package stripeapi

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"strconv"
	"testing"
	"time"
)

func signed(body string, at time.Time, secret string) string {
	ts := strconv.FormatInt(at.Unix(), 10)
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write([]byte(ts + "." + body))
	return "t=" + ts + ",v1=" + hex.EncodeToString(mac.Sum(nil))
}

func TestVerifySignature(t *testing.T) {
	t.Parallel()
	now := time.Unix(1_800_000_000, 0)
	body := `{"id":"evt_1"}`
	ok := signed(body, now, "whsec_new")
	for name, c := range map[string]struct {
		header, body string
		secrets      []string
		want         bool
	}{
		"good":                           {ok, body, []string{"whsec_new"}, true},
		"rotating, either":               {ok, body, []string{"whsec_old", "whsec_new"}, true},
		"two v1s, one good":              {ok + ",v1=00ff", body, []string{"whsec_new"}, true},
		"wrong secret":                   {ok, body, []string{"whsec_old"}, false},
		"body changed":                   {ok, `{"id":"evt_2"}`, []string{"whsec_new"}, false},
		"too old":                        {signed(body, now.Add(-6*time.Minute), "whsec_new"), body, []string{"whsec_new"}, false},
		"from the future":                {signed(body, now.Add(6*time.Minute), "whsec_new"), body, []string{"whsec_new"}, false},
		"no timestamp":                   {"v1=00", body, []string{"whsec_new"}, false},
		"empty":                          {"", body, []string{"whsec_new"}, false},
		"v0 only (Stripe's test scheme)": {"t=" + strconv.FormatInt(now.Unix(), 10) + ",v0=00", body, []string{"whsec_new"}, false},
	} {
		err := VerifySignature(c.header, []byte(c.body), c.secrets, now)
		if got := err == nil; got != c.want {
			t.Errorf("%s: verified %v, want %v", name, got, c.want)
		}
		if err != nil && !errors.Is(err, ErrBadSignature) {
			t.Errorf("%s: error %v is not ErrBadSignature", name, err)
		}
	}
}

// The window is five minutes either side of now: just inside passes,
// just outside fails.
func TestVerifySignatureTolerance(t *testing.T) {
	t.Parallel()
	now := time.Unix(1_800_000_000, 0)
	body := `{"id":"evt_1"}`
	secrets := []string{"whsec"}
	for name, c := range map[string]struct {
		at   time.Time
		want bool
	}{
		"4m59s old":   {now.Add(-4*time.Minute - 59*time.Second), true},
		"4m59s ahead": {now.Add(4*time.Minute + 59*time.Second), true},
		"5m01s old":   {now.Add(-5*time.Minute - time.Second), false},
		"5m01s ahead": {now.Add(5*time.Minute + time.Second), false},
	} {
		err := VerifySignature(signed(body, c.at, "whsec"), []byte(body), secrets, now)
		if got := err == nil; got != c.want {
			t.Errorf("%s: verified %v (%v), want %v", name, got, err, c.want)
		}
	}
}

// While a secret is being rotated Stripe signs with both; the second
// of two configured secrets is enough.
func TestVerifySignatureRotatingSecrets(t *testing.T) {
	t.Parallel()
	now := time.Unix(1_800_000_000, 0)
	body := `{"id":"evt_1"}`
	header := signed(body, now, "whsec_second")
	if err := VerifySignature(header, []byte(body), []string{"whsec_first", "whsec_second"}, now); err != nil {
		t.Fatalf("second secret did not match: %v", err)
	}
	if err := VerifySignature(header, []byte(body), []string{"whsec_first", "whsec_third"}, now); !errors.Is(err, ErrBadSignature) {
		t.Fatalf("neither secret matches, got %v", err)
	}
}