// Copyright 2015 CoreOS, 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 etcdserver

import (
	"crypto/sha1"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"log"
	"net/url"
	"path"
	"sort"
	"strings"
	"sync"

	"github.com/coreos/etcd/pkg/flags"
	"github.com/coreos/etcd/pkg/netutil"
	"github.com/coreos/etcd/pkg/types"
	"github.com/coreos/etcd/raft/raftpb"
	"github.com/coreos/etcd/store"
)

const (
	raftAttributesSuffix = "raftAttributes"
	attributesSuffix     = "attributes"
)

type ClusterInfo interface {
	// ID returns the cluster ID
	ID() types.ID
	// ClientURLs returns an aggregate set of all URLs on which this
	// cluster is listening for client requests
	ClientURLs() []string
	// Members returns a slice of members sorted by their ID
	Members() []*Member
	// Member retrieves a particular member based on ID, or nil if the
	// member does not exist in the cluster
	Member(id types.ID) *Member
	// IsIDRemoved checks whether the given ID has been removed from this
	// cluster at some point in the past
	IsIDRemoved(id types.ID) bool
}

// Cluster is a list of Members that belong to the same raft cluster
type Cluster struct {
	id      types.ID
	token   string
	members map[types.ID]*Member
	// removed contains the ids of removed members in the cluster.
	// removed id cannot be reused.
	removed map[types.ID]bool
	store   store.Store
	sync.Mutex
}

// NewClusterFromString returns a Cluster instantiated from the given cluster token
// and cluster string, by parsing members from a set of discovery-formatted
// names-to-IPs, like:
// mach0=http://1.1.1.1,mach0=http://2.2.2.2,mach1=http://3.3.3.3,mach2=http://4.4.4.4
func NewClusterFromString(token string, cluster string) (*Cluster, error) {
	c := newCluster(token)

	v, err := url.ParseQuery(strings.Replace(cluster, ",", "&", -1))
	if err != nil {
		return nil, err
	}
	for name, urls := range v {
		if len(urls) == 0 || urls[0] == "" {
			return nil, fmt.Errorf("Empty URL given for %q", name)
		}
		purls := &flags.URLsValue{}
		if err := purls.Set(strings.Join(urls, ",")); err != nil {
			return nil, err
		}
		m := NewMember(name, types.URLs(*purls), c.token, nil)
		if _, ok := c.members[m.ID]; ok {
			return nil, fmt.Errorf("Member exists with identical ID %v", m)
		}
		c.members[m.ID] = m
	}
	c.genID()
	return c, nil
}

func NewClusterFromStore(token string, st store.Store) *Cluster {
	c := newCluster(token)
	c.store = st
	c.members, c.removed = membersFromStore(c.store)
	return c
}

func NewClusterFromMembers(token string, id types.ID, membs []*Member) *Cluster {
	c := newCluster(token)
	c.id = id
	for _, m := range membs {
		c.members[m.ID] = m
	}
	return c
}

func newCluster(token string) *Cluster {
	return &Cluster{
		token:   token,
		members: make(map[types.ID]*Member),
		removed: make(map[types.ID]bool),
	}
}

func (c *Cluster) ID() types.ID { return c.id }

func (c *Cluster) Members() []*Member {
	c.Lock()
	defer c.Unlock()
	var sms SortableMemberSlice
	for _, m := range c.members {
		sms = append(sms, m.Clone())
	}
	sort.Sort(sms)
	return []*Member(sms)
}

func (c *Cluster) Member(id types.ID) *Member {
	c.Lock()
	defer c.Unlock()
	return c.members[id].Clone()
}

// MemberByName returns a Member with the given name if exists.
// If more than one member has the given name, it will panic.
func (c *Cluster) MemberByName(name string) *Member {
	c.Lock()
	defer c.Unlock()
	var memb *Member
	for _, m := range c.members {
		if m.Name == name {
			if memb != nil {
				log.Panicf("two members with the given name %q exist", name)
			}
			memb = m
		}
	}
	return memb.Clone()
}

func (c *Cluster) MemberIDs() []types.ID {
	c.Lock()
	defer c.Unlock()
	var ids []types.ID
	for _, m := range c.members {
		ids = append(ids, m.ID)
	}
	sort.Sort(types.IDSlice(ids))
	return ids
}

func (c *Cluster) IsIDRemoved(id types.ID) bool {
	c.Lock()
	defer c.Unlock()
	return c.removed[id]
}

// PeerURLs returns a list of all peer addresses.
// The returned list is sorted in ascending lexicographical order.
func (c *Cluster) PeerURLs() []string {
	c.Lock()
	defer c.Unlock()
	urls := make([]string, 0)
	for _, p := range c.members {
		for _, addr := range p.PeerURLs {
			urls = append(urls, addr)
		}
	}
	sort.Strings(urls)
	return urls
}

// ClientURLs returns a list of all client addresses.
// The returned list is sorted in ascending lexicographical order.
func (c *Cluster) ClientURLs() []string {
	c.Lock()
	defer c.Unlock()
	urls := make([]string, 0)
	for _, p := range c.members {
		for _, url := range p.ClientURLs {
			urls = append(urls, url)
		}
	}
	sort.Strings(urls)
	return urls
}

func (c *Cluster) String() string {
	c.Lock()
	defer c.Unlock()
	sl := []string{}
	for _, m := range c.members {
		for _, u := range m.PeerURLs {
			sl = append(sl, fmt.Sprintf("%s=%s", m.Name, u))
		}
	}
	sort.Strings(sl)
	return strings.Join(sl, ",")
}

func (c *Cluster) genID() {
	mIDs := c.MemberIDs()
	b := make([]byte, 8*len(mIDs))
	for i, id := range mIDs {
		binary.BigEndian.PutUint64(b[8*i:], uint64(id))
	}
	hash := sha1.Sum(b)
	c.id = types.ID(binary.BigEndian.Uint64(hash[:8]))
}

func (c *Cluster) SetID(id types.ID) { c.id = id }

func (c *Cluster) SetStore(st store.Store) { c.store = st }

func (c *Cluster) Recover() {
	c.members, c.removed = membersFromStore(c.store)
}

// ValidateConfigurationChange takes a proposed ConfChange and
// ensures that it is still valid.
func (c *Cluster) ValidateConfigurationChange(cc raftpb.ConfChange) error {
	members, removed := membersFromStore(c.store)
	id := types.ID(cc.NodeID)
	if removed[id] {
		return ErrIDRemoved
	}
	switch cc.Type {
	case raftpb.ConfChangeAddNode:
		if members[id] != nil {
			return ErrIDExists
		}
		urls := make(map[string]bool)
		for _, m := range members {
			for _, u := range m.PeerURLs {
				urls[u] = true
			}
		}
		m := new(Member)
		if err := json.Unmarshal(cc.Context, m); err != nil {
			log.Panicf("unmarshal member should never fail: %v", err)
		}
		for _, u := range m.PeerURLs {
			if urls[u] {
				return ErrPeerURLexists
			}
		}
	case raftpb.ConfChangeRemoveNode:
		if members[id] == nil {
			return ErrIDNotFound
		}
	case raftpb.ConfChangeUpdateNode:
		if members[id] == nil {
			return ErrIDNotFound
		}
		urls := make(map[string]bool)
		for _, m := range members {
			if m.ID == id {
				continue
			}
			for _, u := range m.PeerURLs {
				urls[u] = true
			}
		}
		m := new(Member)
		if err := json.Unmarshal(cc.Context, m); err != nil {
			log.Panicf("unmarshal member should never fail: %v", err)
		}
		for _, u := range m.PeerURLs {
			if urls[u] {
				return ErrPeerURLexists
			}
		}
	default:
		log.Panicf("ConfChange type should be either AddNode, RemoveNode or UpdateNode")
	}
	return nil
}

// AddMember adds a new Member into the cluster, and saves the given member's
// raftAttributes into the store. The given member should have empty attributes.
// A Member with a matching id must not exist.
func (c *Cluster) AddMember(m *Member) {
	c.Lock()
	defer c.Unlock()
	b, err := json.Marshal(m.RaftAttributes)
	if err != nil {
		log.Panicf("marshal raftAttributes should never fail: %v", err)
	}
	p := path.Join(memberStoreKey(m.ID), raftAttributesSuffix)
	if _, err := c.store.Create(p, false, string(b), false, store.Permanent); err != nil {
		log.Panicf("create raftAttributes should never fail: %v", err)
	}
	c.members[m.ID] = m
}

// RemoveMember removes a member from the store.
// The given id MUST exist, or the function panics.
func (c *Cluster) RemoveMember(id types.ID) {
	c.Lock()
	defer c.Unlock()
	if _, err := c.store.Delete(memberStoreKey(id), true, true); err != nil {
		log.Panicf("delete member should never fail: %v", err)
	}
	delete(c.members, id)
	if _, err := c.store.Create(removedMemberStoreKey(id), false, "", false, store.Permanent); err != nil {
		log.Panicf("create removedMember should never fail: %v", err)
	}
	c.removed[id] = true
}

func (c *Cluster) UpdateAttributes(id types.ID, attr Attributes) {
	c.Lock()
	defer c.Unlock()
	c.members[id].Attributes = attr
	// TODO: update store in this function
}

func (c *Cluster) UpdateRaftAttributes(id types.ID, raftAttr RaftAttributes) {
	c.Lock()
	defer c.Unlock()
	b, err := json.Marshal(raftAttr)
	if err != nil {
		log.Panicf("marshal raftAttributes should never fail: %v", err)
	}
	p := path.Join(memberStoreKey(id), raftAttributesSuffix)
	if _, err := c.store.Update(p, string(b), store.Permanent); err != nil {
		log.Panicf("update raftAttributes should never fail: %v", err)
	}
	c.members[id].RaftAttributes = raftAttr
}

func membersFromStore(st store.Store) (map[types.ID]*Member, map[types.ID]bool) {
	members := make(map[types.ID]*Member)
	removed := make(map[types.ID]bool)
	e, err := st.Get(storeMembersPrefix, true, true)
	if err != nil {
		if isKeyNotFound(err) {
			return members, removed
		}
		log.Panicf("get storeMembers should never fail: %v", err)
	}
	for _, n := range e.Node.Nodes {
		m, err := nodeToMember(n)
		if err != nil {
			log.Panicf("nodeToMember should never fail: %v", err)
		}
		members[m.ID] = m
	}

	e, err = st.Get(storeRemovedMembersPrefix, true, true)
	if err != nil {
		if isKeyNotFound(err) {
			return members, removed
		}
		log.Panicf("get storeRemovedMembers should never fail: %v", err)
	}
	for _, n := range e.Node.Nodes {
		removed[mustParseMemberIDFromKey(n.Key)] = true
	}
	return members, removed
}

// ValidateClusterAndAssignIDs validates the local cluster by matching the PeerURLs
// with the existing cluster. If the validation succeeds, it assigns the IDs
// from the existing cluster to the local cluster.
// If the validation fails, an error will be returned.
func ValidateClusterAndAssignIDs(local *Cluster, existing *Cluster) error {
	ems := existing.Members()
	lms := local.Members()
	if len(ems) != len(lms) {
		return fmt.Errorf("member count is unequal")
	}
	sort.Sort(SortableMemberSliceByPeerURLs(ems))
	sort.Sort(SortableMemberSliceByPeerURLs(lms))

	for i := range ems {
		// TODO: Remove URLStringsEqual after improvement of using hostnames #2150 #2123
		if !netutil.URLStringsEqual(ems[i].PeerURLs, lms[i].PeerURLs) {
			return fmt.Errorf("unmatched member while checking PeerURLs")
		}
		lms[i].ID = ems[i].ID
	}
	local.members = make(map[types.ID]*Member)
	for _, m := range lms {
		local.members[m.ID] = m
	}
	return nil
}