# Copyright © 2022, 飞麦 <fitmap@qq.com>, All rights reserved.

# frozen_string_literal: true

require 'fiddle/import'

# Clipboard only for Windows, can use both in x86 and x64
# size_t and handles must use void* (NOT uint) in Fiddle to fit the pointer size of x86 or x64
# if use size_t as return value, you need add to_i to it.
module Clipboard
  module_function

  extend Fiddle::Importer
  include Fiddle::CParser

  dlload 'kernel32', 'user32'

  # HWND GetClipboardOwner();
  extern 'void* GetClipboardOwner()'

  # HWND GetClipboardViewer();
  extern 'void* GetClipboardViewer()'

  # HWND GetDesktopWindow();
  extern 'void* GetDesktopWindow()'

  # BOOL OpenClipboard(
  #   _In_opt_ HWND hWndNewOwner
  # );
  extern 'int OpenClipboard(void*)'

  # BOOL CloseClipboard();
  extern 'int CloseClipboard()'

  # BOOL EmptyClipboard();
  extern 'int EmptyClipboard()'

  # Predefined Clipboard Formats
  CF_UNICODETEXT = 13

  # HANDLE GetClipboardData(
  #   _In_ UINT uFormat
  # );
  extern 'void* GetClipboardData(uint)'

  # HANDLE SetClipboardData(
  #   _In_     UINT   uFormat,
  #   _In_opt_ HANDLE hMem
  # );
  extern 'void* SetClipboardData(uint, void*)'

  # Global Memory Flags
  GMEM_FIXED = 0x0000 # Don't use GMEM_MOVEABLE = 0x0002(need GlobalLock and GlobalUnlock)

  # HGLOBAL GlobalAlloc(
  #   _In_ UINT   uFlags,
  #   _In_ SIZE_T dwBytes
  # );
  extern 'void* GlobalAlloc(uint, void*)'

  # SIZE_T GlobalSize(
  #   _In_ HGLOBAL hMem
  # );
  extern 'void* GlobalSize(void*)'

  # void RtlCopyMemory(
  #   _In_       PVOID  Destination,
  #   _In_ const VOID   *Source,
  #   _In_       SIZE_T Length
  # );
  extern 'void RtlCopyMemory(void*, const void*, void*)'

  # DWORD GetLastError();
  extern 'uint GetLastError()'

  def show(_str)
    # puts _str # uncomment only when debug
    nil
  end

  def clip_hwnd
    hwnd = GetClipboardOwner()
    show("GetClipboardOwner fail! Error=#{GetLastError()}") if hwnd.null?
    hwnd.null? ? nil : hwnd
  end

  def view_hwnd
    hwnd = GetClipboardViewer()
    show("GetClipboardViewer fail! Error=#{GetLastError()}") if hwnd.null?
    hwnd.null? ? nil : hwnd
  end

  def desk_hwnd
    GetDesktopWindow()
  end

  def find_hwnd
    clip_hwnd || view_hwnd || desk_hwnd
  end

  # Sometimes OpenClipboard will fail without any error, so we need retry
  def open_cb
    999.times do
      hwnd = find_hwnd
      next unless hwnd

      break unless OpenClipboard(hwnd).zero?

      show("OpenClipboard fail! Error=#{GetLastError()}")
    end
  end

  def empty_cb
    999.times do
      break unless EmptyClipboard().zero?

      show("EmptyClipboard fail! Error=#{GetLastError()}")
    end
  end

  def close_cb
    999.times do
      break unless CloseClipboard().zero?

      show("CloseClipboard fail! Error=#{GetLastError()}")
    end
  end

  def move_it(text)
    text_16le = "#{text}\u0000".encode(Encoding::UTF_16LE) # must append \u0000 for text
    len = text_16le.bytesize
    hmem = GlobalAlloc(GMEM_FIXED, len)
    show("#GlobalAlloc fail! Error=#{GetLastError()}") if hmem.null?
    RtlCopyMemory(hmem, text_16le, len)
    hmem
  end

  def save_it(hmem)
    hndl = SetClipboardData(CF_UNICODETEXT, hmem)
    show("#SetClipboardData Error=#{GetLastError()} hmem=#{hmem.to_i} != hndl=#{hndl.to_i}") if hndl != hmem
  end

  def copy(text)
    open_cb
    empty_cb
    hmem = move_it(text)
    save_it(hmem)
    close_cb
  end

  def clear
    open_cb
    empty_cb
    close_cb
  end

  def load_it(hmem)
    len = GlobalSize(hmem).to_i
    show("GlobalSize Error=#{GetLastError()} len=#{len}") if len.zero?
    len -= 2 # needn't copy tail \u0000
    text = ''.encode(Encoding::UTF_16LE) * (len / 2)
    RtlCopyMemory(text, hmem, len)
    text.encode(Encoding::UTF_8)
  end

  def paste
    open_cb
    hmem = GetClipboardData(CF_UNICODETEXT)
    text = hmem.null? ? '' : load_it(hmem)
    close_cb
    text
  end
end