// Auto-attack: once the hero attacked or cast an art at an enemy, it keeps
// attacking that enemy with its weapon whenever it would stand idle.
//
// A left click on a creature sends the hero one attack order (cEvent_creature
// 7, target id at +0x18, its position at +0x1c / +0x20); the hero swings once
// and stands again (+0x150 back to 0x10000). Arts are orders 0x105 with the
// target at +0x10. Both are seen in cCreature::ReceiveOrder; their target
// becomes the hero's combat target if it is a living creature and not an ally.
// Every engine tick in which the hero is idle, no mouse button and no skill
// key is held, the attack order a left click sends goes to the target again.
// A walk order (mouse move, WASD, stop) ends it. When the target dies the
// hero takes the nearest enemy within close range (weapon reach and a step).
// After an art: a melee art (the hero walked up to cast it, or casts it from
// close by) always leads to auto-attacking (its target, else the nearest
// enemy close by); a ranged art (cast from beyond close range) only with a
// ranged weapon, or with a melee weapon when an enemy is in melee range. Which arts are ranged is seen when the hero starts them and
// remembered per art. User requests of 2026-10-16.
// Between swings the hero does not go idle at all: the end-of-swing check for
// a held mouse button is answered "held" for the auto-attack target.
// Measured with an order log, see docs/auto-attack.md.

#include <atomic>
#include <cstdint>
#include <unordered_map>

#include <windows.h>

#include "game/engine/arts.h"
#include "game/engine/events.h"
#include "game/engine/objects.h"
#include "game/engine/orders.h"
#include "mods/skillkeys.h"
#include "re/hook.h"
#include "re/patch.h"

namespace mods::autoattack {
namespace {

// After an attack order, wait this many ticks for the hero to start it before
// sending another one (it takes about 2 ticks).
constexpr int kStartTicks = 5;
// "Close range": where the hero touches a creature (game::ContactDistance,
// heroes swing from 117..149) plus a step.
constexpr int kStep = 100;
// TODO(measure): the reach of ranged weapons (no ranged hero measured yet).
constexpr int kRangedWeaponReach = 600;
// An art order that has not started after this long is forgotten.
constexpr DWORD kCastStartMs = 5000;

std::atomic<uint32_t> g_target{0};
int g_waitTicks = 0;

// The hero's last art order until the hero starts it.
struct CastWatch {
    uint16_t art = 0;
    uint32_t target = 0;  // an enemy, or 0
    bool walked = false;
    DWORD since = 0;
};
CastWatch g_cast;
std::unordered_map<uint16_t, bool> g_artRanged;

bool IsEnemy(void* hero, uint32_t id) {
    if (id == 0 || id == static_cast<uint32_t>(game::CreatureField(hero, game::kCreatureId))) {
        return false;
    }
    return game::IsHostileTo(hero, game::GetCreature(id));
}

bool Idle(void* creature) {
    return game::CurrentAction(creature) == game::kActionIdle;
}

// How far the hero looks for its next target.
double CloseRange(void* hero) {
    if (game::HasRangedWeapon(hero)) {
        return kRangedWeaponReach;
    }
    return game::ContactDistance(hero, hero) + kStep;
}

uint32_t NearestCloseEnemy(void* hero, uint32_t except) {
    return game::NearestHostile(hero, hero, CloseRange(hero), except);
}

// The hero started the watched art: decide what it auto-attacks afterwards.
void OnCastStarted(void* hero) {
    const CastWatch cast = g_cast;
    g_cast = {};
    void* target = cast.target ? game::GetCreature(cast.target) : nullptr;
    bool ranged = false;
    if (cast.walked) {
        g_artRanged[cast.art] = false;
    } else if (target && static_cast<int>(game::DistanceTo(hero, cast.target)) >
                             game::ContactDistance(hero, target) + kStep) {
        g_artRanged[cast.art] = ranged = true;
    } else {
        const auto known = g_artRanged.find(cast.art);
        ranged = known != g_artRanged.end() && known->second;
    }
    if (ranged && !game::HasRangedWeapon(hero)) {
        // A ranged art with a melee weapon: auto-attack only what is in melee
        // range already (its target if that close, else the nearest enemy).
        const bool targetClose = target && game::DistanceTo(hero, cast.target) <= CloseRange(hero);
        g_target = targetClose ? cast.target : NearestCloseEnemy(hero, 0);
        return;
    }
    g_target = target ? cast.target : NearestCloseEnemy(hero, 0);
}

void WatchCast(void* hero) {
    if (!g_cast.since) {
        return;
    }
    if (GetTickCount() - g_cast.since > kCastStartMs) {
        g_cast = {};
        return;
    }
    switch (game::CurrentAction(hero)) {
    case game::kActionWalk:
        g_cast.walked = true;
        break;
    case game::kActionCastSpell:
    case game::kActionCombatMove:
        OnCastStarted(hero);
        break;
    default:
        break;
    }
}

void OnTick(uint8_t* engine) {
    void* hero = game::ControlledCreature(engine);
    if (!hero) {
        g_target = 0;
        return;
    }
    WatchCast(hero);
    if (g_cast.since) {
        return;  // the art decides once it starts
    }
    uint32_t id = g_target.load();
    if (!id) {
        return;
    }
    void* target = game::GetCreature(id);
    if (!target || !game::IsAlive(target)) {
        id = NearestCloseEnemy(hero, id);
        g_target = id;
        target = id ? game::GetCreature(id) : nullptr;
        if (!target) {
            return;
        }
    }
    if (!Idle(hero)) {
        g_waitTicks = 0;
        return;
    }
    const uint32_t flags = *reinterpret_cast<uint32_t*>(engine + game::kEngineFlags);
    if (g_waitTicks > 0 && --g_waitTicks > 0) {
        return;
    }
    if ((flags & 0x4010) != 0 || mods::skillkeys::KeyHeld()) {
        return;  // mouse button held / input blocked / a skill key casts
    }
    game::CreatureOrder order;
    order.command = game::kOrderAttack;
    order.a = static_cast<int32_t>(id);
    order.b = game::CreatureField(target, game::kCreatureX);
    order.c = game::CreatureField(target, game::kCreatureY);
    game::SendCreatureOrder(engine, hero, order);
    g_waitTicks = kStartTicks;
}

struct Registration {
    Registration() { game::OnEngineTick(&OnTick); }
} g_registration;

// The end of a swing (0x4e6584, after the hit) asks the mouse cursor whether
// the left button is still held (cMouseCursor::IsButtonHeld, call at
// 0x4e65c6; attacker in esi, target creature in ebp): if so the attacker
// swings again right away, otherwise it recovers (+0x152 = 2) and stands.
// While the hero auto-attacks its target, the answer is yes, so swings follow
// each other at the speed of a held button.
constexpr uint32_t kSwingEndButtonCheck = 0x004e65c6;
constexpr uint32_t kIsButtonHeld = 0x00655ab0;

char __fastcall SwingContinues(void* cursor, void*, void* attacker, void* target) {
    using IsButtonHeldFn = char(__fastcall*)(void*, void*);
    if (reinterpret_cast<IsButtonHeldFn>(kIsButtonHeld)(cursor, nullptr)) {
        return 1;
    }
    const uint32_t id = g_target.load();
    void* hero = game::GetPlayerHero();
    const uint32_t targetId = target ? static_cast<uint32_t>(game::CreatureField(target, game::kCreatureId)) : 0;
    if (!id || !target || attacker != hero || mods::skillkeys::KeyHeld() || targetId != id) {
        return 0;
    }
    return game::IsAlive(target) ? 1 : 0;
}

// Called instead of IsButtonHeld (ecx = the cursor, attacker in esi, target
// in ebp).
__declspec(naked) void SwingContinuesThunk() {
    __asm {
        push ebp
        push esi
        call SwingContinues
        ret
    }
}

// During a swing the attack code also checks the button (call at 0x4e7101)
// and clears the global "attack held" flag (0xab6030) when it is up; the swing
// end only chains while that flag is set (0x4e6641). The flag exists for the
// local player only, so the answer is "held" whenever the hero auto-attacks.
constexpr uint32_t kSwingButtonCheck = 0x004e7101;

char __fastcall AttackHeld(void* cursor, void*) {
    using IsButtonHeldFn = char(__fastcall*)(void*, void*);
    if (reinterpret_cast<IsButtonHeldFn>(kIsButtonHeld)(cursor, nullptr)) {
        return 1;
    }
    const uint32_t id = g_target.load();
    void* hero = game::GetPlayerHero();
    if (!id || !hero || mods::skillkeys::KeyHeld() ||
        game::CurrentAction(hero) != game::kActionAttack) {
        return 0;
    }
    void* target = game::GetCreature(id);
    return target && game::IsAlive(target) ? 1 : 0;
}

void Startup() {
    re::RedirectCall(kSwingEndButtonCheck, kIsButtonHeld, reinterpret_cast<const void*>(&SwingContinuesThunk));
    re::RedirectCall(kSwingButtonCheck, kIsButtonHeld, reinterpret_cast<const void*>(&AttackHeld));
}
RE_STARTUP(AutoAttackStartup, Startup);

} // namespace

namespace {

// An order for the player's hero.
void OnOrder(void* creature, const game::CreatureOrder& order, void*) {
    void* hero = game::GetPlayerHero();
    if (creature != hero) {
        return;
    }
    switch (order.command) {
    case game::kOrderWalk:
        g_target = 0;
        break;
    case game::kOrderAttack:
        if (IsEnemy(hero, static_cast<uint32_t>(order.a))) {
            g_target = static_cast<uint32_t>(order.a);
        }
        break;
    case game::kOrderUseArt: {
        // Buffs and the like (aimed at the hero or an ally) leave the target.
        const auto launch = game::ArtLaunchType(static_cast<uint16_t>(order.art));
        if (launch == game::LaunchType::SelfOrAlly || launch == game::LaunchType::Corpse) {
            break;
        }
        g_cast = {static_cast<uint16_t>(order.art), IsEnemy(hero, order.target) ? order.target : 0u, false,
                  GetTickCount()};
        break;
    }
    }
}

struct OrderRegistration {
    OrderRegistration() { game::OnCreatureOrder(&OnOrder); }
} g_orderRegistration;

} // namespace

} // namespace mods::autoattack