package main

import (
	"bytes"
	"os"
	"os/exec"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"testing"
	"time"

	"golang.org/x/sys/unix"
)

// openPty opens a new pseudo terminal and returns the master and slave side.
func openPty(t *testing.T) (*os.File, *os.File) {
	t.Helper()
	master, err := os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
	if err != nil {
		t.Skipf("no pty available: %v", err)
	}
	if err := unix.IoctlSetPointerInt(int(master.Fd()), unix.TIOCSPTLCK, 0); err != nil {
		t.Fatal(err)
	}
	n, err := unix.IoctlGetInt(int(master.Fd()), unix.TIOCGPTN)
	if err != nil {
		t.Fatal(err)
	}
	slave, err := os.OpenFile("/dev/pts/"+strconv.Itoa(n), os.O_RDWR|syscall.O_NOCTTY, 0)
	if err != nil {
		t.Fatal(err)
	}
	return master, slave
}

// ptyShell is the shell running on a pseudo terminal.
type ptyShell struct {
	t      *testing.T
	master *os.File
	mu     sync.Mutex
	out    bytes.Buffer
	cmd    *exec.Cmd
}

func startPtyShell(t *testing.T) *ptyShell {
	bin := buildShell(t)
	master, slave := openPty(t)
	cmd := exec.Command(bin, "--norc")
	cmd.Stdin, cmd.Stdout, cmd.Stderr = slave, slave, slave
	cmd.Env = append(os.Environ(), "NO_COLOR=1")
	// New session with the pty as controlling terminal, like a terminal
	// emulator does
	cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true, Setctty: true, Ctty: 0}
	if err := cmd.Start(); err != nil {
		t.Fatal(err)
	}
	slave.Close()

	s := &ptyShell{t: t, master: master, cmd: cmd}
	go func() {
		buf := make([]byte, 4096)
		for {
			n, err := master.Read(buf)
			s.mu.Lock()
			s.out.Write(buf[:n])
			s.mu.Unlock()
			if err != nil {
				return
			}
		}
	}()
	t.Cleanup(func() {
		cmd.Process.Kill()
		cmd.Wait()
		master.Close()
	})
	s.expect("$ ")
	return s
}

func (s *ptyShell) send(text string) {
	s.master.WriteString(text)
}

// expect waits until want appears in the output after the position of the
// last match and consumes the output up to it.
func (s *ptyShell) expect(want string) {
	s.t.Helper()
	deadline := time.Now().Add(5 * time.Second)
	for time.Now().Before(deadline) {
		s.mu.Lock()
		out := s.out.String()
		if i := strings.Index(out, want); i >= 0 {
			s.out.Next(i + len(want))
			s.mu.Unlock()
			return
		}
		s.mu.Unlock()
		time.Sleep(20 * time.Millisecond)
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	s.t.Fatalf("timeout waiting for %q, output:\n%s", want, s.out.String())
}

func TestWaitFlags_NoWCONTINUED(t *testing.T) {
	defer func(saved bool) { jobControl = saved }(jobControl)
	jobControl = true
	j := &job{pgid: 1}
	for _, nohang := range []bool{false, true} {
		flags := waitFlags(j, nohang)
		if flags&syscall.WCONTINUED != 0 {
			t.Errorf("waitFlags(nohang=%v) contains WCONTINUED, which Go decodes wrongly on BSD", nohang)
		}
		if flags&syscall.WUNTRACED == 0 {
			t.Errorf("waitFlags(nohang=%v) misses WUNTRACED", nohang)
		}
	}
}

func TestJobControl(t *testing.T) {
	s := startPtyShell(t)

	// Ctrl+Z stops the foreground job, the shell gets the terminal back
	s.send("sleep 30\n")
	time.Sleep(300 * time.Millisecond)
	s.send("\x1a")
	s.expect("[1]+  Stopped                 sleep 30")
	s.send("jobs\n")
	s.expect("[1]+  Stopped                 sleep 30")

	// bg continues it in the background
	s.send("bg\n")
	s.expect("[1]+  Running                 sleep 30 &")

	// After bg the job keeps running and is not reported as finished
	// (regression: on FreeBSD the "continued" status was read as killed by
	// SIGCONT, "Exit 147")
	time.Sleep(300 * time.Millisecond)
	s.send("jobs\n")
	s.expect("[1]+  Running                 sleep 30 &")

	// fg brings it back, Ctrl+C reaches only the job
	s.send("fg %1\n")
	s.expect("sleep 30")
	time.Sleep(300 * time.Millisecond)
	s.send("\x03")
	s.send("echo status=$?\n")
	s.expect("status=130")

	// A pipeline is stopped and continued as a whole
	s.send("sleep 30 | cat\n")
	time.Sleep(300 * time.Millisecond)
	s.send("\x1a")
	s.expect("Stopped                 sleep 30 | cat")
	s.send("fg\n")
	time.Sleep(300 * time.Millisecond)
	s.send("\x03")
	s.send("echo pipeline=$?\n")
	s.expect("pipeline=130")

	// A background job that reads from the terminal is stopped (SIGTTIN),
	// in the foreground it gets the input
	s.send("cat &\n")
	s.expect("[1] ")
	time.Sleep(300 * time.Millisecond)
	s.send("echo next\n")
	s.expect("[1]+  Stopped                 cat")
	s.send("fg\n")
	time.Sleep(300 * time.Millisecond)
	s.send("hello cat\n")
	s.expect("hello cat\r\nhello cat")
	s.send("\x04")
	s.send("echo cat=$?\n")
	s.expect("cat=0")

	// Finished background jobs are reported before the next prompt
	s.send("sleep 0.2 &\n")
	time.Sleep(500 * time.Millisecond)
	s.send("echo tick\n")
	s.expect("Done                    sleep 0.2")

	// exit warns about stopped jobs once
	s.send("sleep 30\n")
	time.Sleep(300 * time.Millisecond)
	s.send("\x1a")
	s.expect("Stopped")
	s.send("exit\n")
	s.expect("there are stopped jobs")
	s.send("exit 0\n")

	done := make(chan error, 1)
	go func() { done <- s.cmd.Wait() }()
	select {
	case err := <-done:
		if err != nil {
			t.Errorf("shell exited with %v", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("shell did not exit")
	}
}