package libbox

import (
	"bufio"
	"net"
	"slices"
	"strings"
	"time"

	"github.com/sagernet/sing-box/experimental/clashapi"
	"github.com/sagernet/sing-box/experimental/clashapi/trafficontrol"
	"github.com/sagernet/sing/common/binary"
	E "github.com/sagernet/sing/common/exceptions"
	M "github.com/sagernet/sing/common/metadata"
	"github.com/sagernet/sing/common/varbin"

	"github.com/gofrs/uuid/v5"
)

func (c *CommandClient) handleConnectionsConn(conn net.Conn) {
	defer conn.Close()
	reader := bufio.NewReader(conn)
	var (
		rawConnections []Connection
		connections    Connections
	)
	for {
		err := varbin.Read(reader, binary.BigEndian, &rawConnections)
		if err != nil {
			c.handler.Disconnected(err.Error())
			return
		}
		connections.input = rawConnections
		c.handler.WriteConnections(&connections)
	}
}

func (s *CommandServer) handleConnectionsConn(conn net.Conn) error {
	var interval int64
	err := binary.Read(conn, binary.BigEndian, &interval)
	if err != nil {
		return E.Cause(err, "read interval")
	}
	ticker := time.NewTicker(time.Duration(interval))
	defer ticker.Stop()
	ctx := connKeepAlive(conn)
	var trafficManager *trafficontrol.Manager
	for {
		service := s.service
		if service != nil {
			clashServer := service.instance.Router().ClashServer()
			if clashServer == nil {
				return E.New("Clash API disabled")
			}
			trafficManager = clashServer.(*clashapi.Server).TrafficManager()
			break
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
		}
	}
	var (
		connections    = make(map[uuid.UUID]*Connection)
		outConnections []Connection
	)
	writer := bufio.NewWriter(conn)
	for {
		outConnections = outConnections[:0]
		for _, connection := range trafficManager.Connections() {
			outConnections = append(outConnections, newConnection(connections, connection, false))
		}
		for _, connection := range trafficManager.ClosedConnections() {
			outConnections = append(outConnections, newConnection(connections, connection, true))
		}
		err = varbin.Write(writer, binary.BigEndian, outConnections)
		if err != nil {
			return err
		}
		err = writer.Flush()
		if err != nil {
			return err
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
		}
	}
}

const (
	ConnectionStateAll = iota
	ConnectionStateActive
	ConnectionStateClosed
)

type Connections struct {
	input    []Connection
	filtered []Connection
}

func (c *Connections) FilterState(state int32) {
	c.filtered = c.filtered[:0]
	switch state {
	case ConnectionStateAll:
		c.filtered = append(c.filtered, c.input...)
	case ConnectionStateActive:
		for _, connection := range c.input {
			if connection.ClosedAt == 0 {
				c.filtered = append(c.filtered, connection)
			}
		}
	case ConnectionStateClosed:
		for _, connection := range c.input {
			if connection.ClosedAt != 0 {
				c.filtered = append(c.filtered, connection)
			}
		}
	}
}

func (c *Connections) SortByDate() {
	slices.SortStableFunc(c.filtered, func(x, y Connection) int {
		if x.CreatedAt < y.CreatedAt {
			return 1
		} else if x.CreatedAt > y.CreatedAt {
			return -1
		} else {
			return strings.Compare(y.ID, x.ID)
		}
	})
}

func (c *Connections) SortByTraffic() {
	slices.SortStableFunc(c.filtered, func(x, y Connection) int {
		xTraffic := x.Uplink + x.Downlink
		yTraffic := y.Uplink + y.Downlink
		if xTraffic < yTraffic {
			return 1
		} else if xTraffic > yTraffic {
			return -1
		} else {
			return strings.Compare(y.ID, x.ID)
		}
	})
}

func (c *Connections) SortByTrafficTotal() {
	slices.SortStableFunc(c.filtered, func(x, y Connection) int {
		xTraffic := x.UplinkTotal + x.DownlinkTotal
		yTraffic := y.UplinkTotal + y.DownlinkTotal
		if xTraffic < yTraffic {
			return 1
		} else if xTraffic > yTraffic {
			return -1
		} else {
			return strings.Compare(y.ID, x.ID)
		}
	})
}

func (c *Connections) Iterator() ConnectionIterator {
	return newPtrIterator(c.filtered)
}

type Connection struct {
	ID            string
	Inbound       string
	InboundType   string
	IPVersion     int32
	Network       string
	Source        string
	Destination   string
	Domain        string
	Protocol      string
	User          string
	FromOutbound  string
	CreatedAt     int64
	ClosedAt      int64
	Uplink        int64
	Downlink      int64
	UplinkTotal   int64
	DownlinkTotal int64
	Rule          string
	Outbound      string
	OutboundType  string
	ChainList     []string
}

func (c *Connection) Chain() StringIterator {
	return newIterator(c.ChainList)
}

func (c *Connection) DisplayDestination() string {
	destination := M.ParseSocksaddr(c.Destination)
	if destination.IsIP() && c.Domain != "" {
		destination = M.Socksaddr{
			Fqdn: c.Domain,
			Port: destination.Port,
		}
		return destination.String()
	}
	return c.Destination
}

type ConnectionIterator interface {
	Next() *Connection
	HasNext() bool
}

func newConnection(connections map[uuid.UUID]*Connection, metadata trafficontrol.TrackerMetadata, isClosed bool) Connection {
	if oldConnection, loaded := connections[metadata.ID]; loaded {
		if isClosed {
			if oldConnection.ClosedAt == 0 {
				oldConnection.Uplink = 0
				oldConnection.Downlink = 0
				oldConnection.ClosedAt = metadata.ClosedAt.UnixMilli()
			}
			return *oldConnection
		}
		lastUplink := oldConnection.UplinkTotal
		lastDownlink := oldConnection.DownlinkTotal
		uplinkTotal := metadata.Upload.Load()
		downlinkTotal := metadata.Download.Load()
		oldConnection.Uplink = uplinkTotal - lastUplink
		oldConnection.Downlink = downlinkTotal - lastDownlink
		oldConnection.UplinkTotal = uplinkTotal
		oldConnection.DownlinkTotal = downlinkTotal
		return *oldConnection
	}
	var rule string
	if metadata.Rule != nil {
		rule = metadata.Rule.String()
	}
	uplinkTotal := metadata.Upload.Load()
	downlinkTotal := metadata.Download.Load()
	uplink := uplinkTotal
	downlink := downlinkTotal
	var closedAt int64
	if !metadata.ClosedAt.IsZero() {
		closedAt = metadata.ClosedAt.UnixMilli()
		uplink = 0
		downlink = 0
	}
	connection := Connection{
		ID:            metadata.ID.String(),
		Inbound:       metadata.Metadata.Inbound,
		InboundType:   metadata.Metadata.InboundType,
		IPVersion:     int32(metadata.Metadata.IPVersion),
		Network:       metadata.Metadata.Network,
		Source:        metadata.Metadata.Source.String(),
		Destination:   metadata.Metadata.Destination.String(),
		Domain:        metadata.Metadata.Domain,
		Protocol:      metadata.Metadata.Protocol,
		User:          metadata.Metadata.User,
		FromOutbound:  metadata.Metadata.Outbound,
		CreatedAt:     metadata.CreatedAt.UnixMilli(),
		ClosedAt:      closedAt,
		Uplink:        uplink,
		Downlink:      downlink,
		UplinkTotal:   uplinkTotal,
		DownlinkTotal: downlinkTotal,
		Rule:          rule,
		Outbound:      metadata.Outbound,
		OutboundType:  metadata.OutboundType,
		ChainList:     metadata.Chain,
	}
	connections[metadata.ID] = &connection
	return connection
}