package room

import (
	"context"
	"database/sql"
	"errors"

	"golang.org/x/crypto/bcrypt"
)

type Service struct {
	store *Store
}

func NewService(store *Store) *Service { return &Service{store: store} }

func (s *Service) Store() *Store { return s.store }

func (s *Service) GetRoom(ctx context.Context, name string) (*Room, error) {
	if s.store == nil || s.store.db == nil {
		return nil, errors.New("room store not configured")
	}
	return s.store.GetRoom(ctx, name)
}

func (s *Service) CreateRoom(ctx context.Context, name, creator string, settings *RoomSettings) (*Room, error) {
	if name == "" {
		return nil, errors.New("room name required")
	}
	if creator == "" {
		return nil, errors.New("creator required")
	}
	r := NewRoom(name, creator)
	if settings != nil {
		r.Settings = settings
		r.IsPublic = settings.IsPublic
		r.RequireApproval = settings.RequireApproval
		if settings.MaxMembers > 0 {
			r.MaxMembers = settings.MaxMembers
		}
	}
	if err := s.store.CreateRoom(ctx, r); err != nil {
		return nil, err
	}
	creatorMember := NewMember(name, creator, RoleCreator)
	if err := s.store.UpsertMember(ctx, creatorMember); err != nil {
		return nil, err
	}
	return r, nil
}

func (s *Service) JoinRoom(ctx context.Context, roomName, username string, password string) (*RoomMember, error) {
	r, err := s.store.GetRoom(ctx, roomName)
	if err != nil {
		return nil, err
	}
	if r.Status == RoomBanned {
		return nil, errors.New("room is banned")
	}
	if r.Status == RoomClosed {
		return nil, errors.New("room is closed")
	}
	if r.PasswordHash != "" {
		if err := verifyRoomPassword(password, r.PasswordHash); err != nil {
			return nil, err
		}
	}
	if cnt, _ := s.store.CountMembers(ctx, roomName); cnt >= r.MaxMembers && r.MaxMembers > 0 {
		return nil, errors.New("room is full")
	}
	member, err := s.store.GetMember(ctx, roomName, username)
	if err == nil && member.Status == MemberActive {
		return member, nil
	}
	if err == nil && member.Status == MemberBanned {
		return nil, errors.New("you are banned from this room")
	}
	if err == nil && member.Status == MemberPending {
		return nil, errors.New("join request pending approval")
	}
	newMember := NewMember(roomName, username, RoleMember)
	if r.RequireApproval {
		newMember.Status = MemberPending
	}
	if s.store != nil {
		_ = s.store.UpsertMember(ctx, newMember)
	}
	return newMember, nil
}

func (s *Service) GetMember(ctx context.Context, room, userID string) (*RoomMember, error) {
	return s.store.GetMember(ctx, room, userID)
}

func (s *Service) EnsurePermission(ctx context.Context, room, userID string, perm RoomPermission) error {
	if s.store == nil || s.store.db == nil {
		return nil
	}
	r, err := s.store.GetRoom(ctx, room)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return errors.New("room not found")
		}
		return err
	}
	if r.Status == RoomBanned {
		return errors.New("room is banned")
	}
	if r.Status == RoomClosed && perm != PermViewMembers && perm != PermViewChatHistory {
		return errors.New("room is closed")
	}
	m, err := s.store.GetMember(ctx, room, userID)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			if r.IsPublic || r.Settings.AllowGuestJoin {
				guest := NewMember(room, userID, RoleGuest)
				if guest.HasPermission(perm, r.Settings) {
					return nil
				}
			}
			return errors.New("not a member of this room")
		}
		return err
	}
	if m.Status != MemberActive {
		return errors.New("member not active")
	}
	if !m.HasPermission(perm, r.Settings) {
		return errors.New("permission denied: " + perm.String())
	}
	return nil
}

func (s *Service) CheckPermission(ctx context.Context, room, userID string, perm RoomPermission) bool {
	return s.EnsurePermission(ctx, room, userID, perm) == nil
}

func (s *Service) ListMembers(ctx context.Context, room string) ([]*RoomMember, error) {
	return s.store.ListMembers(ctx, room)
}

func (s *Service) UpdateMemberRole(ctx context.Context, room, actorID, targetID string, newRole RoomRole) error {
	if newRole == RoleCreator {
		return errors.New("cannot assign creator role")
	}
	roomObj, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermManageMembers, roomObj.Settings) {
		return errors.New("permission denied: manage members")
	}
	if !actor.Role.CanManage(newRole) {
		return errors.New("cannot manage role higher than yours")
	}
	target, err := s.store.GetMember(ctx, room, targetID)
	if err != nil {
		return errors.New("target not in room")
	}
	if target.Role == RoleCreator {
		return errors.New("cannot change creator role")
	}
	if !actor.Role.CanManage(target.Role) {
		return errors.New("cannot manage member with higher or equal role")
	}
	target.Role = newRole
	return s.store.UpsertMember(ctx, target)
}

func (s *Service) UpdateMemberPermissions(ctx context.Context, room, actorID, targetID string, added, removed uint64, isAdmin bool) error {
	roomObj, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermManagePermissions, roomObj.Settings) {
		return errors.New("permission denied: manage permissions")
	}
	target, err := s.store.GetMember(ctx, room, targetID)
	if err != nil {
		return errors.New("target not in room")
	}
	if !actor.Role.CanManage(target.Role) {
		return errors.New("cannot manage this member")
	}
	if isAdmin {
		if target.Role != RoleAdmin && target.Role != RoleCreator {
			return errors.New("admin permissions only for admin/creator")
		}
		target.AdminAdded = added
		target.AdminRemoved = removed
	} else {
		target.AddedPerms = added
		target.RemovedPerms = removed
	}
	return s.store.UpsertMember(ctx, target)
}

func (s *Service) KickMember(ctx context.Context, room, actorID, targetID string) error {
	roomObj, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermRemoveMembers, roomObj.Settings) {
		return errors.New("permission denied: remove members")
	}
	target, err := s.store.GetMember(ctx, room, targetID)
	if err != nil {
		return errors.New("target not in room")
	}
	if target.Role == RoleCreator {
		return errors.New("cannot kick creator")
	}
	if !actor.Role.CanManage(target.Role) {
		return errors.New("cannot kick higher role")
	}
	return s.store.RemoveMember(ctx, room, targetID)
}

func (s *Service) BanMember(ctx context.Context, room, actorID, targetID string) error {
	if err := s.KickMember(ctx, room, actorID, targetID); err != nil {
		return err
	}
	banned := NewMember(room, targetID, RoleGuest)
	banned.Status = MemberBanned
	return s.store.UpsertMember(ctx, banned)
}

func (s *Service) LeaveRoom(ctx context.Context, room, userID string) error {
	m, err := s.store.GetMember(ctx, room, userID)
	if err != nil {
		return err
	}
	if m.Role == RoleCreator {
		return errors.New("creator cannot leave, transfer ownership or delete room")
	}
	return s.store.RemoveMember(ctx, room, userID)
}

func (s *Service) UpdateRoomSettings(ctx context.Context, room, actorID string, newSettings *RoomSettings) error {
	r, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermManageRoom, r.Settings) {
		return errors.New("permission denied: manage room")
	}
	return s.store.UpdateRoomSettings(ctx, room, newSettings)
}

// HashRoomPassword 使用 bcrypt 哈希房间密码。
func HashRoomPassword(password string) (string, error) {
	if password == "" {
		return "", nil
	}
	b, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return "", err
	}
	return string(b), nil
}

func verifyRoomPassword(input, hash string) error {
	if hash == "" {
		return nil
	}
	if err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(input)); err != nil {
		return errors.New("invalid room password")
	}
	return nil
}

// ApproveJoin 将 pending 成员升级为 active member，需 PermManageMembers 权限。
func (s *Service) ApproveJoin(ctx context.Context, room, actorID, targetID string) error {
	roomObj, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermManageMembers, roomObj.Settings) {
		return errors.New("permission denied: manage members")
	}
	target, err := s.store.GetMember(ctx, room, targetID)
	if err != nil {
		return errors.New("target not found")
	}
	if target.Status != MemberPending {
		return errors.New("member is not pending approval")
	}
	target.Status = MemberActive
	return s.store.UpsertMember(ctx, target)
}

// RejectJoin 删除一个 pending 成员的加入请求。
func (s *Service) RejectJoin(ctx context.Context, room, actorID, targetID string) error {
	roomObj, err := s.store.GetRoom(ctx, room)
	if err != nil {
		return err
	}
	actor, err := s.store.GetMember(ctx, room, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if !actor.HasPermission(PermManageMembers, roomObj.Settings) {
		return errors.New("permission denied: manage members")
	}
	target, err := s.store.GetMember(ctx, room, targetID)
	if err != nil {
		return errors.New("target not found")
	}
	if target.Status != MemberPending {
		return errors.New("member is not pending approval")
	}
	return s.store.RemoveMember(ctx, room, targetID)
}

// TransferOwnership 将房间所有权从当前 creator 转移给目标 active 成员。
func (s *Service) TransferOwnership(ctx context.Context, roomName, actorID, targetID string) error {
	r, err := s.store.GetRoom(ctx, roomName)
	if err != nil {
		return err
	}
	_ = r
	actor, err := s.store.GetMember(ctx, roomName, actorID)
	if err != nil {
		return errors.New("actor not in room")
	}
	if actor.Role != RoleCreator {
		return errors.New("only creator can transfer ownership")
	}
	target, err := s.store.GetMember(ctx, roomName, targetID)
	if err != nil {
		return errors.New("target not in room")
	}
	if target.Status != MemberActive {
		return errors.New("target must be an active member")
	}
	if target.Role == RoleCreator {
		return errors.New("target is already the creator")
	}
	// 更新房间表的 creator 字段
	if err := s.store.UpdateRoomCreator(ctx, roomName, targetID); err != nil {
		return err
	}
	// 升级 target 为 creator
	target.Role = RoleCreator
	if err := s.store.UpsertMember(ctx, target); err != nil {
		return err
	}
	// 降级 actor 为 admin
	actor.Role = RoleAdmin
	return s.store.UpsertMember(ctx, actor)
}