package notify

import (
	"context"
	"net"
	"os"
	"time"
)

type serverLogicalTransportDetacher interface {
	detachLogicalSessionTransport(logical *LogicalConn, reason string, err error)
}

type serverInboundSourcePusher interface {
	pushMessageSource([]byte, interface{})
}

func (c *LogicalConn) readTUMessage() {
	rt := c.clientConnSessionRuntimeSnapshot()
	if rt == nil {
		return
	}
	c.readTUMessageLoop(rt)
}

func (c *LogicalConn) readTUMessageLoop(rt *clientConnSessionRuntime) {
	if rt == nil {
		return
	}
	stopCtx := rt.transportStopCtx
	if stopCtx == nil {
		stopCtx = rt.stopCtx
	}
	if stopCtx == nil {
		return
	}
	conn := rt.tuConn
	generation := rt.transportGeneration
	defer closeClientConnSessionRuntimeTransportDone(rt)
	buf := streamReadBuffer()
	for {
		select {
		case <-sessionStopChan(stopCtx):
			if c.shouldCloseTransportOnStop(conn) {
				_ = conn.Close()
			}
			return
		default:
		}
		num, data, err := c.readFromTUTransportConnWithBuffer(conn, buf)
		if !c.handleTUTransportReadResultWithSession(stopCtx, conn, generation, num, data, err) {
			return
		}
	}
}

func (c *LogicalConn) readFromTUTransportConnWithBuffer(conn net.Conn, data []byte) (int, []byte, error) {
	if len(data) == 0 {
		data = streamReadBuffer()
	}
	if conn == nil {
		return 0, nil, net.ErrClosed
	}
	if timeout := c.clientConnMaxReadTimeoutSnapshot(); timeout > 0 {
		_ = conn.SetReadDeadline(time.Now().Add(timeout))
	}
	num, err := conn.Read(data)
	return num, data, err
}

func (c *LogicalConn) handleTUTransportReadResultWithSession(stopCtx context.Context, conn net.Conn, generation uint64, num int, data []byte, err error) bool {
	if err == os.ErrDeadlineExceeded {
		if num != 0 {
			c.pushServerOwnedTransportMessage(data[:num], conn, generation)
		}
		return true
	}
	if err != nil {
		select {
		case <-sessionStopChan(stopCtx):
			if c.shouldCloseTransportOnStop(conn) {
				_ = conn.Close()
			}
			return false
		default:
		}
		if detacher, ok := c.Server().(serverLogicalTransportDetacher); ok && c.shouldPreserveLogicalPeerOnTransportLoss() {
			detacher.detachLogicalSessionTransport(c, "read error", err)
			return false
		}
		c.stopServerOwnedSession("read error", err)
		return false
	}
	c.pushServerOwnedTransportMessage(data[:num], conn, generation)
	return true
}

func (c *LogicalConn) pushServerOwnedTransportMessage(data []byte, conn net.Conn, generation uint64) {
	if c == nil || len(data) == 0 {
		return
	}
	server := c.Server()
	if server == nil {
		return
	}
	if pusher, ok := server.(serverInboundSourcePusher); ok {
		pusher.pushMessageSource(data, newServerInboundSource(c, conn, nil, generation))
		return
	}
	server.pushMessage(data, c.clientConnIDSnapshot())
}

func (c *LogicalConn) shouldCloseTransportOnStop(conn net.Conn) bool {
	if c == nil || conn == nil {
		return false
	}
	rt := c.clientConnSessionRuntimeSnapshot()
	if rt == nil || !rt.transportAttached {
		return false
	}
	current := rt.tuConn
	if rt.transport != nil && rt.transport.connSnapshot() != nil {
		current = rt.transport.connSnapshot()
	}
	return current == conn
}

func (c *ClientConn) readFromTUTransport() (int, []byte, error) {
	binding := c.clientConnTransportBindingSnapshot()
	if binding == nil {
		return 0, nil, net.ErrClosed
	}
	conn := binding.connSnapshot()
	return c.readFromTUTransportConn(conn)
}

func (c *ClientConn) readFromTUTransportConn(conn net.Conn) (int, []byte, error) {
	return c.readFromTUTransportConnWithBuffer(conn, streamReadBuffer())
}

func (c *ClientConn) readFromTUTransportConnWithBuffer(conn net.Conn, data []byte) (int, []byte, error) {
	if logical := c.LogicalConn(); logical != nil {
		return logical.readFromTUTransportConnWithBuffer(conn, data)
	}
	if len(data) == 0 {
		data = streamReadBuffer()
	}
	if conn == nil {
		return 0, nil, net.ErrClosed
	}
	if timeout := c.clientConnMaxReadTimeoutSnapshot(); timeout > 0 {
		_ = conn.SetReadDeadline(time.Now().Add(timeout))
	}
	num, err := conn.Read(data)
	return num, data, err
}

func (c *ClientConn) handleTUTransportReadResult(num int, data []byte, err error) bool {
	return c.handleTUTransportReadResultWithSession(c.clientConnTransportStopContextSnapshot(), c.clientConnTransportSnapshot(), c.clientConnTransportGenerationSnapshot(), num, data, err)
}

func (c *ClientConn) handleTUTransportReadResultWithSession(stopCtx context.Context, conn net.Conn, generation uint64, num int, data []byte, err error) bool {
	if logical := c.LogicalConn(); logical != nil {
		return logical.handleTUTransportReadResultWithSession(stopCtx, conn, generation, num, data, err)
	}
	if err == os.ErrDeadlineExceeded {
		if num != 0 {
			c.pushServerOwnedTransportMessage(data[:num], conn, generation)
		}
		return true
	}
	if err != nil {
		select {
		case <-sessionStopChan(stopCtx):
			if c.shouldCloseClientConnTransportOnStop(conn) {
				_ = conn.Close()
			}
			return false
		default:
		}
		if detacher, ok := c.server.(serverLogicalTransportDetacher); ok && c.shouldPreserveLogicalPeerOnTransportLoss() {
			detacher.detachLogicalSessionTransport(logicalConnFromClient(c), "read error", err)
			return false
		}
		c.stopServerOwnedSession("read error", err)
		return false
	}
	c.pushServerOwnedTransportMessage(data[:num], conn, generation)
	return true
}

func (c *ClientConn) pushServerOwnedTransportMessage(data []byte, conn net.Conn, generation uint64) {
	if logical := c.LogicalConn(); logical != nil {
		logical.pushServerOwnedTransportMessage(data, conn, generation)
		return
	}
	if c == nil || c.server == nil || len(data) == 0 {
		return
	}
	if pusher, ok := c.server.(serverInboundSourcePusher); ok {
		pusher.pushMessageSource(data, newServerInboundSource(logicalConnFromClient(c), conn, nil, generation))
		return
	}
	c.server.pushMessage(data, c.clientConnIDSnapshot())
}

func (c *ClientConn) shouldCloseClientConnTransportOnStop(conn net.Conn) bool {
	if logical := c.LogicalConn(); logical != nil {
		return logical.shouldCloseTransportOnStop(conn)
	}
	if c == nil || conn == nil {
		return false
	}
	rt := c.clientConnSessionRuntimeSnapshot()
	if rt == nil || !rt.transportAttached {
		return false
	}
	current := rt.tuConn
	if rt.transport != nil && rt.transport.connSnapshot() != nil {
		current = rt.transport.connSnapshot()
	}
	return current == conn
}