require 'memory_buffer'
require 'Win32API'

class MiqLargeFileWin32
  # Access specifiers.
  GENERIC_READ  = 0x80000000
  GENERIC_WRITE = 0x40000000

  # Share specifiers.
  FILE_SHARE_READ   = 0x00000001
  FILE_SHARE_WRITE  = 0x00000002

  # Creation disposition specifiers.
  OPEN_EXISTING = 3

  # Seek origin.
  FILE_BEGIN    = 0
  FILE_CURRENT  = 1
  FILE_END      = 2

  # Misc.
  INVALID_HANDLE_VALUE      = -1

  # API.
  @@createFile        = Win32API.new('kernel32', 'CreateFileA',       'PLLLLLL',  'L')
  @@setFilePointerEx  = Win32API.new('kernel32', 'SetFilePointerEx',  'LLLPL',      'L')
  @@readFile          = Win32API.new('kernel32', 'ReadFile',          'LPLPL',    'L')
  @@writeFile         = Win32API.new('kernel32', 'WriteFile',         'LPLPL',    'L')
  @@closeHandle       = Win32API.new('kernel32', 'CloseHandle',       'L',        'L')
  @@getFileSize       = Win32API.new('kernel32', 'GetFileSizeEx',     'LP',       'L')
  @@getLastError      = Win32API.new('kernel32', 'GetLastError',      nil,        'L')

  # Default constructor.
  def initialize(file, access = "r")
    accessOptions = 0
    accessOptions |= GENERIC_READ if access.include?("r")
    accessOptions |= GENERIC_WRITE if access.include?("+")
    @hFile = @@createFile.call(file, accessOptions, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0)
    raise "Couldn't open file #{file}" if @hFile == INVALID_HANDLE_VALUE
    $log.debug("MiqLargeFile<#{object_id}> Opening #{file}, handle 0x#{'%08x' % @hFile}") if $log
  end

  # Alternative initialization.
  def self.open(file, access = "r")
    initialize(file, access)
  end

  def size
    siz = MemoryBuffer.create_quad
    err = @@getFileSize.call(@hFile, siz)
    siz.unpack('Q')[0]
  end

  def seek(offset, whence)
    method = case whence
             when IO::SEEK_SET then FILE_BEGIN
             when IO::SEEK_CUR then FILE_CURRENT
             when IO::SEEK_END then FILE_END
             else raise "Invalid seek method: #{whence}"
             end
    offHi, offLo = offset.divmod(4294967296) # 2 ** 32
    new_pos = MemoryBuffer.create_quad
    res = @@setFilePointerEx.call(@hFile, offLo, offHi, new_pos, method)
    if res == 0
      last_error = @@getLastError.call
      raise "SetFilePointerEx failed - Offset:[#{offset}] method:[#{whence}] Handle:[0x#{'%08x' % @hFile}] GetLastErrorNum:[#{last_error}]"
    end
    new_pos = new_pos.unpack('Q')[0]
    new_pos
  end

  def read(bytes)
    # puts "#{getFilePos}, #{bytes}" if $track_pos
    buf = MemoryBuffer.create(bytes)
    bytesRead = MemoryBuffer.create_long
    res = @@readFile.call(@hFile, buf, bytes, bytesRead, 0)
    bytesRead = bytesRead.unpack('L')[0]
    if bytesRead == 0 && bytes != 0 || res == 0
      last_error = @@getLastError.call
      raise "Read from disk file failed - result:[#{res}] bytesRead:[#{bytesRead}] expected:[#{bytes}] file pointer:[#{getFilePos}] file size:[#{size}] Handle:[0x#{'%08x' % @hFile}] GetLastErrorNum:[#{last_error}]."
    end
    buf = buf[0...bytesRead] if bytesRead != bytes
    buf
  end

  def write(buf, len)
    # NOTE: len must be a double word.
    bytesWritten = MemoryBuffer.create_long
    res = @@writeFile.call(@hFile, buf, len, bytesWritten, 0)
    raise "WriteFile failed" if res == 0
    bytesWritten = bytesWritten.unpack('L')[0]
    raise "Not all data written" if bytesWritten != len
    bytesWritten
  end

  def close
    $log.debug("MiqLargeFile<#{object_id}> Closing handle 0x#{'%08x' % @hFile}") if $log
    h = @hFile
    res = @@closeHandle.call(@hFile)
    @hFile = INVALID_HANDLE_VALUE if res != 0
    return res, h
  end

  def getFilePos
    seek(0, IO::SEEK_CUR)
  end
end