// Copyright (c) Athena Dev Teams - Licensed under GNU GPL
// For more information, see LICENCE in the main folder

#include "../common/cbasetypes.h"
#include "../common/nullpo.h"
#include "../common/random.h"
#include "../common/showmsg.h"
#include "../common/malloc.h"
#include "map.h"
#include "battle.h"
#include "path.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define MAX_HEAP 150

struct tmp_path { short x,y,dist,before,cost,flag;};
#define calc_index(x,y) (((x)+(y)*MAX_WALKPATH) & (MAX_WALKPATH*MAX_WALKPATH-1))

const char walk_choices [3][3] =
{
	{1,0,7},
	{2,-1,6},
	{3,4,5},
};

/*==========================================
 * heap push (helper function)
 *------------------------------------------*/
static void push_heap_path(int *heap,struct tmp_path *tp,int index)
{
	int i,h;

	h = heap[0];
	heap[0]++;

	for( i = (h-1)/2; h > 0 && tp[index].cost < tp[heap[i+1]].cost; i = (h-1)/2 )
		heap[h+1] = heap[i+1], h = i;

	heap[h+1] = index;
}

/*==========================================
 * heap update (helper function)
 * Move toward the root because cost has decreased.
 *------------------------------------------*/
static void update_heap_path(int *heap,struct tmp_path *tp,int index)
{
	int i,h;

	ARR_FIND( 0, heap[0], h, heap[h+1] == index );
	if( h == heap[0] )
	{
		ShowError("update_heap_path bug\n");
		exit(EXIT_FAILURE);
	}

	for( i = (h-1)/2; h > 0 && tp[index].cost < tp[heap[i+1]].cost; i = (h-1)/2 )
		heap[h+1] = heap[i+1], h = i;

	heap[h+1] = index;
}

/*==========================================
 * heap pop (helper function)
 *------------------------------------------*/
static int pop_heap_path(int *heap,struct tmp_path *tp)
{
	int i,h,k;
	int ret,last;

	if( heap[0] <= 0 )
		return -1;
	ret = heap[1];
	last = heap[heap[0]];
	heap[0]--;

	for( h = 0, k = 2; k < heap[0]; k = k*2+2 )
	{
		if( tp[heap[k+1]].cost > tp[heap[k]].cost )
			k--;
		heap[h+1] = heap[k+1], h = k;
	}

	if( k == heap[0] )
		heap[h+1] = heap[k], h = k-1;

	for( i = (h-1)/2; h > 0 && tp[heap[i+1]].cost > tp[last].cost; i = (h-1)/2 )
		heap[h+1] = heap[i+1], h = i;

	heap[h+1]=last;

	return ret;
}

/*==========================================
 * calculate cost for the specified position
 *------------------------------------------*/
static int calc_cost(struct tmp_path *p,int16 x1,int16 y1)
{
	int xd = abs(x1 - p->x);
	int yd = abs(y1 - p->y);
	return (xd + yd)*10 + p->dist;
}

/*==========================================
 * attach/adjust path if neccessary
 *------------------------------------------*/
static int add_path(int *heap,struct tmp_path *tp,int16 x,int16 y,int dist,int before,int cost)
{
	int i;

	i = calc_index(x,y);

	if( tp[i].x == x && tp[i].y == y )
	{
		if( tp[i].dist > dist )
		{
			tp[i].dist = dist;
			tp[i].before = before;
			tp[i].cost = cost;
			if( tp[i].flag )
				push_heap_path(heap,tp,i);
			else
				update_heap_path(heap,tp,i);
			tp[i].flag = 0;
		}
		return 0;
	}

	if( tp[i].x || tp[i].y )
		return 1;

	tp[i].x = x;
	tp[i].y = y;
	tp[i].dist = dist;
	tp[i].before = before;
	tp[i].cost = cost;
	tp[i].flag = 0;
	push_heap_path(heap,tp,i);

	return 0;
}

/*==========================================
 * Find the closest reachable cell, 'count' cells away from (x0,y0) in direction (dx,dy).
 * Income after the coordinates of the blow
 *------------------------------------------*/
int path_blownpos(int16 m,int16 x0,int16 y0,int16 dx,int16 dy,int count)
{
	struct map_data *md;

	if( !map[m].cell )
		return -1;
	md = &map[m];

	if( count>25 ){ //Cap to prevent too much processing...?
		ShowWarning("path_blownpos: count too many %d !\n",count);
		count=25;
	}
	if( dx > 1 || dx < -1 || dy > 1 || dy < -1 ){
		ShowError("path_blownpos: illegal dx=%d or dy=%d !\n",dx,dy);
		dx=(dx>0)?1:((dx<0)?-1:0);
		dy=(dy>0)?1:((dy<0)?-1:0);
	}

	while( count > 0 && (dx != 0 || dy != 0) )
	{
		if( !map_getcellp(md,x0+dx,y0+dy,CELL_CHKPASS) )
		{// attempt partial movement
			int fx = ( dx != 0 && map_getcellp(md,x0+dx,y0,CELL_CHKPASS) );
			int fy = ( dy != 0 && map_getcellp(md,x0,y0+dy,CELL_CHKPASS) );
			if( fx && fy )
			{
				if(rnd()&1)
					dx=0;
				else
					dy=0;
			}
			if( !fx )
				dx=0;
			if( !fy )
				dy=0;
		}

		x0 += dx;
		y0 += dy;
		count--;
	}

	return (x0<<16)|y0; //TODO: use 'struct point' here instead?
}

/*==========================================
 * is ranged attack from (x0,y0) to (x1,y1) possible?
 *------------------------------------------*/
bool path_search_long(struct shootpath_data *spd,int16 m,int16 x0,int16 y0,int16 x1,int16 y1,cell_chk cell)
{
	int dx, dy;
	int wx = 0, wy = 0;
	int weight;
	struct map_data *md;
	struct shootpath_data s_spd;

	if( spd == NULL )
		spd = &s_spd; // use dummy output variable

	if (!map[m].cell)
		return false;
	md = &map[m];

	dx = (x1 - x0);
	if (dx < 0) {
		swap(x0, x1);
		swap(y0, y1);
		dx = -dx;
	}
	dy = (y1 - y0);

	spd->rx = spd->ry = 0;
	spd->len = 1;
	spd->x[0] = x0;
	spd->y[0] = y0;

	if (map_getcellp(md,x1,y1,cell))
		return false;

	if (dx > abs(dy)) {
		weight = dx;
		spd->ry = 1;
	} else {
		weight = abs(y1 - y0);
		spd->rx = 1;
	}

	while (x0 != x1 || y0 != y1)
	{
		if (map_getcellp(md,x0,y0,cell))
			return false;
		wx += dx;
		wy += dy;
		if (wx >= weight) {
			wx -= weight;
			x0++;
		}
		if (wy >= weight) {
			wy -= weight;
			y0++;
		} else if (wy < 0) {
			wy += weight;
			y0--;
		}
		if( spd->len<MAX_WALKPATH )
		{
			spd->x[spd->len] = x0;
			spd->y[spd->len] = y0;
			spd->len++;
		}
	}

	return true;
}

/*==========================================
 * path search (x0,y0)->(x1,y1)
 * wpd: path info will be written here
 * flag: &1 = easy path search only
 * cell: type of obstruction to check for
 *------------------------------------------*/
bool path_search(struct walkpath_data *wpd,int16 m,int16 x0,int16 y0,int16 x1,int16 y1,int flag,cell_chk cell)
{
	int heap[MAX_HEAP+1];
	struct tmp_path tp[MAX_WALKPATH*MAX_WALKPATH];
	register int i,j,len,x,y,dx,dy;
	int rp,xs,ys;
	struct map_data *md;
	struct walkpath_data s_wpd;

	if( wpd == NULL )
		wpd = &s_wpd; // use dummy output variable

	if( !map[m].cell )
		return false;
	md = &map[m];

#ifdef CELL_NOSTACK
	//Do not check starting cell as that would get you stuck.
	if( x0 < 0 || x0 >= md->xs || y0 < 0 || y0 >= md->ys )
#else
	if( x0 < 0 || x0 >= md->xs || y0 < 0 || y0 >= md->ys /*|| map_getcellp(md,x0,y0,cell)*/ )
#endif
		return false;
	if( x1 < 0 || x1 >= md->xs || y1 < 0 || y1 >= md->ys || map_getcellp(md,x1,y1,cell) )
		return false;

	// calculate (sgn(x1-x0), sgn(y1-y0))
	dx = ((dx = x1-x0)) ? ((dx<0) ? -1 : 1) : 0;
	dy = ((dy = y1-y0)) ? ((dy<0) ? -1 : 1) : 0;

	// try finding direct path to target
	x = x0;
	y = y0;
	i = 0;
	while( i < ARRAYLENGTH(wpd->path) )
	{
		wpd->path[i] = walk_choices[-dy + 1][dx + 1];
		i++;

		x += dx;
		y += dy;

		if( x == x1 ) dx = 0;
		if( y == y1 ) dy = 0;

		if( dx == 0 && dy == 0 )
			break; // success
		if( map_getcellp(md,x,y,cell) )
			break; // obstacle = failure
	}

	if( x == x1 && y == y1 )
	{ //easy path successful.
		wpd->path_len = i;
		wpd->path_pos = 0;
		return true;
	}

	if( flag&1 )
		return false;

	memset(tp,0,sizeof(tp));

	i=calc_index(x0,y0);
	tp[i].x=x0;
	tp[i].y=y0;
	tp[i].dist=0;
	tp[i].before=0;
	tp[i].cost=calc_cost(&tp[i],x1,y1);
	tp[i].flag=0;
	heap[0]=0;
	push_heap_path(heap,tp,calc_index(x0,y0));
    xs = md->xs - 1; // Place by subtracting a pre-
	ys = md->ys-1;

	for(;;)
	{
		int e=0,f=0,dist,cost,dc[4]={0,0,0,0};

		if(heap[0]==0)
			return false;
		rp   = pop_heap_path(heap,tp);
		x    = tp[rp].x;
		y    = tp[rp].y;
		dist = tp[rp].dist + 10;
		cost = tp[rp].cost;

		if(x==x1 && y==y1)
			break;

		// dc[0] : y++ Incremental cost at the time
		// dc[1] : x--
		// dc[2] : y--
		// dc[3] : x++

		if(y < ys && !map_getcellp(md,x  ,y+1,cell)) {
			f |= 1; dc[0] = (y >= y1 ? 20 : 0);
			e+=add_path(heap,tp,x  ,y+1,dist,rp,cost+dc[0]); // (x,   y+1)
		}
		if(x > 0  && !map_getcellp(md,x-1,y  ,cell)) {
			f |= 2; dc[1] = (x <= x1 ? 20 : 0);
			e+=add_path(heap,tp,x-1,y  ,dist,rp,cost+dc[1]); // (x-1, y  )
		}
		if(y > 0  && !map_getcellp(md,x  ,y-1,cell)) {
			f |= 4; dc[2] = (y <= y1 ? 20 : 0);
			e+=add_path(heap,tp,x  ,y-1,dist,rp,cost+dc[2]); // (x  , y-1)
		}
		if(x < xs && !map_getcellp(md,x+1,y  ,cell)) {
			f |= 8; dc[3] = (x >= x1 ? 20 : 0);
			e+=add_path(heap,tp,x+1,y  ,dist,rp,cost+dc[3]); // (x+1, y  )
		}
		if( (f & (2+1)) == (2+1) && !map_getcellp(md,x-1,y+1,cell))
			e+=add_path(heap,tp,x-1,y+1,dist+4,rp,cost+dc[1]+dc[0]-6);		// (x-1, y+1)
		if( (f & (2+4)) == (2+4) && !map_getcellp(md,x-1,y-1,cell))
			e+=add_path(heap,tp,x-1,y-1,dist+4,rp,cost+dc[1]+dc[2]-6);		// (x-1, y-1)
		if( (f & (8+4)) == (8+4) && !map_getcellp(md,x+1,y-1,cell))
			e+=add_path(heap,tp,x+1,y-1,dist+4,rp,cost+dc[3]+dc[2]-6);		// (x+1, y-1)
		if( (f & (8+1)) == (8+1) && !map_getcellp(md,x+1,y+1,cell))
			e+=add_path(heap,tp,x+1,y+1,dist+4,rp,cost+dc[3]+dc[0]-6);		// (x+1, y+1)
		tp[rp].flag=1;
		if(e || heap[0]>=MAX_HEAP-5)
			return false;
	}

	if( !(x==x1 && y==y1) ) // will never happen...
		return false;

	for(len=0,i=rp;len<100 && i!=calc_index(x0,y0);i=tp[i].before,len++);
	if(len==100 || len>=sizeof(wpd->path))
		return false;

	wpd->path_len = len;
	wpd->path_pos = 0;
	for(i=rp,j=len-1;j>=0;i=tp[i].before,j--) {
		int dx  = tp[i].x - tp[tp[i].before].x;
		int dy  = tp[i].y - tp[tp[i].before].y;
		uint8 dir;
		if( dx == 0 ) {
			dir = (dy > 0 ? 0 : 4);
		} else if( dx > 0 ) {
			dir = (dy == 0 ? 6 : (dy < 0 ? 5 : 7) );
		} else {
			dir = (dy == 0 ? 2 : (dy > 0 ? 1 : 3) );
		}
		wpd->path[j] = dir;
	}

	return true;
}


//Distance functions, taken from http://www.flipcode.com/articles/article_fastdistance.shtml
int check_distance(int dx, int dy, int distance)
{
#ifdef CIRCULAR_AREA
	//In this case, we just do a square comparison. Add 1 tile grace for diagonal range checks.
	return (dx*dx + dy*dy <= distance*distance + (dx&&dy?1:0));
#else
	if (dx < 0) dx = -dx;
	if (dy < 0) dy = -dy;
	return ((dx<dy?dy:dx) <= distance);
#endif
}

unsigned int distance(int dx, int dy)
{
#ifdef CIRCULAR_AREA
	unsigned int min, max;

	if ( dx < 0 ) dx = -dx;
	if ( dy < 0 ) dy = -dy;
	//There appears to be something wrong with the aproximation below when either dx/dy is 0! [Skotlex]
	if ( dx == 0 ) return dy;
	if ( dy == 0 ) return dx;

	if ( dx < dy )
	{
		min = dx;
		max = dy;
	} else {
		min = dy;
		max = dx;
	}
   // coefficients equivalent to ( 123/128 * max ) and ( 51/128 * min )
	return ((( max << 8 ) + ( max << 3 ) - ( max << 4 ) - ( max << 1 ) +
		( min << 7 ) - ( min << 5 ) + ( min << 3 ) - ( min << 1 )) >> 8 );
#else
	if (dx < 0) dx = -dx;
	if (dy < 0) dy = -dy;
	return (dx<dy?dy:dx);
#endif
}