add validation funcs

+package validation
+
+import (
+	"fmt"
+	"regexp"
+)
+
+type ValidationError struct {
+	Message, Key string
+}
+
+// Returns the Message.
+func (e *ValidationError) String() string {
+	if e == nil {
+		return ""
+	}
+	return e.Message
+}
+
+// A Validation context manages data validation and error messages.
+type Validation struct {
+	Errors []*ValidationError
+}
+
+func (v *Validation) Clear() {
+	v.Errors = []*ValidationError{}
+}
+
+func (v *Validation) HasErrors() bool {
+	return len(v.Errors) > 0
+}
+
+// Return the errors mapped by key.
+// If there are multiple validation errors associated with a single key, the
+// first one "wins".  (Typically the first validation will be the more basic).
+func (v *Validation) ErrorMap() map[string]*ValidationError {
+	m := map[string]*ValidationError{}
+	for _, e := range v.Errors {
+		if _, ok := m[e.Key]; !ok {
+			m[e.Key] = e
+		}
+	}
+	return m
+}
+
+// Add an error to the validation context.
+func (v *Validation) Error(message string, args ...interface{}) *ValidationResult {
+	result := (&ValidationResult{
+		Ok:    false,
+		Error: &ValidationError{},
+	}).Message(message, args...)
+	v.Errors = append(v.Errors, result.Error)
+	return result
+}
+
+// A ValidationResult is returned from every validation method.
+// It provides an indication of success, and a pointer to the Error (if any).
+type ValidationResult struct {
+	Error *ValidationError
+	Ok    bool
+}
+
+func (r *ValidationResult) Key(key string) *ValidationResult {
+	if r.Error != nil {
+		r.Error.Key = key
+	}
+	return r
+}
+
+func (r *ValidationResult) Message(message string, args ...interface{}) *ValidationResult {
+	if r.Error != nil {
+		if len(args) == 0 {
+			r.Error.Message = message
+		} else {
+			r.Error.Message = fmt.Sprintf(message, args)
+		}
+	}
+	return r
+}
+
+// Test that the argument is non-nil and non-empty (if string or list)
+func (v *Validation) Required(obj interface{}, key string) *ValidationResult {
+	return v.apply(Required{key}, obj)
+}
+
+func (v *Validation) Min(n int, min int, key string) *ValidationResult {
+	return v.apply(Min{min, key}, n)
+}
+
+func (v *Validation) Max(n int, max int, key string) *ValidationResult {
+	return v.apply(Max{max, key}, n)
+}
+
+func (v *Validation) Range(n, min, max int, key string) *ValidationResult {
+	return v.apply(Range{Min{Min: min}, Max{Max: max}, key}, n)
+}
+
+func (v *Validation) MinSize(obj interface{}, min int, key string) *ValidationResult {
+	return v.apply(MinSize{min, key}, obj)
+}
+
+func (v *Validation) MaxSize(obj interface{}, max int, key string) *ValidationResult {
+	return v.apply(MaxSize{max, key}, obj)
+}
+
+func (v *Validation) Length(obj interface{}, n int, key string) *ValidationResult {
+	return v.apply(Length{n, key}, obj)
+}
+
+func (v *Validation) Alpha(obj interface{}, n int, key string) *ValidationResult {
+	return v.apply(Alpha{key}, obj)
+}
+
+func (v *Validation) Numeric(obj interface{}, n int, key string) *ValidationResult {
+	return v.apply(Numeric{key}, obj)
+}
+
+func (v *Validation) AlphaNumeric(obj interface{}, n int, key string) *ValidationResult {
+	return v.apply(AlphaNumeric{key}, obj)
+}
+
+func (v *Validation) Match(str string, regex *regexp.Regexp, key string) *ValidationResult {
+	return v.apply(Match{regex, key}, str)
+}
+
+func (v *Validation) NoMatch(str string, regex *regexp.Regexp, key string) *ValidationResult {
+	return v.apply(NoMatch{Match{Regexp: regex}, key}, str)
+}
+
+func (v *Validation) AlphaDash(str string, key string) *ValidationResult {
+	return v.apply(AlphaDash{NoMatch{Match: Match{Regexp: alphaDashPattern}}, key}, str)
+}
+
+func (v *Validation) Email(str string, key string) *ValidationResult {
+	return v.apply(Email{Match{Regexp: emailPattern}, key}, str)
+}
+
+func (v *Validation) IP(str string, key string) *ValidationResult {
+	return v.apply(IP{Match{Regexp: ipPattern}, key}, str)
+}
+
+func (v *Validation) Base64(str string, key string) *ValidationResult {
+	return v.apply(Base64{Match{Regexp: base64Pattern}, key}, str)
+}
+
+func (v *Validation) apply(chk Validator, obj interface{}) *ValidationResult {
+	if chk.IsSatisfied(obj) {
+		return &ValidationResult{Ok: true}
+	}
+
+	// Add the error to the validation context.
+	err := &ValidationError{
+		Message: chk.DefaultMessage(),
+		Key:     chk.GetKey(),
+	}
+	v.Errors = append(v.Errors, err)
+
+	// Also return it in the result.
+	return &ValidationResult{
+		Ok:    false,
+		Error: err,
+	}
+}
+
+// Apply a group of validators to a field, in order, and return the
+// ValidationResult from the first one that fails, or the last one that
+// succeeds.
+func (v *Validation) Check(obj interface{}, checks ...Validator) *ValidationResult {
+	var result *ValidationResult
+	for _, check := range checks {
+		result = v.apply(check, obj)
+		if !result.Ok {
+			return result
+		}
+	}
+	return result
+}

-package revel
+package validation
 
 import (
 	"fmt"
@@ -10,9 +10,12 @@ import (
 type Validator interface {
 	IsSatisfied(interface{}) bool
 	DefaultMessage() string
+	GetKey() string
 }
 
-type Required struct{}
+type Required struct {
+	Key string
+}
 
 func (r Required) IsSatisfied(obj interface{}) bool {
 	if obj == nil {
@@ -42,11 +45,13 @@ func (r Required) DefaultMessage() string {
 	return "Required"
 }
 
-// TODO
-// type Unique struct {}
+func (r Required) GetKey() string {
+	return r.Key
+}
 
 type Min struct {
 	Min int
+	Key string
 }
 
 func (m Min) IsSatisfied(obj interface{}) bool {
@@ -61,8 +66,13 @@ func (m Min) DefaultMessage() string {
 	return fmt.Sprintln("Minimum is", m.Min)
 }
 
+func (m Min) GetKey() string {
+	return m.Key
+}
+
 type Max struct {
 	Max int
+	Key string
 }
 
 func (m Max) IsSatisfied(obj interface{}) bool {
@@ -77,10 +87,15 @@ func (m Max) DefaultMessage() string {
 	return fmt.Sprintln("Maximum is", m.Max)
 }
 
+func (m Max) GetKey() string {
+	return m.Key
+}
+
 // Requires an integer to be within Min, Max inclusive.
 type Range struct {
 	Min
 	Max
+	Key string
 }
 
 func (r Range) IsSatisfied(obj interface{}) bool {
@@ -91,9 +106,14 @@ func (r Range) DefaultMessage() string {
 	return fmt.Sprintln("Range is", r.Min.Min, "to", r.Max.Max)
 }
 
+func (r Range) GetKey() string {
+	return r.Key
+}
+
 // Requires an array or string to be at least a given length.
 type MinSize struct {
 	Min int
+	Key string
 }
 
 func (m MinSize) IsSatisfied(obj interface{}) bool {
@@ -111,9 +131,14 @@ func (m MinSize) DefaultMessage() string {
 	return fmt.Sprintln("Minimum size is", m.Min)
 }
 
+func (m MinSize) GetKey() string {
+	return m.Key
+}
+
 // Requires an array or string to be at most a given length.
 type MaxSize struct {
 	Max int
+	Key string
 }
 
 func (m MaxSize) IsSatisfied(obj interface{}) bool {
@@ -131,27 +156,38 @@ func (m MaxSize) DefaultMessage() string {
 	return fmt.Sprintln("Maximum size is", m.Max)
 }
 
+func (m MaxSize) GetKey() string {
+	return m.Key
+}
+
 // Requires an array or string to be exactly a given length.
 type Length struct {
-	N int
+	N   int
+	Key string
 }
 
-func (s Length) IsSatisfied(obj interface{}) bool {
+func (l Length) IsSatisfied(obj interface{}) bool {
 	if str, ok := obj.(string); ok {
-		return len(str) == s.N
+		return len(str) == l.N
 	}
 	v := reflect.ValueOf(obj)
 	if v.Kind() == reflect.Slice {
-		return v.Len() == s.N
+		return v.Len() == l.N
 	}
 	return false
 }
 
-func (s Length) DefaultMessage() string {
-	return fmt.Sprintln("Required length is", s.N)
+func (l Length) DefaultMessage() string {
+	return fmt.Sprintln("Required length is", l.N)
 }
 
-type Alpha struct{}
+func (l Length) GetKey() string {
+	return l.Key
+}
+
+type Alpha struct {
+	Key string
+}
 
 func (a Alpha) IsSatisfied(obj interface{}) bool {
 	if str, ok := obj.(string); ok {
@@ -168,7 +204,13 @@ func (a Alpha) DefaultMessage() string {
 	return fmt.Sprintln("Must be valid alpha characters")
 }
 
-type Numeric struct{}
+func (a Alpha) GetKey() string {
+	return a.Key
+}
+
+type Numeric struct {
+	Key string
+}
 
 func (n Numeric) IsSatisfied(obj interface{}) bool {
 	if str, ok := obj.(string); ok {
@@ -185,7 +227,13 @@ func (n Numeric) DefaultMessage() string {
 	return fmt.Sprintln("Must be valid numeric characters")
 }
 
-type AlphaNumeric struct{}
+func (n Numeric) GetKey() string {
+	return n.Key
+}
+
+type AlphaNumeric struct {
+	Key string
+}
 
 func (a AlphaNumeric) IsSatisfied(obj interface{}) bool {
 	if str, ok := obj.(string); ok {
@@ -202,9 +250,14 @@ func (a AlphaNumeric) DefaultMessage() string {
 	return fmt.Sprintln("Must be valid alpha or numeric characters")
 }
 
+func (a AlphaNumeric) GetKey() string {
+	return a.Key
+}
+
 // Requires a string to match a given regex.
 type Match struct {
 	Regexp *regexp.Regexp
+	Key    string
 }
 
 func (m Match) IsSatisfied(obj interface{}) bool {
@@ -216,55 +269,84 @@ func (m Match) DefaultMessage() string {
 	return fmt.Sprintln("Must match", m.Regexp)
 }
 
+func (m Match) GetKey() string {
+	return m.Key
+}
+
 // Requires a string to not match a given regex.
 type NoMatch struct {
 	Match
+	Key string
+}
+
+func (n NoMatch) IsSatisfied(obj interface{}) bool {
+	return !n.Match.IsSatisfied(obj)
 }
 
-func (m NoMatch) IsSatisfied(obj interface{}) bool {
-	return !m.Match.IsSatisfied(obj)
+func (n NoMatch) DefaultMessage() string {
+	return fmt.Sprintln("Must no match", n.Regexp)
 }
 
-func (m NoMatch) DefaultMessage() string {
-	return fmt.Sprintln("Must no match", m.Regexp)
+func (n NoMatch) GetKey() string {
+	return n.Key
 }
 
 var alphaDashPattern = regexp.MustCompile("[^\\d\\w-_]")
 
 type AlphaDash struct {
 	NoMatch
+	Key string
 }
 
 func (a AlphaDash) DefaultMessage() string {
 	return fmt.Sprintln("Must be valid characters")
 }
 
+func (a AlphaDash) GetKey() string {
+	return a.Key
+}
+
 var emailPattern = regexp.MustCompile("[\\w!#$%&'*+/=?^_`{|}~-]+(?:\\.[\\w!#$%&'*+/=?^_`{|}~-]+)*@(?:[\\w](?:[\\w-]*[\\w])?\\.)+[a-zA-Z0-9](?:[\\w-]*[\\w])?")
 
 type Email struct {
 	Match
+	Key string
 }
 
 func (e Email) DefaultMessage() string {
 	return fmt.Sprintln("Must be a valid email address")
 }
 
+func (e Email) GetKey() string {
+	return e.Key
+}
+
 var ipPattern = regexp.MustCompile("((2[0-4]\\d|25[0-5]|[01]?\\d\\d?)\\.){3}(2[0-4]\\d|25[0-5]|[01]?\\d\\d?)")
 
 type IP struct {
 	Match
+	Key string
 }
 
 func (i IP) DefaultMessage() string {
 	return fmt.Sprintln("Must be a valid ip address")
 }
 
+func (i IP) GetKey() string {
+	return i.Key
+}
+
 var base64Pattern = regexp.MustCompile("^(?:[A-Za-z0-99+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$")
 
 type Base64 struct {
 	Match
+	Key string
 }
 
 func (b Base64) DefaultMessage() string {
 	return fmt.Sprintln("Must be valid base64 characters")
 }
+
+func (b Base64) GetKey() string {
+	return b.Key
+}