ReadViewSDK/Doc/WXRead/decompiled/WRCoreTextLayoutFrame.m

//
//  WRCoreTextLayoutFrame.m
//  WeRead
//
//  Reverse-engineered from binary analysis
//  Single page layout frame implementation
//
//  This file contains pseudo-code reconstruction of the WRCoreTextLayoutFrame
//  class based on ivar analysis, method signatures, and behavioral context.
//

#import "WRCoreTextLayoutFrame.h"
#import <CoreText/CoreText.h>

// Forward declarations for WeRead-specific classes
@class WRBookCoverView;
@class WRDiscover;
@class RACSubject;

#pragma mark - Internal Constants

// Threshold for avoid-page-break-inside calculation
static const CGFloat kPageBreakAvoidanceThreshold = 20.0;

// Maximum lines to remove for page break avoidance
static const NSUInteger kMaxLinesToRemove = 3;

#pragma mark - WRCoreTextLayoutLine Implementation

@implementation WRCoreTextLayoutLine

- (instancetype)initWithCTLine:(CTLineRef)ctLine origin:(CGPoint)origin range:(NSRange)range {
    self = [super init];
    if (self) {
        _ctLine = (CTLineRef)CFRetain(ctLine);
        _origin = origin;
        _stringRange = range;

        // Calculate typographic metrics
        CGFloat ascent, descent, leading;
        CTLineGetTypographicBounds(_ctLine, &ascent, &descent, &leading);

        _ascent = ascent;
        _descent = descent;
        _leading = leading;
        _height = ascent + descent + leading;
        _width = CTLineGetTypographicBounds(_ctLine, NULL, NULL, NULL);
    }
    return self;
}

- (void)dealloc {
    if (_ctLine) {
        CFRelease(_ctLine);
        _ctLine = NULL;
    }
}

- (BOOL)isLastLineInParagraph {
    // A line is the last in a paragraph if it ends with a newline
    // or if the next line starts a new paragraph
    CFRange cfRange = CTLineGetStringRange(_ctLine);
    if (cfRange.length == 0) return NO;

    NSUInteger endIndex = cfRange.location + cfRange.length - 1;
    // This would need access to the full attributed string to determine
    // For now, we use the stored property
    return _isLastLineInParagraph;
}

@end

#pragma mark - Private Interface

@interface WRCoreTextLayoutFrame () {
    // The CoreText frame object
    CTFrameRef _ctFrame;

    // Cached layout lines
    NSArray<WRCoreTextLayoutLine *> *_cachedLines;

    // Whether lines have been extracted
    BOOL _linesExtracted;

    // Render height cache
    CGFloat _cachedRenderHeight;
    BOOL _renderHeightCached;

    // Internal lock for thread safety
    NSLock *_frameLock;
}

@end

#pragma mark - WRCoreTextLayoutFrame Implementation

@implementation WRCoreTextLayoutFrame

#pragma mark - Lifecycle

- (instancetype)init {
    self = [super init];
    if (self) {
        [self commonInit];
    }
    return self;
}

- (instancetype)initWithCTFrame:(CTFrameRef)ctFrame range:(NSRange)range {
    self = [super init];
    if (self) {
        [self commonInit];
        [self setCTFrame:ctFrame range:range];
    }
    return self;
}

/**
 * Common initialization - sets up internal state.
 */
- (void)commonInit {
    _frameLock = [[NSLock alloc] init];
    _cachedLines = @[];
    _linesExtracted = NO;
    _renderHeightCached = NO;
    _cachedRenderHeight = 0;
    _customAttributes = [NSMutableDictionary dictionary];
    _visibleElements = [NSMutableArray array];
    _accessibilityElements = [NSMutableArray array];
    _computedValueCache = [NSMutableDictionary dictionary];
    _selectedLineIndices = [NSMutableSet set];
    _avoidPageBreakInside = NO;
    _numberOfColumns = 1;
    _columnGap = 20.0;
    _contentInsets = UIEdgeInsetsZero;
}

- (void)dealloc {
    if (_ctFrame) {
        CFRelease(_ctFrame);
        _ctFrame = NULL;
    }
}

#pragma mark - Property Accessors

- (void)setCTFrame:(CTFrameRef)ctFrame range:(NSRange)range {
    [_frameLock lock];

    if (_ctFrame) {
        CFRelease(_ctFrame);
    }

    _ctFrame = ctFrame ? (CTFrameRef)CFRetain(ctFrame) : NULL;
    _stringRange = range;

    // Invalidate cached data
    _linesExtracted = NO;
    _renderHeightCached = NO;
    _cachedLines = @[];

    [_frameLock unlock];
}

- (CTFrameRef)ctFrame {
    return _ctFrame;
}

- (void)setAvoidPageBreakInside:(BOOL)avoidPageBreakInside {
    _avoidPageBreakInside = avoidPageBreakInside;

    if (avoidPageBreakInside) {
        // When enabled, we need to check and potentially remove lines
        [self avoidPageBreakInsideByRemovingLastLinesIfNeeded];
    }
}

#pragma mark - Line Extraction

/**
 * Extracts layout lines from the CTFrame.
 *
 * This method iterates through the CTFrame's lines and creates
 * WRCoreTextLayoutLine wrapper objects with position information.
 *
 * Algorithm:
 * 1. Get array of CTLines from CTFrame
 * 2. For each CTLine:
 *    a. Get its origin from CTFrameGetLineOrigins
 *    b. Get the string range from CTLineGetStringRange
 *    c. Create WRCoreTextLayoutLine wrapper
 *    d. Determine if it's the last line in a paragraph
 * 3. Cache the results
 */
- (void)extractLines {
    if (_linesExtracted || !_ctFrame) {
        return;
    }

    [_frameLock lock];

    // Get the lines from the CTFrame
    CFArrayRef ctLines = CTFrameGetLines(_ctFrame);
    if (!ctLines) {
        [_frameLock unlock];
        return;
    }

    CFIndex lineCount = CFArrayGetCount(ctLines);
    if (lineCount == 0) {
        _cachedLines = @[];
        _linesExtracted = YES;
        [_frameLock unlock];
        return;
    }

    // Get line origins
    CGPoint *origins = (CGPoint *)malloc(sizeof(CGPoint) * lineCount);
    CTFrameGetLineOrigins(_ctFrame, CFRangeMake(0, 0), origins);

    NSMutableArray<WRCoreTextLayoutLine *> *lines = [NSMutableArray arrayWithCapacity:lineCount];

    for (CFIndex i = 0; i < lineCount; i++) {
        CTLineRef ctLine = CFArrayGetValueAtIndex(ctLines, i);

        // Get the string range for this line
        CFRange cfRange = CTLineGetStringRange(ctLine);
        NSRange range = NSMakeRange(cfRange.location, cfRange.length);

        // Create layout line wrapper
        WRCoreTextLayoutLine *layoutLine = [[WRCoreTextLayoutLine alloc]
            initWithCTLine:ctLine
                    origin:origins[i]
                     range:range];

        // Determine if this is the last line in a paragraph
        // Check if the next line starts a new paragraph or if this is the last line
        if (i == lineCount - 1) {
            layoutLine.isLastLineInParagraph = YES;
        } else {
            // Check if the character after this line is a newline
            NSUInteger endOfLine = range.location + range.length;
            if (endOfLine < [_attributedString length]) {
                unichar nextChar = [[_attributedString string] characterAtIndex:endOfLine];
                layoutLine.isLastLineInParagraph = (nextChar == '\n' || nextChar == '\r');
            }
        }

        [lines addObject:layoutLine];
    }

    free(origins);

    _cachedLines = [lines copy];
    _linesExtracted = YES;

    [_frameLock unlock];
}

/**
 * Returns the array of layout lines.
 * Triggers extraction if not already done.
 */
- (NSArray<WRCoreTextLayoutLine *> *)lines {
    [self extractLines];
    return _cachedLines;
}

- (NSUInteger)lineCount {
    return [[self lines] count];
}

- (WRCoreTextLayoutLine *)lineAtIndex:(NSUInteger)index {
    NSArray *lines = [self lines];
    if (index < [lines count]) {
        return lines[index];
    }
    return nil;
}

#pragma mark - Height Calculation

/**
 * Calculates the rendered content height.
 *
 * This method determines the actual height of the rendered content
 * by examining the position of the last line. The rendered height
 * may be less than the frame height if there's unused space at the bottom.
 *
 * Algorithm:
 * 1. Get all layout lines
 * 2. Find the lowest line (by origin.y - descent)
 * 3. Return that position as the rendered height
 *
 * @return The rendered content height in points
 */
- (CGFloat)getRenderHeight {
    [_frameLock lock];

    if (_renderHeightCached) {
        [_frameLock unlock];
        return _cachedRenderHeight;
    }

    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    if ([lines count] == 0) {
        _cachedRenderHeight = 0;
        _renderHeightCached = YES;
        [_frameLock unlock];
        return 0;
    }

    // Find the lowest point of the last line
    // The last line's bottom edge (origin.y - descent) gives us the content height
    WRCoreTextLayoutLine *lastLine = [lines lastObject];

    // In CoreText, the coordinate system is flipped (origin at bottom-left)
    // The line's origin.y is the baseline position
    // To get the bottom of the line, we subtract the descent
    CGFloat lastLineBottom = lastLine.origin.y - lastLine.descent;

    // The rendered height is from the top of the frame to the bottom of the last line
    // Since CoreText uses bottom-left origin, we need to convert
    CGFloat frameHeight = _frame.size.height;
    _cachedRenderHeight = frameHeight - lastLineBottom;

    // Add content insets
    _cachedRenderHeight += _contentInsets.top + _contentInsets.bottom;

    _renderHeightCached = YES;

    [_frameLock unlock];

    return _cachedRenderHeight;
}

/**
 * Returns the descent of the last line.
 * Used for precise baseline alignment at the bottom of the page.
 */
- (CGFloat)lastLineDescent {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];
    if ([lines count] == 0) {
        return 0;
    }

    WRCoreTextLayoutLine *lastLine = [lines lastObject];
    return lastLine.descent;
}

#pragma mark - Drawing

/**
 * Draws the layout frame content into a CGContext.
 *
 * This is the primary rendering method for the reading view.
 * It performs the following steps:
 *
 * 1. Save the graphics state
 * 2. Flip the coordinate system (UIKit vs CoreText)
 * 3. Apply position offset
 * 4. Draw text using CTFrameDraw
 * 5. Draw image attachments at their positions
 * 6. Draw decorative elements (strikethrough, underline, highlights)
 * 7. Restore the graphics state
 *
 * @param context The CGContext to draw into
 * @param image Optional image (used for cover pages)
 * @param size The size of the drawing area
 * @param rect The rectangle to draw within
 * @param position The position offset for multi-page layouts
 */
- (void)drawInContext:(CGContextRef)context
                image:(UIImage *)image
                 size:(CGSize)size
               inRect:(CGRect)rect
             position:(CGPoint)position {
    if (!context || !_ctFrame) {
        return;
    }

    [_frameLock lock];

    // Save graphics state before drawing
    CGContextSaveGState(context);

    // CoreText uses a bottom-left origin, UIKit uses top-left
    // We need to flip the coordinate system
    CGContextTranslateCTM(context, 0, rect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // Apply the position offset (for multi-column or multi-page layouts)
    CGContextTranslateCTM(context, position.x, -position.y);

    // Apply content insets
    CGContextTranslateCTM(context, _contentInsets.left, _contentInsets.bottom);

    // Draw the optional image (for cover pages or special layouts)
    if (image) {
        [self drawCoverImage:image inContext:context rect:rect];
    }

    // Draw the main text content
    CTFrameDraw(_ctFrame, context);

    // Draw image attachments
    [self drawAttachmentsInContext:context inRect:rect];

    // Draw decorative elements
    [self drawDecorativeElementsInContext:context inRect:rect];

    // Restore graphics state
    CGContextRestoreGState(context);

    [_frameLock unlock];
}

/**
 * Draws only the text content without images.
 */
- (void)drawTextInContext:(CGContextRef)context inRect:(CGRect)rect {
    if (!context || !_ctFrame) {
        return;
    }

    [_frameLock lock];

    CGContextSaveGState(context);

    // Flip coordinate system
    CGContextTranslateCTM(context, 0, rect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // Apply content insets
    CGContextTranslateCTM(context, _contentInsets.left, _contentInsets.bottom);

    // Draw just the text
    CTFrameDraw(_ctFrame, context);

    CGContextRestoreGState(context);

    [_frameLock unlock];
}

/**
 * Draws image attachments at their calculated positions.
 *
 * This method iterates through the attachment array and draws each
 * image at the position determined by the layout engine.
 *
 * The attachment positions are calculated during layout and stored
 * in the attachments array. Each attachment has:
 * - A position (origin point)
 * - A size
 * - An image reference
 */
- (void)drawAttachmentsInContext:(CGContextRef)context inRect:(CGRect)rect {
    if (!_attachments || [_attachments count] == 0) {
        return;
    }

    for (NSDictionary *attachment in _attachments) {
        UIImage *image = attachment[@"image"];
        NSValue *positionValue = attachment[@"position"];
        NSValue *sizeValue = attachment[@"size"];

        if (!image || !positionValue || !sizeValue) {
            continue;
        }

        CGPoint imagePosition = [positionValue CGPointValue];
        CGSize imageSize = [sizeValue CGSizeValue];

        CGRect imageRect = CGRectMake(imagePosition.x,
                                      imagePosition.y,
                                      imageSize.width,
                                      imageSize.height);

        // Draw the image
        CGContextDrawImage(context, imageRect, image.CGImage);
    }
}

/**
 * Draws decorative elements like strikethrough and underline.
 */
- (void)drawDecorativeElementsInContext:(CGContextRef)context inRect:(CGRect)rect {
    // Draw strikethrough lines
    if (_strikethroughRanges) {
        [self drawStrikethroughInContext:context];
    }

    // Draw underlines
    if (_underlineRanges) {
        [self drawUnderlineInContext:context];
    }

    // Draw highlights
    if (_highlightRanges) {
        [self drawHighlightsInContext:context];
    }
}

/**
 * Draws strikethrough lines for the specified ranges.
 */
- (void)drawStrikethroughInContext:(CGContextRef)context {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSValue *rangeValue in _strikethroughRanges) {
        NSRange range = [rangeValue rangeValue];

        // Find lines that intersect with this range
        for (WRCoreTextLayoutLine *line in lines) {
            NSRange lineRange = line.stringRange;
            NSRange intersection = NSIntersectionRange(range, lineRange);

            if (intersection.length > 0) {
                // Get the x positions for the strikethrough
                CGFloat startX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location, NULL);
                CGFloat endX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location + intersection.length, NULL);

                // Strikethrough is at the middle of the line
                CGFloat y = line.origin.y + (line.ascent * 0.3);

                CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
                CGContextSetLineWidth(context, 1.0);

                CGContextMoveToPoint(context, line.origin.x + startX, y);
                CGContextAddLineToPoint(context, line.origin.x + endX, y);
                CGContextStrokePath(context);
            }
        }
    }
}

/**
 * Draws underlines for the specified ranges.
 */
- (void)drawUnderlineInContext:(CGContextRef)context {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSDictionary *underlineData in _underlineRanges) {
        NSRange range = [underlineData[@"range"] rangeValue];
        UIColor *color = underlineData[@"color"] ?: [UIColor blueColor];

        for (WRCoreTextLayoutLine *line in lines) {
            NSRange lineRange = line.stringRange;
            NSRange intersection = NSIntersectionRange(range, lineRange);

            if (intersection.length > 0) {
                CGFloat startX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location, NULL);
                CGFloat endX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location + intersection.length, NULL);

                // Underline is below the baseline
                CGFloat y = line.origin.y - line.descent;

                CGContextSetStrokeColorWithColor(context, color.CGColor);
                CGContextSetLineWidth(context, 1.0);

                CGContextMoveToPoint(context, line.origin.x + startX, y);
                CGContextAddLineToPoint(context, line.origin.x + endX, y);
                CGContextStrokePath(context);
            }
        }
    }
}

/**
 * Draws highlight backgrounds for the specified ranges.
 */
- (void)drawHighlightsInContext:(CGContextRef)context {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSDictionary *highlightData in _highlightRanges) {
        NSRange range = [highlightData[@"range"] rangeValue];
        UIColor *color = highlightData[@"color"] ?: [UIColor yellowColor];

        for (WRCoreTextLayoutLine *line in lines) {
            NSRange lineRange = line.stringRange;
            NSRange intersection = NSIntersectionRange(range, lineRange);

            if (intersection.length > 0) {
                CGFloat startX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location, NULL);
                CGFloat endX = CTLineGetOffsetForStringIndex(
                    line.ctLine, intersection.location + intersection.length, NULL);

                // Highlight rect from descent to ascent
                CGFloat y = line.origin.y - line.descent;
                CGFloat height = line.ascent + line.descent;

                CGRect highlightRect = CGRectMake(
                    line.origin.x + startX,
                    y,
                    endX - startX,
                    height
                );

                CGContextSetFillColorWithColor(context, [color colorWithAlphaComponent:0.3].CGColor);
                CGContextFillRect(context, highlightRect);
            }
        }
    }
}

/**
 * Draws a cover image for special pages.
 */
- (void)drawCoverImage:(UIImage *)image inContext:(CGContextRef)context rect:(CGRect)rect {
    if (!image) return;

    // Scale the image to fit the frame while maintaining aspect ratio
    CGSize imageSize = image.size;
    CGSize frameSize = rect.size;

    CGFloat widthRatio = frameSize.width / imageSize.width;
    CGFloat heightRatio = frameSize.height / imageSize.height;
    CGFloat scale = MIN(widthRatio, heightRatio);

    CGSize scaledSize = CGSizeMake(imageSize.width * scale, imageSize.height * scale);

    // Center the image in the frame
    CGFloat x = (frameSize.width - scaledSize.width) / 2;
    CGFloat y = (frameSize.height - scaledSize.height) / 2;

    CGRect imageRect = CGRectMake(x, y, scaledSize.width, scaledSize.height);

    CGContextDrawImage(context, imageRect, image.CGImage);
}

#pragma mark - Page Break Avoidance

/**
 * Implements the CSS 'avoid-page-break-inside' property.
 *
 * When an element (like a table, code block, or list) has this property,
 * we need to ensure it doesn't break across pages. If it would break,
 * we remove the last few lines to make room for the element on the next page.
 *
 * Algorithm:
 * 1. Check if avoidPageBreakInside is enabled
 * 2. Find elements with this property in the current frame
 * 3. For each element, check if it would break
 * 4. If it would break, remove lines from the end until the element fits
 * 5. Return whether any lines were removed
 *
 * @return YES if lines were removed to avoid page break
 */
- (BOOL)avoidPageBreakInsideByRemovingLastLinesIfNeeded {
    if (!_avoidPageBreakInside) {
        return NO;
    }

    [_frameLock lock];

    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];
    if ([lines count] == 0) {
        [_frameLock unlock];
        return NO;
    }

    // Check if any line has the avoid-page-break-inside attribute
    // This would be set in the attributed string attributes
    BOOL needsRemoval = NO;
    NSUInteger linesToRemove = 0;

    // Iterate from the end to find lines that shouldn't be broken
    for (NSInteger i = [lines count] - 1; i >= 0; i--) {
        WRCoreTextLayoutLine *line = lines[i];
        NSRange range = line.stringRange;

        // Check if this line is part of an element with avoid-page-break-inside
        if ([self shouldAvoidPageBreakInRange:range]) {
            // Check if the element starts before this line
            // If so, we need to remove this line and possibly more
            needsRemoval = YES;
            linesToRemove++;

            // Limit the number of lines we remove
            if (linesToRemove >= kMaxLinesToRemove) {
                break;
            }
        } else if (needsRemoval) {
            // We've found a line that doesn't need avoidance, stop
            break;
        }
    }

    if (needsRemoval && linesToRemove > 0) {
        // Remove the last N lines
        NSMutableArray *mutableLines = [_cachedLines mutableCopy];
        [mutableLines removeObjectsInRange:
            NSMakeRange([mutableLines count] - linesToRemove, linesToRemove)];
        _cachedLines = [mutableLines copy];

        // Update the CTFrame to reflect the removal
        // This requires recreating the frame with a shorter range
        [self rebuildFrameWithoutLastLines:linesToRemove];

        [_frameLock unlock];
        return YES;
    }

    [_frameLock unlock];
    return NO;
}

/**
 * Checks if a text range has the avoid-page-break-inside property.
 */
- (BOOL)shouldAvoidPageBreakInRange:(NSRange)range {
    if (!_attributedString || range.location >= [_attributedString length]) {
        return NO;
    }

    // Check the attributes at the start of the range
    NSDictionary *attrs = [_attributedString attributesAtIndex:range.location
                                                effectiveRange:NULL];

    // Check for our custom avoid-page-break-inside attribute
    NSNumber *avoidBreak = attrs[@"WRAvoidPageBreakInside"];
    if ([avoidBreak boolValue]) {
        return YES;
    }

    // Also check for block-level elements that shouldn't break
    NSString *blockType = attrs[@"WRBlockType"];
    if ([blockType isEqualToString:@"table"] ||
        [blockType isEqualToString:@"code"] ||
        [blockType isEqualToString:@"list"] ||
        [blockType isEqualToString:@"blockquote"]) {
        return YES;
    }

    return NO;
}

/**
 * Rebuilds the CTFrame without the last N lines.
 * This is used after avoidPageBreakInside removes lines.
 */
- (void)rebuildFrameWithoutLastLines:(NSUInteger)count {
    if (!_ctFrame || count == 0) {
        return;
    }

    // Get the current lines
    NSArray<WRCoreTextLayoutLine *> *lines = _cachedLines;
    if ([lines count] == 0) {
        return;
    }

    // Calculate the new end range
    WRCoreTextLayoutLine *lastLine = [lines lastObject];
    NSUInteger newEnd = lastLine.stringRange.location + lastLine.stringRange.length;

    // Update the string range
    _stringRange = NSMakeRange(_stringRange.location, newEnd - _stringRange.location);

    // Note: In a real implementation, we would need to recreate the CTFrame
    // with the updated range. This requires access to the CTTypesetter.
    // For this reconstruction, we just update the range metadata.
}

#pragma mark - Hit Testing

/**
 * Returns the character index at a given point.
 *
 * Uses CTLineGetStringIndexForPosition to find which character
 * is at the given point. This is used for text selection and
 * tap handling.
 *
 * @param point The point to test (in the frame's coordinate system)
 * @return The character index, or NSNotFound
 */
- (NSUInteger)characterIndexAtPoint:(CGPoint)point {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (WRCoreTextLayoutLine *line in lines) {
        // Check if the point is within this line's vertical bounds
        CGFloat lineTop = line.origin.y + line.ascent;
        CGFloat lineBottom = line.origin.y - line.descent;

        if (point.y >= lineBottom && point.y <= lineTop) {
            // Use CTLine to find the character index
            CFIndex index = CTLineGetStringIndexForPosition(line.ctLine, point);

            if (index != kCFNotFound) {
                return (NSUInteger)index;
            }
        }
    }

    return NSNotFound;
}

/**
 * Returns the line index at a given point.
 */
- (NSUInteger)lineIndexAtPoint:(CGPoint)point {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSUInteger i = 0; i < [lines count]; i++) {
        WRCoreTextLayoutLine *line = lines[i];

        CGFloat lineTop = line.origin.y + line.ascent;
        CGFloat lineBottom = line.origin.y - line.descent;

        if (point.y >= lineBottom && point.y <= lineTop) {
            return i;
        }
    }

    return NSNotFound;
}

/**
 * Returns the rect for a character at the given index.
 */
- (CGRect)rectForCharacterAtIndex:(NSUInteger)index {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (WRCoreTextLayoutLine *line in lines) {
        NSRange range = line.stringRange;

        if (index >= range.location && index < range.location + range.length) {
            // Get the x position for this character
            CGFloat x = CTLineGetOffsetForStringIndex(line.ctLine, index, NULL);

            return CGRectMake(line.origin.x + x,
                            line.origin.y - line.descent,
                            1, // Width of 1 character
                            line.height);
        }
    }

    return CGRectNull;
}

#pragma mark - Selection

/**
 * Returns the currently selected text.
 */
- (NSString *)selectedText {
    NSArray<NSValue *> *ranges = [self selectedRanges];
    if ([ranges count] == 0) {
        return nil;
    }

    NSMutableString *selectedText = [NSMutableString string];

    for (NSValue *rangeValue in ranges) {
        NSRange range = [rangeValue rangeValue];
        NSString *substring = [_attributedString.string substringWithRange:range];
        [selectedText appendString:substring];
    }

    return [selectedText copy];
}

/**
 * Returns the ranges of selected text.
 */
- (NSArray<NSValue *> *)selectedRanges {
    NSMutableArray<NSValue *> *ranges = [NSMutableArray array];

    // Build ranges from selected line indices
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSUInteger i = 0; i < [lines count]; i++) {
        if ([_selectedLineIndices containsObject:@(i)]) {
            WRCoreTextLayoutLine *line = lines[i];
            [ranges addObject:[NSValue valueWithRange:line.stringRange]];
        }
    }

    return [ranges copy];
}

/**
 * Selects text in the given range.
 */
- (void)selectTextInRange:(NSRange)range {
    NSArray<WRCoreTextLayoutLine *> *lines = [self lines];

    for (NSUInteger i = 0; i < [lines count]; i++) {
        WRCoreTextLayoutLine *line = lines[i];
        NSRange intersection = NSIntersectionRange(range, line.stringRange);

        if (intersection.length > 0) {
            [_selectedLineIndices addObject:@(i)];
        }
    }

    // Notify via RACSubject
    [_layoutChangeSubject sendNext:@{
        @"type": @"selection",
        @"range": [NSValue valueWithRange:range]
    }];
}

/**
 * Clears the current selection.
 */
- (void)clearSelection {
    [_selectedLineIndices removeAllObjects];

    [_layoutChangeSubject sendNext:@{
        @"type": @"selectionCleared"
    }];
}

#pragma mark - Search

/**
 * Highlights search results within this frame.
 *
 * @param searchString The string to search for
 * @return The number of matches found
 */
- (NSUInteger)highlightSearchResults:(NSString *)searchString {
    if (!searchString || !_attributedString) {
        return 0;
    }

    NSMutableArray<NSValue *> *results = [NSMutableArray array];
    NSString *fullText = _attributedString.string;

    // Use NSString's rangeOfString for searching
    NSRange searchRange = NSMakeRange(0, [fullText length]);

    while (searchRange.location < [fullText length]) {
        NSRange foundRange = [fullText rangeOfString:searchString
                                             options:NSCaseInsensitiveSearch
                                               range:searchRange];

        if (foundRange.location == NSNotFound) {
            break;
        }

        [results addObject:[NSValue valueWithRange:foundRange]];

        // Move search range forward
        searchRange.location = foundRange.location + foundRange.length;
        searchRange.length = [fullText length] - searchRange.location;
    }

    // Store results
    _searchResultString = searchString;
    _searchResultRanges = [results copy];

    // Create highlight ranges
    NSMutableArray *highlights = [NSMutableArray array];
    UIColor *highlightColor = [UIColor yellowColor];

    for (NSValue *rangeValue in results) {
        [highlights addObject:@{
            @"range": rangeValue,
            @"color": highlightColor
        }];
    }

    _highlightRanges = [highlights copy];

    return [results count];
}

/**
 * Clears all search result highlights.
 */
- (void)clearSearchHighlights {
    _searchResultString = nil;
    _searchResultRanges = nil;
    _highlightRanges = nil;
}

@end