Pagination

Simple pagination parameter parsing and validating

package main

import (
   "bytes"
   "fmt"
   "net/http"

   "github.com/alexisvisco/kcd/pkg/errors"
   validation "github.com/alexisvisco/ozzo-validation/v4"
   "github.com/go-chi/chi"

   "github.com/alexisvisco/kcd"
)

func main() {
   r := chi.NewRouter()
   r.Get("/{resourceId}", kcd.Handler(YourHttpHandler, http.StatusOK))
   _ = http.ListenAndServe(":3000", r)
}

type Pagination struct {
   Page    uint       `query:"page" default:"1"`
   Limit   uint       `query:"limit" default:"50"`
   OrderBy []*Ordered `query:"orderBy" exploder:"," default:"name:ASC"`
}

func (p *Pagination) Validate() error {
   return validation.ValidateStruct(p,
      validation.Field(&p.OrderBy),
   )
}

type Ordered struct {
   Field string
   Type  string
}

func (o *Ordered) UnmarshalText(text []byte) error {
   list := bytes.Split(text, []byte(":"))
   if len(list) != 2 {
      return errors.NewWithKind(errors.KindInvalidArgument, "order should be of form: field_name:(ASC|DESC)")
   }

   o.Field = string(list[0])
   o.Type = string(list[1])

   return nil
}

func (o *Ordered) Validate() error {
   return validation.ValidateStruct(o,
      validation.Field(&o.Field,
         validation.Required,
         validation.In("created_at", "price", "name").Error("Must be created_at, price or name"),
      ),
      validation.Field(&o.Type,
         validation.Required,
         validation.In("ASC", "DESC").Error("Must be ASC or DESC"),
      ),
   )
}

type ResourceInput struct {
   *Pagination
   ID         string `path:"resourceId"`
}

func YourHttpHandler(input *ResourceInput) (*ResourceInput, error) {
   fmt.Printf("%+v", input)
   return input, nil
}

// Test it : curl 'localhost:3000?orderBy=created_at:DESC,price:ASC'