// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package vm

import (
	"bufio"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"path/filepath"
)

// IPAMRecord describes a single record about a node.
type IPAMRecord struct {
	IP          net.IP
	Netmask     net.IPMask
	MAC         string
	Hostname    string
	Gateway     net.IP
	MTU         int
	Nameservers []net.IP

	TFTPServer       string
	IPXEBootFilename string
}

// IPAMDatabase is a mapping from MAC address to records.
type IPAMDatabase map[string]IPAMRecord

const dbFile = "ipam.db"

// DumpIPAMRecord appends IPAM record to the database.
func DumpIPAMRecord(statePath string, record IPAMRecord) error {
	f, err := os.OpenFile(filepath.Join(statePath, dbFile), os.O_APPEND|os.O_WRONLY|os.O_CREATE, os.ModePerm)
	if err != nil {
		return err
	}

	defer f.Close() //nolint: errcheck

	// need atomic write, buffering json
	b, err := json.Marshal(record)
	if err != nil {
		return fmt.Errorf("error marshaling IPAM record: %w", err)
	}

	_, err = f.Write(append(b, '\n'))

	return err
}

// LoadIPAMRecords loads all the IPAM records indexed by the MAC address.
func LoadIPAMRecords(statePath string) (IPAMDatabase, error) {
	f, err := os.Open(filepath.Join(statePath, dbFile))
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}

		return nil, err
	}

	defer f.Close() //nolint: errcheck

	result := make(IPAMDatabase)

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		var record IPAMRecord

		if err := json.Unmarshal(scanner.Bytes(), &record); err != nil {
			return nil, err
		}

		result[record.MAC] = record
	}

	return result, scanner.Err()
}