// Copyright © 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package gitutil

import (
	"bytes"
	"io"
	"os"
	osexec "os/exec"
	"path/filepath"
	"strings"

	"github.com/golang/glog"
	"github.com/pkg/errors"
)

// EnsureCloned will clone into the destination path, otherwise will return no error.
func EnsureCloned(uri, destinationPath string) error {
	if ok, err := IsGitCloned(destinationPath); err != nil {
		return err
	} else if !ok {
		return exec("", "clone", "-v", uri, destinationPath)
	}
	return nil
}

// IsGitCloned will test if the path is a git dir.
func IsGitCloned(gitPath string) (bool, error) {
	f, err := os.Stat(filepath.Join(gitPath, ".git"))
	if os.IsNotExist(err) {
		return false, nil
	}
	return err == nil && f.IsDir(), err
}

// update will fetch origin and set HEAD to origin/HEAD.
func update(destinationPath string) error {
	return exec(destinationPath, "pull", "--ff-only", "-v")
}

// EnsureUpdated will ensure the destination path exists and is up to date.
func EnsureUpdated(uri, destinationPath string) error {
	if err := EnsureCloned(uri, destinationPath); err != nil {
		return err
	}
	return update(destinationPath)
}

func exec(pwd string, args ...string) error {
	glog.V(4).Infof("Going to run git %s", strings.Join(args, " "))
	cmd := osexec.Command("git", args...)
	cmd.Dir = pwd
	buf := bytes.Buffer{}
	var w io.Writer = &buf
	if glog.V(2) {
		w = io.MultiWriter(w, os.Stderr)
	}
	cmd.Stdout, cmd.Stderr = w, w
	if err := cmd.Run(); err != nil {
		return errors.Wrapf(err, "command execution failure, output=%q", buf.String())
	}
	return nil
}
