"""Low-level IO operations, for use with file wrappers."""
import io

from django.utils.encoding import force_bytes, force_str


class TextIteratorIO(io.TextIOBase):
    """A dynamically generated TextIO-like object.

    Original code by Matt Joiner <anacrolix@gmail.com> from:

    * http://stackoverflow.com/questions/12593576/
    * https://gist.github.com/anacrolix/3788413

    """

    def __init__(self, iterator):
        #: Iterator/generator for content.
        self._iter = iterator

        #: Internal buffer.
        self._left = ""

    def readable(self):
        return True

    def _read1(self, n=None):
        while not self._left:
            try:
                self._left = next(self._iter)
            except StopIteration:
                break
            else:
                # Make sure we handle text.
                self._left = force_str(self._left)
        ret = self._left[:n]
        self._left = self._left[len(ret) :]
        return ret

    def read(self, n=None):
        """Return content up to ``n`` length."""
        chunks = []
        if n is None or n < 0:
            while True:
                m = self._read1()
                if not m:
                    break
                chunks.append(m)
        else:
            while n > 0:
                m = self._read1(n)
                if not m:
                    break
                n -= len(m)
                chunks.append(m)
        return "".join(chunks)

    def readline(self):
        chunks = []
        while True:
            i = self._left.find("\n")
            if i == -1:
                chunks.append(self._left)
                try:
                    self._left = next(self._iter)
                except StopIteration:
                    self._left = ""
                    break
            else:
                chunks.append(self._left[: i + 1])
                self._left = self._left[i + 1 :]
                break
        return "".join(chunks)


class BytesIteratorIO(io.BytesIO):
    """A dynamically generated BytesIO-like object.

    Original code by Matt Joiner <anacrolix@gmail.com> from:

    * http://stackoverflow.com/questions/12593576/
    * https://gist.github.com/anacrolix/3788413

    """

    def __init__(self, iterator):
        #: Iterator/generator for content.
        self._iter = iterator

        #: Internal buffer.
        self._left = b""

    def readable(self):
        return True

    def _read1(self, n=None):
        while not self._left:
            try:
                self._left = next(self._iter)
            except StopIteration:
                break
            else:
                # Make sure we handle text.
                self._left = force_bytes(self._left)
        ret = self._left[:n]
        self._left = self._left[len(ret) :]
        return ret

    def read(self, n=None):
        """Return content up to ``n`` length."""
        chunks = []
        if n is None or n < 0:
            while True:
                m = self._read1()
                if not m:
                    break
                chunks.append(m)
        else:
            while n > 0:
                m = self._read1(n)
                if not m:
                    break
                n -= len(m)
                chunks.append(m)
        return b"".join(chunks)

    def readline(self):
        chunks = []
        while True:
            i = self._left.find(b"\n")
            if i == -1:
                chunks.append(self._left)
                try:
                    self._left = next(self._iter)
                except StopIteration:
                    self._left = b""
                    break
            else:
                chunks.append(self._left[: i + 1])
                self._left = self._left[i + 1 :]
                break
        return b"".join(chunks)