package peer

import (
	"fmt"
	"net"
	"os"
	"path/filepath"
	"sync/atomic"

	"omnisocketgo/cmd/internal/latencylog"
	"omnisocketgo/cmd/internal/protocol"
	"omnisocketgo/cmd/internal/transport"
)

// UDPClient 表示一个通过 UDP 连接到 server 的 peer。
type UDPClient struct {
	id     string
	conn   *transport.UDPConn
	logger latencylog.Logger

	nextID uint64
}

// DialUDP 通过 UDP 连接到 server，并发送 register 消息完成身份注册。
func DialUDP(serverAddr, peerID string, opts ...Option) (*UDPClient, error) {
	options := clientOptions{
		logger:               latencylog.NoopLogger{},
		udpLinuxTimestamping: true,
	}
	for _, opt := range opts {
		opt(&options)
	}
	if options.logger == nil {
		options.logger = latencylog.NoopLogger{}
	}

	udpServerAddr, err := net.ResolveUDPAddr("udp", serverAddr)
	if err != nil {
		return nil, fmt.Errorf("peer: resolve udp server addr %s: %w", serverAddr, err)
	}

	var localAddr *net.UDPAddr
	if options.bindIP != "" {
		ip := net.ParseIP(options.bindIP)
		if ip == nil {
			return nil, fmt.Errorf("peer: invalid bind ip %q", options.bindIP)
		}
		localAddr = &net.UDPAddr{IP: ip}
	}

	rawConn, err := net.DialUDP("udp", localAddr, udpServerAddr)
	if err != nil {
		return nil, fmt.Errorf("peer: dial udp server %s: %w", serverAddr, err)
	}

	conn, err := transport.NewUDPConn(
		rawConn,
		nil, // peer 侧已连接模式，不需要指定 peerAddr
		transport.WithUDPLogger(options.logger, latencylog.NodeRolePeer, peerID),
		transport.WithUDPLinuxTimestamping(options.udpLinuxTimestamping),
		transport.WithUDPTXTimestampDebugLogger(options.txTimestampDebugLogger),
	)
	if err != nil {
		_ = rawConn.Close()
		return nil, fmt.Errorf("peer: create udp transport conn: %w", err)
	}

	client := &UDPClient{
		id:     peerID,
		conn:   conn,
		logger: options.logger,
	}

	// 发送 register 消息完成身份注册
	if err := conn.Send(protocol.Message{
		Type: protocol.MessageTypeRegister,
		From: peerID,
		To:   protocol.ServerPeerID,
	}); err != nil {
		_ = conn.Close()
		return nil, fmt.Errorf("peer: udp register with server: %w", err)
	}

	return client, nil
}

// ID 返回当前 client 的 peer 标识。
func (c *UDPClient) ID() string {
	return c.id
}

// SendText 向目标 peer 发送一条文本消息。
func (c *UDPClient) SendText(to, body string) error {
	msg := protocol.Message{
		Type: protocol.MessageTypeText,
		ID:   c.nextMessageID(),
		From: c.id,
		To:   to,
	}
	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventAAppPrepBegin, msg)

	msg.Body = []byte(body)

	return c.conn.Send(msg)
}

// SendFile 向目标 peer 发送一条文件消息。
func (c *UDPClient) SendFile(to, fileName string, body []byte) error {
	msg := protocol.Message{
		Type:     protocol.MessageTypeFile,
		ID:       c.nextMessageID(),
		From:     c.id,
		To:       to,
		FileName: fileName,
	}
	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventAAppPrepBegin, msg)

	bodyCopy := make([]byte, len(body))
	copy(bodyCopy, body)

	msg.Body = bodyCopy

	return c.conn.Send(msg)
}

// SendFilePath 从本地文件读取内容并发送给目标 peer。
func (c *UDPClient) SendFilePath(to, path string) error {
	msg := protocol.Message{
		Type:     protocol.MessageTypeFile,
		ID:       c.nextMessageID(),
		From:     c.id,
		To:       to,
		FileName: filepath.Base(path),
	}
	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventAAppPrepBegin, msg)

	body, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("peer: read file %s: %w", path, err)
	}

	msg.Body = body

	return c.conn.Send(msg)
}

// Receive 读取一条来自 server 的消息。
func (c *UDPClient) Receive() (protocol.Message, error) {
	msg, _, err := c.conn.Receive()
	if err != nil {
		return protocol.Message{}, fmt.Errorf("peer: udp receive from server: %w", err)
	}

	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBAppRecv, msg)

	return msg, nil
}

// ReceiveLoop 持续接收 server 消息并交给 handler 处理。
func (c *UDPClient) ReceiveLoop(handler func(protocol.Message) error) error {
	return c.conn.ReceiveLoop(func(msg protocol.Message, _ *net.UDPAddr) error {
		switch msg.Type {
		case protocol.MessageTypeText, protocol.MessageTypeFile, protocol.MessageTypeError:
			latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBAppRecv, msg)
			return handler(msg)
		default:
			return fmt.Errorf("peer: unexpected message type from server: %s", msg.Type)
		}
	})
}

// PersistMessage 将收到的业务消息写入本地磁盘。
func (c *UDPClient) PersistMessage(msg protocol.Message, inboxDir string) (string, error) {
	if !latencylog.IsBusinessMessage(msg) {
		return "", fmt.Errorf("peer: cannot persist message type %s", msg.Type)
	}
	if inboxDir == "" {
		return "", fmt.Errorf("peer: inbox directory is required")
	}

	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBPersistBegin, msg)

	if err := os.MkdirAll(inboxDir, 0o755); err != nil {
		return "", fmt.Errorf("peer: create inbox dir %s: %w", inboxDir, err)
	}

	path, err := persistMessageToDisk(msg, inboxDir)
	if err != nil {
		return "", err
	}

	latencylog.LogMessageEvent(c.logger, latencylog.NodeRolePeer, c.id, latencylog.EventBPersistEnd, msg)

	return path, nil
}

// Close 关闭与 server 的 UDP 连接。
func (c *UDPClient) Close() error {
	return c.conn.Close()
}

func (c *UDPClient) nextMessageID() uint64 {
	return atomic.AddUint64(&c.nextID, 1)
}