package confext import ( "errors" "fmt" "gogs.mikescher.com/BlackForestBytes/goext/timeext" "math/bits" "os" "reflect" "strconv" "time" ) // ApplyEnvOverrides overrides field values from environment variables // // fields must be tagged with `env:"env_key"` // // only works on exported fields // // fields without an env tag are ignored // fields with an `env:"-"` tag are ignore // // sub-structs are recursively parsed (if they have an env tag) and the env-variable keys are delimited by the delim parameter // sub-structs with `env:""` are also parsed, but the delimited is skipped (they are handled as if they were one level higher) func ApplyEnvOverrides[T any](prefix string, c *T, delim string) error { rval := reflect.ValueOf(c).Elem() return processEnvOverrides(rval, delim, prefix) } func processEnvOverrides(rval reflect.Value, delim string, prefix string) error { rtyp := rval.Type() for i := 0; i < rtyp.NumField(); i++ { rsfield := rtyp.Field(i) rvfield := rval.Field(i) if !rsfield.IsExported() { continue } if rvfield.Kind() == reflect.Struct { envkey, found := rsfield.Tag.Lookup("env") if !found || envkey == "-" { continue } subPrefix := prefix if envkey != "" { subPrefix = subPrefix + envkey + delim } err := processEnvOverrides(rvfield, delim, subPrefix) if err != nil { return err } } envkey := rsfield.Tag.Get("env") if envkey == "" || envkey == "-" { continue } fullEnvKey := prefix + envkey envval, efound := os.LookupEnv(fullEnvKey) if !efound { continue } if rvfield.Type().Kind() == reflect.Pointer { newval, err := parseEnvToValue(envval, fullEnvKey, rvfield.Type().Elem()) if err != nil { return err } // converts reflect.Value to pointer ptrval := reflect.New(rvfield.Type().Elem()) ptrval.Elem().Set(newval) rvfield.Set(ptrval) fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval) } else { newval, err := parseEnvToValue(envval, fullEnvKey, rvfield.Type()) if err != nil { return err } rvfield.Set(newval) fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval) } } return nil } func parseEnvToValue(envval string, fullEnvKey string, rvtype reflect.Type) (reflect.Value, error) { if rvtype == reflect.TypeOf("") { return reflect.ValueOf(envval), nil } else if rvtype == reflect.TypeOf(int(0)) { envint, err := strconv.ParseInt(envval, 10, bits.UintSize) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(int(envint)), nil } else if rvtype == reflect.TypeOf(int64(0)) { envint, err := strconv.ParseInt(envval, 10, 64) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int64 (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(int64(envint)), nil } else if rvtype == reflect.TypeOf(int32(0)) { envint, err := strconv.ParseInt(envval, 10, 32) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(int32(envint)), nil } else if rvtype == reflect.TypeOf(int8(0)) { envint, err := strconv.ParseInt(envval, 10, 8) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(int8(envint)), nil } else if rvtype == reflect.TypeOf(time.Duration(0)) { dur, err := timeext.ParseDurationShortString(envval) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to duration (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(dur), nil } else if rvtype == reflect.TypeOf(time.UnixMilli(0)) { tim, err := time.Parse(time.RFC3339Nano, envval) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to time.time (value := '%s')", fullEnvKey, envval)) } return reflect.ValueOf(tim), nil } else if rvtype.ConvertibleTo(reflect.TypeOf(int(0))) { envint, err := strconv.ParseInt(envval, 10, 8) if err != nil { return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to <%s, ,int> (value := '%s')", rvtype.Name(), fullEnvKey, envval)) } envcvl := reflect.ValueOf(envint).Convert(rvtype) return envcvl, nil } else if rvtype.ConvertibleTo(reflect.TypeOf("")) { envcvl := reflect.ValueOf(envval).Convert(rvtype) return envcvl, nil } else { return reflect.Value{}, errors.New(fmt.Sprintf("Unknown kind/type in config: [ %s | %s ]", rvtype.Kind().String(), rvtype.String())) } }