package client

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

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

var (
	v2Prefix   = "/v2/keys"
	ErrTimeout = context.DeadlineExceeded
)

// transport mimics http.Transport to provide an interface which can be
// substituted for testing (since the RoundTripper interface alone does not
// require the CancelRequest method)
type transport interface {
	http.RoundTripper
	CancelRequest(req *http.Request)
}

type httpClient struct {
	transport transport
	endpoint  url.URL
	timeout   time.Duration
}

func NewHTTPClient(tr *http.Transport, ep string, timeout time.Duration) (*httpClient, error) {
	u, err := url.Parse(ep)
	if err != nil {
		return nil, err
	}

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

	return c, nil
}

func (c *httpClient) SetPrefix(p string) {
	v2Prefix = p
}

func (c *httpClient) 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
	}

	ctx, cancel := context.WithTimeout(context.Background(), c.timeout)
	httpresp, body, err := c.do(ctx, create)
	cancel()

	if err != nil {
		return nil, err
	}

	return unmarshalHTTPResponse(httpresp.StatusCode, body)
}

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

	ctx, cancel := context.WithTimeout(context.Background(), c.timeout)
	httpresp, body, err := c.do(ctx, get)
	cancel()

	if err != nil {
		return nil, err
	}

	return unmarshalHTTPResponse(httpresp.StatusCode, body)
}

type roundTripResponse struct {
	resp *http.Response
	err  error
}

func (c *httpClient) do(ctx context.Context, act httpAction) (*http.Response, []byte, error) {
	req := act.httpRequest(c.endpoint)

	rtchan := make(chan roundTripResponse, 1)
	go func() {
		resp, err := c.transport.RoundTrip(req)
		rtchan <- roundTripResponse{resp: resp, err: err}
		close(rtchan)
	}()

	var resp *http.Response
	var err error

	select {
	case rtresp := <-rtchan:
		resp, err = rtresp.resp, rtresp.err
	case <-ctx.Done():
		c.transport.CancelRequest(req)
		// wait for request to actually exit before continuing
		<-rtchan
		err = ctx.Err()
	}

	// always check for resp nil-ness to deal with possible
	// race conditions between channels above
	defer func() {
		if resp != nil {
			resp.Body.Close()
		}
	}()

	if err != nil {
		return nil, nil, err
	}

	body, err := ioutil.ReadAll(resp.Body)
	return resp, body, err
}

func (c *httpClient) Watch(key string, idx uint64) Watcher {
	return &httpWatcher{
		httpClient: *c,
		nextWait: waitAction{
			Key:       key,
			WaitIndex: idx,
			Recursive: false,
		},
	}
}

func (c *httpClient) RecursiveWatch(key string, idx uint64) Watcher {
	return &httpWatcher{
		httpClient: *c,
		nextWait: waitAction{
			Key:       key,
			WaitIndex: idx,
			Recursive: true,
		},
	}
}

type httpWatcher struct {
	httpClient
	nextWait waitAction
}

func (hw *httpWatcher) Next() (*Response, error) {
	httpresp, body, err := hw.httpClient.do(context.Background(), &hw.nextWait)
	if err != nil {
		return nil, err
	}

	resp, err := unmarshalHTTPResponse(httpresp.StatusCode, body)
	if err != nil {
		return nil, err
	}

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

func v2URL(ep url.URL, key string) *url.URL {
	ep.Path = path.Join(ep.Path, v2Prefix, key)
	return &ep
}

type httpAction interface {
	httpRequest(url.URL) *http.Request
}

type getAction struct {
	Key       string
	Recursive bool
}

func (g *getAction) httpRequest(ep url.URL) *http.Request {
	u := v2URL(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 := v2URL(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 := v2URL(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)
}