// Command flock-installer is the DaemonSet init container. It copies
// /usr/local/bin/flock to /opt/cni/bin/flock on the host, and writes the
// CNI conflist to /etc/cni/net.d/01-flock.conflist. The init container
// then exits; kubelet picks up the conflist on its next CNI scan.
package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
)

const conflistTemplate = `{
  "cniVersion": "1.0.0",
  "name": "flock",
  "plugins": [
    {
      "type": "flock"
    }
  ]
}
`

func main() {
	var (
		src     = flag.String("src", "/usr/local/bin/flock", "source binary path")
		binDst  = flag.String("bin", "/host/opt/cni/bin/flock", "destination CNI binary path")
		confDst = flag.String("conflist", "/host/etc/cni/net.d/01-flock.conflist", "destination conflist path")
	)
	flag.Parse()

	if err := copyFile(*src, *binDst, 0o755); err != nil {
		log.Fatalf("install binary: %v", err)
	}
	if err := os.MkdirAll(filepath.Dir(*confDst), 0o755); err != nil {
		log.Fatalf("conflist mkdir: %v", err)
	}
	if err := os.WriteFile(*confDst, []byte(conflistTemplate), 0o644); err != nil {
		log.Fatalf("write conflist: %v", err)
	}
	fmt.Printf("flock-installer: installed %s and %s\n", *binDst, *confDst)
}

func copyFile(src, dst string, mode os.FileMode) error {
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		return err
	}
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()
	tmp := dst + ".tmp"
	out, err := os.OpenFile(tmp, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, mode)
	if err != nil {
		return err
	}
	if _, err := io.Copy(out, in); err != nil {
		out.Close()
		os.Remove(tmp)
		return err
	}
	if err := out.Close(); err != nil {
		os.Remove(tmp)
		return err
	}
	return os.Rename(tmp, dst)
}