import random
import sys
import io


class MultipartDataGenerator(object):
    def __init__(self, chunk_size=1028):
        self.data = io.BytesIO()
        self.line_break = "\r\n"
        self.boundary = self._initialize_boundary()
        self.chunk_size = chunk_size

    def add_params(self, params):
        for key, value in params.iteritems():
            if value is None:
                continue

            self._write(self.param_header())
            self._write(self.line_break)
            if hasattr(value, 'read'):
                self._write("Content-Disposition: form-data; name=\"")
                self._write(key)
                self._write("\"; filename=\"")
                self._write(value.name)
                self._write("\"")
                self._write(self.line_break)
                self._write("Content-Type: application/octet-stream")
                self._write(self.line_break)
                self._write(self.line_break)

                self._write_file(value)
            else:
                self._write("Content-Disposition: form-data; name=\"")
                self._write(key)
                self._write("\"")
                self._write(self.line_break)
                self._write(self.line_break)
                self._write(value)

            self._write(self.line_break)

    def param_header(self):
        return "--%s" % self.boundary

    def get_post_data(self):
        self._write("--%s--" % (self.boundary,))
        self._write(self.line_break)
        return self.data.getvalue()

    def _write(self, value):
        if sys.version_info < (3,):
            binary_type = str
            text_type = unicode
        else:
            binary_type = bytes
            text_type = str

        if isinstance(value, binary_type):
            array = bytearray(value)
        elif isinstance(value, text_type):
            array = bytearray(value, encoding='utf-8')
        else:
            raise TypeError("unexpected type: {value_type}"
                            .format(value_type=type(value)))

        self.data.write(array)

    def _write_file(self, f):
        while True:
            file_contents = f.read(self.chunk_size)
            if not file_contents:
                break
            self._write(file_contents)

    def _initialize_boundary(self):
        return random.randint(0, 2**63)