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env.go
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env.go
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package gonfig
import (
"errors"
"os"
"strings"
"github.com/joho/godotenv"
)
// EnvProvider loads values from environment variables to provided struct
type EnvProvider struct {
// Prefix is used when finding values from environment variables, defaults to ""
EnvPrefix string
// SnakeCase specifies whether to convert field names to snake_case or not, defaults to true
SnakeCase bool
// UpperCase specifies whether to convert field names to UPPERCASE or not, defaults to true
UpperCase bool
// FieldSeparator is used to separate field names, defaults to "_"
FieldSeparator string
// Source is used to retrieve environment variables
// It can be either a path to a file or empty string, if empty OS will be used
Source string
// Whether to report error if env file is not found, defaults to false
Required bool
}
// NewEnvProvider creates a new EnvProvider
func NewEnvProvider() *EnvProvider {
return &EnvProvider{
EnvPrefix: "",
SnakeCase: true,
UpperCase: true,
FieldSeparator: "_",
Source: "",
Required: false,
}
}
// NewEnvFileProvider creates a new EnvProvider from .env file
func NewEnvFileProvider(path string) *EnvProvider {
return &EnvProvider{
EnvPrefix: "",
SnakeCase: true,
UpperCase: true,
FieldSeparator: "_",
Source: path,
Required: false,
}
}
// Name of provider
func (ep *EnvProvider) Name() string {
return "ENV provider"
}
// Fill takes struct fields and fills their values
func (ep *EnvProvider) Fill(in *Input) error {
content, err := ep.envMap()
if err != nil {
return err
}
for _, f := range in.Fields {
value, err := ep.provide(content, f.Tags.Config, f.Path)
if err != nil {
if errors.Is(err, ErrKeyNotFound) {
continue
}
return err
}
err = in.setValue(f, value)
if err != nil {
return err
}
f.IsSet = true
}
return nil
}
// envMap returns environment variables map from either OS or file specified by source
// Defaults to operating system env variables
func (ep *EnvProvider) envMap() (map[string]string, error) {
envs := envFromOS()
var fileEnvs map[string]string
var err error
if ep.Source != "" {
fileEnvs, err = envFromFile(ep.Source)
}
if err != nil {
notExistsErr := errors.Is(err, os.ErrNotExist)
if (notExistsErr && ep.Required) || !notExistsErr {
return nil, err
}
}
if len(envs) == 0 {
if len(fileEnvs) == 0 {
return nil, nil
}
envs = make(map[string]string)
}
for k, v := range fileEnvs {
_, exists := envs[k]
if !exists {
envs[k] = v
}
}
return envs, nil
}
// returns environment variables map retrieved from operating system
func envFromOS() map[string]string {
envs := os.Environ()
if len(envs) == 0 {
return nil
}
envMap := make(map[string]string)
for _, env := range envs {
keyValue := strings.SplitN(env, "=", 2)
if len(keyValue) < 2 {
continue
}
envMap[keyValue[0]] = keyValue[1]
}
return envMap
}
// returns environment variables map retrieved from specified file
func envFromFile(path string) (map[string]string, error) {
m, err := godotenv.Read(path)
if err != nil {
return nil, err
}
return m, nil
}
// provide find a value from env variables based on specified key and path
func (ep *EnvProvider) provide(content map[string]string, key string, path []string) (string, error) {
k := ep.buildKey(key, path)
value, exists := content[k]
if !exists {
return "", ErrKeyNotFound
}
return value, nil
}
// buildKey prefix key with EnvPrefix, if not provided, path slice will be used
func (ep *EnvProvider) buildKey(key string, path []string) string {
if key != "" {
return ep.EnvPrefix + key
}
k := strings.Join(path, ep.FieldSeparator)
if ep.SnakeCase {
k = toSnakeCase(k)
}
if ep.UpperCase {
k = strings.ToUpper(k)
}
k = ep.EnvPrefix + k
return k
}