// VulcanizeDB
// Copyright © 2020 Vulcanize

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// 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 Affero General Public License for more details.

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

package rpc

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

	"github.com/ethereum/go-ethereum/p2p/netutil"
	"github.com/ethereum/go-ethereum/rpc"
	log "github.com/sirupsen/logrus"

	"github.com/vulcanize/eth-statediff-service/pkg/prom"
)

var (
	//  On Linux, sun_path is 108 bytes in size
	// see http://man7.org/linux/man-pages/man7/unix.7.html
	maxPathSize = 108
)

// ipcListen will create a Unix socket on the given endpoint.
func ipcListen(endpoint string) (net.Listener, error) {
	if len(endpoint) > int(maxPathSize) {
		log.Warn(fmt.Sprintf("The ipc endpoint is longer than %d characters. ", maxPathSize),
			"endpoint", endpoint)
	}

	// Ensure the IPC path exists and remove any previous leftover
	if err := os.MkdirAll(filepath.Dir(endpoint), 0751); err != nil {
		return nil, err
	}
	os.Remove(endpoint)
	l, err := net.Listen("unix", endpoint)
	if err != nil {
		return nil, err
	}
	os.Chmod(endpoint, 0600)
	return l, nil
}

func ipcServe(srv *rpc.Server, listener net.Listener) {
	for {
		conn, err := listener.Accept()
		if netutil.IsTemporaryError(err) {
			log.WithError(err).Warn("rpc accept error")
			continue
		}
		if err != nil {
			log.WithError(err).Warn("unknown error")
			continue
		}
		log.WithField("addr", conn.RemoteAddr()).Trace("accepted ipc connection")
		go prom.IPCMiddleware(srv, conn)
	}
}

// StartIPCEndpoint starts an IPC endpoint.
func StartIPCEndpoint(ipcEndpoint string, apis []rpc.API) (net.Listener, *rpc.Server, error) {
	// Register all the APIs exposed by the services.
	handler := rpc.NewServer()
	for _, api := range apis {
		if err := handler.RegisterName(api.Namespace, api.Service); err != nil {
			return nil, nil, err
		}
		log.Debug("IPC registered", "namespace", api.Namespace)
	}
	// All APIs registered, start the IPC listener.
	listener, err := ipcListen(ipcEndpoint)
	if err != nil {
		return nil, nil, err
	}

	go ipcServe(handler, listener)
	return listener, handler, nil
}