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

#import "KBKeyboardView.h"
#import "KBKeyButton.h"
#import "KBKey.h"
#import "KBResponderUtils.h" // 封装的响应链工具
#import "KBSkinManager.h"
#import "KBKeyPreviewView.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 kKBBackspaceLongPressMinDuration = 0.35;
static const NSTimeInterval kKBBackspaceRepeatInterval = 0.06;
static const NSTimeInterval kKBBackspaceChunkStartDelay = 0.7;
static const NSTimeInterval kKBBackspaceChunkRepeatInterval = 0.1;
static const NSTimeInterval kKBBackspaceChunkFastDelay = 1.4;
static const NSInteger kKBBackspaceChunkSize = 6;
static const NSInteger kKBBackspaceChunkSizeFast = 12;

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;

typedef NS_ENUM(NSInteger, KBBackspaceChunkClass) {
    KBBackspaceChunkClassUnknown = 0,
    KBBackspaceChunkClassWhitespace,
    KBBackspaceChunkClassASCIIWord,
    KBBackspaceChunkClassPunctuation,
    KBBackspaceChunkClassOther
};

@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;
// 长按退格的一次次删除控制标记（不使用 NSTimer，仅用 GCD 递归调度）
@property (nonatomic, assign) BOOL backspaceHoldActive;
@property (nonatomic, assign) NSTimeInterval backspaceHoldStartTime;
@property (nonatomic, strong) KBKeyPreviewView *previewView;
@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 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];

    [self.row1 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.mas_top).offset(kKBRowVerticalSpacing);
        make.left.right.equalTo(self);
        make.height.mas_equalTo(kKBRowHeight);
    }];
    [self.row2 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row1.mas_bottom).offset(kKBRowVerticalSpacing);
        make.left.right.equalTo(self);
        make.height.equalTo(self.row1);
    }];
    [self.row3 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row2.mas_bottom).offset(kKBRowVerticalSpacing);
        make.left.right.equalTo(self);
        make.height.equalTo(self.row1);
    }];
    [self.row4 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.row3.mas_bottom).offset(kKBRowVerticalSpacing);
        make.left.right.equalTo(self);
        make.height.equalTo(self.row1);
        make.bottom.equalTo(self.mas_bottom).offset(-6);
    }];
}

#pragma mark - Public

- (void)reloadKeys {
    // 移除旧按钮
    for (UIView *row in @[self.row1, self.row2, self.row3, self.row4]) {
        [row.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    }

    self.keysForRows = [self buildKeysForCurrentLayout];
    if (self.keysForRows.count < 4) return;

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

    // 第二行：字母布局时通过左右等宽占位让整行居中
    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]];
}

#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 *customAI = [KBKey keyWithIdentifier:@"ai"
                                         title:@"AI"
                                        output:@""
                                          type:KBKeyTypeCustom];
    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, customAI, 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 *customAI = [KBKey keyWithIdentifier:@"ai"
                                         title:@"AI"
                                        output:@""
                                          type:KBKeyTypeCustom];
    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, customAI, emoji, space, ret ];
}

#pragma mark - Row Building

- (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、AI、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];

        // ⌫ 长按：开始连续逐个删除（无需 NSTimer）。使用 UILongPressGestureRecognizer 识别长按
        if (key.type == KBKeyTypeBackspace) {
            UILongPressGestureRecognizer *lp =
            [[UILongPressGestureRecognizer alloc] initWithTarget:self
                                                          action:@selector(onBackspaceLongPress:)];
            lp.minimumPressDuration = kKBBackspaceLongPressMinDuration;
            lp.cancelsTouchesInView = YES; // 被识别为长按时，取消普通点击
            [btn addGestureRecognizer:lp];
        }

        // 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、AI、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/AI/#+= 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、AI：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 - 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;
                     }];
}

// 长按退格：先连续单删，稍后切换为按段删除；松手停止。（不使用 NSTimer/DisplayLink）
- (void)onBackspaceLongPress:(UILongPressGestureRecognizer *)gr {
    switch (gr.state) {
        case UIGestureRecognizerStateBegan: {
            self.backspaceHoldActive = YES;
            self.backspaceHoldStartTime = [NSDate date].timeIntervalSinceReferenceDate;
            [self kb_backspaceStep];
        } break;
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
        case UIGestureRecognizerStateFailed: {
            self.backspaceHoldActive = NO;
        } break;
        default: break;
    }
}

#pragma mark - Helpers

// 单步删除并在需要时安排下一次，直到松手或无内容
- (void)kb_backspaceStep {
    if (!self.backspaceHoldActive) { return; }
    UIInputViewController *ivc = KBFindInputViewController(self);
    if (!ivc) { self.backspaceHoldActive = NO; return; }
    id<UITextDocumentProxy> proxy = ivc.textDocumentProxy;
    NSString *before = proxy.documentContextBeforeInput ?: @"";
    if (before.length <= 0) { self.backspaceHoldActive = NO; return; }
    NSTimeInterval elapsed = [NSDate date].timeIntervalSinceReferenceDate - self.backspaceHoldStartTime;
    NSInteger deleteCount = [self kb_backspaceDeleteCountForContext:before elapsed:elapsed];
    for (NSInteger i = 0; i < deleteCount; i++) {
        [proxy deleteBackward];
    }

    NSTimeInterval interval = [self kb_backspaceRepeatIntervalForElapsed:elapsed];
    __weak typeof(self) weakSelf = self;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW,
                                 (int64_t)(interval * NSEC_PER_SEC)),
                   dispatch_get_main_queue(), ^{
        __strong typeof(weakSelf) selfStrong = weakSelf;
        [selfStrong kb_backspaceStep];
    });
}

- (NSTimeInterval)kb_backspaceRepeatIntervalForElapsed:(NSTimeInterval)elapsed {
    if (elapsed >= kKBBackspaceChunkStartDelay) {
        return kKBBackspaceChunkRepeatInterval;
    }
    return kKBBackspaceRepeatInterval;
}

- (NSInteger)kb_backspaceDeleteCountForContext:(NSString *)context elapsed:(NSTimeInterval)elapsed {
    if (elapsed < kKBBackspaceChunkStartDelay) {
        return 1;
    }
    NSInteger maxCount = (elapsed >= kKBBackspaceChunkFastDelay)
                         ? kKBBackspaceChunkSizeFast : kKBBackspaceChunkSize;
    return [self kb_backspaceChunkDeleteCountForContext:context maxCount:maxCount];
}

- (NSInteger)kb_backspaceChunkDeleteCountForContext:(NSString *)context maxCount:(NSInteger)maxCount {
    if (context.length == 0) { return 1; }

    static NSCharacterSet *whitespaceSet = nil;
    static NSCharacterSet *asciiWordSet = nil;
    static NSCharacterSet *punctuationSet = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        whitespaceSet = [NSCharacterSet whitespaceAndNewlineCharacterSet];
        asciiWordSet = [NSCharacterSet characterSetWithCharactersInString:
                        @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"];
        punctuationSet = [NSCharacterSet punctuationCharacterSet];
    });

    __block NSInteger deleteCount = 0;
    __block KBBackspaceChunkClass chunkClass = KBBackspaceChunkClassUnknown;
    [context enumerateSubstringsInRange:NSMakeRange(0, context.length)
                                options:NSStringEnumerationByComposedCharacterSequences | NSStringEnumerationReverse
                             usingBlock:^(NSString *substring, __unused NSRange substringRange, __unused NSRange enclosingRange, BOOL *stop) {
        if (substring.length == 0) { return; }
        KBBackspaceChunkClass currentClass = KBBackspaceChunkClassOther;
        if ([substring rangeOfCharacterFromSet:whitespaceSet].location != NSNotFound) {
            currentClass = KBBackspaceChunkClassWhitespace;
        } else if ([substring rangeOfCharacterFromSet:asciiWordSet].location != NSNotFound) {
            currentClass = KBBackspaceChunkClassASCIIWord;
        } else if ([substring rangeOfCharacterFromSet:punctuationSet].location != NSNotFound) {
            currentClass = KBBackspaceChunkClassPunctuation;
        }

        if (chunkClass == KBBackspaceChunkClassUnknown) {
            chunkClass = currentClass;
        } else if (chunkClass != currentClass) {
            *stop = YES;
            return;
        }

        deleteCount += 1;
        if (deleteCount >= maxCount) {
            *stop = YES;
        }
    }];

    return MAX(deleteCount, 1);
}

#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