// Crash report: on an unhandled exception, writes sacred_re_crash.txt (code,
// address as module + offset, registers, return addresses found on the stack)
// and sacred_re_crash.dmp next to the DLL. The game may install its own
// filter later; SetUnhandledExceptionFilter is hooked so ours stays first and
// passes the crash on to the game's afterwards.
//
// Hangs: a watchdog thread writes sacred_re_hang.dmp (all threads) when the
// engine tick (re::EngineHeartbeat) has stopped for kHangMs while the game
// window is in front; once per hang. The game freezing on F2 while walking
// (2026-10-18) left no report.

#include "re/crash.h"

#include <cstdio>
#include <string>

#include <windows.h>

#include <dbghelp.h>

#include "re/hook.h"
#include "re/log.h"

namespace re {
namespace {

std::wstring g_dir;
LPTOP_LEVEL_EXCEPTION_FILTER g_gameFilter = nullptr;
volatile LONG g_reported = 0;

// "module+offset" for a code address.
void DescribeAddress(uintptr_t address, char* out, size_t size) {
    HMODULE module = nullptr;
    char path[MAX_PATH] = "?";
    if (GetModuleHandleExA(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
                           reinterpret_cast<LPCSTR>(address), &module)) {
        GetModuleFileNameA(module, path, MAX_PATH);
        const char* name = strrchr(path, '\\');
        snprintf(out, size, "%08x %s+%x", static_cast<unsigned>(address), name ? name + 1 : path,
                 static_cast<unsigned>(address - reinterpret_cast<uintptr_t>(module)));
    } else {
        snprintf(out, size, "%08x", static_cast<unsigned>(address));
    }
}

bool IsCode(uintptr_t address) {
    MEMORY_BASIC_INFORMATION info;
    if (!VirtualQuery(reinterpret_cast<void*>(address), &info, sizeof(info)) || info.State != MEM_COMMIT) {
        return false;
    }
    return (info.Protect & (PAGE_EXECUTE | PAGE_EXECUTE_READ | PAGE_EXECUTE_READWRITE)) != 0;
}

void WriteReport(EXCEPTION_POINTERS* info) {
    FILE* file = _wfopen((g_dir + L"sacred_re_crash.txt").c_str(), L"w");
    if (!file) {
        return;
    }
    const EXCEPTION_RECORD& record = *info->ExceptionRecord;
    const CONTEXT& c = *info->ContextRecord;
    char where[MAX_PATH + 32];
    DescribeAddress(reinterpret_cast<uintptr_t>(record.ExceptionAddress), where, sizeof(where));
    fprintf(file, "exception %08lx at %s, thread %lu\n", record.ExceptionCode, where, GetCurrentThreadId());
    if (record.ExceptionCode == EXCEPTION_ACCESS_VIOLATION && record.NumberParameters >= 2) {
        fprintf(file, "%s address %08x\n", record.ExceptionInformation[0] ? "writing" : "reading",
                static_cast<unsigned>(record.ExceptionInformation[1]));
    }
    fprintf(file, "eax %08lx ebx %08lx ecx %08lx edx %08lx esi %08lx edi %08lx ebp %08lx esp %08lx\n", c.Eax, c.Ebx,
            c.Ecx, c.Edx, c.Esi, c.Edi, c.Ebp, c.Esp);
    // Frame pointer chain (our debug build and most of sacred.exe keep ebp).
    fprintf(file, "frames (ebp chain):\n");
    uintptr_t frame = c.Ebp;
    for (int i = 0; i < 64 && frame; ++i) {
        MEMORY_BASIC_INFORMATION mem;
        if (!VirtualQuery(reinterpret_cast<void*>(frame), &mem, sizeof(mem)) || mem.State != MEM_COMMIT) {
            break;
        }
        const auto* slots = reinterpret_cast<const uintptr_t*>(frame);
        DescribeAddress(slots[1], where, sizeof(where));
        fprintf(file, "  %s\n", where);
        if (slots[0] <= frame) {
            break;
        }
        frame = slots[0];
    }
    fprintf(file, "code addresses on the stack (innermost first; may include data):\n");
    const auto* stack = reinterpret_cast<const uintptr_t*>(c.Esp);
    int found = 0;
    for (int i = 0; i < 4096 && found < 48; ++i) {
        MEMORY_BASIC_INFORMATION mem;
        if (!VirtualQuery(stack + i, &mem, sizeof(mem)) || mem.State != MEM_COMMIT) {
            break;
        }
        const uintptr_t value = stack[i];
        if (IsCode(value)) {
            DescribeAddress(value, where, sizeof(where));
            fprintf(file, "  [esp+%04x] %s\n", i * 4, where);
            ++found;
        }
    }
    fclose(file);

    HANDLE dump = CreateFileW((g_dir + L"sacred_re_crash.dmp").c_str(), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS,
                              FILE_ATTRIBUTE_NORMAL, nullptr);
    if (dump != INVALID_HANDLE_VALUE) {
        MINIDUMP_EXCEPTION_INFORMATION exception = {GetCurrentThreadId(), info, FALSE};
        MiniDumpWriteDump(GetCurrentProcess(), GetCurrentProcessId(), dump, MiniDumpWithIndirectlyReferencedMemory,
                          &exception, nullptr, nullptr);
        CloseHandle(dump);
    }
}

constexpr DWORD kHangMs = 10000;
volatile LONG g_lastBeat = 0;  // GetTickCount of the last engine tick, 0: no game running

bool GameInFront() {
    DWORD process = 0;
    GetWindowThreadProcessId(GetForegroundWindow(), &process);
    return process == GetCurrentProcessId();
}

void WriteHangDump() {
    HANDLE dump = CreateFileW((g_dir + L"sacred_re_hang.dmp").c_str(), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS,
                              FILE_ATTRIBUTE_NORMAL, nullptr);
    if (dump != INVALID_HANDLE_VALUE) {
        MiniDumpWriteDump(GetCurrentProcess(), GetCurrentProcessId(), dump,
                          static_cast<MINIDUMP_TYPE>(MiniDumpWithIndirectlyReferencedMemory | MiniDumpWithThreadInfo),
                          nullptr, nullptr, nullptr);
        CloseHandle(dump);
    }
}

DWORD WINAPI Watchdog(void*) {
    bool reported = false;
    for (;;) {
        Sleep(1000);
        const DWORD beat = static_cast<DWORD>(g_lastBeat);
        // Signed: a tick may land between reading the beat and the clock.
        if (beat == 0 || static_cast<LONG>(GetTickCount() - beat) < static_cast<LONG>(kHangMs)) {
            reported = false;
            continue;
        }
        if (!reported && GameInFront()) {
            reported = true;
            Log("hang: no engine tick for %lu ms, writing sacred_re_hang.dmp", GetTickCount() - beat);
            WriteHangDump();
            Log("hang: dump written");
        }
    }
}

LONG WINAPI Filter(EXCEPTION_POINTERS* info) {
    if (InterlockedExchange(&g_reported, 1) == 0) {
        WriteReport(info);
    }
    return g_gameFilter ? g_gameFilter(info) : EXCEPTION_CONTINUE_SEARCH;
}

} // namespace

void InstallCrashHandler(const std::wstring& dir) {
    g_dir = dir;
    g_gameFilter = SetUnhandledExceptionFilter(&Filter);
    if (HANDLE thread = CreateThread(nullptr, 0, &Watchdog, nullptr, 0, nullptr)) {
        CloseHandle(thread);
    }
}

void EngineHeartbeat(bool running) {
    InterlockedExchange(&g_lastBeat, running ? static_cast<LONG>(GetTickCount() | 1) : 0);
}

} // namespace re

// The game's own filter goes behind ours.
LPTOP_LEVEL_EXCEPTION_FILTER WINAPI Hooked_SetUnhandledExceptionFilter(LPTOP_LEVEL_EXCEPTION_FILTER filter);
RE_HOOK_API(SetUnhandledExceptionFilter, Hooked_SetUnhandledExceptionFilter);
LPTOP_LEVEL_EXCEPTION_FILTER WINAPI Hooked_SetUnhandledExceptionFilter(LPTOP_LEVEL_EXCEPTION_FILTER filter) {
    if (filter == &re::Filter) {
        return Hooked_SetUnhandledExceptionFilter_original(filter);
    }
    LPTOP_LEVEL_EXCEPTION_FILTER previous = re::g_gameFilter;
    re::g_gameFilter = filter;
    return previous;
}