// Copyright 2020 The Monogon Project Authors.
//
// SPDX-License-Identifier: Apache-2.0
//
// 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 main

import (
	"fmt"
	"io/ioutil"
	"os"

	"github.com/diskfs/go-diskfs"
	"github.com/diskfs/go-diskfs/disk"
	"github.com/diskfs/go-diskfs/filesystem"
	"github.com/diskfs/go-diskfs/partition/gpt"
)

var SmalltownDataPartition gpt.Type = gpt.Type("9eeec464-6885-414a-b278-4305c51f7966")

func mibToSectors(size uint64) uint64 {
	return (size * 1024 * 1024) / 512
}

func main() {
	if len(os.Args) < 3 {
		fmt.Println("Usage: mkimage <UEFI payload> <image path>")
		os.Exit(2)
	}
	_ = os.Remove(os.Args[2])
	diskImg, err := diskfs.Create(os.Args[2], 3*1024*1024*1024, diskfs.Raw)
	if err != nil {
		fmt.Printf("Failed to create disk: %v", err)
		os.Exit(1)
	}

	table := &gpt.Table{
		// This is appropriate at least for virtio disks. Might need to be adjusted for real ones.
		LogicalSectorSize:  512,
		PhysicalSectorSize: 512,
		ProtectiveMBR:      true,
		Partitions: []*gpt.Partition{
			{
				Type:  gpt.EFISystemPartition,
				Name:  "ESP",
				Start: mibToSectors(1),
				End:   mibToSectors(128) - 1,
			},
			{
				Type:  SmalltownDataPartition,
				Name:  "SIGNOS-DATA",
				Start: mibToSectors(128),
				End:   mibToSectors(2560) - 1,
			},
		},
	}
	if err := diskImg.Partition(table); err != nil {
		fmt.Printf("Failed to apply partition table: %v", err)
		os.Exit(1)
	}

	fs, err := diskImg.CreateFilesystem(disk.FilesystemSpec{Partition: 1, FSType: filesystem.TypeFat32, VolumeLabel: "ESP"})
	if err != nil {
		fmt.Printf("Failed to create filesystem: %v", err)
		os.Exit(1)
	}
	if err := fs.Mkdir("/EFI"); err != nil {
		panic(err)
	}
	if err := fs.Mkdir("/EFI/BOOT"); err != nil {
		panic(err)
	}
	if err := fs.Mkdir("/EFI/smalltown"); err != nil {
		panic(err)
	}
	efiPayload, err := fs.OpenFile("/EFI/BOOT/BOOTX64.EFI", os.O_CREATE|os.O_RDWR)
	if err != nil {
		fmt.Printf("Failed to open EFI payload for writing: %v", err)
		os.Exit(1)
	}
	efiPayloadSrc, err := os.Open(os.Args[1])
	if err != nil {
		fmt.Printf("Failed to open EFI payload for reading: %v", err)
		os.Exit(1)
	}
	defer efiPayloadSrc.Close()
	// If this is streamed (e.g. using io.Copy) it exposes a bug in diskfs, so do it in one go.
	efiPayloadFull, err := ioutil.ReadAll(efiPayloadSrc)
	if err != nil {
		panic(err)
	}
	if _, err := efiPayload.Write(efiPayloadFull); err != nil {
		fmt.Printf("Failed to write EFI payload: %v", err)
		os.Exit(1)
	}
	if err := diskImg.File.Close(); err != nil {
		fmt.Printf("Failed to write image: %v", err)
		os.Exit(1)
	}
	fmt.Println("Success! You can now boot smalltown.img")
}