// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

//go:build !windows && !plan9

package process

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"syscall"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

// processAlive reports whether pid refers to a still-running process. Signal 0
// performs error checking without delivering a signal: a nil error (or EPERM)
// means the process exists, ESRCH means it is gone.
//
// On Linux, zombie processes (state Z in /proc/<pid>/stat) appear alive to
// kill(0) but have already terminated — their corpse lingers until the parent
// calls wait(). In a Docker container the child may be reparented to a PID 1
// that does not reap promptly, so we treat zombies as not alive.
func processAlive(pid int) bool {
	err := syscall.Kill(pid, 0)
	if err != nil {
		return false
	}
	// On Linux /proc is available; check whether the process is a zombie.
	if b, readErr := os.ReadFile(fmt.Sprintf("/proc/%d/stat", pid)); readErr == nil {
		// Format: "pid (comm) state ..." — state follows the closing ')' of the
		// command name (which may itself contain spaces and parens).
		if _, after, found := strings.CutLast(string(b), ") "); found {
			fields := strings.Fields(after)
			if len(fields) > 0 && fields[0] == "Z" {
				return false // zombie: terminated but not yet reaped
			}
		}
	}
	return true
}

func TestKillerKillsTree(t *testing.T) {
	cmd, ready := newTestProcess(t, "parent", false)
	require.NoError(t, cmd.Start())
	t.Cleanup(func() {
		_ = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
		_ = cmd.Wait()
	})

	killer, err := NewKiller(cmd.Process)
	require.NoError(t, err)
	defer killer.Close()

	childPID := ready()
	require.True(t, processAlive(childPID), "child process should start")

	require.NoError(t, killer.Kill())
	_ = cmd.Wait()

	require.Eventually(t, func() bool {
		return !processAlive(childPID)
	}, 20*time.Second, 100*time.Millisecond, "backgrounded child should be terminated")
}

func TestTreeKillCancelBeforeCaptureKillsTree(t *testing.T) {
	stdin, input, err := os.Pipe()
	require.NoError(t, err)
	t.Cleanup(func() { _ = stdin.Close() })
	t.Cleanup(func() { _ = input.Close() })
	cmd := exec.CommandContext(t.Context(), "/bin/sh", "-c", "exec 3<&0; cat <&3 & echo $!; read value")
	cmd.Stdin = stdin
	cmd.SysProcAttr = SysProcAttr("", false)
	output, err := cmd.StdoutPipe()
	require.NoError(t, err)
	treeKill := NewTreeKill(cmd)
	require.NoError(t, cmd.Start())
	t.Cleanup(func() {
		_ = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
		_ = cmd.Wait()
	})
	var childPID int
	_, err = fmt.Fscan(output, &childPID)
	require.NoError(t, err)
	require.True(t, processAlive(childPID))

	require.NoError(t, cmd.Cancel())
	killer, err := treeKill.Capture(cmd.Process)
	require.NoError(t, err)
	defer killer.Close()
	require.Error(t, cmd.Wait())
	require.Eventually(t, func() bool { return !processAlive(childPID) }, 5*time.Second, 10*time.Millisecond)
}

func TestTreeKillCancelRunsInterruptTrap(t *testing.T) {
	ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
	defer cancel()
	marker := filepath.Join(t.TempDir(), "interrupted")
	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", `trap 'echo interrupted > "$1"; exit 0' INT; echo ready; read value`, "sh", marker)
	cmd.SysProcAttr = SysProcAttr("", false)
	input, err := cmd.StdinPipe()
	require.NoError(t, err)
	defer input.Close()
	output, err := cmd.StdoutPipe()
	require.NoError(t, err)
	treeKill := NewTreeKill(cmd)
	treeKill.GracefulCancel = true
	require.NoError(t, cmd.Start())
	killer, err := treeKill.Capture(cmd.Process)
	require.NoError(t, err)
	defer killer.Close()
	t.Cleanup(func() {
		_ = killer.Kill()
		_ = cmd.Wait()
	})
	var ready string
	_, err = fmt.Fscanln(output, &ready)
	require.NoError(t, err)
	require.Equal(t, "ready", ready)

	cancel()
	require.ErrorIs(t, treeKill.Wait(ctx, cmd), context.Canceled)
	require.FileExists(t, marker)
}