// 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/showmsg.h"
#include "../common/malloc.h"
#include "map.h"
#include "battle.h"

#ifdef MEMWATCH
#include "memwatch.h"
#endif

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


//#define PATH_STANDALONETEST

#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)
 * costが減ったので根の方へ移動
 *------------------------------------------*/
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,int x1,int 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,int x,int 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;
}


/*==========================================
 * is (x,y) passable?
 * flag: 0x10000 = ranged attack check
 *       0x30000 = stacking check
 *------------------------------------------*/
static int can_place(struct map_data *m,int x,int y,int flag)
{
	if( map_getcellp(m,x,y,CELL_CHKPASS) )
		return 1;
	if( (flag&0x10000)&&map_getcellp(m,x,y,CELL_CHKGROUND) )
		return 1;
#ifdef CELL_NOSTACK
	//Special flag for CELL_NOSTACK systems. Returns true when the given cell is stacked. [Skotlex]
	if( (flag&0x30000)&&map_getcellp(m,x,y,CELL_CHKSTACK) )
		return 1;
#endif
	return 0;
}

/*==========================================
 * can you move from (x0,y0) to (x1,y1) in one step?
 * (helper function for path_blownpos())
 *------------------------------------------*/
static int can_move(struct map_data *m,int x0,int y0,int x1,int y1,int flag)
{
	if( x1 < 0 || y1 < 0 || x1 >= m->xs || y1 >= m->ys)
		return 0; // out-of-bounds coordinates
	if( flag&0x20000 ) //Flag to ignore everything, for use with Taekwon's Jump skill currently. [Skotlex] 
		return 1;
#ifndef CELL_NOSTACK
	//In no-stack mode, do not check current cell.
	if( !can_place(m,x0,y0,flag) )
		return 0;
#endif
	if( !can_place(m,x1,y1,flag) )
		return 0;
	if( x0 == x1 || y0 == y1 )
		return 1;
	if( !can_place(m,x0,y1,flag) || !can_place(m,x1,y0,flag) )
		return 0;
	return 1;
}

/*==========================================
 * (x0,y0)から(dx,dy)方向へcountセル分
 * 吹き飛ばしたあとの座標を所得
 *------------------------------------------*/
int path_blownpos(int m,int x0,int y0,int dx,int dy,int count)
{
	struct map_data *md;

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

	if( count>25 ){ //Cap to prevent too much processing...?
		if( battle_config.error_log )
			ShowWarning("path_blownpos: count too many %d !\n",count);
		count=25;
	}
	if( dx > 1 || dx < -1 || dy > 1 || dy < -1 ){
		if( battle_config.error_log )
			ShowError("path_blownpos: illeagal 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 || dy) )
	{
		if( !can_move(md,x0,y0,x0+dx,y0+dy,0) ){
			int fx=(dx!=0 && can_move(md,x0,y0,x0+dx,y0,0));
			int fy=(dy!=0 && can_move(md,x0,y0,x0,y0+dy,0));
			if( fx && fy ){
				if(rand()&1) dx=0;
				else		 dy=0;
			}
			if( !fx )		dx=0;
			if( !fy )		dy=0;
		}
		x0+=dx;
		y0+=dy;
	}
	return (x0<<16)|y0;
}

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

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

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

	if (spd) {
		spd->rx = spd->ry = 0;
		spd->len = 1;
		spd->x[0] = x0;
		spd->y[0] = y0;
	}

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

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

	while (x0 != x1 || y0 != y1) {
		if (map_getcellp(md,x0,y0,flag))
			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 && spd->len<MAX_WALKPATH) {
			spd->x[spd->len] = x0;
			spd->y[spd->len] = y0;
			spd->len++;
		}
	}

	return true;
}

/*==========================================
 * path search (x0,y0)->(x1,y1)
 * flag: &1 = easy path search only
 *------------------------------------------*/
int path_search_real(struct walkpath_data *wpd,int m,int x0,int y0,int x1,int y1,int flag,cell_t flag2)
{
	int heap[MAX_HEAP+1];
	struct tmp_path tp[MAX_WALKPATH*MAX_WALKPATH];
	register int i,x,y,dx,dy;
	int rp,xs,ys;
	struct map_data *md;

	nullpo_retr(0, wpd);

	if( !map[m].gat )
		return -1;
	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,flag2)*/ )
#endif
		return -1;
	if( x1 < 0 || x1 >= md->xs || y1 < 0 || y1 >= md->ys || map_getcellp(md,x1,y1,flag2) )
		return -1;

	// 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
	for( x = x0, y = y0, i = 0; i < ARRAYLENGTH(wpd->path); )
	{
		wpd->path[i++] = walk_choices[-dy + 1][dx + 1];

		x += dx;
		y += dy;

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

		if( !dx && !dy )
			break; // success
		if( map_getcellp(md,x,y,flag2) )
			break; // obstacle = failure
	}

	if( x == x1 && y == y1 )
	{ //easy path successful.
		wpd->path_len = i;
		wpd->path_pos = 0;
		wpd->path_half = 0;
		return 0;
	}
	
	if( flag&1 )
		return -1;

	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; // あらかじめ１減算しておく
	ys = md->ys-1;
	while(1){
		int e=0,f=0,dist,cost,dc[4]={0,0,0,0};

		if(heap[0]==0)
			return -1;
		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++ の時のコスト増分
		// dc[1] : x-- の時のコスト増分
		// dc[2] : y-- の時のコスト増分
		// dc[3] : x++ の時のコスト増分

		if(y < ys && !map_getcellp(md,x  ,y+1,flag2)) {
			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  ,flag2)) {
			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,flag2)) {
			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  ,flag2)) {
			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,flag2))
			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,flag2))
			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,flag2))
			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,flag2))
			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 -1;
	}
	if(x==x1 && y==y1) {
		int len,j;

		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 -1;
		wpd->path_len=len;
		wpd->path_pos=0;
		wpd->path_half=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;
			int 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;
		}
#if 0
		// test
		{
			int dirx[8]={0,-1,-1,-1,0,1,1,1};
			int diry[8]={1,1,0,-1,-1,-1,0,1};
			x = x0; y = y0;
			for(i = 0; i < wpd->path_len; i++) {
				x += dirx[ wpd->path[i] ];
				y += diry[ wpd->path[i] ];
				if( map_getcellp(md,x,y,flag2) ) {
					printf("path_search_real: cannot move(%d, %d)\n", x, y);
					return -1;
				}
			}
			if( x != x1 || y != y1 ) {
				printf("path_search_real: dest position is wrong. ok:(%d, %d) ng:(%d,%d)\n", x1, y1, x, y);
				return -1;
			}
		}
#endif
		return 0;
	}
	return -1;
}