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pagination.go
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pagination.go
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package linodego
/**
* Pagination and Filtering types and helpers
*/
import (
"crypto/sha256"
"encoding/hex"
"encoding/json"
"fmt"
"reflect"
"strconv"
"github.com/go-resty/resty/v2"
)
// PageOptions are the pagination parameters for List endpoints
type PageOptions struct {
Page int `json:"page" url:"page,omitempty"`
Pages int `json:"pages" url:"pages,omitempty"`
Results int `json:"results" url:"results,omitempty"`
}
// ListOptions are the pagination and filtering (TODO) parameters for endpoints
// nolint
type ListOptions struct {
*PageOptions
PageSize int `json:"page_size"`
Filter string `json:"filter"`
// QueryParams allows for specifying custom query parameters on list endpoint
// calls. QueryParams should be an instance of a struct containing fields with
// the `query` tag.
QueryParams any
}
// NewListOptions simplified construction of ListOptions using only
// the two writable properties, Page and Filter
func NewListOptions(page int, filter string) *ListOptions {
return &ListOptions{PageOptions: &PageOptions{Page: page}, Filter: filter}
}
// Hash returns the sha256 hash of the provided ListOptions.
// This is necessary for caching purposes.
func (l ListOptions) Hash() (string, error) {
data, err := json.Marshal(l)
if err != nil {
return "", fmt.Errorf("failed to cache ListOptions: %w", err)
}
h := sha256.New()
h.Write(data)
return hex.EncodeToString(h.Sum(nil)), nil
}
func applyListOptionsToRequest(opts *ListOptions, req *resty.Request) error {
if opts == nil {
return nil
}
if opts.QueryParams != nil {
params, err := flattenQueryStruct(opts.QueryParams)
if err != nil {
return fmt.Errorf("failed to apply list options: %w", err)
}
req.SetQueryParams(params)
}
if opts.PageOptions != nil && opts.Page > 0 {
req.SetQueryParam("page", strconv.Itoa(opts.Page))
}
if opts.PageSize > 0 {
req.SetQueryParam("page_size", strconv.Itoa(opts.PageSize))
}
if len(opts.Filter) > 0 {
req.SetHeader("X-Filter", opts.Filter)
}
return nil
}
type PagedResponse interface {
endpoint(...any) string
castResult(*resty.Request, string) (int, int, error)
}
// flattenQueryStruct flattens a structure into a Resty-compatible query param map.
// Fields are mapped using the `query` struct tag.
func flattenQueryStruct(val any) (map[string]string, error) {
result := make(map[string]string)
reflectVal := reflect.ValueOf(val)
// Deref pointer if necessary
if reflectVal.Kind() == reflect.Pointer {
if reflectVal.IsNil() {
return nil, fmt.Errorf("QueryParams is a nil pointer")
}
reflectVal = reflect.Indirect(reflectVal)
}
if reflectVal.Kind() != reflect.Struct {
return nil, fmt.Errorf(
"expected struct type for the QueryParams but got: %s",
reflectVal.Kind().String(),
)
}
valType := reflectVal.Type()
for i := range valType.NumField() {
currentField := valType.Field(i)
queryTag, ok := currentField.Tag.Lookup("query")
// Skip untagged fields
if !ok {
continue
}
valField := reflectVal.FieldByName(currentField.Name)
if !valField.IsValid() {
return nil, fmt.Errorf("invalid query param tag: %s", currentField.Name)
}
// Skip if it's a zero value
if valField.IsZero() {
continue
}
// Deref the pointer is necessary
if valField.Kind() == reflect.Pointer {
valField = reflect.Indirect(valField)
}
fieldString, err := queryFieldToString(valField)
if err != nil {
return nil, err
}
result[queryTag] = fieldString
}
return result, nil
}
func queryFieldToString(value reflect.Value) (string, error) {
switch value.Kind() {
case reflect.String:
return value.String(), nil
case reflect.Int64, reflect.Int32, reflect.Int:
return strconv.FormatInt(value.Int(), 10), nil
case reflect.Bool:
return strconv.FormatBool(value.Bool()), nil
default:
return "", fmt.Errorf("unsupported query param type: %s", value.Type().Name())
}
}
type legacyPagedResponse[T any] struct {
*PageOptions
Data []T `json:"data"`
}