// GoCheese -- Python private package repository and caching proxy
// Copyright (C) 2019-2024 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 main

import (
	"io"
	"net"
	"net/http"
	"os"
	"sync"
	"time"
)

var (
	ALongTimeAgo = time.Unix(1, 0)
	UCSPIJob     sync.WaitGroup
)

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 UCSPIConn struct {
	eof chan struct{}
}

type ReadResult struct {
	n   int
	err error
}

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

func (conn *UCSPIConn) Write(b []byte) (int, error) { return os.Stdout.Write(b) }

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

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

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

func (conn *UCSPIConn) SetDeadline(t time.Time) error {
	if err := os.Stdin.SetReadDeadline(t); err != nil {
		return err
	}
	return os.Stdout.SetWriteDeadline(t)
}

func (conn *UCSPIConn) 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 os.Stdin.SetReadDeadline(t)
}

func (conn *UCSPIConn) SetWriteDeadline(t time.Time) error {
	return os.Stdout.SetWriteDeadline(t)
}

type UCSPI struct{ accepted bool }

type UCSPIAlreadyAccepted struct{}

func (u UCSPIAlreadyAccepted) Error() string {
	return "already accepted"
}

func (ucspi *UCSPI) Accept() (net.Conn, error) {
	if ucspi.accepted {
		return nil, UCSPIAlreadyAccepted{}
	}
	ucspi.accepted = true
	conn := UCSPIConn{eof: make(chan struct{}, 1)}
	return &conn, nil
}

func (ucspi *UCSPI) Close() error {
	return nil
}

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

func connStater(conn net.Conn, connState http.ConnState) {
	switch connState {
	case http.StateNew:
		UCSPIJob.Add(1)
	case http.StateClosed:
		UCSPIJob.Done()
	}
}