/*
	This file is part of Warzone 2100.
	Copyright (C) 1999-2004  Eidos Interactive
	Copyright (C) 2005-2019  Warzone 2100 Project

	Warzone 2100 is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	Warzone 2100 is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with Warzone 2100; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* Geometry.c - holds trig/vector deliverance specific stuff for 3D */
/* Alex McLean, Pumpkin Studios, EIDOS Interactive */

#include "lib/framework/frame.h"

#include "lib/ivis_opengl/ivisdef.h"
#include "lib/ivis_opengl/piematrix.h"
#include "lib/ivis_opengl/pieclip.h"

#include "geometry.h"
#include "objectdef.h"
#include "map.h"
#include "display.h"

uint16_t calcDirection(int32_t x0, int32_t y0, int32_t x1, int32_t y1)
{
	return iAtan2(x1 - x0, y1 - y0);
}


/*	A useful function and one that should have been written long ago, assuming of course
	that is hasn't been!!!! Alex M, 24th Sept, 1998. Returns the nearest unit
	to a given world coordinate - we can choose whether we require that the unit be
	selected or not... Makes sending the most logical unit to do something very easy.

  NB*****THIS WON'T PICK A VTOL DROID*****
*/

DROID	*getNearestDroid(UDWORD x, UDWORD y, bool bSelected)
{
	DROID *psBestUnit = nullptr;
	unsigned bestSoFar = UDWORD_MAX;

	/* Go thru' all the droids  - how often have we seen this - a MACRO maybe? */
	for (DROID *psDroid = apsDroidLists[selectedPlayer]; psDroid; psDroid = psDroid->psNext)
	{
		if (!isVtolDroid(psDroid))
		{
			/* Clever (?) bit that reads whether we're interested in droids being selected or not */
			if (!bSelected || psDroid->selected)
			{
				uint32_t dist = iHypot(psDroid->pos.x - x, psDroid->pos.y - y);
				/* Is this the nearest one we got so far? */
				if (dist < bestSoFar)
				{
					/* Yes, then keep a record of the distance for comparison... */
					bestSoFar = dist;
					/* ..and store away the droid responsible */
					psBestUnit = psDroid;
				}
			}
		}
	}
	return psBestUnit;
}
// -------------------------------------------------------------------------------------------

/* Returns non-zero if a point is in a 4 sided polygon */
/* See header file for definition of QUAD */
bool inQuad(const Vector2i *pt, const QUAD *quad)
{
	// Early out.
	int minX = std::min(std::min(quad->coords[0].x, quad->coords[1].x), std::min(quad->coords[2].x, quad->coords[3].x)); if (pt->x < minX)
	{
		return false;
	}
	int maxX = std::max(std::max(quad->coords[0].x, quad->coords[1].x), std::max(quad->coords[2].x, quad->coords[3].x)); if (pt->x > maxX)
	{
		return false;
	}
	int minY = std::min(std::min(quad->coords[0].y, quad->coords[1].y), std::min(quad->coords[2].y, quad->coords[3].y)); if (pt->y < minY)
	{
		return false;
	}
	int maxY = std::max(std::max(quad->coords[0].y, quad->coords[1].y), std::max(quad->coords[2].y, quad->coords[3].y)); if (pt->y > maxY)
	{
		return false;
	}

	bool c = false;

	for (int i = 0, j = 3; i < 4; j = i++)
	{
		Vector2i edge = quad->coords[j] - quad->coords[i];
		Vector2i pos = *pt - quad->coords[i];
		if ((0 <= pos.y && pos.y < edge.y && (int64_t)pos.x * (int64_t)edge.y < (int64_t)pos.y * (int64_t)edge.x) ||
		    (edge.y <= pos.y && pos.y < 0 && (int64_t)pos.x * (int64_t)edge.y > (int64_t)pos.y * (int64_t)edge.x))
		{
			c = !c;
		}
	}

	return c;
}

Vector2i positionInQuad(Vector2i const &pt, QUAD const &quad)
{
	long lenSq[4];
	long ptDot[4];
	for (int i = 0, j = 3; i < 4; j = i++)
	{
		Vector2i edge = quad.coords[j] - quad.coords[i];
		Vector2i pos  = quad.coords[j] - pt;
		Vector2i posRot(pos.y, -pos.x);
		lenSq[i] = dot(edge, edge);
		ptDot[i] = dot(posRot, edge);
	}
	int ret[2];
	for (int i = 0; i < 2; ++i)
	{
		long d1 = ptDot[i] * lenSq[i + 2];
		long d2 = ptDot[i + 2] * lenSq[i];
		ret[i] = d1 + d2 != 0 ? (int64_t)TILE_UNITS * d1 / (d1 + d2) : TILE_UNITS / 2;
	}
	return Vector2i(ret[0], ret[1]);
}

//-----------------------------------------------------------------------------------
bool	droidOnScreen(DROID *psDroid, SDWORD tolerance)
{
	if (DrawnInLastFrame(psDroid->sDisplay.frameNumber) == true)
	{
		const int dX = psDroid->sDisplay.screenX;
		const int dY = psDroid->sDisplay.screenY;
		/* Is it on screen */
		if (dX > (0 - tolerance) && dY > (0 - tolerance)
		    && dX < (SDWORD)(pie_GetVideoBufferWidth() + tolerance)
		    && dY < (SDWORD)(pie_GetVideoBufferHeight() + tolerance))
		{
			return true;
		}
	}
	return false;
}
