/*

     File: APLSimpleCoreTextView.m

 Abstract: 

 A view that draws text, reasons about layout, and manages a selection over its text range.

 IMPORTANT: Its use of CoreText is naive and inefficient, it deals only with left-to-right text layout, and it is by no means a good template for any text editor. It is a toy implementation included only to illustrate how to bind the system keyboard to some pre-existing text editor.

  Version: 2.0

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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

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 */

#import "APLSimpleCoreTextView.h"

#import <QuartzCore/CALayer.h>

#import "APLSimpleCaretView.h"

@interface APLSimpleCoreTextView ()

@property (nonatomic) NSDictionary *attributes;

@property (nonatomic) APLSimpleCaretView *caretView; // Subview that draws the insertion caret.

@end

// Helper function to obtain the intersection of two ranges.

NSRange RangeIntersection(NSRange first, NSRange second);

@implementation APLSimpleCoreTextView

{

    CTFramesetterRef _framesetter; // Cached Core Text framesetter.

    CTFrameRef _ctFrame; // Cached Core Text frame.

}

- (id)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        _contentText = @"";

        _caretView = [[APLSimpleCaretView alloc] initWithFrame:CGRectZero];

        self.layer.geometryFlipped = YES;  // For ease of interaction with the CoreText coordinate system.

        self.font = [UIFont systemFontOfSize:18];

        self.backgroundColor = [UIColor clearColor];

        self.contentMode = UIViewContentModeRedraw;

    }

    return self;

}

// Helper method to update our text storage when the text content has changed.

- (void)textChanged

{

    [self setNeedsDisplay];

    [self clearPreviousLayoutInformation];

    // Build the attributed string from our text data and string attribute data,

    NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:self.contentText attributes:self.attributes];

    // Create the Core Text framesetter using the attributed string.

    if (_framesetter != NULL) {

        CFRelease(_framesetter);

    }

    _framesetter = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)attributedString);

    [self updateCTFrame];

}

- (void)updateCTFrame

{

    // Create the Core Text frame using our current view rect bounds.

    UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.bounds];

    if (_ctFrame != NULL) {

        CFRelease(_ctFrame);

    }

    _ctFrame =  CTFramesetterCreateFrame(_framesetter, CFRangeMake(0, 0), [path CGPath], NULL);

}

-(void)setFrame:(CGRect)frame

{

    [super setFrame:frame];

    if (_ctFrame != NULL) {

        [self updateCTFrame];

    }

}

-(void)setBounds:(CGRect)bounds

{

    /*

     */

    [super setBounds:bounds];

    if(_ctFrame) {

        [self updateCTFrame];

    }

}

// Helper method for drawing the current selection range (as a simple filled rect).

- (void)drawRangeAsSelection:(NSRange)selectionRange

{

    // If not in editing mode, do not draw selection rectangles.

    if (!self.editing) {

        return;

    }

    // If the selection range is empty, do not draw.

    if (selectionRange.length == 0 || selectionRange.location == NSNotFound) {

        return;

    }

    // Set the fill color to the selection color.

    [[APLSimpleCoreTextView selectionColor] setFill];

    /*

     Iterate over the lines in our CTFrame, looking for lines that intersect with the given selection range, and draw a selection rect for each intersection.

     */

    CFArrayRef lines = CTFrameGetLines(_ctFrame);

    CFIndex linesCount = CFArrayGetCount(lines);

    for (CFIndex linesIndex = 0; linesIndex < linesCount; linesIndex++) {

        CTLineRef line = (CTLineRef) CFArrayGetValueAtIndex(lines, linesIndex);

        CFRange lineRange = CTLineGetStringRange(line);

        NSRange range = NSMakeRange(lineRange.location, lineRange.length);

        NSRange intersection = RangeIntersection(range, selectionRange);

        if (intersection.location != NSNotFound && intersection.length > 0) {

            // The text range for this line intersects our selection range.

            CGFloat xStart = CTLineGetOffsetForStringIndex(line, intersection.location, NULL);

            CGFloat xEnd = CTLineGetOffsetForStringIndex(line, intersection.location + intersection.length, NULL);

            CGPoint origin;

            // Get coordinate and bounds information for the intersection text range.

            CTFrameGetLineOrigins(_ctFrame, CFRangeMake(linesIndex, 0), &origin);

            CGFloat ascent, descent;

            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);

            // Create a rect for the intersection and draw it with selection color.

            CGRect selectionRect = CGRectMake(xStart, origin.y - descent, xEnd - xStart, ascent + descent);

            UIRectFill(selectionRect);

        }

    }

}

// Standard UIView drawRect override that uses Core Text to draw our text contents.

- (void)drawRect:(CGRect)rect

{

    // First draw selection / marked text, then draw text.

    [self drawRangeAsSelection:_selectedTextRange];

    [self drawRangeAsSelection:_markedTextRange];

    CTFrameDraw(_ctFrame, UIGraphicsGetCurrentContext());

}

// Public method to find the text range index for a given CGPoint.

- (NSInteger)closestIndexToPoint:(CGPoint)point

{

    /*

     Use Core Text to find the text index for a given CGPoint by iterating over the y-origin points for each line, finding the closest line, and finding the closest index within that line.

     */

    CFArrayRef lines = CTFrameGetLines(_ctFrame);

    CFIndex linesCount = CFArrayGetCount(lines);

    CGPoint origins[linesCount];

    CTFrameGetLineOrigins(_ctFrame, CFRangeMake(0, linesCount), origins);

    for (CFIndex linesIndex = 0; linesIndex < linesCount; linesIndex++) {

        if (point.y > origins[linesIndex].y) {

            // This line origin is closest to the y-coordinate of our point; now look for the closest string index in this line.

            CTLineRef line = (CTLineRef)CFArrayGetValueAtIndex(lines, linesIndex);

            return CTLineGetStringIndexForPosition(line, point);

        }

    }

    return  self.contentText.length;

}

/*

 Public method to determine the CGRect for the insertion point or selection, used when creating or updating the simple caret view instance.

 */

- (CGRect)caretRectForIndex:(int)index

{

    // Special case, no text.

    if (self.contentText.length == 0) {

        CGPoint origin = CGPointMake(CGRectGetMinX(self.bounds), CGRectGetMaxY(self.bounds) - self.font.leading);

        // Note: using fabs() for typically negative descender from fonts.

        return CGRectMake(origin.x, origin.y - fabs(self.font.descender), 3, self.font.ascender + fabs(self.font.descender));

    }

    // Iterate over our CTLines, looking for the line that encompasses the given range.

    CFArrayRef lines = CTFrameGetLines(_ctFrame);

    CFIndex linesCount = CFArrayGetCount(lines);

    // Special case, insertion point at final position in text after newline.

    if (index == self.contentText.length && [self.contentText characterAtIndex:(index - 1)] == '\n') {

        CTLineRef line = (CTLineRef)CFArrayGetValueAtIndex(lines, linesCount -1);

        CFRange range = CTLineGetStringRange(line);

        CGFloat xPos = CTLineGetOffsetForStringIndex(line, range.location, NULL);

        CGPoint origin;

        CGFloat ascent, descent;

        CTLineGetTypographicBounds(line, &ascent, &descent, NULL);

        CTFrameGetLineOrigins(_ctFrame, CFRangeMake(linesCount - 1, 0), &origin);

        // Place point after last line, including any font leading spacing if applicable.

        origin.y -= self.font.leading;

        return CGRectMake(xPos, origin.y - descent, 3, ascent + descent);

    }

    // Regular case, caret somewhere within our text content range.

    for (CFIndex linesIndex = 0; linesIndex < linesCount; linesIndex++) {

        CTLineRef line = (CTLineRef)CFArrayGetValueAtIndex(lines, linesIndex);

        CFRange range = CTLineGetStringRange(line);

        NSInteger localIndex = index - range.location;

        if (localIndex >= 0 && localIndex <= range.length) {

            // index is in the range for this line.

            CGFloat xPos = CTLineGetOffsetForStringIndex(line, index, NULL);

            CGPoint origin;

            CGFloat ascent, descent;

            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);

            CTFrameGetLineOrigins(_ctFrame, CFRangeMake(linesIndex, 0), &origin);

            // Make a small "caret" rect at the index position.

            return CGRectMake(xPos, origin.y - descent, 3, ascent + descent);

        }

    }

    return CGRectNull;

}

/*

 Public method to create a rect for a given range in the text contents.

 Called by our EditableTextRange to implement the required UITextInput:firstRectForRange method.

 */

- (CGRect)firstRectForRange:(NSRange)range;

{

    NSInteger index = range.location;

    // Iterate over the CTLines, looking for the line that encompasses the given range.

    CFArrayRef lines = CTFrameGetLines(_ctFrame);

    NSInteger linesCount = CFArrayGetCount(lines);

    for (CFIndex linesIndex = 0; linesIndex < linesCount; linesIndex++) {

        CTLineRef line = (CTLineRef)CFArrayGetValueAtIndex(lines, linesIndex);

        CFRange lineRange = CTLineGetStringRange(line);

        NSInteger localIndex = index - lineRange.location;

        if (localIndex >= 0 && localIndex < lineRange.length) {

            // For this sample, we use just the first line that intersects range.

            NSInteger finalIndex = MIN(lineRange.location + lineRange.length, range.location + range.length);

            // Create a rect for the given range within this line.

            CGFloat xStart = CTLineGetOffsetForStringIndex(line, index, NULL);

            CGFloat xEnd = CTLineGetOffsetForStringIndex(line, finalIndex, NULL);

            CGPoint origin;

            CTFrameGetLineOrigins(_ctFrame, CFRangeMake(linesIndex, 0), &origin);

            CGFloat ascent, descent;

            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);

            return CGRectMake(xStart, origin.y - descent, xEnd - xStart, ascent + descent);

        }

    }

    return CGRectNull;

}

// Helper method to update caretView when insertion point/selection changes.

- (void)selectionChanged

{

    // If not in editing mode, we don't show the caret.

    if (!self.editing) {

        [self.caretView removeFromSuperview];

        return;

    }

    /*

     If there is no selection range (always true for this sample), find the insert point rect and create a caretView to draw the caret at this position.

     */

    if (self.selectedTextRange.length == 0) {

        self.caretView.frame = [self caretRectForIndex:self.selectedTextRange.location];

        if (self.caretView.superview == nil) {

            [self addSubview:self.caretView];

            [self setNeedsDisplay];

        }

        // Set up a timer to "blink" the caret.

        [self.caretView delayBlink];

    }

    else {

        // If there is an actual selection, don't draw the insertion caret.

        [self.caretView removeFromSuperview];

        [self setNeedsDisplay];

    }

    if (self.markedTextRange.location != NSNotFound) {

        [self setNeedsDisplay];

    }

}

// Helper method to release our cached Core Text framesetter and frame.

- (void)clearPreviousLayoutInformation

{

    if (_framesetter != NULL) {

        CFRelease(_framesetter);

        _framesetter = NULL;

    }

    if (_ctFrame != NULL) {

        CFRelease(_ctFrame);

        _ctFrame = NULL;

    }

}

#pragma mark - Property accessor overrides

/*

 When setting the font, we need to additionally create and set the Core Text font object that corresponds to the UIFont being set.

 */

- (void)setFont:(UIFont *)newFont

{

    if (newFont != _font) {

        _font = newFont;

        // Find matching CTFont via name and size.

        CTFontRef ctFont = CTFontCreateWithName((__bridge CFStringRef) _font.fontName, _font.pointSize, NULL);

        // Set CTFont instance in our attributes dictionary, to be set on our attributed string.

        self.attributes = @{ (NSString *)kCTFontAttributeName : (__bridge id)ctFont };

        CFRelease(ctFont);

        [self textChanged];

    }

}

/*

 We need to call textChanged after setting the new property text to update layout.

 */

- (void)setContentText:(NSString *)text

{

    _contentText = [text copy];

    [self textChanged];

}

/*

 Set accessors should call selectionChanged to update view if necessary.

 */

- (void)setMarkedTextRange:(NSRange)range

{

    _markedTextRange = range;

    [self selectionChanged];

}

- (void)setSelectedTextRange:(NSRange)range

{

    _selectedTextRange = range;

    [self selectionChanged];

}

- (void)setEditing:(BOOL)editing

{

    _editing = editing;

    [self selectionChanged];

}

#pragma mark - Selection and caret colors

// Class method that returns current selection color (in this sample the color cannot be changed).

+ (UIColor *)selectionColor

{

    static UIColor *selectionColor = nil;

    if (selectionColor == nil) {

        selectionColor = [[UIColor alloc] initWithRed:0.25 green:0.50 blue:1.0 alpha:0.50];

    }

    return selectionColor;

}

// Class method that returns current caret color (in this sample the color cannot be changed).

+ (UIColor *)caretColor

{

    static UIColor *caretColor = nil;

    if (caretColor == nil) {

        caretColor = [[UIColor alloc] initWithRed:0.25 green:0.50 blue:1.0 alpha:1.0];

    }

    return caretColor;

}

@end

#pragma mark - Range intersection function

/*

 Helper function to obtain the intersection of two ranges (for handling selection range across multiple line ranges in drawRangeAsSelection).

 */

NSRange RangeIntersection(NSRange first, NSRange second)

{

    NSRange result = NSMakeRange(NSNotFound, 0);

    // Ensure first range does not start after second range.

    if (first.location > second.location) {

        NSRange tmp = first;

        first = second;

        second = tmp;

    }

    // Find the overlap intersection range between first and second.

    if (second.location < first.location + first.length) {

        result.location = second.location;

        NSUInteger end = MIN(first.location + first.length, second.location + second.length);

        result.length = end - result.location;

    }

    return result;

}