use reflection to set config values from environment

accounts/pkg/command/root.go

@@ -68,7 +68,12 @@ func NewLogger(cfg *config.Config) log.Logger {
 
 // ParseConfig loads accounts configuration from known paths.
 func ParseConfig(c *cli.Context, cfg *config.Config) error {
-	return ociscfg.BindSourcesToStructs("accounts", cfg)
+	_, err := ociscfg.BindSourcesToStructs("accounts", cfg)
+	if err != nil {
+		return err
+	}
+
+	return nil
 }
 
 // SutureService allows for the accounts command to be embedded and supervised by a suture supervisor tree.

ocis-pkg/config/helpers.go

@@ -65,7 +65,7 @@ func sanitizeExtensions(set []string, ext []string, f func(a, b string) bool) []
 
 // BindSourcesToStructs assigns any config value from a config file / env variable to struct `dst`. Its only purpose
 // is to solely modify `dst`, not dealing with the config structs; and do so in a thread safe manner.
-func BindSourcesToStructs(extension string, dst interface{}) error {
+func BindSourcesToStructs(extension string, dst interface{}) (*gofig.Config, error) {
 	sources := DefaultConfigSources(extension, supportedExtensions)
 	cnf := gofig.NewWithOptions("proxy", gofig.ParseEnv)
 	cnf.AddDriver(gooyaml.Driver)
@@ -73,8 +73,8 @@ func BindSourcesToStructs(extension string, dst interface{}) error {
 
 	err := cnf.BindStruct("", &dst)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	return nil
+	return cnf, nil
 }

proxy/pkg/command/root.go

@@ -67,7 +67,19 @@ func NewLogger(cfg *config.Config) log.Logger {
 
 // ParseConfig loads proxy configuration from known paths.
 func ParseConfig(c *cli.Context, cfg *config.Config) error {
-	return ociscfg.BindSourcesToStructs("proxy", cfg)
+	conf, err := ociscfg.BindSourcesToStructs("proxy", cfg)
+	if err != nil {
+		return err
+	}
+
+	// load all env variables relevant to the config in the current context.
+	conf.LoadOSEnv(config.GetEnv(), false)
+
+	if err = config.UnmapEnv(conf, cfg); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 // SutureService allows for the proxy command to be embedded and supervised by a suture supervisor tree.

proxy/pkg/config/env_mapping.go

@@ -0,0 +1,82 @@
+package config
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	gofig "github.com/gookit/config/v2"
+)
+
+var mappings = []struct {
+	gType   string // expected type, used for decoding. It is the type expected from gookit.
+	envName string // name of the env var
+	tagName string // name of the tag to select the value from. Tag names are to be unique.
+}{
+	{
+		gType:   "bool",
+		envName: "PROXY_ENABLE_BASIC_AUTH",
+		tagName: "enable_basic_auth",
+	},
+}
+
+// GetEnv fetches a list of known env variables for this extension.
+func GetEnv() []string {
+	var r []string
+	for i := range mappings {
+		r = append(r, mappings[i].envName)
+	}
+
+	return r
+}
+
+func UnmapEnv(gooconf *gofig.Config, cfg *Config) error {
+	for i := range mappings {
+		switch mappings[i].gType {
+		case "bool":
+			v := gooconf.Bool(mappings[i].envName)
+			if err := setField(cfg, mappings[i].tagName, v); err != nil {
+				return err
+			}
+		case "string":
+			v := gooconf.String(mappings[i].envName)
+			if err := setField(cfg, mappings[i].tagName, v); err != nil {
+				return err
+			}
+		default:
+			return fmt.Errorf("invalid type for env var: `%v`", mappings[i].envName)
+		}
+	}
+
+	return nil
+}
+
+// setField allows us to set a value on a struct selecting by its `mapstructure` tag.
+func setField(item interface{}, fieldName string, value interface{}) error {
+	v := reflect.ValueOf(item).Elem()
+	if !v.CanAddr() {
+		return fmt.Errorf("cannot assign to the item passed, item must be a pointer in order to assign")
+	}
+	fName := func(t reflect.StructTag) (string, error) {
+		if jt, ok := t.Lookup("mapstructure"); ok {
+			return strings.Split(jt, ",")[0], nil
+		}
+		return "", fmt.Errorf("tag %s provided does not define a json tag", fieldName)
+	}
+
+	fieldNames := map[string]int{}
+	for i := 0; i < v.NumField(); i++ {
+		typeField := v.Type().Field(i)
+		tag := typeField.Tag
+		jName, _ := fName(tag)
+		fieldNames[jName] = i
+	}
+
+	fieldNum, ok := fieldNames[fieldName]
+	if !ok {
+		return fmt.Errorf("field does not exist within the provided item")
+	}
+	fieldVal := v.Field(fieldNum)
+	fieldVal.Set(reflect.ValueOf(value))
+	return nil
+}