#include "../kernel/dispatch.h"
#include "../kernel/client.h"
#include "../kernel/frame.h"
#include "../kernel/stacking.h"
#include "../kernel/screen.h"
#include <glib.h>

static int resistance = 10;
static gboolean window_resistance = TRUE; /* window-to-window */

static void resist(Client *c, int *x, int *y)
{
    GList *it;
    Rect *area;
    int l, t, r, b; /* requested edges */
    int al, at, ar, ab; /* screen area edges */
    int cl, ct, cr, cb; /* current edges */
    int w, h; /* current size */
    gboolean snapx = FALSE, snapy = FALSE;

    w = c->frame->area.width;
    h = c->frame->area.height;

    l = *x;
    t = *y;
    r = l + w - 1;
    b = t + h - 1;

    cl = c->frame->area.x;
    ct = c->frame->area.y;
    cr = cl + c->frame->area.width - 1;
    cb = ct + c->frame->area.height - 1;
    
    /* snap to other clients */
    if (window_resistance)
        for (it = stacking_list; it != NULL; it = it->next) {
            Client *target;
            int tl, tt, tr, tb; /* 1 past the target's edges on each side */

            target = it->data;
            /* don't snap to self or non-visibles */
            if (!target->frame->visible || target == c) continue; 

            tl = target->frame->area.x - 1;
            tt = target->frame->area.y - 1;
            tr = tl + target->frame->area.width + 1;
            tb = tt + target->frame->area.height + 1;

            /* snapx and snapy ensure that the window snaps to the top-most
               window edge available, without going all the way from
               bottom-to-top in the stacking list
            */
            if (!snapx && cl >= tr && l < tr && l >= tr - resistance)
                *x = tr, snapx = TRUE;
            else if (!snapx && cr <= tl && r > tl && r <= tl + resistance)
                *x = tl - w + 1, snapx = TRUE;
            else if (!snapy && ct >= tb && t < tb && t >= tb - resistance)
                *y = tb, snapy = TRUE;
            else if (!snapy && cb <= tt && b > tt && b <= tt + resistance)
                *y = tt - h + 1, snapy = TRUE;

            if (snapx && snapy) break;
        }

    /* get the screen boundaries */
    area = screen_area(c->desktop);
    al = area->x;
    at = area->y;
    ar = al + area->width - 1;
    ab = at + area->height - 1;

    /* snap to screen edges */
    if (cl >= al && l < al && l >= al - resistance)
        *x = al;
    else if (cr <= ar && r > ar && r <= ar + resistance)
            *x = ar - w + 1;
    if (ct >= at && t < at && t >= at - resistance)
        *y = at;
    else if (cb <= ab && b > ab && b < ab + resistance)
        *y = ab - h + 1;
}

static void event(ObEvent *e, void *foo)
{
    g_assert(e->type == Event_Client_Moving);

    resist(e->data.c.client, &e->data.c.num[0], &e->data.c.num[1]);
}

void plugin_startup()
{
    dispatch_register(Event_Client_Moving, (EventHandler)event, NULL);
}

void plugin_shutdown()
{
    dispatch_register(0, (EventHandler)event, NULL);
}