#include "private.h"

#include "world.h"

#include "drawing.h"

static double colorBack[4] = {1, 1, 1, 1};

static double *path;

static size_t pathSize;

static size_t pathAllocated;

static HeliDrawingState statesStack[1024] = {{

	{0, 0, 0, 1},       // colorStroke

	{0.5, 0.5, 0.5, 1}, // colorFill

	1,                  // lineWidth

	HALIGN_LEFT,        // horAlign

	VALIGN_TOP,         // vertAlign

	NULL,               // font

	24                  // fontSize

}};

static int statesStackIndex = 0;

typedef struct _HeliStrokePoint {

	double x, y, dx, dy;

} HeliStrokePoint;

typedef struct _HeliStroke {

	HeliStrokePoint *points;

	int count;

	int allocatedCount;

} HeliStroke;

static void endPath(int close, int stroke, int fill, int fillSimple);

static void closePathSimple()

	{ endPath(TRUE, TRUE, FALSE, TRUE); }

void background(const char *color)

	{ heliParseColor(color, colorBack); }

void fill(const char *color)

	{ heliParseColor(color, heliDrawingGetState()->colorFill); }

void noFill()

	{ fill("transparent"); }

void stroke(const char *color)

	{ heliParseColor(color, heliDrawingGetState()->colorStroke); }

void noStroke()

	{ stroke("transparent"); }

void strokeWeight(double weight)

	{ heliDrawingGetState()->lineWidth = weight; }

const char* rgba(double r, double g, double b, double a) {

	static char buf[1024];

	snprintf(buf, sizeof(buf) - 1, "%f %f %f %f", r, g, b, a);

	return buf;

}

const char* rgb(double r, double g, double b)

	{ return rgba(r, g, b, 1); }

void rect(double x, double y, double width, double height) {

	resetPath();

	moveTo(x, y);

	lineTo(x + width, y);

	lineTo(x + width, y + height);

	lineTo(x, y + height);

	closePathSimple();

}

void line(double x1, double y1, double x2, double y2) {

	resetPath();

	moveTo(x1, y1);

	lineTo(x2, y2);

	strokePath();

}

void ellipse(double x, double y, double width, double height) {

	resetPath();

	arcPath(x, y, width, height, 0, 360);

	closePathSimple();

}

void point(double x, double y) {

	pushDrawingState();

	HeliDrawingState *s = heliDrawingGetState();

	memcpy(s->colorFill, s->colorStroke, sizeof(s->colorFill));

	s->colorStroke[3] = 0;

	ellipse(x - s->lineWidth*0.5, y - s->lineWidth*0.5, s->lineWidth, s->lineWidth);

	popDrawingState();

}

void arcPath(double x, double y, double w, double h, double start, double stop) {

	w *= 0.5; x += w;

	h *= 0.5; y += h;

	if (fabs(w) < HELI_PRECISION || fabs(h) < HELI_PRECISION) return;

	double step = fabs(w) > fabs(h) ? 1/fabs(w) : 1/fabs(h);

	if (step > PI/180) step = PI/180;

	start *= PI/180;

	stop *= PI/180;

	double a = start;

	if (start < stop) {

		while(1) {

			if (a > stop) a = stop;

			lineTo(x + cos(a)*w, y + sin(a)*h);

			if (a == stop) break;

			a += step;

		}

	} else {

		while(1) {

			if (a < stop) a = stop;

			lineTo(x + cos(a)*w, y + sin(a)*h);

			if (a == stop) break;

			a -= step;

		}

	}

}

void arc(double x, double y, double w, double h, double start, double stop) {

	resetPath();

	arcPath(x, y, w, h, start, stop);

	strokePath();

}

void regularPolygon(double x, double y, int sides, double size) {

	resetPath();

	size *= 0.5;

	moveTo(x + size, y);

	for(int i = 1; i < sides; ++i) {

		double a = i*2*PI/sides;

		lineTo(x + size*cos(a), y + size*sin(a));

	}

	closePathSimple();

}

void resetPath()

	{ pathSize = 0; }

static void drawFillSimple() {

	HeliDrawingState *s = heliDrawingGetState();

	if (s->colorFill[3] <= HELI_PRECISION) return;

	if (pathSize < 6) return;

	glColor4dv(s->colorFill);

	glEnable(GL_MULTISAMPLE);

	glBegin(GL_TRIANGLE_FAN);

	for(int i = 0; i < pathSize; i += 2)

		glVertex2dv(&path[i]);

	glEnd();

	glDisable(GL_MULTISAMPLE);

	glColor4d(1, 1, 1, 1);

}

static void drawFill() {

	HeliDrawingState *s = heliDrawingGetState();

	if (s->colorFill[3] <= HELI_PRECISION) return;

	if (pathSize < 6) return;

	double l = path[0], r = l;

	double t = path[1], b = t;

	for(int i = 2; i < pathSize; i += 2) {

		if (l > path[i]) l = path[i];

		if (r < path[i]) r = path[i];

		if (t > path[i + 1]) t = path[i + 1];

		if (b < path[i + 1]) b = path[i + 1];

	}

	if ( r - l <= HELI_PRECISION

	  || b - t <= HELI_PRECISION) return;

	l -= 1; r += 1;

	t -= 1; b += 1;

	glEnable(GL_MULTISAMPLE);

	glColor4dv(s->colorFill);

	glEnable(GL_STENCIL_TEST);

	glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);

	glStencilOp(GL_ZERO, GL_ZERO, GL_ZERO);

	glBegin(GL_QUADS);

	glVertex2d(l, t);

	glVertex2d(r, t);

	glVertex2d(r, b);

	glVertex2d(l, b);

	glEnd();

	glStencilOpSeparate(GL_FRONT, GL_INCR_WRAP, GL_INCR_WRAP, GL_INCR_WRAP);

	glStencilOpSeparate(GL_BACK, GL_DECR_WRAP, GL_DECR_WRAP, GL_DECR_WRAP);

	glBegin(GL_TRIANGLE_FAN);

	for(int i = 0; i < pathSize; i += 2)

		glVertex2dv(&path[i]);

	glEnd();

	glStencilFunc(GL_NOTEQUAL, 0, -1u);

	glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

	glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);

	glBegin(GL_QUADS);

	glVertex2d(l, t);

	glVertex2d(r, t);

	glVertex2d(r, b);

	glVertex2d(l, b);

	glEnd();

	glStencilFunc(GL_ALWAYS, 0, -1u);

	glDisable(GL_STENCIL_TEST);

	glDisable(GL_MULTISAMPLE);

	glColor4d(1, 1, 1, 1);

}

static void strokeAddPoint(HeliStroke *stroke, double x, double y, double dx, double dy) {

	if (stroke->allocatedCount < stroke->count + 1) {

		stroke->allocatedCount += stroke->allocatedCount/4 + 32;

		stroke->points = realloc(stroke->points, stroke->allocatedCount*4*sizeof(*stroke->points));

		memset(stroke->points + stroke->count, 0, (stroke->allocatedCount - stroke->count)*sizeof(*stroke->points));

	}

	HeliStrokePoint *p = &stroke->points[ stroke->count++ ];

	p->x = x;

	p->y = y;

	p->dx = dx;

	p->dy = dy;

}

static void strokeAddCornerSub(HeliStroke *stroke, double dx, double dy, double precisionSqr, int level) {

	assert(stroke->count > 0);

	HeliStrokePoint *prev = stroke->points + stroke->count - 1;

	if (level > 0) {

		double distx = dx - prev->dx;

		double disty = dy - prev->dy;

		if (distx*distx + disty*disty > precisionSqr) {

			double mx = prev->dx + dx;

			double my = prev->dy + dy;

			double lsqr = mx*mx + my*my;

			if (lsqr > HELI_PRECISION_SQR) {

				double kl = 1/sqrt(lsqr);

				mx *= kl;

				my *= kl;

				strokeAddCornerSub(stroke, mx, my, precisionSqr, level-1);

				strokeAddCornerSub(stroke, dx, dy, precisionSqr, level-1);

				return;

			}

		}

	}

	strokeAddPoint(stroke, prev->x, prev->y, dx, dy);

}

static void strokeAddCorner(

	HeliStroke *stroke,

	double xp, double yp,

	double x0, double y0,

	double x1, double y1,

	double precisionSqr )

{

	double dx0 = x0 - xp;

	double dy0 = y0 - yp;

	double dx1 = x1 - x0;

	double dy1 = y1 - y0;

	double l0 = sqrt(dx0*dx0 + dy0*dy0);

	double l1 = sqrt(dx1*dx1 + dy1*dy1);

	assert(l0 > HELI_PRECISION);

	assert(l1 > HELI_PRECISION);

	double kl0 = 1/l0, kl1 = 1/l1;

	double nx0 = dx0*kl0, ny0 = dy0*kl0;

	double nx1 = dx1*kl1, ny1 = dy1*kl1;

	double dot = nx0*ny1 - ny0*nx1;

	if (dot > HELI_PRECISION) {

		// round

		strokeAddPoint(stroke, x0, y0, ny0, -nx0);

		strokeAddCornerSub(stroke, ny1, -nx1, precisionSqr, 8);

	} else

	if (dot < HELI_PRECISION) {

		// corner

		double dx = nx1 - nx0;

		double dy = ny1 - ny0;

		double kl = 1/sqrt(dx*dx + dy*dy);

		double nx = dx*kl, ny = dy*kl;

		double c = nx*nx1 + ny*ny1;

		double cl = 1/sqrt(1 - c*c);

		if (cl > 3) cl = 3;

		strokeAddPoint(stroke, x0, y0, nx*cl, ny*cl);

	} else {

		// flat

		strokeAddPoint(stroke, x0, y0, ny0, -nx0);

	}

}

static void strokeDraw(HeliStroke *stroke, double w, double *color) {

	const double aaBorder = 1;

	if (aaBorder > 0) {

		double c0[4] = { color[0], color[1], color[2], 0 };

		double c1[4] = { color[0], color[1], color[2], color[3] };

		double w0 = w + 0.5*aaBorder;

		double w1 = w - 0.5*aaBorder;

		if (w1 < HELI_PRECISION) {

			c1[3] *= w0/aaBorder;

			w1 = 0;

		}

		glBegin(GL_TRIANGLE_STRIP);

		for(int i = 0; i < stroke->count; ++i) {

			HeliStrokePoint *p = stroke->points + i;

			glColor4dv(c0);

			glVertex2d(p->x + p->dx*w0, p->y + p->dy*w0);

			glColor4dv(c1);

			glVertex2d(p->x + p->dx*w1, p->y + p->dy*w1);

		}

		glEnd();

		if (w1 > 0) {

			glColor4dv(c1);

			glBegin(GL_TRIANGLE_STRIP);

			for(int i = 0; i < stroke->count; ++i) {

				HeliStrokePoint *p = stroke->points + i;

				glVertex2d(p->x, p->y);

				glVertex2d(p->x + p->dx*w1, p->y + p->dy*w1);

			}

			glEnd();

		}

		glColor4d(1, 1, 1, 1);

	} else {

		glColor4dv(color);

		glEnable(GL_MULTISAMPLE);

		glBegin(GL_TRIANGLE_STRIP);

		for(int i = 0; i < stroke->count; ++i) {

			HeliStrokePoint *p = stroke->points + i;

			glVertex2d(p->x, p->y);

			glVertex2d(p->x + p->dx*w, p->y + p->dy*w);

		}

		glEnd();

		glDisable(GL_MULTISAMPLE);

		glColor4d(1, 1, 1, 1);

	}

}

static void drawStroke(int close) {

	HeliDrawingState *s = heliDrawingGetState();

	if (s->colorStroke[3] <= HELI_PRECISION) return;

	if (s->lineWidth < HELI_PRECISION) return;

	if (pathSize < 4) return;

	HeliStroke stroke = {};

	stroke.allocatedCount = pathSize;

	stroke.points = calloc(stroke.allocatedCount, sizeof(*stroke.points));

	double w = 0.5*s->lineWidth;

	double precisionSqr = 1/(w*0.75);

	precisionSqr *= precisionSqr;

	if (close) {

		for(int i = 0; i < pathSize; i += 2) {

			int p = i > 0 ? i - 2 : pathSize - 2;

			int n = i < pathSize - 2 ? i + 2 : 0;

			strokeAddCorner(

				&stroke,

				path[p], path[p+1],

				path[i], path[i+1],

				path[n], path[n+1],

				precisionSqr );

		}

		strokeAddPoint(

			&stroke,

			stroke.points[0].x,

			stroke.points[0].y,

			stroke.points[0].dx,

			stroke.points[0].dy );

		strokeDraw(&stroke, w, s->colorStroke);

		stroke.count = 0;

		for(int i = pathSize - 2; i >= 0; i -= 2) {

			int p = i < pathSize - 2 ? i + 2 : 0;

			int n = i > 0 ? i - 2 : pathSize - 2;

			strokeAddCorner(

				&stroke,

				path[p], path[p+1],

				path[i], path[i+1],

				path[n], path[n+1],

				precisionSqr );

		}

		strokeAddPoint(

			&stroke,

			stroke.points[0].x,

			stroke.points[0].y,

			stroke.points[0].dx,

			stroke.points[0].dy );

		strokeDraw(&stroke, w, s->colorStroke);

	} else {

		double px = 0, py = 0, nx = 0, ny = 0;

		for(int i = 0; i < pathSize; i += 2) {

			double x = path[i], y = path[i+1];

			if (i > 0)            { px = path[i-2]; py = path[i-1]; }

			if (i < pathSize - 2) { nx = path[i+2]; ny = path[i+3]; }

			if (i == 0)            { px = x + y - ny; py = y + nx - x; }

			if (i == pathSize - 2) { nx = x + py - y; ny = y + x - px; }

			strokeAddCorner(&stroke, px, py, x, y, nx, ny, precisionSqr);

		}

		--stroke.count;

		for(int i = pathSize - 2; i >= 0; i -= 2) {

			double x = path[i], y = path[i+1];

			if (i > 0)            { nx = path[i-2]; ny = path[i-1]; }

			if (i < pathSize - 2) { px = path[i+2]; py = path[i+3]; }

			if (i == 0)            { nx = x + py - y; ny = y + x - px; }

			if (i == pathSize - 2) { px = x + y - ny; py = y + nx - x; }

			strokeAddCorner(&stroke, px, py, x, y, nx, ny, precisionSqr);

		}

		memcpy(stroke.points + stroke.count - 1, stroke.points, sizeof(*stroke.points));

		strokeDraw(&stroke, w, s->colorStroke);

	}

	free(stroke.points);

}

static void pushPathPoint(double x, double y) {

	if (pathAllocated < pathSize + 2) {

		pathAllocated += pathAllocated/4 + 32;

		path = realloc(path, pathAllocated*sizeof(*path));

		memset(&path[pathSize], 0, (pathAllocated - pathSize)*sizeof(*path));

	}

	path[pathSize++] = x;

	path[pathSize++] = y;

}

static void endPath(int close, int stroke, int fill, int fillSimple) {

	// remove duplicates

	int removed = 0;

	for(int i = 2; i < pathSize; i += 2) {

		if ( fabs(path[i-removed-2] - path[i]) <= 2*HELI_PRECISION

		  && fabs(path[i-removed-1] - path[i+1]) <= 2*HELI_PRECISION )

		{

			removed += 2;

		} else

		if (removed > 0) {

			path[i-removed] = path[i];

			path[i-removed+1] = path[i+1];

		}

	}

	// remove tails duplicates

	pathSize -= removed;

	if ( pathSize >= 4

	  && close

	  && fabs(path[pathSize-2] - path[0]) <= 2*HELI_PRECISION

	  && fabs(path[pathSize-1] - path[1]) <= 2*HELI_PRECISION )

		pathSize -= 2;

	// draw

	if (pathSize >= 4) {

		if (fillSimple) drawFillSimple();

			else if (fill) drawFill();

		if (stroke) drawStroke(close);

	}

	resetPath();

}

void closePath()

	{ endPath(TRUE, TRUE, TRUE, FALSE); }

void strokePath()

	{ endPath(FALSE, TRUE, FALSE, FALSE); }

void lineTo(double x, double y)

	{ pushPathPoint(x, y); }

void moveTo(double x, double y)

	{ resetPath(); lineTo(x, y); }

HeliDrawingState *heliDrawingGetState()

	{ return statesStack + statesStackIndex; }

HeliDrawingState *heliDrawingGetStateStack()

	{ return statesStack; }

void pushDrawingState() {

	if (statesStackIndex >= sizeof(statesStack)/sizeof(*statesStack) - 1) {

		fprintf(stderr, "helianthus: drawing stack overflow\n");

		return;

	}

	++statesStackIndex;

	memcpy(statesStack + statesStackIndex, statesStack + statesStackIndex - 1, sizeof(*statesStack));

}

void popDrawingState() {

	assert(statesStackIndex > 0);

	if (statesStackIndex <= 0) {

		fprintf(stderr, "helianthus: drawing stack underflow\n");

		return;

	}

	--statesStackIndex;

}

void heliDrawingClearFrame() {

	glClearColor(colorBack[0], colorBack[1], colorBack[2], colorBack[3]);

	glClear(GL_COLOR_BUFFER_BIT);

}

void heliDrawingPrepareFrame() {

	resetPath();

	if (statesStackIndex > 0) {

		//fprintf(stderr, "helianthus: drawing stack was not empty at end of frame\n");

		while(statesStackIndex > 0) popDrawingState();

	}

	heliDrawingClearFrame();

	glDisable(GL_DEPTH_TEST);

	glDisable(GL_STENCIL_TEST);

	glDisable(GL_CULL_FACE);

	glDisable(GL_MULTISAMPLE);

	glEnable(GL_BLEND);

	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glEnable(GL_LINE_SMOOTH);

	glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);

}

void heliDrawingFinish() {

	resetPath();

	free(path);

	path = NULL;

	pathAllocated = 0;

}