package pluginproxy

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/opentracing/opentracing-go"
	"golang.org/x/oauth2"

	"github.com/grafana/grafana/pkg/api/datasource"
	"github.com/grafana/grafana/pkg/bus"
	glog "github.com/grafana/grafana/pkg/infra/log"
	"github.com/grafana/grafana/pkg/login/social"
	"github.com/grafana/grafana/pkg/models"
	"github.com/grafana/grafana/pkg/plugins"
	"github.com/grafana/grafana/pkg/setting"
	"github.com/grafana/grafana/pkg/util"
	"github.com/grafana/grafana/pkg/util/proxyutil"
)

var (
	logger = glog.New("data-proxy-log")
	client = newHTTPClient()
)

type DataSourceProxy struct {
	ds        *models.DataSource
	ctx       *models.ReqContext
	targetUrl *url.URL
	proxyPath string
	route     *plugins.AppPluginRoute
	plugin    *plugins.DataSourcePlugin
	cfg       *setting.Cfg
}

type handleResponseTransport struct {
	transport http.RoundTripper
}

func (t *handleResponseTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	res, err := t.transport.RoundTrip(req)
	if err != nil {
		return nil, err
	}
	res.Header.Del("Set-Cookie")
	return res, nil
}

type httpClient interface {
	Do(req *http.Request) (*http.Response, error)
}

type logWrapper struct {
	logger glog.Logger
}

// Write writes log messages as bytes from proxy
func (lw *logWrapper) Write(p []byte) (n int, err error) {
	withoutNewline := strings.TrimSuffix(string(p), "\n")
	lw.logger.Error("Data proxy error", "error", withoutNewline)
	return len(p), nil
}

// NewDataSourceProxy creates a new Datasource proxy
func NewDataSourceProxy(ds *models.DataSource, plugin *plugins.DataSourcePlugin, ctx *models.ReqContext,
	proxyPath string, cfg *setting.Cfg) (*DataSourceProxy, error) {
	targetURL, err := datasource.ValidateURL(ds.Type, ds.Url)
	if err != nil {
		return nil, err
	}

	return &DataSourceProxy{
		ds:        ds,
		plugin:    plugin,
		ctx:       ctx,
		proxyPath: proxyPath,
		targetUrl: targetURL,
		cfg:       cfg,
	}, nil
}

func newHTTPClient() httpClient {
	return &http.Client{
		Timeout:   30 * time.Second,
		Transport: &http.Transport{Proxy: http.ProxyFromEnvironment},
	}
}

func (proxy *DataSourceProxy) HandleRequest() {
	if err := proxy.validateRequest(); err != nil {
		proxy.ctx.JsonApiErr(403, err.Error(), nil)
		return
	}

	proxyErrorLogger := logger.New("userId", proxy.ctx.UserId, "orgId", proxy.ctx.OrgId, "uname", proxy.ctx.Login, "path", proxy.ctx.Req.URL.Path, "remote_addr", proxy.ctx.RemoteAddr(), "referer", proxy.ctx.Req.Referer())

	reverseProxy := &httputil.ReverseProxy{
		Director:      proxy.getDirector(),
		FlushInterval: time.Millisecond * 200,
		ErrorLog:      log.New(&logWrapper{logger: proxyErrorLogger}, "", 0),
	}

	transport, err := proxy.ds.GetHttpTransport()
	if err != nil {
		proxy.ctx.JsonApiErr(400, "Unable to load TLS certificate", err)
		return
	}

	reverseProxy.Transport = &handleResponseTransport{
		transport: transport,
	}

	proxy.logRequest()

	span, ctx := opentracing.StartSpanFromContext(proxy.ctx.Req.Context(), "datasource reverse proxy")
	proxy.ctx.Req.Request = proxy.ctx.Req.WithContext(ctx)

	defer span.Finish()
	span.SetTag("datasource_id", proxy.ds.Id)
	span.SetTag("datasource_type", proxy.ds.Type)
	span.SetTag("user_id", proxy.ctx.SignedInUser.UserId)
	span.SetTag("org_id", proxy.ctx.SignedInUser.OrgId)

	proxy.addTraceFromHeaderValue(span, "X-Panel-Id", "panel_id")
	proxy.addTraceFromHeaderValue(span, "X-Dashboard-Id", "dashboard_id")

	if err := opentracing.GlobalTracer().Inject(
		span.Context(),
		opentracing.HTTPHeaders,
		opentracing.HTTPHeadersCarrier(proxy.ctx.Req.Request.Header)); err != nil {
		logger.Error("Failed to inject span context instance", "err", err)
	}

	reverseProxy.ServeHTTP(proxy.ctx.Resp, proxy.ctx.Req.Request)
}

func (proxy *DataSourceProxy) addTraceFromHeaderValue(span opentracing.Span, headerName string, tagName string) {
	panelId := proxy.ctx.Req.Header.Get(headerName)
	dashId, err := strconv.Atoi(panelId)
	if err == nil {
		span.SetTag(tagName, dashId)
	}
}

func (proxy *DataSourceProxy) getDirector() func(req *http.Request) {
	return func(req *http.Request) {
		req.URL.Scheme = proxy.targetUrl.Scheme
		req.URL.Host = proxy.targetUrl.Host
		req.Host = proxy.targetUrl.Host

		reqQueryVals := req.URL.Query()

		switch proxy.ds.Type {
		case models.DS_INFLUXDB_08:
			req.URL.Path = util.JoinURLFragments(proxy.targetUrl.Path, "db/"+proxy.ds.Database+"/"+proxy.proxyPath)
			reqQueryVals.Add("u", proxy.ds.User)
			reqQueryVals.Add("p", proxy.ds.DecryptedPassword())
			req.URL.RawQuery = reqQueryVals.Encode()
		case models.DS_INFLUXDB:
			req.URL.Path = util.JoinURLFragments(proxy.targetUrl.Path, proxy.proxyPath)
			req.URL.RawQuery = reqQueryVals.Encode()
			if !proxy.ds.BasicAuth {
				req.Header.Del("Authorization")
				req.Header.Add("Authorization", util.GetBasicAuthHeader(proxy.ds.User, proxy.ds.DecryptedPassword()))
			}
		default:
			req.URL.Path = util.JoinURLFragments(proxy.targetUrl.Path, proxy.proxyPath)
		}

		if proxy.ds.BasicAuth {
			req.Header.Del("Authorization")
			req.Header.Add("Authorization", util.GetBasicAuthHeader(proxy.ds.BasicAuthUser, proxy.ds.DecryptedBasicAuthPassword()))
		}

		dsAuth := req.Header.Get("X-DS-Authorization")
		if len(dsAuth) > 0 {
			req.Header.Del("X-DS-Authorization")
			req.Header.Del("Authorization")
			req.Header.Add("Authorization", dsAuth)
		}

		applyUserHeader(proxy.cfg.SendUserHeader, req, proxy.ctx.SignedInUser)

		keepCookieNames := []string{}
		if proxy.ds.JsonData != nil {
			if keepCookies := proxy.ds.JsonData.Get("keepCookies"); keepCookies != nil {
				keepCookieNames = keepCookies.MustStringArray()
			}
		}

		proxyutil.ClearCookieHeader(req, keepCookieNames)
		proxyutil.PrepareProxyRequest(req)

		req.Header.Set("User-Agent", fmt.Sprintf("Grafana/%s", setting.BuildVersion))

		// Clear Origin and Referer to avoir CORS issues
		req.Header.Del("Origin")
		req.Header.Del("Referer")

		if proxy.route != nil {
			ApplyRoute(proxy.ctx.Req.Context(), req, proxy.proxyPath, proxy.route, proxy.ds)
		}

		if proxy.ds.JsonData != nil && proxy.ds.JsonData.Get("oauthPassThru").MustBool() {
			addOAuthPassThruAuth(proxy.ctx, req)
		}
	}
}

func (proxy *DataSourceProxy) validateRequest() error {
	if !checkWhiteList(proxy.ctx, proxy.targetUrl.Host) {
		return errors.New("Target url is not a valid target")
	}

	if proxy.ds.Type == models.DS_PROMETHEUS {
		if proxy.ctx.Req.Request.Method == "DELETE" {
			return errors.New("Deletes not allowed on proxied Prometheus datasource")
		}
		if proxy.ctx.Req.Request.Method == "PUT" {
			return errors.New("Puts not allowed on proxied Prometheus datasource")
		}
		if proxy.ctx.Req.Request.Method == "POST" && !(proxy.proxyPath == "api/v1/query" || proxy.proxyPath == "api/v1/query_range") {
			return errors.New("Posts not allowed on proxied Prometheus datasource except on /query and /query_range")
		}
	}

	if proxy.ds.Type == models.DS_ES {
		if proxy.ctx.Req.Request.Method == "DELETE" {
			return errors.New("Deletes not allowed on proxied Elasticsearch datasource")
		}
		if proxy.ctx.Req.Request.Method == "PUT" {
			return errors.New("Puts not allowed on proxied Elasticsearch datasource")
		}
		if proxy.ctx.Req.Request.Method == "POST" && proxy.proxyPath != "_msearch" {
			return errors.New("Posts not allowed on proxied Elasticsearch datasource except on /_msearch")
		}
	}

	// found route if there are any
	if len(proxy.plugin.Routes) > 0 {
		for _, route := range proxy.plugin.Routes {
			// method match
			if route.Method != "" && route.Method != "*" && route.Method != proxy.ctx.Req.Method {
				continue
			}

			if route.ReqRole.IsValid() {
				if !proxy.ctx.HasUserRole(route.ReqRole) {
					return errors.New("Plugin proxy route access denied")
				}
			}

			if strings.HasPrefix(proxy.proxyPath, route.Path) {
				proxy.route = route
				break
			}
		}
	}

	return nil
}

func (proxy *DataSourceProxy) logRequest() {
	if !setting.DataProxyLogging {
		return
	}

	var body string
	if proxy.ctx.Req.Request.Body != nil {
		buffer, err := ioutil.ReadAll(proxy.ctx.Req.Request.Body)
		if err == nil {
			proxy.ctx.Req.Request.Body = ioutil.NopCloser(bytes.NewBuffer(buffer))
			body = string(buffer)
		}
	}

	logger.Info("Proxying incoming request",
		"userid", proxy.ctx.UserId,
		"orgid", proxy.ctx.OrgId,
		"username", proxy.ctx.Login,
		"datasource", proxy.ds.Type,
		"uri", proxy.ctx.Req.RequestURI,
		"method", proxy.ctx.Req.Request.Method,
		"body", body)
}

func checkWhiteList(c *models.ReqContext, host string) bool {
	if host != "" && len(setting.DataProxyWhiteList) > 0 {
		if _, exists := setting.DataProxyWhiteList[host]; !exists {
			c.JsonApiErr(403, "Data proxy hostname and ip are not included in whitelist", nil)
			return false
		}
	}

	return true
}

func addOAuthPassThruAuth(c *models.ReqContext, req *http.Request) {
	authInfoQuery := &models.GetAuthInfoQuery{UserId: c.UserId}
	if err := bus.Dispatch(authInfoQuery); err != nil {
		logger.Error("Error fetching oauth information for user", "userid", c.UserId, "username", c.Login, "error", err)
		return
	}

	authProvider := authInfoQuery.Result.AuthModule
	connect, err := social.GetConnector(authProvider)
	if err != nil {
		logger.Error("Failed to get OAuth connector", "error", err)
		return
	}

	persistedToken := &oauth2.Token{
		AccessToken:  authInfoQuery.Result.OAuthAccessToken,
		Expiry:       authInfoQuery.Result.OAuthExpiry,
		RefreshToken: authInfoQuery.Result.OAuthRefreshToken,
		TokenType:    authInfoQuery.Result.OAuthTokenType,
	}

	client, err := social.GetOAuthHttpClient(authProvider)
	if err != nil {
		logger.Error("Failed to create OAuth http client", "error", err)
		return
	}
	oauthctx := context.WithValue(c.Req.Context(), oauth2.HTTPClient, client)

	// TokenSource handles refreshing the token if it has expired
	token, err := connect.TokenSource(oauthctx, persistedToken).Token()
	if err != nil {
		logger.Error("Failed to retrieve access token from OAuth provider", "provider", authInfoQuery.Result.AuthModule, "userid", c.UserId, "username", c.Login, "error", err)
		return
	}

	// If the tokens are not the same, update the entry in the DB
	if !tokensEq(persistedToken, token) {
		updateAuthCommand := &models.UpdateAuthInfoCommand{
			UserId:     authInfoQuery.Result.UserId,
			AuthModule: authInfoQuery.Result.AuthModule,
			AuthId:     authInfoQuery.Result.AuthId,
			OAuthToken: token,
		}
		if err := bus.Dispatch(updateAuthCommand); err != nil {
			logger.Error("Failed to update auth info during token refresh", "userid", c.UserId, "username", c.Login, "error", err)
			return
		}
		logger.Debug("Updated OAuth info while proxying an OAuth pass-thru request", "userid", c.UserId, "username", c.Login)
	}
	req.Header.Del("Authorization")
	req.Header.Add("Authorization", fmt.Sprintf("%s %s", token.Type(), token.AccessToken))
}

// tokensEq checks for OAuth2 token equivalence given the fields of the struct Grafana is interested in
func tokensEq(t1, t2 *oauth2.Token) bool {
	return t1.AccessToken == t2.AccessToken &&
		t1.RefreshToken == t2.RefreshToken &&
		t1.Expiry == t2.Expiry &&
		t1.TokenType == t2.TokenType
}
