/**
 * @file Capture.cpp
 * @brief 后备缓冲抓帧、区域哈希、PNG 落盘、目录工具。
 *
 * 全程不碰窗口 DC：读的是 `Application::BackBufferSurface()` 给的 top-down 32bpp DIB 段，
 * 因此窗口即使被隐藏（`SW_HIDE`）也能抓到与真实显示一致的像素。
 */

#include <windows.h>
#include <objidl.h>
#include <gdiplus.h>

#include <cstdio>
#include <cstring>
#include <string>
#include <unordered_map>
#include <vector>

#include "OffscreenSupport.hpp"

namespace jdi
{
	namespace tools
	{
		namespace
		{
			/** @brief 取 GDI+ 编码器的 CLSID。 */
			bool FindEncoderClsid(const wchar_t* mimeType, CLSID& clsid)
			{
				UINT count = 0;
				UINT size = 0;
				if (Gdiplus::GetImageEncodersSize(&count, &size) != Gdiplus::Ok || size == 0)
				{
					return false;
				}
				std::vector<std::uint8_t> buffer(size);
				Gdiplus::ImageCodecInfo* codecs =
				    reinterpret_cast<Gdiplus::ImageCodecInfo*>(buffer.data());
				if (Gdiplus::GetImageEncoders(count, size, codecs) != Gdiplus::Ok)
				{
					return false;
				}
				for (UINT index = 0; index < count; ++index)
				{
					if (wcscmp(codecs[index].MimeType, mimeType) == 0)
					{
						clsid = codecs[index].Clsid;
						return true;
					}
				}
				return false;
			}

			/** @brief 把 ASCII 路径转宽字符串。 */
			std::wstring WidenPath(const std::string& path)
			{
				const int length = MultiByteToWideChar(CP_ACP, 0, path.c_str(), -1, nullptr, 0);
				if (length <= 1)
				{
					return std::wstring();
				}
				std::wstring wide(static_cast<std::size_t>(length - 1), L'\0');
				MultiByteToWideChar(CP_ACP, 0, path.c_str(), -1, &wide[0], length);
				return wide;
			}

			/** @brief 夹取区域到帧内，返回 false 表示空区域。 */
			bool ClampRect(const Frame& frame, const PixelRect& rect, PixelRect& clamped)
			{
				const int left = std::max(0, rect.x);
				const int top = std::max(0, rect.y);
				const int right = std::min(frame.width, rect.x + rect.width);
				const int bottom = std::min(frame.height, rect.y + rect.height);
				if (right <= left || bottom <= top)
				{
					return false;
				}
				clamped.x = left;
				clamped.y = top;
				clamped.width = right - left;
				clamped.height = bottom - top;
				return true;
			}
		} // namespace

		bool CaptureFrame(const Application& app, Frame& frame)
		{
			const UiSurface surface = app.BackBufferSurface();
			if (!surface.Valid() || surface.bits == nullptr || surface.stride <= 0)
			{
				return false;
			}
			const int width = static_cast<int>(surface.rect.Width);
			const int height = static_cast<int>(surface.rect.Height);
			const std::size_t bytes = static_cast<std::size_t>(surface.stride) *
			                          static_cast<std::size_t>(height);

			frame.width = width;
			frame.height = height;
			frame.stride = surface.stride;
			frame.pixels.resize(bytes);
			std::memcpy(frame.pixels.data(), surface.bits, bytes);
			return true;
		}

		std::uint64_t HashRegion(const Frame& frame, const PixelRect& rect)
		{
			PixelRect area;
			if (!frame.Valid() || !ClampRect(frame, rect, area))
			{
				return 0ull;
			}
			std::uint64_t hash = 1469598103934665603ull;	// FNV-1a 64 位 offset basis
			for (int row = 0; row < area.height; ++row)
			{
				const std::uint8_t* line = frame.Row(area.y + row) + static_cast<std::size_t>(area.x) * 4u;
				for (int column = 0; column < area.width; ++column)
				{
					// 只混 BGR：GDI 写 DIB 时不设置 alpha 字节，混进去会让哈希随填充方式漂移。
					hash ^= line[column * 4 + 0];
					hash *= 1099511628211ull;
					hash ^= line[column * 4 + 1];
					hash *= 1099511628211ull;
					hash ^= line[column * 4 + 2];
					hash *= 1099511628211ull;
				}
			}
			return hash;
		}

		int CountInk(const Frame& frame, const PixelRect& rect)
		{
			PixelRect area;
			if (!frame.Valid() || !ClampRect(frame, rect, area))
			{
				return 0;
			}
			// 先找到一个"主色"（出现次数最多的颜色 = 背景），再数与之不同的像素。
			std::unordered_map<std::uint32_t, int> histogram;
			histogram.reserve(static_cast<std::size_t>(area.width) * 2u);
			for (int row = 0; row < area.height; row += 2)
			{
				const std::uint8_t* line = frame.Row(area.y + row) + static_cast<std::size_t>(area.x) * 4u;
				for (int column = 0; column < area.width; column += 2)
				{
					const std::uint32_t color = static_cast<std::uint32_t>(line[column * 4 + 0]) |
					                            (static_cast<std::uint32_t>(line[column * 4 + 1]) << 8) |
					                            (static_cast<std::uint32_t>(line[column * 4 + 2]) << 16);
					++histogram[color];
				}
			}
			std::uint32_t background = 0;
			int best = -1;
			for (const auto& entry : histogram)
			{
				if (entry.second > best)
				{
					best = entry.second;
					background = entry.first;
				}
			}

			int ink = 0;
			for (int row = 0; row < area.height; ++row)
			{
				const std::uint8_t* line = frame.Row(area.y + row) + static_cast<std::size_t>(area.x) * 4u;
				for (int column = 0; column < area.width; ++column)
				{
					const std::uint32_t color = static_cast<std::uint32_t>(line[column * 4 + 0]) |
					                            (static_cast<std::uint32_t>(line[column * 4 + 1]) << 8) |
					                            (static_cast<std::uint32_t>(line[column * 4 + 2]) << 16);
					if (color != background)
					{
						++ink;
					}
				}
			}
			return ink;
		}

		int CountDiff(const Frame& left, const Frame& right, const PixelRect& rect, const int tolerance)
		{
			PixelRect area;
			if (!left.Valid() || !right.Valid() || left.width != right.width ||
			    left.height != right.height || !ClampRect(left, rect, area))
			{
				return -1;
			}
			int changed = 0;
			for (int row = 0; row < area.height; ++row)
			{
				const std::uint8_t* a = left.Row(area.y + row) + static_cast<std::size_t>(area.x) * 4u;
				const std::uint8_t* b = right.Row(area.y + row) + static_cast<std::size_t>(area.x) * 4u;
				for (int column = 0; column < area.width; ++column)
				{
					const int deltaB = std::abs(static_cast<int>(a[column * 4 + 0]) - b[column * 4 + 0]);
					const int deltaG = std::abs(static_cast<int>(a[column * 4 + 1]) - b[column * 4 + 1]);
					const int deltaR = std::abs(static_cast<int>(a[column * 4 + 2]) - b[column * 4 + 2]);
					if (deltaB > tolerance || deltaG > tolerance || deltaR > tolerance)
					{
						++changed;
					}
				}
			}
			return changed;
		}

		bool SavePng(const Frame& frame, const std::string& path)
		{
			if (!frame.Valid())
			{
				return false;
			}
			const std::size_t slash = path.find_last_of("/\\");
			if (slash != std::string::npos)
			{
				EnsureDirectory(path.substr(0, slash));
			}

			Gdiplus::Bitmap bitmap(frame.width, frame.height, frame.stride,
			                       PixelFormat32bppRGB,
			                       const_cast<BYTE*>(frame.pixels.data()));
			if (bitmap.GetLastStatus() != Gdiplus::Ok)
			{
				return false;
			}
			CLSID pngClsid = {};
			if (!FindEncoderClsid(L"image/png", pngClsid))
			{
				return false;
			}
			const std::wstring widePath = WidenPath(path);
			const Gdiplus::Status status = bitmap.Save(widePath.c_str(), &pngClsid, nullptr);
			return status == Gdiplus::Ok;
		}

		void EnsureDirectory(const std::string& asciiPath)
		{
			if (asciiPath.empty())
			{
				return;
			}
			const std::wstring wide = WidenPath(asciiPath);
			if (wide.empty())
			{
				return;
			}
			std::wstring prefix;
			prefix.reserve(wide.size());
			for (std::size_t index = 0; index < wide.size(); ++index)
			{
				prefix.push_back(wide[index]);
				const bool boundary =
				    (wide[index] == L'/' || wide[index] == L'\\' || index + 1 == wide.size());
				if (boundary)
				{
					if (!prefix.empty() && prefix.back() != L'/' && prefix.back() != L'\\')
					{
						CreateDirectoryW(prefix.c_str(), nullptr);
					}
				}
			}
		}

		void RemoveDirectoryTree(const std::string& asciiPath)
		{
			const std::wstring wide = WidenPath(asciiPath);
			if (wide.empty())
			{
				return;
			}
			// 用 SHFileOperation 太重；这里用"先递归删文件再删目录"的最小实现。
			WIN32_FIND_DATAW data = {};
			HANDLE handle = FindFirstFileW((wide + L"\\*").c_str(), &data);
			if (handle != INVALID_HANDLE_VALUE)
			{
				do
				{
					if (wcscmp(data.cFileName, L".") == 0 || wcscmp(data.cFileName, L"..") == 0)
					{
						continue;
					}
					const std::wstring child = wide + L"\\" + data.cFileName;
					if ((data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0)
					{
						const int length = WideCharToMultiByte(CP_ACP, 0, child.c_str(), -1, nullptr, 0,
						                                       nullptr, nullptr);
						std::string narrow(static_cast<std::size_t>(std::max(0, length - 1)), '\0');
						if (length > 1)
						{
							WideCharToMultiByte(CP_ACP, 0, child.c_str(), -1, &narrow[0], length, nullptr,
							                    nullptr);
						}
						RemoveDirectoryTree(narrow);
					}
					else
					{
						DeleteFileW(child.c_str());
					}
				} while (FindNextFileW(handle, &data) != FALSE);
				FindClose(handle);
			}
			RemoveDirectoryW(wide.c_str());
		}
	} // namespace tools
} // namespace jdi