/**
 * @file
 * @brief Monster abilities.
**/

#include "AppHdr.h"

#include "mon-abil.h"

#include <algorithm>
#include <cmath>
#include <map>
#include <queue>
#include <set>

#include "act-iter.h"
#include "actor.h"
#include "areas.h"
#include "arena.h"
#include "beam.h"
#include "cloud.h"
#include "colour.h"
#include "coordit.h"
#include "database.h"
#include "delay.h"
#include "dgn-overview.h"
#include "directn.h"
#include "dungeon.h"
#include "english.h"
#include "env.h"
#include "fineff.h"
#include "fprop.h"
#include "god-abil.h"
#include "item-prop.h"
#include "libutil.h"
#include "losglobal.h"
#include "map-knowledge.h"
#include "message.h"
#include "mgen-data.h"
#include "mon-act.h"
#include "mon-behv.h"
#include "mon-cast.h"
#include "mon-death.h"
#include "mon-pathfind.h"
#include "mon-place.h"
#include "mon-poly.h"
#include "mon-speak.h"
#include "mon-util.h"
#include "notes.h"
#include "ouch.h"
#include "random.h"
#include "religion.h"
#include "spl-damage.h"
#include "spl-summoning.h"
#include "spl-util.h"
#include "state.h"
#include "stringutil.h"
#include "target.h"
#include "teleport.h"
#include "terrain.h"
#include "transform.h"
#include "view.h"
#include "viewchar.h"
#include "viewmap.h"

static bool _slime_split_merge(monster* thing);

// Currently only used for Tiamat.
void draconian_change_colour(monster* drac)
{
    if (mons_genus(drac->type) != MONS_DRACONIAN)
        return;

    drac->base_monster = random_choose(MONS_RED_DRACONIAN,
                                       MONS_WHITE_DRACONIAN,
                                       MONS_BLACK_DRACONIAN,
                                       MONS_GREEN_DRACONIAN,
                                       MONS_PURPLE_DRACONIAN,
                                       MONS_YELLOW_DRACONIAN);
    drac->colour = mons_class_colour(drac->base_monster);

    // Get rid of the old breath weapon first.
    monster_spells oldspells = drac->spells;
    drac->spells.clear();
    for (const mon_spell_slot &slot : oldspells)
        if (!(slot.flags & MON_SPELL_BREATH))
            drac->spells.push_back(slot);

    drac->spells.push_back(drac_breath(draconian_subspecies(*drac)));
}

void boris_covet_orb(monster* boris)
{
    if (boris->type != MONS_BORIS || !player_has_orb())
        return;

    if (boris->observable())
        simple_monster_message(*boris, " is empowered by the presence of the orb!");

    boris->add_ench(mon_enchant(ENCH_HASTE, boris, INFINITE_DURATION));
    boris->add_ench(mon_enchant(ENCH_EMPOWERED_SPELLS, boris, INFINITE_DURATION));
}

bool ugly_thing_mutate(monster& ugly, bool force)
{
    if (!(one_chance_in(9) || force))
        return false;

    const char* msg = nullptr;
    // COLOUR_UNDEF means "pick a random colour".
    colour_t new_colour = COLOUR_UNDEF;

    for (fair_adjacent_iterator ai(ugly.pos()); ai && !msg; ++ai)
    {
        const actor* act = actor_at(*ai);

        if (!act)
            continue;

        if (act->is_player() && player_harmful_contamination())
        {
            msg = " basks in your mutagenic energy and changes!";
            break;
        }
        else if (mons_genus(act->type) == MONS_UGLY_THING)
        {
            msg = " basks in the mutagenic energy from its kin and changes!";
            const colour_t other_colour =
                make_low_colour(act->as_monster()->colour);
            if (make_low_colour(ugly.colour) != other_colour)
                new_colour = other_colour;
            break;
        }
    }

    if (force)
        msg = " basks in the mutagenic energy and changes!";

    if (!msg) // didn't find anything to mutate off of
        return false;

    simple_monster_message(ugly, msg);
    ugly.uglything_mutate(new_colour);
    return true;
}

// Returns whether an enchantment should be given to split monsters and inherited on merge.
// TODO: This list is definitely incomplete.
static bool _should_share_ench(enchant_type type)
{
    return type != ENCH_HELD
           && type != ENCH_CONSTRICTED
           && type != ENCH_BULLSEYE_TARGET;
}

// Inflict any enchantments the parent slime has on its offspring,
// leaving durations unchanged, I guess. -cao
static void _share_ench_durations(monster* initial_slime, monster* split_off)
{
    for (const auto &entry : initial_slime->enchantments)
    {
        if (_should_share_ench(entry.second.ench))
        {
            split_off->add_ench(entry.second);

            // The newly split slime will also be vengeance marked, so we need
            // to increment the total number of monsters the player has to kill
            if (entry.second.ench == ENCH_VENGEANCE_TARGET)
                you.duration[DUR_BEOGH_SEEKING_VENGEANCE] += 1;
        }
    }
}

// What to do about any enchantments these two creatures may have?
// For now, we are averaging the durations, weighted by slime size
// or by hit dice, depending on usehd.
void merge_ench_durations(monster& initial, monster& merge_to, bool usehd)
{
    int initial_count = usehd ? initial.get_hit_dice() : initial.blob_size;
    int merge_to_count = usehd ? merge_to.get_hit_dice() : merge_to.blob_size;
    int total_count = initial_count + merge_to_count;

    mon_enchant_list &from_ench = initial.enchantments;

    for (auto &entry : from_ench)
    {
        if (!_should_share_ench(entry.second.ench))
            continue;

        // Does the other creature have this enchantment as well?
        const mon_enchant temp = merge_to.get_ench(entry.first);
        // If not, use duration 0 for their part of the average.
        const bool no_initial = temp.ench == ENCH_NONE;
        const int duration = no_initial ? 0 : temp.duration;

        entry.second.duration = (entry.second.duration * initial_count
                                 + duration * merge_to_count)/total_count;

        if (!entry.second.duration)
            entry.second.duration = 1;

        if (no_initial)
            merge_to.add_ench(entry.second);
        else
            merge_to.update_ench(entry.second);
    }

    for (auto &entry : merge_to.enchantments)
    {
        if (from_ench.find(entry.first) == from_ench.end()
            && entry.second.duration > 1)
        {
            entry.second.duration = (merge_to_count * entry.second.duration)
                                    / total_count;

            merge_to.update_ench(entry.second);
        }
    }
}

// Scale current slymdra HP based on head count.
void slymdra_scale_hp(monster& slymdra)
{
    const monsterentry *m_ent = get_monster_data(MONS_SLYMDRA);
    const int new_avg_hp = div_rand_round(m_ent->avg_hp_10x * slymdra.get_hit_dice(), m_ent->HD);
    const int hp = hit_points(new_avg_hp) + SLYMDRA_HP_PER_HEAD * slymdra.num_heads;

    const int diff = slymdra.max_hit_points - hp;
    slymdra.max_hit_points -= diff;
    slymdra.hit_points = max(1, slymdra.hit_points - diff);
}

// Calculate slime creature hp based on how many are merged.
static void _stats_from_blob_count(monster* slime, float max_per_blob,
                                   float current_per_blob)
{
    slime->max_hit_points = (int)(slime->blob_size * max_per_blob);
    slime->hit_points = (int)(slime->blob_size * current_per_blob);
}

// Create a new slime creature at 'target', and split 'thing''s hp and
// merge count with the new monster.
// Returns the new slime (nullptr if it fails).
static monster* _do_split(monster* thing, const coord_def & target, bool quiet = false)
{
    ASSERT(thing); // XXX: change to monster &thing
    ASSERT(thing->alive());

    // Create a new slime.
    monster_type type = thing->type == MONS_SLYMDRA ? MONS_SLIME_CREATURE
                                                    : thing->type;
    mgen_data new_slime_data = mgen_data(type,
                                         SAME_ATTITUDE(thing),
                                         target,
                                         thing->foe,
                                         MG_FORCE_PLACE);

    // Don't explicitly announce the child slime coming into view if you
    // saw the split that created it
    if (you.can_see(*thing))
        new_slime_data.extra_flags |= MF_WAS_IN_VIEW;

    monster *new_slime = create_monster(new_slime_data);

    if (!new_slime)
        return 0;

    if (!quiet && you.can_see(*thing))
    {
        if (thing->type == MONS_SLYMDRA)
        {
            mprf("%s separates from %s.", new_slime->name(DESC_A).c_str(),
                                          thing->name(DESC_A).c_str());
        }
        else
            mprf("%s splits.", thing->name(DESC_A).c_str());
    }

    // Inflict the new slime with any enchantments on the parent.
    _share_ench_durations(thing, new_slime);
    new_slime->attitude = thing->attitude;
    new_slime->behaviour = thing->behaviour;
    new_slime->flags = thing->flags;
    new_slime->props = thing->props;
    new_slime->summoner = thing->summoner;
    if (thing->props.exists(BLAME_KEY))
        new_slime->props[BLAME_KEY] = thing->props[BLAME_KEY].get_vector();
    if (thing->type == MONS_SLYMDRA)
    {
        new_slime->props.erase(POLY_SET_KEY);
        init_poly_set(new_slime);
    }

    // Lose heads and HP equivalent to those heads
    if (thing->type == MONS_SLYMDRA)
    {
        --thing->num_heads;
        const monsterentry *m_ent = get_monster_data(MONS_SLYMDRA);

        const int new_avg_hp = div_rand_round(m_ent->avg_hp_10x * thing->get_hit_dice(), m_ent->HD);
        const int hp = hit_points(new_avg_hp) + SLYMDRA_HP_PER_HEAD * thing->num_heads;

        const int diff = thing->max_hit_points - hp;
        thing->max_hit_points -= diff;
        thing->hit_points = max(1, thing->hit_points - diff);
    }
    else
    {
        int split_off = thing->blob_size / 2;
        float max_per_blob = thing->max_hit_points / float(thing->blob_size);
        float current_per_blob = thing->hit_points / float(thing->blob_size);

        thing->blob_size -= split_off;
        new_slime->blob_size = split_off;

        new_slime->set_hit_dice(thing->get_experience_level());

        _stats_from_blob_count(thing, max_per_blob, current_per_blob);
        _stats_from_blob_count(new_slime, max_per_blob, current_per_blob);
    }

    if (crawl_state.game_is_arena())
        arena_split_monster(thing, new_slime);

    ASSERT(thing->alive());
    ASSERT(new_slime->alive());

    return new_slime;
}

// Cause a monster to lose a turn. has_gone should be true if the
// monster has already moved this turn.
static void _lose_turn(monster* mons, bool has_gone)
{
    const monsterentry* entry = get_monster_data(mons->type);

    // We want to find out if mons will move next time it has a turn
    // (assuming for the sake of argument the next delay is 10). If it's
    // already going to lose a turn we don't need to do anything.
    mons->speed_increment += entry->speed;
    if (!mons->has_action_energy())
        return;
    mons->speed_increment -= entry->speed;

    mons->speed_increment -= entry->energy_usage.move;

    // So we subtracted some energy above, but if mons hasn't moved yet
    // /this turn, that will just cancel its turn in this round of
    // world_reacts().
    if (!has_gone)
        mons->speed_increment -= entry->energy_usage.move;
}

// Actually merge two slime creatures, pooling their hp, etc.
// initial_slime is the one that gets killed off by this process.
static void _do_merge_slimes(monster* initial_slime, monster* merge_to)
{
    const string old_name = merge_to->name(DESC_A);
    const bool merge_to_was_visible = you.can_see(*merge_to);

    // Combine enchantment durations.
    merge_ench_durations(*initial_slime, *merge_to);

    merge_to->blob_size += initial_slime->blob_size;
    merge_to->max_hit_points += initial_slime->max_hit_points;
    merge_to->hit_points += initial_slime->hit_points;

    // Merge monster flags (mostly so that MF_CREATED_NEUTRAL, etc. are
    // passed on if the merged slime subsequently splits. Hopefully
    // this won't do anything weird.
    merge_to->flags |= initial_slime->flags;

    // Transfer duel status over to the merge target.
    if (initial_slime->props.exists(OKAWARU_DUEL_CURRENT_KEY))
    {
        initial_slime->props.erase(OKAWARU_DUEL_CURRENT_KEY);
        merge_to->props[OKAWARU_DUEL_TARGET_KEY] = true;
        merge_to->props[OKAWARU_DUEL_CURRENT_KEY] = true;
    }

    // Merging costs the combined slime some energy. The idea is that if 2
    // slimes merge you can gain a space by moving away the turn after (maybe
    // this is too nice but there will probably be a lot of complaints about
    // the damage on higher level slimes). We see if mons has gone already by
    // checking its mindex (this works because handle_monsters just iterates
    // over env.mons in ascending order).
    _lose_turn(merge_to, merge_to->mindex() < initial_slime->mindex());

    // Overwrite the state of the slime getting merged into, because it
    // might have been resting or something.
    merge_to->behaviour = initial_slime->behaviour;
    merge_to->foe = initial_slime->foe;

    behaviour_event(merge_to, ME_EVAL);

    // Messaging cases:
    // 1. MT & I were both visible & still are
    // 2. MT was visible, I wasn't but now both are
    // 3. MT was visible, I wasn't and now both aren't
    // 4. MT wasn't visible, I was and now both are
    // 5. MT and I weren't visible & still aren't
    if (merge_to_was_visible)
    {
        if (you.can_see(*merge_to))
        {
            // cases 1 and 2
            mprf("Two slime creatures merge to form %s.",
                 merge_to->name(DESC_A).c_str());
        }
        else
        {
            // case 3
            mprf("Something merges into %s, and it vanishes!",
                 old_name.c_str());
        }

        flash_view_delay(UA_MONSTER, LIGHTGREEN, 150);
    }
    else if (you.can_see(*initial_slime))
    {
        // case 4
        mprf("%s merges with something you can't see.",
             initial_slime->name(DESC_A).c_str());
    }
    // case 5 (no-op)

    // Have to 'kill' the slime doing the merging.
    monster_die(*initial_slime, KILL_RESET, NON_MONSTER, true);
}

// Slime creatures can split but not merge under these conditions.
static bool _unoccupied_slime(monster* thing)
{
    return thing->asleep() || mons_is_wandering(*thing)
           || thing->foe == MHITNOT;
}

// Slime creatures cannot split or merge under these conditions.
static bool _disabled_merge(monster* thing)
{
    return !thing
           || mons_is_fleeing(*thing)
           || mons_is_confused(*thing)
           || thing->paralysed()
           || thing->has_ench(ENCH_FRENZIED);
}

// See if there are any appropriate adjacent slime creatures for 'thing'
// to merge with. If so, carry out the merge.
//
// A slime creature will merge if there is an adjacent slime, merging
// onto that slime would reduce the distance to the original slime's
// target, and there are no empty squares that would also reduce the
// distance to the target.
static bool _slime_merge(monster* thing)
{
    if (!thing || _disabled_merge(thing) || _unoccupied_slime(thing))
        return false;

    int max_slime_merge = 5;
    int target_distance = grid_distance(thing->target, thing->pos());

    // Check for adjacent slime creatures.
    monster* merge_target = nullptr;
    for (fair_adjacent_iterator ai(thing->pos()); ai; ++ai)
    {
        // If this square won't reduce the distance to our target, don't
        // look for a potential merge, and don't allow this square to
        // prevent a merge if empty.
        if (grid_distance(thing->target, *ai) >= target_distance)
            continue;

        // Don't merge if there is an open square that reduces distance
        // to target, even if we found a possible slime to merge with.
        if (!actor_at(*ai)
            && monster_habitable_grid(MONS_SLIME_CREATURE, *ai))
        {
            return false;
        }

        // Is there a slime creature on this square we can consider
        // merging with?
        monster* other_thing = monster_at(*ai);
        if (!merge_target
            && other_thing
            && other_thing->type == MONS_SLIME_CREATURE
            && other_thing->attitude == thing->attitude
            && other_thing->has_ench(ENCH_CHARM) == thing->has_ench(ENCH_CHARM)
            && other_thing->has_ench(ENCH_HEXED) == thing->has_ench(ENCH_HEXED)
            && other_thing->is_summoned() == thing->is_summoned()
            && !other_thing->is_shapeshifter()
            && other_thing->has_ench(ENCH_FIGMENT) == thing->has_ench(ENCH_FIGMENT)
            && other_thing->is_unrewarding() == thing->is_unrewarding()
            && !_disabled_merge(other_thing))
        {
            // We can potentially merge if doing so won't take us over
            // the merge cap.
            int new_blob_count = other_thing->blob_size + thing->blob_size;
            if (new_blob_count <= max_slime_merge)
                merge_target = other_thing;
        }
    }

    // We found a merge target and didn't find an open square that
    // would reduce distance to target, so we can actually merge.
    if (merge_target)
    {
        _do_merge_slimes(thing, merge_target);
        return true;
    }

    // No adjacent slime creatures we could merge with.
    return false;
}

static bool _slime_can_spawn(const coord_def target)
{
    return monster_habitable_grid(MONS_SLIME_CREATURE, target)
           && !actor_at(target);
}

// See if slime creature 'thing' can split, and carry out the split if
// we can find a square to place the new slime creature on.
static monster *_slime_split(monster* thing, bool force_split, bool quiet = false)
{
    if (!thing || thing->blob_size <= 1 || thing->hit_points < 4
        || (coinflip() && !force_split) // Don't make splitting quite so reliable. (jpeg)
        || _disabled_merge(thing))
    {
        return 0;
    }

    const coord_def origin  = thing->pos();

    const actor* foe        = thing->get_foe();
    const bool has_foe      = (foe != nullptr && thing->can_see(*foe));
    const coord_def foe_pos = (has_foe ? foe->position : coord_def(0,0));
    const int old_dist      = (has_foe ? grid_distance(origin, foe_pos) : 0);

    if ((has_foe && old_dist > 1) && !force_split)
    {
        // If we're not already adjacent to the foe, check whether we can
        // move any closer. If so, do that rather than splitting.
        for (adjacent_iterator ri(origin); ri; ++ri)
        {
            if (_slime_can_spawn(*ri)
                && grid_distance(*ri, foe_pos) < old_dist)
            {
                return 0;
            }
        }
    }

    // Anywhere we can place an offspring?
    for (fair_adjacent_iterator ai(origin); ai; ++ai)
    {
        // Don't split if this increases the distance to the target.
        if (has_foe && grid_distance(*ai, foe_pos) > old_dist
            && !force_split)
        {
            continue;
        }

        if (_slime_can_spawn(*ai))
        {
            // This can fail if placing a new monster fails. That
            // probably means we have too many monsters on the level,
            // so just return in that case.
            return _do_split(thing, *ai, quiet);
        }
    }

    // No free squares.
    return 0;
}

// See if a given slime creature can split or merge.
static bool _slime_split_merge(monster* thing)
{
    // No merging/splitting shapeshifters.
    if (!thing
        || thing->is_shapeshifter()
        || thing->type != MONS_SLIME_CREATURE)
    {
        return false;
    }

    if (_slime_split(thing, false))
        return true;

    return _slime_merge(thing);
}

// Splits and polymorphs merged slime creatures.
bool slime_creature_polymorph(monster& slime, poly_power_type power)
{
    ASSERT(slime.type == MONS_SLIME_CREATURE);

    if (slime.blob_size > 1 && x_chance_in_y(4, 5))
    {
        int count = 0;
        while (slime.blob_size > 1 && count <= 10)
        {
            if (monster *splinter = _slime_split(&slime, true))
                slime_creature_polymorph(*splinter, power);
            else
                break;
            count++;
        }
    }

    return monster_polymorph(&slime, RANDOM_POLYMORPH_MONSTER, power);
}

int slymdra_split(monster& slymdra, int count, bool quiet)
{
    ASSERT(slymdra.type == MONS_SLYMDRA);

    int num_splits = 0;
    int& fake_heads = slymdra.props[SLYMDRA_FAKE_HEADS_KEY].get_int();
    int& real_slimes = slymdra.props[SLYMDRA_SLIMES_EATEN_KEY].get_int();
    if (count == -1)
        count = slymdra.num_heads - 4;

    if (count <= 0 || real_slimes == 0 && fake_heads == 0)
        return 0;
    for (distance_iterator di(slymdra.pos(), true, true, 2); di; ++di)
    {
        if (cell_see_cell(slymdra.pos(), *di, LOS_NO_TRANS) && _slime_can_spawn(*di))
        {
            if (monster* slime = _do_split(&slymdra, *di, quiet))
            {
                if (real_slimes > 0)
                    --real_slimes;
                else
                {
                    slime->flags |= (MF_NO_REWARD | MF_HARD_RESET);
                    --fake_heads;
                }

                // If we've split out as many things as we want or as many as we *can*, return.
                if (++num_splits >= count || real_slimes == 0 && fake_heads == 0)
                    return num_splits;
            }
        }
    }

    return num_splits;
}

bool slymdra_polymorph(monster& slymdra, poly_power_type power)
{
    ASSERT(slymdra.type == MONS_SLYMDRA);
    int count = slymdra_split(slymdra, -1, true);

    if (you.can_see(slymdra) && count > 0)
    {
        if (count == 1)
        {
            mprf("A slime creature is ejected from %s body as it begins to warp and change.",
                 slymdra.name(DESC_ITS).c_str());
        }
        else
        {
            mprf("%d slime creatures are ejected from %s body as it begins to warp and change.",
                 count, slymdra.name(DESC_ITS).c_str());
        }
    }

    return monster_polymorph(&slymdra, RANDOM_POLYMORPH_MONSTER, power);
}

static bool _starcursed_split(monster* mon)
{
    if (!mon || mon->blob_size <= 1 || mon->type != MONS_STARCURSED_MASS)
        return false;

    // Anywhere we can place an offspring?
    for (fair_adjacent_iterator ai(mon->pos()); ai; ++ai)
    {
        if (mons_class_can_pass(MONS_STARCURSED_MASS, env.grid(*ai))
            && !actor_at(*ai))
        {
            return _do_split(mon, *ai);
        }
    }

    // No free squares.
    return false;
}

static void _starcursed_scream(monster* mon, actor* target)
{
    if (!target || !target->alive())
        return;

    //Gather the chorus
    vector<monster*> chorus;

    for (monster_near_iterator mi(target->pos(), LOS_NO_TRANS); mi; ++mi)
    {
        if (mi->type == MONS_STARCURSED_MASS)
            chorus.push_back(*mi);
    }

    int n = chorus.size();
    int dam = 0; int stun = 0;
    const char* message = nullptr;

    dprf("Chorus size: %d", n);

    if (n > 7)
    {
        message = "A cacophony of accursed wailing tears at your sanity!";
        if (coinflip())
            stun = 2;
    }
    else if (n > 4)
    {
        message = "A deafening chorus of shrieks assaults your mind!";
        if (one_chance_in(3))
            stun = 1;
    }
    else if (n > 1)
        message = "A chorus of shrieks assaults your mind.";
    else
        message = "The starcursed mass shrieks in your mind.";

    dam = 4 + random2(5) + random2(n * 3 / 2);

    if (!target->is_player())
    {
        if (you.see_cell(target->pos()))
        {
            mprf(target->as_monster()->friendly() ? MSGCH_FRIEND_SPELL
                                                  : MSGCH_MONSTER_SPELL,
                 "%s writhes in pain as voices assail %s mind.",
                 target->name(DESC_THE).c_str(),
                 target->pronoun(PRONOUN_POSSESSIVE).c_str());
        }
    }
    else
        mprf(MSGCH_MONSTER_SPELL, "%s", message);
    target->hurt(mon, dam, BEAM_MISSILE, KILLED_BY_BEAM, "",
                 "accursed screaming");

    if (stun && target->alive())
        target->paralyse(mon, stun, "accursed screaming");

    for (monster *voice : chorus)
        if (voice->alive())
            voice->add_ench(mon_enchant(ENCH_SCREAMED, voice, 1));
}

static bool _will_starcursed_scream(monster* mon)
{
    int n = 0;

    for (monster_near_iterator mi(mon->pos(), LOS_NO_TRANS); mi; ++mi)
    {
        if (mi->type != MONS_STARCURSED_MASS)
            continue;

        // Don't scream if any part of the chorus has a scream timeout
        // (This prevents it being staggered into a bunch of mini-screams)
        if (mi->has_ench(ENCH_SCREAMED))
            return false;
        else
            n++;
    }

    return one_chance_in(n);
}

/**
 * Can a lost soul revive the given monster, assuming one is nearby?
 *
 * @param mons      The monster potentially being revived.
 * @return          Whether it's a possible target for lost souls.
 */
static bool _lost_soul_affectable(const monster &mons)
{
    // zombies are boring
    if (mons_is_zombified(mons))
        return false;

    // undead can be reknit, naturals ghosted, everyone else is out of luck
    if (!(mons.holiness() & (MH_UNDEAD | MH_NATURAL)))
        return false;

    // already been revived once
    if (testbits(mons.flags, MF_SPECTRALISED))
        return false;

    // just silly
    if (mons.type == MONS_LOST_SOUL)
        return false;

    // for ely, I guess?
    if (is_good_god(mons.god))
        return false;

    if (mons.is_summoned())
        return false;

    if (!mons_class_gives_xp(mons.type))
        return false;

    return true;
}

// Is it worth sacrificing ourselves to revive this monster? This is based
// on monster HD, with a lower chance for weaker monsters so long as other
// monsters are present, but always true if there are only as many valid
// targets as nearby lost souls.
static bool _worthy_sacrifice(monster* soul, const monster* target)
{
    int count = 0;
    for (monster_near_iterator mi(soul, LOS_NO_TRANS); mi; ++mi)
    {
        if (_lost_soul_affectable(**mi))
            ++count;
        else if (mi->type == MONS_LOST_SOUL)
            --count;
    }

    const int target_hd = target->get_experience_level();
    return count <= -1 || target_hd > 9
           || x_chance_in_y(target_hd * target_hd * target_hd, 1200);
}

/**
 * Check to see if the given monster can be revived by lost souls (if it's a
 * valid target for revivication & if there are any lost souls nearby), and
 * revive it if so.
 *
 * @param mons  The monster in question.
 * @return      Whether the monster was revived/reknitted, or whether it
 *              remains dead (dying?).
 */
bool lost_soul_revive(monster& mons, killer_type killer)
{
    if (killer == KILL_RESET
        || killer == KILL_RESET_KEEP_ITEMS
        || killer == KILL_BANISHED)
    {
        return false;
    }

    if (!_lost_soul_affectable(mons))
        return false;

    for (monster_near_iterator mi(&mons, LOS_NO_TRANS); mi; ++mi)
    {
        if (mi->type != MONS_LOST_SOUL || !mons_aligned(&mons, *mi))
            continue;

        if (!_worthy_sacrifice(*mi, &mons))
            continue;

        // save this before we revive it
        const string revivee_name = mons.name(DESC_THE);
        const bool was_alive = bool(mons.holiness() & MH_NATURAL);

        // In this case the old monster will be replaced by
        // a ghostly version, so we should record defeat now.
        if (was_alive)
        {
            record_monster_defeat(&mons, killer);
            remove_unique_annotation(&mons);
        }

        targeter_radius hitfunc(*mi, LOS_SOLID);
        flash_view_delay(UA_MONSTER, GREEN, 200, &hitfunc);

        mons.heal(mons.max_hit_points);
        mons.timeout_enchantments();

        coord_def newpos = mi->pos();
        if (was_alive)
        {
            mons.move_to(newpos, MV_INTERNAL);
            mons.flags |= (MF_SPECTRALISED | MF_FAKE_UNDEAD);
        }

        // check if you can see the monster *after* it maybe moved
        if (you.can_see(mons))
        {
            if (!was_alive)
            {
                mprf("%s sacrifices itself to reknit %s!",
                     mi->name(DESC_THE).c_str(),
                     revivee_name.c_str());
            }
            else
            {
                mprf("%s assumes the form of %s%s!",
                     mi->name(DESC_THE).c_str(),
                     revivee_name.c_str(),
                     (mi->is_summoned() ? " and becomes anchored to this"
                      " world" : ""));
            }
        }

        if (mi->alive())
            monster_die(**mi, KILL_NON_ACTOR, -1, true);

        return true;
    }

    return false;
}

void treant_release_fauna(monster& mons)
{
    // FIXME: this should be a fineff, at least when called from monster_die.
    int count = mons.mangrove_pests;
    bool created = false;

    monster_type fauna_t = one_chance_in(4) ? MONS_RAVEN : MONS_HORNET;

    for (int i = 0; i < count; ++i)
    {
        mgen_data fauna_data(fauna_t, SAME_ATTITUDE(&mons),
                            mons.pos(),  mons.foe);
        fauna_data.extra_flags |= MF_WAS_IN_VIEW;
        fauna_data.copy_from_parent(&mons);

        if (create_monster(fauna_data))
        {
            created = true;
            mons.mangrove_pests--;
        }
    }

    if (created && you.can_see(mons))
    {
        if (fauna_t == MONS_RAVEN)
        {
            mprf("Jet-black ravens fly out from beneath %s foliage!",
                 mons.name(DESC_ITS).c_str());
        }
        else
        {
            mprf("Angry insects surge out from beneath %s foliage!",
                mons.name(DESC_ITS).c_str());
        }
    }
}

static bool _adj_to_tree(coord_def p)
{
    for (adjacent_iterator ai(p); ai; ++ai)
        if (feat_is_tree(env.grid(*ai)))
            return true;
    return false;
}

static coord_def _find_nearer_tree(coord_def cur_loc, coord_def target)
{
    coord_def p = {0, 0};
    int seen = 0;
    // don't bother teleporting to something that's at the same distance
    // from the target as you already are
    int closest = grid_distance(cur_loc, target) - 1;
    for (distance_iterator di(target); di; ++di)
    {
        const int dist = grid_distance(target, *di);
        if (dist > closest)
            break;

        if (!cell_see_cell(target, *di, LOS_NO_TRANS) // there might be a better iterator
            || !_adj_to_tree(*di)
            || !monster_habitable_grid(MONS_ELEIONOMA, *di))
        {
            continue;
        }
        // XXX: also check for dangerous clouds?

        closest = dist;

        seen++;
        if (x_chance_in_y(1, seen))
            p = *di;
    }
    return p;
}

static void _weeping_skull_cloud_aura(monster* mons)
{
    actor *foe = mons->get_foe();
    if (!foe || !mons->can_see(*foe))
        return;

    // Generate list of valid cloud spots.
    vector<coord_def> pos;

    for (radius_iterator ri(mons->pos(), LOS_NO_TRANS); ri; ++ri)
    {
        if (grid_distance(mons->pos(), *ri) > 2)
            continue;

        if (!feat_is_solid(env.grid(*ri)) && !actor_at(*ri) && !cloud_at(*ri))
            pos.push_back(*ri);
    }

    shuffle_array(pos);

    int num_clouds = min((int)pos.size(), random_range(1, 3));
    for (int i = 0; i < num_clouds; ++i)
        place_cloud(CLOUD_MISERY, pos[i], random2(3) + 2, mons);
}

void seismosaurus_egg_hatch(monster* mons)
{
    mon_enchant hatch = mons->get_ench(ENCH_HATCHING);
    hatch.duration -= 1;

    if (hatch.duration  == 4)
    {
        simple_monster_message(*mons, " cracks slightly.");
        mons->number = 1;
    }
    else if (hatch.duration  == 2)
    {
        simple_monster_message(*mons, " shakes eagerly.");
        mons->number = 2;
    }
    // Hatching time!
    else if (hatch.duration  == 0)
    {
        simple_monster_message(*mons, " hatches with a roar like a landslide!",
                                false, MSGCH_MONSTER_SPELL);

        const int old_hd = mons->get_experience_level();
        change_monster_type(mons, MONS_SEISMOSAURUS, true);
        mons->heal(mons->max_hit_points);
        mons->set_hit_dice(old_hd);

        mon_enchant timer = mons->get_ench(ENCH_SUMMON_TIMER);
        timer.duration = random_range(40, 55) * BASELINE_DELAY;
        mons->update_ench(timer);
        mons->del_ench(ENCH_HATCHING);

        // Immediately stomp if anything is in range
        mons->speed_increment = 80;
        try_mons_cast(*mons, SPELL_SEISMIC_STOMP);
        queue_monster_for_action(mons);

        // Clean up range indicator
        for (distance_iterator di(mons->pos(), false, false, 4); di; ++di)
            env.pgrid(*di) &= ~FPROP_SEISMOROCK;

        return;
    }

    mons->update_ench(hatch);
}

// Attempt to merge with any nearby aligned slime creatures
static bool _slymdra_try_merge(monster* mons)
{
    int did_merge = 0;
    const int old_heads = mons->num_heads;
    int new_heads = old_heads;
    for (adjacent_iterator ai(mons->pos()); ai; ++ai)
    {
        if (monster* mon_at = monster_at(*ai))
        {
            if (mon_at->type == MONS_SLIME_CREATURE
                && mons_aligned(mons, mon_at))
            {
                const int extra_heads = mon_at->blob_size;

                // Don't absorb more heads than we can handle.
                if (new_heads + extra_heads > 20)
                    continue;

                if (mon_at->is_unrewarding() || mon_at->is_summoned())
                    mons->props[SLYMDRA_FAKE_HEADS_KEY].get_int() += extra_heads;
                else
                    mons->props[SLYMDRA_SLIMES_EATEN_KEY].get_int() += extra_heads;

                new_heads += extra_heads;
                merge_ench_durations(*mon_at, *mons);
                monster_die(*mon_at, KILL_RESET, NON_MONSTER);

                ++did_merge;
            }
        }
    }

    if (did_merge > 0)
    {
        if (you.see_cell(mons->pos()))
        {
            flash_tile(mons->pos(), LIGHTGREEN);
            const int gained_heads = new_heads - old_heads;
            const string head_msg = gained_heads == 1 ? "sprouts a new head"
                                                      : make_stringf("sprouts %d new heads", gained_heads);
            if (did_merge > 1)
            {
                mprf("%s absorbs %d nearby slime creatures and %s.",
                        mons->name(DESC_THE).c_str(), did_merge, head_msg.c_str());
            }
            else
            {
                mprf("%s absorbs a nearby slime creature and %s.",
                        mons->name(DESC_THE).c_str(), head_msg.c_str());
            }
        }
        mons->num_heads = new_heads;
        slymdra_scale_hp(*mons);
        return true;
    }

    return false;
}

static bool _slymdra_split_or_merge(monster* mons)
{
    const actor* foe = mons->get_foe();
    if (mons->behaviour == BEH_SEEK
        && foe && mons->see_cell_no_trans(foe->pos()) && coinflip())
    {
        return _slymdra_try_merge(mons);
    }
    else if (mons->num_heads > 4
             && (!foe || !mons->see_cell(foe->pos())) && one_chance_in(10))
    {
        return slymdra_split(*mons, 1);
    }

    return false;
}

static inline void _mons_cast_abil(monster* mons, bolt &pbolt,
                                   spell_type spell_cast)
{
    mons_cast(mons, pbolt, spell_cast, MON_SPELL_NATURAL);
}

bool mon_special_ability(monster* mons)
{
    bool used = false;

    const monster_type mclass = (mons_genus(mons->type) == MONS_DRACONIAN)
                                  ? draconian_subspecies(*mons)
                                  : mons->type;

    // Slime creatures can split while out of sight.
    if ((!mons->near_foe() || mons->asleep())
         && !(mons->type == MONS_SLIME_CREATURE
              || mons->type == MONS_SLYMDRA))
    {
        return false;
    }

    switch (mclass)
    {
    case MONS_UGLY_THING:
    case MONS_VERY_UGLY_THING:
        // A (very) ugly thing may mutate if it's next to other ones (or
        // next to you if you're contaminated).
        used = ugly_thing_mutate(*mons, false);
        break;

    case MONS_SLIME_CREATURE:
        // Slime creatures may split or merge depending on the
        // situation.
        used = _slime_split_merge(mons);
        if (!mons->alive())
            return true;
        break;

    case MONS_SLYMDRA:
        used = _slymdra_split_or_merge(mons);
        break;

    case MONS_BALL_LIGHTNING:
        if (mons->attitude == ATT_HOSTILE
            && grid_distance(you.pos(), mons->pos()) <= 2)
        {
            mons->suicide();
            used = true;
            break;
        }

        for (monster_near_iterator targ(mons, LOS_NO_TRANS); targ; ++targ)
        {
            if (mons_aligned(mons, *targ) || targ->is_firewood()
                || grid_distance(mons->pos(), targ->pos()) > 2
                || !you.see_cell(targ->pos()))
            {
                continue;
            }

            mons->suicide();
            used = true;
            break;
        }
        break;

    case MONS_FOXFIRE:
    case MONS_SHOOTING_STAR:
        if (mons->attitude == ATT_HOSTILE
            && grid_distance(you.pos(), mons->pos()) == 1)
        {
            seeker_attack(*mons, you);
            used = true;
            break;
        }

        for (monster_near_iterator targ(mons, LOS_NO_TRANS); targ; ++targ)
        {
            if (mons_aligned(mons, *targ) || targ->is_firewood()
                || grid_distance(mons->pos(), targ->pos()) > 1
                || (mons->friendly() && !you.see_cell(targ->pos())))
            {
                continue;
            }

            seeker_attack(*mons, **targ);
            used = true;
            break;
        }
        break;

    case MONS_STARCURSED_MASS:
        if (x_chance_in_y(mons->blob_size,8) && x_chance_in_y(2,3)
            && mons->hit_points >= 8)
        {
            _starcursed_split(mons), used = true;
        }

        if (!mons_is_confused(*mons)
            && could_harm(mons, actor_at(mons->target))
            && _will_starcursed_scream(mons)
            && coinflip())
        {
            _starcursed_scream(mons, actor_at(mons->target));
            used = true;
        }
        break;

    case MONS_THORN_HUNTER:
    {
        // If we would try to move into a briar (that we might have just created
        // defensively), let's see if we can shoot our foe through it instead
        if (actor_at(mons->pos() + mons->props[MMOV_KEY].get_coord())
            && actor_at(mons->pos() + mons->props[MMOV_KEY].get_coord())->type == MONS_BRIAR_PATCH
            && !one_chance_in(3))
        {
            actor *foe = mons->get_foe();
            if (foe && mons->can_see(*foe))
            {
                bolt beem = setup_targeting_beam(*mons);
                beem.target = foe->pos();
                setup_mons_cast(mons, beem, SPELL_THORN_VOLLEY);

                targeting_tracer tracer;
                fire_tracer(mons, tracer, beem);
                if (mons_should_fire(beem, tracer))
                {
                    make_mons_stop_fleeing(mons);
                    _mons_cast_abil(mons, beem, SPELL_THORN_VOLLEY);
                    used = true;
                }
            }
        }
        // Otherwise, if our foe is approaching us, we might want to raise a
        // defensive wall of brambles (use the number of brambles in the area
        // as some indication if we've already done this, and shouldn't repeat)
        else if (mons->props[FOE_APPROACHING_KEY].get_bool() == true
                 && !mons_is_confused(*mons)
                 && coinflip())
        {
            int briar_count = 0;
            for (monster_near_iterator mi(mons, LOS_NO_TRANS); mi; ++mi)
            {
                if (mi->type == MONS_BRIAR_PATCH
                    && grid_distance(mons->pos(), mi->pos()) > 3)
                {
                    briar_count++;
                }
            }
            if (briar_count < 4) // Probably no solid wall here
            {
                bolt beem; // unused
                _mons_cast_abil(mons, beem, SPELL_WALL_OF_BRAMBLES);
                used = true;
            }
        }
    }
    break;

    case MONS_WATER_NYMPH:
    case MONS_NORRIS:
    {
        if (!one_chance_in(5))
            break;

        actor *foe = mons->get_foe();
        if (!foe || !mons->can_see(*foe) || feat_is_water(env.grid(foe->pos())))
            break;

        const coord_def targ = foe->pos();
        coord_def spot;
        if (!find_habitable_spot_near(targ, MONS_ELECTRIC_EEL, 3, spot)
            || targ.distance_from(spot) >= targ.distance_from(mons->pos()))
        {
            break;
        }

        if (mons->move_to(spot, MV_DELIBERATE | MV_TRANSLOCATION, true))
        {
            simple_monster_message(*mons, " flows with the water.");
            mons->finalise_movement();
            used = true;
        }
    }
    break;

    case MONS_ELEIONOMA:
    {
        if (!one_chance_in(3))
            break;

        actor *foe = mons->get_foe();
        if (!foe || !mons->can_see(*foe))
            break;

        const int dist = grid_distance(foe->pos(), mons->pos());
        if (dist < 3)
            break;

        const coord_def target = _find_nearer_tree(mons->pos(), foe->pos());
        if (target.origin() || !mons->move_to(target, MV_DELIBERATE | MV_TRANSLOCATION, true))
            break;

        simple_monster_message(*mons, " flows through the trees.");
        mons->finalise_movement();
        used = true;
    }
    break;

    case MONS_SHAMBLING_MANGROVE:
    {
        if (mons->hit_points * 2 < mons->max_hit_points
            && mons->mangrove_pests > 0)
        {
            treant_release_fauna(*mons);
            // Intentionally takes no energy; the creatures are flying free
            // on their own time.
        }
    }
    break;

    case MONS_WEEPING_SKULL:
        _weeping_skull_cloud_aura(mons);
        break;

    case MONS_CLOCKWORK_BEE_INACTIVE:
    {
        // Note: the player is not a monster, so this will never happen to them.
        monster* summ = monster_by_mid(mons->summoner);
        if (summ && adjacent(summ->pos(), mons->pos()) && !summ->incapacitated()
            && summ->has_action_energy() && !one_chance_in(4))
        {
            if (clockwork_bee_recharge(*summ, *mons))
                summ->lose_energy(EUT_MOVE);
        }
        break;
    }

    case MONS_NAMELESS_REVENANT:
        // If we are engaging the player and have full memories, burn one fairly
        // immediately.
        if (mons->foe == MHITYOU && mons->can_see(you)
            && mons->props[NOBODY_MEMORIES_KEY].get_vector().size() == NOBODY_MAX_MEMORIES
            && one_chance_in(3))
        {
            pyrrhic_recollection(*mons);
            used = true;
        }

        break;

    default:
        break;
    }

    if (used)
        mons->lose_energy(EUT_SPECIAL);

    return used;
}

bool egg_is_incubating(const monster& egg)
{
    if (!egg.has_ench(ENCH_HATCHING))
        return false;

    mon_enchant hatch = egg.get_ench(ENCH_HATCHING);

    // Check if we're near our 'parent'
    const actor* parent = hatch.agent();
    if (!parent || !adjacent(parent->pos(), egg.pos()))
        return false;

    // Finally, check that there are foes sufficiently nearby (and in the
    // parent's LoS)
    for (monster_near_iterator mi(parent, LOS_NO_TRANS); mi; ++mi)
    {
        if (!mons_aligned(*mi, &egg) && !mi->is_firewood()
            && grid_distance(egg.pos(), mi->pos()) <= 4)
        {
            return true;
        }
    }

    return false;
}

struct nobody_recollection
{
    int weight;
    string key;
    vector<pair<spell_type, uint8_t>> spells;
};

const static vector<nobody_recollection> _recollections =
{
    {50, "fire", {{SPELL_MARSHLIGHT, 40}, {SPELL_SCORCH, 50}}},
    {50, "fire", {{SPELL_PYRE_ARROW, 80}}},
    {50, "cold", {{SPELL_OZOCUBUS_REFRIGERATION, 80}}},
    {50, "cold", {{SPELL_PERMAFROST_ERUPTION, 80}}},
    {50, "poison", {{SPELL_CORROSIVE_BOLT, 80}}},
    {50, "poison", {{SPELL_HURL_SLUDGE, 100}}},
    {50, "poison", {{SPELL_IRRADIATE, 75}}},
    {65, "undead", {{SPELL_BORGNJORS_VILE_CLUTCH, 120}}},
    {80, "fear", {{SPELL_CAUSE_FEAR, 120}, {SPELL_GHOSTLY_FIREBALL, 50}}},
    {80, "soldiers", {{SPELL_BATTLESPHERE, 120}, {SPELL_BOMBARD, 60}}},
    {50, "rockslide", {{SPELL_LRD, 100}}},
    {50, "electricity", {{SPELL_ARCJOLT, 80}}},

    {75, "xxx", {{SPELL_SUMMON_HORRIBLE_THINGS, 70}}},
    {85, "demons", {{SPELL_SUMMON_GREATER_DEMON, 70}}},
    {85, "undead", {{SPELL_HAUNT, 70}}},
    {110, "vermin", {{SPELL_SUMMON_VERMIN, 70}}},

    {180, "soldiers", {{SPELL_HASTE, 75}, {SPELL_MIGHT, 75}}},
};

// Initialize a set of 3 random spellsets for Nobody, guaranteed to all be
// different from each other. (Called upon Nobody spawning or so much time
// passing that they regenerate their memories.)
void initialize_nobody_memories(monster& nobody)
{
    CrawlVector& memories = nobody.props[NOBODY_MEMORIES_KEY].get_vector();
    memories.clear();

    vector<pair<int, int>> weights;
    for (size_t i = 0; i < _recollections.size(); ++i)
        weights.push_back({i, _recollections[i].weight});

    for (int i = 0; i < NOBODY_MAX_MEMORIES; ++i)
    {
        const int index = *random_choose_weighted(weights);
        memories.push_back(index);
        weights[index].second = 0;
    }
}

bool pyrrhic_recollection(monster& nobody)
{
    CrawlVector& memories = nobody.props[NOBODY_MEMORIES_KEY].get_vector();
    if (memories.size() <= 0)
        return false;

    const bool can_see = you.see_cell(nobody.pos());
    const bool was_injured = nobody.hit_points < nobody.max_hit_points;

    if (can_see)
        draw_ring_animation(nobody.pos(), 3, LIGHTCYAN, CYAN, true);

    // Change spells
    nobody.spells.clear();
    const auto& recollection = _recollections[memories[memories.size() - 1].get_int()];

    vector<string> spell_names;
    for (pair<spell_type, uint8_t> spell : recollection.spells)
    {
        nobody.spells.push_back({spell.first, spell.second, MON_SPELL_WIZARD});
        spell_names.push_back(spell_title(spell.first));
    }
    nobody.spells.push_back({SPELL_PYRRHIC_RECOLLECTION, 0, MON_SPELL_NATURAL});
    nobody.props[CUSTOM_SPELLS_KEY] = true;
    memories.pop_back();

    if (can_see)
    {
        mprf(MSGCH_MONSTER_SPELL, "%s ignites a memory of %s%s.",
                nobody.name(DESC_THE).c_str(),
                comma_separated_line(spell_names.begin(), spell_names.end()).c_str(),
                was_injured ? " to re-knit themselves" : "");
        string speech = make_stringf("\"We remember... %s...\"",
                            getSpeakString("nobody_recollection " + recollection.key).c_str());
        mons_speaks_msg(&nobody, speech, MSGCH_TALK);
    }

    // Heal and move.
    if (was_injured)
        monster_blink(&nobody, true, true);
    nobody.heal(nobody.max_hit_points);

    // If this was a phantom mirror copy, allow it to revive, but don't wipe out
    // its summon timer at the same time, to keep it from having unlimited duration.
    mon_enchant summon_timer;
    if (nobody.has_ench(ENCH_SUMMON_TIMER))
    {
        summon_timer = nobody.get_ench(ENCH_SUMMON_TIMER);
        nobody.del_ench(ENCH_SUMMON_TIMER, true, false);
    }
    // Also, manually delete the previous enkindle without effect, in case
    // Nobody's taken a big enough hit to go from healthy to dead in one action,
    // or we'll immediately wipe out the spells we just gave them.
    nobody.del_ench(ENCH_PYRRHIC_RECOLLECTION, true, false);
    // XXX: Also save their Haste and Might, since the *point* of that spellset
    // is that the effects can linger into other phases. It would really be
    // nice if there was a general 'clear *negative* status effects on a monster,
    // but we don't have that at the moment.
    mon_enchant haste = nobody.get_ench(ENCH_HASTE);
    mon_enchant might = nobody.get_ench(ENCH_MIGHT);
    nobody.timeout_enchantments();
    nobody.add_ench(summon_timer);
    nobody.add_ench(haste);
    nobody.add_ench(might);

    nobody.add_ench(mon_enchant(ENCH_PYRRHIC_RECOLLECTION, &nobody, random_range(300, 500)));

    // Don't immediately expire summons (we want them to stick around into the next phase),
    // but at least make them time out a bit faster.
    for (monster_iterator mi; mi; ++mi)
    {
        if (mi->was_created_by(nobody))
        {
            mon_enchant timer = mi->get_ench(ENCH_SUMMON_TIMER);
            timer.duration = timer.duration / 3;
            mi->update_ench(timer);
        }
    }

    nobody.props[NOBODY_RECOVERY_KEY] = you.elapsed_time + (random_range(300, 500));

    // Allow Nobody to wake up if you kill them in their sleep
    behaviour_event(&nobody, ME_ALERT);

    schedule_avoided_death_fineff(&nobody);

    return true;
}

// AoE attack when the player attacks in scarab form
void solar_ember_blast()
{
    monster* ember = get_solar_ember();
    if (!ember)
        return;

    if (!ember->has_ench(ENCH_SPELL_CHARGED))
    {
        simple_monster_message(*ember, " glows brighter.");
        ember->add_ench(mon_enchant(ENCH_SPELL_CHARGED, ember, random_range(70, 90)));
        you.did_trigger(DID_SOLAR_EMBER);
        return;
    }

    vector<monster*> targs;
    for (adjacent_iterator ai(ember->pos()); ai; ++ai)
        if (monster* mon = monster_at(*ai))
            if (could_harm_enemy(&you, mon) && !mon->is_firewood() && you.see_cell_no_trans(mon->pos()))
                targs.push_back(mon);

    if (targs.empty())
        return;

    simple_monster_message(*ember, " blazes with a fierce heat.", false, MSGCH_FRIEND_SPELL);

    bolt beam;
    beam.flavour = BEAM_FIRE;
    dice_def dmg = get_form()->get_special_damage();
    for (monster* mon : targs)
    {
        if (!mon->alive())
            continue;

        flash_tile(mon->pos(), RED, 0);
        const int damage_done = mons_adjust_flavoured(mon, beam, mon->apply_ac(dmg.roll()));
        mprf("The solar flare engulfs %s%s.", mon->name(DESC_THE).c_str(),
                damage_done ? "" : " but does no damage");
        mon->hurt(ember, damage_done, BEAM_FIRE);
    }

    animation_delay(10, true);

    ember->hurt(ember, random_range(7, 10));
    ember->del_ench(ENCH_SPELL_CHARGED);

    you.did_trigger(DID_SOLAR_EMBER);
}

static bool _make_tesseract_spawn(bool near_player, bool outside_vault = false)
{
    mgen_data mg(one_chance_in(6) ? MONS_ORB_GUARDIAN : WANDERING_MONSTER);
    mg.place = level_id::current();
    mg.place.depth = 7;
    mg.flags |= MG_FORBID_BANDS;
    mg.extra_flags |= (MF_HARD_RESET | MF_TESSERACT_SPAWN);
    mg.foe = MHITYOU;
    mg.non_actor_summoner = "a Boundless Tesseract";
    mg.proximity = near_player ? PROX_CLOSE_TO_PLAYER
                               : PROX_AWAY_FROM_PLAYER;

    if (outside_vault)
    {
        int tries = 500;
        while (--tries > 0)
        {
            coord_def pos = random_in_bounds();
            if (!monster_habitable_grid(mg.cls, pos))
                continue;

            const vault_placement *vp = dgn_vault_at(pos);
            if (!(vp && vp->map_name_at(pos) == "hall_of_Zot"))
            {
                mg.pos = pos;
                mg.flags |= MG_FORCE_PLACE;
                break;
            }
        }

        if (tries <= 0)
            return false;
    }

    return mons_place(mg);
}

void activate_tesseracts()
{
    if (you.props.exists(TESSERACT_SPAWN_COUNTER_KEY))
        return;

    bool did_activate = false;
    for (monster_iterator mi; mi; ++mi)
    {
        if (mi->type != MONS_BOUNDLESS_TESSERACT)
            continue;

        if (!did_activate)
        {
            mprf(MSGCH_WARN, "You feel the power of Zot begin to gather its forces!");
            take_note(Note(NOTE_TESSERACT_ACTIVATED));
            mark_milestone("tesseract.activate", "activated a tesseract");
            // Tracked on the player instead of the monster so status lookup is quicker.
            you.props[TESSERACT_SPAWN_COUNTER_KEY] = 0;
            mi->props[TESSERACT_SPAWN_TIMER_KEY] = you.elapsed_time;

            // Remove patrolling from everything but Orb guardians.
            for (monster_iterator mi2; mi2; ++mi2)
                if (mi2->type != MONS_ORB_GUARDIAN && !mi2->friendly())
                    mi2->patrol_point.reset();

            tesseract_action(**mi);
            did_activate = true;

            // Spawn several monsters outside the orb vault immediately.
            const int num = random_range(4, 7);
            for (int i = 0; i < num; ++i)
                _make_tesseract_spawn(false, true);
        }

        behaviour_event(*mi, ME_ALERT);
        env.map_knowledge(mi->pos()).set_monster(monster_info(*mi));
        set_terrain_seen(mi->pos());
        view_update_at(mi->pos());
#ifdef USE_TILE
        tiles.update_minimap(mi->pos());
#endif
    }
}

void tesseract_action(monster& mon)
{
    // Only operate logic on a single tesseract on the floor
    if (!mon.props.exists(TESSERACT_SPAWN_TIMER_KEY))
        return;

    // Handle regular spawning
    int& timer = mon.props[TESSERACT_SPAWN_TIMER_KEY].get_int();
    int& count = you.props[TESSERACT_SPAWN_COUNTER_KEY].get_int();

    // Don't act as if more than 500 turns have passed off-level. (It only runs
    // off-level at all to prevent it being correct to return to Zot:4 every
    // time you want to rest, and this is hopefully long enough to cover those
    // situations.)
    if (you.elapsed_time - timer > 5000)
        timer = you.elapsed_time - 5000;

    // Exit early if it's not yet time to spawn things.
    if (you.elapsed_time < timer)
        return;

    // Count number of both tesseract spawns and remaining non-tesseract
    // monsters on the floor.
    int spawn_count = 0;
    int non_spawn_count = 0;
    for (monster_iterator mi; mi; ++mi)
    {
        if (mi->flags & MF_TESSERACT_SPAWN)
            ++spawn_count;
        else if (!mi->is_summoned() && !mi->is_peripheral() && !mi->wont_attack())
            ++non_spawn_count;
    }

    // Cap number of tesseract spawns at 60, and total number of monsters on the
    // floor at 100 (which is above the average starting monster count, but not
    // the *maximum* starting monster count).
    int allowed = min(60 - spawn_count, 100 - spawn_count - non_spawn_count);

    // Catch up however many spawns should have happened since the last time
    // we activated.
    while (you.elapsed_time >= timer && allowed > 0)
    {
        // Spawn a monster every ~50 turns.
        timer += random_range(350, 650);

        if (!_make_tesseract_spawn(count >= 50 && coinflip()))
            break;

        --allowed;
        ++count;
    }
}