// +build linux darwin

package envoy

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"testing"
	"time"

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

func TestExecEnvoy(t *testing.T) {
	require := require.New(t)

	cmd, destroy := helperProcess("exec-fake-envoy")
	defer destroy()

	cmd.Stderr = os.Stderr
	outBytes, err := cmd.Output()
	if err != nil {
		t.Fatalf("error launching child process: %v", err)
	}

	var got FakeEnvoyExecData
	require.NoError(json.Unmarshal(outBytes, &got))

	expectArgs := []string{
		"--v2-config-only",
		"--disable-hot-restart",
		"--config-path",
		"/dev/fd/3",
		"--fake-envoy-arg",
	}
	expectConfigPath := "/dev/fd/3"
	expectConfigData := fakeEnvoyTestData

	require.Equal(expectArgs, got.Args)
	require.Equal(expectConfigPath, got.ConfigPath)
	require.Equal(expectConfigData, got.ConfigData)
}

type FakeEnvoyExecData struct {
	Args       []string `json:"args"`
	ConfigPath string   `json:"configPath"`
	ConfigData string   `json:"configData"`
}

// helperProcessSentinel is a sentinel value that is put as the first
// argument following "--" and is used to determine if TestHelperProcess
// should run.
const helperProcessSentinel = "GO_WANT_HELPER_PROCESS"

// helperProcess returns an *exec.Cmd that can be used to execute the
// TestHelperProcess function below. This can be used to test multi-process
// interactions.
func helperProcess(s ...string) (*exec.Cmd, func()) {
	cs := []string{"-test.run=TestHelperProcess", "--", helperProcessSentinel}
	cs = append(cs, s...)

	cmd := exec.Command(os.Args[0], cs...)
	destroy := func() {
		if p := cmd.Process; p != nil {
			p.Kill()
		}
	}

	return cmd, destroy
}

const fakeEnvoyTestData = "pahx9eiPoogheb4haeb2abeem1QuireWahtah1Udi5ae4fuD0c"

// This is not a real test. This is just a helper process kicked off by tests
// using the helperProcess helper function.
func TestHelperProcess(t *testing.T) {
	args := os.Args
	for len(args) > 0 {
		if args[0] == "--" {
			args = args[1:]
			break
		}

		args = args[1:]
	}

	if len(args) == 0 || args[0] != helperProcessSentinel {
		return
	}

	defer os.Exit(0)
	args = args[1:] // strip sentinel value
	cmd, args := args[0], args[1:]

	switch cmd {
	case "exec-fake-envoy":
		// this will just exec the "fake-envoy" flavor below

		limitProcessLifetime(2 * time.Minute)

		err := execEnvoy(
			os.Args[0],
			[]string{
				"-test.run=TestHelperProcess",
				"--",
				helperProcessSentinel,
				"fake-envoy",
			},
			[]string{"--fake-envoy-arg"},
			[]byte(fakeEnvoyTestData),
		)
		if err != nil {
			fmt.Fprintf(os.Stderr, "fake envoy process failed to exec: %v\n", err)
			os.Exit(1)
		}

	case "fake-envoy":
		// This subcommand is instrumented to verify some settings
		// survived an exec.

		limitProcessLifetime(2 * time.Minute)

		data := FakeEnvoyExecData{
			Args: args,
		}

		// Dump all of the args.
		var captureNext bool
		for _, arg := range args {
			if arg == "--config-path" {
				captureNext = true
			} else if captureNext {
				data.ConfigPath = arg
				captureNext = false
			}
		}

		if data.ConfigPath == "" {
			fmt.Fprintf(os.Stderr, "did not detect a --config-path argument passed through\n")
			os.Exit(1)
		}

		d, err := ioutil.ReadFile(data.ConfigPath)
		if err != nil {
			fmt.Fprintf(os.Stderr, "could not read provided --config-path file %q: %v\n", data.ConfigPath, err)
			os.Exit(1)
		}
		data.ConfigData = string(d)

		enc := json.NewEncoder(os.Stdout)
		if err := enc.Encode(&data); err != nil {
			fmt.Fprintf(os.Stderr, "could not dump results to stdout: %v", err)
			os.Exit(1)

		}

	default:
		fmt.Fprintf(os.Stderr, "Unknown command: %q\n", cmd)
		os.Exit(2)
	}
}

// limitProcessLifetime installs a background goroutine that self-exits after
// the specified duration elapses to prevent leaking processes from tests that
// may spawn them.
func limitProcessLifetime(dur time.Duration) {
	go time.AfterFunc(dur, func() {
		os.Exit(99)
	})
}