Fix indentation and return modified line numbers.

        Line numbers are indexed at 1.

def run(self, indent_size=DEFAULT_INDENT_SIZE):
        """Fix indentation and return modified line numbers.

        Line numbers are indexed at 1.

        """
        if indent_size < 1:
            return self.input_text

        try:
            stats = _reindent_stats(tokenize.generate_tokens(self.getline))
        except (SyntaxError, tokenize.TokenError):
            return self.input_text
        # Remove trailing empty lines.
        lines = self.lines
        # Sentinel.
        stats.append((len(lines), 0))
        # Map count of leading spaces to # we want.
        have2want = {}
        # Program after transformation.
        after = []
        # Copy over initial empty lines -- there's nothing to do until
        # we see a line with *something* on it.
        i = stats[0][0]
        after.extend(lines[1:i])
        for i in range(len(stats) - 1):
            thisstmt, thislevel = stats[i]
            nextstmt = stats[i + 1][0]
            have = _leading_space_count(lines[thisstmt])
            want = thislevel * indent_size
            if want < 0:
                # A comment line.
                if have:
                    # An indented comment line. If we saw the same
                    # indentation before, reuse what it most recently
                    # mapped to.
                    want = have2want.get(have, -1)
                    if want < 0:
                        # Then it probably belongs to the next real stmt.
                        for j in range(i + 1, len(stats) - 1):
                            jline, jlevel = stats[j]
                            if jlevel >= 0:
                                if have == _leading_space_count(lines[jline]):
                                    want = jlevel * indent_size
                                break
                    # Maybe it's a hanging comment like this one,
                    if want < 0:
                        # in which case we should shift it like its base
                        # line got shifted.
                        for j in range(i - 1, -1, -1):
                            jline, jlevel = stats[j]
                            if jlevel >= 0:
                                want = (have + _leading_space_count(
                                        after[jline - 1]) -
                                        _leading_space_count(lines[jline]))
                                break
                    if want < 0:
                        # Still no luck -- leave it alone.
                        want = have
                else:
                    want = 0
            assert want >= 0
            have2want[have] = want
            diff = want - have
            if diff == 0 or have == 0:
                after.extend(lines[thisstmt:nextstmt])
            else:
                for line_number, line in enumerate(lines[thisstmt:nextstmt],
                                                   start=thisstmt):
                    if line_number in self.string_content_line_numbers:
                        after.append(line)
                    elif diff > 0:
                        if line == '\n':
                            after.append(line)
                        else:
                            after.append(' ' * diff + line)
                    else:
                        remove = min(_leading_space_count(line), -diff)
                        after.append(line[remove:])

        return ''.join(after)