// Copyright 2021 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.

// The helper functions in this package are copied from the original
// versions from the file of the same name in $GOROOT/src/internal.

package testenv

import (
	"errors"
	"fmt"
	"go/build"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"testing"
)

// HasGoBuild reports whether the current system can build programs
// with “go build” and then run them with os.StartProcess or
// exec.Command.
func HasGoBuild() bool {
	if os.Getenv("GO_GCFLAGS") != "" {
		// It's too much work to require every caller of the go command
		// to pass along "-gcflags="+os.Getenv("GO_GCFLAGS").
		// For now, if $GO_GCFLAGS is set, report that we simply can't
		// run go build.
		return false
	}
	switch runtime.GOOS {
	case "android", "js", "ios":
		return false
	}
	return true
}

// MustHaveGoBuild checks that the current system can build programs with “go build”
// and then run them with os.StartProcess or exec.Command.
// If not, MustHaveGoBuild calls t.Skip with an explanation.
func MustHaveGoBuild(t testing.TB) {
	if os.Getenv("GO_GCFLAGS") != "" {
		t.Skipf("skipping test: 'go build' not compatible with setting $GO_GCFLAGS")
	}
	if !HasGoBuild() {
		t.Skipf("skipping test: 'go build' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
}

// GoToolPath reports the path to the Go tool.
// It is a convenience wrapper around GoTool.
// If the tool is unavailable GoToolPath calls t.Skip.
// If the tool should be available and isn't, GoToolPath calls t.Fatal.
func GoToolPath(t testing.TB) string {
	MustHaveGoBuild(t)
	path, err := GoTool()
	if err != nil {
		t.Fatal(err)
	}
	return path
}

// GoTool reports the path to the Go tool.
func GoTool() (string, error) {
	if !HasGoBuild() {
		return "", errors.New("platform cannot run go tool")
	}
	var exeSuffix string
	if runtime.GOOS == "windows" {
		exeSuffix = ".exe"
	}
	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
	if _, err := os.Stat(path); err == nil {
		return path, nil
	}
	goBin, err := exec.LookPath("go" + exeSuffix)
	if err != nil {
		return "", errors.New("cannot find go tool: " + err.Error())
	}
	return goBin, nil
}

// HasExternalNetwork reports whether the current system can use
// external (non-localhost) networks.
func HasExternalNetwork() bool {
	return !testing.Short() && runtime.GOOS != "js"
}

// MustHaveExternalNetwork checks that the current system can use
// external (non-localhost) networks.
// If not, MustHaveExternalNetwork calls t.Skip with an explanation.
func MustHaveExternalNetwork(t testing.TB) {
	if runtime.GOOS == "js" {
		t.Skipf("skipping test: no external network on %s", runtime.GOOS)
	}
	if testing.Short() {
		t.Skipf("skipping test: no external network in -short mode")
	}
}

// Go1Point returns the x in Go 1.x.
func Go1Point() int {
	for i := len(build.Default.ReleaseTags) - 1; i >= 0; i-- {
		var version int
		if _, err := fmt.Sscanf(build.Default.ReleaseTags[i], "go1.%d", &version); err != nil {
			continue
		}
		return version
	}
	panic("bad release tags")
}

// Testing is an abstraction of a *testing.T.
type Testing interface {
	Skipf(format string, args ...interface{})
	Fatalf(format string, args ...interface{})
}

type helperer interface {
	Helper()
}

// NeedsGo1Point skips t if the Go version used to run the test is
// older than 1.x.
func NeedsGo1Point(t Testing, x int) {
	if t, ok := t.(helperer); ok {
		t.Helper()
	}
	if Go1Point() < x {
		t.Skipf("running Go version %q is version 1.%d, older than required 1.%d", runtime.Version(), Go1Point(), x)
	}
}