/*
ucspi -- UCSPI-related utilities
Copyright (C) 2021 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package ucspi

import (
	"io"
	"net"
	"os"
	"time"
)

var aLongTimeAgo = time.Unix(1, 0)

type UCSPIAddr struct {
	ip   string
	port string
}

func (addr *UCSPIAddr) Network() string { return "tcp" }

func (addr *UCSPIAddr) String() string { return addr.ip + ":" + addr.port }

type Conn struct {
	R   *os.File
	W   *os.File
	eof chan struct{}
}

type ReadResult struct {
	n   int
	err error
}

func (conn *Conn) Read(b []byte) (int, error) {
	c := make(chan ReadResult)
	go func() {
		n, err := conn.R.Read(b)
		c <- ReadResult{n, err}
	}()
	select {
	case res := <-c:
		return res.n, res.err
	case <-conn.eof:
		return 0, io.EOF
	}
}

func (conn *Conn) Write(b []byte) (int, error) { return conn.W.Write(b) }

func (conn *Conn) Close() error {
	if err := conn.R.Close(); err != nil {
		return err
	}
	return os.Stdin.Close()
}

func (conn *Conn) LocalAddr() net.Addr {
	return &UCSPIAddr{ip: os.Getenv("TCPLOCALIP"), port: os.Getenv("TCPLOCALPORT")}
}

func (conn *Conn) RemoteAddr() net.Addr {
	return &UCSPIAddr{ip: os.Getenv("TCPREMOTEIP"), port: os.Getenv("TCPREMOTEPORT")}
}

func (conn *Conn) SetDeadline(t time.Time) error {
	if err := conn.R.SetReadDeadline(t); err != nil {
		return err
	}
	return conn.W.SetWriteDeadline(t)
}

func (conn *Conn) SetReadDeadline(t time.Time) error {
	// An ugly hack to forcefully terminate pending read.
	// net/http calls SetReadDeadline(aLongTimeAgo), but file
	// descriptors are not capable to exit immediately that way.
	if t.Equal(aLongTimeAgo) {
		conn.eof <- struct{}{}
	}
	return conn.R.SetReadDeadline(t)
}

func (conn *Conn) SetWriteDeadline(t time.Time) error {
	return conn.W.SetWriteDeadline(t)
}