package net

import (
	"errors"
	"io/ioutil"
	"net"
	"os"

	"github.com/rajch/weave/db"
	"github.com/weaveworks/mesh"
)

func getOldStyleSystemUUID() ([]byte, error) {
	uuid, err := ioutil.ReadFile("/sys/class/dmi/id/product_uuid")
	if os.IsNotExist(err) {
		uuid, err = ioutil.ReadFile("/sys/hypervisor/uuid")
	}
	return uuid, err
}

func getSystemUUID(hostRoot string) ([]byte, error) {
	uuid, err := getOldStyleSystemUUID()
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	machineid, err := ioutil.ReadFile(hostRoot + "/etc/machine-id")
	if os.IsNotExist(err) {
		machineid, err = ioutil.ReadFile(hostRoot + "/var/lib/dbus/machine-id")
	}
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	if len(uuid) == 0 && len(machineid) == 0 {
		return nil, errors.New("All system IDs are blank")
	}
	return append(machineid, uuid...), nil
}

func getPersistedPeerName(dbPrefix string) (mesh.PeerName, error) {
	d, err := db.NewBoltDBReadOnly(dbPrefix)
	if err != nil {
		return mesh.UnknownPeerName, err
	}
	defer d.Close()
	var peerName mesh.PeerName
	nameFound, err := d.Load(db.NameIdent, &peerName)
	if err != nil || !nameFound {
		return mesh.UnknownPeerName, err
	}
	return peerName, nil
}

// GetSystemPeerName returns an ID derived from concatenated machine-id
// (either systemd or dbus), the system (aka bios) UUID and the
// hypervisor UUID.  It is tweaked and formatted to be usable as a mac address
func GetSystemPeerName(dbPrefix, hostRoot string) (string, error) {
	// Check if we have a persisted name that matches the old-style ID for this host
	if oldUUID, err := getOldStyleSystemUUID(); err == nil {
		if _, err := os.Stat(db.Pathname(dbPrefix)); err == nil {
			persistedPeerName, err := getPersistedPeerName(dbPrefix)
			if err != nil && !os.IsNotExist(err) {
				return "", err
			}
			if persistedPeerName == mesh.PeerNameFromBin(MACfromUUID(oldUUID)) {
				return persistedPeerName.String(), nil
			}
		}
	} else if !os.IsNotExist(err) {
		return "", err
	}
	var mac net.HardwareAddr
	if uuid, err := getSystemUUID(hostRoot); err == nil {
		mac = MACfromUUID(uuid)
	} else if !os.IsNotExist(err) {
		return "", err
	} else {
		mac, err = RandomMAC()
		if err != nil {
			return "", err
		}
	}
	return mac.String(), nil
}