package gift

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"time"

	kratoserrors "github.com/go-kratos/kratos/v3/errors"

	bizlive "kra/internal/biz/live"
)

var (
	ErrNotFound            = kratoserrors.NotFound("GIFT_NOT_FOUND", "gift not found")
	ErrNameExists          = kratoserrors.BadRequest("GIFT_NAME_EXISTS", "gift name already exists")
	ErrInvalid             = kratoserrors.BadRequest("GIFT_INVALID", "invalid gift data")
	ErrLastEnabled         = kratoserrors.BadRequest("GIFT_LAST_ENABLED", "at least one enabled gift is required")
	ErrInsufficientBalance = kratoserrors.BadRequest("GIFT_INSUFFICIENT_BALANCE", "insufficient diamond balance")
	ErrSendNotAllowed      = kratoserrors.BadRequest("GIFT_SEND_NOT_ALLOWED", "gift cannot be sent")
)

// InsufficientBalanceError preserves the wallet snapshot needed by clients
// to decide whether to open the recharge flow. It unwraps to the stable
// ErrInsufficientBalance reason so existing errors.Is checks keep working.
type InsufficientBalanceError struct {
	Required int64
	Balance  int64
	Missing  int64
}

func (e *InsufficientBalanceError) Error() string {
	if e == nil {
		return ErrInsufficientBalance.Error()
	}
	return fmt.Sprintf("insufficient diamond balance: need %d, have %d, missing %d", e.Required, e.Balance, e.Missing)
}

func (e *InsufficientBalanceError) Unwrap() error { return ErrInsufficientBalance }

type Gift struct {
	ID                      uint
	Name, Icon, Description string
	Price                   int64
	Tiers                   []int
	Sort                    int
	Enabled                 bool
	SendCount               int64
	CreatedAt, UpdatedAt    time.Time
}
type Send struct {
	ID                                       uint
	SerialNo                                 string
	UserID                                   uint
	Username, Nickname                       string
	RoomID                                   *uint
	RoomName                                 string
	RoomDeleted                              bool
	AnchorUserID                             uint
	AnchorName                               string
	GiftID                                   *uint
	GiftName, GiftIcon                       string
	GiftPrice                                int64
	Quantity                                 int
	DiamondTotal, RateCents, EquivalentCents int64
	CreatedAt                                time.Time
}
type Filter struct {
	Name               string
	MinPrice, MaxPrice int64
	Enabled            *bool
}
type SendFilter struct {
	RoomName, AnchorName, UserKeyword string
	GiftID                            uint
	CreatedAt                         []time.Time
}
type ListOptions struct {
	Offset, Limit int
	OrderBy       string
}
type Summary struct{ Count, Diamonds, AmountCents int64 }
type Repo interface {
	List(context.Context, Filter, ListOptions) ([]*Gift, int64, error)
	Get(context.Context, uint) (*Gift, error)
	Save(context.Context, *Gift) (*Gift, error)
	Delete(context.Context, uint) error
	SetEnabled(context.Context, uint, bool) error
	SaveSort(context.Context, map[uint]int) error
	ListSends(context.Context, SendFilter, ListOptions) ([]*Send, int64, *Summary, error)
	Send(context.Context, uint, uint, uint, int) (*Send, error)
}
type Notifier interface {
	GiftSent(context.Context, *Send)
}
type roomAvailability interface {
	IsLive(context.Context, uint) (bool, error)
}
type Usecase struct {
	repo     Repo
	notifier Notifier
	rooms    roomAvailability
}

func NewUsecase(repo Repo, notifier Notifier, rooms *bizlive.RoomUsecase) *Usecase {
	return newUsecase(repo, notifier, rooms)
}

func newUsecase(repo Repo, notifier Notifier, rooms roomAvailability) *Usecase {
	return &Usecase{repo: repo, notifier: notifier, rooms: rooms}
}
func (uc *Usecase) List(ctx context.Context, f Filter, o ListOptions) ([]*Gift, int64, error) {
	f.Name = strings.TrimSpace(f.Name)
	return uc.repo.List(ctx, f, normalize(o))
}
func (uc *Usecase) Get(ctx context.Context, id uint) (*Gift, error) {
	if id == 0 {
		return nil, ErrNotFound
	}
	return uc.repo.Get(ctx, id)
}
func (uc *Usecase) Save(ctx context.Context, item *Gift) (*Gift, error) {
	if err := validate(item); err != nil {
		return nil, err
	}
	return uc.repo.Save(ctx, item)
}
func (uc *Usecase) Delete(ctx context.Context, id uint) error { return uc.repo.Delete(ctx, id) }
func (uc *Usecase) SetEnabled(ctx context.Context, id uint, enabled bool) error {
	return uc.repo.SetEnabled(ctx, id, enabled)
}
func (uc *Usecase) SaveSort(ctx context.Context, values map[uint]int) error {
	for id, v := range values {
		if id == 0 || v < 0 || v > 9999 {
			return ErrInvalid
		}
	}
	return uc.repo.SaveSort(ctx, values)
}
func (uc *Usecase) ListSends(ctx context.Context, f SendFilter, o ListOptions) ([]*Send, int64, *Summary, error) {
	return uc.repo.ListSends(ctx, f, normalize(o))
}
func (uc *Usecase) Send(ctx context.Context, userID, roomID, giftID uint, quantity int) (*Send, error) {
	if userID == 0 || roomID == 0 || giftID == 0 || quantity < 1 || quantity > 9999 {
		return nil, ErrSendNotAllowed
	}
	if uc.rooms == nil {
		return nil, ErrSendNotAllowed
	}
	live, err := uc.rooms.IsLive(ctx, roomID)
	if err != nil || !live {
		return nil, ErrSendNotAllowed
	}
	result, err := uc.repo.Send(ctx, userID, roomID, giftID, quantity)
	if err != nil {
		return nil, err
	}
	if uc.notifier != nil {
		uc.notifier.GiftSent(ctx, result)
	}
	return result, nil
}
func normalize(o ListOptions) ListOptions {
	if o.Offset < 0 {
		o.Offset = 0
	}
	if o.Limit < 1 || o.Limit > 100 {
		o.Limit = 10
	}
	return o
}
func validate(item *Gift) error {
	if item == nil {
		return ErrInvalid
	}
	item.Name = strings.TrimSpace(item.Name)
	item.Icon = strings.TrimSpace(item.Icon)
	item.Description = strings.TrimSpace(item.Description)
	if len([]rune(item.Name)) < 1 || len([]rune(item.Name)) > 12 || item.Icon == "" || item.Price < 1 || item.Price > 99999 || len([]rune(item.Description)) > 50 || item.Sort < 0 || item.Sort > 9999 || len(item.Tiers) < 1 || len(item.Tiers) > 6 {
		return ErrInvalid
	}
	seen := map[int]struct{}{}
	for _, v := range item.Tiers {
		if v < 1 || v > 9999 {
			return ErrInvalid
		}
		if _, ok := seen[v]; ok {
			return ErrInvalid
		}
		seen[v] = struct{}{}
	}
	sort.Ints(item.Tiers)
	return nil
}