added GetPaymentsWithFilter and Filter to list filtered payments

README.md

@@ -122,6 +122,20 @@ payment, err := c.GetPayment("PAY-17S8410768582940NKEE66EQ")
 
 ```go
 payments, err := c.GetPayments()
+
+//Or list payments with filters
+filter := &paypalsdk.Filter{}
+
+//With text fields
+filter.AddTextField("sort_by").Is = "create_time"
+filter.AddTextField("count").Is = "30"
+filter.AddTextField("sort_order").Is = "desc"
+
+//And time fields
+filter.AddTimeField("start_time").Is = time.Now().Add(-time.Hour * 24 * 30)
+filter.AddTimeField("stop_time").Is = time.Now()
+
+payments, err := c.GetPaymentsWithFilter(filter)
 ```
 
 ### Get authorization by ID

filter.go

@@ -0,0 +1,59 @@
+package paypalsdk
+
+import (
+	"fmt"
+	"time"
+)
+
+const format = "2006-01-02T15:04:05Z"
+
+type stringable interface {
+	String() string
+}
+
+type Filter struct {
+	fields []stringable
+}
+
+func (s *Filter) String() string {
+	filter := ""
+	for i, f := range s.fields {
+		if i == 0 {
+			filter = "?" + f.String()
+		} else {
+			filter = filter + "&" + f.String()
+		}
+	}
+
+	return filter
+}
+
+type TextField struct {
+	name string
+	Is   string
+}
+
+func (d TextField) String() string {
+	return fmt.Sprintf("%s=%s", d.name, d.Is)
+}
+
+type TimeField struct {
+	name string
+	Is   time.Time
+}
+
+func (d TimeField) String() string {
+	return fmt.Sprintf("%s=%s", d.name, d.Is.UTC().Format(format))
+}
+
+func (s *Filter) AddTextField(field string) *TextField {
+	f := &TextField{name: field}
+	s.fields = append(s.fields, f)
+	return f
+}
+
+func (s *Filter) AddTimeField(field string) *TimeField {
+	f := &TimeField{name: field}
+	s.fields = append(s.fields, f)
+	return f
+}

filter_test.go

@@ -0,0 +1,44 @@
+package paypalsdk
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFilter_AddTextField(t *testing.T) {
+	filter := &Filter{}
+	filter.AddTextField("sort_by").Is = "create_time"
+	filter.AddTextField("count").Is = "30"
+	filter.AddTextField("sort_order").Is = "desc"
+
+	expected := "?sort_by=create_time&count=30&sort_order=desc"
+	if filter.String() != expected {
+		t.Errorf("filter string was %s, wanted %s", filter.String(), expected)
+	}
+}
+
+func TestFilter_AddTimeField(t *testing.T) {
+	filter := &Filter{}
+	startTime := time.Time{}
+	endTime := startTime.Add(time.Hour * 24 * 30)
+	filter.AddTimeField("start_time").Is = startTime
+	filter.AddTimeField("stop_time").Is = endTime
+
+	expected := "?start_time=0001-01-01T00:00:00Z&stop_time=0001-01-31T00:00:00Z"
+	if filter.String() != expected {
+		t.Errorf("filter string was %s, wanted %s", filter.String(), expected)
+	}
+}
+
+func TestFilter_AddMixedFields(t *testing.T) {
+	filter := &Filter{}
+	startTime := time.Time{}
+	endTime := startTime.Add(time.Hour * 24 * 30)
+	filter.AddTimeField("stop_time").Is = endTime
+	filter.AddTextField("count").Is = "30"
+
+	expected := "?stop_time=0001-01-31T00:00:00Z&count=30"
+	if filter.String() != expected {
+		t.Errorf("filter string was %s, wanted %s", filter.String(), expected)
+	}
+}

payment.go

@@ -131,9 +131,19 @@ func (c *Client) PatchPayment(paymentID string, p []PaymentPatch) (*Payment, err
 // GetPayments retrieve payments resources from Paypal
 // Endpoint: GET /v1/payments/payment/
 func (c *Client) GetPayments() ([]Payment, error) {
+	return c.getPayments(nil)
+}
+
+// GetPayments retrieve payments resources from Paypal by the provided filter
+// Endpoint: GET /v1/payments/payment/
+func (c *Client) GetPaymentsWithFilter(filter *Filter) ([]Payment, error) {
+	return c.getPayments(filter)
+}
+
+func (c *Client) getPayments(filter *Filter) ([]Payment, error) {
 	var p ListPaymentsResp
 
-	req, err := http.NewRequest("GET", fmt.Sprintf("%s%s", c.APIBase, "/v1/payments/payment/"), nil)
+	req, err := http.NewRequest("GET", fmt.Sprintf("%s%s%s", c.APIBase, "/v1/payments/payment/", filter), nil)
 	if err != nil {
 		return p.Payments, err
 	}