// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package util

import (
	"strconv"

	"v.io/v23/context"
	"v.io/v23/rpc"
	"v.io/v23/security/access"
	"v.io/v23/verror"
	"v.io/x/ref/services/syncbase/store"
)

func FormatVersion(version uint64) string {
	return strconv.FormatUint(version, 10)
}

func CheckVersion(ctx *context.T, presented string, actual uint64) error {
	if presented != "" && presented != FormatVersion(actual) {
		return verror.NewErrBadVersion(ctx)
	}
	return nil
}

// TODO(sadovsky): Perhaps these functions should strip key prefixes such as
// "c:" from the error messages they return.

type Permser interface {
	// GetPerms returns the Permissions for this Layer.
	GetPerms() access.Permissions
}

// GetWithAuth does Get followed by an auth check.
func GetWithAuth(ctx *context.T, call rpc.ServerCall, st store.StoreReader, k string, v Permser) error {
	if err := store.Get(ctx, st, k, v); err != nil {
		return err
	}
	auth, _ := access.PermissionsAuthorizer(v.GetPerms(), access.TypicalTagType())
	if err := auth.Authorize(ctx, call.Security()); err != nil {
		return verror.New(verror.ErrNoAccess, ctx, err)
	}
	return nil
}

// UpdateWithAuth performs a read-modify-write.
// Input v is populated by the "read" step. fn should "modify" v.
// Performs an auth check as part of the "read" step.
func UpdateWithAuth(ctx *context.T, call rpc.ServerCall, tx store.Transaction, k string, v Permser, fn func() error) error {
	if err := GetWithAuth(ctx, call, tx, k, v); err != nil {
		return err
	}
	if err := fn(); err != nil {
		return err
	}
	return store.Put(ctx, tx, k, v)
}

// ErrorToExists wraps a call to Get and returns true if Get found the
// object, false otherwise, suppressing ErrNoExist. Access errors are
// suppressed as well because they imply existence in some Get
// implementations.
// TODO(ivanpi): Revisit once ACL specification is finalized.
func ErrorToExists(err error) (bool, error) {
	if err == nil {
		return true, nil
	}
	switch verror.ErrorID(err) {
	case verror.ErrNoExist.ID:
		return false, nil
	case verror.ErrNoAccess.ID, verror.ErrNoExistOrNoAccess.ID:
		return false, nil
	default:
		return false, err
	}
}