// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package testenv

import (
	"os"
	"os/exec"
	"runtime"
	"strings"
	"sync"
	"testing"
)

// HasExec reports whether the current system can start new processes
// using os.StartProcess or (more commonly) exec.Command.
func HasExec() bool {
	switch runtime.GOOS {
	case "js", "ios":
		return false
	}
	return true
}

// MustHaveExec checks that the current system can start new processes
// using os.StartProcess or (more commonly) exec.Command.
// If not, MustHaveExec calls t.Skip with an explanation.
func MustHaveExec(t testing.TB) {
	if !HasExec() {
		t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
}

var execPaths sync.Map // path -> error

// MustHaveExecPath checks that the current system can start the named executable
// using os.StartProcess or (more commonly) exec.Command.
// If not, MustHaveExecPath calls t.Skip with an explanation.
func MustHaveExecPath(t testing.TB, path string) {
	MustHaveExec(t)

	err, found := execPaths.Load(path)
	if !found {
		_, err = exec.LookPath(path)
		err, _ = execPaths.LoadOrStore(path, err)
	}
	if err != nil {
		t.Skipf("skipping test: %s: %s", path, err)
	}
}

// CleanCmdEnv will fill cmd.Env with the environment, excluding certain
// variables that could modify the behavior of the Go tools such as
// GODEBUG and GOTRACEBACK.
func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
	if cmd.Env != nil {
		panic("environment already set")
	}
	for _, env := range os.Environ() {
		// Exclude GODEBUG from the environment to prevent its output
		// from breaking tests that are trying to parse other command output.
		if strings.HasPrefix(env, "GODEBUG=") {
			continue
		}
		// Exclude GOTRACEBACK for the same reason.
		if strings.HasPrefix(env, "GOTRACEBACK=") {
			continue
		}
		cmd.Env = append(cmd.Env, env)
	}
	return cmd
}