/*
    Copyright (C) 1996-1997  Id Software, Inc.
    Copyright (C) 1997       Greg Lewis

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

    See file, 'COPYING', for details.
*/
// portals.c

#include <qbsp/brush.hh>
#include <qbsp/portals.hh>

#include <qbsp/map.hh>
#include <qbsp/solidbsp.hh>
#include <qbsp/qbsp.hh>

#include <atomic>

#include "tbb/task_group.h"

/*
=============
AddPortalToNodes
=============
*/
static void AddPortalToNodes(portal_t *p, node_t *front, node_t *back)
{
    if (p->nodes[0] || p->nodes[1])
        FError("portal already included");

    p->nodes[0] = front;
    p->next[0] = front->portals;
    front->portals = p;

    p->nodes[1] = back;
    p->next[1] = back->portals;
    back->portals = p;
}

/*
=============
RemovePortalFromNode
=============
*/
static void RemovePortalFromNode(portal_t *portal, node_t *l)
{
    portal_t **pp, *t;

    // remove reference to the current portal
    pp = &l->portals;
    while (1) {
        t = *pp;
        if (!t)
            FError("Portal not in leaf");

        if (t == portal)
            break;

        if (t->nodes[0] == l)
            pp = &t->next[0];
        else if (t->nodes[1] == l)
            pp = &t->next[1];
        else
            FError("Portal not bounding leaf");
    }

    if (portal->nodes[0] == l) {
        *pp = portal->next[0];
        portal->nodes[0] = NULL;
    } else if (portal->nodes[1] == l) {
        *pp = portal->next[1];
        portal->nodes[1] = NULL;
    }
}

/*
================
MakeHeadnodePortals

The created portals will face the global outside_node
================
*/
void MakeHeadnodePortals(tree_t *tree)
{
    int i, j, n;
    portal_t *p, *portals[6];
    qbsp_plane_t bplanes[6];
    side_t side;

    // pad with some space so there will never be null volume leafs
    aabb3d bounds = tree->bounds.grow(SIDESPACE);

    tree->outside_node.planenum = PLANENUM_LEAF;
    tree->outside_node.contents = options.target_game->create_solid_contents();
    tree->outside_node.portals = NULL;

    // create 6 portals forming a cube around the bounds of the map.
    // these portals will have `outside_node` on one side, and headnode on the other.
    for (i = 0; i < 3; i++)
        for (j = 0; j < 2; j++) {
            n = j * 3 + i;

            p = new portal_t{};
            portals[n] = p;

            qplane3d &pl = bplanes[n] = {};

            if (j) {
                pl.normal[i] = -1;
                pl.dist = -bounds[j][i];
            } else {
                pl.normal[i] = 1;
                pl.dist = bounds[j][i];
            }
            p->planenum = FindPlane(pl, &side);

            p->winding = BaseWindingForPlane(pl);
            if (side)
                AddPortalToNodes(p, &tree->outside_node, tree->headnode);
            else
                AddPortalToNodes(p, tree->headnode, &tree->outside_node);
        }

    // clip the basewindings by all the other planes
    for (i = 0; i < 6; i++) {
        for (j = 0; j < 6; j++) {
            if (j == i)
                continue;
            portals[i]->winding = portals[i]->winding->clip(bplanes[j], options.epsilon.value(), true)[SIDE_FRONT];
        }
    }
}

//============================================================================

/*
================
BaseWindingForNode

Creates a winding from the given node plane, clipped by all parent nodes.
================
*/
#define	BASE_WINDING_EPSILON	0.001
#define	SPLIT_WINDING_EPSILON	0.001

std::optional<winding_t> BaseWindingForNode(node_t *node)
{
    auto plane = map.planes.at(node->planenum);

    std::optional<winding_t> w = BaseWindingForPlane(plane);

    // clip by all the parents
    for (node_t *np = node->parent; np && w; )
    {
        plane = map.planes.at(np->planenum);

        const side_t keep = (np->children[0] == node) ?
            SIDE_FRONT : SIDE_BACK;

        w = w->clip(plane, BASE_WINDING_EPSILON, false)[keep];

        node = np;
        np = np->parent;
    }

    return w;
}

/*
==================
MakeNodePortal

create the new portal by taking the full plane winding for the cutting plane
and clipping it by all of parents of this node, as well as all the other
portals in the node.
==================
*/
void MakeNodePortal(node_t *node, portalstats_t &stats)
{
    auto w = BaseWindingForNode(node);

    // clip the portal by all the other portals in the node
    int side = -1;
    for (auto *p = node->portals; p && w; p = p->next[side]) {
        qbsp_plane_t plane;
        if (p->nodes[0] == node)
        {
            side = 0;
            plane = map.planes.at(p->planenum);
        }
        else if (p->nodes[1] == node)
        {
            side = 1;
            plane = -map.planes.at(p->planenum);
        }
        else
            Error("CutNodePortals_r: mislinked portal");

        w = w->clip(plane, 0.1, false)[SIDE_FRONT];
    }

    if (!w)
    {
        return;
    }

    if (WindingIsTiny(*w))
    {
        stats.c_tinyportals++;
        return;
    }

    auto *new_portal = new portal_t{};
    new_portal->planenum = node->planenum;
    new_portal->onnode = node;
    new_portal->winding = w;
    AddPortalToNodes(new_portal, node->children[0], node->children[1]);
}

/*
==============
SplitNodePortals

Move or split the portals that bound node so that the node's
children have portals instead of node.
==============
*/
void SplitNodePortals(node_t *node, portalstats_t &stats)
{
    const auto plane = map.planes.at(node->planenum);
    node_t *f = node->children[0];
    node_t *b = node->children[1];

    portal_t *next_portal = nullptr;
    for (portal_t *p = node->portals; p ; p = next_portal)
    {
        side_t side;
        if (p->nodes[SIDE_FRONT] == node)
            side = SIDE_FRONT;
        else if (p->nodes[SIDE_BACK] == node)
            side = SIDE_BACK;
        else
            FError("CutNodePortals_r: mislinked portal");
        next_portal = p->next[side];

        node_t *other_node = p->nodes[!side];
        RemovePortalFromNode(p, p->nodes[0]);
        RemovePortalFromNode(p, p->nodes[1]);

        //
        // cut the portal into two portals, one on each side of the cut plane
        //
        auto [frontwinding, backwinding] = p->winding->clip(plane, SPLIT_WINDING_EPSILON, true);

        if (frontwinding && WindingIsTiny(*frontwinding))
        {
            frontwinding = {};
            stats.c_tinyportals++;
        }

        if (backwinding && WindingIsTiny(*backwinding))
        {
            backwinding = {};
            stats.c_tinyportals++;
        }

        if (!frontwinding && !backwinding)
        {	// tiny windings on both sides
            continue;
        }

        if (!frontwinding)
        {
            if (side == SIDE_FRONT)
                AddPortalToNodes(p, b, other_node);
            else
                AddPortalToNodes(p, other_node, b);
            continue;
        }
        if (!backwinding)
        {
            if (side == SIDE_FRONT)
                AddPortalToNodes(p, f, other_node);
            else
                AddPortalToNodes(p, other_node, f);
            continue;
        }

        // the winding is split
        auto *new_portal = new portal_t{*p};
        new_portal->winding = backwinding;
        p->winding = frontwinding;

        if (side == SIDE_FRONT)
        {
            AddPortalToNodes(p, f, other_node);
            AddPortalToNodes(new_portal, b, other_node);
        }
        else
        {
            AddPortalToNodes(p, other_node, f);
            AddPortalToNodes(new_portal, other_node, b);
        }
    }

    node->portals = nullptr;
}

/*
================
CalcNodeBounds
================
*/
void CalcNodeBounds(node_t *node)
{
    // calc mins/maxs for both leafs and nodes
    node->bounds = aabb3d{};

    for (portal_t *p = node->portals; p ;) {
        int s = (p->nodes[1] == node);
        for (auto &point : *p->winding) {
            node->bounds += point;
        }
        p = p->next[s];
    }
}

/*
==================
MakeTreePortals_r
==================
*/
void MakeTreePortals_r(node_t *node, portalstats_t &stats)
{
    CalcNodeBounds(node);
    if (node->bounds.mins()[0] >= node->bounds.maxs()[0])
    {
        printf ("WARNING: node without a volume\n");

        // fixme-brushbsp: added this to work around leafs with no portals showing up in "qbspfeatures.map" among other
        // test maps. Not sure if correct or there's another underlying problem.
        node->bounds = { node->parent->bounds.mins(), node->parent->bounds.mins() };
    }

    for (int i = 0; i < 3; i++)
    {
        if (fabs(node->bounds.mins()[i]) > options.worldextent.value())
        {
            printf ("WARNING: node with unbounded volume\n");
            break;
        }
    }
    if (node->planenum == PLANENUM_LEAF)
        return;

    MakeNodePortal(node, stats);
    SplitNodePortals(node, stats);

    MakeTreePortals_r(node->children[0], stats);
    MakeTreePortals_r(node->children[1], stats);
}

/*
==================
MakeTreePortals
==================
*/
void MakeTreePortals(tree_t *tree)
{
    FreeTreePortals_r(tree->headnode);

    AssertNoPortals(tree->headnode);

    portalstats_t stats{};

    MakeHeadnodePortals(tree);
    MakeTreePortals_r(tree->headnode, stats);
}

void AssertNoPortals(node_t *node)
{
    Q_assert(!node->portals);

    if (node->planenum != PLANENUM_LEAF) {
        AssertNoPortals(node->children[0]);
        AssertNoPortals(node->children[1]);
    }
}

/*
==================
FreeTreePortals_r

==================
*/
void FreeTreePortals_r(node_t *node)
{
    portal_t *p, *nextp;

    if (node->planenum != PLANENUM_LEAF) {
        FreeTreePortals_r(node->children[0]);
        FreeTreePortals_r(node->children[1]);
    }

    for (p = node->portals; p; p = nextp) {
        if (p->nodes[0] == node)
            nextp = p->next[0];
        else
            nextp = p->next[1];
        RemovePortalFromNode(p, p->nodes[0]);
        RemovePortalFromNode(p, p->nodes[1]);
        delete p;
    }
    node->portals = nullptr;
}