package meshcli

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"net"
	"os"
	"os/user"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"testing"
	"time"

	"git.novox.be/novox/mesh-sdk/go/cli"
)

// serving starts Serve on a socket of the test's own, and stops it when the test ends.
func serving(t *testing.T, forward Forward) string {
	t.Helper()
	socket := filepath.Join(t.TempDir(), "run", "cli.sock")
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() { done <- Serve(ctx, socket, forward, func(string) {}) }()
	t.Cleanup(func() {
		cancel()
		if err := <-done; err != nil {
			t.Errorf("Serve ended with %v", err)
		}
	})
	for i := 0; i < 200; i++ {
		if _, err := os.Stat(socket); err == nil {
			return socket
		}
		time.Sleep(5 * time.Millisecond)
	}
	t.Fatal("the socket never appeared")
	return ""
}

// The account sent is the one the kernel gives for the connecting process, and the answer comes back as it was.
func TestTheAccountAskingIsTheKernelsAndTheAnswerComesBack(t *testing.T) {
	var got Asked
	socket := serving(t, func(_ context.Context, asked Asked) cli.Answer {
		got = asked
		return cli.Answer{Stdout: []byte("done\n"), Exit: 0, Terminal: true, Why: "the terminal"}
	})
	a, err := cli.Ask(context.Background(), socket, []string{"settings", "show", "zsh"})
	if err != nil {
		t.Fatal(err)
	}
	if string(a.Stdout) != "done\n" || !a.Terminal || a.Refused != "" {
		t.Fatalf("the answer came back as %+v", a)
	}
	me, err := user.Current()
	if err != nil {
		t.Skipf("this machine cannot name the test's account: %v", err)
	}
	if int(got.UID) != os.Getuid() || got.Account != me.Username {
		t.Fatalf("asked as %d %q, and the kernel says %d %q", got.UID, got.Account, os.Getuid(), me.Username)
	}
	if strings.Join(got.Line, " ") != "settings show zsh" {
		t.Fatalf("the line was sent as %q", got.Line)
	}
	if info, err := os.Stat(socket); err != nil || info.Mode().Perm() != 0o666 {
		t.Fatalf("the socket is not open to every account: %v %v", info.Mode(), err)
	}
}

// Credentials the kernel did not give are no account: refused, and nothing is asked.
func TestAConnectionWhoseAccountCannotBeReadIsNeverAskedAsAnyone(t *testing.T) {
	before := peerOf
	peerOf = func(*net.UnixConn) (uint32, int32, error) { return 0, 0, errors.New("no credentials") }
	t.Cleanup(func() { peerOf = before })
	asked := false
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		asked = true
		return cli.Answer{}
	})
	a, err := cli.Ask(context.Background(), socket, []string{"status"})
	if err != nil {
		t.Fatal(err)
	}
	if asked || a.Refused == "" || a.Exit == 0 {
		t.Fatalf("a connection with no account was asked (%v) or not refused: %+v", asked, a)
	}
}

// A request over the bound is refused and never asked.
func TestARequestOverTheBoundIsRefused(t *testing.T) {
	asked := false
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		asked = true
		return cli.Answer{}
	})
	a, err := cli.Ask(context.Background(), socket, []string{strings.Repeat("x", cli.MaxRequest)})
	if err != nil {
		t.Fatal(err)
	}
	if asked || a.Refused == "" {
		t.Fatalf("a request over the bound was asked (%v): %+v", asked, a)
	}
}

// A file at the socket's path that is not a socket is never removed.
func TestAFileThatIsNotASocketIsKept(t *testing.T) {
	dir := t.TempDir()
	socket := filepath.Join(dir, "cli.sock")
	if err := os.WriteFile(socket, []byte("mine"), 0o644); err != nil {
		t.Fatal(err)
	}
	err := Serve(context.Background(), socket, nil, nil)
	if err == nil || !strings.Contains(err.Error(), "not a socket") {
		t.Fatalf("a file at the socket's path was not refused: %v", err)
	}
	if body, _ := os.ReadFile(socket); string(body) != "mine" {
		t.Fatal("the file at the socket's path was touched")
	}
}

// The request the controller reads holds these field names; the controller's side holds the same list
// (mesh-controller, the mesh-cli request's test).
func TestTheRequestToTheControllerKeepsItsFieldNames(t *testing.T) {
	body, err := json.Marshal(Asked{Line: []string{"status"}, Account: "a", UID: 1})
	if err != nil {
		t.Fatal(err)
	}
	body, _ = json.Marshal(Asked{Line: []string{"status"}, Account: "a", UID: 1, Session: "session-3.scope"})
	if got := keysOf(t, body); got != "account line session uid" {
		t.Fatalf("the request's fields are %q", got)
	}
	body, _ = json.Marshal(Asked{Line: []string{"status"}, Account: "a", UID: 1})
	if got := keysOf(t, body); got != "account line uid" {
		t.Fatalf("the request's fields are %q", got)
	}
	body, _ = json.Marshal(Asked{Line: []string{"secret"}, Account: "a", UID: 1, Stdin: []byte("x")})
	if got := keysOf(t, body); got != "account line stdin uid" {
		t.Fatalf("a request with standard input has the fields %q", got)
	}
	body, _ = json.Marshal(Asked{Follow: "call-1", Account: "a", UID: 1})
	if got := keysOf(t, body); got != "account follow uid" {
		t.Fatalf("a follow's fields are %q", got)
	}
	// What the controller answers as a line's result, and as a running line's: the same names its side holds.
	body, err = json.Marshal(cli.Answer{Stdout: []byte("o"), Stderr: []byte("e"), Exit: 1, Terminal: true, Why: "w",
		Refused: "r", Cut: true})
	if err != nil {
		t.Fatal(err)
	}
	if got := keysOf(t, body); got != "cut exit refused stderr stdout terminal why" {
		t.Fatalf("the answer's fields are %q", got)
	}
	body, _ = json.Marshal(runningResult{Running: true, Call: "call-1"})
	if got := keysOf(t, body); got != "call running" {
		t.Fatalf("a running answer's fields are %q", got)
	}
}

func keysOf(t *testing.T, body []byte) string {
	t.Helper()
	var m map[string]any
	if err := json.Unmarshal(body, &m); err != nil {
		t.Fatal(err)
	}
	var keys []string
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return strings.Join(keys, " ")
}

// holdALine asks one line and returns once the engine is asking it, so it holds its account's slot. A first line
// that ends or never arrives fails the test at once, with what came of it, instead of hanging the suite (novox/hq
// issue 434).
func holdALine(t *testing.T, socket string, started <-chan struct{}) {
	t.Helper()
	first := make(chan error, 1)
	go func() {
		_, err := cli.Ask(context.Background(), socket, []string{"push"})
		first <- err
	}()
	select {
	case <-started:
	case err := <-first:
		t.Fatalf("the first line ended before it was asked: %v", err)
	case <-time.After(5 * time.Second):
		t.Fatal("the first line was never asked")
	}
}

// **One account cannot hold the socket** (review of ADR 0272): its lines beyond its own bound are answered busy at
// once, nothing is asked, and the engine goes on accepting.
func TestOneAccountsLinesBeyondItsBoundAreAnsweredBusy(t *testing.T) {
	was := perAccount
	perAccount = 1
	t.Cleanup(func() { perAccount = was })
	release := make(chan struct{})
	started := make(chan struct{}, 2)
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		started <- struct{}{}
		<-release
		return cli.Answer{}
	})
	// Released before the engine is stopped: cleanups run last first, and the engine waits for its lines.
	t.Cleanup(func() { close(release) })
	holdALine(t, socket, started)
	type asked struct {
		a   cli.Answer
		err error
	}
	done := make(chan asked, 1)
	go func() {
		a, err := cli.Ask(context.Background(), socket, []string{"status"})
		done <- asked{a, err}
	}()
	select {
	case got := <-done:
		// An error is a busy line the client never read (novox/hq issue 434), not an answer.
		if got.err != nil || !strings.Contains(got.a.Refused, "busy") {
			t.Fatalf("a second line from the same account reads %+v (%v)", got.a, got.err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("a second line from the same account waited instead of being answered busy")
	}
	if len(started) != 0 {
		t.Fatal("the busy line was asked")
	}
}

// **A refusal waits for the request it answers** (novox/hq issue 434): the client writes its line first and reads
// the answer after. An engine that answered busy and closed before that write landed broke the client's write, and
// the refusal was never read — under the whole suite's load the busy line read as an error. Here the client
// connects and holds its line back: no answer may come before the line, and the line, once written, is answered
// busy. Ordered by the client's own write, so it holds however slow the machine is.
func TestARefusalWaitsForTheRequestItAnswers(t *testing.T) {
	was, wasWithin := perAccount, refusedWithin
	perAccount, refusedWithin = 1, time.Minute
	t.Cleanup(func() { perAccount, refusedWithin = was, wasWithin })
	release := make(chan struct{})
	started := make(chan struct{}, 2)
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		started <- struct{}{}
		<-release
		return cli.Answer{}
	})
	t.Cleanup(func() { close(release) })
	holdALine(t, socket, started)
	conn, err := net.Dial("unix", socket)
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()
	// Nothing is written yet: an engine that answers now answers before the request. The wait is far inside
	// refusedWithin, so an engine that waits is still waiting when it ends.
	_ = conn.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
	var b [1]byte
	if n, err := conn.Read(b[:]); n > 0 || !errors.Is(err, os.ErrDeadlineExceeded) {
		t.Fatalf("the engine answered before the request was written (%d bytes, %v)", n, err)
	}
	_ = conn.SetDeadline(time.Now().Add(5 * time.Second))
	if err := cli.WriteRequest(conn, cli.Request{Line: []string{"status"}}); err != nil {
		t.Fatalf("the request could not be written: %v", err)
	}
	a, err := cli.ReadAnswer(conn)
	if err != nil || !strings.Contains(a.Refused, "busy") {
		t.Fatalf("a line written after the engine chose busy reads %+v (%v)", a, err)
	}
	if len(started) != 0 {
		t.Fatal("the busy line was asked")
	}
}

// **Refusals that wait are bounded** (novox/hq issue 434, review of ADR 0272): with refusalsWaiting already full, a
// further refused line is answered at once, without waiting for its request.
func TestARefusalOverTheWaitingBoundIsAnsweredAtOnce(t *testing.T) {
	was, wasWithin, wasWaiting := perAccount, refusedWithin, refusalsWaiting
	perAccount, refusedWithin = 1, time.Minute
	refusalsWaiting = make(chan struct{}, 1)
	refusalsWaiting <- struct{}{}
	t.Cleanup(func() { perAccount, refusedWithin, refusalsWaiting = was, wasWithin, wasWaiting })
	release := make(chan struct{})
	started := make(chan struct{}, 2)
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		started <- struct{}{}
		<-release
		return cli.Answer{}
	})
	t.Cleanup(func() { close(release) })
	holdALine(t, socket, started)
	conn, err := net.Dial("unix", socket)
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()
	// Nothing is written: a refusal that waited would wait refusedWithin, a minute, for it.
	_ = conn.SetDeadline(time.Now().Add(5 * time.Second))
	a, err := cli.ReadAnswer(conn)
	if err != nil || !strings.Contains(a.Refused, "busy") {
		t.Fatalf("a refusal over the waiting bound reads %+v (%v)", a, err)
	}
}

// countingReader is an endless request with no line end, counting what was read of it.
type countingReader struct{ read int }

func (c *countingReader) Read(p []byte) (int, error) {
	for i := range p {
		p[i] = 'x'
	}
	c.read += len(p)
	return len(p), nil
}

// **A refused request is drained, not kept** (novox/hq issue 434): what a refused client writes is read up to
// drainCap bytes and no further, however much it sends.
func TestARefusedRequestIsDrainedNoFurtherThanItsCap(t *testing.T) {
	r := &countingReader{}
	drain(r)
	if r.read != drainCap {
		t.Fatalf("drained %d bytes of an endless request; the cap is %d", r.read, drainCap)
	}
	after := &countingReader{}
	drain(io.MultiReader(strings.NewReader("{\"line\":[\"status\"]}\n"), after))
	if after.read != 0 {
		t.Fatalf("draining read %d bytes past the end of the request line", after.read)
	}
}

// **A process in another namespace is not this machine's account** (review of ADR 0272): a container running with
// the operator's user id shares the id and not the machine; refused, and nothing is asked.
func TestAPeerInAnotherNamespaceIsRefused(t *testing.T) {
	before := sameNamespaces
	sameNamespaces = func(pid int32) error { return errors.New("its mount namespace is not the engine's") }
	t.Cleanup(func() { sameNamespaces = before })
	asked := false
	socket := serving(t, func(context.Context, Asked) cli.Answer {
		asked = true
		return cli.Answer{}
	})
	a, err := cli.Ask(context.Background(), socket, []string{"status"})
	if err != nil {
		t.Fatal(err)
	}
	if asked || !strings.Contains(a.Refused, "namespace") {
		t.Fatalf("a peer in another namespace was asked (%v): %+v", asked, a)
	}
}

// **The session a line comes from is the kernel's word, and only a login session counts** (review of ADR 0272): a
// service running as the operator — the tool runner, a user unit — is not a person at a terminal. The engine reads
// the peer's cgroup and sends the login session's scope, or nothing; the controller makes no other terminal.
func TestTheLoginSessionAskingIsReadFromTheKernel(t *testing.T) {
	for _, c := range []struct{ cgroup, session string }{
		{"0::/user.slice/user-1000.slice/session-3.scope\n", "session-3.scope"},
		{"0::/user.slice/user-1000.slice/session-c1.scope\n", "session-c1.scope"},
		{"0::/user.slice/user-1000.slice/user@1000.service/app.slice/tmux.scope\n", ""},
		{"0::/system.slice/node-tools.service\n", ""},
		{"0::/user.slice/user-1001.slice/session-3.scope\n", ""}, // another account's session
		{"12:pids:/user.slice\n0::/user.slice/user-1000.slice/session-9.scope/sub\n", ""},
		// Below a session scope, in a scope of its own: only the check that the scope is the account slice's direct
		// child refuses it.
		{"0::/user.slice/user-1000.slice/session-9.scope/x.scope\n", ""},
		{"", ""},
	} {
		if got := loginSessionIn(c.cgroup, 1000); got != c.session {
			t.Errorf("%q read as %q, want %q", c.cgroup, got, c.session)
		}
	}
	// And it is sent: the test process's own, whatever it is, as the kernel says it.
	var got Asked
	socket := serving(t, func(_ context.Context, asked Asked) cli.Answer {
		got = asked
		return cli.Answer{}
	})
	if _, err := cli.Ask(context.Background(), socket, []string{"status"}); err != nil {
		t.Fatal(err)
	}
	raw, _ := os.ReadFile("/proc/self/cgroup")
	if want := userSessionIn(string(raw), uint32(os.Getuid())); got.Session != want {
		t.Fatalf("sent session %q, the kernel says %q", got.Session, want)
	}
}

// **A login session is a person's: systemd's own record says so** (review of ADR 0272): the scope the cgroup names
// must be a session logind keeps for this very account, of class `user` — not a greeter's, not the user manager's,
// not one whose record names another account — and read at accept, with the namespaces, before anything else.
func TestALoginSessionIsAUsersByItsOwnRecord(t *testing.T) {
	dir := t.TempDir()
	was := sessionsDir
	sessionsDir = dir
	t.Cleanup(func() { sessionsDir = was })
	write := func(id, body string) {
		if err := os.WriteFile(filepath.Join(dir, id), []byte(body), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	write("9", "UID=1000\nUSER=op\nCLASS=user\nSCOPE=session-9.scope\nACTIVE=1\n")
	write("3", "UID=1000\nCLASS=greeter\nSCOPE=session-3.scope\n")
	write("5", "UID=1000\nCLASS=user\nSCOPE=session-6.scope\n")
	// The account the record names is not the slice's: only the record's UID check refuses it.
	write("8", "UID=1001\nCLASS=user\nSCOPE=session-8.scope\n")
	// A name with a dot, held as a record that would pass: only the check of the id's characters refuses it.
	write("a.b", "UID=1000\nCLASS=user\nSCOPE=session-a.b.scope\n")
	// A key said twice: the first is the record's word (systemd writes each once); a later one is not read.
	write("11", "UID=1001\nCLASS=user\nSCOPE=session-11.scope\nUID=1000\n")
	write("12", "UID=1000\nCLASS=user\nSCOPE=session-12.scope\nCLASS=greeter\nUID=1001\n")
	for _, c := range []struct {
		cgroup  string
		uid     uint32
		session string
	}{
		{"0::/user.slice/user-1000.slice/session-9.scope\n", 1000, "session-9.scope"},
		{"0::/user.slice/user-1000.slice/x.scope\n", 1000, ""},
		{"0::/user.slice/user-1000.slice/session-9.scope\n", 1001, ""}, // asked as another uid than the slice's
		{"0::/user.slice/user-1000.slice/session-8.scope\n", 1000, ""}, // the record names uid 1001
		{"0::/user.slice/user-1000.slice/session-3.scope\n", 1000, ""}, // a greeter's
		{"0::/user.slice/user-1000.slice/session-5.scope\n", 1000, ""}, // a record naming another scope
		{"0::/user.slice/user-1000.slice/session-7.scope\n", 1000, ""}, // no record at all
		{"0::/user.slice/user-1000.slice/session-a.b.scope\n", 1000, ""},
		{"0::/user.slice/user-1000.slice/session-...scope\n", 1000, ""},
		{"0::/user.slice/user-1000.slice/session-11.scope\n", 1000, ""},                 // first UID is 1001
		{"0::/user.slice/user-1000.slice/session-12.scope\n", 1000, "session-12.scope"}, // first UID and CLASS stand
	} {
		if got := userSessionIn(c.cgroup, c.uid); got != c.session {
			t.Errorf("%q as uid %d read as %q, want %q", c.cgroup, c.uid, got, c.session)
		}
	}
}

// **The session is read at accept, with the namespaces, before the line** (review of ADR 0272): the peer is judged as
// it was when it connected. The client sends its line only once the session has been read; were the session read
// after the line — in the forward, say — the line would never be sent and the test fails.
func TestTheSessionIsReadBeforeTheLine(t *testing.T) {
	var mu sync.Mutex
	var order []string
	note := func(s string) { mu.Lock(); order = append(order, s); mu.Unlock() }
	read := make(chan struct{}, 1)
	beforeNS, beforeSession := sameNamespaces, sessionOf
	sameNamespaces = func(int32) error { note("namespaces"); return nil }
	sessionOf = func(int32, uint32) string { note("session"); read <- struct{}{}; return "session-1.scope" }
	t.Cleanup(func() { sameNamespaces, sessionOf = beforeNS, beforeSession })
	var got Asked
	socket := serving(t, func(_ context.Context, asked Asked) cli.Answer {
		note("forward")
		got = asked
		return cli.Answer{}
	})
	conn, err := net.Dial("unix", socket)
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()
	select {
	case <-read:
	case <-time.After(3 * time.Second):
		t.Fatal("the session was not read before the line was sent")
	}
	note("line sent")
	if err := cli.WriteRequest(conn, cli.Request{Line: []string{"status"}}); err != nil {
		t.Fatal(err)
	}
	_ = conn.SetDeadline(time.Now().Add(5 * time.Second))
	if _, err := cli.ReadAnswer(conn); err != nil {
		t.Fatal(err)
	}
	mu.Lock()
	defer mu.Unlock()
	if strings.Join(order, ",") != "namespaces,session,line sent,forward" || got.Session != "session-1.scope" {
		t.Fatalf("read in the order %v, sent %q", order, got.Session)
	}
}

// mesh-cli's standard input reaches the controller with its line, whole, and only with the line: a follow of the
// same call carries none, and the engine says it nowhere (novox/hq ADR 0259 §10, ADR 0272).
func TestStandardInputGoesToTheControllerWithTheLineAndNowhereElse(t *testing.T) {
	secret := []byte("123456789:the-bot-token-given-at-the-terminal\n")
	var said []string
	var mu sync.Mutex
	var asked [][]byte
	ask := func(_ context.Context, body []byte) ([]byte, error) {
		mu.Lock()
		defer mu.Unlock()
		asked = append(asked, append([]byte(nil), body...))
		if len(asked) == 1 {
			return []byte(`{"result":{"running":true,"call":"call-7"}}`), nil
		}
		return []byte(`{"result":{"exit":0,"terminal":true}}`), nil
	}
	was := followEvery
	followEvery = time.Millisecond
	t.Cleanup(func() { followEvery = was })
	socket := filepath.Join(t.TempDir(), "run", "cli.sock")
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan error, 1)
	go func() {
		done <- Serve(ctx, socket, func(ctx context.Context, a Asked) cli.Answer { return AskTheController(ctx, ask, a) },
			func(s string) { mu.Lock(); said = append(said, s); mu.Unlock() })
	}()
	defer func() { cancel(); <-done }()
	for i := 0; i < 200; i++ {
		if _, err := os.Stat(socket); err == nil {
			break
		}
		time.Sleep(5 * time.Millisecond)
	}
	a, err := cli.AskWith(context.Background(), socket, cli.Request{Line: []string{"secret", "accept", "anchor",
		"telegram", "telegram-token", "--from", "-"}, Stdin: secret})
	if err != nil || a.Exit != 0 {
		t.Fatalf("%v %+v", err, a)
	}
	mu.Lock()
	defer mu.Unlock()
	if len(asked) != 2 {
		t.Fatalf("asked %d times, want the line and one follow", len(asked))
	}
	var first, follow Asked
	_ = json.Unmarshal(asked[0], &first)
	_ = json.Unmarshal(asked[1], &follow)
	if string(first.Stdin) != string(secret) {
		t.Fatalf("the controller was not given the standard input whole: %q", first.Stdin)
	}
	if len(follow.Stdin) != 0 || strings.Contains(string(asked[1]), "stdin") {
		t.Fatalf("a follow carried the standard input again: %s", asked[1])
	}
	for _, s := range said {
		if strings.Contains(s, "bot-token") {
			t.Fatalf("the engine said the standard input: %s", s)
		}
	}
}