// Package bootstrap deals with the parsing and creation of bootstrap.json
// files. It also contains some helpers which rely on bootstrap data.
package bootstrap

import (
	"crypto/sha512"
	"encoding/json"
	"fmt"
	"isle/nebula"
	"net/netip"
	"path/filepath"
	"sort"
)

// StateDirPath returns the path within the user's state directory where the
// bootstrap file is stored.
func StateDirPath(dataDirPath string) string {
	return filepath.Join(dataDirPath, "bootstrap.json")
}

// AppDirPath returns the path within the AppDir where an embedded bootstrap
// file might be found.
func AppDirPath(appDirPath string) string {
	return filepath.Join(appDirPath, "share/bootstrap.json")
}

// CreationParams are general parameters used when creating a new network. These
// are available to all hosts within the network via their bootstrap files.
type CreationParams struct {
	ID     string
	Name   string
	Domain string
}

// Bootstrap contains all information which is needed by a host daemon to join a
// network on boot.
type Bootstrap struct {
	NetworkCreationParams CreationParams
	CAPublicCredentials   nebula.CAPublicCredentials

	PrivateCredentials nebula.HostPrivateCredentials
	HostAssigned       `json:"-"`
	SignedHostAssigned nebula.Signed[HostAssigned] // signed by CA

	Hosts map[nebula.HostName]Host
}

// New initializes and returns a new Bootstrap file for a new host. This
// function assigns Hosts an empty map.
func New(
	caCreds nebula.CACredentials,
	adminCreationParams CreationParams,
	name nebula.HostName,
	ip netip.Addr,
) (
	Bootstrap, error,
) {
	hostPubCreds, hostPrivCreds, err := nebula.NewHostCredentials(
		caCreds, name, ip,
	)
	if err != nil {
		return Bootstrap{}, fmt.Errorf("generating host credentials: %w", err)
	}

	assigned := HostAssigned{
		Name:              name,
		PublicCredentials: hostPubCreds,
	}

	signedAssigned, err := nebula.Sign(assigned, caCreds.SigningPrivateKey)
	if err != nil {
		return Bootstrap{}, fmt.Errorf("signing assigned fields: %w", err)
	}

	return Bootstrap{
		NetworkCreationParams: adminCreationParams,
		CAPublicCredentials:   caCreds.Public,
		PrivateCredentials:    hostPrivCreds,
		HostAssigned:          assigned,
		SignedHostAssigned:    signedAssigned,
		Hosts:                 map[nebula.HostName]Host{},
	}, nil
}

// UnmarshalJSON implements the json.Unmarshaler interface. It will
// automatically populate the HostAssigned field by unwrapping the
// SignedHostAssigned field.
func (b *Bootstrap) UnmarshalJSON(data []byte) error {
	type inner Bootstrap

	err := json.Unmarshal(data, (*inner)(b))
	if err != nil {
		return err
	}

	b.HostAssigned, err = b.SignedHostAssigned.Unwrap(
		b.CAPublicCredentials.SigningKey,
	)
	if err != nil {
		return fmt.Errorf("unwrapping HostAssigned: %w", err)
	}

	return nil
}

// ThisHost is a shortcut for b.Hosts[b.HostName], but will panic if the
// HostName isn't found in the Hosts map.
func (b Bootstrap) ThisHost() Host {
	host, ok := b.Hosts[b.Name]
	if !ok {
		panic(fmt.Sprintf("hostname %q not defined in bootstrap's hosts", b.Name))
	}

	return host
}

// Hash returns a deterministic hash of the given hosts map.
func HostsHash(hostsMap map[nebula.HostName]Host) ([]byte, error) {

	hosts := make([]Host, 0, len(hostsMap))
	for _, host := range hostsMap {
		hosts = append(hosts, host)
	}

	sort.Slice(hosts, func(i, j int) bool {
		return hosts[i].Name < hosts[j].Name
	})

	h := sha512.New()
	if err := json.NewEncoder(h).Encode(hosts); err != nil {
		return nil, err
	}

	return h.Sum(nil), nil
}