HTTP wrapper: Add helper for link header pagination

pkg/uhttp/pagination.go

@@ -0,0 +1,99 @@
+package uhttp
+
+import (
+	"strings"
+
+	"github.com/conductorone/baton-sdk/pkg/pagination"
+)
+
+/*
+ * Uhttp pagination handling.
+ * There are three common types of pagination:
+ * 1. NextLink: http header containing a url to fetch the next page
+ * 2. Cursor: http body containing a token to fetch the next page
+ * 3. Offset: offset + limit to fetch the next page
+ *    - Subset of offset: incremental page numbers
+ *
+ * All of these helper functions take a bag and push the next page state on (if there is a next page).
+ */
+
+type NextLinkConfig struct {
+	Header         string `json:"header,omitempty"` // HTTP header containing the next link. Defaults to "link".
+	Rel            string `json:"rel,omitempty"`    // The rel value to look for in the link header. Defaults to "next".
+	ResourceTypeID string `json:"resource_type_id,omitempty"`
+	ResourceID     string `json:"resource_id,omitempty"`
+}
+
+// Parses the link header and returns a map of rel values to URLs.
+func parseLinkHeader(header string) (map[string]string, error) {
+	if header == "" {
+		// Empty header is fine, it just means there are no more pages.
+		return nil, nil
+	}
+
+	links := make(map[string]string)
+	headerLinks := strings.Split(header, ",")
+	for _, headerLink := range headerLinks {
+		linkParts := strings.Split(headerLink, ";")
+		if len(linkParts) < 2 {
+			continue
+		}
+		linkUrl := strings.TrimSpace(linkParts[0])
+		linkUrl = strings.Trim(linkUrl, "<>")
+		var relValue string
+		for _, rel := range linkParts[1:] {
+			rel = strings.TrimSpace(rel)
+			relParts := strings.Split(rel, "=")
+			if len(relParts) < 2 {
+				continue
+			}
+			if relParts[0] == "rel" {
+				relValue = strings.Trim(relParts[1], "\"")
+				break
+			}
+		}
+		if relValue == "" {
+			continue
+		}
+		links[relValue] = linkUrl
+	}
+
+	return links, nil
+}
+
+// WithNextLinkPagination handles nextlink pagination.
+// The config is optional, and if not provided, the default config will be used.
+func WithNextLinkPagination(bag *pagination.Bag, config *NextLinkConfig) DoOption {
+	return func(resp *WrapperResponse) error {
+		if config == nil {
+			config = &NextLinkConfig{
+				Header: "link",
+				Rel:    "next",
+			}
+		}
+		if config.Header == "" {
+			config.Header = "link"
+		}
+		if config.Rel == "" {
+			config.Rel = "next"
+		}
+		nextLinkVal := resp.Header.Get(config.Header)
+		if nextLinkVal == "" {
+			return nil
+		}
+		links, err := parseLinkHeader(nextLinkVal)
+		if err != nil {
+			return err
+		}
+		nextLink := links[config.Rel]
+		if nextLink == "" {
+			return nil
+		}
+		bag.Push(pagination.PageState{
+			Token:          nextLink,
+			ResourceTypeID: config.ResourceTypeID,
+			ResourceID:     config.ResourceID,
+		})
+		return nil
+	}
+}

pkg/uhttp/pagination_test.go

@@ -0,0 +1,23 @@
+package uhttp
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Parses the link header and returns a map of rel values to URLs.
+func TestParseLinkHeader(t *testing.T) {
+	//nolint:revive // This is fine
+	// Example link header value: <https://api.github.com/repositories/1300192/issues?page=2>; rel="prev", <https://api.github.com/repositories/1300192/issues?page=4>; rel="next", <https://api.github.com/repositories/1300192/issues?page=515>; rel="last", <https://api.github.com/repositories/1300192/issues?page=1>; rel="first"
+
+	//nolint:revive // This is fine
+	header := `<https://api.github.com/repositories/1300192/issues?page=2>; rel="prev", <https://api.github.com/repositories/1300192/issues?page=4>; rel="next", <https://api.github.com/repositories/1300192/issues?page=515>; rel="last", <https://api.github.com/repositories/1300192/issues?page=1>; rel="first"`
+
+	links, err := parseLinkHeader(header)
+	require.Nil(t, err)
+	require.Equal(t, "https://api.github.com/repositories/1300192/issues?page=2", links["prev"])
+	require.Equal(t, "https://api.github.com/repositories/1300192/issues?page=4", links["next"])
+	require.Equal(t, "https://api.github.com/repositories/1300192/issues?page=515", links["last"])
+	require.Equal(t, "https://api.github.com/repositories/1300192/issues?page=1", links["first"])
+}