// Copyright 2018 Google LLC All Rights Reserved.
//
// 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 cmd

import (
	"fmt"
	"io"
	"log"
	"os"

	"github.com/google/go-containerregistry/pkg/crane"
	v1 "github.com/google/go-containerregistry/pkg/v1"
	"github.com/google/go-containerregistry/pkg/v1/tarball"
	"github.com/spf13/cobra"
)

// NewCmdExport creates a new cobra.Command for the export subcommand.
func NewCmdExport(options *[]crane.Option) *cobra.Command {
	return &cobra.Command{
		Use:   "export IMAGE|- TARBALL|-",
		Short: "Export filesystem of a container image as a tarball",
		Example: `  # Write tarball to stdout
  crane export ubuntu -

  # Write tarball to file
  crane export ubuntu ubuntu.tar

  # Read image from stdin
  crane export - ubuntu.tar`,
		Args: cobra.RangeArgs(1, 2),
		RunE: func(_ *cobra.Command, args []string) error {
			src, dst := args[0], "-"
			if len(args) > 1 {
				dst = args[1]
			}

			var img v1.Image
			if src == "-" {
				tmpfile, err := os.CreateTemp("", "crane")
				if err != nil {
					log.Fatal(err)
				}
				defer os.Remove(tmpfile.Name())

				if _, err := io.Copy(tmpfile, os.Stdin); err != nil {
					log.Fatal(err)
				}
				tmpfile.Close()

				img, err = tarball.ImageFromPath(tmpfile.Name(), nil)
				if err != nil {
					return fmt.Errorf("reading tarball from stdin: %w", err)
				}
			} else {
				desc, err := crane.Get(src, *options...)
				if err != nil {
					return fmt.Errorf("pulling %s: %w", src, err)
				}
				if desc.MediaType.IsSchema1() {
					img, err = desc.Schema1()
					if err != nil {
						return fmt.Errorf("pulling schema 1 image %s: %w", src, err)
					}
				} else {
					img, err = desc.Image()
					if err != nil {
						return fmt.Errorf("pulling Image %s: %w", src, err)
					}
				}
			}

			f, err := openFile(dst)
			if err != nil {
				return fmt.Errorf("failed to open %s: %w", dst, err)
			}
			defer f.Close()

			return crane.Export(img, f)
		},
	}
}

func openFile(s string) (*os.File, error) {
	if s == "-" {
		return os.Stdout, nil
	}
	return os.Create(s)
}
