// Copyright 2018 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 main

import (
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// vetCheck runs the "vet" tool on the source code in req.Body.
// In case of no errors it returns an empty, non-nil *response.
// Otherwise &response.Errors contains found errors.
//
// Deprecated: this is the handler for the legacy /vet endpoint; use
// the /compile (compileAndRun) handler instead with the WithVet
// boolean set. This code path doesn't support modules and only exists
// as a temporary compatiblity bridge to older javascript clients.
func vetCheck(req *request) (*response, error) {
	tmpDir, err := ioutil.TempDir("", "vet")
	if err != nil {
		return nil, fmt.Errorf("error creating temp directory: %v", err)
	}
	defer os.RemoveAll(tmpDir)

	in := filepath.Join(tmpDir, progName)
	if err := ioutil.WriteFile(in, []byte(req.Body), 0400); err != nil {
		return nil, fmt.Errorf("error creating temp file %q: %v", in, err)
	}
	const useModules = false // legacy handler; no modules (see func comment)
	vetOutput, err := vetCheckInDir(tmpDir, os.Getenv("GOPATH"), useModules)
	if err != nil {
		// This is about errors running vet, not vet returning output.
		return nil, err
	}
	return &response{Errors: vetOutput}, nil
}

// vetCheckInDir runs go vet in the provided directory, using the
// provided GOPATH value, and whether modules are enabled. The
// returned error is only about whether go vet was able to run, not
// whether vet reported problem. The returned value is ("", nil) if
// vet successfully found nothing, and (non-empty, nil) if vet ran and
// found issues.
func vetCheckInDir(dir, goPath string, modules bool) (output string, execErr error) {
	cmd := exec.Command("go", "vet")
	if !modules {
		cmd.Args = append(cmd.Args, progName)
	}
	cmd.Dir = dir
	// Linux go binary is not built with CGO_ENABLED=0.
	// Prevent vet to compile packages in cgo mode.
	// See #26307.
	cmd.Env = append(os.Environ(), "CGO_ENABLED=0", "GOPATH="+goPath)
	if modules {
		cmd.Env = append(cmd.Env,
			"GO111MODULE=on",
			"GOPROXY=https://proxy.golang.org",
		)
	}
	out, err := cmd.CombinedOutput()
	if err == nil {
		return "", nil
	}
	if _, ok := err.(*exec.ExitError); !ok {
		return "", fmt.Errorf("error vetting go source: %v", err)
	}

	// Rewrite compiler errors to refer to progName
	// instead of '/tmp/sandbox1234/main.go'.
	errs := strings.Replace(string(out), dir, "", -1)

	// Remove vet's package name banner.
	if strings.HasPrefix(errs, "#") {
		if nl := strings.Index(errs, "\n"); nl != -1 {
			errs = errs[nl+1:]
		}
	}
	return errs, nil
}