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

import (
	"isle/admin"
	"isle/garage"
	"isle/nebula"
	"crypto/sha512"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"

	"gopkg.in/yaml.v3"
)

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

// 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.yml")
}

// Bootstrap is used for accessing all information contained within a
// bootstrap.yml file.
type Bootstrap struct {
	AdminCreationParams admin.CreationParams `yaml:"admin_creation_params"`

	Hosts    map[string]Host `yaml:"hosts"`
	HostName string          `yaml:"hostname"`

	Nebula struct {
		CAPublicCredentials     nebula.CAPublicCredentials `yaml:"ca_public_credentials"`
		HostCredentials         nebula.HostCredentials     `yaml:"host_credentials"`
		SignedPublicCredentials string                     `yaml:"signed_public_credentials"`
	} `yaml:"nebula"`

	Garage struct {
		RPCSecret                    string                  `yaml:"rpc_secret"`
		AdminToken                   string                  `yaml:"admin_token"`
		GlobalBucketS3APICredentials garage.S3APICredentials `yaml:"global_bucket_s3_api_credentials"`
	} `yaml:"garage"`
}

// FromReader reads a bootstrap.yml file from the given io.Reader.
func FromReader(r io.Reader) (Bootstrap, error) {
	var b Bootstrap
	err := yaml.NewDecoder(r).Decode(&b)
	return b, err
}

// FromFile reads a bootstrap.yml from a file at the given path.
func FromFile(path string) (Bootstrap, error) {

	f, err := os.Open(path)
	if err != nil {
		return Bootstrap{}, fmt.Errorf("opening file: %w", err)
	}
	defer f.Close()

	return FromReader(f)
}

// WriteTo writes the Bootstrap as a new bootstrap.yml to the given io.Writer.
func (b Bootstrap) WriteTo(into io.Writer) error {
	return yaml.NewEncoder(into).Encode(b)
}

// 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.HostName]
	if !ok {
		panic(fmt.Sprintf("hostname %q not defined in bootstrap's hosts", b.HostName))
	}

	return host
}

// Hash returns a deterministic hash of the given hosts map.
func HostsHash(hostsMap map[string]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 := yaml.NewEncoder(h).Encode(hosts); err != nil {
		return nil, err
	}

	return h.Sum(nil), nil
}