// 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 client

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"path"

	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
	"github.com/coreos/etcd/etcdserver/etcdhttp/httptypes"
	"github.com/coreos/etcd/pkg/types"
)

var (
	defaultV2MembersPrefix = "/v2/members"
)

type Member httptypes.Member

// NewMembersAPI constructs a new MembersAPI that uses HTTP to
// interact with etcd's membership API.
func NewMembersAPI(c Client) MembersAPI {
	return &httpMembersAPI{
		client: c,
	}
}

type MembersAPI interface {
	// List enumerates the current cluster membership
	List(ctx context.Context) ([]Member, error)

	// Add instructs etcd to accept a new Member into the cluster
	Add(ctx context.Context, peerURL string) (*Member, error)

	// Remove demotes an existing Member out of the cluster
	Remove(ctx context.Context, mID string) error
}

type httpMembersAPI struct {
	client httpClient
}

func (m *httpMembersAPI) List(ctx context.Context) ([]Member, error) {
	req := &membersAPIActionList{}
	resp, body, err := m.client.Do(ctx, req)
	if err != nil {
		return nil, err
	}

	if err := assertStatusCode(resp.StatusCode, http.StatusOK); err != nil {
		return nil, err
	}

	var mCollection httptypes.MemberCollection
	if err := json.Unmarshal(body, &mCollection); err != nil {
		return nil, err
	}

	ms := make([]Member, len(mCollection))
	for i, m := range mCollection {
		m := Member(m)
		ms[i] = m
	}
	return ms, nil
}

func (m *httpMembersAPI) Add(ctx context.Context, peerURL string) (*Member, error) {
	urls, err := types.NewURLs([]string{peerURL})
	if err != nil {
		return nil, err
	}

	req := &membersAPIActionAdd{peerURLs: urls}
	resp, body, err := m.client.Do(ctx, req)
	if err != nil {
		return nil, err
	}

	if err := assertStatusCode(resp.StatusCode, http.StatusCreated, http.StatusConflict); err != nil {
		return nil, err
	}

	if resp.StatusCode != http.StatusCreated {
		var httperr httptypes.HTTPError
		if err := json.Unmarshal(body, &httperr); err != nil {
			return nil, err
		}
		return nil, httperr
	}

	var memb Member
	if err := json.Unmarshal(body, &memb); err != nil {
		return nil, err
	}

	return &memb, nil
}

func (m *httpMembersAPI) Remove(ctx context.Context, memberID string) error {
	req := &membersAPIActionRemove{memberID: memberID}
	resp, _, err := m.client.Do(ctx, req)
	if err != nil {
		return err
	}

	return assertStatusCode(resp.StatusCode, http.StatusNoContent)
}

type membersAPIActionList struct{}

func (l *membersAPIActionList) HTTPRequest(ep url.URL) *http.Request {
	u := v2MembersURL(ep)
	req, _ := http.NewRequest("GET", u.String(), nil)
	return req
}

type membersAPIActionRemove struct {
	memberID string
}

func (d *membersAPIActionRemove) HTTPRequest(ep url.URL) *http.Request {
	u := v2MembersURL(ep)
	u.Path = path.Join(u.Path, d.memberID)
	req, _ := http.NewRequest("DELETE", u.String(), nil)
	return req
}

type membersAPIActionAdd struct {
	peerURLs types.URLs
}

func (a *membersAPIActionAdd) HTTPRequest(ep url.URL) *http.Request {
	u := v2MembersURL(ep)
	m := httptypes.MemberCreateRequest{PeerURLs: a.peerURLs}
	b, _ := json.Marshal(&m)
	req, _ := http.NewRequest("POST", u.String(), bytes.NewReader(b))
	req.Header.Set("Content-Type", "application/json")
	return req
}

func assertStatusCode(got int, want ...int) (err error) {
	for _, w := range want {
		if w == got {
			return nil
		}
	}
	return fmt.Errorf("unexpected status code %d", got)
}

// v2MembersURL add the necessary path to the provided endpoint
// to route requests to the default v2 members API.
func v2MembersURL(ep url.URL) *url.URL {
	ep.Path = path.Join(ep.Path, defaultV2MembersPrefix)
	return &ep
}