package twitter

import (
	"fmt"
	"net/http"
	"regexp"
	"strings"
	"unicode/utf8"

	"forge.cadoles.com/pcaseiro/namecheck"
)

const (
	sizeMin        = 1
	sizeMax        = 15
	legalChars     = "^[a-zA-Z0-9_]+$"
	illegalPattern = "twitter"
	twitterUrl     = "https://twitter.com"
)

type Twitter struct {
	HttpClient http.Client
	Responds   bool
}

var (
	legal   = regexp.MustCompile(legalChars)
	illegal = regexp.MustCompile(illegalPattern)
)

func containsOnlyLegalChars(username string) bool {
	return legal.MatchString(username)
}

func containsNoIllegalPattern(username string) bool {
	if strings.Contains(strings.ToLower(username), illegalPattern) {
		return false
	}
	return true
}

func isLongEnough(username string) bool {
	return utf8.RuneCountInString(username) > sizeMin
}

func isShortEnough(username string) bool {
	return utf8.RuneCountInString(username) <= sizeMax
}

func (t *Twitter) IsValid(username string) bool {
	if !containsNoIllegalPattern(username) {
		return false
	}
	if !containsOnlyLegalChars(username) {
		return false
	}
	if !isLongEnough(username) {
		return false
	}

	if !isShortEnough(username) {
		return false
	}
	return true
}

// Name return a string with the name of the "Social Media"
func (t *Twitter) String() string {
	return "Twitter"
}

// IsAvailable check if a user name is valid and available on twitter
func (t *Twitter) IsAvailable(username string) (bool, error) {
	resp := t.IsValid(username)
	if resp {
		url := fmt.Sprintf("%s/%s", twitterUrl, username)
		resp, err := t.HttpClient.Get(url)
		if err != nil {
			t.Responds = false
			nerr := &namecheck.ErrUnknownAvailability{Username: username, Cause: err}
			return false, nerr
		}
		t.Responds = true
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusNotFound {
			return false, nil
		}
		return true, nil
	}
	return false, fmt.Errorf("Username is not valid")
}