#import <Foundation/Foundation.h>

#if TARGET_OS_OSX
#import <Cocoa/Cocoa.h>
#else
#import <UIKit/UIKit.h>
#endif

#import <Metal/Metal.h>
#import <MetalKit/MetalKit.h>

#include "imgui.h"
#include "imgui_impl_metal.h"

#if TARGET_OS_OSX
#include "imgui_impl_osx.h"

@interface ViewController : NSViewController
@end
#else
@interface ViewController : UIViewController
@end
#endif

@interface ViewController () <MTKViewDelegate>
@property (nonatomic, readonly) MTKView *mtkView;
@property (nonatomic, strong) id <MTLDevice> device;
@property (nonatomic, strong) id <MTLCommandQueue> commandQueue;
@end

@implementation ViewController

- (instancetype)initWithNibName:(nullable NSString *)nibNameOrNil bundle:(nullable NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    
    _device = MTLCreateSystemDefaultDevice();
    _commandQueue = [_device newCommandQueue];

    if (!self.device) {
        NSLog(@"Metal is not supported");
        abort();
    }
    
    // Setup Dear ImGui context
    // FIXME: This example doesn't have proper cleanup...
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsClassic();

    // Setup Renderer backend
    ImGui_ImplMetal_Init(_device);

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
    // - Read 'docs/FONTS.txt' for more instructions and details.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/ProggyTiny.ttf", 10.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != NULL);
    
    return self;
}

- (MTKView *)mtkView {
    return (MTKView *)self.view;
}

- (void)loadView {
    self.view = [[MTKView alloc] initWithFrame:CGRectMake(0, 0, 1200, 720)];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.mtkView.device = self.device;
    self.mtkView.delegate = self;
    
#if TARGET_OS_OSX
    // Add a tracking area in order to receive mouse events whenever the mouse is within the bounds of our view
    NSTrackingArea *trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
                                                                options:NSTrackingMouseMoved | NSTrackingInVisibleRect | NSTrackingActiveAlways
                                                                  owner:self
                                                               userInfo:nil];
    [self.view addTrackingArea:trackingArea];

    // If we want to receive key events, we either need to be in the responder chain of the key view,
    // or else we can install a local monitor. The consequence of this heavy-handed approach is that
    // we receive events for all controls, not just Dear ImGui widgets. If we had native controls in our
    // window, we'd want to be much more careful than just ingesting the complete event stream, though we
    // do make an effort to be good citizens by passing along events when Dear ImGui doesn't want to capture.
    NSEventMask eventMask = NSEventMaskKeyDown | NSEventMaskKeyUp | NSEventMaskFlagsChanged | NSEventTypeScrollWheel;
    [NSEvent addLocalMonitorForEventsMatchingMask:eventMask handler:^NSEvent * _Nullable(NSEvent *event) {
        BOOL wantsCapture = ImGui_ImplOSX_HandleEvent(event, self.view);
        if (event.type == NSEventTypeKeyDown && wantsCapture) {
            return nil;
        } else {
            return event;
        }

    }];

    ImGui_ImplOSX_Init();
    
#endif
}

#pragma mark - Interaction

#if TARGET_OS_OSX

- (void)mouseMoved:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)mouseDown:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)rightMouseDown:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)otherMouseDown:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)mouseUp:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)rightMouseUp:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)otherMouseUp:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)mouseDragged:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)rightMouseDragged:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)otherMouseDragged:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

- (void)scrollWheel:(NSEvent *)event {
    ImGui_ImplOSX_HandleEvent(event, self.view);
}

#else

// This touch mapping is super cheesy/hacky. We treat any touch on the screen
// as if it were a depressed left mouse button, and we don't bother handling
// multitouch correctly at all. This causes the "cursor" to behave very erratically
// when there are multiple active touches. But for demo purposes, single-touch
// interaction actually works surprisingly well.
- (void)updateIOWithTouchEvent:(UIEvent *)event {
    UITouch *anyTouch = event.allTouches.anyObject;
    CGPoint touchLocation = [anyTouch locationInView:self.view];
    ImGuiIO &io = ImGui::GetIO();
    io.MousePos = ImVec2(touchLocation.x, touchLocation.y);

    BOOL hasActiveTouch = NO;
    for (UITouch *touch in event.allTouches) {
        if (touch.phase != UITouchPhaseEnded && touch.phase != UITouchPhaseCancelled) {
            hasActiveTouch = YES;
            break;
        }
    }
    io.MouseDown[0] = hasActiveTouch;
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self updateIOWithTouchEvent:event];
}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self updateIOWithTouchEvent:event];
}

- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self updateIOWithTouchEvent:event];
}

- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self updateIOWithTouchEvent:event];
}

#endif

#pragma mark - MTKViewDelegate

- (void)drawInMTKView:(MTKView*)view
{
    ImGuiIO &io = ImGui::GetIO();
    io.DisplaySize.x = view.bounds.size.width;
    io.DisplaySize.y = view.bounds.size.height;

#if TARGET_OS_OSX
    CGFloat framebufferScale = view.window.screen.backingScaleFactor ?: NSScreen.mainScreen.backingScaleFactor;
#else
    CGFloat framebufferScale = view.window.screen.scale ?: UIScreen.mainScreen.scale;
#endif
    io.DisplayFramebufferScale = ImVec2(framebufferScale, framebufferScale);

    io.DeltaTime = 1 / float(view.preferredFramesPerSecond ?: 60);

    id<MTLCommandBuffer> commandBuffer = [self.commandQueue commandBuffer];

    // Our state (make them static = more or less global) as a convenience to keep the example terse.
    static bool show_demo_window = true;
    static bool show_another_window = false;
    static float clear_color[4] = { 0.28f, 0.36f, 0.5f, 1.0f };

    MTLRenderPassDescriptor* renderPassDescriptor = view.currentRenderPassDescriptor;
    if (renderPassDescriptor != nil)
    {
        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(clear_color[0], clear_color[1], clear_color[2], clear_color[3]);

        // Here, you could do additional rendering work, including other passes as necessary.

        id <MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
        [renderEncoder pushDebugGroup:@"ImGui demo"];

        // Start the Dear ImGui frame
        ImGui_ImplMetal_NewFrame(renderPassDescriptor);
#if TARGET_OS_OSX
        ImGui_ImplOSX_NewFrame(view);
#endif
        ImGui::NewFrame();

        // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
        {
            static float f = 0.0f;
            static int counter = 0;

            ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

            ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
            ImGui::Checkbox("Another Window", &show_another_window);

            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

            if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                counter++;
            ImGui::SameLine();
            ImGui::Text("counter = %d", counter);

            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
            ImGui::End();
        }

        // 3. Show another simple window.
        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }

        // Rendering
        ImGui::Render();
        ImDrawData* drawData = ImGui::GetDrawData();
        ImGui_ImplMetal_RenderDrawData(drawData, commandBuffer, renderEncoder);

        [renderEncoder popDebugGroup];
        [renderEncoder endEncoding];

        [commandBuffer presentDrawable:view.currentDrawable];
    }

    [commandBuffer commit];
}

- (void)mtkView:(MTKView*)view drawableSizeWillChange:(CGSize)size
{
}

@end

#pragma mark - Application Delegate

#if TARGET_OS_OSX

@interface AppDelegate : NSObject <NSApplicationDelegate>
@property (nonatomic, strong) NSWindow *window;
@end

@implementation AppDelegate

- (instancetype)init {
    if (self = [super init]) {
        NSViewController *rootViewController = [[ViewController alloc] initWithNibName:nil bundle:nil];
        self.window = [[NSWindow alloc] initWithContentRect:NSZeroRect
                                                  styleMask:NSWindowStyleMaskTitled | NSWindowStyleMaskClosable | NSWindowStyleMaskResizable | NSWindowStyleMaskMiniaturizable
                                                    backing:NSBackingStoreBuffered
                                                      defer:NO];
        self.window.contentViewController = rootViewController;
        [self.window orderFront:self];
        [self.window center];
        [self.window becomeKeyWindow];
    }
    return self;
}

- (BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication *)sender {
    return YES;
}

@end

#else

@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application
    didFinishLaunchingWithOptions:(NSDictionary<UIApplicationLaunchOptionsKey,id> *)launchOptions
{
    UIViewController *rootViewController = [[ViewController alloc] init];
    self.window = [[UIWindow alloc] initWithFrame:UIScreen.mainScreen.bounds];
    self.window.rootViewController = rootViewController;
    [self.window makeKeyAndVisible];
    return YES;
}

@end

#endif

#pragma mark - main()

#if TARGET_OS_OSX

int main(int argc, const char * argv[]) {
    return NSApplicationMain(argc, argv);
}

#else

int main(int argc, char * argv[]) {
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

#endif