[ios, macos] Add format expression support.

3 files changed, 80 insertions, 18 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.h b/platform/darwin/src/NSExpression+MGLAdditions.h
index 1e6fd6fc46..c7a5f5a969 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLAdditions.h
@@ -7,6 +7,8 @@
 
 #import "MGLTypes.h"
 
+@class MGLAttributedExpression;
+
 NS_ASSUME_NONNULL_BEGIN
 
 typedef NSString *MGLExpressionInterpolationMode NS_TYPED_ENUM;
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 6aaba4dd90..b53fe63d55 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -11,6 +11,7 @@
 #import "NSPredicate+MGLAdditions.h"
 #import "NSValue+MGLStyleAttributeAdditions.h"
 #import "MGLVectorTileSource_Private.h"
+#import "MGLAttributedExpression.h"
 
 #import <objc/runtime.h>
 
@@ -75,6 +76,7 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     INSTALL_METHOD(mgl_atan:);
     INSTALL_METHOD(mgl_tan:);
     INSTALL_METHOD(mgl_log2:);
+    INSTALL_METHOD(mgl_attributed:);
     
     // Install functions that resemble control structures, taking arbitrary
     // numbers of arguments. Vararg aftermarket functions need to be declared
@@ -96,6 +98,12 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     return [components componentsJoinedByString:@""];
 }
 
+- (NSString *)mgl_attributed:(NSArray<MGLAttributedExpression *> *)attributedExpressions {
+    [NSException raise:NSInvalidArgumentException
+                format:@"Text format expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 /**
  Rounds the given number to the nearest integer. If the number is halfway
  between two integers, this method rounds it away from zero.
@@ -229,7 +237,6 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     return nil;
 }
 
-
 /**
  A placeholder for a catch-all method that evaluates an arbitrary number of
  arguments as an expression according to the Mapbox Style Specification’s
@@ -860,6 +867,23 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
         
             return [NSExpression expressionForFunction:@"MGL_MATCH"
                                              arguments:optionsArray];
+        } else if ([op isEqualToString:@"format"]) {
+            NSMutableArray *attributedExpressions = [NSMutableArray array];
+            
+            for (NSUInteger index = 0; index < argumentObjects.count; index+=2) {
+                NSExpression *expression = [NSExpression expressionWithMGLJSONObject:argumentObjects[index]];
+                NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
+                if ((index + 1) < argumentObjects.count) {
+                    attrs = argumentObjects[index + 1];
+                }
+                
+                MGLAttributedExpression *attributedExpression = [[MGLAttributedExpression alloc] initWithExpression:expression attributes:attrs];
+
+                [attributedExpressions addObject:attributedExpression];
+            }
+            NSExpression *subexpression = [NSExpression expressionForConstantValue:attributedExpressions];
+            return [NSExpression expressionForFunction:@"mgl_attributed:" arguments:@[subexpression]];
+            
         } else if ([op isEqualToString:@"coalesce"]) {
             NSMutableArray *expressions = [NSMutableArray array];
             for (id operand in argumentObjects) {
@@ -1115,6 +1139,11 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }
                 [NSException raise:NSInvalidArgumentException
                             format:@"Casting expression to %@ not yet implemented.", type];
+            } else if ([function isEqualToString:@"mgl_attributed:"] ||
+                       [function isEqualToString:@"MGL_FORMAT:"] ||
+                       [function isEqualToString:@"MGL_FORMAT"]) {
+                return [self mgl_jsonFormatExpressionObject];
+                
             } else if ([function isEqualToString:@"MGL_FUNCTION"] ||
                        [function isEqualToString:@"MGL_FUNCTION:"]) {
                 NSExpression *firstOp = self.arguments.firstObject;
@@ -1363,6 +1392,32 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     return expressionObject;
 }
 
+- (id)mgl_jsonFormatExpressionObject {
+    BOOL isAftermarketFunction = [self.function hasPrefix:@"mgl_attributed:"];
+    NSExpression *formatParameter;
+    NSArray<MGLAttributedExpression *> *attributedExpressions;
+    
+    if (isAftermarketFunction) {
+        formatParameter = self.arguments.firstObject;
+    } else {
+        formatParameter = self.operand;
+    }
+    
+    if ([formatParameter respondsToSelector:@selector(constantValue)] && [formatParameter.constantValue isKindOfClass:[NSArray class]]) {
+        attributedExpressions = (NSArray *)formatParameter.constantValue;
+    }
+    
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"format", nil];
+    
+    for (NSUInteger index = 0; index < attributedExpressions.count; index++) {
+        MGLAttributedExpression *attributedExpression = attributedExpressions[index];
+        [expressionObject addObject:attributedExpression.expression.mgl_jsonExpressionObject];
+        [expressionObject addObject:attributedExpression.attributes];
+    }
+    
+    return expressionObject;
+}
+
 #pragma mark Localization
 
 /**
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index bcc30e49fd..1152ed3c13 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -12,6 +12,7 @@
 #else
 #import "NSColor+MGLAdditions.h"
 #endif
+#import "MGLAttributedExpression.h"
 
 #define MGLAssertEqualValues(actual, expected, ...) \
     XCTAssertTrue(actual.is<__typeof__(expected)>()); \
@@ -990,6 +991,27 @@ using namespace std::string_literals;
     }
 }
 
+- (void)testFormatExpressionObject {
+    {
+        MGLAttributedExpression *attribute1 = [MGLAttributedExpression initWithExpression:[NSExpression expressionForConstantValue:@"foo"]
+                                                                                fontNames:nil
+                                                                                 fontSize:@(1.2)];
+        MGLAttributedExpression *attribute2 = [MGLAttributedExpression initWithExpression:[NSExpression expressionForConstantValue:@"biz"]
+                                                                                fontNames:nil
+                                                                                 fontSize:@(1.0)];
+        MGLAttributedExpression *attribute3 = [MGLAttributedExpression initWithExpression:[NSExpression expressionForConstantValue:@"bar"]
+                                                                                fontNames:nil
+                                                                                 fontSize:@(0.8)];
+        MGLAttributedExpression *attribute4 = [MGLAttributedExpression initWithExpression:[NSExpression expressionForConstantValue:@"\r"]
+                                                                                fontNames:@[]
+                                                                                 fontSize:nil];
+        NSExpression *expression = [NSExpression expressionWithFormat:@"mgl_attributed(%@)", @[attribute1, attribute4, attribute2, attribute3]];
+        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\r", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
+}
+
 - (void)testGenericExpressionObject {
     {
         NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('random', 1, 2, 3, 4, 5)"];
@@ -1002,23 +1024,6 @@ using namespace std::string_literals;
         XCTAssertThrowsSpecificNamed([expression expressionValueWithObject:nil context:nil], NSException, NSInvalidArgumentException);
     }
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_FUNCTION('format', 'foo', %@, '\r', %@, 'biz', %@, 'bar', %@)", @{@"font-scale": @1.2}, @{}, @{@"font-scale": @1.0}, @{@"font-scale": @0.8}];
-        NSArray *jsonExpression = @[@"format", @"foo", @{@"font-scale": @1.2}, @"\r", @{}, @"biz", @{@"font-scale": @1.0}, @"bar", @{@"font-scale": @0.8}];
-
-        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
-        
-        NSExpression *encodedExpression = [NSExpression expressionWithMGLJSONObject:jsonExpression];
-
-        // Expressions encoded from a json create a different constant abstract type
-        // thus even tho knowing that the constant values are the same, the base
-        // class is not. This compares the resulting array which is type agnostic encoding.
-        for (NSUInteger index = 0; index < jsonExpression.count; index++) {
-            NSExpression *left = encodedExpression.mgl_jsonExpressionObject[index];
-            NSExpression *right = expression.mgl_jsonExpressionObject[index];
-            XCTAssertEqualObjects(left.mgl_jsonExpressionObject, right.mgl_jsonExpressionObject);
-        }
-    }
-    {
         NSArray *arguments = @[
             MGLConstantExpression(@"one"), MGLConstantExpression(@1),
             [NSExpression expressionForVariable:@"one"],