keyboard/CustomKeyboard/View/KBKeyboardView.m

//
//  KBKeyboardView.m
//  CustomKeyboard
//

#import "KBKeyboardView.h"
#import "KBKeyButton.h"
#import "KBKey.h"
#import "KBSkinManager.h"
#import "KBKeyPreviewView.h"
#import "KBBackspaceLongPressHandler.h"
#import "KBKeyboardLayoutConfig.h"

// UI 常量统一管理，方便后续调试样式（以 375 宽设计稿为基准，通过 KBFit 做等比缩放）
#define kKBRowVerticalSpacing  KBFit(8.0f)
#define kKBRowHorizontalInset  KBFit(6.0f)
#define kKBRowHeight           KBFit(40.0f)

static const NSTimeInterval kKBPreviewShowDuration = 0.08;
static const NSTimeInterval kKBPreviewHideDuration = 0.06;

static const CGFloat kKBSpecialKeySquareMultiplier = 1.2;
static const CGFloat kKBReturnWidthMultiplier = 2.4;
static const CGFloat kKBSpaceWidthMultiplier = 3.0;

// 第二行字母行的左右占位比例（用于居中）
static const CGFloat kKBLettersRow2EdgeSpacerMultiplier = 0.5;

@interface KBKeyboardView ()
@property (nonatomic, strong) UIView *row1;
@property (nonatomic, strong) UIView *row2;
@property (nonatomic, strong) UIView *row3;
@property (nonatomic, strong) UIView *row4;
@property (nonatomic, strong) NSArray<NSArray<KBKey *> *> *keysForRows;
@property (nonatomic, strong) KBBackspaceLongPressHandler *backspaceHandler;
@property (nonatomic, strong) KBKeyPreviewView *previewView;
@property (nonatomic, strong) KBKeyboardLayoutConfig *layoutConfig;
@end

@implementation KBKeyboardView

- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        self.backgroundColor = [KBSkinManager shared].current.keyboardBackground;
        _layoutStyle = KBKeyboardLayoutStyleLetters;
        // 默认小写：与需求一致，初始不开启 Shift
        _shiftOn = NO;
        _symbolsMoreOn = NO; // 数字面板默认第一页（123）
        self.layoutConfig = [KBKeyboardLayoutConfig sharedConfig];
        self.backspaceHandler = [[KBBackspaceLongPressHandler alloc] initWithContainerView:self];
        [self buildBase];
        [self reloadKeys];
    }
    return self;
}

// 当切换大布局（字母/数字）时，重置数字二级页状态
- (void)setLayoutStyle:(KBKeyboardLayoutStyle)layoutStyle {
    _layoutStyle = layoutStyle;
    if (_layoutStyle != KBKeyboardLayoutStyleNumbers) {
        _symbolsMoreOn = NO;
    }
}

#pragma mark - Base Layout

- (void)buildBase {
    [self addSubview:self.row1];
    [self addSubview:self.row2];
    [self addSubview:self.row3];
    [self addSubview:self.row4];

    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    KBKeyboardLayout *layout = [self kb_layoutForName:@"letters"];
    NSArray<KBKeyboardRowConfig *> *rows = layout.rows ?: @[];

    CGFloat rowSpacing = [self kb_metricValue:config.metrics.rowSpacing fallback:nil defaultValue:8.0];
    CGFloat topInset = [self kb_metricValue:config.metrics.topInset fallback:nil defaultValue:8.0];
    CGFloat bottomInset = [self kb_metricValue:config.metrics.bottomInset fallback:nil defaultValue:6.0];

    CGFloat row1Height = [self kb_rowHeightForRow:(rows.count > 0 ? rows[0] : nil)];
    CGFloat row2Height = [self kb_rowHeightForRow:(rows.count > 1 ? rows[1] : nil)];
    CGFloat row3Height = [self kb_rowHeightForRow:(rows.count > 2 ? rows[2] : nil)];
    CGFloat row4Height = [self kb_rowHeightForRow:(rows.count > 3 ? rows[3] : nil)];

    [self.row1 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.mas_top).offset(topInset);
        make.left.right.equalTo(self);
        make.height.mas_equalTo(row1Height);
    }];
    [self.row2 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row1.mas_bottom).offset(rowSpacing);
        make.left.right.equalTo(self);
        make.height.mas_equalTo(row2Height);
    }];
    [self.row3 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row2.mas_bottom).offset(rowSpacing);
        make.left.right.equalTo(self);
        make.height.mas_equalTo(row3Height);
    }];
    [self.row4 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row3.mas_bottom).offset(rowSpacing);
        make.left.right.equalTo(self);
        make.height.mas_equalTo(row4Height);
        make.bottom.equalTo(self.mas_bottom).offset(-bottomInset);
    }];
}

#pragma mark - Public

- (void)reloadKeys {
    [self.backspaceHandler bindDeleteButton:nil showClearLabel:NO];
    // 移除旧按钮
    for (UIView *row in @[self.row1, self.row2, self.row3, self.row4]) {
        [row.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    }

    KBKeyboardLayout *layout = [self kb_currentLayout];
    NSArray<KBKeyboardRowConfig *> *rows = layout.rows ?: @[];
    if (rows.count < 4) {
        [self kb_buildLegacyLayout];
        return;
    }

    [self buildRow:self.row1 withRowConfig:rows[0]];
    [self buildRow:self.row2 withRowConfig:rows[1]];
    [self buildRow:self.row3 withRowConfig:rows[2]];
    [self buildRow:self.row4 withRowConfig:rows[3]];
}

#pragma mark - Hit Test

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    UIView *hit = [super hitTest:point withEvent:event];
    if ([hit isKindOfClass:[KBKeyButton class]]) {
        return hit;
    }
    if ([self kb_isHitInsideKeyRows:hit]) {
        KBKeyButton *btn = [self kb_nearestKeyButtonForPoint:point];
        if (btn) { return btn; }
    }
    return hit;
}

- (BOOL)kb_isHitInsideKeyRows:(UIView *)hitView {
    if (!hitView) { return NO; }
    if (hitView == self) { return YES; }
    if ([hitView isDescendantOfView:self.row1]) { return YES; }
    if ([hitView isDescendantOfView:self.row2]) { return YES; }
    if ([hitView isDescendantOfView:self.row3]) { return YES; }
    if ([hitView isDescendantOfView:self.row4]) { return YES; }
    return NO;
}

- (KBKeyButton *)kb_nearestKeyButtonForPoint:(CGPoint)point {
    KBKeyButton *best = nil;
    CGFloat bestDistance = CGFLOAT_MAX;
    NSArray<UIView *> *rows = @[self.row1, self.row2, self.row3, self.row4];

    UIView *targetRow = nil;
    for (UIView *row in rows) {
        CGRect rowFrame = [self convertRect:row.bounds fromView:row];
        if (CGRectContainsPoint(rowFrame, point)) {
            targetRow = row;
            break;
        }
    }

    NSArray<UIView *> *candidateRows = targetRow ? @[targetRow] : rows;
    for (UIView *row in candidateRows) {
        NSArray<KBKeyButton *> *buttons = [self kb_collectKeyButtonsInView:row];
        for (KBKeyButton *btn in buttons) {
            CGRect frame = [self convertRect:btn.frame fromView:btn.superview];
            CGFloat dx = point.x - CGRectGetMidX(frame);
            CGFloat dy = point.y - CGRectGetMidY(frame);
            CGFloat dist = (dx * dx) + (dy * dy);
            if (dist < bestDistance) {
                bestDistance = dist;
                best = btn;
            }
        }
    }
    return best;
}

- (NSArray<KBKeyButton *> *)kb_collectKeyButtonsInView:(UIView *)view {
    if (!view) { return @[]; }
    NSMutableArray<KBKeyButton *> *buttons = [NSMutableArray array];
    [self kb_collectKeyButtonsInView:view into:buttons];
    return buttons.copy;
}

- (void)kb_collectKeyButtonsInView:(UIView *)view
                              into:(NSMutableArray<KBKeyButton *> *)buttons {
    for (UIView *sub in view.subviews) {
        if ([sub isKindOfClass:[KBKeyButton class]]) {
            [buttons addObject:(KBKeyButton *)sub];
            continue;
        }
        if (sub.subviews.count > 0) {
            [self kb_collectKeyButtonsInView:sub into:buttons];
        }
    }
}

#pragma mark - Key Model Construction

// 创建当前布局下各行的 KBKey 列表
- (NSArray<NSArray<KBKey *> *> *)buildKeysForCurrentLayout {
    if (self.layoutStyle == KBKeyboardLayoutStyleNumbers) {
        return [self buildKeysForNumbersLayout];
    } else {
        return [self buildKeysForLettersLayout];
    }
}

#pragma mark - Letters Layout

- (NSArray<NSArray<KBKey *> *> *)buildKeysForLettersLayout {
    // 字母布局（QWERTY）
    NSArray *r1Letters = @[ @"q", @"w", @"e", @"r", @"t", @"y", @"u", @"i", @"o", @"p" ];
    NSArray *r2Letters = @[ @"a", @"s", @"d", @"f", @"g", @"h", @"j", @"k", @"l" ];
    NSArray *r3Letters = @[ @"z", @"x", @"c", @"v", @"b", @"n", @"m" ];

    NSMutableArray *row1 = [NSMutableArray arrayWithCapacity:r1Letters.count];
    for (NSString *s in r1Letters) {
        [row1 addObject:[self kb_letterKeyWithChar:s]];
    }

    NSMutableArray *row2 = [NSMutableArray arrayWithCapacity:r2Letters.count];
    for (NSString *s in r2Letters) {
        [row2 addObject:[self kb_letterKeyWithChar:s]];
    }

    // 第三行：Shift + Z...M + Backspace
    NSMutableArray *row3 = [NSMutableArray array];
    KBKey *shift = [KBKey keyWithIdentifier:@"shift"
                                      title:@"⇧"
                                     output:@""
                                       type:KBKeyTypeShift];
    // Shift 键也支持大小写两套皮肤图：
    // - shift.caseVariant = Lower 时，使用 KBSkinIconMap 中 "shift" 对应的短名；
    // - shift.caseVariant = Upper 时，使用 "shift_upper" 对应的短名。
    shift.caseVariant = self.shiftOn ? KBKeyCaseVariantUpper : KBKeyCaseVariantLower;
    [row3 addObject:shift];

    for (NSString *s in r3Letters) {
        [row3 addObject:[self kb_letterKeyWithChar:s]];
    }

    KBKey *backspace = [KBKey keyWithIdentifier:@"backspace"
                                          title:@"⌫"
                                         output:@""
                                           type:KBKeyTypeBackspace];
    [row3 addObject:backspace];

    NSArray *row4 = [self kb_bottomControlRowKeysForLettersLayout];

    return @[row1.copy, row2.copy, row3.copy, row4];
}

#pragma mark - Numbers / Symbols Layout

- (NSArray<NSArray<KBKey *> *> *)buildKeysForNumbersLayout {
    // 数字/符号布局：3 行主键 + 底部控制行
    NSArray *r1 = nil;
    NSArray *r2 = nil;
    NSArray *r3 = nil;

    if (!self.symbolsMoreOn) {
        // 数字第一页（123）
        r1 = @[ [KBKey keyWithIdentifier:@"digit_1" title:@"1" output:@"1" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_2" title:@"2" output:@"2" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_3" title:@"3" output:@"3" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_4" title:@"4" output:@"4" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_5" title:@"5" output:@"5" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_6" title:@"6" output:@"6" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_7" title:@"7" output:@"7" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_8" title:@"8" output:@"8" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_9" title:@"9" output:@"9" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"digit_0" title:@"0" output:@"0" type:KBKeyTypeCharacter] ];
        r2 = @[ [KBKey keyWithIdentifier:@"sym_minus"     title:@"-" output:@"-" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_slash"     title:@"/" output:@"/" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_colon"     title:@":" output:@":" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_semicolon" title:@";" output:@";" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_paren_l"   title:@"(" output:@"(" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_paren_r"   title:@")" output:@")" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_money"    title:@"¥" output:@"¥" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_amp"       title:@"&" output:@"&" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_at"        title:@"@" output:@"@" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_quote_double" title:@"\"" output:@"\"" type:KBKeyTypeCharacter] ];

        r3 = [self kb_symbolsCommonThirdRowWithToggleIsMore:NO];
    } else {
        // 数字第二页（#+=）：前两行替换为更多符号，左下角按钮文案改为“123”
        r1 = @[ [KBKey keyWithIdentifier:@"sym_bracket_l" title:@"[" output:@"[" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_bracket_r" title:@"]" output:@"]" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_brace_l"   title:@"{" output:@"{" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_brace_r"   title:@"}" output:@"}" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_hash"      title:@"#" output:@"#" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_percent"   title:@"%" output:@"%" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_caret"     title:@"^" output:@"^" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_asterisk"  title:@"*" output:@"*" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_plus"      title:@"+" output:@"+" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_equal"     title:@"=" output:@"=" type:KBKeyTypeCharacter] ];
        r2 = @[ [KBKey keyWithIdentifier:@"sym_underscore" title:@"_" output:@"_" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_backslash"  title:@"\\" output:@"\\" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_pipe"       title:@"|" output:@"|" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_tilde"      title:@"~" output:@"~" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_lt"         title:@"<" output:@"<" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_gt"         title:@">" output:@">" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_dollar"     title:@"$" output:@"$" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_euro"       title:@"€" output:@"€" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_pound"      title:@"£" output:@"£" type:KBKeyTypeCharacter],
                [KBKey keyWithIdentifier:@"sym_bullet"     title:@"•" output:@"•" type:KBKeyTypeCharacter] ];

        r3 = [self kb_symbolsCommonThirdRowWithToggleIsMore:YES];
    }

    NSArray *r4 = [self kb_bottomControlRowKeysForNumbersLayout];
    return @[r1, r2, r3, r4];
}

#pragma mark - Key Factories

// 字母键工厂：根据 shiftOn 决定显示与输出大小写
- (KBKey *)kb_letterKeyWithChar:(NSString *)charString {
    NSParameterAssert(charString.length == 1);
    NSString *lower = charString.lowercaseString;
    NSString *upper = charString.uppercaseString;

    NSString *shown = self.shiftOn ? upper : lower;
    NSString *identifier = [NSString stringWithFormat:@"letter_%@", lower];

    KBKey *k = [KBKey keyWithIdentifier:identifier
                                  title:shown
                                 output:shown
                                   type:KBKeyTypeCharacter];
    k.caseVariant = self.shiftOn ? KBKeyCaseVariantUpper : KBKeyCaseVariantLower;
    return k;
}

// 数字布局第三行公共部分（左下角是 123 或 #+=）
- (NSArray<KBKey *> *)kb_symbolsCommonThirdRowWithToggleIsMore:(BOOL)isMorePage {
    NSString *identifier = isMorePage ? @"symbols_toggle_123" : @"symbols_toggle_more";
    NSString *title      = isMorePage ? @"123" : @"#+=";

    KBKey *toggle = [KBKey keyWithIdentifier:identifier
                                       title:title
                                      output:@""
                                        type:KBKeyTypeSymbolsToggle];
    KBKey *comma = [KBKey keyWithIdentifier:@"sym_comma" title:@"," output:@"," type:KBKeyTypeCharacter];
    KBKey *dot   = [KBKey keyWithIdentifier:@"sym_dot"   title:@"." output:@"." type:KBKeyTypeCharacter];
    KBKey *q     = [KBKey keyWithIdentifier:@"sym_question" title:@"?" output:@"?" type:KBKeyTypeCharacter];
    KBKey *ex    = [KBKey keyWithIdentifier:@"sym_exclam" title:@"!" output:@"!" type:KBKeyTypeCharacter];
    KBKey *quote = [KBKey keyWithIdentifier:@"sym_quote_single" title:@"'" output:@"'" type:KBKeyTypeCharacter];
    KBKey *back = [KBKey keyWithIdentifier:@"backspace"
                                     title:@"⌫"
                                    output:@""
                                      type:KBKeyTypeBackspace];
    return @[ toggle, comma, dot, q, ex, quote, back ];
}

// 底部控制行（字母布局）
- (NSArray<KBKey *> *)kb_bottomControlRowKeysForLettersLayout {
    KBKey *mode123 = [KBKey keyWithIdentifier:@"mode_123"
                                        title:@"123"
                                       output:@""
                                         type:KBKeyTypeModeChange];
    KBKey *emoji = [KBKey keyWithIdentifier:KBKeyIdentifierEmojiPanel
                                      title:@"😊"
                                     output:@""
                                       type:KBKeyTypeCustom];
    KBKey *space = [KBKey keyWithIdentifier:@"space"
                                      title:@"space"
                                     output:@" "
                                       type:KBKeyTypeSpace];
    KBKey *ret = [KBKey keyWithIdentifier:@"return"
                                    title:KBLocalized(@"Send")
                                   output:@"\n"
                                     type:KBKeyTypeReturn];
    return @[ mode123, emoji, space, ret ];
}

// 底部控制行（数字布局）
- (NSArray<KBKey *> *)kb_bottomControlRowKeysForNumbersLayout {
    KBKey *modeABC = [KBKey keyWithIdentifier:@"mode_abc"
                                        title:@"abc"
                                       output:@""
                                         type:KBKeyTypeModeChange];
    KBKey *emoji = [KBKey keyWithIdentifier:KBKeyIdentifierEmojiPanel
                                      title:@"😊"
                                     output:@""
                                       type:KBKeyTypeCustom];
    KBKey *space = [KBKey keyWithIdentifier:@"space"
                                      title:@"space"
                                     output:@" "
                                       type:KBKeyTypeSpace];
    KBKey *ret = [KBKey keyWithIdentifier:@"return"
                                    title:KBLocalized(@"Send")
                                   output:@"\n"
                                     type:KBKeyTypeReturn];
    return @[ modeABC, emoji, space, ret ];
}

#pragma mark - Row Building

- (void)buildRow:(UIView *)row withRowConfig:(KBKeyboardRowConfig *)rowConfig {
    if (!row || !rowConfig) { return; }
    CGFloat gap = [self kb_gapForRow:rowConfig];
    CGFloat insetLeft = [self kb_insetLeftForRow:rowConfig];
    CGFloat insetRight = [self kb_insetRightForRow:rowConfig];

    if (rowConfig.segments) {
        KBKeyboardRowSegments *segments = rowConfig.segments;
        NSArray<KBKeyboardRowItem *> *leftItems = [segments leftItems];
        NSArray<KBKeyboardRowItem *> *centerItems = [segments centerItems];
        NSArray<KBKeyboardRowItem *> *rightItems = [segments rightItems];
        UIView *leftContainer = [UIView new];
        UIView *centerContainer = [UIView new];
        UIView *rightContainer = [UIView new];
        [row addSubview:leftContainer];
        [row addSubview:centerContainer];
        [row addSubview:rightContainer];

        [leftContainer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.left.equalTo(row.mas_left).offset(insetLeft);
            make.top.bottom.equalTo(row);
        }];
        [rightContainer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.right.equalTo(row.mas_right).offset(-insetRight);
            make.top.bottom.equalTo(row);
        }];
        [centerContainer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.centerX.equalTo(row);
            make.top.bottom.equalTo(row);
            make.left.greaterThanOrEqualTo(leftContainer.mas_right).offset(gap);
            make.right.lessThanOrEqualTo(rightContainer.mas_left).offset(-gap);
        }];

        if (leftItems.count == 0) {
            [leftContainer mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.mas_equalTo(0);
            }];
        }
        if (centerItems.count == 0) {
            [centerContainer mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.mas_equalTo(0);
            }];
        }
        if (rightItems.count == 0) {
            [rightContainer mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.mas_equalTo(0);
            }];
        }

        [self kb_buildButtonsInContainer:leftContainer
                                   items:leftItems
                                     gap:gap
                               insetLeft:0
                              insetRight:0
                             alignCenter:NO];
        [self kb_buildButtonsInContainer:centerContainer
                                   items:centerItems
                                     gap:gap
                               insetLeft:0
                              insetRight:0
                             alignCenter:NO];
        [self kb_buildButtonsInContainer:rightContainer
                                   items:rightItems
                                     gap:gap
                               insetLeft:0
                              insetRight:0
                             alignCenter:NO];
        return;
    }

    BOOL alignCenter = [rowConfig.align.lowercaseString isEqualToString:@"center"];
    [self kb_buildButtonsInContainer:row
                               items:[rowConfig resolvedItems]
                                 gap:gap
                           insetLeft:insetLeft
                          insetRight:insetRight
                         alignCenter:alignCenter];
}

- (void)kb_buildButtonsInContainer:(UIView *)container
                             items:(NSArray<KBKeyboardRowItem *> *)items
                               gap:(CGFloat)gap
                         insetLeft:(CGFloat)insetLeft
                        insetRight:(CGFloat)insetRight
                       alignCenter:(BOOL)alignCenter {
    if (items.count == 0) { return; }

    UIView *leftSpacer = nil;
    UIView *rightSpacer = nil;
    if (alignCenter) {
        leftSpacer = [UIView new];
        rightSpacer = [UIView new];
        [container addSubview:leftSpacer];
        [container addSubview:rightSpacer];
        [leftSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.left.equalTo(container.mas_left).offset(insetLeft);
            make.top.bottom.equalTo(container);
        }];
        [rightSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.right.equalTo(container.mas_right).offset(-insetRight);
            make.top.bottom.equalTo(container);
        }];
        [leftSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(rightSpacer);
        }];
    }

    KBKeyButton *previous = nil;
    for (KBKeyboardRowItem *item in items) {
        KBKeyButton *btn = [self kb_buttonForItem:item];
        if (!btn) { continue; }
        [container addSubview:btn];

        [btn mas_makeConstraints:^(MASConstraintMaker *make) {
            make.top.bottom.equalTo(container);
            if (previous) {
                make.left.equalTo(previous.mas_right).offset(gap);
            } else {
                if (leftSpacer) {
                    make.left.equalTo(leftSpacer.mas_right).offset(gap);
                } else {
                    make.left.equalTo(container.mas_left).offset(insetLeft);
                }
            }
        }];

        CGFloat width = [self kb_widthForItem:item key:btn.key];
        if (width > 0.0) {
            [btn mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.mas_equalTo(width);
            }];
        }

        previous = btn;
    }

    if (!previous) { return; }
    [previous mas_makeConstraints:^(MASConstraintMaker *make) {
        if (rightSpacer) {
            make.right.equalTo(rightSpacer.mas_left).offset(-gap);
        } else {
            make.right.equalTo(container.mas_right).offset(-insetRight);
        }
    }];
}

- (void)buildRow:(UIView *)row withKeys:(NSArray<KBKey *> *)keys {
    [self buildRow:row withKeys:keys edgeSpacerMultiplier:0.0];
}

- (void)buildRow:(UIView *)row
        withKeys:(NSArray<KBKey *> *)keys
edgeSpacerMultiplier:(CGFloat)edgeSpacerMultiplier {

    // 第 4 行（底部控制行）使用单独的布局规则：
    // 123/ABC、Emoji、Send 给定尺寸，Space 自动吃掉剩余宽度。
    BOOL isBottomControlRow = [self kb_isBottomControlRowWithKeys:keys];

    CGFloat spacing = 0;  // 键与键之间的间距
    UIView *previous = nil;
    UIView *leftSpacer = nil;
    UIView *rightSpacer = nil;

    if (edgeSpacerMultiplier > 0.0) {
        leftSpacer = [UIView new];
        rightSpacer = [UIView new];
        leftSpacer.backgroundColor = [UIColor clearColor];
        rightSpacer.backgroundColor = [UIColor clearColor];
        [row addSubview:leftSpacer];
        [row addSubview:rightSpacer];
        [leftSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.left.equalTo(row.mas_left).offset(kKBRowHorizontalInset);
            make.centerY.equalTo(row);
            make.height.mas_equalTo(1);
        }];
        [rightSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
            make.right.equalTo(row.mas_right).offset(-kKBRowHorizontalInset);
            make.centerY.equalTo(row);
            make.height.mas_equalTo(1);
        }];
    }

    for (NSInteger i = 0; i < keys.count; i++) {
        KBKey *key = keys[i];
        KBKeyButton *btn = [[KBKeyButton alloc] init];
        btn.key = key;
        [btn setTitle:key.title forState:UIControlStateNormal];
        // 在设置完标题后，按当前皮肤应用图标与文字显隐
        [btn applyThemeForCurrentKey];
        [btn addTarget:self action:@selector(onKeyTapped:) forControlEvents:UIControlEventTouchUpInside];
        [row addSubview:btn];

        if (key.type == KBKeyTypeBackspace) {
            [self.backspaceHandler bindDeleteButton:btn showClearLabel:YES];
        }

        // Shift 按钮选中态随大小写状态变化
        if (key.type == KBKeyTypeShift) {
            btn.selected = self.shiftOn;
        }

        [btn mas_makeConstraints:^(MASConstraintMaker *make) {
            make.top.bottom.equalTo(row);
            if (previous) {
                make.left.equalTo(previous.mas_right).offset(spacing);
            } else {
                if (leftSpacer) {
                    make.left.equalTo(leftSpacer.mas_right).offset(spacing);
                } else {
                    make.left.equalTo(row.mas_left).offset(kKBRowHorizontalInset);
                }
            }
        }];

        // 字符键：等宽
        if (key.type == KBKeyTypeCharacter) {
            if (previous && [previous isKindOfClass:[KBKeyButton class]]) {
                KBKeyButton *prevBtn = (KBKeyButton *)previous;
                if (prevBtn.key.type == KBKeyTypeCharacter) {
                    [btn mas_makeConstraints:^(MASConstraintMaker *make) {
                        make.width.equalTo(previous);
                    }];
                }
            }
        } else {
            // special keys: 宽度在第二遍统一设置
        }

        previous = btn;
    }

    // 右侧使用内边距或右占位
    if (previous) {
        [previous mas_makeConstraints:^(MASConstraintMaker *make) {
            if (rightSpacer) {
                make.right.equalTo(rightSpacer.mas_left).offset(-spacing);
            } else {
                make.right.equalTo(row.mas_right).offset(-kKBRowHorizontalInset);
            }
        }];
    }

    // 底部控制行：在第一轮已完成左右约束的前提下，仅给 123/ABC、Emoji、Send 指定宽度，
    // Space 不加宽度约束，让其自动填充剩余空间。
    if (isBottomControlRow) {
        [self kb_applyBottomControlRowWidthInRow:row];
        return;
    }

    // 第二遍：以首个字符键为基准，统一设置特殊键宽度倍数
    KBKeyButton *firstChar = nil;
    BOOL hasCharacterInRow = NO;
    for (UIView *v in row.subviews) {
        if (![v isKindOfClass:[KBKeyButton class]]) continue;
        KBKeyButton *b = (KBKeyButton *)v;
        if (b.key.type == KBKeyTypeCharacter) {
            firstChar = b;
            hasCharacterInRow = YES;
            break;
        }
    }
    // 若该行没有字符键（例如底部控制行之外的特殊行），则使用行内第一个按钮作为基准宽度
    if (!firstChar) {
        for (UIView *v in row.subviews) {
            if ([v isKindOfClass:[KBKeyButton class]]) {
                firstChar = (KBKeyButton *)v;
                break;
            }
        }
    }
    if (firstChar) {
        // 如果该行本身没有字符键（如底部控制行），且基准按钮是 123/ABC/#+= 等，
        // 也将其约束为 1:1，避免 123/ABC 不是正方形。
        if (!hasCharacterInRow &&
            (firstChar.key.type == KBKeyTypeModeChange ||
             firstChar.key.type == KBKeyTypeSymbolsToggle ||
             firstChar.key.type == KBKeyTypeCustom)) {
            [firstChar mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.equalTo(firstChar.mas_height).multipliedBy(kKBSpecialKeySquareMultiplier);
            }];
        }

        for (UIView *v in row.subviews) {
            if (![v isKindOfClass:[KBKeyButton class]]) continue;
            KBKeyButton *b = (KBKeyButton *)v;

            // 避免对基准按钮自身添加 self == self * k 的无效约束
            if (b == firstChar) continue;
            if (b.key.type == KBKeyTypeCharacter) continue;

            BOOL isBottomModeKey = (b.key.type == KBKeyTypeModeChange) ||
                                   (b.key.type == KBKeyTypeSymbolsToggle) ||
                                   (b.key.type == KBKeyTypeCustom);
            // 一类键强制近似正方形（宽 ~ 高）
            if (b.key.type == KBKeyTypeShift ||
                b.key.type == KBKeyTypeBackspace ||
                isBottomModeKey) {
                [b mas_makeConstraints:^(MASConstraintMaker *make) {
                    make.width.equalTo(b.mas_height).multipliedBy(kKBSpecialKeySquareMultiplier);
                }];
                continue;
            }

            CGFloat multiplier = 1.5;

            // Space：宽度更大
            if (b.key.type == KBKeyTypeSpace) {
                multiplier = kKBSpaceWidthMultiplier;
            }
            // Send 按钮：宽度为基准键的 2.4 倍
            else if (b.key.type == KBKeyTypeReturn) {
                multiplier = kKBReturnWidthMultiplier;
            }
            // 其它特殊键（如 Globe）保持适度放大
            else if (b.key.type == KBKeyTypeGlobe) {
                multiplier = 1.5;
            }

            [b mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.equalTo(firstChar).multipliedBy(multiplier);
            }];
        }

        // 如果有左右占位，则把占位宽度设置为字符键宽度的一定倍数，以实现整体居中；
        // 同时强约束左右占位宽度相等，避免在某些系统上由于布局冲突导致只压缩一侧，
        // 出现“左侧有空隙，右侧无空隙”的情况。
        if (leftSpacer && rightSpacer) {
            // 1) 左右占位宽度必须相等
            [leftSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.equalTo(rightSpacer);
            }];
            // 2) 同时都接近字符键宽度的 edgeSpacerMultiplier 倍数
            [rightSpacer mas_makeConstraints:^(MASConstraintMaker *make) {
                make.width.equalTo(firstChar).multipliedBy(edgeSpacerMultiplier);
            }];
        }
    }
}

#pragma mark - Row Helpers (Bottom Control Row)

// 判断是否为底部控制行：包含 Space + Return，且有 ModeChange/SymbolsToggle，
// 并且不再含字符键。
- (BOOL)kb_isBottomControlRowWithKeys:(NSArray<KBKey *> *)keys {
    BOOL hasSpace = NO;
    BOOL hasReturn = NO;
    BOOL hasModeOrSymbols = NO;
    for (KBKey *k in keys) {
        if (k.type == KBKeyTypeCharacter) {
            return NO;
        }
        if (k.type == KBKeyTypeSpace) {
            hasSpace = YES;
        } else if (k.type == KBKeyTypeReturn) {
            hasReturn = YES;
        } else if (k.type == KBKeyTypeModeChange || k.type == KBKeyTypeSymbolsToggle) {
            hasModeOrSymbols = YES;
        }
    }
    return hasSpace && hasReturn && hasModeOrSymbols;
}

// 为底部控制行设置宽度：
// - 123/ABC、Emoji：正方形（宽 = 行高 * multiplier）
// - Send：宽 = 模式键宽度的 2 倍
// - Space：不加宽度约束，依靠左右约束自动填充剩余空间。
- (void)kb_applyBottomControlRowWidthInRow:(UIView *)row {
    KBKeyButton *modeBtn = nil;
    NSMutableArray<KBKeyButton *> *customButtons = [NSMutableArray array];
    KBKeyButton *spaceBtn = nil;
    KBKeyButton *retBtn = nil;

    for (UIView *v in row.subviews) {
        if (![v isKindOfClass:[KBKeyButton class]]) continue;
        KBKeyButton *b = (KBKeyButton *)v;
        switch (b.key.type) {
            case KBKeyTypeModeChange:
            case KBKeyTypeSymbolsToggle:
                modeBtn = b;
                break;
            case KBKeyTypeCustom:
                [customButtons addObject:b];
                break;
            case KBKeyTypeSpace:
                spaceBtn = b;
                break;
            case KBKeyTypeReturn:
                retBtn = b;
                break;
            default:
                break;
        }
    }

    if (!modeBtn || customButtons.count == 0 || !spaceBtn || !retBtn) {
        return;
    }

    [modeBtn mas_makeConstraints:^(MASConstraintMaker *make) {
        make.width.equalTo(row.mas_height).multipliedBy(kKBSpecialKeySquareMultiplier);
    }];
    for (KBKeyButton *custom in customButtons) {
        [custom mas_makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(row.mas_height).multipliedBy(kKBSpecialKeySquareMultiplier);
        }];
    }
    [retBtn mas_makeConstraints:^(MASConstraintMaker *make) {
        make.width.equalTo(modeBtn.mas_width).multipliedBy(2.0);
    }];
    // Space 不设置宽度；通过此前已建立的左右约束自动占满剩余宽度。
}

#pragma mark - Config Helpers

- (KBKeyboardLayoutConfig *)kb_layoutConfig {
    if (!self.layoutConfig) {
        self.layoutConfig = [KBKeyboardLayoutConfig sharedConfig];
    }
    return self.layoutConfig;
}

- (KBKeyboardLayout *)kb_layoutForName:(NSString *)name {
    return [[self kb_layoutConfig] layoutForName:name];
}

- (KBKeyboardLayout *)kb_currentLayout {
    if (self.layoutStyle == KBKeyboardLayoutStyleNumbers) {
        return [self kb_layoutForName:(self.symbolsMoreOn ? @"symbolsMore" : @"numbers")];
    }
    return [self kb_layoutForName:@"letters"];
}

- (void)kb_buildLegacyLayout {
    self.keysForRows = [self buildKeysForCurrentLayout];
    if (self.keysForRows.count < 4) { return; }

    [self buildRow:self.row1 withKeys:self.keysForRows[0]];

    CGFloat row2Spacer = (self.layoutStyle == KBKeyboardLayoutStyleLetters)
                         ? kKBLettersRow2EdgeSpacerMultiplier : 0.0;
    [self buildRow:self.row2 withKeys:self.keysForRows[1] edgeSpacerMultiplier:row2Spacer];

    [self buildRow:self.row3 withKeys:self.keysForRows[2]];
    [self buildRow:self.row4 withKeys:self.keysForRows[3]];
}

- (CGFloat)kb_scaledValue:(CGFloat)designValue {
    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    if (config) {
        return [config scaledValue:designValue];
    }
    return KBFit(designValue);
}

- (CGFloat)kb_numberValue:(NSNumber *)value defaultValue:(CGFloat)defaultValue {
    if ([value isKindOfClass:[NSNumber class]]) {
        return value.doubleValue;
    }
    return defaultValue;
}

- (CGFloat)kb_metricValue:(NSNumber *)value fallback:(NSNumber *)fallback defaultValue:(CGFloat)defaultValue {
    CGFloat v = [self kb_numberValue:value defaultValue:-1.0];
    if (v < 0.0) {
        v = [self kb_numberValue:fallback defaultValue:defaultValue];
    }
    if (v < 0.0) {
        v = defaultValue;
    }
    return [self kb_scaledValue:v];
}

- (CGFloat)kb_rowHeightForRow:(KBKeyboardRowConfig *)row {
    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    NSNumber *height = row.height ?: config.metrics.keyHeight;
    CGFloat value = [self kb_numberValue:height defaultValue:40.0];
    return [self kb_scaledValue:value];
}

- (CGFloat)kb_gapForRow:(KBKeyboardRowConfig *)row {
    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    return [self kb_metricValue:row.gap fallback:config.metrics.gap defaultValue:5.0];
}

- (CGFloat)kb_insetLeftForRow:(KBKeyboardRowConfig *)row {
    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    return [self kb_metricValue:row.insetLeft fallback:config.metrics.edgeInset defaultValue:0.0];
}

- (CGFloat)kb_insetRightForRow:(KBKeyboardRowConfig *)row {
    KBKeyboardLayoutConfig *config = [self kb_layoutConfig];
    return [self kb_metricValue:row.insetRight fallback:config.metrics.edgeInset defaultValue:0.0];
}

- (KBKeyButton *)kb_buttonForItem:(KBKeyboardRowItem *)item {
    if (item.itemId.length == 0) { return nil; }
    KBKeyboardKeyDef *def = [[self kb_layoutConfig] keyDefForIdentifier:item.itemId];
    KBKey *key = [self kb_keyForItemId:item.itemId];
    if (!key) { return nil; }

    KBKeyButton *btn = [[KBKeyButton alloc] init];
    btn.key = key;
    [btn setTitle:key.title forState:UIControlStateNormal];

    UIColor *bgColor = [self kb_backgroundColorForItem:item keyDef:def];
    if (bgColor) {
        btn.customBackgroundColor = bgColor;
    }

    CGFloat fontSize = [self kb_fontSizeForItem:item key:key];
    if (fontSize > 0.0) {
        btn.titleLabel.font = [UIFont systemFontOfSize:fontSize weight:UIFontWeightSemibold];
    }

    [btn applyThemeForCurrentKey];
    [btn addTarget:self action:@selector(onKeyTapped:) forControlEvents:UIControlEventTouchUpInside];

    if (key.type == KBKeyTypeBackspace) {
        [self.backspaceHandler bindDeleteButton:btn showClearLabel:YES];
    }
    if (key.type == KBKeyTypeShift) {
        btn.selected = self.shiftOn;
    }
    [self kb_applySymbolIfNeededForButton:btn keyDef:def fontSize:fontSize];
    return btn;
}

- (void)kb_applySymbolIfNeededForButton:(KBKeyButton *)button
                                 keyDef:(KBKeyboardKeyDef *)def
                               fontSize:(CGFloat)fontSize {
    if (!button || !def) { return; }
    if (button.iconView.image != nil) { return; }
    NSString *symbolName = button.isSelected ? def.selectedSymbolName : def.symbolName;
    if (symbolName.length == 0) { return; }

    UIImage *image = [UIImage systemImageNamed:symbolName];
    if (!image) { return; }

    UIImageSymbolConfiguration *config = [UIImageSymbolConfiguration configurationWithPointSize:fontSize weight:UIFontWeightSemibold];
    image = [image imageWithConfiguration:config];

    button.iconView.image = image;
    button.iconView.hidden = NO;
    button.iconView.contentMode = UIViewContentModeCenter;
    button.titleLabel.hidden = YES;

    UIColor *textColor = [KBSkinManager shared].current.keyTextColor ?: [UIColor blackColor];
    button.iconView.tintColor = button.isSelected ? [UIColor blackColor] : textColor;
}

- (UIColor *)kb_backgroundColorForItem:(KBKeyboardRowItem *)item keyDef:(KBKeyboardKeyDef *)def {
    NSString *hex = def.backgroundColor;
    if (hex.length == 0) {
        hex = [self kb_layoutConfig].defaultKeyBackground;
    }
    if (hex.length == 0) { return nil; }
    return [KBSkinManager colorFromHexString:hex defaultColor:nil];
}

- (CGFloat)kb_metricWidthForKey:(NSString *)key {
    KBKeyboardLayoutMetrics *m = [self kb_layoutConfig].metrics;
    if ([key isEqualToString:@"letterWidth"]) { return m.letterWidth.doubleValue; }
    if ([key isEqualToString:@"controlWidth"]) { return m.controlWidth.doubleValue; }
    if ([key isEqualToString:@"sendWidth"]) { return m.sendWidth.doubleValue; }
    if ([key isEqualToString:@"symbolsWideWidth"]) { return m.symbolsWideWidth.doubleValue; }
    if ([key isEqualToString:@"symbolsSideWidth"]) { return m.symbolsSideWidth.doubleValue; }
    return 0.0;
}

- (CGFloat)kb_widthForItem:(KBKeyboardRowItem *)item key:(KBKey *)key {
    CGFloat width = 0.0;
    if (item.widthValue.doubleValue > 0.0) {
        width = item.widthValue.doubleValue;
    } else if (item.width.length > 0) {
        if ([item.width.lowercaseString isEqualToString:@"flex"]) {
            return 0.0;
        }
        width = [self kb_metricWidthForKey:item.width];
        if (width <= 0.0) {
            width = item.width.doubleValue;
        }
    }

    if (width <= 0.0) {
        KBKeyboardLayoutMetrics *m = [self kb_layoutConfig].metrics;
        if ([item.itemId hasPrefix:@"letter:"] ||
            [item.itemId hasPrefix:@"digit:"] ||
            [item.itemId hasPrefix:@"sym:"]) {
            width = m.letterWidth.doubleValue;
        } else if (key.type == KBKeyTypeReturn) {
            width = m.sendWidth.doubleValue;
        } else if (key.type == KBKeyTypeSpace) {
            return 0.0;
        } else {
            width = m.controlWidth.doubleValue;
        }
    }

    if (width <= 0.0) {
        if ([item.itemId hasPrefix:@"letter:"] ||
            [item.itemId hasPrefix:@"digit:"] ||
            [item.itemId hasPrefix:@"sym:"]) {
            width = 32.0;
        } else if (key.type == KBKeyTypeReturn) {
            width = 88.0;
        } else if (key.type == KBKeyTypeSpace) {
            return 0.0;
        } else {
            width = 41.0;
        }
    }

    return width > 0.0 ? [self kb_scaledValue:width] : 0.0;
}

- (CGFloat)kb_fontSizeForItem:(KBKeyboardRowItem *)item key:(KBKey *)key {
    NSString *fontKey = nil;
    if ([item.itemId hasPrefix:@"letter:"]) {
        fontKey = @"letter";
    } else if ([item.itemId hasPrefix:@"digit:"]) {
        fontKey = @"digit";
    } else if ([item.itemId hasPrefix:@"sym:"]) {
        fontKey = @"symbol";
    } else {
        KBKeyboardKeyDef *def = [[self kb_layoutConfig] keyDefForIdentifier:item.itemId];
        fontKey = def.font;
    }

    if (fontKey.length == 0) {
        switch (key.type) {
            case KBKeyTypeModeChange:
            case KBKeyTypeSymbolsToggle:
                fontKey = @"mode";
                break;
            case KBKeyTypeSpace:
                fontKey = @"space";
                break;
            case KBKeyTypeReturn:
                fontKey = @"send";
                break;
            default:
                fontKey = @"symbol";
                break;
        }
    }

    return [self kb_fontSizeForFontKey:fontKey];
}

- (CGFloat)kb_fontSizeForFontKey:(NSString *)fontKey {
    KBKeyboardLayoutFonts *fonts = [self kb_layoutConfig].fonts;
    CGFloat size = 0.0;
    if ([fontKey isEqualToString:@"letter"]) { size = fonts.letter.doubleValue; }
    else if ([fontKey isEqualToString:@"digit"]) { size = fonts.digit.doubleValue; }
    else if ([fontKey isEqualToString:@"symbol"]) { size = fonts.symbol.doubleValue; }
    else if ([fontKey isEqualToString:@"mode"]) { size = fonts.mode.doubleValue; }
    else if ([fontKey isEqualToString:@"space"]) { size = fonts.space.doubleValue; }
    else if ([fontKey isEqualToString:@"send"]) { size = fonts.send.doubleValue; }
    if (size <= 0.0) { size = 18.0; }
    return [self kb_scaledValue:size];
}

- (KBKey *)kb_keyForItemId:(NSString *)itemId {
    if (itemId.length == 0) { return nil; }
    KBKeyboardKeyDef *def = [[self kb_layoutConfig] keyDefForIdentifier:itemId];
    if (def) {
        return [self kb_keyFromDef:def identifier:itemId];
    }

    NSRange range = [itemId rangeOfString:@":"]; 
    if (range.location != NSNotFound) {
        NSString *prefix = [itemId substringToIndex:range.location];
        NSString *value = [itemId substringFromIndex:range.location + 1];
        if ([prefix isEqualToString:@"letter"]) {
            if (value.length == 1) {
                return [self kb_letterKeyWithChar:value];
            }
            return nil;
        }
        if ([prefix isEqualToString:@"digit"]) {
            NSString *identifier = [NSString stringWithFormat:@"digit_%@", value];
            KBKey *k = [KBKey keyWithIdentifier:identifier title:value output:value type:KBKeyTypeCharacter];
            k.caseVariant = KBKeyCaseVariantNone;
            return k;
        }
        if ([prefix isEqualToString:@"sym"]) {
            NSString *identifier = [self kb_identifierForSymbol:value];
            KBKey *k = [KBKey keyWithIdentifier:identifier title:value output:value type:KBKeyTypeCharacter];
            k.caseVariant = KBKeyCaseVariantNone;
            return k;
        }
    }
    return nil;
}

- (KBKey *)kb_keyFromDef:(KBKeyboardKeyDef *)def identifier:(NSString *)identifier {
    KBKeyType type = [self kb_keyTypeForDef:def];
    NSString *title = def.title ?: @"";
    if (type == KBKeyTypeShift && self.shiftOn && def.selectedTitle.length > 0) {
        title = def.selectedTitle;
    }
    NSString *output = @"";
    switch (type) {
        case KBKeyTypeSpace:
            output = @" ";
            break;
        case KBKeyTypeReturn:
            output = @"\n";
            break;
        default:
            output = @"";
            break;
    }

    NSString *finalId = identifier;
    if ([identifier isEqualToString:@"emoji"]) {
        finalId = KBKeyIdentifierEmojiPanel;
    } else if ([identifier isEqualToString:@"send"]) {
        finalId = @"return";
    }

    KBKey *k = [KBKey keyWithIdentifier:finalId title:title output:output type:type];
    if (type == KBKeyTypeShift) {
        k.caseVariant = self.shiftOn ? KBKeyCaseVariantUpper : KBKeyCaseVariantLower;
    } else {
        k.caseVariant = KBKeyCaseVariantNone;
    }
    return k;
}

- (KBKeyType)kb_keyTypeForDef:(KBKeyboardKeyDef *)def {
    NSString *type = def.type.lowercaseString;
    if ([type isEqualToString:@"shift"]) return KBKeyTypeShift;
    if ([type isEqualToString:@"backspace"]) return KBKeyTypeBackspace;
    if ([type isEqualToString:@"mode"]) return KBKeyTypeModeChange;
    if ([type isEqualToString:@"symbolstoggle"]) return KBKeyTypeSymbolsToggle;
    if ([type isEqualToString:@"space"]) return KBKeyTypeSpace;
    if ([type isEqualToString:@"return"]) return KBKeyTypeReturn;
    if ([type isEqualToString:@"globe"]) return KBKeyTypeGlobe;
    return KBKeyTypeCustom;
}

- (NSString *)kb_identifierForSymbol:(NSString *)symbol {
    if (symbol.length == 0) { return nil; }
    static NSDictionary<NSString *, NSString *> *map = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        map = @{
            @"-": @"sym_minus",
            @"/": @"sym_slash",
            @":": @"sym_colon",
            @";": @"sym_semicolon",
            @"(": @"sym_paren_l",
            @")": @"sym_paren_r",
            @"¥": @"sym_money",
            @"￥": @"sym_money",
            @"&": @"sym_amp",
            @"@": @"sym_at",
            @"\"": @"sym_quote_double",
            @"“": @"sym_quote_double",
            @"”": @"sym_quote_double",
            @".": @"sym_dot",
            @",": @"sym_comma",
            @"?": @"sym_question",
            @"!": @"sym_exclam",
            @"'": @"sym_quote_single",
            @"‘": @"sym_quote_single",
            @"’": @"sym_quote_single",
            @"[": @"sym_bracket_l",
            @"]": @"sym_bracket_r",
            @"{": @"sym_brace_l",
            @"}": @"sym_brace_r",
            @"#": @"sym_hash",
            @"%": @"sym_percent",
            @"^": @"sym_caret",
            @"*": @"sym_asterisk",
            @"+": @"sym_plus",
            @"=": @"sym_equal",
            @"_": @"sym_underscore",
            @"\\": @"sym_backslash",
            @"|": @"sym_pipe",
            @"~": @"sym_tilde",
            @"<": @"sym_lt",
            @">": @"sym_gt",
            @"€": @"sym_euro",
            @"$": @"sym_dollar",
            @"·": @"sym_bullet"
        };
    });
    return map[symbol];
}

#pragma mark - Actions

- (void)onKeyTapped:(KBKeyButton *)sender {
    KBKey *key = sender.key;
    if (key.type == KBKeyTypeShift) {
        self.shiftOn = !self.shiftOn;
        [self reloadKeys];
        return;
    }
    if (key.type == KBKeyTypeSymbolsToggle) {
        // 在数字布局内切换 123 <-> #+=
        self.symbolsMoreOn = !self.symbolsMoreOn;
        [self reloadKeys];
        return;
    }
    if ([self.delegate respondsToSelector:@selector(keyboardView:didTapKey:)]) {
        [self.delegate keyboardView:self didTapKey:key];
    }
}

// 在字符键按下时，显示一个上方气泡预览（类似系统键盘）。
- (void)showPreviewForButton:(KBKeyButton *)button {
    KBKey *key = button.key;
    if (key.type != KBKeyTypeCharacter) return;

    if (!self.previewView) {
        self.previewView = [[KBKeyPreviewView alloc] initWithFrame:CGRectZero];
        self.previewView.hidden = YES;
        [self addSubview:self.previewView];
    }

    [self.previewView configureWithKey:key icon:button.iconView.image];

    // 计算预览视图位置：在按钮上方稍微偏上
    CGRect btnFrameInSelf = [button convertRect:button.bounds toView:self];
//    CGFloat previewWidth  = MAX(CGRectGetWidth(btnFrameInSelf) * 1.4, 42.0);
    CGFloat previewWidth = 42;
    CGFloat previewHeight = CGRectGetHeight(btnFrameInSelf) * 1.2;
    CGFloat centerX = CGRectGetMidX(btnFrameInSelf);
    CGFloat centerY = CGRectGetMinY(btnFrameInSelf) - previewHeight * 0.6;

    // 修复：原来写死 40，这里用真正计算出的 previewWidth
    self.previewView.frame = CGRectMake(0, 0, previewWidth, previewHeight);
    self.previewView.center = CGPointMake(centerX, centerY);
    self.previewView.alpha = 0.0;
    self.previewView.hidden = NO;

    [UIView animateWithDuration:kKBPreviewShowDuration
                          delay:0
                        options:UIViewAnimationOptionBeginFromCurrentState | UIViewAnimationOptionCurveEaseOut
                     animations:^{
                         self.previewView.alpha = 1.0;
                     }
                     completion:nil];
}

- (void)hidePreview {
    if (!self.previewView || self.previewView.isHidden) return;
    [UIView animateWithDuration:kKBPreviewHideDuration
                          delay:0
                        options:UIViewAnimationOptionBeginFromCurrentState | UIViewAnimationOptionCurveEaseIn
                     animations:^{
                         self.previewView.alpha = 0.0;
                     }
                     completion:^(BOOL finished) {
                         self.previewView.hidden = YES;
                     }];
}

#pragma mark - Lazy

- (UIView *)row1 { if (!_row1) _row1 = [UIView new]; return _row1; }
- (UIView *)row2 { if (!_row2) _row2 = [UIView new]; return _row2; }
- (UIView *)row3 { if (!_row3) _row3 = [UIView new]; return _row3; }
- (UIView *)row4 { if (!_row4) _row4 = [UIView new]; return _row4; }

@end