/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/

#import "NSTextStorage+FontScaling.h"

typedef NS_OPTIONS(NSInteger, RCTTextSizeComparisonOptions) {
RCTTextSizeComparisonSmaller = 1 << 0,
RCTTextSizeComparisonLarger = 1 << 1,
RCTTextSizeComparisonWithinRange = 1 << 2,
};

@implementation NSTextStorage (FontScaling)

- (void)scaleFontSizeToFitSize:(CGSize)size
minimumFontSize:(CGFloat)minimumFontSize
maximumFontSize:(CGFloat)maximumFontSize
{
CGFloat bottomRatio = 1.0 / 128.0;
CGFloat topRatio = 128.0;
CGFloat ratio = 1.0;

NSAttributedString *originalAttributedString = [self copy];

CGFloat lastRatioWhichFits = 0.02;

while (true) {
[self scaleFontSizeWithRatio:ratio minimumFontSize:minimumFontSize maximumFontSize:maximumFontSize];

RCTTextSizeComparisonOptions comparsion = [self compareToSize:size thresholdRatio:0.01];

if ((comparsion & RCTTextSizeComparisonWithinRange) && (comparsion & RCTTextSizeComparisonSmaller)) {
return;
} else if (comparsion & RCTTextSizeComparisonSmaller) {
bottomRatio = ratio;
lastRatioWhichFits = ratio;
} else {
topRatio = ratio;
}

ratio = (topRatio + bottomRatio) / 2.0;

CGFloat kRatioThreshold = 0.005;
if (ABS(topRatio - bottomRatio) < kRatioThreshold || ABS(topRatio - ratio) < kRatioThreshold ||
ABS(bottomRatio - ratio) < kRatioThreshold) {
[self replaceCharactersInRange:(NSRange){0, self.length} withAttributedString:originalAttributedString];

[self scaleFontSizeWithRatio:lastRatioWhichFits minimumFontSize:minimumFontSize maximumFontSize:maximumFontSize];
return;
}

[self replaceCharactersInRange:(NSRange){0, self.length} withAttributedString:originalAttributedString];
}
}

- (RCTTextSizeComparisonOptions)compareToSize:(CGSize)size thresholdRatio:(CGFloat)thresholdRatio
{
NSLayoutManager *layoutManager = self.layoutManagers.firstObject;
NSTextContainer *textContainer = layoutManager.textContainers.firstObject;

[layoutManager ensureLayoutForTextContainer:textContainer];

// Does it fit the text container?
NSRange glyphRange = [layoutManager glyphRangeForTextContainer:textContainer];
NSRange truncatedGlyphRange = [layoutManager truncatedGlyphRangeInLineFragmentForGlyphAtIndex:glyphRange.length - 1];

if (truncatedGlyphRange.location != NSNotFound) {
return RCTTextSizeComparisonLarger;
}

CGSize measuredSize = [layoutManager usedRectForTextContainer:textContainer].size;

// Does it fit the size?
BOOL fitsSize = size.width >= measuredSize.width && size.height >= measuredSize.height;

CGSize thresholdSize = (CGSize){
size.width * thresholdRatio,
size.height * thresholdRatio,
};

RCTTextSizeComparisonOptions result = 0;

result |= (fitsSize) ? RCTTextSizeComparisonSmaller : RCTTextSizeComparisonLarger;

if (ABS(measuredSize.width - size.width) < thresholdSize.width) {
result = result | RCTTextSizeComparisonWithinRange;
}

return result;
}

- (void)scaleFontSizeWithRatio:(CGFloat)ratio
minimumFontSize:(CGFloat)minimumFontSize
maximumFontSize:(CGFloat)maximumFontSize
{
[self beginEditing];

[self enumerateAttribute:NSFontAttributeName
inRange:(NSRange){0, self.length}
options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired
usingBlock:^(UIFont *_Nullable font, NSRange range, BOOL *_Nonnull stop) {
if (!font) {
return;
}

CGFloat fontSize = MAX(MIN(font.pointSize * ratio, maximumFontSize), minimumFontSize);

[self addAttribute:NSFontAttributeName value:[font fontWithSize:fontSize] range:range];
}];

[self endEditing];
}

@end