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configr.go
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configr.go
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// Configr provides an abstraction above configuration sources, allowing you to
// use a single interface to get all your configuration values
package configr
import (
"errors"
"fmt"
"reflect"
"sort"
"strings"
"unicode"
"unicode/utf8"
"github.com/mitchellh/mapstructure"
"github.com/spf13/cast"
)
const (
tagKeyName = "configr"
tagRequired = "required"
)
type Manager interface {
RegisterFromStruct(interface{}, ...NameToKeyFunc) error
RegisterKey(string, string, interface{}, ...Validator)
RequireKey(string, string, ...Validator)
AddSource(Source)
GenerateBlank(Encoder) ([]byte, error)
SetIsCaseSensitive(bool)
}
// Validator is a validation function which would be coupled with a configuration
// key, anytime the config key is found in a Source it's value is validated.
type Validator func(interface{}) error
// KeySplitter is a function that takes a key path and splits it into its sub-parts:
// In: "person.height.inches"
// Out: []string("person", "height", "inches")
type KeySplitter func(string) []string
// Converts a Struct Name or Field into an appropriate key name:
// In: "FromAddress"
// Out: "fromAddress"
type NameToKeyFunc func(string) string
type Config interface {
Parse() error
Parsed() bool
MustParse()
Get(string) (interface{}, error)
String(string) (string, error)
Bool(string) (bool, error)
Int(string) (int, error)
Float64(string) (float64, error)
Unmarshal(interface{}) error
UnmarshalKey(string, interface{}) error
}
// Source is a source of configuration keys and values, calling unmarshal should
// return a map[string]interface{} of all key/value pairs (nesting is supported)
// with multiple types. First arg is a slice of all expected keys.
type Source interface {
Unmarshal([]string, KeySplitter) (map[string]interface{}, error)
}
// Encoder would be used to encode registered and required values (along with
// their defaults or descriptions) into bytes.
type Encoder interface {
Marshal(interface{}) ([]byte, error)
}
func NewValidationError(key string, err error) ValidationError {
return ValidationError{
Key: key,
Err: err,
}
}
type ValidationError struct {
Key string
Err error
}
func (v ValidationError) Error() string {
return "Validation error on key '" + v.Key + "': " + v.Err.Error()
}
type InvalidTypeError struct {
Type reflect.Type
}
func (e InvalidTypeError) Error() string {
if e.Type == nil {
return "configr: Invalid type (nil)"
}
if e.Type.Kind() != reflect.Ptr {
return "configr: Invalid type (non-pointer " + e.Type.String() + ")"
}
return "configr: Invalid type (nil " + e.Type.String() + ")"
}
type Configr struct {
valueValidators map[string][]Validator
registeredKeys map[string]string
requiredKeys map[string]struct{}
defaultValues map[string]interface{}
cache map[string]interface{}
sources []Source
parsed bool
keyDelimeter string
descriptionWrapper string
isCaseInsensitive bool
keySplitterFn KeySplitter
}
func New() *Configr {
return &Configr{
valueValidators: make(map[string][]Validator),
registeredKeys: make(map[string]string),
requiredKeys: make(map[string]struct{}),
defaultValues: make(map[string]interface{}),
cache: make(map[string]interface{}),
keyDelimeter: ".",
descriptionWrapper: "***",
keySplitterFn: NewKeySplitter("."),
}
}
func GetConfigr() *Configr {
return globalConfigr
}
func SetConfigr(c *Configr) {
globalConfigr = c
}
var (
globalConfigr *Configr = New()
ErrKeyNotFound = errors.New("configr: Key not found")
ErrParseHasntBeenCalled = errors.New("configr: Trying to get values before calling Parse()")
ErrNoRegisteredValues = errors.New("configr: No registered values to generate")
)
type ErrRequiredKeysMissing []string
func (e ErrRequiredKeysMissing) Error() string {
sort.Strings(e)
return fmt.Sprintf("configr: Missing required configuration values: %v", []string(e))
}
// RegisterKey registers a configuration key (name) along with a description
// of what the configuration key is for, a default value and optional validators
//
// name supports nested notation in the form of '.' delimitered keys (unless changed)
// e.g.
// "user.age.month"
func RegisterKey(name, description string, defaultVal interface{}, validators ...Validator) {
globalConfigr.RegisterKey(name, description, defaultVal, validators...)
}
func (c *Configr) RegisterKey(name, description string, defaultVal interface{}, validators ...Validator) {
if c.isCaseInsensitive {
name = strings.ToLower(name)
}
c.registeredKeys[name] = description
if defaultVal != nil {
c.defaultValues[name] = defaultVal
c.cache = c.mergeMap(name, defaultVal, c.cache)
}
if len(validators) > 0 {
c.valueValidators[name] = validators
}
}
// RequireValue wraps the RegisterValue() call but upon parsing sources, if the
// configuration key (name) is not found, Parse() will return a
// ErrRequiredValuesMissing error
func RequireKey(name, description string, validators ...Validator) {
globalConfigr.RequireKey(name, description, validators...)
}
func (c *Configr) RequireKey(name, description string, validators ...Validator) {
if c.isCaseInsensitive {
name = strings.ToLower(name)
}
c.requiredKeys[name] = struct{}{}
c.RegisterKey(name, description, nil, validators...)
}
// AddSource registers Sources with the Configr instance to Unmarshal()
// when Parse() is called. Sources are parsed in a FILO order, meaning
// the first source added is considered the highest priority, and any
// keys from lower priority sources that are present in a higher will be
// overwritten
func AddSource(p Source) {
globalConfigr.AddSource(p)
}
func (c *Configr) AddSource(p Source) {
c.sources = append(c.sources, p)
}
// Parse calls Unmarshal on all registered sources, and caches the subsequent
// key/value's. Additional calls to Parse can be made to add additional config
// from sources.
//
// Sources are called in a FILO order, meaning the first source added is
// considered the highest priority, any keys set from lower priority sources
// found in higher priority will be overwritten.
func Parse() error {
return globalConfigr.Parse()
}
func (c *Configr) Parse() error {
if err := c.populateValues(); err != nil {
return err
}
if err := c.checkRequiredKeys(); err != nil {
return err
}
c.parsed = true
return nil
}
func (c *Configr) checkRequiredKeys() error {
missingKeys := []string{}
for requiredKey := range c.requiredKeys {
if _, err := c.get(requiredKey); err != nil {
missingKeys = append(missingKeys, requiredKey)
}
}
if len(missingKeys) > 0 {
return ErrRequiredKeysMissing(missingKeys)
}
return nil
}
func (c *Configr) populateValues() error {
expectedKeys := make([]string, 0, len(c.registeredKeys))
for key, _ := range c.registeredKeys {
expectedKeys = append(expectedKeys, key)
}
sort.Strings(expectedKeys)
for i := len(c.sources) - 1; i >= 0; i-- {
source := c.sources[i]
sourceValues, err := source.Unmarshal(expectedKeys, c.keySplitterFn)
if err != nil {
return err
}
for key, value := range sourceValues {
if err := c.set(key, value); err != nil {
return err
}
}
}
return nil
}
// MustParse wraps Parse() and will panic if there are any resulting errors
func MustParse() {
globalConfigr.MustParse()
}
func (c *Configr) MustParse() {
if err := c.Parse(); err != nil {
panic(err)
}
}
func (c *Configr) set(key string, value interface{}) error {
if c.isCaseInsensitive {
key = strings.ToLower(key)
}
if err := c.runValidators(key, value); err != nil {
return err
}
c.cache = c.mergeMap(key, value, c.cache)
return nil
}
func (c *Configr) mergeMap(key string, value interface{}, targetMap map[string]interface{}) map[string]interface{} {
if reflect.TypeOf(value).Kind() == reflect.Map {
targetMap = c.traverseSubMap(key, cast.ToStringMap(value), targetMap)
} else {
path := strings.SplitN(key, c.keyDelimeter, 2)
if len(path) == 2 {
targetMap = c.traverseKeyPath(path[0], path[1], value, targetMap)
} else {
if c.isCaseInsensitive {
key = strings.ToLower(key)
}
targetMap[key] = value
}
}
return targetMap
}
func (c *Configr) traverseKeyPath(currentKey, keyRemainder string, value interface{}, targetMap map[string]interface{}) map[string]interface{} {
if _, found := targetMap[currentKey]; !found {
targetMap[currentKey] = make(map[string]interface{})
}
targetMap[currentKey] = c.mergeMap(keyRemainder, value, targetMap[currentKey].(map[string]interface{}))
return targetMap
}
func (c *Configr) traverseSubMap(key string, value map[string]interface{}, targetMap map[string]interface{}) map[string]interface{} {
for subKey, subValue := range value {
if _, found := targetMap[key]; !found {
targetMap[key] = make(map[string]interface{})
}
targetMap[key] = c.mergeMap(subKey, subValue, targetMap[key].(map[string]interface{}))
}
return targetMap
}
func (c *Configr) runValidators(key string, value interface{}) error {
keysAndValues, err := c.findKeysAndValuesToValidate(key, value)
if err != nil {
return err
}
for validatorKey, valueToValidate := range keysAndValues {
if validators, found := c.valueValidators[validatorKey]; found {
for _, validate := range validators {
if err := validate(valueToValidate); err != nil {
return NewValidationError(validatorKey, err)
}
}
}
}
return nil
}
func (c *Configr) findKeysAndValuesToValidate(key string, value interface{}) (map[string]interface{}, error) {
keysAndValues := make(map[string]interface{})
if reflect.TypeOf(value).Kind() == reflect.Map {
for validatorKey := range c.valueValidators {
if !strings.HasPrefix(validatorKey, key) {
continue
}
valueToValidate := searchMap(cast.ToStringMap(value), strings.Split(validatorKey, c.keyDelimeter)[1:])
keysAndValues[validatorKey] = valueToValidate
}
} else {
keysAndValues[key] = value
}
return keysAndValues, nil
}
// Get can only be called after a Parse() has been done. Keys support the
// nested notation format:
// "user.age.month"
//
// If a key is not found but has been registered with a default, the default
// will be returned
func Get(key string) (interface{}, error) {
return globalConfigr.Get(key)
}
func (c *Configr) Get(key string) (interface{}, error) {
if !c.Parsed() {
return nil, ErrParseHasntBeenCalled
}
return c.get(key)
}
func (c *Configr) get(key string) (interface{}, error) {
if c.isCaseInsensitive {
key = strings.ToLower(key)
}
if value, found := c.cache[key]; found {
return value, nil
}
path := strings.Split(key, c.keyDelimeter)
parent, found := c.cache[path[0]]
if found {
if reflect.TypeOf(parent).Kind() == reflect.Map {
if val := searchMap(cast.ToStringMap(parent), path[1:]); val != nil {
return val, nil
}
}
}
return nil, ErrKeyNotFound
}
// From github.com/spf13/viper
func searchMap(source map[string]interface{}, path []string) interface{} {
if len(path) == 0 {
return source
}
if next, ok := source[path[0]]; ok {
switch next.(type) {
case map[string]interface{}:
// Type assertion is safe here since it is only reached
// if the type of `next` is the same as the type being asserted
return searchMap(next.(map[string]interface{}), path[1:])
default:
return next
}
} else {
return nil
}
}
// String wraps Get() and will attempt to cast the resulting value to a string
// or error
func String(key string) (string, error) {
return globalConfigr.String(key)
}
func (c *Configr) String(key string) (string, error) {
val, err := c.Get(key)
if err != nil {
return "", err
}
return cast.ToStringE(val)
}
// Bool wraps Get() and will attempt to cast the resulting value to a bool
// or error
func Bool(key string) (bool, error) {
return globalConfigr.Bool(key)
}
func (c *Configr) Bool(key string) (bool, error) {
val, err := c.Get(key)
if err != nil {
return false, err
}
return cast.ToBoolE(val)
}
// Int wraps Get() and will attempt to cast the resulting value to a int
// or error
func Int(key string) (int, error) {
return globalConfigr.Int(key)
}
func (c *Configr) Int(key string) (int, error) {
val, err := c.Get(key)
if err != nil {
return 0, err
}
return cast.ToIntE(val)
}
// Float64 wraps Get() and will attempt to cast the resulting value to a float64
// or error
func Float64(key string) (float64, error) {
return globalConfigr.Float64(key)
}
func (c *Configr) Float64(key string) (float64, error) {
val, err := c.Get(key)
if err != nil {
return 0, err
}
return cast.ToFloat64E(val)
}
// Parsed lets the caller know if a Parse() call has been made or not
func Parsed() bool {
return globalConfigr.Parsed()
}
func (c *Configr) Parsed() bool {
return c.parsed
}
// GenerateBlank generates a 'blank' configuration using the passed Encoder,
// it will honour nested keys, use default values where possible and when not
// fall back to placing the description as the value.
func GenerateBlank(e Encoder) ([]byte, error) {
return globalConfigr.GenerateBlank(e)
}
func (c *Configr) GenerateBlank(e Encoder) ([]byte, error) {
if len(c.registeredKeys) == 0 {
return []byte{}, ErrNoRegisteredValues
}
blankMap := make(map[string]interface{})
for key, description := range c.registeredKeys {
if defaultValue, found := c.defaultValues[key]; found {
blankMap = c.mergeMap(key, defaultValue, blankMap)
} else {
blankMap = c.mergeMap(key, c.wrapDescription(description), blankMap)
}
}
return e.Marshal(blankMap)
}
func (c *Configr) wrapDescription(description string) string {
return strings.Join([]string{c.descriptionWrapper, description, c.descriptionWrapper}, " ")
}
func (c *Configr) SetKeyPathDelimeter(delimeter string) {
c.keyDelimeter = delimeter
c.keySplitterFn = NewKeySplitter(delimeter)
}
func (c *Configr) SetDescriptionWrapper(wrapper string) {
c.descriptionWrapper = wrapper
}
func (c *Configr) SetIsCaseSensitive(isCaseSensitive bool) {
c.isCaseInsensitive = !isCaseSensitive
}
// Unmarshals all parsed values into struct, uses `configr` struct tag for
// alternative property name. e.g.
//
// type Example struct {
// property1 string `configr:"myproperty1"`
// }
//
func Unmarshal(destination interface{}) error {
return globalConfigr.Unmarshal(destination)
}
func (c *Configr) Unmarshal(destination interface{}) error {
return c.UnmarshalKey("", destination)
}
// UnmarshalKey unmarshals a subtree of parsed values from Key into a struct.
// Key follows the same rules as Get.
func UnmarshalKey(key string, destination interface{}) error {
return globalConfigr.UnmarshalKey(key, destination)
}
func (c *Configr) UnmarshalKey(key string, destination interface{}) error {
if !c.Parsed() {
return ErrParseHasntBeenCalled
}
decoderConfig := &mapstructure.DecoderConfig{
Metadata: nil,
WeaklyTypedInput: true,
Result: destination,
TagName: "configr",
}
decoder, err := mapstructure.NewDecoder(decoderConfig)
if err != nil {
return err
}
if key != "" {
subTree, err := c.Get(key)
if err != nil {
return err
}
return decoder.Decode(subTree)
}
return decoder.Decode(c.cache)
}
func RegisterFromStruct(structPtr interface{}, fieldToKeyFunc ...NameToKeyFunc) error {
return globalConfigr.RegisterFromStruct(structPtr, fieldToKeyFunc...)
}
func (c *Configr) RegisterFromStruct(structPtr interface{}, fieldToKeyFunc ...NameToKeyFunc) error {
reflectValue := reflect.ValueOf(structPtr)
if reflectValue.Kind() != reflect.Ptr ||
reflectValue.IsNil() {
return InvalidTypeError{reflectValue.Type()}
}
c.processFields([]string{}, structPtr, fieldToKeyFunc...)
return nil
}
func (c *Configr) processFields(path []string, strut interface{}, fieldToKeyFunc ...NameToKeyFunc) {
reflectType, reflectValue := c.fetchTypeAndValue(strut)
for i := 0; i < reflectType.NumField(); i++ {
c.processField(path, reflectType.Field(i), reflectValue.Field(i), fieldToKeyFunc...)
}
}
func (c *Configr) fetchTypeAndValue(strut interface{}) (reflect.Type, reflect.Value) {
if reflect.ValueOf(strut).Kind() == reflect.Ptr {
return reflect.TypeOf(strut).Elem(), reflect.ValueOf(strut).Elem()
}
return reflect.TypeOf(strut), reflect.ValueOf(strut)
}
func (c *Configr) processField(path []string, field reflect.StructField, value reflect.Value, fieldToKeyFunc ...NameToKeyFunc) {
tagValue := field.Tag.Get(tagKeyName)
tagParts := strings.Split(tagValue, ",")
name := c.pickFieldName(field.Name, tagParts[0], fieldToKeyFunc...)
isRequired := c.isRequiredField(tagParts[1:])
if field.Type.Kind() == reflect.Struct {
c.processFields(append(path, name), value.Interface(), fieldToKeyFunc...)
} else {
name = strings.Join(append(path, name), c.keyDelimeter)
if isRequired {
c.RequireKey(name, "")
} else {
c.RegisterKey(name, "", value.Interface())
}
}
}
func (c *Configr) pickFieldName(fieldName string, tagName string, fieldToKeyFunc ...NameToKeyFunc) string {
if tagName != "" {
return tagName
}
if fieldToKeyFunc != nil && len(fieldToKeyFunc) > 0 && fieldToKeyFunc[0] != nil {
return fieldToKeyFunc[0](fieldName)
}
if c.isCaseInsensitive {
return strings.ToLower(fieldName)
}
return fieldName
}
func (c *Configr) isRequiredField(parts []string) bool {
var required bool
for _, tag := range parts {
if tag == tagRequired {
required = true
}
}
return required
}
func NewKeySplitter(delimeter string) KeySplitter {
return func(key string) []string {
return strings.Split(key, delimeter)
}
}
func ToLowerCamelCase(s string) string {
if s == "" {
return ""
}
r, n := utf8.DecodeRuneInString(s)
return string(unicode.ToLower(r)) + s[n:]
}