package loginwidget

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"testing"
	"time"
)

const testToken = "123456:TESTTOKEN"

// signWidget builds validly signed Login Widget data for the token and fields,
// mirroring Telegram's algorithm (secret = SHA-256(token); HMAC over the sorted
// data-check string).
func signWidget(token string, fields map[string]string) string {
	keys := make([]string, 0, len(fields))
	for k := range fields {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	lines := make([]string, 0, len(keys))
	for _, k := range keys {
		lines = append(lines, k+"="+fields[k])
	}
	secret := sha256.Sum256([]byte(token))
	mac := hmac.New(sha256.New, secret[:])
	mac.Write([]byte(strings.Join(lines, "\n")))

	v := url.Values{}
	for k, val := range fields {
		v.Set(k, val)
	}
	v.Set("hash", hex.EncodeToString(mac.Sum(nil)))
	return v.Encode()
}

func freshFields() map[string]string {
	return map[string]string{
		"auth_date":  strconv.FormatInt(time.Now().Unix(), 10),
		"id":         "42",
		"username":   "neo",
		"first_name": "Thomas",
	}
}

func TestValidateOK(t *testing.T) {
	data := signWidget(testToken, freshFields())
	u, err := NewHMACValidator(testToken).Validate(data)
	if err != nil {
		t.Fatalf("validate: %v", err)
	}
	if u.ExternalID != "42" || u.Username != "neo" || u.FirstName != "Thomas" {
		t.Errorf("user = %+v, want {42 neo Thomas}", u)
	}
}

func TestValidateRejects(t *testing.T) {
	valid := signWidget(testToken, freshFields())

	t.Run("tampered hash", func(t *testing.T) {
		tampered := strings.Replace(valid, "hash=", "hash=00", 1)
		if _, err := NewHMACValidator(testToken).Validate(tampered); !errors.Is(err, ErrInvalidLoginWidget) {
			t.Errorf("err = %v, want ErrInvalidLoginWidget", err)
		}
	})
	t.Run("wrong token", func(t *testing.T) {
		if _, err := NewHMACValidator("other:TOKEN").Validate(valid); !errors.Is(err, ErrInvalidLoginWidget) {
			t.Errorf("err = %v, want ErrInvalidLoginWidget", err)
		}
	})
	t.Run("tampered field", func(t *testing.T) {
		// Flip the id after signing: the HMAC must no longer match.
		forged := strings.Replace(valid, "id=42", "id=43", 1)
		if _, err := NewHMACValidator(testToken).Validate(forged); !errors.Is(err, ErrInvalidLoginWidget) {
			t.Errorf("err = %v, want ErrInvalidLoginWidget", err)
		}
	})
	t.Run("missing hash", func(t *testing.T) {
		if _, err := NewHMACValidator(testToken).Validate("id=42&auth_date=1"); !errors.Is(err, ErrInvalidLoginWidget) {
			t.Errorf("err = %v, want ErrInvalidLoginWidget", err)
		}
	})
	t.Run("stale auth_date", func(t *testing.T) {
		stale := signWidget(testToken, map[string]string{
			"auth_date": strconv.FormatInt(time.Now().Add(-48*time.Hour).Unix(), 10),
			"id":        "42",
		})
		if _, err := NewHMACValidator(testToken).Validate(stale); !errors.Is(err, ErrInvalidLoginWidget) {
			t.Errorf("err = %v, want ErrInvalidLoginWidget", err)
		}
	})
}