[ios, macos] Add NSExpression convinient expression constructors.

4 files changed, 221 insertions, 9 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.h b/platform/darwin/src/NSExpression+MGLAdditions.h
index b4d36bc1b1..df8129811d 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.h
+++ b/platform/darwin/src/NSExpression+MGLAdditions.h
@@ -9,6 +9,54 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+typedef NSString *MGLExpressionStyleFunction NS_STRING_ENUM;
+typedef NSString *MGLExpressionInterpolationMode NS_STRING_ENUM;
+
+/**
+ An `NSString` identifying the `zoomLevel` operator in an `NSExpression`.
+ 
+ This attribute corresponds to the
+ <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-zoom"><code>zoom</code></a>
+ expression reference in the Mapbox Style Specification.
+ */
+extern MGL_EXPORT const MGLExpressionStyleFunction MGLExpressionStyleFunctionZoomLevel;
+
+/**
+ An `NSString` identifying the `heatmapDensity` operator in an `NSExpression`.
+ 
+ This attribute corresponds to the
+ <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-heatmap-density"><code>heatmap-density</code></a>
+ expression reference in the Mapbox Style Specification.
+ */
+extern MGL_EXPORT const MGLExpressionStyleFunction MGLExpressionStyleFunctionHeatmapDensity;
+
+/**
+ An `NSString` identifying the `linear` interpolation type in an `NSExpression`.
+ 
+ This attribute corresponds to the `linear` value in the
+ <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-interpolate"><code>interpolate</code></a>
+ expression reference in the Mapbox Style Specification.
+ */
+extern MGL_EXPORT const MGLExpressionInterpolationMode MGLExpressionInterpolationModeLinear;
+
+/**
+ An `NSString` identifying the `expotential` interpolation type in an `NSExpression`.
+ 
+ This attribute corresponds to the `exponential` value in the
+ <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-interpolate"><code>interpolate</code></a>
+ expression reference in the Mapbox Style Specification.
+ */
+extern MGL_EXPORT const MGLExpressionInterpolationMode MGLExpressionInterpolationModeExponential;
+
+/**
+ An `NSString` identifying the `cubic-bezier` interpolation type in an `NSExpression`.
+ 
+ This attribute corresponds to the `cubic-bezier` value in the
+ <a href="https://www.mapbox.com/mapbox-gl-js/style-spec/#expressions-interpolate"><code>interpolate</code></a>
+ expression reference in the Mapbox Style Specification.
+ */
+extern MGL_EXPORT const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier;
+
 @interface NSExpression (MGLAdditions)
 
 /**
@@ -42,6 +90,105 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (nonatomic, readonly) id mgl_jsonExpressionObject;
 
+/**
+ Returns a constant expression containing an `NSString`.
+ 
+ This is equivalent to call `[NSExpression expressionForConstant:]`.
+ 
+ @param string The string constant.
+ */
++ (instancetype)mgl_expressionForString:(nonnull NSString *)string;
+
+/**
+ Returns a constant expression containing an `MGLColor`.
+ 
+ This is equivalent to call `[NSExpression expressionForConstant:]`.
+ 
+ @param color The color constant.
+ */
++ (instancetype)mgl_expressionForColor:(nonnull MGLColor *)color;
+
+/**
+ Returns a constant expression containing an `NSValue`.
+ 
+ This is equivalent to call `[NSExpression expressionForConstant:]`.
+ 
+ @param value The value constant.
+ */
++ (instancetype)mgl_expressionForValue:(nonnull NSValue *)value;
+
++ (instancetype)mgl_expressionForTernaryFunction:(nonnull NSString *)conditionString trueExpression:(nonnull NSExpression *)trueExpression falseExpresssion:(nonnull NSExpression *)falseExpression;
+
+/**
+ Returns a step function expression specifying the function operator, default value
+ and stops.
+ 
+ @param function The operator type in which this expression is applied.
+ @param value The default value can be boolean or numeric.
+ @param stops The stops dictionay must be numeric literals in strictly ascending order.
+ */
++ (instancetype)mgl_expressionForStepFunction:(nonnull MGLExpressionStyleFunction)function defaultValue:(nonnull NSValue *)value stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops;
+
+/**
+ Returns a step function expression specifying the function operator, default color
+ and stops.
+ 
+ @param function The operator type in which this expression is applied.
+ @param color The default color.
+ @param stops The stops dictionay must be numeric literals in strictly ascending order.
+ */
++ (instancetype)mgl_expressionForStepFunction:(nonnull MGLExpressionStyleFunction)function defaultColor:(nonnull MGLColor *)color stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops;
+
+/**
+ Returns a step function expression specifying the function operator, default expression
+ and stops.
+ 
+ @param function The operator type in which this expression is applied.
+ @param expression The expression which could be a constant or function expression.
+ @param stops The stops dictionay must be numeric literals in strictly ascending order.
+ */
++ (instancetype)mgl_expressionForStepFunction:(nonnull MGLExpressionStyleFunction)function defaultExpression:(nonnull NSExpression *)expression stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops;
+
+/**
+ Returns an interpolated function expression specifying the function operator, curve type
+ and steps.
+ 
+ @param function The operator type in which this expression is applied.
+ @param curveType The curve type could be `MGLExpressionInterpolationModeLinear`,
+                    `MGLExpressionInterpolationModeExponential` and
+                    `MGLExpressionInterpolationModeCubicBezier`.
+ @param steps The stops dictionay must be numeric literals in strictly ascending order.
+ */
++ (instancetype)mgl_expressionForInterpolateFunction:(nonnull MGLExpressionStyleFunction)function curveType:(nonnull MGLExpressionInterpolationMode)curveType steps:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)steps;
+
+/**
+ Returns an interpolated function expression specifying the function operator, curve type,
+ parameters and steps.
+ 
+ @param function The operator type in which this expression is applied.
+ @param curveType The curve type could be `MGLExpressionInterpolationModeLinear`,
+ `MGLExpressionInterpolationModeExponential` and
+ `MGLExpressionInterpolationModeCubicBezier`.
+ @param parameters The parameters expression.
+ @param steps The stops dictionay must be numeric literals in strictly ascending order.
+ */
++ (instancetype)mgl_expressionForInterpolateFunction:(nonnull MGLExpressionStyleFunction)function curveType:(nonnull MGLExpressionInterpolationMode)curveType parameters:(nullable NSExpression *)parameters steps:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)steps;
+
+/**
+ Returns a string constant expression appending the passed string.
+ 
+ @param string The string to append.
+ */
+- (instancetype)mgl_appendingString:(NSString *)string;
+
+/**
+ Returns a string constant expression appending the passed expression.
+ 
+ @param expression The evaluated expression must return a string.
+ */
+- (instancetype)mgl_appendingExpression:(NSExpression *)expression;
+
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 5ad565c398..ed501d0e18 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -13,6 +13,13 @@
 
 #import <mbgl/style/expression/expression.hpp>
 
+const MGLExpressionStyleFunction MGLExpressionStyleFunctionZoomLevel = @"$zoomLevel";
+const MGLExpressionStyleFunction MGLExpressionStyleFunctionHeatmapDensity = @"$heatmapDensity";
+
+const MGLExpressionInterpolationMode MGLExpressionInterpolationModeLinear = @"linear";
+const MGLExpressionInterpolationMode MGLExpressionInterpolationModeExponential = @"exponential";
+const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier = @"cubic-bezier";
+
 @implementation NSExpression (MGLPrivateAdditions)
 
 - (std::vector<mbgl::Value>)mgl_aggregateMBGLValue {
@@ -297,6 +304,55 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     return subexpressions;
 }
 
++ (instancetype)mgl_expressionForString:(NSString *)string {
+    return [NSExpression expressionForConstantValue:string];
+}
+
++ (instancetype)mgl_expressionForColor:(MGLColor *)color {
+    return [NSExpression expressionForConstantValue:color];
+}
++ (instancetype)mgl_expressionForValue:(NSValue *)value {
+    return [NSExpression expressionForConstantValue:value];
+}
+
++ (instancetype)mgl_expressionForTernaryFunction:(NSString *)conditionString trueExpression:(NSExpression *)trueExpression falseExpresssion:(NSExpression *)falseExpression {
+    NSString *funtionFormat = [NSString stringWithFormat:@"TERNARY(%@, %%@, %%@)", conditionString];
+    return [NSExpression expressionWithFormat:funtionFormat, trueExpression, falseExpression];
+}
+
++ (instancetype)mgl_expressionForStepFunction:(MGLExpressionStyleFunction)function defaultValue:(NSValue *)value stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops {
+    return [NSExpression mgl_expressionForStepFunction:function
+                                     defaultExpression:[NSExpression mgl_expressionForValue:value]
+                                                 stops:stops];
+}
+
++ (instancetype)mgl_expressionForStepFunction:(MGLExpressionStyleFunction)function defaultString:(NSString *)string stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops {
+    return [NSExpression mgl_expressionForStepFunction:function
+                                     defaultExpression:[NSExpression mgl_expressionForString:string]
+                                                 stops:stops];
+}
+
++ (instancetype)mgl_expressionForStepFunction:(MGLExpressionStyleFunction)function defaultColor:(MGLColor *)color stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops {
+    return [NSExpression mgl_expressionForStepFunction:function
+                                     defaultExpression:[NSExpression mgl_expressionForColor:color]
+                                                 stops:stops];
+}
+
++ (instancetype)mgl_expressionForStepFunction:(MGLExpressionStyleFunction)function defaultExpression:(NSExpression *)expression stops:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)stops {
+    NSString *functionFormat = [NSString stringWithFormat:@"FUNCTION(%@, 'mgl_stepWithMinimum:stops:', %%@, %%@, %%@)", function];
+    return [NSExpression expressionWithFormat:functionFormat, expression, stops];
+}
+
++ (instancetype)mgl_expressionForInterpolateFunction:(MGLExpressionStyleFunction)function curveType:(nonnull MGLExpressionInterpolationMode)curveType steps:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)steps; {
+    return [NSExpression mgl_expressionForInterpolateFunction:function curveType:curveType parameters:nil steps:steps];
+}
+
++ (instancetype)mgl_expressionForInterpolateFunction:(MGLExpressionStyleFunction)function curveType:(nonnull MGLExpressionInterpolationMode)curveType parameters:(nullable NSExpression *)parameters steps:(nonnull NS_DICTIONARY_OF(NSNumber *, id) *)steps {
+    NSString *functionFormat = [NSString stringWithFormat:@"FUNCTION(%@, 'mgl_interpolateWithCurveType:parameters:stops:', %%@, %%@, %%@)", function];
+    return [NSExpression expressionWithFormat:functionFormat, curveType, parameters, steps];
+}
+
+
 + (instancetype)mgl_expressionWithJSONObject:(id)object {
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
@@ -487,6 +543,15 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
     return nil;
 }
 
+
+
+- (instancetype)mgl_appendingString:(NSString *)string {
+    return [self mgl_appendingExpression:[NSExpression mgl_expressionForString:string]];
+}
+- (instancetype)mgl_appendingExpression:(NSExpression *)expression {
+    return [NSExpression expressionForFunction:self selectorName:@"stringByAppendingString:" arguments:@[expression]];
+}
+
 - (id)mgl_jsonExpressionObject {
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
diff --git a/platform/ios/app/MBXViewController.m b/platform/ios/app/MBXViewController.m
index a472e3a221..18e8229c8f 100644
--- a/platform/ios/app/MBXViewController.m
+++ b/platform/ios/app/MBXViewController.m
@@ -945,14 +945,20 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
 - (void)styleWaterLayer
 {
     MGLFillStyleLayer *waterLayer = (MGLFillStyleLayer *)[self.mapView.style layerWithIdentifier:@"water"];
+    
     NSDictionary *waterColorStops = @{@6.0f: [UIColor yellowColor],
                                       @8.0f: [UIColor blueColor],
                                       @10.0f: [UIColor redColor],
                                       @12.0f: [UIColor greenColor],
                                       @14.0f: [UIColor blueColor]};
-    waterLayer.fillColor = [NSExpression expressionWithFormat:
-                            @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
-                            waterColorStops];
+    MGLNSExpressionBuilder *expressionBuilder = [MGLNSExpressionBuilder expressionBuilderWithFunction:MGLExpressionStyleFunctionZoomLevel
+                                                                                 interpolateCurveType:MGLInterpolateCurveTypeLinear
+                                                                                           parameters:nil
+                                                                                                steps:waterColorStops];
+//    waterLayer.fillColor = [NSExpression expressionWithFormat:
+//                            @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+//                            waterColorStops];
+    waterLayer.fillColor = expressionBuilder.expression;
 
     NSDictionary *fillAntialiasedStops = @{@11: @YES,
                                            @12: @NO,
diff --git a/platform/ios/ios.xcodeproj/project.pbxproj b/platform/ios/ios.xcodeproj/project.pbxproj
index b2d89fe962..29a5b74a70 100644
--- a/platform/ios/ios.xcodeproj/project.pbxproj
+++ b/platform/ios/ios.xcodeproj/project.pbxproj
@@ -511,8 +511,6 @@
 		DA8963381CC549A100684375 /* sprites in Resources */ = {isa = PBXBuildFile; fileRef = DA8963341CC549A100684375 /* sprites */; };
 		DA8963391CC549A100684375 /* styles in Resources */ = {isa = PBXBuildFile; fileRef = DA8963351CC549A100684375 /* styles */; };
 		DA89633A1CC549A100684375 /* tiles in Resources */ = {isa = PBXBuildFile; fileRef = DA8963361CC549A100684375 /* tiles */; };
-		DA9EA82B201C0C0C00F9874D /* NSExpression+MGLAdditions.h in Headers */ = {isa = PBXBuildFile; fileRef = DA9EA82A201C0C0B00F9874D /* NSExpression+MGLAdditions.h */; settings = {ATTRIBUTES = (Public, ); }; };
-		DA9EA82C201C0C0C00F9874D /* NSExpression+MGLAdditions.h in Headers */ = {isa = PBXBuildFile; fileRef = DA9EA82A201C0C0B00F9874D /* NSExpression+MGLAdditions.h */; };
 		DAA32CC31E4C6B65006F8D24 /* MGLDistanceFormatter.m in Sources */ = {isa = PBXBuildFile; fileRef = 3557F7AF1E1D27D300CCA5E6 /* MGLDistanceFormatter.m */; };
 		DAA4E4081CBB6C9500178DFB /* Mapbox.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = DA8847D21CBAF91600AB86E3 /* Mapbox.framework */; };
 		DAA4E4091CBB6C9500178DFB /* Mapbox.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = DA8847D21CBAF91600AB86E3 /* Mapbox.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
@@ -1164,7 +1162,6 @@
 		DA9C012C1E4C7ADB00C4742A /* pt-BR */ = {isa = PBXFileReference; lastKnownFileType = text.plist.stringsdict; name = "pt-BR"; path = "pt-BR.lproj/Foundation.stringsdict"; sourceTree = "<group>"; };
 		DA9C012D1E4C7B1F00C4742A /* pt-BR */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = "pt-BR"; path = "pt-BR.lproj/Localizable.strings"; sourceTree = "<group>"; };
 		DA9C012E1E4C7B6100C4742A /* pt-BR */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = "pt-BR"; path = "pt-BR.lproj/Root.strings"; sourceTree = "<group>"; };
-		DA9EA82A201C0C0B00F9874D /* NSExpression+MGLAdditions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSExpression+MGLAdditions.h"; sourceTree = "<group>"; };
 		DAA32CA11E4C44DB006F8D24 /* de */ = {isa = PBXFileReference; lastKnownFileType = text.plist.stringsdict; name = de; path = de.lproj/Foundation.stringsdict; sourceTree = "<group>"; };
 		DAA32CA21E4C44DD006F8D24 /* de */ = {isa = PBXFileReference; lastKnownFileType = text.plist.stringsdict; name = de; path = de.lproj/Localizable.stringsdict; sourceTree = "<group>"; };
 		DAA32CA31E4C44F1006F8D24 /* de */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = de; path = de.lproj/Foundation.strings; sourceTree = "<group>"; };
@@ -2073,7 +2070,6 @@
 				408AA8561DAEDA0800022900 /* NSDictionary+MGLAdditions.mm */,
 				DA8848141CBAFA6200AB86E3 /* NSException+MGLAdditions.h */,
 				3510FFEE1D6D9D8C00F413B2 /* NSExpression+MGLAdditions.h */,
-				DA9EA82A201C0C0B00F9874D /* NSExpression+MGLAdditions.h */,
 				DAC25FCB200FD83E009BE98E /* NSExpression+MGLPrivateAdditions.h */,
 				3510FFEF1D6D9D8C00F413B2 /* NSExpression+MGLAdditions.mm */,
 				35B82BF61D6C5F8400B1B721 /* NSPredicate+MGLAdditions.h */,
@@ -2264,7 +2260,6 @@
 				DA8848841CBB033F00AB86E3 /* FABAttributes.h in Headers */,
 				DA8847FD1CBAFA5100AB86E3 /* MGLTilePyramidOfflineRegion.h in Headers */,
 				DA88482F1CBAFA6200AB86E3 /* NSProcessInfo+MGLAdditions.h in Headers */,
-				DA9EA82B201C0C0C00F9874D /* NSExpression+MGLAdditions.h in Headers */,
 				DA8848601CBAFC2E00AB86E3 /* Mapbox.h in Headers */,
 				DAF0D8101DFE0EA000B28378 /* MGLRasterSource_Private.h in Headers */,
 				350098BB1D480108004B2AF0 /* MGLVectorSource.h in Headers */,
@@ -2294,7 +2289,6 @@
 				DABFB8641CBE99E500D62B32 /* MGLOfflineStorage.h in Headers */,
 				96E516E32000552A00A02306 /* MGLAccountManager_Private.h in Headers */,
 				96E5170420005A6B00A02306 /* SMCalloutView.h in Headers */,
-				DA9EA82C201C0C0C00F9874D /* NSExpression+MGLAdditions.h in Headers */,
 				96036A02200565C700510F3D /* NSOrthography+MGLAdditions.h in Headers */,
 				DAD165791CF4CDFF001FF4B9 /* MGLShapeCollection.h in Headers */,
 				4049C29E1DB6CD6C00B3F799 /* MGLPointCollection.h in Headers */,