// 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,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;
}

/*==========================================
 * 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(int m,int x0,int y0,int dx,int 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,int m,int x0,int y0,int x1,int 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,int m,int x0,int y0,int x1,int 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;
        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;
    }

    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
}