/*
   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 client

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

	"github.com/coreos/etcd/Godeps/_workspace/src/code.google.com/p/go.net/context"
)

var (
	DefaultV2KeysPrefix = "/v2/keys"
)

var (
	ErrUnavailable = errors.New("client: no available etcd endpoints")
	ErrNoLeader    = errors.New("client: no leader")
	ErrKeyNoExist  = errors.New("client: key does not exist")
	ErrKeyExists   = errors.New("client: key already exists")
)

func NewKeysAPI(tr *http.Transport, ep string, to time.Duration) (KeysAPI, error) {
	return newHTTPKeysAPIWithPrefix(tr, ep, to, DefaultV2KeysPrefix)
}

func NewDiscoveryKeysAPI(tr *http.Transport, ep string, to time.Duration) (KeysAPI, error) {
	return newHTTPKeysAPIWithPrefix(tr, ep, to, "")
}

func newHTTPKeysAPIWithPrefix(tr *http.Transport, ep string, to time.Duration, prefix string) (*httpKeysAPI, error) {
	u, err := url.Parse(ep)
	if err != nil {
		return nil, err
	}

	u.Path = path.Join(u.Path, prefix)

	c := &httpClient{
		transport: tr,
		endpoint:  *u,
		timeout:   to,
	}

	kAPI := httpKeysAPI{
		client: c,
	}

	return &kAPI, nil
}

type KeysAPI interface {
	Create(key, value string, ttl time.Duration) (*Response, error)
	Get(key string) (*Response, error)
	Watch(key string, idx uint64) Watcher
	RecursiveWatch(key string, idx uint64) Watcher
}

type Watcher interface {
	Next() (*Response, error)
}

type Response struct {
	Action   string `json:"action"`
	Node     *Node  `json:"node"`
	PrevNode *Node  `json:"prevNode"`
}

type Nodes []*Node
type Node struct {
	Key           string `json:"key"`
	Value         string `json:"value"`
	Nodes         Nodes  `json:"nodes"`
	ModifiedIndex uint64 `json:"modifiedIndex"`
	CreatedIndex  uint64 `json:"createdIndex"`
}

func (n *Node) String() string {
	return fmt.Sprintf("{Key: %s, CreatedIndex: %d, ModifiedIndex: %d}", n.Key, n.CreatedIndex, n.ModifiedIndex)
}

type httpKeysAPI struct {
	client *httpClient
}

func (k *httpKeysAPI) Create(key, val string, ttl time.Duration) (*Response, error) {
	create := &createAction{
		Key:   key,
		Value: val,
	}
	if ttl >= 0 {
		uttl := uint64(ttl.Seconds())
		create.TTL = &uttl
	}

	code, body, err := k.client.doWithTimeout(create)
	if err != nil {
		return nil, err
	}

	return unmarshalHTTPResponse(code, body)
}

func (k *httpKeysAPI) Get(key string) (*Response, error) {
	get := &getAction{
		Key:       key,
		Recursive: false,
	}

	code, body, err := k.client.doWithTimeout(get)
	if err != nil {
		return nil, err
	}

	return unmarshalHTTPResponse(code, body)
}

func (k *httpKeysAPI) Watch(key string, idx uint64) Watcher {
	return &httpWatcher{
		client: k.client,
		nextWait: waitAction{
			Key:       key,
			WaitIndex: idx,
			Recursive: false,
		},
	}
}

func (k *httpKeysAPI) RecursiveWatch(key string, idx uint64) Watcher {
	return &httpWatcher{
		client: k.client,
		nextWait: waitAction{
			Key:       key,
			WaitIndex: idx,
			Recursive: true,
		},
	}
}

type httpWatcher struct {
	client   *httpClient
	nextWait waitAction
}

func (hw *httpWatcher) Next() (*Response, error) {
	//TODO(bcwaldon): This needs to be cancellable by the calling user
	code, body, err := hw.client.do(context.Background(), &hw.nextWait)
	if err != nil {
		return nil, err
	}

	resp, err := unmarshalHTTPResponse(code, body)
	if err != nil {
		return nil, err
	}

	hw.nextWait.WaitIndex = resp.Node.ModifiedIndex + 1
	return resp, nil
}

// v2KeysURL forms a URL representing the location of a key. The provided
// endpoint must be the root of the etcd keys API. For example, a valid
// endpoint probably has the path "/v2/keys".
func v2KeysURL(ep url.URL, key string) *url.URL {
	ep.Path = path.Join(ep.Path, key)
	return &ep
}

type getAction struct {
	Key       string
	Recursive bool
}

func (g *getAction) httpRequest(ep url.URL) *http.Request {
	u := v2KeysURL(ep, g.Key)

	params := u.Query()
	params.Set("recursive", strconv.FormatBool(g.Recursive))
	u.RawQuery = params.Encode()

	req, _ := http.NewRequest("GET", u.String(), nil)
	return req
}

type waitAction struct {
	Key       string
	WaitIndex uint64
	Recursive bool
}

func (w *waitAction) httpRequest(ep url.URL) *http.Request {
	u := v2KeysURL(ep, w.Key)

	params := u.Query()
	params.Set("wait", "true")
	params.Set("waitIndex", strconv.FormatUint(w.WaitIndex, 10))
	params.Set("recursive", strconv.FormatBool(w.Recursive))
	u.RawQuery = params.Encode()

	req, _ := http.NewRequest("GET", u.String(), nil)
	return req
}

type createAction struct {
	Key   string
	Value string
	TTL   *uint64
}

func (c *createAction) httpRequest(ep url.URL) *http.Request {
	u := v2KeysURL(ep, c.Key)

	params := u.Query()
	params.Set("prevExist", "false")
	u.RawQuery = params.Encode()

	form := url.Values{}
	form.Add("value", c.Value)
	if c.TTL != nil {
		form.Add("ttl", strconv.FormatUint(*c.TTL, 10))
	}
	body := strings.NewReader(form.Encode())

	req, _ := http.NewRequest("PUT", u.String(), body)
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	return req
}

func unmarshalHTTPResponse(code int, body []byte) (res *Response, err error) {
	switch code {
	case http.StatusOK, http.StatusCreated:
		res, err = unmarshalSuccessfulResponse(body)
	default:
		err = unmarshalErrorResponse(code)
	}

	return
}

func unmarshalSuccessfulResponse(body []byte) (*Response, error) {
	var res Response
	err := json.Unmarshal(body, &res)
	if err != nil {
		return nil, err
	}

	return &res, nil
}

func unmarshalErrorResponse(code int) error {
	switch code {
	case http.StatusNotFound:
		return ErrKeyNoExist
	case http.StatusPreconditionFailed:
		return ErrKeyExists
	case http.StatusInternalServerError:
		// this isn't necessarily true
		return ErrNoLeader
	default:
	}

	return fmt.Errorf("unrecognized HTTP status code %d", code)
}