/*
 * Minio Cloud Storage, (C) 2016 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cmd

import (
	"errors"
	"net/rpc"
	"time"

	router "github.com/gorilla/mux"
)

const adminPath = "/admin"

var errUnsupportedBackend = errors.New("not supported for non erasure-code backend")

// adminCmd - exports RPC methods for service status, stop and
// restart commands.
type adminCmd struct {
	AuthRPCServer
}

// ListLocksQuery - wraps ListLocks API's query values to send over RPC.
type ListLocksQuery struct {
	AuthRPCArgs
	bucket   string
	prefix   string
	duration time.Duration
}

// ListLocksReply - wraps ListLocks response over RPC.
type ListLocksReply struct {
	AuthRPCReply
	volLocks []VolumeLockInfo
}

// UptimeReply - wraps the uptime response over RPC.
type UptimeReply struct {
	AuthRPCReply
	Uptime time.Duration
}

// Restart - Restart this instance of minio server.
func (s *adminCmd) Restart(args *AuthRPCArgs, reply *AuthRPCReply) error {
	if err := args.IsAuthenticated(); err != nil {
		return err
	}

	globalServiceSignalCh <- serviceRestart
	return nil
}

// ListLocks - lists locks held by requests handled by this server instance.
func (s *adminCmd) ListLocks(query *ListLocksQuery, reply *ListLocksReply) error {
	if err := query.IsAuthenticated(); err != nil {
		return err
	}
	volLocks := listLocksInfo(query.bucket, query.prefix, query.duration)
	*reply = ListLocksReply{volLocks: volLocks}
	return nil
}

// ReInitDisk - reinitialize storage disks and object layer to use the
// new format.
func (s *adminCmd) ReInitDisks(args *AuthRPCArgs, reply *AuthRPCReply) error {
	if err := args.IsAuthenticated(); err != nil {
		return err
	}

	if !globalIsXL {
		return errUnsupportedBackend
	}

	// Get the current object layer instance.
	objLayer := newObjectLayerFn()

	// Initialize new disks to include the newly formatted disks.
	bootstrapDisks, err := initStorageDisks(globalEndpoints)
	if err != nil {
		return err
	}

	// Initialize new object layer with newly formatted disks.
	newObjectAPI, err := newXLObjects(bootstrapDisks)
	if err != nil {
		return err
	}

	// Replace object layer with newly formatted storage.
	globalObjLayerMutex.Lock()
	globalObjectAPI = newObjectAPI
	globalObjLayerMutex.Unlock()

	// Shutdown storage belonging to old object layer instance.
	objLayer.Shutdown()

	return nil
}

// Uptime - returns the time when object layer was initialized on this server.
func (s *adminCmd) Uptime(args *AuthRPCArgs, reply *UptimeReply) error {
	if err := args.IsAuthenticated(); err != nil {
		return err
	}

	if globalBootTime.IsZero() {
		return errServerNotInitialized
	}

	// N B The uptime is computed assuming that the system time is
	// monotonic. This is not the case in time pkg in Go, see
	// https://github.com/golang/go/issues/12914. This is expected
	// to be fixed by go1.9.
	*reply = UptimeReply{
		Uptime: time.Now().UTC().Sub(globalBootTime),
	}

	return nil
}

// registerAdminRPCRouter - registers RPC methods for service status,
// stop and restart commands.
func registerAdminRPCRouter(mux *router.Router) error {
	adminRPCHandler := &adminCmd{}
	adminRPCServer := rpc.NewServer()
	err := adminRPCServer.RegisterName("Admin", adminRPCHandler)
	if err != nil {
		return traceError(err)
	}
	adminRouter := mux.NewRoute().PathPrefix(reservedBucket).Subrouter()
	adminRouter.Path(adminPath).Handler(adminRPCServer)
	return nil
}