSkew     int64
	session       string
	stopReconnect bool
	closed        bool

	ridSeq   atomic.Uint64
	pending  map[string]*pendingReq
	sendQ    []*sendItem
	inflight int

	dedup    map[string]*dedupEntry
	dedupOrd []string

	receiptSeen map[string]struct{}

	cbMu sync.Mutex

	onSession    func(token string)
	onMessage    func(msg Message) error
	onReceipt    func(r Receipt)
	onRevoked    func(e RevokedEvent)
	onPresence   func(e PresenceEvent)
	onGroupEvent func(e GroupEvent)
	onConnection func(ev ConnectionEvent)

	helloSentAt time.Time
	ctx         context.Context
	cancel      context.CancelFunc
}

// New 创建客户端（尚未连接）。
func New() *Client {
	return &Client{
		pending:     make(map[string]*pendingReq),
		dedup:       make(map[string]*dedupEntry),
		receiptSeen: make(map[string]struct{}),
		state:       StateOffline,
		backoff:     newReconnectBackoff(),
	}
}

// OnSession 会话令牌回调。
func (c *Client) OnSession(h func(token string)) { c.onSession = h }

// OnMessage 消息回调。自动模式下返回 error 则不发 ack 并删去重记录。
func (c *Client) OnMessage(h func(msg Message) error) { c.onMessage = h }

// OnReceipt 回执回调。
func (c *Client) OnReceipt(h func(r Receipt)) { c.onReceipt = h }

// OnRevoked 撤回/作废回调。
func (c *Client) OnRevoked(h func(e RevokedEvent)) { c.onRevoked = h }

// OnPresence 上下线回调。
func (c *Client) OnPresence(h func(e PresenceEvent)) { c.onPresence = h }

// OnGroupEvent 群事件回调。
func (c *Client) OnGroupEvent(h func(e GroupEvent)) { c.onGroupEvent = h }

// OnConnection 连接状态回调。
func (c *Client) OnConnection(h func(ev ConnectionEvent)) { c.onConnection = h }

func newMessageID() string {
	id, err := uuid.NewV7()
	if err != nil {
		return uuid.NewString()
	}
	return id.String()
}

func (c *Client) nextRID() string {
	return fmt.Sprintf("%d", c.ridSeq.Add(1))
}

type respFrame struct {
	OK    bool            `json:"ok"`
	Data  json.RawMessage `json:"data"`
	Error *struct {
		Code    string `json:"code"`
		Message string `json:"message"`
	} `json:"error"`
}