main.go

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"time"

	"github.com/kurrik/oauth1a"
	"github.com/kurrik/twittergo"
)

type UsersResponse struct {
	Users []*twittergo.User `json:"users"`
	Next  string            `json:"next_cursor_str"`
}

func main() {
	conf := &oauth1a.ClientConfig{
		ConsumerKey:    "Vldy5iHv2cUW4dZiF9LV9T3d0",
		ConsumerSecret: "oxBcYaraLjAsld7B4mFiqWT364ic4lkILdZh9gtBIkvzdO5bJi",
		CallbackURL:    "oob",
	}
	oauthUser := &oauth1a.UserConfig{}
	if b, err := ioutil.ReadFile("credentials"); err == nil {
		if err := json.Unmarshal(b, oauthUser); err != nil {
			oauthUser = &oauth1a.UserConfig{}
		}
	}

	c := twittergo.NewClient(conf, oauthUser)
	if err := authUser(c); err != nil {
		log.Fatal(err)
	}

	screenName := c.User.AccessValues.Get("screen_name")
	if screenName == "" {
		log.Fatal("Expecting screen_name in the credentials")
	}

	type user [2]string // id, screen_name

	var users []user
	_ = users

	cursor := "-1"
	for {
		vals := url.Values{
			"cursor":      []string{cursor},
			"screen_name": []string{screenName},
			"count":       []string{"200"},
			"skip_status": []string{"true"},
		}
		url := "/1.1/followers/list.json?" + vals.Encode()
		req, err := http.NewRequest("GET", url, nil)
		if err != nil {
			log.Fatal(err)
		}

		page := &UsersResponse{}
		resp, err := c.SendRequest(req)
		if err != nil {
			log.Fatal(err)
		}

		if resp.HasRateLimit() {
			log.Printf("Remaining: %d", resp.RateLimitRemaining())
			if resp.RateLimitRemaining() == 0 {
				log.Printf("Waiting until: %s", resp.RateLimitReset())
				time.Sleep(resp.RateLimitReset().Sub(time.Now()) + time.Second)
				continue // try again
			}
		}

		if err := resp.Parse(page); err != nil {
			log.Fatal("Parse: ", err)
		}
		log.Printf("Next page: %s", page.Next)

		for _, u := range page.Users {
			fmt.Printf("%s\t%s\n", u.IdStr(), u.ScreenName())
		}
		cursor = page.Next
		log.Printf("Got %d followers", len(page.Users))
		if len(page.Users) == 0 {
			break
		}
		time.Sleep(400 * time.Millisecond)
	}

	log.Print("Done!")
}

func authUser(c *twittergo.Client) error {
	// Check creds
	if c.User.AccessTokenSecret != "" {
		req, _ := http.NewRequest("GET", "/1.1/account/verify_credentials.json", nil)
		if resp, err := c.SendRequest(req); err == nil {
			if resp.StatusCode >= 200 && resp.StatusCode < 300 {
				return nil
			}
			log.Printf("Bad response from server: %#v", resp)
			return errors.New("bad response")
		}
	}

	if err := c.User.GetRequestToken(c.OAuth, http.DefaultClient); err != nil {
		return err
	}
	url, err := c.User.GetAuthorizeURL(c.OAuth)
	if err != nil {
		return err
	}
	fmt.Println("Go here:", url)
	fmt.Print("Enter the code shown: ")
	var code string
	if _, err := fmt.Scanf("%s\n", &code); err != nil {
		return err
	}
	if err := c.User.GetAccessToken(c.User.RequestTokenKey, code, c.OAuth, http.DefaultClient); err != nil {
		return err
	}
	b, err := json.Marshal(c.User)
	if err != nil {
		return err
	}
	return ioutil.WriteFile("credentials", b, 0600)
}