/*
   Copyright 2014 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 etcdhttp

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/coreos/etcd/Godeps/_workspace/src/github.com/jonboulle/clockwork"
	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
	etcdErr "github.com/coreos/etcd/error"
	"github.com/coreos/etcd/etcdserver"
	"github.com/coreos/etcd/etcdserver/etcdhttp/httptypes"
	"github.com/coreos/etcd/etcdserver/etcdserverpb"
	"github.com/coreos/etcd/etcdserver/stats"
	"github.com/coreos/etcd/pkg/types"
	"github.com/coreos/etcd/store"
	"github.com/coreos/etcd/version"
)

const (
	keysPrefix               = "/v2/keys"
	deprecatedMachinesPrefix = "/v2/machines"
	membersPrefix            = "/v2/members"
	statsPrefix              = "/v2/stats"
	versionPrefix            = "/version"
)

// NewClientHandler generates a muxed http.Handler with the given parameters to serve etcd client requests.
func NewClientHandler(server *etcdserver.EtcdServer) http.Handler {
	kh := &keysHandler{
		server:      server,
		clusterInfo: server.Cluster,
		timer:       server,
		timeout:     defaultServerTimeout,
	}

	sh := &statsHandler{
		stats: server,
	}

	mh := &membersHandler{
		server:      server,
		clusterInfo: server.Cluster,
		clock:       clockwork.NewRealClock(),
	}

	dmh := &deprecatedMachinesHandler{
		clusterInfo: server.Cluster,
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/", http.NotFound)
	mux.HandleFunc(versionPrefix, serveVersion)
	mux.Handle(keysPrefix, kh)
	mux.Handle(keysPrefix+"/", kh)
	mux.HandleFunc(statsPrefix+"/store", sh.serveStore)
	mux.HandleFunc(statsPrefix+"/self", sh.serveSelf)
	mux.HandleFunc(statsPrefix+"/leader", sh.serveLeader)
	mux.Handle(membersPrefix, mh)
	mux.Handle(membersPrefix+"/", mh)
	mux.Handle(deprecatedMachinesPrefix, dmh)
	return mux
}

type keysHandler struct {
	server      etcdserver.Server
	clusterInfo etcdserver.ClusterInfo
	timer       etcdserver.RaftTimer
	timeout     time.Duration
}

func (h *keysHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "HEAD", "GET", "PUT", "POST", "DELETE") {
		return
	}
	w.Header().Set("X-Etcd-Cluster-ID", h.clusterInfo.ID().String())

	ctx, cancel := context.WithTimeout(context.Background(), h.timeout)
	defer cancel()

	rr, err := parseKeyRequest(r, clockwork.NewRealClock())
	if err != nil {
		writeError(w, err)
		return
	}

	resp, err := h.server.Do(ctx, rr)
	if err != nil {
		err = trimErrorPrefix(err, etcdserver.StoreKeysPrefix)
		writeError(w, err)
		return
	}

	switch {
	case resp.Event != nil:
		if err := writeKeyEvent(w, resp.Event, h.timer); err != nil {
			// Should never be reached
			log.Printf("error writing event: %v", err)
		}
	case resp.Watcher != nil:
		ctx, cancel := context.WithTimeout(context.Background(), defaultWatchTimeout)
		defer cancel()
		handleKeyWatch(ctx, w, resp.Watcher, rr.Stream, h.timer)
	default:
		writeError(w, errors.New("received response with no Event/Watcher!"))
	}
}

type deprecatedMachinesHandler struct {
	clusterInfo etcdserver.ClusterInfo
}

func (h *deprecatedMachinesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET", "HEAD") {
		return
	}
	endpoints := h.clusterInfo.ClientURLs()
	w.Write([]byte(strings.Join(endpoints, ", ")))
}

type membersHandler struct {
	server      etcdserver.Server
	clusterInfo etcdserver.ClusterInfo
	clock       clockwork.Clock
}

func (h *membersHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET", "POST", "DELETE", "PUT") {
		return
	}
	w.Header().Set("X-Etcd-Cluster-ID", h.clusterInfo.ID().String())

	ctx, cancel := context.WithTimeout(context.Background(), defaultServerTimeout)
	defer cancel()

	switch r.Method {
	case "GET":
		if trimPrefix(r.URL.Path, membersPrefix) != "" {
			writeError(w, httptypes.NewHTTPError(http.StatusNotFound, "Not found"))
			return
		}
		mc := newMemberCollection(h.clusterInfo.Members())
		w.Header().Set("Content-Type", "application/json")
		if err := json.NewEncoder(w).Encode(mc); err != nil {
			log.Printf("etcdhttp: %v", err)
		}
	case "POST":
		req := httptypes.MemberCreateRequest{}
		if ok := unmarshalRequest(r, &req, w); !ok {
			return
		}
		now := h.clock.Now()
		m := etcdserver.NewMember("", req.PeerURLs, "", &now)
		err := h.server.AddMember(ctx, *m)
		switch {
		case err == etcdserver.ErrIDExists || err == etcdserver.ErrPeerURLexists:
			writeError(w, httptypes.NewHTTPError(http.StatusConflict, err.Error()))
			return
		case err != nil:
			log.Printf("etcdhttp: error adding node %s: %v", m.ID, err)
			writeError(w, err)
			return
		}
		res := newMember(m)
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		if err := json.NewEncoder(w).Encode(res); err != nil {
			log.Printf("etcdhttp: %v", err)
		}
	case "DELETE":
		id, ok := getID(r.URL.Path, w)
		if !ok {
			return
		}
		err := h.server.RemoveMember(ctx, uint64(id))
		switch {
		case err == etcdserver.ErrIDRemoved:
			writeError(w, httptypes.NewHTTPError(http.StatusGone, fmt.Sprintf("Member permanently removed: %s", id)))
		case err == etcdserver.ErrIDNotFound:
			writeError(w, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", id)))
		case err != nil:
			log.Printf("etcdhttp: error removing node %s: %v", id, err)
			writeError(w, err)
		default:
			w.WriteHeader(http.StatusNoContent)
		}
	case "PUT":
		id, ok := getID(r.URL.Path, w)
		if !ok {
			return
		}
		req := httptypes.MemberUpdateRequest{}
		if ok := unmarshalRequest(r, &req, w); !ok {
			return
		}
		m := etcdserver.Member{
			ID:             id,
			RaftAttributes: etcdserver.RaftAttributes{PeerURLs: req.PeerURLs.StringSlice()},
		}
		err := h.server.UpdateMember(ctx, m)
		switch {
		case err == etcdserver.ErrPeerURLexists:
			writeError(w, httptypes.NewHTTPError(http.StatusConflict, err.Error()))
		case err == etcdserver.ErrIDNotFound:
			writeError(w, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", id)))
		case err != nil:
			log.Printf("etcdhttp: error updating node %s: %v", m.ID, err)
			writeError(w, err)
		default:
			w.WriteHeader(http.StatusNoContent)
		}
	}
}

type statsHandler struct {
	stats stats.Stats
}

func (h *statsHandler) serveStore(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET") {
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(h.stats.StoreStats())
}

func (h *statsHandler) serveSelf(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET") {
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(h.stats.SelfStats())
}

func (h *statsHandler) serveLeader(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET") {
		return
	}
	stats := h.stats.LeaderStats()
	if stats == nil {
		writeError(w, httptypes.NewHTTPError(http.StatusForbidden, "not current leader"))
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(stats)
}

func serveVersion(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET") {
		return
	}
	w.Write([]byte("etcd " + version.Version))
}

// parseKeyRequest converts a received http.Request on keysPrefix to
// a server Request, performing validation of supplied fields as appropriate.
// If any validation fails, an empty Request and non-nil error is returned.
func parseKeyRequest(r *http.Request, clock clockwork.Clock) (etcdserverpb.Request, error) {
	emptyReq := etcdserverpb.Request{}

	err := r.ParseForm()
	if err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidForm,
			err.Error(),
		)
	}

	if !strings.HasPrefix(r.URL.Path, keysPrefix) {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidForm,
			"incorrect key prefix",
		)
	}
	p := path.Join(etcdserver.StoreKeysPrefix, r.URL.Path[len(keysPrefix):])

	var pIdx, wIdx uint64
	if pIdx, err = getUint64(r.Form, "prevIndex"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeIndexNaN,
			`invalid value for "prevIndex"`,
		)
	}
	if wIdx, err = getUint64(r.Form, "waitIndex"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeIndexNaN,
			`invalid value for "waitIndex"`,
		)
	}

	var rec, sort, wait, dir, quorum, stream bool
	if rec, err = getBool(r.Form, "recursive"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "recursive"`,
		)
	}
	if sort, err = getBool(r.Form, "sorted"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "sorted"`,
		)
	}
	if wait, err = getBool(r.Form, "wait"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "wait"`,
		)
	}
	// TODO(jonboulle): define what parameters dir is/isn't compatible with?
	if dir, err = getBool(r.Form, "dir"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "dir"`,
		)
	}
	if quorum, err = getBool(r.Form, "quorum"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "quorum"`,
		)
	}
	if stream, err = getBool(r.Form, "stream"); err != nil {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`invalid value for "stream"`,
		)
	}

	if wait && r.Method != "GET" {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodeInvalidField,
			`"wait" can only be used with GET requests`,
		)
	}

	pV := r.FormValue("prevValue")
	if _, ok := r.Form["prevValue"]; ok && pV == "" {
		return emptyReq, etcdErr.NewRequestError(
			etcdErr.EcodePrevValueRequired,
			`"prevValue" cannot be empty`,
		)
	}

	// TTL is nullable, so leave it null if not specified
	// or an empty string
	var ttl *uint64
	if len(r.FormValue("ttl")) > 0 {
		i, err := getUint64(r.Form, "ttl")
		if err != nil {
			return emptyReq, etcdErr.NewRequestError(
				etcdErr.EcodeTTLNaN,
				`invalid value for "ttl"`,
			)
		}
		ttl = &i
	}

	// prevExist is nullable, so leave it null if not specified
	var pe *bool
	if _, ok := r.Form["prevExist"]; ok {
		bv, err := getBool(r.Form, "prevExist")
		if err != nil {
			return emptyReq, etcdErr.NewRequestError(
				etcdErr.EcodeInvalidField,
				"invalid value for prevExist",
			)
		}
		pe = &bv
	}

	rr := etcdserverpb.Request{
		Method:    r.Method,
		Path:      p,
		Val:       r.FormValue("value"),
		Dir:       dir,
		PrevValue: pV,
		PrevIndex: pIdx,
		PrevExist: pe,
		Wait:      wait,
		Since:     wIdx,
		Recursive: rec,
		Sorted:    sort,
		Quorum:    quorum,
		Stream:    stream,
	}

	if pe != nil {
		rr.PrevExist = pe
	}

	// Null TTL is equivalent to unset Expiration
	if ttl != nil {
		expr := time.Duration(*ttl) * time.Second
		rr.Expiration = clock.Now().Add(expr).UnixNano()
	}

	return rr, nil
}

// writeKeyEvent trims the prefix of key path in a single Event under
// StoreKeysPrefix, serializes it and writes the resulting JSON to the given
// ResponseWriter, along with the appropriate headers.
func writeKeyEvent(w http.ResponseWriter, ev *store.Event, rt etcdserver.RaftTimer) error {
	if ev == nil {
		return errors.New("cannot write empty Event!")
	}
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("X-Etcd-Index", fmt.Sprint(ev.EtcdIndex))
	w.Header().Set("X-Raft-Index", fmt.Sprint(rt.Index()))
	w.Header().Set("X-Raft-Term", fmt.Sprint(rt.Term()))

	if ev.IsCreated() {
		w.WriteHeader(http.StatusCreated)
	}

	ev = trimEventPrefix(ev, etcdserver.StoreKeysPrefix)
	return json.NewEncoder(w).Encode(ev)
}

func handleKeyWatch(ctx context.Context, w http.ResponseWriter, wa store.Watcher, stream bool, rt etcdserver.RaftTimer) {
	defer wa.Remove()
	ech := wa.EventChan()
	var nch <-chan bool
	if x, ok := w.(http.CloseNotifier); ok {
		nch = x.CloseNotify()
	}

	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("X-Etcd-Index", fmt.Sprint(wa.StartIndex()))
	w.Header().Set("X-Raft-Index", fmt.Sprint(rt.Index()))
	w.Header().Set("X-Raft-Term", fmt.Sprint(rt.Term()))
	w.WriteHeader(http.StatusOK)

	// Ensure headers are flushed early, in case of long polling
	w.(http.Flusher).Flush()

	for {
		select {
		case <-nch:
			// Client closed connection. Nothing to do.
			return
		case <-ctx.Done():
			// Timed out. net/http will close the connection for us, so nothing to do.
			return
		case ev, ok := <-ech:
			if !ok {
				// If the channel is closed this may be an indication of
				// that notifications are much more than we are able to
				// send to the client in time. Then we simply end streaming.
				return
			}
			ev = trimEventPrefix(ev, etcdserver.StoreKeysPrefix)
			if err := json.NewEncoder(w).Encode(ev); err != nil {
				// Should never be reached
				log.Printf("error writing event: %v\n", err)
				return
			}
			if !stream {
				return
			}
			w.(http.Flusher).Flush()
		}
	}
}

func trimEventPrefix(ev *store.Event, prefix string) *store.Event {
	if ev == nil {
		return nil
	}
	// Since the *Event may reference one in the store history
	// history, we must copy it before modifying
	e := ev.Clone()
	e.Node = trimNodeExternPrefix(e.Node, prefix)
	e.PrevNode = trimNodeExternPrefix(e.PrevNode, prefix)
	return e
}

func trimNodeExternPrefix(n *store.NodeExtern, prefix string) *store.NodeExtern {
	if n == nil {
		return nil
	}
	n.Key = strings.TrimPrefix(n.Key, prefix)
	for _, nn := range n.Nodes {
		nn = trimNodeExternPrefix(nn, prefix)
	}
	return n
}

func trimErrorPrefix(err error, prefix string) error {
	if e, ok := err.(*etcdErr.Error); ok {
		e.Cause = strings.TrimPrefix(e.Cause, prefix)
	}
	return err
}

func unmarshalRequest(r *http.Request, req json.Unmarshaler, w http.ResponseWriter) bool {
	ctype := r.Header.Get("Content-Type")
	if ctype != "application/json" {
		writeError(w, httptypes.NewHTTPError(http.StatusUnsupportedMediaType, fmt.Sprintf("Bad Content-Type %s, accept application/json", ctype)))
		return false
	}
	b, err := ioutil.ReadAll(r.Body)
	if err != nil {
		writeError(w, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	if err := req.UnmarshalJSON(b); err != nil {
		writeError(w, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	return true
}

func getID(p string, w http.ResponseWriter) (types.ID, bool) {
	idStr := trimPrefix(p, membersPrefix)
	if idStr == "" {
		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
		return 0, false
	}
	id, err := types.IDFromString(idStr)
	if err != nil {
		writeError(w, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", idStr)))
		return 0, false
	}
	return id, true
}

// getUint64 extracts a uint64 by the given key from a Form. If the key does
// not exist in the form, 0 is returned. If the key exists but the value is
// badly formed, an error is returned. If multiple values are present only the
// first is considered.
func getUint64(form url.Values, key string) (i uint64, err error) {
	if vals, ok := form[key]; ok {
		i, err = strconv.ParseUint(vals[0], 10, 64)
	}
	return
}

// getBool extracts a bool by the given key from a Form. If the key does not
// exist in the form, false is returned. If the key exists but the value is
// badly formed, an error is returned. If multiple values are present only the
// first is considered.
func getBool(form url.Values, key string) (b bool, err error) {
	if vals, ok := form[key]; ok {
		b, err = strconv.ParseBool(vals[0])
	}
	return
}

// trimPrefix removes a given prefix and any slash following the prefix
// e.g.: trimPrefix("foo", "foo") == trimPrefix("foo/", "foo") == ""
func trimPrefix(p, prefix string) (s string) {
	s = strings.TrimPrefix(p, prefix)
	s = strings.TrimPrefix(s, "/")
	return
}

func newMemberCollection(ms []*etcdserver.Member) *httptypes.MemberCollection {
	c := httptypes.MemberCollection(make([]httptypes.Member, len(ms)))

	for i, m := range ms {
		c[i] = newMember(m)
	}

	return &c
}

func newMember(m *etcdserver.Member) httptypes.Member {
	tm := httptypes.Member{
		ID:         m.ID.String(),
		Name:       m.Name,
		PeerURLs:   make([]string, len(m.PeerURLs)),
		ClientURLs: make([]string, len(m.ClientURLs)),
	}

	copy(tm.PeerURLs, m.PeerURLs)
	copy(tm.ClientURLs, m.ClientURLs)

	return tm
}