cp_mission_intercept.cpp

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/*
Copyright (C) 2002-2025 UFO: Alien Invasion.
 
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.
*/
 
#include "../../../DateTime.h"
#include "../../../cl_shared.h"
#include "../cp_campaign.h"
#include "../cp_ufo.h"
#include "../cp_missions.h"
#include "../cp_time.h"
#include "../cp_alien_interest.h"
#include "../cp_xvi.h"
#include "cp_mission_intercept.h"

void CP_InterceptMissionIsSuccess (mission_t* mission)
{
    INT_ChangeIndividualInterest(0.3f, INTERESTCATEGORY_RECON);
    INT_ChangeIndividualInterest(-0.3f, INTERESTCATEGORY_INTERCEPT);
    INT_ChangeIndividualInterest(0.1f, INTERESTCATEGORY_HARVEST);
    if (CP_IsXVIStarted())
        INT_ChangeIndividualInterest(0.1f, INTERESTCATEGORY_XVI);
 
    CP_MissionRemove(mission);
}

void CP_InterceptMissionIsFailure (mission_t* mission)
{
    INT_ChangeIndividualInterest(0.1f, INTERESTCATEGORY_INTERCEPT);
    INT_ChangeIndividualInterest(0.05f, INTERESTCATEGORY_BUILDING);
    INT_ChangeIndividualInterest(0.05f, INTERESTCATEGORY_BASE_ATTACK);
    INT_ChangeIndividualInterest(0.05f, INTERESTCATEGORY_TERROR_ATTACK);
 
    CP_MissionRemove(mission);
}
 
#define UFO_EPSILON 0.00001f

void CP_InterceptMissionLeave (mission_t* mission, bool destroyed)
{
    installation_t* installation;
 
    assert(mission->ufo);
 
    mission->stage = STAGE_RETURN_TO_ORBIT;
 
    /* if the mission was an attack of an installation, destroy it */
    installation = mission->data.installation;
    if (installation) {
        vec3_t missionPos;
 
        Vector2Copy(mission->pos, missionPos);
        missionPos[2] = installation->pos[2];
        if (destroyed && VectorCompareEps(missionPos, installation->pos, UFO_EPSILON))
            INS_DestroyInstallation(installation);
    }
 
    CP_MissionDisableTimeLimit(mission);
    UFO_SetRandomDest(mission->ufo);
    CP_MissionRemoveFromGeoscape(mission);
    /* Display UFO on geoscape if it is detected */
    mission->ufo->landed = false;
}

static void CP_InterceptAttackInstallation (mission_t* mission)
{
    const DateTime minAttackDelay(0, 3600);
    const DateTime maxAttackDelay(0, 21600);        /* How long the UFO should stay on earth */
    installation_t* installation;
    vec3_t missionPos;
 
    mission->stage = STAGE_INTERCEPT;
 
    installation = mission->data.installation;
    Vector2Copy(mission->pos, missionPos);
    if (!VectorCompareEps(missionPos, installation->pos, UFO_EPSILON)) {
        mission->finalDate = ccs.date;
        return;
    }
 
    /* Make round around the position of the mission */
    UFO_SetRandomDestAround(mission->ufo, mission->pos);
    mission->finalDate = ccs.date + Date_Random(minAttackDelay, maxAttackDelay);
}

void CP_InterceptAircraftMissionSet (mission_t* mission)
{
    const DateTime minReconDelay(3, 0);
    const DateTime maxReconDelay(6, 0);     /* How long the UFO should stay on earth */
 
    mission->stage = STAGE_INTERCEPT;
    mission->finalDate = ccs.date + Date_Random(minReconDelay, maxReconDelay);
}

static installation_t* CP_InterceptChooseInstallation (const mission_t* mission)
{
    float randomNumber, sum = 0.0f;
    installation_t* installation = nullptr;
 
    assert(mission);
 
    /* Choose randomly a base depending on alienInterest values for those bases */
    INS_Foreach(i) {
        sum += i->alienInterest;
    }
    randomNumber = frand() * sum;
    INS_Foreach(i) {
        randomNumber -= i->alienInterest;
        if (randomNumber < 0) {
            installation = i;
            break;
        }
    }
 
    /* Make sure we have a base */
    assert(installation && (randomNumber < 0));
 
    return installation;
}

void CP_InterceptGoToInstallation (mission_t* mission)
{
    installation_t* installation;
    assert(mission->ufo);
 
    mission->stage = STAGE_MISSION_GOTO;
 
    installation = CP_InterceptChooseInstallation(mission);
    if (!installation) {
        cgi->Com_Printf("CP_InterceptGoToInstallation: no installation found\n");
        CP_MissionRemove(mission);
        return;
    }
    mission->data.installation = installation;
 
    Vector2Copy(installation->pos, mission->pos);
    mission->posAssigned = true;
 
    CP_MissionDisableTimeLimit(mission);
    UFO_SendToDestination(mission->ufo, mission->pos);
}

static void CP_InterceptMissionSet (mission_t* mission)
{
    assert(mission->ufo);
 
    /* Only large UFOs can attack installations -- if there are installations to attack */
    if (UFO_CanDoMission(mission->ufo->getUfoType(), "interceptbombing"))
        if (INS_HasAny()) {
            /* Probability to get a UFO that targets installations. */
            const float TARGET_INS_PROBABILITY = 0.25;
            /* don't make attack on installation happen too often */
            if (frand() < TARGET_INS_PROBABILITY)
                CP_InterceptGoToInstallation(mission);
        }
 
    /* if not attacking an installation */
    if (mission->stage != STAGE_MISSION_GOTO)
        CP_InterceptAircraftMissionSet(mission);
}

void CP_InterceptNextStage (mission_t* mission)
{
    switch (mission->stage) {
    case STAGE_NOT_ACTIVE:
        /* Create Intercept mission */
        CP_MissionBegin(mission);
        break;
    case STAGE_COME_FROM_ORBIT:
        /* UFO start looking for target */
        CP_InterceptMissionSet(mission);
        break;
    case STAGE_MISSION_GOTO:
        CP_InterceptAttackInstallation(mission);
        break;
    case STAGE_INTERCEPT:
        assert(mission->ufo);
        /* Leave earth */
        if (AIRFIGHT_ChooseWeapon(mission->ufo->weapons, mission->ufo->maxWeapons, mission->ufo->pos, mission->ufo->pos) !=
            AIRFIGHT_WEAPON_CAN_NEVER_SHOOT && mission->ufo->status == AIR_UFO && !mission->data.installation) {
            /* UFO is fighting and has still ammo, wait a little bit before leaving (UFO is not attacking an installation) */
            const DateTime additionalDelay(0, 3600);    /* check every hour if there is still ammos */
            mission->finalDate = ccs.date + additionalDelay;
        } else
            CP_InterceptMissionLeave(mission, true);
        break;
    case STAGE_RETURN_TO_ORBIT:
        /* mission is over, remove mission */
        CP_InterceptMissionIsSuccess(mission);
        break;
    default:
        cgi->Com_Printf("CP_InterceptNextStage: Unknown stage: %i, removing mission.\n", mission->stage);
        CP_MissionRemove(mission);
        break;
    }
}