package meshcli

import (
	"context"
	"encoding/json"
	"errors"
	"net"
	"os"
	"os/user"
	"path/filepath"
	"sort"
	"strings"
	"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{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, " ")
}

// **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) })
	go func() { _, _ = cli.Ask(context.Background(), socket, []string{"push"}) }()
	<-started
	done := make(chan cli.Answer, 1)
	go func() {
		a, _ := cli.Ask(context.Background(), socket, []string{"status"})
		done <- a
	}()
	select {
	case a := <-done:
		if !strings.Contains(a.Refused, "busy") {
			t.Fatalf("a second line from the same account reads %+v", a)
		}
	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 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", ""},
		{"", ""},
	} {
		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 := loginSessionIn(string(raw), uint32(os.Getuid())); got.Session != want {
		t.Fatalf("sent session %q, the kernel says %q", got.Session, want)
	}
}