package twitch

import (
	"context"
	"fmt"
	"net/http"
	"net/url"
	"regexp"
	"strconv"
	"strings"

	"github.com/trufflesecurity/trufflehog/v3/pkg/common"
	"github.com/trufflesecurity/trufflehog/v3/pkg/detectors"
	"github.com/trufflesecurity/trufflehog/v3/pkg/pb/detectorspb"
)

type Scanner struct {
	client *http.Client
}

// Ensure the Scanner satisfies the interface at compile time
var _ detectors.Detector = (*Scanner)(nil)

const verifyURL = "https://id.twitch.tv/oauth2/token"

var (
	defaultClient = common.SaneHttpClient()

	// Make sure that your group is surrounded in boundary characters such as below to reduce false positives
	keyPat = regexp.MustCompile(detectors.PrefixRegex([]string{"twitch"}) + `\b([0-9a-z]{30})\b`)
	idPat  = regexp.MustCompile(detectors.PrefixRegex([]string{"twitch"}) + `\b([0-9a-z]{30})\b`)
)

// Keywords are used for efficiently pre-filtering chunks.
// Use identifiers in the secret preferably, or the provider name.
func (s Scanner) Keywords() []string {
	return []string{"twitch"}
}

// FromData will find and optionally verify Twitch secrets in a given set of bytes.
func (s Scanner) FromData(ctx context.Context, verify bool, data []byte) (results []detectors.Result, err error) {
	dataStr := string(data)

	matches := keyPat.FindAllStringSubmatch(dataStr, -1)
	idMatches := idPat.FindAllStringSubmatch(dataStr, -1)

	for _, match := range matches {
		if len(match) != 2 {
			continue
		}
		resMatch := strings.TrimSpace(match[1])

		for _, idMatch := range idMatches {
			if len(idMatch) != 2 {
				continue
			}
			resIdMatch := strings.TrimSpace(idMatch[1])

			s1 := detectors.Result{
				DetectorType: detectorspb.DetectorType_Twitch,
				Raw:          []byte(resMatch),
			}

			if verify {
				client := s.getClient()
				isVerified, verificationErr := verifyTwitch(ctx, client, resMatch, resIdMatch)
				s1.Verified = isVerified
				s1.VerificationError = verificationErr
			}

			// This function will check false positives for common test words, but also it will make sure the key appears 'random' enough to be a real key
			if !s1.Verified && detectors.IsKnownFalsePositive(resMatch, detectors.DefaultFalsePositives, true) {
				continue
			}
			results = append(results, s1)
		}
	}
	return results, nil
}

func (s Scanner) getClient() *http.Client {
	if s.client != nil {
		return s.client
	}
	return defaultClient
}

func verifyTwitch(ctx context.Context, client *http.Client, resMatch string, resIdMatch string) (bool, error) {
	data := url.Values{}
	data.Set("client_id", resIdMatch)
	data.Set("client_secret", resMatch)
	data.Set("grant_type", "client_credentials")
	encodedData := data.Encode()

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, verifyURL, strings.NewReader(encodedData))
	if err != nil {
		return false, err
	}

	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
	req.Header.Add("Content-Length", strconv.Itoa(len(data.Encode())))
	res, err := client.Do(req)
	if err != nil {
		return false, err
	}
	defer res.Body.Close()

	switch res.StatusCode {
	case http.StatusOK:
		return true, nil
	case http.StatusBadRequest, http.StatusForbidden:
		return false, nil
	default:
		return false, fmt.Errorf("unexpected http response status %d", res.StatusCode)
	}
}

func (s Scanner) Type() detectorspb.DetectorType {
	return detectorspb.DetectorType_Twitch
}
