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// Copyright 2023 Google LLC
//
// 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 app
import (
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"time"
"github.com/google/cel-go/repl"
)
type service struct {
commandCountLimit int
}
type evaluateRequest struct {
Commands []string
}
type commandResponse struct {
ReplOutput string `json:"replOutput"`
Issue string `json:"issue"`
Evaluated bool `json:"evaluated"`
}
type evaluateResponse struct {
Responses []commandResponse `json:"responses"`
EvalTime time.Duration `json:"evalTime"`
}
func unmarshalEvaluationRequest(data []byte) (*evaluateRequest, error) {
r := evaluateRequest{}
err := json.Unmarshal(data, &r)
return &r, err
}
func marshalEvaluationResponse(r *evaluateResponse) ([]byte, error) {
v, err := json.Marshal(r)
return v, err
}
func (s *service) evaluate(req *evaluateRequest) (*evaluateResponse, error) {
evaluator, err := repl.NewEvaluator()
if err != nil {
return nil, errors.New("error initilializing evaluator")
}
if s.commandCountLimit > 0 && len(req.Commands) > s.commandCountLimit {
return nil, fmt.Errorf("number of commands (%d) exceeded limit (%d)", len(req.Commands), s.commandCountLimit)
}
start := time.Now()
resp := evaluateResponse{}
for _, replCmd := range req.Commands {
cmd, err := repl.Parse(replCmd)
if err != nil {
resp.Responses = append(resp.Responses, commandResponse{
ReplOutput: "",
Issue: err.Error(),
})
continue
}
val, _, err := evaluator.Process(cmd)
iss := ""
if err != nil {
iss = err.Error()
}
resp.Responses = append(resp.Responses,
commandResponse{
ReplOutput: val,
Issue: iss,
Evaluated: true,
})
}
elapsed := time.Now().Sub(start)
resp.EvalTime = elapsed
return &resp, nil
}
func (s *service) evaluateJSON(data []byte) ([]byte, error) {
req, err := unmarshalEvaluationRequest(data)
if err != nil {
return nil, err
}
resp, err := s.evaluate(req)
if err != nil {
return nil, err
}
return marshalEvaluationResponse(resp)
}
func writeErr(w http.ResponseWriter, err error) {
w.WriteHeader(http.StatusBadRequest)
w.Header().Set("Content-Type", "text/plain")
w.Write([]byte(err.Error()))
}
// NewJSONHandler provides an http.HandlerFunc that implements the JSON API
// for the CEL REPL.
//
// The service is stateless -- every request creates a new repl instance and
// applies the list of commands in order.
func NewJSONHandler() http.HandlerFunc {
s := &service{
commandCountLimit: 50,
}
return func(w http.ResponseWriter, r *http.Request) {
data, err := io.ReadAll(r.Body)
if err != nil {
writeErr(w, err)
return
}
resp, err := s.evaluateJSON(data)
if err != nil {
writeErr(w, err)
}
w.WriteHeader(http.StatusOK)
w.Header().Set("Content-Type", "application/json")
w.Write(resp)
}
}
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