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"""Utilities to generate source codes."""

__author__ = "hidehiko"

import struct
import types


def ToCppStringLiteral(s):
  """Returns C-style string literal, or NULL if given s is None."""
  if s is None:
    return 'NULL'

  if all(0x20 <= ord(c) <= 0x7E for c in s):
    # All characters are in ascii code.
    return '"%s"' % s.replace('\\', r'\\').replace('"', r'\"')
  else:
    # One or more characters are non-ascii.
    return '"%s"' % ''.join(r'\x%02X' % ord(c) for c in s)


def FormatWithCppEscape(format_text, *args):
  """Returns a string filling format with args."""
  literal_list = []
  for arg in args:
    if isinstance(arg, (types.StringType, types.NoneType)):
      arg = ToCppStringLiteral(arg)
    literal_list.append(arg)

  return format_text % tuple(literal_list)


def WriteCppDataArray(data, variable_name, target_compiler, stream):
  """Format data into C++ style array.

  Visual C++ does not support string literals longer than 65535 characters
  so integer arrays (e.g. arrays of uint64) are used to represent byte arrays
  on Windows.

  The generated code looks like:
    const uint64 kVAR_data_wordtype[] = {
        0x0123456789ABCDEF, ...
    };
    const char * const kVAR_data =
        reinterpret_cast<const char *>(kVAR_data_wordtype);
    const size_t kVAR_size = 123;

  This implementation works well with other toolchains, too, but we use
  string literals for other toolchains.

  The generated code with a string literal looks like:
    const char kVAR_data[] =
        "\\x12\\x34\\x56\\x78...";
    const size_t kVAR_size = 123;

  Args:
    data: original data to be formatted.
    variable_name: the core name of variables.
    target_compiler: the target compiler which will compile the formatted
      code.
    stream: output stream.
  """

  # To accept "target_compiler = None", check taget_compiler itself first.
  if target_compiler and target_compiler.startswith('msvs'):
    stream.write('const uint64 k%s_data_wordtype[] = {\n' % variable_name)

    for word_index in xrange(0, len(data), 8):
      word_chunk = data[word_index:word_index + 8].ljust(8, '\x00')
      stream.write('0x%016X, ' % struct.unpack('<Q', word_chunk))
      if (word_index / 8) % 4 == 3:
        # Line feed for every 4 elements.
        stream.write('\n')

    stream.write('};\n')
    stream.write(
        'const char * const k%s_data = '
        'reinterpret_cast<const char *>(k%s_data_wordtype);\n' % (
            variable_name, variable_name))
  else:
    stream.write('const char k%s_data[] =\n' % variable_name)
    # Output 16bytes per line.
    chunk_size = 16
    for index in xrange(0, len(data), chunk_size):
      chunk = data[index:index + chunk_size]
      stream.write('"')
      stream.writelines(r'\x%02X' % ord(c) for c in chunk)
      stream.write('"\n')
    stream.write(';\n')

  stream.write('const size_t k%s_size = %d;\n' % (variable_name, len(data)))


def ToJavaStringLiteral(codepoint):
  """Returns string literal with surrogate pair support."""
  utf16_string = unichr(codepoint).encode('utf-16be')
  if len(utf16_string) == 2:
    (u0, l0) = utf16_string
    return r'"\u%02X%02X"' % (ord(u0), ord(l0))
  else:
    (u0, l0, u1, l1) = utf16_string
    return r'"\u%02X%02X\u%02X%02X"' % (ord(u0), ord(l0), ord(u1), ord(l1))


def SkipLineComment(stream, comment_prefix='#'):
  """Skips line comments from stream."""
  for line in stream:
    stripped_line = line.strip()
    if stripped_line and not stripped_line.startswith(comment_prefix):
      yield line.rstrip('\n')


def ParseColumnStream(stream, num_column=None, delimiter=None):
  """Returns parsed columns read from stream."""
  if num_column is None:
    for line in stream:
      yield line.rstrip('\n').split(delimiter)
  else:
    for line in stream:
      yield line.rstrip('\n').split(delimiter)[:num_column]


def SelectColumn(stream, column_index):
  """Returns the tuple specified by the column_index from the tuple stream."""
  for columns in stream:
    yield tuple(columns[i] for i in column_index)


def SplitChunk(iterable, n):
  """Splits sequence to consecutive n-element chunks.

  Quite similar to grouper in itertools section of python manual,
  but slightly different if len(iterable) is not factor of n.
  grouper extends the last chunk to make it an n-element chunk by adding
  appropriate value, but this returns truncated chunk.
  """
  for index in xrange(0, len(iterable), n):
    yield iterable[index:index + n]