// Execute the statement(s) in the given request and returns a response.
// On error, the returned integer is an HTTP error code.
func (e *Executor) Execute(args driver.Request) (driver.Response, int, error) {
	defer func(start time.Time) {
		e.latency.RecordValue(time.Now().Sub(start).Nanoseconds())
	}(time.Now())
	var session Session
	if err := proto.Unmarshal(args.Session, &session); err != nil {
		return driver.Response{}, http.StatusBadRequest, err
	}
	return e.ExecuteStatements(args.GetUser(), session, args.Sql, args.Params)
}

// Execute the statement(s) in the given request and return a response.
// On error, the returned integer is an HTTP error code.
func (e *Executor) Execute(args driver.Request) (driver.Response, int, error) {
	planMaker := plannerPool.Get().(*planner)
	defer plannerPool.Put(planMaker)

	*planMaker = planner{
		user: args.GetUser(),
		evalCtx: parser.EvalContext{
			NodeID:  e.nodeID,
			ReCache: e.reCache,
			// Copy existing GetLocation closure. See plannerPool.New() for the
			// initial setting.
			GetLocation: planMaker.evalCtx.GetLocation,
		},
		leaseMgr:     e.leaseMgr,
		systemConfig: e.getSystemConfig(),
	}

	// Pick up current session state.
	if err := proto.Unmarshal(args.Session, &planMaker.session); err != nil {
		return args.CreateReply(), http.StatusBadRequest, err
	}
	// Resume a pending transaction if present.
	if planMaker.session.Txn != nil {
		txn := client.NewTxn(e.db)
		txn.Proto = planMaker.session.Txn.Txn
		if planMaker.session.MutatesSystemDB {
			txn.SetSystemDBTrigger()
		}
		planMaker.setTxn(txn, planMaker.session.Txn.Timestamp.GoTime())
	}

	// Send the Request for SQL execution and set the application-level error
	// for each result in the reply.
	planMaker.params = parameters(args.Params)
	reply := e.execStmts(args.Sql, planMaker)

	// Send back the session state even if there were application-level errors.
	// Add transaction to session state.
	if planMaker.txn != nil {
		// TODO(pmattis): Need to record the leases used by a transaction within
		// the transaction state and restore it when the transaction is restored.
		planMaker.releaseLeases(e.db)
		planMaker.session.Txn = &Session_Transaction{Txn: planMaker.txn.Proto, Timestamp: driver.Timestamp(planMaker.evalCtx.TxnTimestamp.Time)}
		planMaker.session.MutatesSystemDB = planMaker.txn.SystemDBTrigger()
	} else {
		planMaker.session.Txn = nil
		planMaker.session.MutatesSystemDB = false
	}
	bytes, err := proto.Marshal(&planMaker.session)
	if err != nil {
		return args.CreateReply(), http.StatusInternalServerError, err
	}
	reply.Session = bytes

	return reply, 0, nil
}

// Execute the statement(s) in the given request and return a response.
// On error, the returned integer is an HTTP error code.
func (e *Executor) Execute(args driver.Request) (driver.Response, int, error) {
	planMaker := &planner{
		user: args.GetUser(),
		evalCtx: parser.EvalContext{
			NodeID:  e.nodeID,
			ReCache: e.reCache,
		},
		leaseMgr:     e.leaseMgr,
		systemConfig: e.getSystemConfig(),
	}

	// Pick up current session state.
	if err := proto.Unmarshal(args.Session, &planMaker.session); err != nil {
		return args.CreateReply(), http.StatusBadRequest, err
	}
	// Resume a pending transaction if present.
	if planMaker.session.Txn != nil {
		txn := client.NewTxn(e.db)
		txn.Proto = planMaker.session.Txn.Txn
		if planMaker.session.MutatesSystemDB {
			txn.SetSystemDBTrigger()
		}
		planMaker.setTxn(txn, planMaker.session.Txn.Timestamp.GoTime())
	}
	planMaker.evalCtx.GetLocation = planMaker.session.getLocation

	// Send the Request for SQL execution and set the application-level error
	// for each result in the reply.
	reply := e.execStmts(args.Sql, parameters(args.Params), planMaker)

	// Send back the session state even if there were application-level errors.
	// Add transaction to session state.
	if planMaker.txn != nil {
		planMaker.session.Txn = &Session_Transaction{Txn: planMaker.txn.Proto, Timestamp: driver.Timestamp(planMaker.evalCtx.TxnTimestamp.Time)}
		planMaker.session.MutatesSystemDB = planMaker.txn.SystemDBTrigger()
	} else {
		planMaker.session.Txn = nil
		planMaker.session.MutatesSystemDB = false
	}
	bytes, err := proto.Marshal(&planMaker.session)
	if err != nil {
		return args.CreateReply(), http.StatusInternalServerError, err
	}
	reply.Session = bytes

	return reply, 0, nil
}

func (s server) execute(args driver.Request) (driver.Response, int, error) {
	// Pick up current session state.
	planMaker := planner{user: args.GetUser()}
	if err := gogoproto.Unmarshal(args.Session, &planMaker.session); err != nil {
		return args.CreateReply(), http.StatusBadRequest, err
	}
	// Open a pending transaction if needed.
	if planMaker.session.Txn != nil {
		txn := client.NewTxn(s.db)
		txn.Proto = *planMaker.session.Txn
		if planMaker.session.MutatesSystemDB {
			txn.SetSystemDBTrigger()
		}
		planMaker.txn = txn
	}

	// Send the Request for SQL execution and set the application-level error
	// for each result in the reply.
	reply := s.execStmts(args.Sql, args.GetParameters(), &planMaker)

	// Send back the session state even if there were application-level errors.
	// Add transaction to session state.
	if planMaker.txn != nil {
		planMaker.session.Txn = &planMaker.txn.Proto
		planMaker.session.MutatesSystemDB = planMaker.txn.SystemDBTrigger()
	} else {
		planMaker.session.Txn = nil
		planMaker.session.MutatesSystemDB = false
	}
	bytes, err := gogoproto.Marshal(&planMaker.session)
	if err != nil {
		return args.CreateReply(), http.StatusInternalServerError, err
	}
	reply.Session = bytes

	return reply, 0, nil
}

// ServeHTTP serves the SQL API by treating the request URL path
// as the method, the request body as the arguments, and sets the
// response body as the method reply. The request body is unmarshalled
// into arguments based on the Content-Type request header. Protobuf
// and JSON-encoded requests are supported. The response body is
// encoded according to the request's Accept header, or if not
// present, in the same format as the request's incoming Content-Type
// header.
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	method := r.URL.Path
	if !strings.HasPrefix(method, driver.Endpoint) {
		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
		return
	}

	// Check TLS settings.
	authenticationHook, err := security.AuthenticationHook(s.context.Insecure, r.TLS)
	if err != nil {
		http.Error(w, err.Error(), http.StatusUnauthorized)
		return
	}

	method = strings.TrimPrefix(method, driver.Endpoint)
	if method != driver.Execute.String() {
		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
		return
	}

	// Unmarshal the request.
	reqBody, err := ioutil.ReadAll(r.Body)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	var args driver.Request
	if err := util.UnmarshalRequest(r, reqBody, &args, allowedEncodings); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	// Check request user against client certificate user.
	if err := authenticationHook(&args, true /*public*/); err != nil {
		http.Error(w, err.Error(), http.StatusUnauthorized)
		return
	}

	// Pick up current session state.
	planMaker := planner{user: args.GetUser()}
	if err := gogoproto.Unmarshal(args.Session, &planMaker.session); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	// Open a pending transaction if needed.
	if planMaker.session.Txn != nil {
		txn := client.NewTxn(*s.db)
		txn.Proto = *planMaker.session.Txn
		planMaker.txn = txn
	}

	// Send the Request for SQL execution and set the application-level error
	// for each result in the reply.
	reply := s.exec(args, &planMaker)

	// Send back the session state even if there were application-level errors.
	// Add transaction to session state.
	if planMaker.txn != nil {
		planMaker.session.Txn = &planMaker.txn.Proto
	} else {
		planMaker.session.Txn = nil
	}
	bytes, err := gogoproto.Marshal(&planMaker.session)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	reply.Session = bytes

	// Marshal the response.
	body, contentType, err := util.MarshalResponse(r, &reply, allowedEncodings)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set(util.ContentTypeHeader, contentType)
	w.Write(body)
}

// exec executes the request. Any error encountered is returned; it is
// the caller's responsibility to update the response.
func (s *Server) exec(req driver.Request) (driver.Response, error) {
	var resp driver.Response

	// Pick up current session state.
	// The request user is validated in ServeHTTP. Even in insecure mode,
	// it is guaranteed not to be empty.
	planner := planner{user: req.GetUser()}
	if req.Session != nil {
		// TODO(tschottdorf) will have to validate the Session information (for
		// instance, whether access to the stored database is permitted).
		if err := gogoproto.Unmarshal(req.Session, &planner.session); err != nil {
			return resp, err
		}
	}
	stmts, err := parser.Parse(req.Sql)
	if err != nil {
		return resp, err
	}
	for _, stmt := range stmts {
		// Bind all the placeholder variables in the stmt to actual values.
		if err := parser.FillArgs(stmt, parameters(req.Params)); err != nil {
			return resp, err
		}
		var plan planNode
		if err := s.db.Txn(func(txn *client.Txn) error {
			planner.txn = txn
			plan, err = planner.makePlan(stmt)
			planner.txn = nil
			return err
		}); err != nil {
			return resp, err
		}

		result := driver.Result{
			Columns: plan.Columns(),
		}
		for plan.Next() {
			values := plan.Values()
			row := driver.Result_Row{}
			row.Values = make([]driver.Datum, 0, len(values))
			for _, val := range values {
				if val == parser.DNull {
					row.Values = append(row.Values, driver.Datum{})
				} else {
					switch vt := val.(type) {
					case parser.DBool:
						row.Values = append(row.Values, driver.Datum{BoolVal: (*bool)(&vt)})
					case parser.DInt:
						row.Values = append(row.Values, driver.Datum{IntVal: (*int64)(&vt)})
					case parser.DFloat:
						row.Values = append(row.Values, driver.Datum{FloatVal: (*float64)(&vt)})
					case parser.DString:
						row.Values = append(row.Values, driver.Datum{StringVal: (*string)(&vt)})
					default:
						return resp, util.Errorf("unsupported datum: %T", val)
					}
				}
			}
			result.Rows = append(result.Rows, row)
		}
		if err := plan.Err(); err != nil {
			return resp, err
		}

		resp.Results = append(resp.Results, result)
	}

	// Update session state.
	resp.Session, err = gogoproto.Marshal(&planner.session)
	return resp, err
}