Eviscerate mbgl expression to Foundation JSON object conversion (#11389)

* [ios, macos] Eviscerate mbgl expression to Foundation JSON object conversion

* [ios, macos] Remove literal special case

MGLJSONObjectFromMBGLValue() is just a literal translation from C++ types to Foundation types; no need for expression-specific literal wrapping.

* [ios, macos] Implemented RGB(A) operators

* [ios, macos] More robust color conversion

* [macos] Create calibrated RGB from expression on Sierra

* [macos] Calibrate colors in expressions at runtime

* [ios, macos] Special-case number conversion without fallbacks

* [ios, macos] Test mgl_number expressions

* [ios, macos] Updated tests for aftermarket expressions

* [ios, macos] Relax roundtripping requirement for serialize()

* [ios, macos] Fixed interpolation expression tests

* [ios, macos] Removed dead code

* [ios, macos] Fixed color conversion on Sierra

2 files changed, 56 insertions, 0 deletions

diff --git a/platform/ios/src/UIColor+MGLAdditions.h b/platform/ios/src/UIColor+MGLAdditions.h
index ea415d9db9..60cfe1c58b 100644
--- a/platform/ios/src/UIColor+MGLAdditions.h
+++ b/platform/ios/src/UIColor+MGLAdditions.h
@@ -12,3 +12,10 @@
 + (UIColor *)mgl_colorWithColor:(mbgl::Color)color;
 
 @end
+
+@interface NSExpression (MGLColorAdditions)
+
++ (NSExpression *)mgl_expressionForRGBComponents:(NSArray<NSExpression *> *)components;
++ (NSExpression *)mgl_expressionForRGBAComponents:(NSArray<NSExpression *> *)components;
+
+@end
diff --git a/platform/ios/src/UIColor+MGLAdditions.mm b/platform/ios/src/UIColor+MGLAdditions.mm
index 41c066c206..9ca39acda4 100644
--- a/platform/ios/src/UIColor+MGLAdditions.mm
+++ b/platform/ios/src/UIColor+MGLAdditions.mm
@@ -21,3 +21,52 @@
 }
 
 @end
+
+@implementation NSExpression (MGLColorAdditions)
+
++ (NSExpression *)mgl_expressionForRGBComponents:(NSArray<NSExpression *> *)components {
+    if (UIColor *color = [self mgl_colorWithRGBComponents:components]) {
+        return [NSExpression expressionForConstantValue:color];
+    }
+    
+    NSExpression *color = [NSExpression expressionForConstantValue:[UIColor class]];
+    NSExpression *alpha = [NSExpression expressionForConstantValue:@1.0];
+    return [NSExpression expressionForFunction:color
+                                  selectorName:@"colorWithRed:green:blue:alpha:"
+                                     arguments:[components arrayByAddingObject:alpha]];
+}
+
++ (NSExpression *)mgl_expressionForRGBAComponents:(NSArray<NSExpression *> *)components {
+    if (UIColor *color = [self mgl_colorWithRGBComponents:components]) {
+        return [NSExpression expressionForConstantValue:color];
+    }
+    
+    NSExpression *color = [NSExpression expressionForConstantValue:[UIColor class]];
+    return [NSExpression expressionForFunction:color
+                                  selectorName:@"colorWithRed:green:blue:alpha:"
+                                     arguments:components];
+}
+
++ (UIColor *)mgl_colorWithRGBComponents:(NSArray<NSExpression *> *)components {
+    if (components.count < 3 || components.count > 4) {
+        return nil;
+    }
+    
+    for (NSExpression *component in components) {
+        if (component.expressionType != NSConstantValueExpressionType) {
+            return nil;
+        }
+        
+        NSNumber *number = (NSNumber *)component.constantValue;
+        if (![number isKindOfClass:[NSNumber class]]) {
+            return nil;
+        }
+    }
+    
+    return [UIColor colorWithRed:[components[0].constantValue doubleValue] / 255.0
+                           green:[components[1].constantValue doubleValue] / 255.0
+                            blue:[components[2].constantValue doubleValue] / 255.0
+                           alpha:components.count == 3 ? [components[3].constantValue doubleValue] : 1.0];
+}
+
+@end