Adding validate

Signed-off-by: mayank <mayank.patel@mayadata.io>

Author: mayank

main.go

@@ -13,7 +13,7 @@ import (
 	"strings"
 )
 
-var builder = []string{BuildTemplate, BuildVarTemplate}
+var builder = []string{BuildTemplate, BuildVarTemplate, ValidateTemplate, BuildFuncTemplate}
 var predicate = []string{PredicateTemplate, PredicateVarTemplate}
 var utils = []string{SetVarTemplate, GetVarTemplate}
 
@@ -138,7 +138,7 @@ func parseTemplate(template string, fs *ast.File, w *bufio.Writer) error {
 	shouldParseVar := true
 	predicateGenertor := false
 
-	if template == BuildTemplate || template == PredicateTemplate {
+	if template == BuildTemplate || template == PredicateTemplate || template == BuildFuncTemplate || template == ValidateTemplate {
 		shouldParseVar = false
 	}
 	if template == PredicateVarTemplate {
@@ -210,6 +210,11 @@ func parseTemplate(template string, fs *ast.File, w *bufio.Writer) error {
 }
 
 func copyStructFile(fs *ast.File, w *bufio.Writer) {
+	// import error package
+	_, err := fmt.Fprintf(w, "\nimport \"github.com/pkg/errors\"\n")
+	if err != nil {
+		log.Fatalf("Failed to write struct : %v", err)
+	}
 
 	// fs is a parsed, type-checked *ast.File.
 	ast.Inspect(fs, func(n ast.Node) bool {
@@ -243,7 +248,12 @@ func copyStructFile(fs *ast.File, w *bufio.Writer) {
 		return true
 	})
 
-	_, err := fmt.Fprintf(w, "}\n")
+	// Add predicatelist variable
+	if _, err := w.WriteString(BuilderFieldTemplate); err != nil {
+		log.Fatalf("Failed to add predicate and error filed : %v", err)
+	}
+
+	_, err = fmt.Fprintf(w, "}\n")
 	if err != nil {
 		log.Fatalf("Failed to write struct : %v", err)
 	}

template.go

@@ -12,6 +12,32 @@ var BuildTemplate = `
 func New$Struct() *$NewObj {
 	return &$Struct{}
 }
+
+// WithCheck add given predicate to predicate list
+func ($obj *$newobj) WithCheck(pred ...PredicateFunc) *$NewObj {
+	$obj.predicatelist = append($obj.predicatelist, pred...)
+	return $obj
+}
+`
+var ValidateTemplate = `
+// Validate is to validate generated $NewObj object by builder
+func ($obj *$newobj) Validate() *$NewObj {
+	if len($obj.predicatelist) != 0 {
+		for _, pred := range $obj.predicatelist {
+			if !pred($obj) {
+				errors.Wrapf($obj.err, "Failed to run predicate {%v}", pred)
+			}
+		}
+	}
+	return $obj
+}
+`
+var BuildFuncTemplate = `
+// Build returns the $NewObj object generated by builder
+func ($obj *$newobj) Build() (*$NewObj, error) {
+	$obj = $obj.Validate()
+	return $obj, $obj.err
+}
 `
 
 var SetVarTemplate = `
@@ -38,3 +64,11 @@ var PredicateTemplate = `
 // PredicateFunc defines data-type for validation function
 type PredicateFunc func(*$newobj) bool
 `
+
+var BuilderFieldTemplate = `
+	// predicatelist is list of predicate function used for validating object
+	predicatelist []PredicateFunc
+
+	// error
+	err error
+`