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config.go
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config.go
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package service
import (
"encoding/json"
"errors"
"fmt"
"net/http"
"os"
"reflect"
"strconv"
"strings"
"time"
)
const (
defaultPort int = 8080
defaultRateLimit int = 1000
defaultRatio float64 = 1.0
)
// config is the service configuration
type config struct {
port int // server listening port
apiKey string // api key
apiToken string // api token
methods, subRoutes []string // supported sub-routes
respDelay time.Duration // response delay in milliseconds
failureCode int // response code for failed requests
failureRespBody map[string]interface{} // response body for failed requests
successCode int // response code for successful requests
successRespBody map[string]interface{} // response body for successful requests
successRatio float64 // ratio of successful requests
rateLimit int // rate limit (requests per second)
rateExceededRespBody map[string]interface{} // response body for rate exceeded requests
}
// loadConfigFromEnv loads the configuration from the environment.
//
//nolint:cyclop // many env variables to parse
func loadConfigFromEnv() (*config, error) {
var err error
cfg := config{
apiKey: os.Getenv("API_KEY"),
apiToken: os.Getenv("API_TOKEN"),
}
if cfg.apiKey != "" && cfg.apiToken != "" {
return nil, errors.New("only one of API_KEY or API_TOKEN can be set")
}
portENV := os.Getenv("PORT")
if portENV != "" {
cfg.port, err = strconv.Atoi(portENV)
if err != nil {
return nil, fmt.Errorf("invalid int format for PORT: %w", err)
}
} else {
cfg.port = defaultPort
}
respDelayENV := os.Getenv("RESP_DELAY")
if respDelayENV != "" {
respDelayINT, err := strconv.Atoi(respDelayENV)
if err != nil {
return nil, fmt.Errorf("invalid int format for RESP_DELAY: %w", err)
}
cfg.respDelay = time.Duration(respDelayINT) * time.Millisecond
if cfg.respDelay > 30*time.Second {
return nil, fmt.Errorf("RESP_DELAY cannot be greater than 30 seconds")
}
}
failureCodeEnv := os.Getenv("FAILURE_RESP_CODE")
if failureCodeEnv != "" {
cfg.failureCode, err = strconv.Atoi(failureCodeEnv)
if err != nil {
return nil, fmt.Errorf("invalid int format for FAILURE_RESP_CODE: %w", err)
}
} else {
cfg.failureCode = http.StatusBadRequest // default response code
}
failureRespBodyEnv := os.Getenv("FAILURE_RESP_BODY")
if failureRespBodyEnv != "" {
if err = json.Unmarshal([]byte(failureRespBodyEnv), &cfg.failureRespBody); err != nil {
return nil, fmt.Errorf("invalid json format for FAILURE_RESP_BODY: %w", err)
}
}
successCodeEnv := os.Getenv("SUCCESS_RESP_CODE")
if successCodeEnv != "" {
cfg.successCode, err = strconv.Atoi(successCodeEnv)
if err != nil {
return nil, fmt.Errorf("invalid int format for SUCCESS_RESP_CODE: %w", err)
}
} else {
cfg.successCode = http.StatusOK // default response code
}
successRepBodyEnv := os.Getenv("SUCCESS_RESP_BODY")
if successRepBodyEnv != "" {
if err = json.Unmarshal([]byte(successRepBodyEnv), &cfg.successRespBody); err != nil {
return nil, fmt.Errorf("invalid json format for SUCCESS_RESP_BODY: %w", err)
}
} else {
cfg.successRespBody = map[string]interface{}{"success": true} // default response body
}
successRatioEnv := os.Getenv("SUCCESS_RATIO")
if successRatioEnv != "" {
cfg.successRatio, err = strconv.ParseFloat(successRatioEnv, 64)
if err != nil || cfg.successRatio <= 0 || cfg.successRatio > 1 {
return nil, fmt.Errorf("invalid value for SUCCESS_RATIO")
}
} else {
cfg.successRatio = defaultRatio
}
rateLimitEnv := os.Getenv("RATE_LIMIT")
if rateLimitEnv != "" {
cfg.rateLimit, err = strconv.Atoi(rateLimitEnv)
if err != nil {
return nil, fmt.Errorf("invalid int format for RATE_LIMIT")
}
} else {
cfg.rateLimit = defaultRateLimit
}
rateExceededRespBodyEnv := os.Getenv("RATE_EXCEEDED_RESP_BODY")
if rateExceededRespBodyEnv != "" {
if err = json.Unmarshal([]byte(rateExceededRespBodyEnv), &cfg.rateExceededRespBody); err != nil {
return nil, fmt.Errorf("invalid json format for RATE_EXCEEDED_RESP_BODY: %w", err)
}
}
methodsEnv := os.Getenv("METHODS")
if methodsEnv != "" {
allowedMethods := []string{http.MethodGet, http.MethodPost, http.MethodPut, http.MethodDelete, http.MethodPatch}
cfg.methods = strings.Split(methodsEnv, ",")
for _, method := range cfg.methods {
if !stringSliceContains(allowedMethods, method) {
return nil, fmt.Errorf("method %s is not allowed", method)
}
}
}
subRoutesEnv := os.Getenv("SUB_ROUTES")
if subRoutesEnv != "" {
cfg.subRoutes = strings.Split(subRoutesEnv, ",")
}
return &cfg, nil
}
// stringSliceContains is a helper function to detect whether a string slice contains a string or not
func stringSliceContains(s []string, e string) bool {
for _, a := range s {
if a == e {
return true
}
}
return false
}
// structToMapStringInterface transforms a struct of the given type into a map[string]interface{}
func structToMapStringInterface(s interface{}) (map[string]interface{}, error) {
if reflect.TypeOf(s).Kind() != reflect.Struct {
return nil, fmt.Errorf("s must be a struct")
}
buf, err := json.Marshal(s)
if err != nil {
return nil, err
}
var mapVal map[string]interface{}
if err = json.Unmarshal(buf, &mapVal); err != nil {
return nil, err
}
return mapVal, nil
}