#include <u.h>
#include <libc.h>
#include <draw.h>

#include "rushhour.h"

int
item(Point p)
{
	return level.board[p.x][p.y];
}

void
setitem(Point p, int v)
{
	level.board[p.x][p.y] = v;
}

int
isvehicle(int square)
{
	switch(square) {
	case CarX:
	case CarY:
	case CarZ:
	case CarA:
	case CarB:
	case CarC:
	case CarD:
	case CarE:
	case CarF:
	case CarG:
	case CarH:
	case CarI:
	case CarJ:
	case CarK:
	case CarL:
	case CarM:
	case CarN:
	case TruckO:
	case TruckP:
	case TruckQ:
	case TruckR:
	case TruckS:
	case TruckT:
	case TruckU:
	case TruckV:
		return 1;
	default:
		return 0;
	}
}

Point
next(Point p)
{
	int b, o;
	Point t;
	Point one[] = {
		[OHoriz] Pt(1, 0),
		[OVert]  Pt(0,1)
	};

	b = item(p);
	if (isvehicle(b)) {
		o = level.orient[b];
		t = addpt(p, one[o]);
		return t;
	} else {
		return p;
	}
}

Point
prev(Point p)
{
	int b, o;
	Point t;
	Point one[] = {
		[OHoriz] Pt(1, 0),
		[OVert]  Pt(0,1)
	};

	b = item(p);
	if (isvehicle(b)) {
		o = level.orient[b];
		t = subpt(p, one[o]);
		return t;
	} else {
		return p;
	}
}

Point
gettopleft(Point p)
{
	int b;
	Point s, t;

	b = item(p);
	if (isvehicle(b)) {
		s = p;
		t = prev(s);
		while (item(t) == b) {
			s = t;
			t = prev(s);
		}
		return s;
	} else {
		return p;
	}
}

int
canmove(Point p, Point dir)
{
	int b, res;
	Point d;

	if (eqpt(dir, ZP))
		return 0;

	res = 0;
	b = item(p);
	if (isvehicle(b)) {
		d = addpt(p, dir);
		/*
		 * check that we do not go beyond the allocated board
		 * (allocated: Rpt(ZP, Pt(MazeX, MazeY))
		 * (used: Rpt(ZP, level.max)
		 */
		while (ptinrect(d, Rect(0,0, MazeX, MazeY)) && item(d) == b) {
			d = addpt(d, dir);
		}
		if (ptinrect(d, Rect(0,0, MazeX, MazeY))) {
			switch(item(d)) {
			case Empty:
				res = 1;
				break;
			}
		}
	}
	return res;
}

Point
destof(Point p, Point dir)
{
	int b;
	Point d;

	if (eqpt(dir, ZP))
		return Pt(-1,-1);

	b = item(p);
	if (isvehicle(b)) {
		d = addpt(p, dir);
		while (item(d) == b) {
			d = addpt(d, dir);
		}
		switch(item(d)) {
		case Empty:
			return d;
			break;
		}
	}
	return Pt(-1,-1);
}

int
onestep(Point p, Point dir, Point *vacant)
{
	int b;
	Point e, d, t, v;

	if (eqpt(dir, ZP))
		return 0;

	b = item(p);
	if (isvehicle(b)) {
		v = p;
		t = subpt(v, dir);
		while (item(t) == b) {
			v = t;
			t = subpt(v, dir);
		}
		e = p;
		t = addpt(e, dir);
		while (item(t) == b) {
			e = t;
			t = addpt(e, dir);
		}
		d = t;
		switch(item(d)) {
		case Empty:
			*vacant = v;
			setitem(d, b);
			setitem(v, Empty);
			/* make escaping car disappear */
			if (ptinrect(v, Rpt(Pt(Off,Off), level.max)) &&
			     !ptinrect(addpt(v,dir), Rpt(Pt(Off,Off), level.max))) {
				t = gettopleft(d);
				while(item(t) == b) {
					p = t;
					t = next(t);
					setitem(p, Empty);
				}
			}
				
			return 1;
		}
	}
	return 0;
}