[ios, macos] Add conventional custom function support.

4 files changed, 106 insertions, 27 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 2ff0d100f6..2af636516e 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -67,7 +67,7 @@
     // with an explicit and implicit first argument.
     INSTALL_CONTROL_STRUCTURE(MGL_LET);
     INSTALL_CONTROL_STRUCTURE(MGL_MATCH);
-    INSTALL_CONTROL_STRUCTURE(MGL_SWITCH);
+    INSTALL_CONTROL_STRUCTURE(MGL_IF);
     INSTALL_CONTROL_STRUCTURE(MGL_FUNCTION);
     
     #undef INSTALL_AFTERMARKET_FN
@@ -100,6 +100,9 @@
     return nil;
 }
 
+/**
+ A placeholder for a method that evaluates a coalesce expression.
+ */
 - (id)mgl_coalesce:(NSArray<NSExpression *> *)elements {
     [NSException raise:NSInvalidArgumentException
                 format:@"Coalesce expressions lack underlying Objective-C implementations."];
@@ -128,7 +131,7 @@
 /**
  A placeholder for a method that evaluates an expression and returns the matching element.
  */
-- (id)MGL_SWITCH:(id)firstCondition, ... {
+- (id)MGL_IF:(id)firstCondition, ... {
     va_list argumentList;
     va_start(argumentList, firstCondition);
     
@@ -647,7 +650,7 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }
             }
             
-            return [NSExpression expressionForFunction:@"MGL_SWITCH" arguments:arguments];
+            return [NSExpression expressionForFunction:@"MGL_IF" arguments:arguments];
         } else if ([op isEqualToString:@"match"]) {
             NSMutableArray *optionsArray = [NSMutableArray array];
             NSEnumerator *optionsEnumerator = argumentObjects.objectEnumerator;
@@ -852,28 +855,12 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
                 }];
                 [expressionObject addObject:self.operand.mgl_jsonExpressionObject];
                 return expressionObject;
-            } else if ([function isEqualToString:@"MGL_SWITCH"]) {
-                NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"case", nil];
-
-                for (NSExpression *option in self.arguments) {
-                    if ([option respondsToSelector:@selector(constantValue)] && [option.constantValue isKindOfClass:[NSComparisonPredicate class]]) {
-                        NSPredicate *predicate = (NSPredicate *)option.constantValue;
-                        [expressionObject addObject:predicate.mgl_jsonExpressionObject];
-                    } else {
-                        [expressionObject addObject:option.mgl_jsonExpressionObject];
-                    }
-                }
-
-                return expressionObject;
-            } else if ([function isEqualToString:@"MGL_MATCH"]) {
-                NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"match", nil];
-                
-
-                for (NSExpression *option in self.arguments) {
-                    [expressionObject addObject:option.mgl_jsonExpressionObject];
-                }
-                
-                return expressionObject;
+            } else if ([function isEqualToString:@"MGL_IF"] ||
+                       [function isEqualToString:@"mgl_if:"]) {
+                return self.mgl_jsonIfExpressionObject;
+            } else if ([function isEqualToString:@"MGL_MATCH"] ||
+                       [function isEqualToString:@"mgl_match:"]) {
+                return self.mgl_jsonMatchExpressionObject;
             } else if ([function isEqualToString:@"mgl_coalesce:"]) {
                 NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"coalesce", nil];
                 
@@ -1018,4 +1005,52 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     return expressionObject;
 }
 
+- (id)mgl_jsonMatchExpressionObject {
+    BOOL isAftermarketFunction = [self.function isEqualToString:@"MGL_MATCH"];
+    NSUInteger minimumIndex = isAftermarketFunction ? 1 : 0;
+
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"match", (isAftermarketFunction ? self.arguments.firstObject : self.operand).mgl_jsonExpressionObject, nil];
+    NSArray<NSExpression *> *arguments = isAftermarketFunction ? self.arguments : self.arguments[minimumIndex].constantValue;
+    
+    for (NSUInteger index = minimumIndex; index < arguments.count; index++) {
+        [expressionObject addObject:arguments[index].mgl_jsonExpressionObject];
+    }
+    
+    return expressionObject;
+}
+
+- (id)mgl_jsonIfExpressionObject {
+    BOOL isAftermarketFunction = [self.function isEqualToString:@"MGL_IF"];
+    NSUInteger minimumIndex = isAftermarketFunction ? 1 : 0;
+    NSExpression *firstCondition;
+    id condition;
+    
+    if (isAftermarketFunction) {
+        firstCondition = self.arguments.firstObject;
+    } else {
+        firstCondition = self.operand;
+    }
+    
+    if ([firstCondition respondsToSelector:@selector(constantValue)] && [firstCondition.constantValue isKindOfClass:[NSComparisonPredicate class]]) {
+        NSPredicate *predicate = (NSPredicate *)firstCondition.constantValue;
+        condition = predicate.mgl_jsonExpressionObject;
+    } else {
+        condition = firstCondition.mgl_jsonExpressionObject;
+    }
+    
+    NSMutableArray *expressionObject = [NSMutableArray arrayWithObjects:@"case", condition, nil];
+    NSArray<NSExpression *> *arguments = isAftermarketFunction ? self.arguments : self.arguments[minimumIndex].constantValue;
+    
+    for (NSUInteger index = minimumIndex; index < arguments.count; index++) {
+        if ([arguments[index] respondsToSelector:@selector(constantValue)] && [arguments[index].constantValue isKindOfClass:[NSComparisonPredicate class]]) {
+            NSPredicate *predicate = (NSPredicate *)arguments[index].constantValue;
+            [expressionObject addObject:predicate.mgl_jsonExpressionObject];
+        } else {
+            [expressionObject addObject:arguments[index].mgl_jsonExpressionObject];
+        }
+    }
+    
+    return expressionObject;
+}
+
 @end
diff --git a/platform/darwin/src/NSPredicate+MGLAdditions.h b/platform/darwin/src/NSPredicate+MGLAdditions.h
index 89e9e65c64..a73b1a61ba 100644
--- a/platform/darwin/src/NSPredicate+MGLAdditions.h
+++ b/platform/darwin/src/NSPredicate+MGLAdditions.h
@@ -16,4 +16,8 @@
 
 @property (nonatomic, readonly) id mgl_jsonExpressionObject;
 
+- (id)mgl_if:(id)firstValue, ...;
+
+- (id)mgl_match:(NSExpression *)firstCase, ...;
+
 @end
diff --git a/platform/darwin/src/NSPredicate+MGLAdditions.mm b/platform/darwin/src/NSPredicate+MGLAdditions.mm
index 63c8307803..8fe5735bf9 100644
--- a/platform/darwin/src/NSPredicate+MGLAdditions.mm
+++ b/platform/darwin/src/NSPredicate+MGLAdditions.mm
@@ -324,4 +324,35 @@ NSArray *MGLSubpredicatesWithJSONObjects(NSArray *objects) {
     return nil;
 }
 
+- (id)mgl_if:(id)firstValue, ... {
+
+    if ([self evaluateWithObject:nil]) {
+            return firstValue;
+        }
+
+    id eachExpression;
+    va_list argumentList;
+    va_start(argumentList, firstValue);
+
+    while ((eachExpression = va_arg(argumentList, id))) {
+            if ([eachExpression isKindOfClass:[NSComparisonPredicate class]]) {
+                    id valueExpression = va_arg(argumentList, id);
+                    if ([eachExpression evaluateWithObject:nil]) {
+                            return valueExpression;
+                        }
+                } else {
+                        return eachExpression;
+                    }
+        }
+    va_end(argumentList);
+
+    return nil;
+}
+
+- (id)mgl_match:(NSExpression *)firstCase, ... {
+    [NSException raise:NSInvalidArgumentException
+                      format:@"Match expressions lack underlying Objective-C implementations."];
+    return nil;
+}
+
 @end
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index f00ea690f5..17c48af226 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -632,8 +632,15 @@ using namespace std::string_literals;
                                     MGLConstantExpression(@"one"),
                                     MGLConstantExpression(@0),
                                     MGLConstantExpression(@"zero")];
+        NSExpression *predicate = [NSExpression expressionWithFormat:@"2 - 1"];
+        NSExpression *compatibilityExpression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_match:', %@)", predicate, @[MGLConstantExpression(@1),
+                                                 MGLConstantExpression(@"one"),
+                                                 MGLConstantExpression(@0),
+                                                 MGLConstantExpression(@"zero"),
+                                                 MGLConstantExpression(@"default")]];
         NSArray *jsonExpression =  @[@"match", @[@"-", @2, @1], @1, @"one", @0, @"zero", @"default"];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects(compatibilityExpression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
     }
     {
@@ -660,17 +667,19 @@ using namespace std::string_literals;
 
 - (void)testConditionalExpressionObject {
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_SWITCH(%@, %@, %@)",
+        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_IF(%@, %@, %@)",
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 2"]],
                                     MGLConstantExpression(@YES),
                                     MGLConstantExpression(@NO)];
+        NSExpression *compatibilityExpression = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'mgl_if:', %@)", [NSPredicate predicateWithFormat:@"1 = 2"], @[MGLConstantExpression(@YES), MGLConstantExpression(@NO)]];
         NSArray *jsonExpression = @[@"case", @[@"==", @1, @2], @YES, @NO];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects(compatibilityExpression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:nil], @NO);
     }
     {
-        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_SWITCH(%@, %@, %@, %@, %@)",
+        NSExpression *expression = [NSExpression expressionWithFormat:@"MGL_IF(%@, %@, %@, %@, %@)",
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 2"]],
                                     MGLConstantExpression(@YES),
                                     [NSExpression expressionWithFormat:@"%@", [NSPredicate predicateWithFormat:@"1 = 1"]],