#golang jsonparser with twitter api responses

cursored_resp.go

package twitter_api

import (
	"fmt"
	"strconv"

	"github.com/buger/jsonparser"
)

/*
The pseudocode to iterate over all responses from a cursored endpoint is:

	cursor = -1
	api_path = "https://api.twitter.com/1.1/endpoint.json?screen_name=targetUser"

	do {
		url_with_cursor = api_path + "&cursor=" + cursor
		response_dictionary = perform_http_get_request_for_url( url_with_cursor )
		cursor = response_dictionary[ 'next_cursor' ]
	}
	while ( cursor != 0 )

From https://developer.twitter.com/en/docs/basics/cursoring
*/
type CursoredResponse struct {
	NextCursor     int64
	PreviousCursor int64
	IDs            []int64
}

func (cursored *CursoredResponse) From(data *[]byte) {
	if data == nil || *data == nil {
		return
	}

	jsonparser.EachKey(*data, func(idx int, value []byte, dataType jsonparser.ValueType, err error) {
		if err != nil {
			panic(err)
		}
		switch idx {
		case 0:
			if dataType != jsonparser.Number {
				panic(fmt.Sprintf("unexpected data type %s", dataType))
			}
			cursored.NextCursor, err = jsonparser.ParseInt(value)
			if err != nil {
				panic(err)
			}
		case 1:
			if dataType != jsonparser.Number {
				panic(fmt.Sprintf("unexpected data type %s", dataType))
			}
			cursored.PreviousCursor, err = jsonparser.ParseInt(value)
			if err != nil {
				panic(err)
			}
		case 2:
			_, err = jsonparser.ArrayEach(value, func(value []byte, dataType jsonparser.ValueType, offset int, err error) {
				if err != nil {
					panic(err)
				}
				if dataType != jsonparser.Number {
					panic(fmt.Sprintf("unexpected data type %s", dataType))
				}
				i, err := strconv.ParseInt(string(value), 10, 64)
				if err != nil {
					panic(err)
				}
				cursored.IDs = append(cursored.IDs, i)
			})
			if err != nil {
				panic(err)
			}
		}
	}, [][]string{
		{"next_cursor"},
		{"previous_cursor"},
		{"ids"},
	}...)
}

cursored_resp_test.go

package twitter_api

import (
	"reflect"
	"testing"
)

func TestCursored_From(t *testing.T) {
	type fields struct {
		NextCursor     int64
		PreviousCursor int64
		IDs            []int64
	}
	type args struct {
		data []byte
	}
	tests := []struct {
		name   string
		fields fields
		args   args
	}{
		{
			name:   "zero_value",
			fields: fields{},
			args: args{
				data: []byte(`{}`),
			},
		},
		{
			name: "basic_values",
			fields: fields{
				NextCursor:     0,
				PreviousCursor: 0,
				IDs:            []int64{1, 2, 3},
			},
			args: args{
				data: []byte(`{"ids": [1, 2, 3], "next_cursor": 0, "previous_cursor": 0}`),
			},
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			cursored := &CursoredResponse{}
			cursored.From(&tt.args.data)

			if !reflect.DeepEqual(cursored.IDs, tt.fields.IDs) {
				t.Fatalf("got: %v, wanted: %v", cursored.IDs, tt.fields.IDs)
			}

			if cursored.NextCursor != tt.fields.NextCursor {
				t.Fatalf("got: %v, wanted: %v", cursored.NextCursor, tt.fields.NextCursor)
			}

			if cursored.PreviousCursor != tt.fields.PreviousCursor {
				t.Fatalf("got: %v, wanted: %v", cursored.PreviousCursor, tt.fields.PreviousCursor)
			}
		})
	}
}

error_resp.go

package twitter_api

import (
	"fmt"
	
	"github.com/buger/jsonparser"
	"github.com/pkg/errors"
)

var ErrNoData = errors.New("no data provided")

type Error struct {
	Message string `json:"message"`
	Code    int    `json:"code"`
}

// ErrorResponse example:
// {"errors":[{"message":"Sorry, that page does not exist","code":34}]}
type ErrorResponse struct {
	Errors []Error `json:"errors"`

	// for formatting error string
	method     string
	url        string
	statusCode int
	body       []byte
}

func (resp *ErrorResponse) Error() string {
	return fmt.Sprintf("received status %d with %s from %s %s", resp.statusCode, string(resp.body), resp.method, resp.url)
}

func (resp *ErrorResponse) First() (Error, bool) {
	if len(resp.Errors) == 0 {
		return Error{}, false
	}
	return resp.Errors[0], true
}

func (resp *ErrorResponse) From(data []byte) error {
	if data == nil {
		return ErrNoData
	}

	resp.Errors = []Error{}

	// {"errors": ...}
	value, _, _, err := jsonparser.Get(data, "errors")
	if err != nil {
		return err
	}

	// {"errors": [...]}
	_, err = jsonparser.ArrayEach(value, func(value []byte, dataType jsonparser.ValueType, _ int, err error) {
		if err != nil {
			panic(err)
		}

		resp.Errors = append(resp.Errors, parseError(value))
	})
	if err != nil {
		return err
	}

	return nil
}

func parseError(value []byte) Error {
	var errorObj Error
	// {"message": ..., "code": ...}
	jsonparser.EachKey(value, func(idx int, value []byte, dataType jsonparser.ValueType, err error) {
		if err != nil {
			panic(err)
		}
		switch idx {
		case 0:
			errorObj.Message, err = jsonparser.ParseString(value)
			if err != nil {
				panic(err)
			}
		case 1:
			code, err := jsonparser.ParseInt(value)
			if err != nil {
				panic(err)
			}
			errorObj.Code = int(code)
		}
	}, [][]string{
		{"message"},
		{"code"},
	}...)
	return errorObj
}