go-libs/pkg/transport/api/response.go

package api

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"

	bunpaginate "github.com/hanzo-fi/go-libs/v5/pkg/storage/bun/paginate"
)

type BaseResponse[T any] struct {
	Data   *T                     `json:"data,omitempty"`
	Cursor *bunpaginate.Cursor[T] `json:"cursor,omitempty"`
}

type ErrorResponse struct {
	ErrorCode    string `json:"errorCode,omitempty"`
	ErrorMessage string `json:"errorMessage,omitempty"`
	Details      string `json:"details,omitempty"`
}

func (e ErrorResponse) Error() string {
	return fmt.Sprintf("[%s] %s", e.ErrorCode, e.ErrorMessage)
}

func FetchAllPaginated[T any](ctx context.Context, client *http.Client, _url string, queryParams url.Values) ([]T, error) {
	ret := make([]T, 0)

	var nextToken string
	for {
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, _url, nil)
		if err != nil {
			return nil, err
		}
		if nextToken == "" {
			req.URL.RawQuery = queryParams.Encode()
		} else {
			req.URL.RawQuery = url.Values{
				"cursor": []string{nextToken},
			}.Encode()
		}
		rsp, err := client.Do(req)
		if err != nil {
			return nil, err
		}
		apiResponse, err := decodePaginatedResponse[T](rsp)
		if err != nil {
			return nil, err
		}
		ret = append(ret, apiResponse.Cursor.Data...)
		if !apiResponse.Cursor.HasMore {
			break
		}
		if apiResponse.Cursor.Next == "" || apiResponse.Cursor.Next == nextToken {
			return nil, errors.New("paginated response did not advance: empty or repeated next cursor while hasMore is true")
		}
		nextToken = apiResponse.Cursor.Next
	}
	return ret, nil
}

func decodePaginatedResponse[T any](rsp *http.Response) (*BaseResponse[T], error) {
	defer func() {
		_, _ = io.Copy(io.Discard, rsp.Body)
		_ = rsp.Body.Close()
	}()

	if rsp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("unexpected status code %d while waiting for %d", rsp.StatusCode, http.StatusOK)
	}
	apiResponse := &BaseResponse[T]{}
	if err := json.NewDecoder(rsp.Body).Decode(apiResponse); err != nil {
		return nil, fmt.Errorf("decoding cursor: %w", err)
	}
	if apiResponse.Cursor == nil {
		return nil, errors.New("missing cursor in paginated response")
	}
	return apiResponse, nil
}