//
//  KBVipPay.m
//  keyBoard
//
//  Created by Mac on 2025/11/14.
//

#import "KBVipPay.h"
#import "KBVipPayHeaderView.h"
#import "KBVipSubscribeCell.h"
#import "KBVipReviewListCell.h"
#import "PayVM.h"
#import "KBPayProductModel.h"
#import "KBBizCode.h"
#import "keyBoard-Swift.h"
#import <MJExtension/MJExtension.h>

static NSString * const kKBVipHeaderId = @"kKBVipHeaderId";
static NSString * const kKBVipSubscribeCellId = @"kKBVipSubscribeCellId";
static NSString * const kKBVipReviewListCellId = @"kKBVipReviewListCellId";

@interface KBVipPay () <UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>
@property (nonatomic, strong) UICollectionView *collectionView;   // 主列表（竖向滚动）
@property (nonatomic, strong) NSArray<KBPayProductModel *> *plans;     // 订阅方案数组
@property (nonatomic, assign) NSInteger selectedIndex;            // 当前选中的方案索引
@property (nonatomic, strong) UIButton *closeButton;            // 当前选中的方案索引
@property (nonatomic, strong) UIButton *restoreButton;
@property (nonatomic, strong) UIImageView *bgImageView;  // 全屏背景图
// Header 自适应测量
@property (nonatomic, strong) KBVipPayHeaderView *sizingHeader;
@property (nonatomic, assign) CGFloat headerHeight;
// 底部支付与协议
@property (nonatomic, strong) UIButton *payButton;            // 支付按钮（背景图）
@property (nonatomic, strong) UILabel *agreementLabel;        // 协议提示
@property (nonatomic, strong) UIButton *agreementButton;      // 《Embership Agreement》
@property (nonatomic, strong) PayVM *payVM;
@property (nonatomic, copy, nullable) NSString *pendingProductId;
@property (nonatomic, assign) BOOL pendingAutoPurchase;
@property (nonatomic, assign) BOOL hasTriggeredAutoPurchase;
@property (nonatomic, assign) BOOL viewVisible;
@property (nonatomic, copy, nullable) NSArray *prefillProductsJSON;
@property (nonatomic, assign) NSInteger prefillSelectedIndex;
@property (nonatomic, assign) BOOL didApplyPrefillPlans;

@end

@implementation KBVipPay

- (void)viewDidLoad {
    [super viewDidLoad];
    // 标题与导航样式
//    self.kb_titleLabel.text = @"VIP";
//    self.kb_navView.backgroundColor = [UIColor clearColor];
    self.view.backgroundColor = [UIColor colorWithHex:0xF6F7FB];
    self.kb_enableCustomNavBar = NO;
    self.bgImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"pay_vipbg_icon"]];
    self.bgImageView.contentMode = UIViewContentModeScaleAspectFill;
    [self.view addSubview:self.bgImageView];
    [self.bgImageView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.top.right.equalTo(self.view);
        make.height.mas_equalTo(224);
    }];
    self.payVM = [PayVM new];
    self.plans = @[];
    self.selectedIndex = NSNotFound;
    self.prefillSelectedIndex = NSNotFound;
    
    // 组装主列表
    [self.view addSubview:self.collectionView];
    // 先添加底部按钮与协议，再让 collectionView 的底部在按钮之上
    [self.view addSubview:self.payButton];
    [self.view addSubview:self.agreementLabel];
    [self.view addSubview:self.agreementButton];
    [self.payButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(self.view).offset(24);
        make.right.equalTo(self.view).offset(-24);
        make.bottom.equalTo(self.agreementLabel.mas_top).offset(-14);
        make.height.mas_equalTo(58);
    }];
    [self.agreementButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.centerX.equalTo(self.view);
        make.bottom.equalTo(self.view).offset(-KB_SAFE_BOTTOM - 15);
    }];
    [self.agreementLabel mas_makeConstraints:^(MASConstraintMaker *make) {
        make.centerX.equalTo(self.view);
        make.bottom.equalTo(self.agreementButton.mas_top).offset(0);
    }];
    [self.collectionView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.equalTo(self.view);
        make.top.equalTo(self.view).offset(0);
        make.bottom.equalTo(self.payButton.mas_top).offset(-16);
    }];
    [self.view addSubview:self.closeButton];
    [self.closeButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view).offset(KB_NAV_TOTAL_HEIGHT - 30);
        make.left.equalTo(self.view).offset(15);
        make.width.height.mas_equalTo(36);
    }];
    [self.view addSubview:self.restoreButton];
    [self.restoreButton mas_makeConstraints:^(MASConstraintMaker *make) {
        make.centerY.equalTo(self.closeButton);
        make.right.equalTo(self.view).offset(-15);
        make.width.mas_equalTo(123);
        make.height.mas_equalTo(32);
    }];
    
    // 预计算 Header 高度（由内部约束决定）
    self.headerHeight = [self kb_calcHeaderHeightForWidth:KB_SCREEN_WIDTH];
    BOOL appliedPrefill = [self kb_applyPrefillPlansIfPossible];
    [self.collectionView reloadData];
    [self selectCurrentPlanAnimated:NO];
    if (!appliedPrefill) {
        [self fetchSubscriptionPlans];
    }
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    self.viewVisible = YES;
    [self selectCurrentPlanAnimated:NO];
    [self kb_triggerAutoPurchaseIfNeeded];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    self.viewVisible = NO;
}

#pragma mark - Deep Link Support

- (void)configureWithProductId:(NSString *)productId autoPurchase:(BOOL)autoPurchase {
    self.pendingProductId = productId.length ? [productId copy] : nil;
    self.pendingAutoPurchase = autoPurchase;
    self.hasTriggeredAutoPurchase = NO;
    [self kb_applyPendingPrefillIfNeeded];
    [self kb_triggerAutoPurchaseIfNeeded];
}

- (void)configureWithProductId:(nullable NSString *)productId
                  autoPurchase:(BOOL)autoPurchase
            prefillProductsJSON:(nullable NSArray *)productsJSON
                 selectedIndex:(NSInteger)selectedIndex {
    self.pendingProductId = productId.length ? [productId copy] : nil;
    self.pendingAutoPurchase = autoPurchase;
    self.hasTriggeredAutoPurchase = NO;
    self.prefillProductsJSON = [productsJSON isKindOfClass:NSArray.class] ? [productsJSON copy] : nil;
    self.prefillSelectedIndex = selectedIndex;
    self.didApplyPrefillPlans = NO;
    if (self.isViewLoaded) {
        BOOL ok = [self kb_applyPrefillPlansIfPossible];
        if (ok) {
            [self.collectionView reloadData];
            [self selectCurrentPlanAnimated:NO];
        }
    }
    [self kb_triggerAutoPurchaseIfNeeded];
}

#pragma mark - Data
- (void)fetchSubscriptionPlans {
    __weak typeof(self) weakSelf = self;
    [self.payVM fetchSubscriptionProductsNeedShow:YES completion:^(NSInteger sta, NSString * _Nullable msg, NSArray<KBPayProductModel *> * _Nullable products) {
        dispatch_async(dispatch_get_main_queue(), ^{
            __strong typeof(weakSelf) self = weakSelf;
            if (!self) { return; }
            if (sta != KBBizCodeSuccess || ![products isKindOfClass:NSArray.class]) {
                self.plans = @[];
                self.selectedIndex = NSNotFound;
                [self.collectionView reloadData];
                NSString *tip = msg.length ? msg : KBLocalized(@"Failed to load products");
                if (tip.length) { [KBHUD showInfo:tip]; }
                return;
            }
            self.plans = products ?: @[];
            self.selectedIndex = self.plans.count > 0 ? 0 : NSNotFound;
            [self.collectionView reloadData];
            [self prepareStoreKitWithPlans:self.plans];
            [self kb_applyPendingPrefillIfNeeded];
            [self selectCurrentPlanAnimated:NO];
            [self kb_triggerAutoPurchaseIfNeeded];
        });
    }];
}

- (BOOL)kb_applyPrefillPlansIfPossible {
    if (self.didApplyPrefillPlans) {
        return (self.plans.count > 0);
    }
    if (![self.prefillProductsJSON isKindOfClass:NSArray.class] || self.prefillProductsJSON.count == 0) {
        return NO;
    }
    NSArray<KBPayProductModel *> *models = [KBPayProductModel mj_objectArrayWithKeyValuesArray:self.prefillProductsJSON];
    if (![models isKindOfClass:NSArray.class] || models.count == 0) {
        return NO;
    }
    self.didApplyPrefillPlans = YES;
    self.plans = models;
    NSInteger idx = self.prefillSelectedIndex;
    if (idx != NSNotFound && idx >= 0 && idx < (NSInteger)self.plans.count) {
        self.selectedIndex = idx;
    } else {
        self.selectedIndex = (self.plans.count > 0) ? 0 : NSNotFound;
    }
    [self prepareStoreKitWithPlans:self.plans];
    [self kb_applyPendingPrefillIfNeeded];
    return YES;
}

- (void)prepareStoreKitWithPlans:(NSArray<KBPayProductModel *> *)plans {
    if (![plans isKindOfClass:NSArray.class] || plans.count == 0) { return; }
    NSMutableArray<NSString *> *ids = [NSMutableArray array];
    for (KBPayProductModel *plan in plans) {
        if (![plan isKindOfClass:KBPayProductModel.class]) { continue; }
        if (plan.productId.length) {
            [ids addObject:plan.productId];
        }
    }
    if (ids.count == 0) { return; }
    [[KBStoreKitBridge shared] prepareWithProductIds:ids completion:nil];
}

- (void)selectCurrentPlanAnimated:(BOOL)animated {
    if (self.selectedIndex == NSNotFound) { return; }
    if (self.selectedIndex < 0 || self.selectedIndex >= self.plans.count) { return; }
    NSIndexPath *ip = [NSIndexPath indexPathForItem:self.selectedIndex inSection:1];
    if (!ip) { return; }
    [self.collectionView selectItemAtIndexPath:ip animated:animated scrollPosition:UICollectionViewScrollPositionNone];
    KBVipSubscribeCell *cell = (KBVipSubscribeCell *)[self.collectionView cellForItemAtIndexPath:ip];
    if ([cell isKindOfClass:KBVipSubscribeCell.class]) {
        [cell applySelected:YES animated:animated];
    }
}

- (KBPayProductModel *)currentSelectedPlan {
    if (self.selectedIndex == NSNotFound) { return nil; }
    if (self.selectedIndex < 0 || self.selectedIndex >= self.plans.count) { return nil; }
    id plan = self.plans[self.selectedIndex];
    if (![plan isKindOfClass:KBPayProductModel.class]) { return nil; }
    return plan;
}

- (void)kb_applyPendingPrefillIfNeeded {
    if (self.pendingProductId.length == 0 || self.plans.count == 0) { return; }
    __block NSInteger target = NSNotFound;
    [self.plans enumerateObjectsUsingBlock:^(KBPayProductModel *obj, NSUInteger idx, BOOL *stop) {
        if (![obj isKindOfClass:KBPayProductModel.class]) { return; }
        if ([obj.productId isEqualToString:self.pendingProductId]) {
            target = (NSInteger)idx;
            *stop = YES;
        }
    }];
    if (target != NSNotFound) {
        self.selectedIndex = target;
    }
}

- (void)kb_triggerAutoPurchaseIfNeeded {
    if (!self.pendingAutoPurchase || self.hasTriggeredAutoPurchase || !self.viewVisible) { return; }
    if (![self currentSelectedPlan]) { return; }
    self.hasTriggeredAutoPurchase = YES;
    self.pendingAutoPurchase = NO;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.35 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [self onTapPayButton];
    });
}

- (NSString *)displayTitleForPlan:(KBPayProductModel *)plan {
    if (!plan) { return @""; }
    if (plan.productDescription.length) { return plan.productDescription; }
    NSString *name = plan.name ?: @"";
    NSString *unit = plan.unit ?: @"";
    if (name.length && unit.length) { return [NSString stringWithFormat:@"%@%@", name, unit]; }
    if (name.length) { return name; }
    if (unit.length) { return unit; }
    return KBLocalized(@"Subscription");
}

#pragma mark - Header Height Calc
- (CGFloat)kb_calcHeaderHeightForWidth:(CGFloat)width {
    if (width <= 0) { width = KB_SCREEN_WIDTH; }
    if (!self.sizingHeader) {
        self.sizingHeader = [[KBVipPayHeaderView alloc] initWithFrame:CGRectMake(0, 0, width, 1)];
    }
    // 更新目标宽度并触发布局
    self.sizingHeader.bounds = CGRectMake(0, 0, width, self.sizingHeader.bounds.size.height);
    [self.sizingHeader setNeedsLayout];
    [self.sizingHeader layoutIfNeeded];
    CGSize size = [self.sizingHeader systemLayoutSizeFittingSize:CGSizeMake(width, UILayoutFittingCompressedSize.height)
                                  withHorizontalFittingPriority:UILayoutPriorityRequired
                                        verticalFittingPriority:UILayoutPriorityFittingSizeLevel];
    return MAX(1, ceil(size.height));
}

#pragma mark - Action
- (void)onTapClose{
    [self.navigationController popViewControllerAnimated:true];
}

#pragma mark - Bottom Actions
- (void)onTapPayButton {
    KBPayProductModel *plan = [self currentSelectedPlan];
    if (!plan) {
        [KBHUD showInfo:KBLocalized(@"Please select a product")];
        return;
    }
    NSString *productId = plan.productId;
    if (productId.length == 0) {
        [KBHUD showInfo:KBLocalized(@"Product unavailable")];
        return;
    }
    [KBHUD show];
    __weak typeof(self) weakSelf = self;
    [[KBStoreKitBridge shared] purchaseWithProductId:productId completion:^(BOOL success, NSString * _Nullable message) {
        __strong typeof(weakSelf) self = weakSelf;
//        NSString *tip = message.length ? message : (success ? KBLocalized(@"Payment successful") : KBLocalized(@"Payment failed"));
        [KBHUD dismiss];
//        [KBHUD showInfo:tip];
        [KBHUD showInfo:KBLocalized(message)];
        if (!self || !success) { return; }
        // 刷新 UI 或数据
        [self selectCurrentPlanAnimated:NO];
    }];
}
- (void)agreementButtonAction{
    [KBHUD showInfo:KBLocalized(@"Open agreement")];
}

- (void)onTapRestoreButton {
    [KBHUD show];
    __weak typeof(self) weakSelf = self;
    [[KBStoreKitBridge shared] restorePurchasesWithCompletion:^(BOOL success, NSString * _Nullable message) {
        dispatch_async(dispatch_get_main_queue(), ^{
            __strong typeof(weakSelf) self = weakSelf;
            (void)self;
            [KBHUD dismiss];
            NSString *tip = message.length ? message : (success ? KBLocalized(@"Success") : KBLocalized(@"Failed"));
            [KBHUD showInfo:tip];
        });
    }];
}

#pragma mark - UICollectionView DataSource

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    // 0：头部；1：订阅选项；2：底部横滑好评
    return 3;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    if (section == 1) { return self.plans.count; }
    if (section == 2) { return 1; }
    return 0; // 头部仅使用 header
}

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == 1) {
        KBVipSubscribeCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kKBVipSubscribeCellId forIndexPath:indexPath];
        if (indexPath.item < self.plans.count) {
            KBPayProductModel *plan = self.plans[indexPath.item];
            NSString *title = [self displayTitleForPlan:plan];
            NSString *price = [plan priceDisplayText];
            [cell configTitle:title price:price strike:nil];
            [cell applySelected:(indexPath.item == self.selectedIndex) animated:NO];
        } else {
            [cell configTitle:@"" price:@"" strike:nil];
            [cell applySelected:NO animated:NO];
        }
        return cell;
    } else {
        KBVipReviewListCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kKBVipReviewListCellId forIndexPath:indexPath];
        return cell;
    }
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == 0 && [kind isEqualToString:UICollectionElementKindSectionHeader]) {
        KBVipPayHeaderView *header = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:kKBVipHeaderId forIndexPath:indexPath];
        return header;
    }
    return [UICollectionReusableView new];
}

#pragma mark - UICollectionView Delegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section != 1 || indexPath.item >= self.plans.count) { return; }
    if (self.selectedIndex == indexPath.item) { return; }
    NSInteger old = self.selectedIndex;
    self.selectedIndex = indexPath.item;
    
    KBVipSubscribeCell *newCell = (KBVipSubscribeCell *)[collectionView cellForItemAtIndexPath:indexPath];
    [newCell applySelected:YES animated:YES];
    if (old >= 0 && old < self.plans.count) {
        NSIndexPath *oldIP = [NSIndexPath indexPathForItem:old inSection:1];
        KBVipSubscribeCell *oldCell = (KBVipSubscribeCell *)[collectionView cellForItemAtIndexPath:oldIP];
        [oldCell applySelected:NO animated:YES];
    }
}

- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
    // 兜底：当订阅项第一次出现在屏幕上，强制同步选中样式
    if (indexPath.section == 1 && indexPath.item < self.plans.count && [cell isKindOfClass:KBVipSubscribeCell.class]) {
        BOOL sel = (indexPath.item == self.selectedIndex);
        KBVipSubscribeCell *c = (KBVipSubscribeCell *)cell;
        if (sel) {
            [collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
        }
        [c applySelected:sel animated:NO];
    }
}

#pragma mark - FlowLayout
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    CGFloat w = KB_SCREEN_WIDTH - 32;
    if (indexPath.section == 1) {
        return CGSizeMake(w, KBFit(75 + 6));
    } else {
        return CGSizeMake(w, 140);
    }
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
    if (section == 0) {
        // 动态返回测量好的 Header 高度
        CGFloat w = collectionView.bounds.size.width ?: KB_SCREEN_WIDTH;
        if (self.headerHeight <= 1) { self.headerHeight = [self kb_calcHeaderHeightForWidth:w]; }
        return CGSizeMake(w, self.headerHeight);
    }
    return CGSizeZero;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
    if (section == 1) { return 14; }
    return 0;
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    if (section == 1) {
        // 留出顶部间距，避免第一个订阅 cell 的边框被 header 盖住
        return UIEdgeInsetsMake(16, 16, 10, 16);
    } else if (section == 2) {
        return UIEdgeInsetsMake(10, 16, 20, 16);
    }
    return UIEdgeInsetsZero;
}

#pragma mark - Lazy
- (UICollectionView *)collectionView {
    if (!_collectionView) {
        UICollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
        layout.scrollDirection = UICollectionViewScrollDirectionVertical;
        // 每次宽度变化时让布局失效，便于 header 重算高度
        layout.sectionHeadersPinToVisibleBounds = NO;
        _collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
        _collectionView.backgroundColor = [UIColor clearColor];
        _collectionView.dataSource = self;
        _collectionView.delegate = self;
        _collectionView.alwaysBounceVertical = YES;
            _collectionView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
        [_collectionView registerClass:KBVipPayHeaderView.class forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:kKBVipHeaderId];
        [_collectionView registerClass:KBVipSubscribeCell.class forCellWithReuseIdentifier:kKBVipSubscribeCellId];
        [_collectionView registerClass:KBVipReviewListCell.class forCellWithReuseIdentifier:kKBVipReviewListCellId];
    }
    return _collectionView;
}


- (UIButton *)closeButton {
    if (!_closeButton) {
        _closeButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [_closeButton setImage:[UIImage imageNamed:@"close_white2_icon"] forState:UIControlStateNormal];
        [_closeButton addTarget:self action:@selector(onTapClose) forControlEvents:UIControlEventTouchUpInside];
    }
    return _closeButton;
}

- (UIButton *)restoreButton {
    if (!_restoreButton) {
        _restoreButton = [UIButton buttonWithType:UIButtonTypeCustom];
        _restoreButton.backgroundColor = [[UIColor colorWithHex:0xF6F7FB] colorWithAlphaComponent:0.72];
        _restoreButton.layer.cornerRadius = 8;
        _restoreButton.layer.masksToBounds = YES;
        UIImage *icon = [UIImage imageNamed:@"pay_resh_icon"];
        [_restoreButton setImage:icon forState:UIControlStateNormal];
        [_restoreButton setTitle:KBLocalized(@"Resume Purchase") forState:UIControlStateNormal];
        [_restoreButton setTitleColor:[UIColor colorWithHex:0x02BEAC] forState:UIControlStateNormal];
        _restoreButton.titleLabel.font = [KBFont medium:10];
        _restoreButton.contentEdgeInsets = UIEdgeInsetsMake(0, 12, 0, 12);
        _restoreButton.imageEdgeInsets = UIEdgeInsetsMake(0, -4, 0, 4);
        _restoreButton.titleEdgeInsets = UIEdgeInsetsMake(0, 6, 0, -6);
        [_restoreButton addTarget:self action:@selector(onTapRestoreButton) forControlEvents:UIControlEventTouchUpInside];
    }
    return _restoreButton;
}

- (UIButton *)payButton {
    if (!_payButton) {
        _payButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [_payButton setTitle:KBLocalized(@"Recharge Now") forState:UIControlStateNormal];
        [_payButton setTitleColor:[UIColor colorWithHex:KBBlackValue] forState:UIControlStateNormal];
//        _payButton.titleLabel.font = [UIFont systemFontOfSize:16 weight:UIFontWeightSemibold];
        _payButton.titleLabel.font = [KBFont medium:15];
        UIImage *bg = [UIImage imageNamed:@"recharge_now_icon"];
        if (bg) {
            [_payButton setBackgroundImage:bg forState:UIControlStateNormal];
        } else {
            // 兜底：纯代码渐变
            UIImage *fallback = [UIImage kb_gradientImageWithColors:@[[UIColor colorWithHex:0xC7F8F0], [UIColor colorWithHex:0xE8FFF6]] size:CGSizeMake(10, 58) direction:KBGradientDirectionLeftToRight];
            [_payButton setBackgroundImage:[fallback resizableImageWithCapInsets:UIEdgeInsetsMake(29, 29, 29, 29) resizingMode:UIImageResizingModeStretch] forState:UIControlStateNormal];
        }
        [_payButton addTarget:self action:@selector(onTapPayButton) forControlEvents:UIControlEventTouchUpInside];
    }
    return _payButton;
}

- (UILabel *)agreementLabel {
    if (!_agreementLabel) {
        _agreementLabel = [UILabel new];
        _agreementLabel.text = @"By clicking \"Pay\", you indicate your agreement to the";
        _agreementLabel.font = [KBFont regular:12];
        _agreementLabel.textColor = [UIColor colorWithHex:KBBlackValue];
    }
    return _agreementLabel;
}

- (UIButton *)agreementButton {
    if (!_agreementButton) {
        _agreementButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [_agreementButton setTitle:@"《Embership Agreement》" forState:UIControlStateNormal];
        [_agreementButton setTitleColor:[UIColor colorWithHex:KBColorValue] forState:UIControlStateNormal];
        _agreementButton.titleLabel.font = [KBFont regular:12];
        [_agreementButton addTarget:self action:@selector(agreementButtonAction) forControlEvents:UIControlEventTouchUpInside];
    }
    return _agreementButton;
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    // 宽度变化时重算 Header 高度并刷新布局
    CGFloat w = self.collectionView.bounds.size.width ?: KB_SCREEN_WIDTH;
    CGFloat newH = [self kb_calcHeaderHeightForWidth:w];
    if (fabs(newH - self.headerHeight) > 0.5) {
        self.headerHeight = newH;
        UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout;
        [layout invalidateLayout];
    }
}
@end