/*
 * Copyright (c) 2019-2021, NVIDIA CORPORATION.  All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-FileCopyrightText: Copyright (c) 2019-2021 NVIDIA CORPORATION
 * SPDX-License-Identifier: Apache-2.0
 */
 //--------------------------------------------------------------------

#include "nvpsystem.hpp"

#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
#define GLFW_EXPOSE_NATIVE_X11
#include <GLFW/glfw3native.h>

#include <vector>
#include <algorithm>
#include <unistd.h>
#include <stdio.h>
#include <limits.h>
#include <string>
#include <assert.h>
#include <memory>
#include <sys/shm.h>
#include <X11/extensions/XShm.h>

// Samples include their own definitions of stb_image. Use STB_IMAGE_WRITE_STATIC to avoid issues with multiple
// definitions in the nvpro_core static lib at the cost of having the code exist multiple times.
#define STB_IMAGE_WRITE_IMPLEMENTATION
#define STB_IMAGE_WRITE_STATIC
#include <stb_image_write.h>

#include "linux_file_dialog.h"

union Pixel
{
  uint32_t data;
  struct
  {
    uint8_t r, g, b, a;
  } channels;
};

// Object to allocate and hold a shared memory XImage and a shared memory segment
// This allows reading/writing an XImage in one IPC call
// Check XShmQueryExtension() before using
class XShmImage
{
public:
  XShmImage(Display* display, int width, int height)
      : m_display{display}
  {
    // Allocate a shared XImage
    int     screen = XDefaultScreen(m_display);
    Visual* visual = XDefaultVisual(m_display, screen);
    int     depth  = DefaultDepth(m_display, screen);
    m_image        = XShmCreateImage(m_display, visual, depth, ZPixmap, nullptr, &m_shmSegmentInfo, width, height);
    if(!m_image)
    {
      LOGE("Error: XShmCreateImage() failed\n");
      return;
    }

    // Create the shared memory, used by XShmGetImage()
    int permissions = 0600;
    m_shmID         = shmget(IPC_PRIVATE, height * m_image->bytes_per_line, IPC_CREAT | permissions);
    if(m_shmID == -1)
    {
      LOGE("Error: shmget() failed\n");
      return;
    }

    // Map the shared memory segment into the address space of this process
    m_shmAddr = shmat(m_shmID, 0, 0);
    if(reinterpret_cast<intptr_t>(m_shmAddr) == -1)
    {
      LOGE("Error: shmat() failed\n");
      return;
    }

    // Use the allocated shared memory for the XImage
    m_shmSegmentInfo.shmid    = m_shmID;
    m_shmSegmentInfo.shmaddr  = reinterpret_cast<char*>(m_shmAddr);
    m_shmSegmentInfo.readOnly = false;
    m_image->data             = m_shmSegmentInfo.shmaddr;

    // Get the X server to attach the shared memory segment on its side and sync
    if(!XShmAttach(m_display, &m_shmSegmentInfo))
      LOGE("Error: XShmAttach() failed\n");
    if(!XSync(m_display, false))
      LOGE("Error: XSync() failed\n");
    return;
  }
  ~XShmImage()
  {
    if(m_image)
    {
      if(!XShmDetach(m_display, &m_shmSegmentInfo))
        LOGE("Error: XShmDetach() failed\n");
      if(!XDestroyImage(m_image))
        LOGE("Error: XDestroyImage() failed\n");
    }
    if(reinterpret_cast<intptr_t>(m_shmAddr) != -1 && shmdt(m_shmAddr) == -1)
      LOGE("Error: shmdt() failed\n");
    if(m_shmID != -1 && shmctl(m_shmID, IPC_RMID, nullptr) == -1)
      LOGE("Error: shmctl(IPC_RMID) failed\n");
  }

  // Get the X server to copy the window contents into the shared memory
  bool read(Window window) { return XShmGetImage(m_display, window, m_image, 0, 0, AllPlanes); }

  // In lieu of exceptions, call this after constructing to see if the constructor failed
  bool valid() const { return m_shmID != -1 && reinterpret_cast<intptr_t>(m_shmAddr) != -1; }

  // Returns the XImage object to be accessed after calling read()
  XImage* image() const { return m_image; }

private:
  int             m_shmID{-1};
  void*           m_shmAddr{reinterpret_cast<void*>(-1)};
  XShmSegmentInfo m_shmSegmentInfo{};
  Display*        m_display{};
  XImage*         m_image{};
};

void NVPSystem::windowScreenshot(struct GLFWwindow* glfwin, const char* filename)
{
  const int                  bytesPerPixel = sizeof(Pixel);
  int                        width{};
  int                        height{};
  std::unique_ptr<XShmImage> shmImage;
  std::vector<Pixel>         imageData;
  XImage*                    fallbackXImage{};

  Display* display = glfwGetX11Display();
  Window   window  = glfwGetX11Window(glfwin);
  glfwGetWindowSize(glfwin, &width, &height);

  if(XShmQueryExtension(display))
  {
    // Use the shared memory extension if it is supported to avoid expensive XGetPixel calls
    // Shared memory allows X11 to copy all the image data at once
    shmImage = std::make_unique<XShmImage>(display, width, height);
    if(shmImage->valid() && bytesPerPixel * 8 == shmImage->image()->bits_per_pixel)
    {
      if(shmImage->read(window))
      {
        XImage* ximg = shmImage->image();
        imageData.reserve(width * height);
        for(int y = 0; y < ximg->height; ++y)
        {
          Pixel* ximgData = reinterpret_cast<Pixel*>(ximg->data + ximg->bytes_per_line * y);
          imageData.insert(imageData.end(), ximgData, ximgData + ximg->width);
        }

        // bgr to rgb
        for(Pixel& pixel : imageData)
        {
          std::swap(pixel.channels.r, pixel.channels.b);
        }
      }
      else
      {
        LOGE("Error: Failed to get window contents for screenshot. Falling back to XGetPixel()\n");
      }
    }
    else
    {
      LOGE("Error: Failed to create XShm Image for screenshot. Falling back to XGetPixel()\n");
    }
  }

  if(imageData.empty())
  {
    fallbackXImage = XGetImage(display, window, 0, 0, width, height, AllPlanes, ZPixmap);
    if(!fallbackXImage)
    {
      LOGE("Error: XGetImage() failed to get window contents for screenshot\n");
      return;
    }
    if(bytesPerPixel * 8 != fallbackXImage->bits_per_pixel)
    {
      LOGE("Error: XGetImage() returned an image with %i bits per pixel but only %i is supported\n",
           fallbackXImage->bits_per_pixel, bytesPerPixel * 8);
      return;
    }
    imageData.reserve(width * height);
    for(int y = 0; y < height; ++y)
    {
      for(int x = 0; x < width; ++x)
      {
        Pixel pixel;
        pixel.data = static_cast<uint32_t>(XGetPixel(fallbackXImage, x, y));
        std::swap(pixel.channels.r, pixel.channels.b);  // bgr to rgb
        pixel.channels.a = 0xff;                        // set full alpha
        imageData.push_back(pixel);
      }
    }
  }

  if(!stbi_write_png(filename, width, height, 4, imageData.data(), width * bytesPerPixel))
  {
    LOGE("Error: Writing %s failed\n", filename);
  }

  if(fallbackXImage && !XDestroyImage(fallbackXImage))
    LOGE("Error: XDestroyImage() failed\n");
}

void NVPSystem::windowClear(struct GLFWwindow* glfwin, uint32_t r, uint32_t g, uint32_t b)
{
  Window hwnd = glfwGetX11Window(glfwin);
  assert(0 && "not yet implemented");
}

static void fixSingleFilter(std::string* pFilter);

static std::vector<std::string> toFilterArgs(const char* exts)
{
  // Convert exts list to filter format recognized by portable-file-dialogs
  // Try to match implemented nvpsystem on Windows behavior:
  // Alternate between human-readable descriptions and filter strings.
  // | separates strings
  // ; separates filters e.g. .png|.gif
  // Case-insensitive e.g. .png = .PNG = .pNg

  // Split strings by |
  std::vector<std::string> filterArgs(1);
  for(const char* pC = exts; pC != nullptr && *pC != '\0'; ++pC)
  {
    char c = *pC;
    if(c == '|')
      filterArgs.emplace_back();
    else
      filterArgs.back().push_back(c);
  }

  // Default arguments
  if(filterArgs.size() < 2)
  {
    filterArgs = {"All files", "*"};
  }

  // Split filters by ; and fix those filters.
  for(size_t i = 1; i < filterArgs.size(); i += 2)
  {
    std::string& arg = filterArgs[i];
    std::string  newArg;
    std::string  singleFilter;
    for(char c : arg)
    {
      if(c == ';')
      {
        fixSingleFilter(&singleFilter);
        newArg += std::move(singleFilter);
        singleFilter.clear();
        newArg += ' ';  // portable-file-dialogs uses spaces to separate... win32 wants no spaces in filters at all so presumably this is fine.
      }
      else
      {
        singleFilter.push_back(c);
      }
    }
    fixSingleFilter(&singleFilter);
    newArg += std::move(singleFilter);
    arg = std::move(newArg);
  }

  return filterArgs;
}

static void fixSingleFilter(std::string* pFilter)
{
  // Make case insensitive.
  std::string newFilter;
  for(char c : *pFilter)
  {
    if(('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'))
    {
      // replace c with [cC] to make case-insensitive. TODO: Unicode support, not sure how to implement for multibyte utf-8 characters.
      newFilter.push_back('[');
      newFilter.push_back(c);
      newFilter.push_back(char(c ^ 32));
      newFilter.push_back(']');
    }
    else
    {
      newFilter.push_back(c);
    }
  }
  *pFilter = std::move(newFilter);
}

std::string NVPSystem::windowOpenFileDialog(struct GLFWwindow* glfwin, const char* title, const char* exts)
{
  // Not sure yet how to use this; maybe make as a child window somehow?
  [[maybe_unused]] Window hwnd = glfwGetX11Window(glfwin);

  std::vector<std::string> filterArgs   = toFilterArgs(exts);
  std::vector<std::string> resultVector = open_file(title, ".", filterArgs).result();
  assert(resultVector.size() <= 1);
  return resultVector.empty() ? "" : std::move(resultVector[0]);
}

std::string NVPSystem::windowSaveFileDialog(struct GLFWwindow* glfwin, const char* title, const char* exts)
{
  // Not sure yet how to use this; maybe make as a child window somehow?
  [[maybe_unused]] Window hwnd = glfwGetX11Window(glfwin);

  std::vector<std::string> filterArgs = toFilterArgs(exts);
  return save_file(title, ".", filterArgs).result();
}

void NVPSystem::sleep(double seconds)
{
  ::sleep(seconds);
}

void NVPSystem::platformInit()
{
}

void NVPSystem::platformDeinit()
{
}

static bool        s_exePathInit = false;

std::string NVPSystem::exePath()
{
  static std::string s_exePath;

  if(!s_exePathInit)
  {
    char modulePath[PATH_MAX];
    ssize_t modulePathLength = readlink( "/proc/self/exe", modulePath, PATH_MAX );

    s_exePath = std::string(modulePath, modulePathLength > 0 ? modulePathLength : 0);

    size_t last = s_exePath.rfind('/');
    if(last != std::string::npos)
    {
      s_exePath = s_exePath.substr(0, last) + std::string("/");
    }

    s_exePathInit = true;
  }

  return s_exePath;
}