package group

import (
	"encoding/json"
	"os"
	"path"
	"path/filepath"
	"strings"
	"time"
)

// Description represents a group description together with some metadata
// about the JSON file it was deserialised from.
type Description struct {
	// The file this was deserialised from.  This is not necessarily
	// the name of the group, for example in case of a subgroup.
	FileName string `json:"-"`

	// The modtime and size of the file.  These are used to detect
	// when a file has changed on disk.
	modTime  time.Time `json:"-"`
	fileSize int64     `json:"-"`

	// The user-friendly group name
	DisplayName string `json:"displayName,omitempty"`

	// A user-readable description of the group.
	Description string `json:"description,omitempty"`

	// A user-readable contact, typically an e-mail address.
	Contact string `json:"contact,omitempty"`

	// A user-readable comment.  Ignored by the server.
	Comment string `json:"comment,omitempty"`

	// Whether to display the group on the landing page.
	Public bool `json:"public,omitempty"`

	// A URL to redirect the group to.  If this is not empty, most
	// other fields are ignored.
	Redirect string `json:"redirect,omitempty"`

	// The maximum number of simultaneous clients.  Unlimited if 0.
	MaxClients int `json:"max-clients,omitempty"`

	// The time for which history entries are kept.
	MaxHistoryAge int `json:"max-history-age,omitempty"`

	// Whether users are allowed to log in with an empty username.
	AllowAnonymous bool `json:"allow-anonymous,omitempty"`

	// Whether recording is allowed.
	AllowRecording bool `json:"allow-recording,omitempty"`

	// Whether creating tokens is allowed
	UnrestrictedTokens bool `json:"unrestricted-tokens,omitempty"`

	// Whether subgroups are created on the fly.
	AllowSubgroups bool `json:"allow-subgroups,omitempty"`

	// Whether to lock the group when the last op logs out.
	Autolock bool `json:"autolock,omitempty"`

	// Whether to kick all users when the last op logs out.
	Autokick bool `json:"autokick,omitempty"`

	// A list of logins for ops.
	Op []ClientPattern `json:"op,omitempty"`

	// A list of logins for presenters.
	Presenter []ClientPattern `json:"presenter,omitempty"`

	// A list of logins for non-presenting users.
	Other []ClientPattern `json:"other,omitempty"`

	// The (public) keys used for token authentication.
	AuthKeys []map[string]interface{} `json:"authKeys,omitempty"`

	// The URL of the authentication server, if any.
	AuthServer string `json:"authServer,omitempty"`

	// The URL of the authentication portal, if any.
	AuthPortal string `json:"authPortal,omitempty"`

	// Codec preferences.  If empty, a suitable default is chosen in
	// the APIFromNames function.
	Codecs []string `json:"codecs,omitempty"`
}

const DefaultMaxHistoryAge = 4 * time.Hour

func maxHistoryAge(desc *Description) time.Duration {
	if desc.MaxHistoryAge != 0 {
		return time.Duration(desc.MaxHistoryAge) * time.Second
	}
	return DefaultMaxHistoryAge
}

func getDescriptionFile[T any](name string, get func(string) (T, error)) (T, string, bool, error) {
	isParent := false
	for name != "" {
		fileName := filepath.Join(
			Directory, path.Clean("/"+name)+".json",
		)
		r, err := get(fileName)
		if !os.IsNotExist(err) {
			return r, fileName, isParent, err
		}
		isParent = true
		name, _ = path.Split(name)
		name = strings.TrimRight(name, "/")
	}
	var zero T
	return zero, "", false, os.ErrNotExist
}

// descriptionMatch returns true if the description hasn't changed between
// d1 and d2
func descriptionMatch(d1, d2 *Description) bool {
	if d1.FileName != d2.FileName {
		return false
	}

	if d1.fileSize != d2.fileSize || !d1.modTime.Equal(d2.modTime) {
		return false
	}
	return true
}

// descriptionUnchanged returns true if a group's description hasn't
// changed since it was last read.
func descriptionUnchanged(name string, desc *Description) bool {
	fi, fileName, _, err := getDescriptionFile(name, os.Stat)
	if err != nil || fileName != desc.FileName {
		return false
	}

	if fi.Size() != desc.fileSize || !fi.ModTime().Equal(desc.modTime) {
		return false
	}
	return true
}

// GetDescription gets a group description, either from cache or from disk
func GetDescription(name string) (*Description, error) {
	g := Get(name)
	if g != nil {
		if descriptionUnchanged(name, g.description) {
			return g.description, nil
		}
	}

	return readDescription(name)
}

// readDescription reads a group's description from disk
func readDescription(name string) (*Description, error) {
	r, fileName, isParent, err := getDescriptionFile(name, os.Open)
	if err != nil {
		return nil, err
	}
	defer r.Close()

	var desc Description

	fi, err := r.Stat()
	if err != nil {
		return nil, err
	}

	d := json.NewDecoder(r)
	d.DisallowUnknownFields()
	err = d.Decode(&desc)
	if err != nil {
		return nil, err
	}
	if isParent {
		if !desc.AllowSubgroups {
			return nil, os.ErrNotExist
		}
		desc.Public = false
		desc.Description = ""
	}

	desc.FileName = fileName
	desc.fileSize = fi.Size()
	desc.modTime = fi.ModTime()

	return &desc, nil
}