// Copyright 2018 The Fuchsia 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 makeroot.go script copies a GOROOT. It is a precursor to makefuchsia.go,
// used to stage a clean GOROOT into the build directory.
// Note: this script exists because the `go` tool globs for inputs, as such, a
// copy tool is required that will actively remove files that are not found in
// the source.

package main

import (
	"bytes"
	"flag"
	"io"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"time"
)

var (
	sourceGoroot = flag.String("source-goroot", "", "GOROOT to copy from")
	targetGoroot = flag.String("target-goroot", "", "GOROOT to copy into")
	depfilePath  = flag.String("depfile", "", "depfile to write into")
	stampPath    = flag.String("stamp-file", "", "Path of a file to create upon completion")
)

func main() {
	log.SetFlags(log.Lshortfile)
	flag.Parse()

	if err := os.RemoveAll(*targetGoroot); err != nil {
		log.Fatal(err)
	}

	var buf bytes.Buffer
	buf.WriteString(*stampPath)
	buf.WriteByte(':')

	git, err := exec.LookPath("git")
	if err != nil {
		log.Fatal(err)
	}
	cmd := exec.Command(git, "--no-optional-locks", "-C", *sourceGoroot, "ls-files", "--cached", "--others", "--exclude-standard", "-z")
	out, err := cmd.Output()
	if err != nil {
		log.Fatal(err)
	}
	for _, path := range bytes.Split(out, []byte{0}) {
		if len(path) == 0 {
			continue
		}
		path := string(path)
		src := filepath.Join(*sourceGoroot, path)
		dst := filepath.Join(*targetGoroot, path)
		srcFile, err := os.Open(src)
		if err != nil {
			// Renaming or deleting files will cause git ls-files to return the old (or deleted)
			// paths unless the change is staged, so ignore these errors.
			if os.IsNotExist(err) {
				log.Print("could not open file: ", src)
				continue
			}
			log.Fatal(err)
		}
		dstDir := filepath.Dir(dst)
		if _, err := os.Stat(dstDir); os.IsNotExist(err) {
			info, err := os.Stat(filepath.Dir(src))
			if err != nil {
				log.Fatal(err)
			}
			if err := os.MkdirAll(dstDir, info.Mode()); err != nil {
				log.Fatal(err)
			}
		} else if err != nil {
			log.Fatal(err)
		}
		info, err := srcFile.Stat()
		if err != nil {
			log.Fatal(err)
		}
		dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, info.Mode())
		if err != nil {
			log.Fatal(err)
		}
		if _, err := io.Copy(dstFile, srcFile); err != nil {
			log.Fatal(err)
		}
		if err := dstFile.Close(); err != nil {
			log.Fatal(err)
		}
		if err := srcFile.Close(); err != nil {
			log.Fatal(err)
		}
		buf.WriteByte(' ')
		buf.WriteString(src)
	}
	buf.WriteByte('\n')

	if err := os.WriteFile(*depfilePath, buf.Bytes(), os.ModePerm); err != nil {
		log.Fatal(err)
	}

	f, err := os.OpenFile(*stampPath, os.O_CREATE|os.O_TRUNC, os.ModePerm)
	if err != nil {
		log.Fatal(err)
	}
	if err := f.Close(); err != nil {
		log.Fatal(err)
	}
	now := time.Now()
	if err := os.Chtimes(*stampPath, now, now); err != nil {
		log.Fatal(err)
	}
}