From db56162a0dc8757e169dffa5f3d90605b29a5ce7 Mon Sep 17 00:00:00 2001
From: Matthew Wood <matthewtylerwood@gmail.com>
Date: Fri, 3 Dec 2021 17:19:47 -0600
Subject: [PATCH] fixes #9 implement pattern validation on strings (#11)

Co-authored-by: Matthew Wood <mwood@firstorion.com>
---
 field.go      | 18 ++++++++++++++++++
 field_test.go | 20 ++++++++++++++++++++
 swagger.go    |  2 ++
 3 files changed, 40 insertions(+)

diff --git a/field.go b/field.go
index f221563..811fb4b 100644
--- a/field.go
+++ b/field.go
@@ -3,6 +3,7 @@ package crud
 import (
 	"fmt"
 	"reflect"
+	"regexp"
 	"strings"
 	"time"
 )
@@ -14,6 +15,7 @@ type Field struct {
 	obj         map[string]Field
 	max         *float64
 	min         *float64
+	pattern     *regexp.Regexp
 	required    *bool
 	example     interface{}
 	description string
@@ -64,6 +66,7 @@ var (
 	errMinimum      = fmt.Errorf("minimum exceeded")
 	errEnumNotFound = fmt.Errorf("value not in enum")
 	errUnknown      = fmt.Errorf("unknown value")
+	errPattern      = fmt.Errorf("value does not match pattern")
 )
 
 // Validate is used in the validation middleware to tell if the value passed
@@ -115,6 +118,9 @@ func (f *Field) Validate(value interface{}) error {
 		if f.min != nil && len(v) < int(*f.min) {
 			return errMinimum
 		}
+		if f.pattern != nil && !f.pattern.MatchString(v) {
+			return errPattern
+		}
 		switch f.format {
 		case FormatDateTime:
 			_, err := time.Parse(time.RFC3339, v)
@@ -328,6 +334,12 @@ func (f Field) Max(max float64) Field {
 	return f
 }
 
+// Pattern specifies a regex pattern value for this field
+func (f Field) Pattern(pattern string) Field {
+	f.pattern = regexp.MustCompile(pattern)
+	return f
+}
+
 // Required specifies the field must be provided. Can't be used with Default.
 func (f Field) Required() Field {
 	if f._default != nil {
@@ -460,6 +472,9 @@ func (f *Field) ToSwaggerParameters(in string) (parameters []Parameter) {
 				Minimum:     field.min,
 				Maximum:     field.max,
 			}
+			if field.pattern != nil {
+				param.Pattern = field.pattern.String()
+			}
 			if field.kind == KindArray {
 				if field.arr != nil {
 					temp := field.arr.ToJsonSchema()
@@ -518,6 +533,9 @@ func (f *Field) ToJsonSchema() JsonSchema {
 			if field.max != nil {
 				prop.Maximum = *field.max
 			}
+			if field.pattern != nil {
+				prop.Pattern = field.pattern.String()
+			}
 			if prop.Type == KindArray {
 				if field.arr != nil {
 					items := field.arr.ToJsonSchema()
diff --git a/field_test.go b/field_test.go
index 9b03432..9992653 100644
--- a/field_test.go
+++ b/field_test.go
@@ -27,6 +27,16 @@ func TestField_Min_Panic(t *testing.T) {
 	String().Max(1).Min(2)
 }
 
+func TestField_Pattern_Panic(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+
+	String().Pattern("[")
+}
+
 func TestField_String(t *testing.T) {
 	table := []struct {
 		Field    Field
@@ -93,6 +103,16 @@ func TestField_String(t *testing.T) {
 			Input:    "hi",
 			Expected: nil,
 		},
+		{
+			Field:    String().Pattern("[a-c]"),
+			Input:    "abc",
+			Expected: nil,
+		},
+		{
+			Field:    String().Pattern("[a-c]"),
+			Input:    "def",
+			Expected: errPattern,
+		},
 	}
 
 	for i, test := range table {
diff --git a/swagger.go b/swagger.go
index 98c256b..23b812e 100644
--- a/swagger.go
+++ b/swagger.go
@@ -26,6 +26,7 @@ type JsonSchema struct {
 	Maximum     float64               `json:"maximum,omitempty"`
 	Enum        []interface{}         `json:"enum,omitempty"`
 	Default     interface{}           `json:"default,omitempty"`
+	Pattern     string                `json:"pattern,omitempty"`
 }
 
 type Path struct {
@@ -58,6 +59,7 @@ type Parameter struct {
 	Minimum          *float64      `json:"minimum,omitempty"`
 	Maximum          *float64      `json:"maximum,omitempty"`
 	Enum             []interface{} `json:"enum,omitempty"`
+	Pattern          string        `json:"pattern,omitempty"`
 	Default          interface{}   `json:"default,omitempty"`
 	Items            *JsonSchema   `json:"items,omitempty"`
 	CollectionFormat string        `json:"collectionFormat,omitempty"`