/*
   Copyright The containerd Authors.

   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 server

import (
	"context"
	"expvar"
	"io"
	"net"
	"net/http"
	"net/http/pprof"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	csapi "github.com/containerd/containerd/api/services/content/v1"
	ssapi "github.com/containerd/containerd/api/services/snapshots/v1"
	"github.com/containerd/containerd/content"
	"github.com/containerd/containerd/content/local"
	csproxy "github.com/containerd/containerd/content/proxy"
	"github.com/containerd/containerd/defaults"
	"github.com/containerd/containerd/events/exchange"
	"github.com/containerd/containerd/log"
	"github.com/containerd/containerd/metadata"
	"github.com/containerd/containerd/pkg/dialer"
	"github.com/containerd/containerd/plugin"
	srvconfig "github.com/containerd/containerd/services/server/config"
	"github.com/containerd/containerd/snapshots"
	ssproxy "github.com/containerd/containerd/snapshots/proxy"
	metrics "github.com/docker/go-metrics"
	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
	"github.com/pkg/errors"
	bolt "go.etcd.io/bbolt"
	"google.golang.org/grpc"
)

// New creates and initializes a new containerd server
func New(ctx context.Context, config *srvconfig.Config) (*Server, error) {
	switch {
	case config.Root == "":
		return nil, errors.New("root must be specified")
	case config.State == "":
		return nil, errors.New("state must be specified")
	case config.Root == config.State:
		return nil, errors.New("root and state must be different paths")
	}

	if err := os.MkdirAll(config.Root, 0711); err != nil {
		return nil, err
	}
	if err := os.MkdirAll(config.State, 0711); err != nil {
		return nil, err
	}
	if err := apply(ctx, config); err != nil {
		return nil, err
	}
	plugins, err := LoadPlugins(ctx, config)
	if err != nil {
		return nil, err
	}

	serverOpts := []grpc.ServerOption{
		grpc.UnaryInterceptor(grpc_prometheus.UnaryServerInterceptor),
		grpc.StreamInterceptor(grpc_prometheus.StreamServerInterceptor),
	}
	if config.GRPC.MaxRecvMsgSize > 0 {
		serverOpts = append(serverOpts, grpc.MaxRecvMsgSize(config.GRPC.MaxRecvMsgSize))
	}
	if config.GRPC.MaxSendMsgSize > 0 {
		serverOpts = append(serverOpts, grpc.MaxSendMsgSize(config.GRPC.MaxSendMsgSize))
	}
	rpc := grpc.NewServer(serverOpts...)
	var (
		services []plugin.Service
		s        = &Server{
			rpc:    rpc,
			events: exchange.NewExchange(),
			config: config,
		}
		initialized = plugin.NewPluginSet()
	)
	for _, p := range plugins {
		id := p.URI()
		log.G(ctx).WithField("type", p.Type).Infof("loading plugin %q...", id)

		initContext := plugin.NewContext(
			ctx,
			p,
			initialized,
			config.Root,
			config.State,
		)
		initContext.Events = s.events
		initContext.Address = config.GRPC.Address

		// load the plugin specific configuration if it is provided
		if p.Config != nil {
			pluginConfig, err := config.Decode(p.ID, p.Config)
			if err != nil {
				return nil, err
			}
			initContext.Config = pluginConfig
		}
		result := p.Init(initContext)
		if err := initialized.Add(result); err != nil {
			return nil, errors.Wrapf(err, "could not add plugin result to plugin set")
		}

		instance, err := result.Instance()
		if err != nil {
			if plugin.IsSkipPlugin(err) {
				log.G(ctx).WithField("type", p.Type).Infof("skip loading plugin %q...", id)
			} else {
				log.G(ctx).WithError(err).Warnf("failed to load plugin %s", id)
			}
			continue
		}
		// check for grpc services that should be registered with the server
		if service, ok := instance.(plugin.Service); ok {
			services = append(services, service)
		}
		s.plugins = append(s.plugins, result)
	}
	// register services after all plugins have been initialized
	for _, service := range services {
		if err := service.Register(rpc); err != nil {
			return nil, err
		}
	}
	return s, nil
}

// Server is the containerd main daemon
type Server struct {
	rpc     *grpc.Server
	events  *exchange.Exchange
	config  *srvconfig.Config
	plugins []*plugin.Plugin
}

// ServeGRPC provides the containerd grpc APIs on the provided listener
func (s *Server) ServeGRPC(l net.Listener) error {
	if s.config.Metrics.GRPCHistogram {
		// enable grpc time histograms to measure rpc latencies
		grpc_prometheus.EnableHandlingTimeHistogram()
	}
	// before we start serving the grpc API register the grpc_prometheus metrics
	// handler.  This needs to be the last service registered so that it can collect
	// metrics for every other service
	grpc_prometheus.Register(s.rpc)
	return trapClosedConnErr(s.rpc.Serve(l))
}

// ServeMetrics provides a prometheus endpoint for exposing metrics
func (s *Server) ServeMetrics(l net.Listener) error {
	m := http.NewServeMux()
	m.Handle("/v1/metrics", metrics.Handler())
	return trapClosedConnErr(http.Serve(l, m))
}

// ServeDebug provides a debug endpoint
func (s *Server) ServeDebug(l net.Listener) error {
	// don't use the default http server mux to make sure nothing gets registered
	// that we don't want to expose via containerd
	m := http.NewServeMux()
	m.Handle("/debug/vars", expvar.Handler())
	m.Handle("/debug/pprof/", http.HandlerFunc(pprof.Index))
	m.Handle("/debug/pprof/cmdline", http.HandlerFunc(pprof.Cmdline))
	m.Handle("/debug/pprof/profile", http.HandlerFunc(pprof.Profile))
	m.Handle("/debug/pprof/symbol", http.HandlerFunc(pprof.Symbol))
	m.Handle("/debug/pprof/trace", http.HandlerFunc(pprof.Trace))
	return trapClosedConnErr(http.Serve(l, m))
}

// Stop the containerd server canceling any open connections
func (s *Server) Stop() {
	s.rpc.Stop()
	for i := len(s.plugins) - 1; i >= 0; i-- {
		p := s.plugins[i]
		instance, err := p.Instance()
		if err != nil {
			log.L.WithError(err).WithField("id", p.Registration.ID).
				Errorf("could not get plugin instance")
			continue
		}
		closer, ok := instance.(io.Closer)
		if !ok {
			continue
		}
		if err := closer.Close(); err != nil {
			log.L.WithError(err).WithField("id", p.Registration.ID).
				Errorf("failed to close plugin")
		}
	}
}

// LoadPlugins loads all plugins into containerd and generates an ordered graph
// of all plugins.
func LoadPlugins(ctx context.Context, config *srvconfig.Config) ([]*plugin.Registration, error) {
	// load all plugins into containerd
	if err := plugin.Load(filepath.Join(config.Root, "plugins")); err != nil {
		return nil, err
	}
	// load additional plugins that don't automatically register themselves
	plugin.Register(&plugin.Registration{
		Type: plugin.ContentPlugin,
		ID:   "content",
		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
			ic.Meta.Exports["root"] = ic.Root
			return local.NewStore(ic.Root)
		},
	})
	plugin.Register(&plugin.Registration{
		Type: plugin.MetadataPlugin,
		ID:   "bolt",
		Requires: []plugin.Type{
			plugin.ContentPlugin,
			plugin.SnapshotPlugin,
		},
		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
			if err := os.MkdirAll(ic.Root, 0711); err != nil {
				return nil, err
			}
			cs, err := ic.Get(plugin.ContentPlugin)
			if err != nil {
				return nil, err
			}

			snapshottersRaw, err := ic.GetByType(plugin.SnapshotPlugin)
			if err != nil {
				return nil, err
			}

			snapshotters := make(map[string]snapshots.Snapshotter)
			for name, sn := range snapshottersRaw {
				sn, err := sn.Instance()
				if err != nil {
					log.G(ic.Context).WithError(err).
						Warnf("could not use snapshotter %v in metadata plugin", name)
					continue
				}
				snapshotters[name] = sn.(snapshots.Snapshotter)
			}

			path := filepath.Join(ic.Root, "meta.db")
			ic.Meta.Exports["path"] = path

			db, err := bolt.Open(path, 0644, nil)
			if err != nil {
				return nil, err
			}
			mdb := metadata.NewDB(db, cs.(content.Store), snapshotters)
			if err := mdb.Init(ic.Context); err != nil {
				return nil, err
			}
			return mdb, nil
		},
	})

	clients := &proxyClients{}
	for name, pp := range config.ProxyPlugins {
		var (
			t plugin.Type
			f func(*grpc.ClientConn) interface{}

			address = pp.Address
		)

		switch pp.Type {
		case string(plugin.SnapshotPlugin), "snapshot":
			t = plugin.SnapshotPlugin
			ssname := name
			f = func(conn *grpc.ClientConn) interface{} {
				return ssproxy.NewSnapshotter(ssapi.NewSnapshotsClient(conn), ssname)
			}

		case string(plugin.ContentPlugin), "content":
			t = plugin.ContentPlugin
			f = func(conn *grpc.ClientConn) interface{} {
				return csproxy.NewContentStore(csapi.NewContentClient(conn))
			}
		default:
			log.G(ctx).WithField("type", pp.Type).Warn("unknown proxy plugin type")
		}

		plugin.Register(&plugin.Registration{
			Type: t,
			ID:   name,
			InitFn: func(ic *plugin.InitContext) (interface{}, error) {
				ic.Meta.Exports["address"] = address
				conn, err := clients.getClient(address)
				if err != nil {
					return nil, err
				}
				return f(conn), nil
			},
		})

	}

	// return the ordered graph for plugins
	return plugin.Graph(config.DisabledPlugins), nil
}

type proxyClients struct {
	m       sync.Mutex
	clients map[string]*grpc.ClientConn
}

func (pc *proxyClients) getClient(address string) (*grpc.ClientConn, error) {
	pc.m.Lock()
	defer pc.m.Unlock()
	if pc.clients == nil {
		pc.clients = map[string]*grpc.ClientConn{}
	} else if c, ok := pc.clients[address]; ok {
		return c, nil
	}

	gopts := []grpc.DialOption{
		grpc.WithInsecure(),
		grpc.WithBackoffMaxDelay(3 * time.Second),
		grpc.WithDialer(dialer.Dialer),

		// TODO(stevvooe): We may need to allow configuration of this on the client.
		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(defaults.DefaultMaxRecvMsgSize)),
		grpc.WithDefaultCallOptions(grpc.MaxCallSendMsgSize(defaults.DefaultMaxSendMsgSize)),
	}

	conn, err := grpc.Dial(dialer.DialAddress(address), gopts...)
	if err != nil {
		return nil, errors.Wrapf(err, "failed to dial %q", address)
	}

	pc.clients[address] = conn

	return conn, nil
}

func trapClosedConnErr(err error) error {
	if err == nil {
		return nil
	}
	if strings.Contains(err.Error(), "use of closed network connection") {
		return nil
	}
	return err
}
