package auth

import (
	"context"
	"errors"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

const testSecret = "test-signing-secret"

// sign builds a token with the given claims and method.
func sign(t *testing.T, method jwt.SigningMethod, claims jwt.Claims) string {
	t.Helper()

	s, err := jwt.NewWithClaims(method, claims).SignedString([]byte(testSecret))
	if err != nil {
		t.Fatalf("SignedString: %v", err)
	}
	return s
}

// validClaims returns an unexpired claim set for the verifier under test.
func validClaims() Claims {
	return Claims{
		RegisteredClaims: jwt.RegisteredClaims{
			Subject:   "user-42",
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Hour)),
			IssuedAt:  jwt.NewNumericDate(time.Now().Add(-time.Minute)),
		},
		Username: "ada",
		Email:    "ada@example.com",
	}
}

func TestJWTVerifierAcceptsValidToken(t *testing.T) {
	t.Parallel()

	v := NewJWTVerifier(testSecret, "", "")
	got, err := v.Verify(context.Background(), sign(t, jwt.SigningMethodHS256, validClaims()))
	if err != nil {
		t.Fatalf("Verify: %v", err)
	}
	if got.ID != "user-42" {
		t.Errorf("ID = %q, want user-42", got.ID)
	}
	if got.Username != "ada" {
		t.Errorf("Username = %q, want ada", got.Username)
	}
	if got.Email != "ada@example.com" {
		t.Errorf("Email = %q", got.Email)
	}
	if v.Name() != "jwt" {
		t.Errorf("Name = %q, want jwt", v.Name())
	}
}

func TestJWTVerifierFallsBackToSubjectForUsername(t *testing.T) {
	t.Parallel()

	// A token that only asserts a subject still has to yield a usable identity,
	// so the username defaults to the subject.
	claims := Claims{RegisteredClaims: jwt.RegisteredClaims{
		Subject:   "user-7",
		ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Hour)),
	}}
	v := NewJWTVerifier(testSecret, "", "")
	got, err := v.Verify(context.Background(), sign(t, jwt.SigningMethodHS256, claims))
	if err != nil {
		t.Fatalf("Verify: %v", err)
	}
	if got.Username != "user-7" {
		t.Errorf("Username = %q, want the subject as fallback", got.Username)
	}
}

func TestJWTVerifierRejections(t *testing.T) {
	t.Parallel()

	expired := Claims{RegisteredClaims: jwt.RegisteredClaims{
		Subject:   "user-42",
		ExpiresAt: jwt.NewNumericDate(time.Now().Add(-time.Hour)),
	}}
	noExp := Claims{RegisteredClaims: jwt.RegisteredClaims{Subject: "user-42"}}
	noSub := Claims{RegisteredClaims: jwt.RegisteredClaims{
		ExpiresAt: jwt.NewNumericDate(time.Now().Add(time.Hour)),
	}}

	tests := []struct {
		name  string
		token string
	}{
		{"empty", ""},
		{"expired", sign(t, jwt.SigningMethodHS256, expired)},
		{"missing expiration", sign(t, jwt.SigningMethodHS256, noExp)},
		{"missing subject", sign(t, jwt.SigningMethodHS256, noSub)},
		{"wrong secret", signWithSecret(t, jwt.SigningMethodHS256, validClaims(), "other-secret")},
		// The algorithm is pinned, so a token cannot pick "none" and skip
		// signature verification entirely.
		{"alg none", unsignedToken(t, validClaims())},
		{"garbage", "not-a-token"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			v := NewJWTVerifier(testSecret, "", "")
			if _, err := v.Verify(context.Background(), tc.token); err == nil {
				t.Error("Verify accepted a token it should have rejected")
			}
		})
	}
}

func TestJWTVerifierReportsMissingTokenDistinctly(t *testing.T) {
	t.Parallel()

	// The middleware needs to tell "you sent nothing" from "what you sent is
	// bad" so it can word the challenge properly.
	v := NewJWTVerifier(testSecret, "", "")
	if _, err := v.Verify(context.Background(), ""); !errors.Is(err, ErrMissingToken) {
		t.Errorf("err = %v, want ErrMissingToken", err)
	}
	if _, err := v.Verify(context.Background(), "garbage"); !errors.Is(err, ErrInvalidToken) {
		t.Errorf("err = %v, want ErrInvalidToken", err)
	}
}

func TestJWTVerifierRequiresConfiguredSecret(t *testing.T) {
	t.Parallel()

	// An empty secret must reject everything rather than accept a token signed
	// with an empty key.
	v := NewJWTVerifier("", "", "")
	_, err := v.Verify(context.Background(), sign(t, jwt.SigningMethodHS256, validClaims()))
	if !errors.Is(err, ErrInvalidToken) {
		t.Errorf("err = %v, want ErrInvalidToken", err)
	}
}

func TestJWTVerifierEnforcesAudienceAndIssuer(t *testing.T) {
	t.Parallel()

	claims := validClaims()
	claims.Audience = jwt.ClaimStrings{"go-places"}
	claims.Issuer = "go-loose"
	token := sign(t, jwt.SigningMethodHS256, claims)

	matching := NewJWTVerifier(testSecret, "go-places", "go-loose")
	if _, err := matching.Verify(context.Background(), token); err != nil {
		t.Errorf("Verify with matching aud/iss: %v", err)
	}

	// A token minted for a different client must not be accepted, or a token
	// issued for another service in the same cluster would grant access.
	wrongAudience := NewJWTVerifier(testSecret, "some-other-app", "go-loose")
	if _, err := wrongAudience.Verify(context.Background(), token); err == nil {
		t.Error("Verify accepted a token with the wrong audience")
	}
	wrongIssuer := NewJWTVerifier(testSecret, "go-places", "some-other-issuer")
	if _, err := wrongIssuer.Verify(context.Background(), token); err == nil {
		t.Error("Verify accepted a token from the wrong issuer")
	}

	// Skipping the checks is the documented behaviour of the empty arguments.
	unpinned := NewJWTVerifier(testSecret, "", "")
	if _, err := unpinned.Verify(context.Background(), token); err != nil {
		t.Errorf("Verify with no aud/iss configured: %v", err)
	}
}

func TestJWTVerifierHonoursContextCancellation(t *testing.T) {
	t.Parallel()

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	v := NewJWTVerifier(testSecret, "", "")
	_, err := v.Verify(ctx, sign(t, jwt.SigningMethodHS256, validClaims()))
	if !errors.Is(err, context.Canceled) {
		t.Errorf("err = %v, want context.Canceled", err)
	}
}

func TestDevVerifierAcceptsOnlyConfiguredTokens(t *testing.T) {
	t.Parallel()

	v := NewDevVerifier(nil)
	got, err := v.Verify(context.Background(), "valid_token")
	if err != nil {
		t.Fatalf("Verify: %v", err)
	}
	if got.ID != DefaultDevUser.ID {
		t.Errorf("ID = %q, want %q", got.ID, DefaultDevUser.ID)
	}
	if v.Name() != "dev" {
		t.Errorf("Name = %q, want dev", v.Name())
	}

	if _, err := v.Verify(context.Background(), "anything-else"); !errors.Is(err, ErrInvalidToken) {
		t.Errorf("err = %v, want ErrInvalidToken", err)
	}
	if _, err := v.Verify(context.Background(), ""); !errors.Is(err, ErrMissingToken) {
		t.Errorf("err = %v, want ErrMissingToken", err)
	}
}

func TestBearerToken(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name    string
		header  string
		want    string
		wantErr error
	}{
		{name: "standard", header: "Bearer abc.def.ghi", want: "abc.def.ghi"},
		{name: "lowercase scheme", header: "bearer abc", want: "abc"},
		{name: "mixed case scheme", header: "BeArEr abc", want: "abc"},
		{name: "extra spaces", header: "Bearer   abc  ", want: "abc"},
		{name: "bare token", header: "abc.def.ghi", want: "abc.def.ghi"},
		{name: "empty", header: "", wantErr: ErrMissingToken},
		{name: "whitespace only", header: "   ", wantErr: ErrMissingToken},
		{name: "scheme without token", header: "Bearer ", wantErr: ErrMissingToken},
		// A header naming some other scheme must not be silently read as a
		// bearer token.
		{name: "other scheme", header: "Basic dXNlcjpwYXNz", wantErr: ErrInvalidToken},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			got, err := BearerToken(tc.header)
			if tc.wantErr != nil {
				if !errors.Is(err, tc.wantErr) {
					t.Fatalf("err = %v, want %v", err, tc.wantErr)
				}
				return
			}
			if err != nil {
				t.Fatalf("unexpected error: %v", err)
			}
			if got != tc.want {
				t.Errorf("token = %q, want %q", got, tc.want)
			}
		})
	}
}

func TestMiddlewareAttachesUserToContext(t *testing.T) {
	t.Parallel()

	m := NewMiddleware(NewDevVerifier(nil))

	var seen User
	var ok bool
	h := m.WrapFunc(func(w http.ResponseWriter, r *http.Request) {
		seen, ok = FromContext(r.Context())
		w.WriteHeader(http.StatusNoContent)
	})

	req := httptest.NewRequest(http.MethodGet, "/places", nil)
	req.Header.Set("Authorization", "Bearer valid_token")
	rec := httptest.NewRecorder()
	h(rec, req)

	if rec.Code != http.StatusNoContent {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusNoContent)
	}
	if !ok {
		t.Fatal("the handler could not read the identity from the context")
	}
	if seen.ID != DefaultDevUser.ID {
		t.Errorf("user = %q, want %q", seen.ID, DefaultDevUser.ID)
	}
}

func TestMiddlewareRejectsUnusableCredentials(t *testing.T) {
	t.Parallel()

	m := NewMiddleware(NewDevVerifier(nil))

	tests := []struct {
		name   string
		header string
		body   string
	}{
		{name: "no header", body: "a bearer token is required"},
		{name: "bad token", header: "Bearer nope", body: "the token was rejected"},
		{name: "other scheme", header: "Basic dXNlcjpwYXNz", body: "the token was rejected"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			// Local to the subtest: the subtests run in parallel, so a shared
			// flag would be a data race.
			called := false
			h := m.WrapFunc(func(w http.ResponseWriter, r *http.Request) {
				called = true
			})

			req := httptest.NewRequest(http.MethodGet, "/places", nil)
			if tc.header != "" {
				req.Header.Set("Authorization", tc.header)
			}
			rec := httptest.NewRecorder()
			h.ServeHTTP(rec, req)

			if called {
				t.Error("the protected handler ran without a valid credential")
			}
			if rec.Code != http.StatusUnauthorized {
				t.Errorf("status = %d, want 401", rec.Code)
			}
			if got := rec.Header().Get("WWW-Authenticate"); !strings.HasPrefix(got, "Bearer") {
				t.Errorf("WWW-Authenticate = %q, want a Bearer challenge", got)
			}
			if body := rec.Body.String(); !strings.Contains(body, tc.body) {
				t.Errorf("body = %q, want it to mention %q", body, tc.body)
			}
		})
	}
}

func TestFromContextReportsAbsentIdentity(t *testing.T) {
	t.Parallel()

	if _, ok := FromContext(context.Background()); ok {
		t.Error("FromContext found an identity on a bare context")
	}
}

// signWithSecret signs with a different key to model a forged token.
func signWithSecret(t *testing.T, method jwt.SigningMethod, claims jwt.Claims, secret string) string {
	t.Helper()

	s, err := jwt.NewWithClaims(method, claims).SignedString([]byte(secret))
	if err != nil {
		t.Fatalf("SignedString: %v", err)
	}
	return s
}

// unsignedToken builds an alg=none token, the classic JWT downgrade attack.
func unsignedToken(t *testing.T, claims jwt.Claims) string {
	t.Helper()

	s, err := jwt.NewWithClaims(jwt.SigningMethodNone, claims).
		SignedString(jwt.UnsafeAllowNoneSignatureType)
	if err != nil {
		t.Fatalf("SignedString: %v", err)
	}
	return s
}