Add UUID-Validator (#70)

- new uuid validator
- add testcases
- print warning message if uuid and regex validator is set for a field
- ignore the regex and uuid validator if both are set for a field.
- adding the string_not_empty validator to the example, makes it clearer that uuid_ver otherwise allows empty string

examples/nested.proto

@@ -12,4 +12,4 @@ message OuterMessage {
   string important_string = 1 [(validator.field) = {regex: "^[a-z]{2,5}$"}];
   // proto3 doesn't have `required`, the `msg_exist` enforces presence of InnerMessage.
   InnerMessage inner = 2 [(validator.field) = {msg_exists : true}];
-}
+}

examples/uuid.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+package validator.examples;
+import "github.com/mwitkow/go-proto-validators/validator.proto";
+
+message UUIDMsg {
+  // user_id must be a valid version 4 UUID.
+  string user_id = 1 [(validator.field) = {uuid_ver: 4, string_not_empty: true}];
+}

plugin/plugin.go

@@ -57,12 +57,18 @@ import (
 
 	"github.com/gogo/protobuf/gogoproto"
 	"github.com/gogo/protobuf/proto"
-	descriptor "github.com/gogo/protobuf/protoc-gen-gogo/descriptor"
+	"github.com/gogo/protobuf/protoc-gen-gogo/descriptor"
 	"github.com/gogo/protobuf/protoc-gen-gogo/generator"
 	"github.com/gogo/protobuf/vanity"
 	validator "github.com/mwitkow/go-proto-validators"
 )
 
+const uuidPattern = "^([a-fA-F0-9]{8}-" +
+	"[a-fA-F0-9]{4}-" +
+	"[%s][a-fA-F0-9]{3}-" +
+	"[8|9|aA|bB][a-fA-F0-9]{3}-" +
+	"[a-fA-F0-9]{12})?$"
+
 type plugin struct {
 	*generator.Generator
 	generator.PluginImports
@@ -154,9 +160,21 @@ func (p *plugin) generateRegexVars(file *generator.FileDescriptor, message *gene
 	ccTypeName := generator.CamelCaseSlice(message.TypeName())
 	for _, field := range message.Field {
 		validator := getFieldValidatorIfAny(field)
-		if validator != nil && validator.Regex != nil {
+		if validator != nil {
 			fieldName := p.GetOneOfFieldName(message, field)
-			p.P(`var `, p.regexName(ccTypeName, fieldName), ` = `, p.regexPkg.Use(), `.MustCompile(`, "`", *validator.Regex, "`", `)`)
+			if validator.Regex != nil && validator.UuidVer != nil {
+				fmt.Fprintf(os.Stderr, "WARNING: regex and uuid validator is set for field %v.%v, only one of them can be set. Regex and UUID validator is ignored for this field.", ccTypeName, fieldName)
+			} else if validator.UuidVer != nil {
+				uuid, err := getUUIDRegex(validator.UuidVer)
+				if err != nil {
+					fmt.Fprintf(os.Stderr, "WARNING: field %v.%v error %s.\n", ccTypeName, fieldName, err)
+				} else {
+					validator.Regex = &uuid
+					p.P(`var `, p.regexName(ccTypeName, fieldName), ` = `, p.regexPkg.Use(), `.MustCompile(`, "`", *validator.Regex, "`", `)`)
+				}
+			} else if validator.Regex != nil {
+				p.P(`var `, p.regexName(ccTypeName, fieldName), ` = `, p.regexPkg.Use(), `.MustCompile(`, "`", *validator.Regex, "`", `)`)
+			}
 		}
 	}
 }
@@ -500,8 +518,32 @@ func (p *plugin) generateFloatValidator(variableName string, ccTypeName string,
 	}
 }
 
+// getUUIDRegex returns a regex to validate that a string is in UUID
+// format. The version parameter specified the UUID version. If version is 0,
+// the returned regex is valid for any UUID version
+func getUUIDRegex(version *int32) (string, error) {
+	if version == nil {
+		return "", nil
+	} else if *version < 0 || *version > 5 {
+		return "", fmt.Errorf("UUID version should be between 0-5, Got %d", *version)
+	} else if *version == 0 {
+		return fmt.Sprintf(uuidPattern, "1-5"), nil
+	} else {
+		return fmt.Sprintf(uuidPattern, strconv.Itoa(int(*version))), nil
+	}
+}
+
 func (p *plugin) generateStringValidator(variableName string, ccTypeName string, fieldName string, fv *validator.FieldValidator) {
-	if fv.Regex != nil {
+	if fv.Regex != nil || fv.UuidVer != nil {
+		if fv.UuidVer != nil {
+			uuid, err := getUUIDRegex(fv.UuidVer)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "WARNING: field %v.%v error %s.\n", ccTypeName, fieldName, err)
+			} else {
+				fv.Regex = &uuid
+			}
+		}
+
 		p.P(`if !`, p.regexName(ccTypeName, fieldName), `.MatchString(`, variableName, `) {`)
 		p.In()
 		errorStr := "be a string conforming to regex " + strconv.Quote(fv.GetRegex())