package hscontrol

import (
	"bytes"
	"context"
	"encoding/binary"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/juanfont/headscale/hscontrol/types"
	"github.com/juanfont/headscale/hscontrol/util"
	"github.com/rs/zerolog"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"tailscale.com/tailcfg"
	"tailscale.com/types/key"
	"tailscale.com/util/zstdframe"
)

// newNoiseRouterWithBodyLimit builds a chi router with the same body-limit
// middleware used in the real Noise router but wired to a test handler that
// captures the [io.ReadAll] result. This lets us verify the limit without
// needing a full [Headscale] instance.
func newNoiseRouterWithBodyLimit(readBody *[]byte, readErr *error) http.Handler {
	r := chi.NewRouter()
	r.Use(func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			r.Body = http.MaxBytesReader(w, r.Body, noiseBodyLimit)
			next.ServeHTTP(w, r)
		})
	})

	handler := func(w http.ResponseWriter, r *http.Request) {
		*readBody, *readErr = io.ReadAll(r.Body)
		if *readErr != nil {
			http.Error(w, "body too large", http.StatusRequestEntityTooLarge)

			return
		}

		w.WriteHeader(http.StatusOK)
	}

	r.Post("/machine/map", handler)
	r.Post("/machine/register", handler)

	return r
}

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

	t.Run("normal_map_request", func(t *testing.T) {
		t.Parallel()

		var body []byte

		var readErr error

		router := newNoiseRouterWithBodyLimit(&body, &readErr)

		mapReq := tailcfg.MapRequest{Version: 100, Stream: true}
		payload, err := json.Marshal(mapReq)
		require.NoError(t, err)

		req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/map", bytes.NewReader(payload))
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		require.NoError(t, readErr)
		assert.Equal(t, http.StatusOK, rec.Code)
		assert.Len(t, body, len(payload))
	})

	t.Run("oversized_body_rejected", func(t *testing.T) {
		t.Parallel()

		var body []byte

		var readErr error

		router := newNoiseRouterWithBodyLimit(&body, &readErr)

		oversized := bytes.Repeat([]byte("x"), int(noiseBodyLimit)+1)
		req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/map", bytes.NewReader(oversized))
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		require.Error(t, readErr)
		assert.Equal(t, http.StatusRequestEntityTooLarge, rec.Code)
		assert.LessOrEqual(t, len(body), int(noiseBodyLimit))
	})
}

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

	t.Run("normal_register_request", func(t *testing.T) {
		t.Parallel()

		var body []byte

		var readErr error

		router := newNoiseRouterWithBodyLimit(&body, &readErr)

		regReq := tailcfg.RegisterRequest{Version: 100}
		payload, err := json.Marshal(regReq)
		require.NoError(t, err)

		req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/register", bytes.NewReader(payload))
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		require.NoError(t, readErr)
		assert.Equal(t, http.StatusOK, rec.Code)
		assert.Len(t, body, len(payload))
	})

	t.Run("oversized_body_rejected", func(t *testing.T) {
		t.Parallel()

		var body []byte

		var readErr error

		router := newNoiseRouterWithBodyLimit(&body, &readErr)

		oversized := bytes.Repeat([]byte("x"), int(noiseBodyLimit)+1)
		req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/register", bytes.NewReader(oversized))
		rec := httptest.NewRecorder()
		router.ServeHTTP(rec, req)

		require.Error(t, readErr)
		assert.Equal(t, http.StatusRequestEntityTooLarge, rec.Code)
		assert.LessOrEqual(t, len(body), int(noiseBodyLimit))
	})
}

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

	var body []byte

	var readErr error

	router := newNoiseRouterWithBodyLimit(&body, &readErr)

	payload := bytes.Repeat([]byte("a"), int(noiseBodyLimit))
	req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/map", bytes.NewReader(payload))
	rec := httptest.NewRecorder()
	router.ServeHTTP(rec, req)

	require.NoError(t, readErr)
	assert.Equal(t, http.StatusOK, rec.Code)
	assert.Len(t, body, int(noiseBodyLimit))
}

// TestPollNetMapHandler_OversizedBody calls the real handler with a
// [http.MaxBytesReader]-wrapped body to verify it fails gracefully (json decode
// error on truncated data) rather than consuming unbounded memory.
func TestPollNetMapHandler_OversizedBody(t *testing.T) {
	t.Parallel()

	ns := &noiseServer{}

	oversized := bytes.Repeat([]byte("x"), int(noiseBodyLimit)+1)
	req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/map", bytes.NewReader(oversized))
	rec := httptest.NewRecorder()
	req.Body = http.MaxBytesReader(rec, req.Body, noiseBodyLimit)

	ns.PollNetMapHandler(rec, req)

	// Body is truncated → [json.Decoder.Decode] fails → [httpError] returns 500.
	assert.Equal(t, http.StatusInternalServerError, rec.Code)
}

// TestRegistrationHandler_OversizedBody calls the real handler with a
// [http.MaxBytesReader]-wrapped body to verify it returns an error response
// rather than consuming unbounded memory.
func TestRegistrationHandler_OversizedBody(t *testing.T) {
	t.Parallel()

	ns := &noiseServer{}

	oversized := bytes.Repeat([]byte("x"), int(noiseBodyLimit)+1)
	req := httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/register", bytes.NewReader(oversized))
	rec := httptest.NewRecorder()
	req.Body = http.MaxBytesReader(rec, req.Body, noiseBodyLimit)

	ns.RegistrationHandler(rec, req)

	// [json.Decoder.Decode] returns [http.MaxBytesError] → [regErr] wraps it → handler writes
	// a [tailcfg.RegisterResponse] with the error and then [rejectUnsupported] kicks in
	// for version 0 → returns 400.
	assert.Equal(t, http.StatusBadRequest, rec.Code)
}

// TestSSHActionRoute_OldPathReturns404 pins the wire-format shape of the
// SSH check-action endpoint. Pre-alignment headscale served
// /machine/ssh/action/from/{src}/to/{dst}?ssh_user=...; the current
// endpoint is /machine/ssh/action/{src}/to/{dst}?local_user=.... If
// someone re-adds the old route shape, this fails.
func TestSSHActionRoute_OldPathReturns404(t *testing.T) {
	t.Parallel()

	r := chi.NewRouter()
	r.Route("/machine", func(r chi.Router) {
		r.Get("/ssh/action/{src_node_id}/to/{dst_node_id}", func(w http.ResponseWriter, _ *http.Request) {
			w.WriteHeader(http.StatusOK)
		})
	})

	cases := []struct {
		name string
		path string
		want int
	}{
		{"new", "/machine/ssh/action/1/to/2", http.StatusOK},
		{"old-with-from", "/machine/ssh/action/from/1/to/2", http.StatusNotFound},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			req := httptest.NewRequestWithContext(context.Background(), http.MethodGet, tc.path, nil)
			rec := httptest.NewRecorder()
			r.ServeHTTP(rec, req)

			assert.Equal(t, tc.want, rec.Code)
		})
	}
}

// sshTestLocalUser is the non-root local user the SSH action tests log in as.
const sshTestLocalUser = "alice"

// newSSHActionRequest builds an httptest request with the chi URL params
// [noiseServer.SSHActionHandler] reads (src_node_id and dst_node_id), so the handler
// can be exercised directly without going through the chi router.
func newSSHActionRequest(t *testing.T, src, dst types.NodeID) *http.Request {
	t.Helper()

	url := fmt.Sprintf("/machine/ssh/action/%d/to/%d?local_user=%s",
		src.Uint64(), dst.Uint64(), sshTestLocalUser)
	req := httptest.NewRequestWithContext(context.Background(), http.MethodGet, url, nil)

	rctx := chi.NewRouteContext()
	rctx.URLParams.Add("src_node_id", strconv.FormatUint(src.Uint64(), 10))
	rctx.URLParams.Add("dst_node_id", strconv.FormatUint(dst.Uint64(), 10))
	req = req.WithContext(context.WithValue(req.Context(), chi.RouteCtxKey, rctx))

	return req
}

// putTestNodeInStore creates a node via the database test helper and
// also stages it into the in-memory [state.NodeStore] so handlers that read
// [state.NodeStore]-backed APIs (e.g. [state.State.GetNodeByID]) can see it.
func putTestNodeInStore(t *testing.T, app *Headscale, user *types.User, hostname string) *types.Node {
	t.Helper()

	node := app.state.CreateNodeForTest(user, hostname)
	app.state.PutNodeInStoreForTest(*node)

	return node
}

// sshCheckPolicy subjects every same-user pair of userName's nodes to an
// SSH check.
func sshCheckPolicy(userName string) string {
	return fmt.Sprintf(`{"ssh": [{
		"action": "check",
		"src":    [%q],
		"dst":    ["autogroup:self"],
		"users":  ["autogroup:nonroot"]
	}]}`, userName+"@")
}

// putSSHCheckNodes stages one node per hostname for a new user and sets
// [sshCheckPolicy], so the SSH action handler holds and delegates for any
// pair of them.
func putSSHCheckNodes(t *testing.T, app *Headscale, userName string, hostnames ...string) []*types.Node {
	t.Helper()

	user := app.state.CreateUserForTest(userName)
	require.NoError(t, app.state.UpdatePolicyManagerUsersForTest())

	nodes := make([]*types.Node, 0, len(hostnames))
	for _, hostname := range hostnames {
		node := app.state.CreateRegisteredNodeForTest(user, hostname)
		node.User = user
		app.state.PutNodeInStoreForTest(*node)
		nodes = append(nodes, node)
	}

	require.NoError(t, app.state.UpdatePolicyManagerNodesForTest())

	_, err := app.state.SetPolicy([]byte(sshCheckPolicy(userName)))
	require.NoError(t, err)

	_, checkFound := app.state.SSHCheckParams(nodes[0].ID, nodes[len(nodes)-1].ID, sshTestLocalUser)
	require.True(t, checkFound, "test setup: nodes must be subject to an SSH check")

	return nodes
}

// TestSSHActionHandler_RejectsRogueMachineKey verifies that the SSH
// check action endpoint rejects a Noise session whose machine key does
// not match the dst node.
func TestSSHActionHandler_RejectsRogueMachineKey(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	user := app.state.CreateUserForTest("ssh-handler-user")

	src := putTestNodeInStore(t, app, user, "src-node")
	dst := putTestNodeInStore(t, app, user, "dst-node")

	// [noiseServer] carries the wrong machine key — a fresh throwaway key,
	// not dst.MachineKey.
	rogue := key.NewMachine().Public()
	require.NotEqual(t, dst.MachineKey, rogue, "test sanity: rogue key must differ from dst")

	ns := &noiseServer{
		headscale:  app,
		machineKey: rogue,
	}

	rec := httptest.NewRecorder()
	ns.SSHActionHandler(rec, newSSHActionRequest(t, src.ID, dst.ID))

	assert.Equal(t, http.StatusUnauthorized, rec.Code,
		"rogue machine key must be rejected with 401")

	// And the auth cache must not have been mutated by the rejected request.
	if last, ok := app.state.GetLastSSHAuth(src.ID, dst.ID); ok {
		t.Fatalf("rejected SSH action must not record lastSSHAuth, got %v", last)
	}
}

// TestSSHActionHandler_RejectsUnknownDst verifies that the handler
// rejects a request for a dst_node_id that does not exist with 404.
func TestSSHActionHandler_RejectsUnknownDst(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	user := app.state.CreateUserForTest("ssh-handler-unknown-user")
	src := putTestNodeInStore(t, app, user, "src-node")

	ns := &noiseServer{
		headscale:  app,
		machineKey: key.NewMachine().Public(),
	}

	rec := httptest.NewRecorder()
	ns.SSHActionHandler(rec, newSSHActionRequest(t, src.ID, 9999))

	assert.Equal(t, http.StatusNotFound, rec.Code,
		"unknown dst node id must be rejected with 404")
}

// TestSSHActionFollowUp_RejectsBindingMismatch verifies that the
// follow-up handler refuses to honour an auth_id whose cached binding
// does not match the (src, dst) pair on the request URL. Without this
// check an attacker holding any auth_id could route its verdict to a
// different node pair.
func TestSSHActionFollowUp_RejectsBindingMismatch(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	nodes := putSSHCheckNodes(t, app, "ssh-binding-user",
		"src-cached", "dst-cached", "src-other", "dst-other")
	srcCached, dstCached, srcOther, dstOther := nodes[0], nodes[1], nodes[2], nodes[3]

	// Mint an SSH-check auth request bound to (srcCached, dstCached).
	authID := types.MustAuthID()
	app.state.SetAuthCacheEntry(
		authID,
		types.NewSSHCheckAuthRequest(srcCached.ID, dstCached.ID),
	)

	// Build a follow-up that claims to be for (srcOther, dstOther) but
	// reuses the bound auth_id. The Noise machineKey matches dstOther so
	// the outer machine-key check passes — only the binding check
	// should reject it.
	ns := &noiseServer{
		headscale:  app,
		machineKey: dstOther.MachineKey,
	}

	url := fmt.Sprintf(
		"/machine/ssh/action/%d/to/%d?local_user=%s&auth_id=%s",
		srcOther.ID.Uint64(), dstOther.ID.Uint64(), sshTestLocalUser, authID.String(),
	)
	req := httptest.NewRequestWithContext(context.Background(), http.MethodGet, url, nil)

	rctx := chi.NewRouteContext()
	rctx.URLParams.Add("src_node_id", strconv.FormatUint(srcOther.ID.Uint64(), 10))
	rctx.URLParams.Add("dst_node_id", strconv.FormatUint(dstOther.ID.Uint64(), 10))
	req = req.WithContext(context.WithValue(req.Context(), chi.RouteCtxKey, rctx))

	rec := httptest.NewRecorder()
	ns.SSHActionHandler(rec, req)

	assert.Equal(t, http.StatusUnauthorized, rec.Code,
		"binding mismatch must be rejected with 401")
}

// TestOverrideRemoteAddr asserts the middleware used inside the Noise
// tunnel pins r.RemoteAddr to the value captured from the outer
// (pre-hijack) request, so /machine/* requests log the trusted-proxy
// resolved client IP instead of the hijacked TCP socket's loopback peer.
func TestOverrideRemoteAddr(t *testing.T) {
	t.Parallel()

	const clientAddr = "192.168.91.240"

	r := chi.NewRouter()
	r.Use(overrideRemoteAddr(clientAddr))

	var observed string

	r.Get("/x", func(w http.ResponseWriter, r *http.Request) {
		observed = r.RemoteAddr

		w.WriteHeader(http.StatusOK)
	})

	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/x", nil)
	req.RemoteAddr = "127.0.0.1:44388"

	r.ServeHTTP(httptest.NewRecorder(), req)

	assert.Equal(t, clientAddr, observed)
}

// TestSSHActionHoldAndDelegate_PersistsAuthSession guards the happy path: the
// initial SSH-check poll returns a HoldAndDelegate URL carrying an auth_id, and
// that auth session must remain in the cache for the follow-up poll to find.
func TestSSHActionHoldAndDelegate_PersistsAuthSession(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	nodes := putSSHCheckNodes(t, app, "ssh-persist-user", "src-node", "dst-node")
	src, dst := nodes[0], nodes[1]

	ns := &noiseServer{headscale: app, machineKey: dst.MachineKey}

	rec := httptest.NewRecorder()
	ns.SSHActionHandler(rec, newSSHActionRequest(t, src.ID, dst.ID))
	require.Equal(t, http.StatusOK, rec.Code, "initial poll body=%s", rec.Body.String())

	var action tailcfg.SSHAction
	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &action))
	require.NotEmpty(t, action.HoldAndDelegate, "expected HoldAndDelegate, got %+v", action)

	u, err := url.Parse(action.HoldAndDelegate)
	require.NoError(t, err)

	authIDStr := u.Query().Get("auth_id")
	require.NotEmpty(t, authIDStr, "HoldAndDelegate URL missing auth_id: %s", action.HoldAndDelegate)

	authID, err := types.AuthIDFromString(authIDStr)
	require.NoError(t, err)

	_, ok := app.state.GetAuthCacheEntry(authID)
	require.True(t, ok, "auth session %s must persist after HoldAndDelegate", authID)
}

// TestSSHActionHandler_RejectsWithoutCheck verifies that a pair no check rule
// covers is denied with a 200 Reject on both the initial and the follow-up
// poll. Such a call comes from a client holding a stale check rule; an HTTP
// error would make tailssh retry for up to 30 minutes. Re-delegation for a
// missing session (issue #3305) applies only while a check is required.
// https://github.com/juanfont/headscale/issues/3508
func TestSSHActionHandler_RejectsWithoutCheck(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	user := app.state.CreateUserForTest("ssh-nocheck-user")
	src := putTestNodeInStore(t, app, user, "src-node")
	dst := putTestNodeInStore(t, app, user, "dst-node")

	_, checkFound := app.state.SSHCheckParams(src.ID, dst.ID, sshTestLocalUser)
	require.False(t, checkFound, "test setup: pair must not be subject to a check")

	ns := &noiseServer{headscale: app, machineKey: dst.MachineKey}

	for name, req := range map[string]*http.Request{
		"initial":   newSSHActionRequest(t, src.ID, dst.ID),
		"follow-up": newSSHActionFollowUpRequest(t, src.ID, dst.ID, types.MustAuthID()),
	} {
		rec := httptest.NewRecorder()
		ns.SSHActionHandler(rec, req)
		require.Equal(t, http.StatusOK, rec.Code, "%s: body=%s", name, rec.Body.String())

		var action tailcfg.SSHAction
		require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &action))
		assert.True(t, action.Reject, "%s: must reject, got %+v", name, action)
		assert.Empty(t, action.HoldAndDelegate, "%s: must not delegate", name)
	}
}

// TestSSHActionFollowUp_RejectsVerdictAfterCheckRemoved verifies the check is
// re-evaluated once the user authenticates: a rule removed while the login
// prompt was open must not grant access.
// https://github.com/juanfont/headscale/issues/3508
func TestSSHActionFollowUp_RejectsVerdictAfterCheckRemoved(t *testing.T) {
	t.Parallel()

	const userName = "ssh-verdict-user"

	nonrootOnly := sshCheckPolicy(userName)
	rootAndNonroot := strings.Replace(nonrootOnly,
		`["autogroup:nonroot"]`, `["root", "autogroup:nonroot"]`, 1)

	for name, tc := range map[string]struct {
		after     string // policy once the user has authenticated; "" keeps it
		localUser string
	}{
		"rule kept":    {"", sshTestLocalUser},
		"rule removed": {`{}`, sshTestLocalUser},
		// Another check rule still covers the pair, but not for root.
		"root rule removed": {nonrootOnly, "root"},
	} {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			app := createTestApp(t)
			nodes := putSSHCheckNodes(t, app, userName, "src-node", "dst-node")
			src, dst := nodes[0], nodes[1]

			_, err := app.state.SetPolicy([]byte(rootAndNonroot))
			require.NoError(t, err)

			authID := types.MustAuthID()
			app.state.SetAuthCacheEntry(authID, types.NewSSHCheckAuthRequest(src.ID, dst.ID))

			auth, ok := app.state.GetAuthCacheEntry(authID)
			require.True(t, ok)
			auth.FinishAuth(types.AuthVerdict{})

			if tc.after != "" {
				_, err := app.state.SetPolicy([]byte(tc.after))
				require.NoError(t, err)
			}

			ns := &noiseServer{headscale: app, machineKey: dst.MachineKey}

			// Call the follow-up directly: the verdict is already in, as if
			// the policy changed while the user was authenticating.
			action, err := ns.sshActionFollowUp(
				t.Context(), zerolog.Nop(), &tailcfg.SSHAction{},
				authID.String(), src.ID, dst.ID, tc.localUser,
			)
			require.NoError(t, err)

			kept := tc.after == ""
			_, recorded := app.state.GetLastSSHAuth(src.ID, dst.ID)

			assert.Equal(t, kept, action.Accept, "accept, got %+v", action)
			assert.Equal(t, !kept, action.Reject, "reject, got %+v", action)
			assert.Equal(t, kept, recorded, "auth recorded for auto-approval")
		})
	}
}

// TestTS2021Route_AcceptsGETAndPOST reproduces a regression where the
// browser/WASM control client could not connect. Tailscale's JS/WASM control
// client opens /ts2021 as a WebSocket, which is an HTTP GET upgrade; the native
// Go client uses an HTTP POST upgrade. The gorilla->chi router migration
// registered /ts2021 for POST only, so the GET WebSocket handshake was rejected
// with 405 Method Not Allowed by the router before it could reach
// NoiseUpgradeHandler. Both methods must route to the handler.
//
// NoiseUpgradeHandler dispatches on the Upgrade header, not the HTTP method, so
// once the route is reachable the handler handles both upgrade styles. The
// httptest recorder is not an http.Hijacker, so the upgrade itself fails past
// the router (501 for the WebSocket path, 400 for the native path) — the point
// is only that neither is 405, i.e. the router no longer rejects GET early.
func TestTS2021Route_AcceptsGETAndPOST(t *testing.T) {
	t.Parallel()

	handler := createTestApp(t).HTTPHandler()

	tests := []struct {
		name    string
		method  string
		headers map[string]string
	}{
		{
			name:   "websocket_get_from_wasm_client",
			method: http.MethodGet,
			headers: map[string]string{
				"Connection":             "Upgrade",
				"Upgrade":                "websocket",
				"Sec-WebSocket-Version":  "13",
				"Sec-WebSocket-Key":      "dGhlIHNhbXBsZSBub25jZQ==",
				"Sec-WebSocket-Protocol": "tailscale-control-protocol",
			},
		},
		{
			name:   "native_post_upgrade",
			method: http.MethodPost,
			headers: map[string]string{
				"Connection":            "upgrade",
				"Upgrade":               "tailscale-control-protocol",
				"X-Tailscale-Handshake": "AAAA",
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			req := httptest.NewRequestWithContext(context.Background(), tt.method,
				"/ts2021?X-Tailscale-Handshake=AAAA", nil)
			for k, v := range tt.headers {
				req.Header.Set(k, v)
			}

			rec := httptest.NewRecorder()
			handler.ServeHTTP(rec, req)

			assert.NotEqual(t, http.StatusMethodNotAllowed, rec.Code,
				"%s /ts2021 must reach NoiseUpgradeHandler, not be rejected by the router with 405",
				tt.method)
		})
	}
}

// newSSHActionFollowUpRequest is like newSSHActionRequest but carries the
// auth_id query parameter that marks a follow-up poll.
func newSSHActionFollowUpRequest(t *testing.T, src, dst types.NodeID, authID types.AuthID) *http.Request {
	t.Helper()

	req := newSSHActionRequest(t, src, dst)

	q := req.URL.Query()
	q.Set("auth_id", authID.String())
	req.URL.RawQuery = q.Encode()

	return req
}

var errSSHCheckRejectedForTest = errors.New("ssh check rejected for test")

// sshVerdictCases are the two verdicts a check session can resolve to.
var sshVerdictCases = []struct {
	name    string
	verdict types.AuthVerdict
	accept  bool
}{
	{name: "accept", verdict: types.AuthVerdict{}, accept: true},
	{name: "reject", verdict: types.AuthVerdict{Err: errSSHCheckRejectedForTest}, accept: false},
}

// sshVerdictFixture is a same-user (src, dst) pair under an SSH check with
// checkPeriod "always". Period 0 never auto-approves from the ledger, so any
// Accept not backed by a verdict is a replay.
type sshVerdictFixture struct {
	ns       *noiseServer
	src, dst types.NodeID
}

func newSSHVerdictFixture(t *testing.T) *sshVerdictFixture {
	t.Helper()

	app := createTestApp(t)
	user := app.state.CreateUserForTest("ssh-verdict-user")
	require.NoError(t, app.state.UpdatePolicyManagerUsersForTest())

	var ids [2]types.NodeID

	for i, name := range []string{"src-node", "dst-node"} {
		node := app.state.CreateRegisteredNodeForTest(user, name)
		// autogroup:self compares hydrated users.
		node.User = user

		// SaveNode refreshes the policy manager's nodes, which
		// SSHCheckParams resolves against.
		_, _, err := app.state.SaveNode(node.View())
		require.NoError(t, err)

		ids[i] = node.ID
	}

	_, err := app.state.SetPolicy(fmt.Appendf(nil, `{
		"ssh": [{
			"action": "check",
			"checkPeriod": "always",
			"src": [%q],
			"dst": ["autogroup:self"],
			"users": ["autogroup:nonroot"]
		}]
	}`, user.Name+"@"))
	require.NoError(t, err)

	period, checkFound := app.state.SSHCheckParams(ids[0], ids[1], sshTestLocalUser)
	require.True(t, checkFound, "test setup: pair must be subject to a check")
	require.Zero(t, period, "test setup: checkPeriod must be always")

	dst, ok := app.state.GetNodeByID(ids[1])
	require.True(t, ok)

	return &sshVerdictFixture{
		ns:  &noiseServer{headscale: app, machineKey: dst.MachineKey()},
		src: ids[0],
		dst: ids[1],
	}
}

// mint runs the initial poll and returns the check session it created.
func (f *sshVerdictFixture) mint(t *testing.T) (types.AuthID, *types.AuthRequest) {
	t.Helper()

	rec := httptest.NewRecorder()
	f.ns.SSHActionHandler(rec, newSSHActionRequest(t, f.src, f.dst))

	authID := requireSSHHold(t, sshActionFromRecorder(t, rec))

	auth, ok := f.ns.headscale.state.GetAuthCacheEntry(authID)
	require.True(t, ok, "minted session must be cached")

	return authID, auth
}

// cancellableFollowUp returns a follow-up request and the cancel for its
// context, derived from the request's own so chi's route values survive.
func (f *sshVerdictFixture) cancellableFollowUp(
	t *testing.T,
	authID types.AuthID,
) (*http.Request, context.CancelFunc) {
	t.Helper()

	req := newSSHActionFollowUpRequest(t, f.src, f.dst, authID)
	ctx, cancel := context.WithCancel(req.Context())

	return req.WithContext(ctx), cancel
}

func (f *sshVerdictFixture) serve(req *http.Request) *httptest.ResponseRecorder {
	rec := httptest.NewRecorder()
	f.ns.SSHActionHandler(rec, req)

	return rec
}

func (f *sshVerdictFixture) followUp(t *testing.T, authID types.AuthID) *httptest.ResponseRecorder {
	t.Helper()

	return f.serve(newSSHActionFollowUpRequest(t, f.src, f.dst, authID))
}

func sshActionFromRecorder(t *testing.T, rec *httptest.ResponseRecorder) tailcfg.SSHAction {
	t.Helper()

	require.Equal(t, http.StatusOK, rec.Code, "body=%s", rec.Body.String())

	var action tailcfg.SSHAction
	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &action))

	return action
}

// carriesSSHVerdict reports whether action is the answer to the verdict.
func carriesSSHVerdict(action tailcfg.SSHAction, accept bool) bool {
	if action.HoldAndDelegate != "" || action.Accept == action.Reject {
		return false
	}

	return action.Accept == accept
}

// requireSSHHold asserts action re-delegates and returns its fresh auth_id.
func requireSSHHold(t *testing.T, action tailcfg.SSHAction) types.AuthID {
	t.Helper()

	require.False(t, action.Accept, "expected HoldAndDelegate, got Accept: %+v", action)
	require.False(t, action.Reject, "expected HoldAndDelegate, got Reject: %+v", action)
	require.NotEmpty(t, action.HoldAndDelegate, "expected HoldAndDelegate: %+v", action)

	u, err := url.Parse(action.HoldAndDelegate)
	require.NoError(t, err)

	authID, err := types.AuthIDFromString(u.Query().Get("auth_id"))
	require.NoError(t, err)

	return authID
}

// TestSSHActionFollowUp_ConsumedVerdictNotReplayed guards the one-shot
// verdict channel: after a follow-up consumed the verdict, a second follow-up
// on the same auth_id must re-decide instead of reading the closed channel's
// zero value, which Accept() reports as success.
func TestSSHActionFollowUp_ConsumedVerdictNotReplayed(t *testing.T) {
	t.Parallel()

	for _, tc := range sshVerdictCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			f := newSSHVerdictFixture(t)
			authID, auth := f.mint(t)
			auth.FinishAuth(tc.verdict)

			first := sshActionFromRecorder(t, f.followUp(t, authID))
			require.True(t, carriesSSHVerdict(first, tc.accept),
				"first follow-up must carry the verdict, got %+v", first)

			second := sshActionFromRecorder(t, f.followUp(t, authID))
			replayID := requireSSHHold(t, second)
			assert.NotEqual(t, authID, replayID, "re-delegation must mint a new session")

			// A replay that recorded auth would feed auto-approval.
			_, recorded := f.ns.headscale.state.GetLastSSHAuth(f.src, f.dst)
			assert.Equal(t, tc.accept, recorded, "only an accepted verdict may record auth")
		})
	}

	// With the check gone there is nothing to re-delegate, but the replay
	// must still not be answered from the consumed verdict.
	for _, tc := range sshVerdictCases {
		t.Run(tc.name+"-check-removed", func(t *testing.T) {
			t.Parallel()

			f := newSSHVerdictFixture(t)
			authID, auth := f.mint(t)
			auth.FinishAuth(tc.verdict)

			first := sshActionFromRecorder(t, f.followUp(t, authID))
			require.True(t, carriesSSHVerdict(first, tc.accept),
				"first follow-up must carry the verdict, got %+v", first)

			_, err := f.ns.headscale.state.SetPolicy([]byte(`{}`))
			require.NoError(t, err)

			_, checkFound := f.ns.headscale.state.SSHCheckParams(f.src, f.dst, sshTestLocalUser)
			require.False(t, checkFound, "test setup: pair must no longer be subject to a check")

			rec := f.followUp(t, authID)
			action := sshActionFromRecorder(t, rec)
			assert.True(t, action.Reject, "replay without a check must be refused")
			assert.False(t, action.Accept, "replay without a check must never approve access")
		})
	}
}

// TestSSHActionFollowUp_ConcurrentWaiters parks two follow-ups on one
// session: exactly one may consume the verdict, the other re-decides.
// FinishAuth can land before either waiter parks and nothing signals the
// park, so the body repeats to exercise the both-parked order.
func TestSSHActionFollowUp_ConcurrentWaiters(t *testing.T) {
	t.Parallel()

	const iterations = 200

	for _, tc := range sshVerdictCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			f := newSSHVerdictFixture(t)

			for range iterations {
				authID, auth := f.mint(t)

				var (
					wg   sync.WaitGroup
					recs [2]*httptest.ResponseRecorder
				)

				for i := range recs {
					wg.Go(func() {
						recs[i] = f.followUp(t, authID)
					})
				}

				auth.FinishAuth(tc.verdict)
				wg.Wait()

				var carried, held int

				for _, rec := range recs {
					action := sshActionFromRecorder(t, rec)
					if carriesSSHVerdict(action, tc.accept) {
						carried++

						continue
					}

					requireSSHHold(t, action)

					held++
				}

				require.Equal(t, 1, carried, "exactly one waiter must carry the verdict")
				require.Equal(t, 1, held, "the other waiter must re-delegate")
			}
		})
	}
}

// TestSSHActionFollowUp_CancelledWaiterLeavesVerdict: a follow-up that
// returns before FinishAuth must not consume the verdict, so the retry gets
// it exactly once.
func TestSSHActionFollowUp_CancelledWaiterLeavesVerdict(t *testing.T) {
	t.Parallel()

	for _, tc := range sshVerdictCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			f := newSSHVerdictFixture(t)
			authID, auth := f.mint(t)

			req1, cancel := f.cancellableFollowUp(t, authID)
			done1 := make(chan *httptest.ResponseRecorder)

			go func() {
				done1 <- f.serve(req1)
			}()

			cancel()

			rec1 := <-done1
			require.Equal(t, http.StatusUnauthorized, rec1.Code,
				"cancelled follow-up must return 401, body=%s", rec1.Body.String())

			// The handler has returned, so its select could only take ctx.Done.
			auth.FinishAuth(tc.verdict)

			second := sshActionFromRecorder(t, f.followUp(t, authID))
			require.True(t, carriesSSHVerdict(second, tc.accept),
				"retry must carry the verdict, got %+v", second)

			third := sshActionFromRecorder(t, f.followUp(t, authID))
			requireSSHHold(t, third)
		})
	}
}

// TestSSHActionFollowUp_CancelRacingVerdictAtMostOnce makes both select cases
// ready before the handler parks. Either outcome is allowed; the verdict
// must reach at most one response.
func TestSSHActionFollowUp_CancelRacingVerdictAtMostOnce(t *testing.T) {
	t.Parallel()

	const iterations = 200

	for _, tc := range sshVerdictCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			f := newSSHVerdictFixture(t)

			for range iterations {
				authID, auth := f.mint(t)

				auth.FinishAuth(tc.verdict)

				req1, cancel := f.cancellableFollowUp(t, authID)
				cancel()

				rec1 := f.serve(req1)
				retry := sshActionFromRecorder(t, f.followUp(t, authID))

				if rec1.Code == http.StatusUnauthorized {
					require.True(t, carriesSSHVerdict(retry, tc.accept),
						"cancelled follow-up left the verdict; retry must carry it, got %+v", retry)

					continue
				}

				first := sshActionFromRecorder(t, rec1)
				require.True(t, carriesSSHVerdict(first, tc.accept),
					"cancelled follow-up consumed the verdict, got %+v", first)
				requireSSHHold(t, retry)
			}
		})
	}
}

// TestSSHActionFollowUp_LostResponseRedecides: the client never saw the
// Accept (dropped response) and retries. The retry must re-decide through a
// fresh session, which then completes normally.
func TestSSHActionFollowUp_LostResponseRedecides(t *testing.T) {
	t.Parallel()

	f := newSSHVerdictFixture(t)
	authID, auth := f.mint(t)
	auth.FinishAuth(types.AuthVerdict{})

	// The Accept response is lost on the way to the client.
	_ = f.followUp(t, authID)

	retry := sshActionFromRecorder(t, f.followUp(t, authID))
	freshID := requireSSHHold(t, retry)
	require.NotEqual(t, authID, freshID)

	fresh, ok := f.ns.headscale.state.GetAuthCacheEntry(freshID)
	require.True(t, ok, "re-delegated session must be cached")
	fresh.FinishAuth(types.AuthVerdict{})

	final := sshActionFromRecorder(t, f.followUp(t, freshID))
	assert.True(t, carriesSSHVerdict(final, true),
		"fresh session must complete with its verdict, got %+v", final)
}

// newMapRequest builds a streaming [tailcfg.MapRequest] POST for
// /machine/map. Version is mandatory: [rejectUnsupported] runs before the
// handler looks the node up, and a zero version is rejected with 400.
func newMapRequest(t *testing.T, req tailcfg.MapRequest) *http.Request {
	t.Helper()

	body, err := json.Marshal(req)
	require.NoError(t, err)

	return httptest.NewRequestWithContext(context.Background(), http.MethodPost, "/machine/map", bytes.NewReader(body))
}

// decodeMapResponse reads a map response frame the way a Tailscale client
// does: a little-endian length prefix followed by a body that is zstd-framed
// whenever the request asked for compression.
func decodeMapResponse(t *testing.T, compress string, body []byte) tailcfg.MapResponse {
	t.Helper()

	require.GreaterOrEqual(t, len(body), reservedResponseHeaderSize, "response too short to carry a length prefix")

	size := binary.LittleEndian.Uint32(body[:reservedResponseHeaderSize])
	payload := body[reservedResponseHeaderSize:]
	require.Len(t, payload, int(size), "length prefix must match the body it precedes")

	if compress == util.ZstdCompression {
		decoded, err := zstdframe.AppendDecode(nil, payload)
		require.NoError(t, err, "client decodes every frame as zstd when it asked for zstd")

		payload = decoded
	}

	var resp tailcfg.MapResponse
	require.NoError(t, json.Unmarshal(payload, &resp))

	return resp
}

// TestPollNetMapHandler_DeletedNodeGetsExpiredSelf verifies that a streaming
// map request for a node that no longer exists is answered with an expired
// self node instead of a bare 404. A Tailscale client treats every non-200 on
// the map path identically and retries forever with loggedIn still set; only a
// self node whose KeyExpiry is in the past moves it to NeedsLogin.
//
// See: https://github.com/juanfont/headscale/issues/3410
func TestPollNetMapHandler_DeletedNodeGetsExpiredSelf(t *testing.T) {
	t.Parallel()

	for _, compress := range []string{"", util.ZstdCompression} {
		t.Run("compress="+compress, func(t *testing.T) {
			t.Parallel()

			app := createTestApp(t)
			user := app.state.CreateUserForTest("deleted-node-user")
			node := putTestNodeInStore(t, app, user, "deleted-node")

			nodeView, ok := app.state.GetNodeByID(node.ID)
			require.True(t, ok)

			_, err := app.state.DeleteNode(nodeView)
			require.NoError(t, err)

			ns := &noiseServer{headscale: app, machineKey: node.MachineKey}

			rec := httptest.NewRecorder()
			ns.PollNetMapHandler(rec, newMapRequest(t, tailcfg.MapRequest{
				Version:  tailcfg.CurrentCapabilityVersion,
				NodeKey:  node.NodeKey,
				Stream:   true,
				Compress: compress,
			}))

			require.Equal(t, http.StatusOK, rec.Code, "body=%q", rec.Body.String())

			resp := decodeMapResponse(t, compress, rec.Body.Bytes())
			require.NotNil(t, resp.Node, "clients reject an initial map response without a node")
			assert.Equal(t, node.NodeKey, resp.Node.Key)
			assert.Equal(t, time.Unix(1, 0).UTC(), resp.Node.KeyExpiry,
				"a fixed ancient KeyExpiry must remain expired despite client clock skew")
			assert.True(t, resp.Node.Expired)
		})
	}
}

// TestPollNetMapHandler_ForeignMachineKeyStillRejected pins that the
// expired-self response is limited to a genuinely unknown node. A known
// NodeKey presented by the wrong machine key is an impostor, and answering it
// with "your key expired" would wipe the real client's persisted node ID.
func TestPollNetMapHandler_ForeignMachineKeyStillRejected(t *testing.T) {
	t.Parallel()

	app := createTestApp(t)
	user := app.state.CreateUserForTest("impostor-user")
	victim := putTestNodeInStore(t, app, user, "victim-node")
	impostor := putTestNodeInStore(t, app, user, "impostor-node")

	ns := &noiseServer{headscale: app, machineKey: impostor.MachineKey}

	rec := httptest.NewRecorder()
	ns.PollNetMapHandler(rec, newMapRequest(t, tailcfg.MapRequest{
		Version: tailcfg.CurrentCapabilityVersion,
		NodeKey: victim.NodeKey,
		Stream:  true,
	}))

	assert.Equal(t, http.StatusNotFound, rec.Code, "body=%q", rec.Body.String())
}