// The dwarf's Kanonenschuss (0x43f) and Mörsergranate (0x43e) (request of
// 2026-10-25, docs/dwarf-arts.md).
//
// Kanonenschuss: "remove the knockback, instead it can be just a stun". On a
// successful stun roll the dwarf's combat move code (0x5145d0, case 0x43f)
// plays MOTION_HIT_A on the target (0x5936e0 at 0x517709) and sends it the
// stun order (cEvent_creature 3 from 0x5177aa, +0x14 = 100). The game's stun
// is a push (measured: about 100 units away from the attacker in 0.3 s): the
// order sets creature flag 0x20000, the push left (+0x24d) and the attacker
// (+0x259); while the flag is set, cCreature::Update (branch 0x594c82) skips
// everything else and moves the creature away from the attacker, lowering
// the push left by each step, and clears the flag at 0. The mod skips the
// motion, and for creatures the cannon stunned the push step (0x594deb)
// moves them by 0 and keeps the push left above 0 for kStunMs: they stand
// still, doing nothing, then carry on. The shot's ray (25 steps of 40 = 1000) gets 45 steps (1800),
// for the widened view ("range needs to be increased to accommodate for the
// increased viewport", 2026-10-26).
//
// Mörsergranate: "the radius of the explosion should increase every 5 skill
// levels". The grenade (type 0x3fa) creates an impact object
// (TYPE_FX_GRENADEIMPACT, 0x3fc) where it lands; that object gathers its
// targets with cObjectManager 0x5ff820 (called from 0x5ab400 at 0x5ab63d): a
// creature is hit when its distance is below the impact type's size (150)
// plus the creature type's size (object type table 0x428bb0). The mod passes
// that call a radius of size × (1 + kRadiusGrowth × (level / 5)), with the
// level of the owner's Mörsergranate.
//
// Impact marker (asked 2026-10-25): where the grenade will land and its
// explosion radius, a red circle with low alpha on the ground. The landing
// point is decided at launch (0x5145d0 case 0x43e: the target's position, or
// 200 units from the dwarf with +-15 jitter when closer) and sent to the new
// grenade with cEventFX 0x96 (constructed at 0x5169fa: code, owner, 0,
// position area / x / y / level). The construct call notes the grenade and
// the point; the circle is drawn after the world view's ground (0x62d530,
// before the objects) until the impact gathers its targets (the grenade
// object itself stays about 30 s longer).

#include <windows.h>

#include <cstdint>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <vector>

#include "game/engine/art.h"
#include "game/engine/arts.h"
#include "game/engine/objects.h"
#include "game/engine/orders.h"
#include "game/engine/worldview.h"
#include "game/ui/draw.h"
#include "mods/widescreen.h"
#include "re/hook.h"
#include "re/log.h"
#include "re/patch.h"

namespace mods::dwarfarts {

uint32_t* __fastcall GatherTargets(void* manager, void*, uint32_t* out, const void* position, uint32_t type,
                                   uint32_t only, int32_t radius, const uint8_t* fx);
void DrawMarkers(const uint8_t* view);

namespace {

// The stunned target's motion: push 3.0f, push 0.25f... (0x5176f8) up to the
// call of 0x5936e0 (0x517709, 5 bytes): jumped over.
constexpr uint32_t kCannonStunMotion = 0x005176f8;
constexpr uint8_t kStunMotionPush[] = {0x68, 0x00};  // push 0x3e800000 (first two bytes)
constexpr uint8_t kSkipStunMotion[] = {0xeb, 0x14};  // jmp 0x51770e, after the call

// The ray's step count: cmp edi, 19h (0x517389, imm8 at +2); steps of 40.
constexpr uint32_t kCannonRaySteps = 0x00517389;
constexpr uint8_t kRayStepsOriginal = 25;
constexpr uint8_t kRaySteps = 45;

// The cannon's stun order: the return address of its call [eax+18h].
constexpr uint32_t kCannonStunOrderReturn = 0x005177ad;
constexpr uint32_t kOrderStun = 3;
constexpr DWORD kStunMs = 1500;
// The push step in cCreature::Update: lea edx,[ebp+18h]; mov edi,[esp+60h]
// (y offset; x offset in ebx); mov [ebp+24dh],eax (push left).
constexpr uint32_t kPushStep = 0x00594deb;
constexpr uint8_t kPushStepCode[] = {0x8d, 0x55, 0x18, 0x8b, 0x7c, 0x24, 0x60, 0x89, 0x85, 0x4d, 0x02, 0x00, 0x00};

std::map<uint32_t, DWORD> g_stunEnds;  // creature id -> GetTickCount at which its stun ends

constexpr uint32_t kGrenadeImpactType = 0x3fc;  // TYPE_FX_GRENADEIMPACT
constexpr uint32_t kImpactGatherCall = 0x005ab63d;  // in 0x5ab400
constexpr uint32_t kGatherInRange = 0x005ff820;  // cObjectManager: objects within type sizes
constexpr size_t kFxOwner = 0x54;  // u32: the creature the effect hits for
constexpr unsigned kLevelsPerStep = 5;
constexpr float kRadiusGrowth = 0.1f;  // of the impact's own size, per step

// The size of object type `type` (0x428bb0 on the type table *0xaa9564,
// 50 when the table has none).
int32_t TypeSize(uint32_t type) {
    using Fn = int32_t(__fastcall*)(void* table, void* edx, uint32_t type);
    return reinterpret_cast<Fn>(0x00428bb0)(*reinterpret_cast<void**>(0x00aa9564), nullptr, type);
}

// The explosion radius of a grenade thrown by `owner` (world units; a
// creature is hit when within it plus its own size).
int32_t ImpactRadiusAt(unsigned level) {
    const int32_t size = TypeSize(kGrenadeImpactType);
    return static_cast<int32_t>(static_cast<float>(size) * (1.0f + kRadiusGrowth * (level / kLevelsPerStep)));
}

int32_t ImpactRadius(void* owner) {
    return ImpactRadiusAt(owner ? game::ArtLevel(owner, game::kArtMoerser) : 0);
}

// The tooltip (game::Art::Tooltip filter, as for Kettenblitz in
// mods/chainlightning.cpp): sections start with the level line ("Aktuelle
// Stufe:", in the skill book also "Nächste erlernte Stufe:") followed by
// "Name: value" lines; each section gets "Explosionsradius: N" after its last
// value, in that line's colour.
constexpr const wchar_t* kCurrentLevelLine = L"Aktuelle Stufe:";
constexpr const wchar_t* kNextLevelLine = L"Nächste erlernte Stufe:";
constexpr const wchar_t* kValueSeparator = L": ";
constexpr size_t kColourCodeLength = 10;  // "\cAARRGGBB"

std::wstring LeadingColourCodes(const std::wstring& line) {
    size_t end = 0;
    while (line.compare(end, 2, L"\\c") == 0 && end + kColourCodeLength <= line.size()) {
        end += kColourCodeLength;
    }
    return line.substr(0, end);
}

void RewriteTooltip(const game::Art& art, void* creature, std::wstring& text) {
    std::vector<std::wstring> lines;
    for (size_t start = 0; start < text.size();) {
        size_t end = text.find(L'\n', start);
        end = end == std::wstring::npos ? text.size() : end + 1;
        lines.push_back(text.substr(start, end - start));
        start = end;
    }
    const unsigned current = game::ArtLevel(creature, art.Id());
    std::vector<std::wstring> out;
    unsigned level = current;
    bool inSection = false;
    size_t lastValue = SIZE_MAX;  // index in `out`
    const auto closeSection = [&] {
        if (!inSection || lastValue == SIZE_MAX) {
            return;
        }
        std::wstring& after = out[lastValue];
        const bool last = after.empty() || after.back() != L'\n';
        if (last) {
            after += L'\n';
        }
        out.insert(out.begin() + static_cast<ptrdiff_t>(lastValue) + 1,
                   LeadingColourCodes(after) + L"Explosionsradius: " + std::to_wstring(ImpactRadiusAt(level)) +
                       (last ? L"" : L"\n"));
    };
    for (const std::wstring& line : lines) {
        const bool currentHeader = line.find(kCurrentLevelLine) != std::wstring::npos;
        const bool nextHeader = line.find(kNextLevelLine) != std::wstring::npos;
        if (currentHeader || nextHeader) {
            closeSection();
            inSection = true;
            level = nextHeader ? current + 1 : current;
            lastValue = SIZE_MAX;
        } else if (inSection && line.find(kValueSeparator) != std::wstring::npos) {
            lastValue = out.size();
        }
        out.push_back(line);
    }
    closeSection();
    text.clear();
    for (const std::wstring& line : out) {
        text += line;
    }
}

// 0x5ab400 calls 0x5ff820 (thiscall (out, position, type, only, radius),
// ret 0x14) with the effect object in ebx.
__declspec(naked) void GatherTargetsThunk() {
    __asm {
        push ebx                 // the effect object
        push dword ptr [esp+18h] // radius (-1: the type's size)
        push dword ptr [esp+18h] // only objects of this type (0: any)
        push dword ptr [esp+18h] // type
        push dword ptr [esp+18h] // position
        push dword ptr [esp+18h] // out vector
        call GatherTargets
        ret 14h
    }
}

void OnOrder(void* creature, const game::CreatureOrder& order, void* caller) {
    if (order.command == kOrderStun && reinterpret_cast<uint32_t>(caller) == kCannonStunOrderReturn) {
        g_stunEnds[*reinterpret_cast<uint32_t*>(static_cast<uint8_t*>(creature) + game::kCreatureId)] =
            GetTickCount() + kStunMs;
    }
}

// The push step of `creature` with `left` push left after it: the push left
// to store (low dword) and whether to stay in place (high dword).
uint64_t __cdecl PushStep(uint8_t* creature, int32_t left) {
    const auto it = g_stunEnds.find(*reinterpret_cast<uint32_t*>(creature + game::kCreatureId));
    if (it == g_stunEnds.end()) {
        return static_cast<uint32_t>(left);
    }
    const bool stunned = static_cast<int32_t>(GetTickCount() - it->second) < 0;
    if (!stunned) {
        g_stunEnds.erase(it);
    }
    return (uint64_t{1} << 32) | static_cast<uint32_t>(stunned ? 1 : 0);
}

__declspec(naked) void PushStepThunk() {
    __asm {
        push eax                    // push left after this step
        push ebp                    // the creature
        call PushStep
        add esp, 8
        test edx, edx
        jz move
        xor ebx, ebx                // x offset
        mov dword ptr [esp+64h], 0  // y offset (the caller's [esp+60h])
    move:
        mov edi, [esp+64h]
        mov [ebp+24dh], eax
        lea edx, [ebp+18h]
        ret
    }
}

// The cannon creates its impact effect (TYPE_FX_DWARF_SHOOT_IMPACT 0x47f,
// attached to the target with cEventFX 0x9c) on every target it hits; it stays
// on targets that were not pushed. CreateAt (0x5fbaa0, thiscall (type,
// position, link, 0, 0), ret 0x14) at 0x517855, the target in ebx: only for
// targets in the stun state (the order was not resisted); 0 otherwise, which
// the game skips (GetObject(0) is null).
constexpr uint32_t kImpactCreate = 0x00517855;
constexpr uint32_t kCreateAt = 0x005fbaa0;
constexpr size_t kCreatureFlags = 0x200;
constexpr uint32_t kCreaturePushed = 0x20000;  // the stun's push state (cCreature::Update 0x594c82)

uint32_t __fastcall CreateImpact(void* manager, void*, uint32_t type, const void* position, uint32_t link, uint32_t a,
                                 uint32_t b, const uint8_t* target) {
    if (!target || !(*reinterpret_cast<const uint32_t*>(target + kCreatureFlags) & kCreaturePushed)) {
        return 0;
    }
    using Fn = uint32_t(__fastcall*)(void*, void*, uint32_t, const void*, uint32_t, uint32_t, uint32_t);
    return reinterpret_cast<Fn>(kCreateAt)(manager, nullptr, type, position, link, a, b);
}

__declspec(naked) void CreateImpactThunk() {
    __asm {
        push ebx                 // the target
        push dword ptr [esp+18h]
        push dword ptr [esp+18h]
        push dword ptr [esp+18h]
        push dword ptr [esp+18h]
        push dword ptr [esp+18h]
        call CreateImpact
        ret 14h
    }
}

// --- impact marker ---------------------------------------------------------

constexpr uint32_t kGrenadeEventConstruct = 0x005169fa;  // call cEventFX::Construct
constexpr uint32_t kFxEventConstruct = 0x0041e0a0;       // thiscall, ret 0x44
constexpr uint32_t kFxEventLand = 0x96;
constexpr size_t kObjectId = 0xc;
constexpr uint32_t kMarkerFill = 0x40ff0000;  // red, low alpha
constexpr uint32_t kMarkerRim = 0xa0ff2020;
constexpr float kRimWidth = 2.0f;  // screen pixels
constexpr int kCircleSegments = 48;

// A grenade object outlives its explosion by about 30 s (measured
// 2026-10-26), so its marker ends with the explosion: the impact gathering
// its targets (GatherTargets; it does so on several frames, at exactly the
// noted landing point).
constexpr float kImpactMatchDistance = 100.0f;  // world units; the landing jitter is +-15

struct Grenade {
    uint8_t* object;
    uint32_t id;
    uint32_t owner;
    float x, y;  // landing point, world units
    float radius;
};
std::vector<Grenade> g_grenades;

// The explosion of `owner`'s grenade at `position` (world units): ends the
// marker of that grenade, the owner's one closest to it.
void OnImpact(uint32_t owner, float x, float y) {
    auto closest = g_grenades.end();
    float best = kImpactMatchDistance;
    for (auto it = g_grenades.begin(); it != g_grenades.end(); ++it) {
        const float distance = std::hypot(it->x - x, it->y - y);
        if (it->owner == owner && distance < best) {
            best = distance;
            closest = it;
        }
    }
    if (closest != g_grenades.end()) {
        g_grenades.erase(closest);
    }
}

// Construct's arguments: code, owner id, target id, position (area, x, y,
// level), ...; the new grenade object is in esi.
void __cdecl NoteGrenade(const uint32_t* args, uint8_t* grenade) {
    if (args[0] != kFxEventLand || !grenade) {
        return;
    }
    const auto x = static_cast<float>(static_cast<int32_t>(args[4]));
    const auto y = static_cast<float>(static_cast<int32_t>(args[5]));
    const auto radius = static_cast<float>(ImpactRadius(game::GetCreature(args[1])));
    g_grenades.push_back({grenade, *reinterpret_cast<uint32_t*>(grenade + kObjectId), args[1], x, y, radius});
}

__declspec(naked) void GrenadeEventThunk() {
    __asm {
        pushad
        lea eax, [esp+24h]  // the arguments (above pushad and the return address)
        push esi            // the grenade
        push eax
        call NoteGrenade
        add esp, 8
        popad
        mov eax, kFxEventConstruct
        jmp eax
    }
}

bool Alive(const Grenade& grenade) {
    return game::GetObjectById(grenade.id) == grenade.object;
}

using SetRenderStateFn = HRESULT(__stdcall*)(void*, DWORD, DWORD);
using GetRenderStateFn = HRESULT(__stdcall*)(void*, DWORD, DWORD*);

// Render states for a translucent overlay without depth, restored after.
class OverlayStates {
public:
    explicit OverlayStates(void* device) : device_(device) {
        void** vtable = *static_cast<void***>(device);
        set_ = reinterpret_cast<SetRenderStateFn>(vtable[game::kDeviceSetRenderState]);
        const auto get = reinterpret_cast<GetRenderStateFn>(vtable[game::kDeviceGetRenderState]);
        for (size_t i = 0; i < kCount; ++i) {
            get(device_, kStates[i], &saved_[i]);
            set_(device_, kStates[i], kValues[i]);
        }
    }
    ~OverlayStates() {
        for (size_t i = 0; i < kCount; ++i) {
            set_(device_, kStates[i], saved_[i]);
        }
    }
    OverlayStates(const OverlayStates&) = delete;
    OverlayStates& operator=(const OverlayStates&) = delete;

private:
    // D3DRENDERSTATE ZENABLE, ZWRITEENABLE off; alpha blending SRCALPHA /
    // INVSRCALPHA.
    static constexpr size_t kCount = 5;
    static constexpr DWORD kStates[kCount] = {7, 14, game::kStateAlphaBlendEnable, game::kStateSourceBlend,
                                              game::kStateDestinationBlend};
    static constexpr DWORD kValues[kCount] = {FALSE, FALSE, TRUE, 5, 6};
    void* device_;
    SetRenderStateFn set_ = nullptr;
    DWORD saved_[kCount] = {};
};

game::ScreenVertex Vertex(const game::Point2& p, uint32_t colour) {
    return {p.x, p.y, 0, 1, colour, 0, 0, 0};
}

// The circle on the ground: a translucent disc and a brighter rim.
void DrawMarker(const uint8_t* view, void* device, const Grenade& grenade) {
    const float halfWidth = static_cast<float>(mods::widescreen::RenderWidth()) / 2;
    const auto screen = [&](float x, float y) {
        return game::PlaneToScreen(view, game::WorldToPlane(x, y), halfWidth);
    };
    const game::Point2 centre = screen(grenade.x, grenade.y);
    game::Point2 rim[kCircleSegments + 1];
    for (int i = 0; i <= kCircleSegments; ++i) {
        const float angle = 6.2831853f * static_cast<float>(i % kCircleSegments) / kCircleSegments;
        rim[i] = screen(grenade.x + grenade.radius * std::cos(angle), grenade.y + grenade.radius * std::sin(angle));
    }
    // The rim band reaches inwards from the circle by kRimWidth.
    const auto inner = [&](const game::Point2& p) {
        const float dx = centre.x - p.x, dy = centre.y - p.y;
        const float length = std::hypot(dx, dy);
        return length > kRimWidth ? game::Point2{p.x + dx / length * kRimWidth, p.y + dy / length * kRimWidth}
                                  : centre;
    };
    static std::vector<game::ScreenVertex> vertices;
    vertices.clear();
    for (int i = 0; i < kCircleSegments; ++i) {
        vertices.insert(vertices.end(),
                        {Vertex(centre, kMarkerFill), Vertex(rim[i], kMarkerFill), Vertex(rim[i + 1], kMarkerFill)});
    }
    for (int i = 0; i < kCircleSegments; ++i) {
        const game::Point2 a = rim[i], b = rim[i + 1], c = inner(rim[i]), d = inner(rim[i + 1]);
        vertices.insert(vertices.end(), {Vertex(a, kMarkerRim), Vertex(b, kMarkerRim), Vertex(c, kMarkerRim),
                                         Vertex(c, kMarkerRim), Vertex(b, kMarkerRim), Vertex(d, kMarkerRim)});
    }
    game::FillTriangles(device, vertices.data(), vertices.size());
}

void Startup() {
    const bool impact = re::RedirectCall(kImpactCreate, kCreateAt, reinterpret_cast<const void*>(&CreateImpactThunk));
    re::Log("dwarfarts: Kanonenschuss impact only on stuns%s", impact ? "" : " (patch FAILED)");
    uint8_t call[sizeof(kPushStepCode)];
    std::memset(call, 0x90, sizeof(call));
    call[0] = 0xe8;
    const int32_t rel = reinterpret_cast<int32_t>(&PushStepThunk) - static_cast<int32_t>(kPushStep + 5);
    std::memcpy(call + 1, &rel, sizeof(rel));
    const bool hold = re::ReplaceCode(kPushStep, kPushStepCode, call, sizeof(call));
    re::Log("dwarfarts: Kanonenschuss stun holds in place%s", hold ? "" : " (patch FAILED)");
    const bool stun = re::ReplaceCode(kCannonStunMotion, kStunMotionPush, kSkipStunMotion, sizeof(kSkipStunMotion));
    re::Log("dwarfarts: Kanonenschuss without stun motion%s", stun ? "" : " (patch FAILED)");
    const bool range = re::PatchInstructionByte(kCannonRaySteps, 2, kRayStepsOriginal, kRaySteps);
    re::Log("dwarfarts: Kanonenschuss range %d%s", kRaySteps * 40, range ? "" : " (patch FAILED)");
    const bool radius =
        re::RedirectCall(kImpactGatherCall, kGatherInRange, reinterpret_cast<const void*>(&GatherTargetsThunk));
    re::Log("dwarfarts: Mörsergranate radius%s", radius ? "" : " (patch FAILED)");
    const bool marker = re::RedirectCall(kGrenadeEventConstruct, kFxEventConstruct,
                                         reinterpret_cast<const void*>(&GrenadeEventThunk));
    re::Log("dwarfarts: Mörsergranate impact marker%s", marker ? "" : " (patch FAILED)");
}
RE_STARTUP(DwarfArtsStartup, Startup);

struct Registration {
    Registration() {
        game::OnCreatureOrder(&OnOrder);
        game::AddTooltipFilter(game::kArtMoerser, &RewriteTooltip);
    }
} g_registration;

} // namespace

uint32_t* __fastcall GatherTargets(void* manager, void*, uint32_t* out, const void* position, uint32_t type,
                                   uint32_t only, int32_t radius, const uint8_t* fx) {
    if (type == kGrenadeImpactType && radius < 0 && fx) {
        const uint32_t owner = *reinterpret_cast<const uint32_t*>(fx + kFxOwner);
        radius = ImpactRadius(game::GetCreature(owner));
        // The position: area (u16), x, y (int32, world units), level.
        const auto* at = static_cast<const uint8_t*>(position);
        OnImpact(owner, static_cast<float>(*reinterpret_cast<const int32_t*>(at + 4)),
                 static_cast<float>(*reinterpret_cast<const int32_t*>(at + 8)));
    }
    using Fn = uint32_t*(__fastcall*)(void*, void*, uint32_t*, const void*, uint32_t, uint32_t, int32_t);
    return reinterpret_cast<Fn>(kGatherInRange)(manager, nullptr, out, position, type, only, radius);
}

// The impact markers of the grenades in flight, on the ground of `view`.
void DrawMarkers(const uint8_t* view) {
    g_grenades.erase(std::remove_if(g_grenades.begin(), g_grenades.end(), [](const Grenade& g) { return !Alive(g); }),
                     g_grenades.end());
    void* device = game::RenderDevice();
    if (g_grenades.empty() || !device) {
        return;
    }
    OverlayStates states(device);
    for (const Grenade& grenade : g_grenades) {
        DrawMarker(view, device, grenade);
    }
}

} // namespace mods::dwarfarts

namespace game {

// cWorldView0::DrawGroundQuads (0x62d530, thiscall (renderer), ret 4): the
// ground; the objects are drawn after it.
void __fastcall WorldView_DrawGroundQuads(uint8_t* self, void* edx, void* renderer);
RE_HOOK(0x0062d530, WorldView_DrawGroundQuads);
void __fastcall WorldView_DrawGroundQuads(uint8_t* self, void* edx, void* renderer) {
    WorldView_DrawGroundQuads_original(self, edx, renderer);
    if (self) {
        mods::dwarfarts::DrawMarkers(self);
    }
}

} // namespace game