"""Wrapper for s3 object to act like a proper file."""
import io


class S3File(io.RawIOBase):
    def __init__(self, s3_object):
        self.s3_object = s3_object
        self.position = 0

    def __repr__(self):
        return "<%s s3_object=%r>" % (type(self).__name__, self.s3_object)

    @property
    def size(self):
        return self.s3_object.content_length

    def tell(self):
        return self.position

    def seek(self, offset, whence=io.SEEK_SET):
        if whence == io.SEEK_SET:
            self.position = offset
        elif whence == io.SEEK_CUR:
            self.position += offset
        elif whence == io.SEEK_END:
            self.position = self.size + offset
        else:
            raise ValueError("invalid whence (%r, should be %d, %d, %d)" % (
                whence, io.SEEK_SET, io.SEEK_CUR, io.SEEK_END
            ))

        return self.position

    def seekable(self):
        return True

    def read(self, size=-1):
        if size == -1:
            # Read to the end of the file
            # range_header = "bytes=%d-" % self.position
            self.seek(offset=0, whence=io.SEEK_END)
            return self.s3_object.get()["Body"].read()
        else:
            new_position = self.position + size

            # If we're going to read beyond the end of the object, return
            # the entire object.
            if new_position >= self.size:
                return self.read()

            range_header = "bytes=%d-%d" % (self.position, new_position - 1)
            self.seek(offset=size, whence=io.SEEK_CUR)

            return self.s3_object.get(Range=range_header)["Body"].read()

    def readable(self):
        return True