//
//  CSOpenGLView
//  CLK
//
//  Created by Thomas Harte on 16/07/2015.
//  Copyright 2015 Thomas Harte. All rights reserved.
//

#import "CSOpenGLView.h"
#import "CSApplication.h"
@import CoreVideo;
@import GLKit;

@interface CSOpenGLView () <NSDraggingDestination, CSApplicationEventDelegate>
@end

@implementation CSOpenGLView {
	CVDisplayLinkRef _displayLink;
	CGSize _backingSize;

	NSTrackingArea *_mouseTrackingArea;
	NSTimer *_mouseHideTimer;
	BOOL _mouseIsCaptured;
}

- (void)prepareOpenGL {
	[super prepareOpenGL];

	// Synchronize buffer swaps with vertical refresh rate
	GLint swapInt = 1;
	[[self openGLContext] setValues:&swapInt forParameter:NSOpenGLCPSwapInterval];

	// Create a display link capable of being used with all active displays
	CVDisplayLinkCreateWithActiveCGDisplays(&_displayLink);

	// Set the renderer output callback function
	CVDisplayLinkSetOutputCallback(_displayLink, DisplayLinkCallback, (__bridge void * __nullable)(self));

	// Set the display link for the current renderer
	CGLContextObj cglContext = [[self openGLContext] CGLContextObj];
	CGLPixelFormatObj cglPixelFormat = [[self pixelFormat] CGLPixelFormatObj];
	CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(_displayLink, cglContext, cglPixelFormat);

	// set the clear colour
	[self.openGLContext makeCurrentContext];
	glClearColor(0.0, 0.0, 0.0, 1.0);

	// Activate the display link
	CVDisplayLinkStart(_displayLink);
}

static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp *now, const CVTimeStamp *outputTime, CVOptionFlags flagsIn, CVOptionFlags *flagsOut, void *displayLinkContext) {
	CSOpenGLView *const view = (__bridge CSOpenGLView *)displayLinkContext;
	[view drawAtTime:now frequency:CVDisplayLinkGetActualOutputVideoRefreshPeriod(displayLink)];
	return kCVReturnSuccess;
}

- (void)drawAtTime:(const CVTimeStamp *)now frequency:(double)frequency {
	[self redrawWithEvent:CSOpenGLViewRedrawEventTimer];
}

- (void)drawRect:(NSRect)dirtyRect {
	[self redrawWithEvent:CSOpenGLViewRedrawEventAppKit];
}

- (void)redrawWithEvent:(CSOpenGLViewRedrawEvent)event {
	[self performWithGLContext:^{
		[self.delegate openGLViewRedraw:self event:event];
		CGLFlushDrawable([[self openGLContext] CGLContextObj]);
	}];
}

- (void)invalidate {
	CVDisplayLinkStop(_displayLink);
}

- (void)dealloc {
	// Release the display link
	CVDisplayLinkRelease(_displayLink);
}

- (CGSize)backingSize {
	@synchronized(self) {
		return _backingSize;
	}
}

- (void)reshape {
	[super reshape];
	@synchronized(self) {
		_backingSize = [self convertSizeToBacking:self.bounds.size];
	}

	[self performWithGLContext:^{
		CGSize viewSize = [self backingSize];
		glViewport(0, 0, (GLsizei)viewSize.width, (GLsizei)viewSize.height);
	}];
}

- (void)awakeFromNib {
	NSOpenGLPixelFormatAttribute attributes[] = {
		NSOpenGLPFADoubleBuffer,
		NSOpenGLPFAOpenGLProfile,	NSOpenGLProfileVersion3_2Core,
//		NSOpenGLPFAMultisample,
//		NSOpenGLPFASampleBuffers,	1,
//		NSOpenGLPFASamples,			2,
		0
	};

	NSOpenGLPixelFormat *pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attributes];
	NSOpenGLContext *context = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];

#ifdef DEBUG
	// When we're using a CoreProfile context, crash if we call a legacy OpenGL function
	// This will make it much more obvious where and when such a function call is made so
	// that we can remove such calls.
	// Without this we'd simply get GL_INVALID_OPERATION error for calling legacy functions
	// but it would be more difficult to see where that function was called.
	CGLEnable([context CGLContextObj], kCGLCECrashOnRemovedFunctions);
#endif

	self.pixelFormat = pixelFormat;
	self.openGLContext = context;
	self.wantsBestResolutionOpenGLSurface = YES;

	// Register to receive dragged and dropped file URLs.
	[self registerForDraggedTypes:@[(__bridge NSString *)kUTTypeFileURL]];
}

- (void)performWithGLContext:(dispatch_block_t)action {
	CGLLockContext([[self openGLContext] CGLContextObj]);
	[self.openGLContext makeCurrentContext];
	action();
	CGLUnlockContext([[self openGLContext] CGLContextObj]);
}

#pragma mark - NSResponder

- (BOOL)acceptsFirstResponder {
	return YES;
}

- (void)keyDown:(NSEvent *)event {
	[self.responderDelegate keyDown:event];
}

- (void)keyUp:(NSEvent *)event {
	[self.responderDelegate keyUp:event];
}

- (void)flagsChanged:(NSEvent *)event {
	// Release the mouse upon a control + command.
	if(_mouseIsCaptured &&
		event.modifierFlags & NSEventModifierFlagControl &&
		event.modifierFlags & NSEventModifierFlagCommand) {
		[self releaseMouse];
	}

	[self.responderDelegate flagsChanged:event];
}

- (BOOL)application:(nonnull CSApplication *)application shouldSendEvent:(nonnull NSEvent *)event {
	switch(event.type) {
		default: return YES;
		case NSEventTypeKeyUp:			[self keyUp:event];		return NO;
		case NSEventTypeKeyDown:		[self keyDown:event];	return NO;
		case NSEventTypeFlagsChanged:	[self flagsChanged:event];	return NO;
	}
}

- (void)paste:(id)sender {
	[self.responderDelegate paste:sender];
}

#pragma mark - NSDraggingDestination

- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender {
	for(NSPasteboardItem *item in [[sender draggingPasteboard] pasteboardItems]) {
		NSURL *URL = [NSURL URLWithString:[item stringForType:(__bridge NSString *)kUTTypeFileURL]];
		[self.delegate openGLView:self didReceiveFileAtURL:URL];
	}
	return YES;
}

- (NSDragOperation)draggingEntered:(id < NSDraggingInfo >)sender {
	return NSDragOperationLink;
}

#pragma mark - Mouse hiding

- (void)setShouldCaptureMouse:(BOOL)shouldCaptureMouse {
	_shouldCaptureMouse = shouldCaptureMouse;
}

- (void)updateTrackingAreas {
	[super updateTrackingAreas];

	if(_mouseTrackingArea) {
		[self removeTrackingArea:_mouseTrackingArea];
	}
	_mouseTrackingArea =
		[[NSTrackingArea alloc]
			initWithRect:self.bounds
			options:NSTrackingMouseEnteredAndExited | NSTrackingMouseMoved | NSTrackingActiveWhenFirstResponder
			owner:self
			userInfo:nil];
	[self addTrackingArea:_mouseTrackingArea];
}

- (void)scheduleMouseHide {
	if(!self.shouldCaptureMouse) {
		[_mouseHideTimer invalidate];

		_mouseHideTimer = [NSTimer scheduledTimerWithTimeInterval:3.0 repeats:NO block:^(NSTimer * _Nonnull timer) {
			[NSCursor setHiddenUntilMouseMoves:YES];
		}];
	}
}

- (void)mouseEntered:(NSEvent *)event {
	[super mouseEntered:event];
	[self scheduleMouseHide];
}

- (void)mouseExited:(NSEvent *)event {
	[super mouseExited:event];
	[_mouseHideTimer invalidate];
	_mouseHideTimer = nil;
}

- (void)releaseMouse {
	if(_mouseIsCaptured) {
		_mouseIsCaptured = NO;
		CGAssociateMouseAndMouseCursorPosition(true);
		[NSCursor unhide];
		[self.delegate openGLViewDidReleaseMouse:self];
		((CSApplication *)[NSApplication sharedApplication]).eventDelegate = nil;
	}
}

#pragma mark - Mouse motion

- (void)applyMouseMotion:(NSEvent *)event {
	if(!self.shouldCaptureMouse) {
		// Mouse capture is off, so don't play games with the cursor, just schedule it to
		// hide in the near future.
		[self scheduleMouseHide];
	} else {
		if(_mouseIsCaptured) {
			// Mouse capture is on, so move the cursor back to the middle of the window, and
			// forward the deltas to the listener.
			//
			// TODO: should I really need to invert the y coordinate myself? It suggests I
			// might have an error in mapping here.
			const NSPoint windowCentre = [self convertPoint:CGPointMake(self.bounds.size.width * 0.5, self.bounds.size.height * 0.5) toView:nil];
			const NSPoint screenCentre = [self.window convertPointToScreen:windowCentre];
			const CGRect screenFrame = self.window.screen.frame;
			CGWarpMouseCursorPosition(NSMakePoint(
				screenFrame.origin.x + screenCentre.x,
				screenFrame.origin.y + screenFrame.size.height - screenCentre.y
			));

			[self.responderDelegate mouseMoved:event];
		}
	}
}

- (void)mouseDragged:(NSEvent *)event {
	[self applyMouseMotion:event];
	[super mouseDragged:event];
}

- (void)rightMouseDragged:(NSEvent *)event {
	[self applyMouseMotion:event];
	[super rightMouseDragged:event];
}

- (void)otherMouseDragged:(NSEvent *)event {
	[self applyMouseMotion:event];
	[super otherMouseDragged:event];
}

- (void)mouseMoved:(NSEvent *)event {
	[self applyMouseMotion:event];
	[super mouseMoved:event];
}

#pragma mark - Mouse buttons

- (void)applyButtonDown:(NSEvent *)event {
	if(self.shouldCaptureMouse) {
		if(!_mouseIsCaptured) {
			_mouseIsCaptured = YES;
			[NSCursor hide];
			CGAssociateMouseAndMouseCursorPosition(false);
			[self.delegate openGLViewDidCaptureMouse:self];
			if(self.shouldUsurpCommand) {
				((CSApplication *)[NSApplication sharedApplication]).eventDelegate = self;
			}

			// Don't report the first click to the delegate; treat that as merely
			// an invitation to capture the cursor.
			return;
		}

		[self.responderDelegate mouseDown:event];
	}
}

- (void)applyButtonUp:(NSEvent *)event {
	if(self.shouldCaptureMouse) {
		[self.responderDelegate mouseUp:event];
	}
}

- (void)mouseDown:(NSEvent *)event {
	[self applyButtonDown:event];
	[super mouseDown:event];
}

- (void)rightMouseDown:(NSEvent *)event {
	[self applyButtonDown:event];
	[super rightMouseDown:event];
}

- (void)otherMouseDown:(NSEvent *)event {
	[self applyButtonDown:event];
	[super otherMouseDown:event];
}

- (void)mouseUp:(NSEvent *)event {
	[self applyButtonUp:event];
	[super mouseUp:event];
}

- (void)rightMouseUp:(NSEvent *)event  {
	[self applyButtonUp:event];
	[super rightMouseUp:event];
}

- (void)otherMouseUp:(NSEvent *)event {
	[self applyButtonUp:event];
	[super otherMouseUp:event];
}

@end