feat(commerce): added CommerceListingsPagination and genArgsPagination for pagination handling

commerce.go

@@ -56,6 +56,12 @@ func (s *Session) CommerceListings(ids ...int) (items []*CommerceListing, err er
 	return
 }
 
+// CommerceListingsPagination returns buy and sell orders for the items with pagination
+func (s *Session) CommerceListingsPagination(page, pageSize int) (items []*CommerceListing, err error) {
+	err = s.get(concatStrings("/v2/commerce/listings", genArgsPagination(page, pageSize)), &items)
+	return
+}
+
 // CommerceListingsIds returns ids of all items available on trading post
 func (s *Session) CommerceListingsIds() (ids []int, err error) {
 	err = s.get("/v2/commerce/listings", &ids)

commerce_test.go

@@ -38,6 +38,15 @@ func TestCommerceListings(t *testing.T) {
 	}
 }
 
+func TestCommerceListingsPagination(t *testing.T) {
+	api := New()
+
+	_, err := api.CommerceListingsPagination(0, 201)
+	if err != nil {
+		t.Errorf("CommerceListingsPagination failed: '%s'", err)
+	}
+}
+
 func TestCommerceListingsIds(t *testing.T) {
 	api := New()
 	if _, err := api.CommerceListingsIds(); err != nil {

gw2api.go

@@ -3,6 +3,7 @@ package gw2api
 import (
 	"encoding/json"
 	"net/http"
+	"strconv"
 	"strings"
 )
 
@@ -138,3 +139,17 @@ func genArgsString(ids ...string) string {
 		return concatStrings("?ids=", strings.Join(ids, ","))
 	}
 }
+
+// genArgsPagination generates the http arguments for pagination based on the given page and page size
+// Official max page size is 200
+func genArgsPagination(page, pageSize int) string {
+	if pageSize == 0 {
+		pageSize = 10
+	}
+
+	if pageSize > 200 {
+		pageSize = 200
+	}
+
+	return concatStrings("?page=", strconv.Itoa(page), "&page_size=", strconv.Itoa(pageSize))
+}