// Package store holds the server's authoritative metadata: users, nested
// groups, databases and the grants that connect them.
//
// Glossary:
//
//	User        an account, authenticated by password+TOTP or by OIDC.
//	Group       a node in a single tree of groups. Grants hang off groups.
//	Membership  a user's place in one group, as member or admin.
//	Database    one KDBX file tracked by the server. Owned by one group.
//	Grant       a (group, database, permission) triple.
//	Invite      a single- or multi-use registration token.
//	Session     a bearer token held by a client device.
package store

import "time"

// Perm is a permission on a database, ordered read < write < admin.
type Perm string

const (
	PermNone  Perm = ""
	PermRead  Perm = "read"
	PermWrite Perm = "write"
	PermAdmin Perm = "admin"
)

var permRank = map[Perm]int{PermNone: 0, PermRead: 1, PermWrite: 2, PermAdmin: 3}

// Rank orders permissions so the strongest of several grants can be picked.
func (p Perm) Rank() int { return permRank[p] }

// AtLeast reports whether p is as strong as want.
func (p Perm) AtLeast(want Perm) bool { return p.Rank() >= want.Rank() }

// Valid reports whether p is a permission that may be stored.
func (p Perm) Valid() bool { return p == PermRead || p == PermWrite || p == PermAdmin }

// Role is a user's role inside a group.
type Role string

const (
	RoleMember Role = "member"
	RoleAdmin  Role = "admin"
)

// Valid reports whether r is a role that may be stored.
func (r Role) Valid() bool { return r == RoleMember || r == RoleAdmin }

// Strategy decides what happens when a client pushes a database version that
// is no longer current.
type Strategy string

const (
	// StrategyServerWins rejects the stale push; the client takes the server
	// copy and keeps its own as a conflict file. This is the default.
	StrategyServerWins Strategy = "server-wins"
	// StrategyClientWins lets the client overwrite the server copy.
	StrategyClientWins Strategy = "client-wins"
	// StrategyManual rejects the stale push and leaves both copies in place
	// for a human to reconcile.
	StrategyManual Strategy = "manual"
)

// Valid reports whether s is a strategy that may be stored.
func (s Strategy) Valid() bool {
	return s == StrategyServerWins || s == StrategyClientWins || s == StrategyManual
}

type User struct {
	ID            string    `json:"id"`
	Username      string    `json:"username"`
	Email         string    `json:"email,omitempty"`
	PassHash      string    `json:"pass_hash,omitempty"`
	OIDCIssuer    string    `json:"oidc_issuer,omitempty"`
	OIDCSubject   string    `json:"oidc_subject,omitempty"`
	TOTPSecret    string    `json:"totp_secret,omitempty"`
	TOTPConfirmed bool      `json:"totp_confirmed"`
	ServerAdmin   bool      `json:"server_admin"`
	Disabled      bool      `json:"disabled"`
	CreatedAt     time.Time `json:"created_at"`
}

type Group struct {
	ID        string    `json:"id"`
	Name      string    `json:"name"`
	ParentID  string    `json:"parent_id,omitempty"`
	CreatedAt time.Time `json:"created_at"`
}

type Membership struct {
	UserID  string `json:"user_id"`
	GroupID string `json:"group_id"`
	Role    Role   `json:"role"`
}

type Database struct {
	ID            string    `json:"id"`
	Name          string    `json:"name"`
	OwnerGroupID  string    `json:"owner_group_id"`
	MergeStrategy Strategy  `json:"merge_strategy"`
	Version       int64     `json:"version"`
	SHA256        string    `json:"sha256"`
	Size          int64     `json:"size"`
	UpdatedAt     time.Time `json:"updated_at"`
	UpdatedBy     string    `json:"updated_by,omitempty"`
}

type Grant struct {
	GroupID    string `json:"group_id"`
	DatabaseID string `json:"database_id"`
	Perm       Perm   `json:"perm"`
}

type Invite struct {
	Token     string    `json:"token"`
	GroupID   string    `json:"group_id,omitempty"`
	Role      Role      `json:"role"`
	CreatedBy string    `json:"created_by"`
	CreatedAt time.Time `json:"created_at"`
	ExpiresAt time.Time `json:"expires_at"`
	MaxUses   int       `json:"max_uses"`
	Uses      int       `json:"uses"`
}

// Usable reports whether the invite may still be redeemed at time now.
func (i *Invite) Usable(now time.Time) bool {
	return now.Before(i.ExpiresAt) && (i.MaxUses <= 0 || i.Uses < i.MaxUses)
}

type Session struct {
	Token     string    `json:"token"`
	UserID    string    `json:"user_id"`
	Label     string    `json:"label,omitempty"`
	CreatedAt time.Time `json:"created_at"`
	ExpiresAt time.Time `json:"expires_at"`
}

// DeviceAuth backs the browser-assisted login used for OIDC on desktop and
// Android: the client shows a short user code, the browser approves it, the
// client polls until a session token appears.
type DeviceAuth struct {
	DeviceCode   string    `json:"device_code"`
	UserCode     string    `json:"user_code"`
	Label        string    `json:"label,omitempty"`
	SessionToken string    `json:"session_token,omitempty"`
	OIDCState    string    `json:"oidc_state,omitempty"`
	CreatedAt    time.Time `json:"created_at"`
	ExpiresAt    time.Time `json:"expires_at"`
}

// State is the whole metadata set, serialized as one JSON document.
type State struct {
	Users       map[string]*User       `json:"users"`
	Groups      map[string]*Group      `json:"groups"`
	Databases   map[string]*Database   `json:"databases"`
	Invites     map[string]*Invite     `json:"invites"`
	Sessions    map[string]*Session    `json:"sessions"`
	Devices     map[string]*DeviceAuth `json:"devices"`
	Memberships []Membership           `json:"memberships"`
	Grants      []Grant                `json:"grants"`
}

func newState() *State {
	return &State{
		Users:     map[string]*User{},
		Groups:    map[string]*Group{},
		Databases: map[string]*Database{},
		Invites:   map[string]*Invite{},
		Sessions:  map[string]*Session{},
		Devices:   map[string]*DeviceAuth{},
	}
}

func (s *State) init() {
	if s.Users == nil {
		s.Users = map[string]*User{}
	}
	if s.Groups == nil {
		s.Groups = map[string]*Group{}
	}
	if s.Databases == nil {
		s.Databases = map[string]*Database{}
	}
	if s.Invites == nil {
		s.Invites = map[string]*Invite{}
	}
	if s.Sessions == nil {
		s.Sessions = map[string]*Session{}
	}
	if s.Devices == nil {
		s.Devices = map[string]*DeviceAuth{}
	}
}

// UserByName finds a user by exact username.
func (s *State) UserByName(name string) *User {
	for _, u := range s.Users {
		if u.Username == name {
			return u
		}
	}
	return nil
}

// UserByOIDC finds a user previously linked to an OIDC issuer and subject.
func (s *State) UserByOIDC(issuer, subject string) *User {
	for _, u := range s.Users {
		if u.OIDCIssuer == issuer && u.OIDCSubject == subject {
			return u
		}
	}
	return nil
}

// DeviceByUserCode finds a pending device login by the code shown to the user.
func (s *State) DeviceByUserCode(code string) *DeviceAuth {
	for _, d := range s.Devices {
		if d.UserCode == code {
			return d
		}
	}
	return nil
}