package oauth_test

import (
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"path/filepath"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"kode.naiv.no/olemd/forgejo-mcp-broker/internal/forgejo"
	brokerlog "kode.naiv.no/olemd/forgejo-mcp-broker/internal/log"
	"kode.naiv.no/olemd/forgejo-mcp-broker/internal/oauth"
	"kode.naiv.no/olemd/forgejo-mcp-broker/internal/store"
)

// fixture bundles the harness each test wires up: a real store, a fake
// Forgejo instance, an OAuth server, and an httptest.Server fronting it.
type fixture struct {
	t           *testing.T
	store       *store.Store
	server      *oauth.Server
	httpServer  *httptest.Server
	fakeForgejo *fakeForgejo
	now         func() time.Time
	clock       *atomic.Int64 // unix seconds
}

func newFixture(t *testing.T) *fixture {
	t.Helper()

	st, err := store.Open(t.Context(), filepath.Join(t.TempDir(), "broker.db"))
	if err != nil {
		t.Fatalf("store: %v", err)
	}
	t.Cleanup(func() { _ = st.Close() })

	fake := newFakeForgejo(t)

	fjClient, err := forgejo.NewClient(forgejo.ClientConfig{
		BaseURL: fake.server.URL, ClientID: "broker-app", ClientSecret: "broker-secret",
	})
	if err != nil {
		t.Fatalf("forgejo client: %v", err)
	}

	clock := &atomic.Int64{}
	clock.Store(time.Date(2026, 1, 1, 12, 0, 0, 0, time.UTC).Unix())
	now := func() time.Time { return time.Unix(clock.Load(), 0).UTC() }

	srv, err := oauth.NewServer(oauth.Config{
		Store: st, Forgejo: fjClient,
		Issuer: "https://broker.example.com",
		Scopes: "read:user write:repository",
		Now:    now,
		Log:    brokerlog.Discard(),
	})
	if err != nil {
		t.Fatalf("oauth.NewServer: %v", err)
	}
	t.Cleanup(srv.Close)

	httpSrv := httptest.NewServer(srv.Handler())
	t.Cleanup(httpSrv.Close)

	return &fixture{
		t:           t,
		store:       st,
		server:      srv,
		httpServer:  httpSrv,
		fakeForgejo: fake,
		now:         now,
		clock:       clock,
	}
}

// advance moves the test clock forward by d.
func (f *fixture) advance(d time.Duration) {
	f.clock.Add(int64(d.Seconds()))
}

// registerClient calls /oauth/register with the given redirect URIs and
// returns the issued client_id.
func (f *fixture) registerClient(redirectURIs ...string) string {
	f.t.Helper()
	body, _ := json.Marshal(map[string]any{"redirect_uris": redirectURIs, "client_name": "Test"})
	resp, err := http.Post(f.httpServer.URL+"/oauth/register",
		"application/json", strings.NewReader(string(body)))
	if err != nil {
		f.t.Fatalf("register: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusCreated {
		b, _ := io.ReadAll(resp.Body)
		f.t.Fatalf("register status %d: %s", resp.StatusCode, b)
	}
	var rr struct {
		ClientID string `json:"client_id"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&rr); err != nil {
		f.t.Fatalf("decode register: %v", err)
	}
	return rr.ClientID
}

// pkce returns (verifier, challenge) for a fresh PKCE pair.
func pkce(t *testing.T, verifier string) (string, string) {
	t.Helper()
	sum := sha256.Sum256([]byte(verifier))
	return verifier, base64.RawURLEncoding.EncodeToString(sum[:])
}

// noRedirectClient is an http.Client that does not follow redirects, so
// tests can inspect the 302 responses /authorize and /callback emit.
var noRedirectClient = &http.Client{
	CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse },
}

// fakeForgejo is the same minimal Forgejo stub used in the bridge
// integration test, plus the OAuth token + userinfo endpoints needed here.
type fakeForgejo struct {
	t      *testing.T
	server *httptest.Server

	tokenStatus      int
	tokenAccessToken string
	tokenRefresh     string
	tokenError       string

	userSub      string
	userUsername string
}

func newFakeForgejo(t *testing.T) *fakeForgejo {
	t.Helper()
	f := &fakeForgejo{
		t:                t,
		tokenStatus:      http.StatusOK,
		tokenAccessToken: "fj-access",
		tokenRefresh:     "fj-refresh",
		userSub:          "42",
		userUsername:     "alice",
	}
	mux := http.NewServeMux()
	mux.HandleFunc("/login/oauth/access_token", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(f.tokenStatus)
		if f.tokenError != "" {
			_, _ = io.WriteString(w, fmt.Sprintf(`{"error":%q}`, f.tokenError))
			return
		}
		_, _ = io.WriteString(w, fmt.Sprintf(
			`{"access_token":%q,"refresh_token":%q,"token_type":"bearer","expires_in":3600}`,
			f.tokenAccessToken, f.tokenRefresh))
	})
	mux.HandleFunc("/login/oauth/userinfo", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w, fmt.Sprintf(
			`{"sub":%q,"preferred_username":%q,"name":"Alice"}`, f.userSub, f.userUsername))
	})
	f.server = httptest.NewServer(mux)
	t.Cleanup(f.server.Close)
	return f
}

// --------------------------------------------------------------------------
// /oauth/register
// --------------------------------------------------------------------------

func TestRegister_HappyPath(t *testing.T) {
	fx := newFixture(t)
	body := `{"redirect_uris":["https://app.example.com/cb"],"client_name":"Demo"}`
	resp, err := http.Post(fx.httpServer.URL+"/oauth/register",
		"application/json", strings.NewReader(body))
	if err != nil {
		t.Fatalf("post: %v", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated {
		t.Errorf("status = %d, want 201", resp.StatusCode)
	}
	var rr map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&rr); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if rr["client_id"] == "" {
		t.Error("client_id empty")
	}
	if rr["token_endpoint_auth_method"] != "none" {
		t.Errorf("auth_method = %v, want none", rr["token_endpoint_auth_method"])
	}
}

func TestRegister_EmptyRedirectURIs(t *testing.T) {
	fx := newFixture(t)
	resp, _err := http.Post(fx.httpServer.URL+"/oauth/register",
		"application/json", strings.NewReader(`{"redirect_uris":[]}`))
	if _err != nil {
		t.Fatalf("http: %v", _err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestRegister_BadJSON(t *testing.T) {
	fx := newFixture(t)
	resp, _err := http.Post(fx.httpServer.URL+"/oauth/register",
		"application/json", strings.NewReader(`{not json`))
	if _err != nil {
		t.Fatalf("http: %v", _err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

// --------------------------------------------------------------------------
// /oauth/authorize
// --------------------------------------------------------------------------

func TestAuthorize_RedirectsToForgejo(t *testing.T) {
	fx := newFixture(t)
	clientID := fx.registerClient("https://app.example.com/cb")

	_, challenge := pkce(t, "verifier-123")
	q := url.Values{
		"response_type":         {"code"},
		"client_id":             {clientID},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"client-csrf"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
		"scope":                 {"read:user"},
	}
	resp, err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode())
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	resp.Body.Close()
	if resp.StatusCode != http.StatusFound {
		t.Fatalf("status = %d, want 302", resp.StatusCode)
	}
	loc := resp.Header.Get("Location")
	if !strings.Contains(loc, fx.fakeForgejo.server.URL+"/login/oauth/authorize") {
		t.Errorf("not redirected to Forgejo: %s", loc)
	}
}

func TestAuthorize_UnknownClient(t *testing.T) {
	fx := newFixture(t)
	q := url.Values{
		"response_type": {"code"},
		"client_id":     {"nope"},
		"redirect_uri":  {"https://app.example.com/cb"},
	}
	resp, _err := http.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestAuthorize_MismatchedRedirectURI(t *testing.T) {
	fx := newFixture(t)
	clientID := fx.registerClient("https://app.example.com/cb")
	q := url.Values{
		"response_type": {"code"},
		"client_id":     {clientID},
		"redirect_uri":  {"https://evil.example.com/cb"},
	}
	resp, _err := http.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestAuthorize_MissingPKCE_RedirectsWithError(t *testing.T) {
	fx := newFixture(t)
	clientID := fx.registerClient("https://app.example.com/cb")
	q := url.Values{
		"response_type": {"code"},
		"client_id":     {clientID},
		"redirect_uri":  {"https://app.example.com/cb"},
		"state":         {"st"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	if resp.StatusCode != http.StatusFound {
		t.Fatalf("status = %d, want 302", resp.StatusCode)
	}
	loc := resp.Header.Get("Location")
	if !strings.Contains(loc, "error=invalid_request") {
		t.Errorf("redirect missing error param: %s", loc)
	}
	if !strings.Contains(loc, "state=st") {
		t.Errorf("redirect missing state echo: %s", loc)
	}
}

func TestAuthorize_NonS256_RedirectsWithError(t *testing.T) {
	fx := newFixture(t)
	clientID := fx.registerClient("https://app.example.com/cb")
	q := url.Values{
		"response_type":         {"code"},
		"client_id":             {clientID},
		"redirect_uri":          {"https://app.example.com/cb"},
		"code_challenge":        {"abc"},
		"code_challenge_method": {"plain"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	if resp.StatusCode != http.StatusFound {
		t.Fatalf("status = %d, want 302", resp.StatusCode)
	}
	if !strings.Contains(resp.Header.Get("Location"), "error=invalid_request") {
		t.Errorf("missing error: %s", resp.Header.Get("Location"))
	}
}

// --------------------------------------------------------------------------
// /oauth/callback (also exercises the rest of the happy-path flow)
// --------------------------------------------------------------------------

// runFullFlow walks an entire authorize → callback → token sequence and
// returns the final token response. Used by happy-path tests and by
// downstream tests (refresh, revoke) that need a valid token to play with.
func runFullFlow(t *testing.T, fx *fixture, redirectURI, clientID, verifier string) tokenBundle {
	t.Helper()
	_, challenge := pkce(t, verifier)
	clientState := "client-csrf-" + verifier

	// 1. /authorize: capture the redirect to Forgejo and extract its state.
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {clientID},
		"redirect_uri":          {redirectURI},
		"state":                 {clientState},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
		"scope":                 {"read:user"},
	}
	resp, err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode())
	if err != nil {
		t.Fatalf("authorize: %v", err)
	}
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	forgejoState := loc.Query().Get("state")
	if forgejoState == "" {
		t.Fatalf("authorize did not produce a forgejo state: %s", loc)
	}

	// 2. /callback: simulate Forgejo redirecting back with code + state.
	cbQ := url.Values{"code": {"upstream-code"}, "state": {forgejoState}}
	resp, err = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" + cbQ.Encode())
	if err != nil {
		t.Fatalf("callback: %v", err)
	}
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")
	if brokerCode == "" {
		t.Fatalf("callback did not return broker code: %s", cbLoc)
	}
	if cbLoc.Query().Get("state") != clientState {
		t.Errorf("callback dropped client_state: got %q want %q",
			cbLoc.Query().Get("state"), clientState)
	}

	// 3. /token: exchange broker code for access+refresh tokens.
	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {clientID},
		"redirect_uri":  {redirectURI},
		"code_verifier": {verifier},
	}
	resp, err = http.PostForm(fx.httpServer.URL+"/oauth/token", form)
	if err != nil {
		t.Fatalf("token: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		t.Fatalf("token status = %d: %s", resp.StatusCode, b)
	}
	var tr tokenBundle
	if err := json.NewDecoder(resp.Body).Decode(&tr); err != nil {
		t.Fatalf("decode token: %v", err)
	}
	return tr
}

type tokenBundle struct {
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
	TokenType    string `json:"token_type"`
	ExpiresIn    int    `json:"expires_in"`
	Scope        string `json:"scope"`
}

func TestEndToEnd_RegisterAuthorizeCallbackToken(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-flow-1")

	if tok.AccessToken == "" || tok.RefreshToken == "" {
		t.Errorf("missing tokens: %+v", tok)
	}
	if tok.TokenType != "Bearer" {
		t.Errorf("TokenType = %q, want Bearer", tok.TokenType)
	}
}

func TestCallback_UnknownState(t *testing.T) {
	fx := newFixture(t)
	q := url.Values{"code": {"x"}, "state": {"unknown"}}
	resp, _err := http.Get(fx.httpServer.URL + "/oauth/callback?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

// --------------------------------------------------------------------------
// /oauth/token — additional grants and edge cases
// --------------------------------------------------------------------------

func TestToken_AuthCode_PKCEFails(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")

	// Authorize with one verifier, then try to exchange with a different one.
	_, challenge := pkce(t, "good-verifier")
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {cid},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"st"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	forgejoState := loc.Query().Get("state")

	resp, _ = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" +
		url.Values{"code": {"u"}, "state": {forgejoState}}.Encode())
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")

	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {cid},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {"WRONG-verifier"},
	}
	resp, err := http.PostForm(fx.httpServer.URL+"/oauth/token", form)
	if err != nil {
		t.Fatalf("post: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "PKCE") && !strings.Contains(string(body), "invalid_grant") {
		t.Errorf("expected PKCE error: %s", body)
	}
}

func TestToken_AuthCode_Reuse(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-reuse")

	// Same code can't be exchanged a second time.
	// Replay the third step; we need the broker_code, but runFullFlow
	// consumes it. Repeat the dance and try /token twice on the second go.
	_ = tok
	_, challenge := pkce(t, "verifier-reuse-2")
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {cid},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"st"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	forgejoState := loc.Query().Get("state")

	resp, _ = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" +
		url.Values{"code": {"u"}, "state": {forgejoState}}.Encode())
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")

	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {cid},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {"verifier-reuse-2"},
	}
	first, _ := http.PostForm(fx.httpServer.URL+"/oauth/token", form)
	first.Body.Close()
	if first.StatusCode != http.StatusOK {
		t.Fatalf("first /token status = %d", first.StatusCode)
	}
	second, err := http.PostForm(fx.httpServer.URL+"/oauth/token", form)
	if err != nil {
		t.Fatalf("second post: %v", err)
	}
	defer second.Body.Close()
	if second.StatusCode != http.StatusBadRequest {
		t.Errorf("second /token status = %d, want 400", second.StatusCode)
	}
}

func TestToken_Refresh_HappyPath(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	first := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-refresh-1")

	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {first.RefreshToken},
		"client_id":     {cid},
	}
	resp, err := http.PostForm(fx.httpServer.URL+"/oauth/token", form)
	if err != nil {
		t.Fatalf("refresh: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		t.Fatalf("status = %d: %s", resp.StatusCode, b)
	}
	var second tokenBundle
	if err := json.NewDecoder(resp.Body).Decode(&second); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if second.AccessToken == "" || second.RefreshToken == "" {
		t.Errorf("missing tokens: %+v", second)
	}
	if second.AccessToken == first.AccessToken {
		t.Error("new access token must differ from the original")
	}
	if second.RefreshToken == first.RefreshToken {
		t.Error("new refresh token must differ (rotation)")
	}

	// The original refresh should now be invalid.
	resp2, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp2.Body.Close()
	if resp2.StatusCode != http.StatusBadRequest {
		t.Errorf("reusing original refresh: status = %d, want 400", resp2.StatusCode)
	}
}

func TestToken_UnsupportedGrant(t *testing.T) {
	fx := newFixture(t)
	form := url.Values{"grant_type": {"client_credentials"}}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
	b, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(b), "unsupported_grant_type") {
		t.Errorf("expected unsupported_grant_type: %s", b)
	}
}

// --------------------------------------------------------------------------
// /oauth/revoke
// --------------------------------------------------------------------------

func TestRevoke_HappyPath(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-revoke")

	form := url.Values{"token": {tok.AccessToken}, "token_type_hint": {"access_token"}}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/revoke", form); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		t.Errorf("revoke status = %d, want 200", resp.StatusCode)
	}

	// Refresh should still work for the unrelated refresh token here, but
	// access-token validation lives in the /mcp middleware (phase 5b);
	// we just verify the row got revoked by checking the DB directly.
	var revokedAt int64
	row := fx.store.DB().QueryRow(
		`SELECT IFNULL(revoked_at, 0) FROM access_tokens WHERE token_hash =
		   (SELECT MIN(token_hash) FROM access_tokens WHERE client_id = ?)`,
		cid)
	if err := row.Scan(&revokedAt); err != nil {
		t.Fatalf("scan: %v", err)
	}
	if revokedAt == 0 {
		t.Error("access_token row was not marked revoked")
	}
}

func TestRevoke_UnknownToken_StillReturns200(t *testing.T) {
	// RFC 7009: the AS responds 200 even for unknown tokens, to prevent
	// clients from probing token validity via the revoke endpoint.
	fx := newFixture(t)
	form := url.Values{"token": {"clearly-not-a-real-token"}}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/revoke", form); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		t.Errorf("status = %d, want 200", resp.StatusCode)
	}
}

func TestRevoke_MissingToken(t *testing.T) {
	fx := newFixture(t)
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/revoke", url.Values{}); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

// --------------------------------------------------------------------------
// Callback error paths
// --------------------------------------------------------------------------

func TestCallback_ForgejoReportedError(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	forgejoState := startAuthorize(t, fx, cid, "https://app.example.com/cb", "verifier-cb-err", "client-st")

	// Forgejo redirects back with ?error=access_denied — we should
	// forward that to the client, not crash.
	q := url.Values{"error": {"access_denied"}, "error_description": {"user denied"}, "state": {forgejoState}}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()

	if resp.StatusCode != http.StatusFound {
		t.Fatalf("status = %d, want 302", resp.StatusCode)
	}
	loc := resp.Header.Get("Location")
	if !strings.Contains(loc, "error=access_denied") {
		t.Errorf("client redirect missing access_denied: %s", loc)
	}
	if !strings.Contains(loc, "state=client-st") {
		t.Errorf("client redirect missing original state: %s", loc)
	}
}

func TestCallback_NoCodeNoError(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	forgejoState := startAuthorize(t, fx, cid, "https://app.example.com/cb", "verifier-cb-noc", "st")

	// Empty callback (no code, no error) — should redirect with server_error.
	q := url.Values{"state": {forgejoState}}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if !strings.Contains(resp.Header.Get("Location"), "error=server_error") {
		t.Errorf("expected server_error redirect: %s", resp.Header.Get("Location"))
	}
}

func TestCallback_ForgejoExchangeFails(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	forgejoState := startAuthorize(t, fx, cid, "https://app.example.com/cb", "verifier-cb-fail", "st")

	// Make Forgejo's token endpoint return an error.
	fx.fakeForgejo.tokenStatus = http.StatusBadRequest
	fx.fakeForgejo.tokenError = "invalid_grant"

	q := url.Values{"code": {"u"}, "state": {forgejoState}}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" + q.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if !strings.Contains(resp.Header.Get("Location"), "error=server_error") {
		t.Errorf("expected server_error: %s", resp.Header.Get("Location"))
	}
}

// --------------------------------------------------------------------------
// Token grant error paths
// --------------------------------------------------------------------------

func TestToken_AuthCode_MissingFields(t *testing.T) {
	fx := newFixture(t)
	form := url.Values{"grant_type": {"authorization_code"}}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestToken_AuthCode_BadCode(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {"made-up-code"},
		"client_id":     {cid},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {"v"},
	}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "invalid_grant") {
		t.Errorf("expected invalid_grant: %s", body)
	}
}

func TestToken_AuthCode_ExpiredCode(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")

	// Walk authorize + callback to mint a code, then advance the clock
	// past the AuthCodeTTL before attempting /token.
	verifier := "verifier-expire"
	_, challenge := pkce(t, verifier)
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {cid},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"st"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	forgejoState := loc.Query().Get("state")

	resp, _ = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" +
		url.Values{"code": {"u"}, "state": {forgejoState}}.Encode())
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")

	fx.advance(oauth.AuthCodeTTL + time.Minute)

	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {cid},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {verifier},
	}
	resp2, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp2.Body.Close()
	body, _ := io.ReadAll(resp2.Body)
	if resp2.StatusCode != http.StatusBadRequest || !strings.Contains(string(body), "expired") {
		t.Errorf("expected expired error, got %d: %s", resp2.StatusCode, body)
	}
}

func TestToken_AuthCode_WrongClient(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	cid2 := fx.registerClient("https://other.example.com/cb")

	// Run authorize/callback for cid, then try /token under cid2.
	verifier := "verifier-wrongclient"
	_, challenge := pkce(t, verifier)
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {cid},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"st"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	forgejoState := loc.Query().Get("state")
	resp, _ = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" +
		url.Values{"code": {"u"}, "state": {forgejoState}}.Encode())
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")

	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {cid2},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {verifier},
	}
	resp2, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp2.Body.Close()
	body, _ := io.ReadAll(resp2.Body)
	if !strings.Contains(string(body), "client_id mismatch") {
		t.Errorf("expected client_id mismatch: %s", body)
	}
}

func TestToken_Refresh_MissingFields(t *testing.T) {
	fx := newFixture(t)
	form := url.Values{"grant_type": {"refresh_token"}}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestToken_Refresh_UnknownToken(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {"made-up-token"},
		"client_id":     {cid},
	}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

func TestToken_Refresh_WrongClientID(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	cid2 := fx.registerClient("https://other.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-rfwrong")

	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {tok.RefreshToken},
		"client_id":     {cid2},
	}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "client_id mismatch") {
		t.Errorf("expected client_id mismatch: %s", body)
	}
}

func TestToken_Refresh_RevokedToken(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-rfrev")

	// Revoke the refresh token via /oauth/revoke.
	revForm := url.Values{"token": {tok.RefreshToken}, "token_type_hint": {"refresh_token"}}
	revResp, _ := http.PostForm(fx.httpServer.URL+"/oauth/revoke", revForm)
	revResp.Body.Close()

	// Subsequent refresh attempt should fail.
	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {tok.RefreshToken},
		"client_id":     {cid},
	}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "revoked") {
		t.Errorf("expected revoked error: %s", body)
	}
}

func TestToken_Refresh_Expired(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	tok := runFullFlow(t, fx, "https://app.example.com/cb", cid, "verifier-rfexp")

	fx.advance(oauth.RefreshTokenTTL + time.Hour)

	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {tok.RefreshToken},
		"client_id":     {cid},
	}
	resp, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "expired") {
		t.Errorf("expected expired error: %s", body)
	}
}

func TestToken_AuthCode_WrongRedirectURI(t *testing.T) {
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	verifier := "verifier-wrongru"
	_, challenge := pkce(t, verifier)
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {cid},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"st"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, _err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + authQ.Encode()); if _err != nil { t.Fatalf("http: %v", _err) }
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	resp, _ = noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" +
		url.Values{"code": {"u"}, "state": {loc.Query().Get("state")}}.Encode())
	resp.Body.Close()
	cbLoc, _ := url.Parse(resp.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")

	form := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {cid},
		"redirect_uri":  {"https://different.example.com/cb"},
		"code_verifier": {verifier},
	}
	resp2, _err := http.PostForm(fx.httpServer.URL+"/oauth/token", form); if _err != nil { t.Fatalf("http: %v", _err) }
	defer resp2.Body.Close()
	body, _ := io.ReadAll(resp2.Body)
	if !strings.Contains(string(body), "redirect_uri mismatch") {
		t.Errorf("expected redirect_uri mismatch: %s", body)
	}
}

func TestToken_NoGrantType(t *testing.T) {
	fx := newFixture(t)
	resp, err := http.PostForm(fx.httpServer.URL+"/oauth/token", url.Values{})
	if err != nil {
		t.Fatalf("post: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

// --------------------------------------------------------------------------
// Pending-auth reaper
// --------------------------------------------------------------------------

func TestReap_RemovesExpiredPending(t *testing.T) {
	// Internal-API path: we can't call reapPending directly from the test
	// package, but we can drive the same effect via /callback's "unknown
	// state" path after time has advanced past PendingAuthTTL.
	fx := newFixture(t)
	cid := fx.registerClient("https://app.example.com/cb")
	forgejoState := startAuthorize(t, fx, cid, "https://app.example.com/cb", "verifier-reap", "st")

	fx.advance(oauth.PendingAuthTTL + time.Minute)

	// /callback with the (now-expired) state — pending entry's expiry is
	// rejected directly. Either the reaper has cleaned it (unknown state)
	// or the freshness check rejects it; both produce a 400.
	q := url.Values{"code": {"u"}, "state": {forgejoState}}
	resp, err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/callback?" + q.Encode())
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusBadRequest {
		t.Errorf("status = %d, want 400", resp.StatusCode)
	}
}

// --------------------------------------------------------------------------
// Discovery (.well-known)
// --------------------------------------------------------------------------

func TestDiscovery_AuthorizationServerMetadata(t *testing.T) {
	fx := newFixture(t)
	resp, err := http.Get(fx.httpServer.URL + "/.well-known/oauth-authorization-server")
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		t.Errorf("status = %d, want 200", resp.StatusCode)
	}
	if ct := resp.Header.Get("Content-Type"); !strings.HasPrefix(ct, "application/json") {
		t.Errorf("Content-Type = %q, want application/json", ct)
	}

	var md map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&md); err != nil {
		t.Fatalf("decode: %v", err)
	}

	// Issuer MUST come from cfg.Issuer, not from the request URL.
	if md["issuer"] != "https://broker.example.com" {
		t.Errorf("issuer = %v, want https://broker.example.com (config)", md["issuer"])
	}
	for _, k := range []string{"authorization_endpoint", "token_endpoint", "registration_endpoint", "revocation_endpoint"} {
		v, _ := md[k].(string)
		if !strings.HasPrefix(v, "https://broker.example.com/") {
			t.Errorf("%s = %q, want issuer-rooted URL", k, v)
		}
	}

	wantContains := map[string][]string{
		"code_challenge_methods_supported":      {"S256"},
		"grant_types_supported":                 {"authorization_code", "refresh_token"},
		"response_types_supported":              {"code"},
		"token_endpoint_auth_methods_supported": {"none"},
	}
	for field, vals := range wantContains {
		got, _ := md[field].([]any)
		if len(got) == 0 {
			t.Errorf("%s missing or empty", field)
			continue
		}
		for _, want := range vals {
			found := false
			for _, g := range got {
				if g == want {
					found = true
					break
				}
			}
			if !found {
				t.Errorf("%s does not include %q (got %v)", field, want, got)
			}
		}
	}

	scopes, _ := md["scopes_supported"].([]any)
	if len(scopes) != 2 {
		t.Errorf("scopes_supported = %v, want 2 entries", scopes)
	}
}

func TestDiscovery_ProtectedResourceMetadata(t *testing.T) {
	fx := newFixture(t)
	resp, err := http.Get(fx.httpServer.URL + "/.well-known/oauth-protected-resource")
	if err != nil {
		t.Fatalf("get: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		t.Errorf("status = %d, want 200", resp.StatusCode)
	}

	var md map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&md); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if md["resource"] != "https://broker.example.com/mcp" {
		t.Errorf("resource = %v, want issuer-rooted /mcp", md["resource"])
	}
	servers, _ := md["authorization_servers"].([]any)
	if len(servers) != 1 || servers[0] != "https://broker.example.com" {
		t.Errorf("authorization_servers = %v, want [config issuer]", servers)
	}
	bearer, _ := md["bearer_methods_supported"].([]any)
	if len(bearer) == 0 || bearer[0] != "header" {
		t.Errorf("bearer_methods_supported = %v, want [\"header\"]", bearer)
	}
}

func TestDiscovery_IssuerIgnoresHostHeader(t *testing.T) {
	// Crafting a malicious Host header must not leak that host into the
	// discovery document. Defense against the metadata-spoofing class of
	// OAuth attack starts here.
	fx := newFixture(t)
	req, err := http.NewRequest(http.MethodGet,
		fx.httpServer.URL+"/.well-known/oauth-authorization-server", nil)
	if err != nil {
		t.Fatalf("new request: %v", err)
	}
	req.Host = "evil.example.com"
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		t.Fatalf("do: %v", err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if strings.Contains(string(body), "evil.example.com") {
		t.Errorf("discovery doc leaked attacker-supplied Host: %s", body)
	}
}

// --------------------------------------------------------------------------
// Helpers used by /callback flow tests
// --------------------------------------------------------------------------

// startAuthorize walks just steps 1+2 of the flow (client → broker /authorize)
// and returns the forgejo state the broker stashed. Used by tests that need
// to drive /callback with arbitrary parameters afterwards.
func startAuthorize(t *testing.T, fx *fixture, clientID, redirectURI, verifier, clientState string) string {
	t.Helper()
	_, challenge := pkce(t, verifier)
	q := url.Values{
		"response_type":         {"code"},
		"client_id":             {clientID},
		"redirect_uri":          {redirectURI},
		"state":                 {clientState},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp, err := noRedirectClient.Get(fx.httpServer.URL + "/oauth/authorize?" + q.Encode())
	if err != nil {
		t.Fatalf("authorize: %v", err)
	}
	resp.Body.Close()
	loc, _ := url.Parse(resp.Header.Get("Location"))
	state := loc.Query().Get("state")
	if state == "" {
		t.Fatalf("no forgejo state in redirect: %s", loc)
	}
	return state
}

func TestNewServer_ValidationErrors(t *testing.T) {
	cases := []struct {
		name string
		cfg  oauth.Config
		want string
	}{
		{"no_store", oauth.Config{Forgejo: &forgejo.Client{}, Issuer: "https://x"}, "Store"},
		{"no_forgejo", oauth.Config{Store: &store.Store{}, Issuer: "https://x"}, "Forgejo"},
		{"no_issuer", oauth.Config{Store: &store.Store{}, Forgejo: &forgejo.Client{}}, "Issuer"},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			_, err := oauth.NewServer(tc.cfg)
			if err == nil || !strings.Contains(err.Error(), tc.want) {
				t.Errorf("want error containing %q, got %v", tc.want, err)
			}
		})
	}
}