package server

import (
	"context"
	"errors"
	"fmt"
	"slices"

	nbdns "github.com/netbirdio/netbird/dns"
	"github.com/netbirdio/netbird/route"
	"github.com/rs/xid"
	log "github.com/sirupsen/logrus"

	"github.com/netbirdio/netbird/management/server/activity"
	nbgroup "github.com/netbirdio/netbird/management/server/group"
	"github.com/netbirdio/netbird/management/server/status"
)

type GroupLinkError struct {
	Resource string
	Name     string
}

func (e *GroupLinkError) Error() string {
	return fmt.Sprintf("group has been linked to %s: %s", e.Resource, e.Name)
}

// CheckGroupPermissions validates if a user has the necessary permissions to view groups
func (am *DefaultAccountManager) CheckGroupPermissions(ctx context.Context, accountID, userID string) error {
	settings, err := am.Store.GetAccountSettings(ctx, LockingStrengthShare, accountID)
	if err != nil {
		return err
	}

	user, err := am.Store.GetUserByUserID(ctx, LockingStrengthShare, userID)
	if err != nil {
		return err
	}

	if (!user.IsAdminOrServiceUser() && settings.RegularUsersViewBlocked) || user.AccountID != accountID {
		return status.Errorf(status.PermissionDenied, "groups are blocked for users")
	}

	return nil
}

// GetGroup returns a specific group by groupID in an account
func (am *DefaultAccountManager) GetGroup(ctx context.Context, accountID, groupID, userID string) (*nbgroup.Group, error) {
	if err := am.CheckGroupPermissions(ctx, accountID, userID); err != nil {
		return nil, err
	}

	return am.Store.GetGroupByID(ctx, LockingStrengthShare, groupID, accountID)
}

// GetAllGroups returns all groups in an account
func (am *DefaultAccountManager) GetAllGroups(ctx context.Context, accountID, userID string) ([]*nbgroup.Group, error) {
	if err := am.CheckGroupPermissions(ctx, accountID, userID); err != nil {
		return nil, err
	}

	return am.Store.GetAccountGroups(ctx, accountID)
}

// GetGroupByName filters all groups in an account by name and returns the one with the most peers
func (am *DefaultAccountManager) GetGroupByName(ctx context.Context, groupName, accountID string) (*nbgroup.Group, error) {
	return am.Store.GetGroupByName(ctx, LockingStrengthShare, groupName, accountID)
}

// SaveGroup object of the peers
func (am *DefaultAccountManager) SaveGroup(ctx context.Context, accountID, userID string, newGroup *nbgroup.Group) error {
	unlock := am.Store.AcquireWriteLockByUID(ctx, accountID)
	defer unlock()
	return am.SaveGroups(ctx, accountID, userID, []*nbgroup.Group{newGroup})
}

// SaveGroups adds new groups to the account.
// Note: This function does not acquire the global lock.
// It is the caller's responsibility to ensure proper locking is in place before invoking this method.
func (am *DefaultAccountManager) SaveGroups(ctx context.Context, accountID, userID string, newGroups []*nbgroup.Group) error {
	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return err
	}

	var eventsToStore []func()

	for _, newGroup := range newGroups {
		if newGroup.ID == "" && newGroup.Issued != nbgroup.GroupIssuedAPI {
			return status.Errorf(status.InvalidArgument, "%s group without ID set", newGroup.Issued)
		}

		if newGroup.ID == "" && newGroup.Issued == nbgroup.GroupIssuedAPI {
			existingGroup, err := account.FindGroupByName(newGroup.Name)
			if err != nil {
				s, ok := status.FromError(err)
				if !ok || s.ErrorType != status.NotFound {
					return err
				}
			}

			// Avoid duplicate groups only for the API issued groups.
			// Integration or JWT groups can be duplicated as they are coming from the IdP that we don't have control of.
			if existingGroup != nil {
				return status.Errorf(status.AlreadyExists, "group with name %s already exists", newGroup.Name)
			}

			newGroup.ID = xid.New().String()
		}

		for _, peerID := range newGroup.Peers {
			if account.Peers[peerID] == nil {
				return status.Errorf(status.InvalidArgument, "peer with ID \"%s\" not found", peerID)
			}
		}

		oldGroup := account.Groups[newGroup.ID]
		account.Groups[newGroup.ID] = newGroup

		events := am.prepareGroupEvents(ctx, userID, accountID, newGroup, oldGroup, account)
		eventsToStore = append(eventsToStore, events...)
	}

	newGroupIDs := make([]string, 0, len(newGroups))
	for _, newGroup := range newGroups {
		newGroupIDs = append(newGroupIDs, newGroup.ID)
	}

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	if areGroupChangesAffectPeers(account, newGroupIDs) {
		am.updateAccountPeers(ctx, account)
	}

	for _, storeEvent := range eventsToStore {
		storeEvent()
	}

	return nil
}

// prepareGroupEvents prepares a list of event functions to be stored.
func (am *DefaultAccountManager) prepareGroupEvents(ctx context.Context, userID string, accountID string, newGroup, oldGroup *nbgroup.Group, account *Account) []func() {
	var eventsToStore []func()

	addedPeers := make([]string, 0)
	removedPeers := make([]string, 0)

	if oldGroup != nil {
		addedPeers = difference(newGroup.Peers, oldGroup.Peers)
		removedPeers = difference(oldGroup.Peers, newGroup.Peers)
	} else {
		addedPeers = append(addedPeers, newGroup.Peers...)
		eventsToStore = append(eventsToStore, func() {
			am.StoreEvent(ctx, userID, newGroup.ID, accountID, activity.GroupCreated, newGroup.EventMeta())
		})
	}

	for _, p := range addedPeers {
		peer := account.Peers[p]
		if peer == nil {
			log.WithContext(ctx).Errorf("peer %s not found under account %s while saving group", p, accountID)
			continue
		}
		peerCopy := peer // copy to avoid closure issues
		eventsToStore = append(eventsToStore, func() {
			am.StoreEvent(ctx, userID, peerCopy.ID, accountID, activity.GroupAddedToPeer,
				map[string]any{
					"group": newGroup.Name, "group_id": newGroup.ID, "peer_ip": peerCopy.IP.String(),
					"peer_fqdn": peerCopy.FQDN(am.GetDNSDomain()),
				})
		})
	}

	for _, p := range removedPeers {
		peer := account.Peers[p]
		if peer == nil {
			log.WithContext(ctx).Errorf("peer %s not found under account %s while saving group", p, accountID)
			continue
		}
		peerCopy := peer // copy to avoid closure issues
		eventsToStore = append(eventsToStore, func() {
			am.StoreEvent(ctx, userID, peerCopy.ID, accountID, activity.GroupRemovedFromPeer,
				map[string]any{
					"group": newGroup.Name, "group_id": newGroup.ID, "peer_ip": peerCopy.IP.String(),
					"peer_fqdn": peerCopy.FQDN(am.GetDNSDomain()),
				})
		})
	}

	return eventsToStore
}

// difference returns the elements in `a` that aren't in `b`.
func difference(a, b []string) []string {
	mb := make(map[string]struct{}, len(b))
	for _, x := range b {
		mb[x] = struct{}{}
	}
	var diff []string
	for _, x := range a {
		if _, found := mb[x]; !found {
			diff = append(diff, x)
		}
	}
	return diff
}

// DeleteGroup object of the peers.
func (am *DefaultAccountManager) DeleteGroup(ctx context.Context, accountId, userId, groupID string) error {
	unlock := am.Store.AcquireWriteLockByUID(ctx, accountId)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountId)
	if err != nil {
		return err
	}

	group, ok := account.Groups[groupID]
	if !ok {
		return nil
	}

	allGroup, err := account.GetGroupAll()
	if err != nil {
		return err
	}

	if allGroup.ID == groupID {
		return status.Errorf(status.InvalidArgument, "deleting group ALL is not allowed")
	}

	if err = validateDeleteGroup(account, group, userId); err != nil {
		return err
	}
	delete(account.Groups, groupID)

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	am.StoreEvent(ctx, userId, groupID, accountId, activity.GroupDeleted, group.EventMeta())

	return nil
}

// DeleteGroups deletes groups from an account.
// Note: This function does not acquire the global lock.
// It is the caller's responsibility to ensure proper locking is in place before invoking this method.
//
// If an error occurs while deleting a group, the function skips it and continues deleting other groups.
// Errors are collected and returned at the end.
func (am *DefaultAccountManager) DeleteGroups(ctx context.Context, accountId, userId string, groupIDs []string) error {
	account, err := am.Store.GetAccount(ctx, accountId)
	if err != nil {
		return err
	}

	var allErrors error

	deletedGroups := make([]*nbgroup.Group, 0, len(groupIDs))
	for _, groupID := range groupIDs {
		group, ok := account.Groups[groupID]
		if !ok {
			continue
		}

		if err := validateDeleteGroup(account, group, userId); err != nil {
			allErrors = errors.Join(allErrors, fmt.Errorf("failed to delete group %s: %w", groupID, err))
			continue
		}

		delete(account.Groups, groupID)
		deletedGroups = append(deletedGroups, group)
	}

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	for _, g := range deletedGroups {
		am.StoreEvent(ctx, userId, g.ID, accountId, activity.GroupDeleted, g.EventMeta())
	}

	return allErrors
}

// ListGroups objects of the peers
func (am *DefaultAccountManager) ListGroups(ctx context.Context, accountID string) ([]*nbgroup.Group, error) {
	unlock := am.Store.AcquireWriteLockByUID(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return nil, err
	}

	groups := make([]*nbgroup.Group, 0, len(account.Groups))
	for _, item := range account.Groups {
		groups = append(groups, item)
	}

	return groups, nil
}

// GroupAddPeer appends peer to the group
func (am *DefaultAccountManager) GroupAddPeer(ctx context.Context, accountID, groupID, peerID string) error {
	unlock := am.Store.AcquireWriteLockByUID(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return err
	}

	group, ok := account.Groups[groupID]
	if !ok {
		return status.Errorf(status.NotFound, "group with ID %s not found", groupID)
	}

	add := true
	for _, itemID := range group.Peers {
		if itemID == peerID {
			add = false
			break
		}
	}
	if add {
		group.Peers = append(group.Peers, peerID)
	}

	account.Network.IncSerial()
	if err = am.Store.SaveAccount(ctx, account); err != nil {
		return err
	}

	if areGroupChangesAffectPeers(account, []string{group.ID}) {
		am.updateAccountPeers(ctx, account)
	}

	return nil
}

// GroupDeletePeer removes peer from the group
func (am *DefaultAccountManager) GroupDeletePeer(ctx context.Context, accountID, groupID, peerID string) error {
	unlock := am.Store.AcquireWriteLockByUID(ctx, accountID)
	defer unlock()

	account, err := am.Store.GetAccount(ctx, accountID)
	if err != nil {
		return err
	}

	group, ok := account.Groups[groupID]
	if !ok {
		return status.Errorf(status.NotFound, "group with ID %s not found", groupID)
	}

	account.Network.IncSerial()
	for i, itemID := range group.Peers {
		if itemID == peerID {
			group.Peers = append(group.Peers[:i], group.Peers[i+1:]...)
			if err := am.Store.SaveAccount(ctx, account); err != nil {
				return err
			}
		}
	}

	if areGroupChangesAffectPeers(account, []string{group.ID}) {
		am.updateAccountPeers(ctx, account)
	}

	return nil
}

func validateDeleteGroup(account *Account, group *nbgroup.Group, userID string) error {
	// disable a deleting integration group if the initiator is not an admin service user
	if group.Issued == nbgroup.GroupIssuedIntegration {
		executingUser := account.Users[userID]
		if executingUser == nil {
			return status.Errorf(status.NotFound, "user not found")
		}
		if executingUser.Role != UserRoleAdmin || !executingUser.IsServiceUser {
			return status.Errorf(status.PermissionDenied, "only service users with admin power can delete integration group")
		}
	}

	if isLinked, linkedRoute := isGroupLinkedToRoute(account.Routes, group.ID); isLinked {
		return &GroupLinkError{"route", string(linkedRoute.NetID)}
	}

	if isLinked, linkedDns := isGroupLinkedToDns(account.NameServerGroups, group.ID); isLinked {
		return &GroupLinkError{"name server groups", linkedDns.Name}
	}

	if isLinked, linkedPolicy := isGroupLinkedToPolicy(account.Policies, group.ID); isLinked {
		return &GroupLinkError{"policy", linkedPolicy.Name}
	}

	if isLinked, linkedSetupKey := isGroupLinkedToSetupKey(account.SetupKeys, group.ID); isLinked {
		return &GroupLinkError{"setup key", linkedSetupKey.Name}
	}

	if isLinked, linkedUser := isGroupLinkedToUser(account.Users, group.ID); isLinked {
		return &GroupLinkError{"user", linkedUser.Id}
	}

	if slices.Contains(account.DNSSettings.DisabledManagementGroups, group.ID) {
		return &GroupLinkError{"disabled DNS management groups", group.Name}
	}

	if account.Settings.Extra != nil {
		if slices.Contains(account.Settings.Extra.IntegratedValidatorGroups, group.ID) {
			return &GroupLinkError{"integrated validator", group.Name}
		}
	}

	return nil
}

// isGroupLinkedToRoute checks if a group is linked to any route in the account.
func isGroupLinkedToRoute(routes map[route.ID]*route.Route, groupID string) (bool, *route.Route) {
	for _, r := range routes {
		if slices.Contains(r.Groups, groupID) || slices.Contains(r.PeerGroups, groupID) {
			return true, r
		}
	}
	return false, nil
}

// isGroupLinkedToPolicy checks if a group is linked to any policy in the account.
func isGroupLinkedToPolicy(policies []*Policy, groupID string) (bool, *Policy) {
	for _, policy := range policies {
		for _, rule := range policy.Rules {
			if slices.Contains(rule.Sources, groupID) || slices.Contains(rule.Destinations, groupID) {
				return true, policy
			}
		}
	}
	return false, nil
}

// isGroupLinkedToDns checks if a group is linked to any nameserver group in the account.
func isGroupLinkedToDns(nameServerGroups map[string]*nbdns.NameServerGroup, groupID string) (bool, *nbdns.NameServerGroup) {
	for _, dns := range nameServerGroups {
		for _, g := range dns.Groups {
			if g == groupID {
				return true, dns
			}
		}
	}
	return false, nil
}

// isGroupLinkedToSetupKey checks if a group is linked to any setup key in the account.
func isGroupLinkedToSetupKey(setupKeys map[string]*SetupKey, groupID string) (bool, *SetupKey) {
	for _, setupKey := range setupKeys {
		if slices.Contains(setupKey.AutoGroups, groupID) {
			return true, setupKey
		}
	}
	return false, nil
}

// isGroupLinkedToUser checks if a group is linked to any user in the account.
func isGroupLinkedToUser(users map[string]*User, groupID string) (bool, *User) {
	for _, user := range users {
		if slices.Contains(user.AutoGroups, groupID) {
			return true, user
		}
	}
	return false, nil
}

// anyGroupHasPeers checks if any of the given groups in the account have peers.
func anyGroupHasPeers(account *Account, groupIDs []string) bool {
	for _, groupID := range groupIDs {
		if group, exists := account.Groups[groupID]; exists && group.HasPeers() {
			return true
		}
	}
	return false
}

func areGroupChangesAffectPeers(account *Account, groupIDs []string) bool {
	for _, groupID := range groupIDs {
		if linked, _ := isGroupLinkedToDns(account.NameServerGroups, groupID); linked {
			return true
		}
		if linked, _ := isGroupLinkedToPolicy(account.Policies, groupID); linked {
			return true
		}
		if linked, _ := isGroupLinkedToRoute(account.Routes, groupID); linked {
			return true
		}
	}

	return false
}