# coding=utf-8
"""
Download mode implementation.

"""
from __future__ import division
import os
import re
import sys
import mimetypes
import threading
from time import time

from .output import RawStream
from .models import HTTPResponse
from .utils import humanize_bytes
from .compat import urlsplit


PARTIAL_CONTENT = 206


CLEAR_LINE = '\r\033[K'
PROGRESS = (
    '{percentage: 6.2f} %'
    ' {downloaded: >10}'
    ' {speed: >10}/s'
    ' {eta: >8} ETA'
)
PROGRESS_NO_CONTENT_LENGTH = '{downloaded: >10} {speed: >10}/s'
SUMMARY = 'Done. {downloaded} in {time:0.5f}s ({speed}/s)\n'
SPINNER = '|/-\\'


class ContentRangeError(ValueError):
    pass


def parse_content_range(content_range, resumed_from):
    """
    Parse and validate Content-Range header.

    <http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html>

    :param content_range: the value of a Content-Range response header
                          eg. "bytes 21010-47021/47022"
    :param resumed_from: first byte pos. from the Range request header
    :return: total size of the response body when fully downloaded.

    """
    if content_range is None:
        raise ContentRangeError('Missing Content-Range')

    pattern = (
        '^bytes (?P<first_byte_pos>\d+)-(?P<last_byte_pos>\d+)'
        '/(\*|(?P<instance_length>\d+))$'
    )
    match = re.match(pattern, content_range)

    if not match:
        raise ContentRangeError(
            'Invalid Content-Range format %r' % content_range)

    content_range_dict = match.groupdict()
    first_byte_pos = int(content_range_dict['first_byte_pos'])
    last_byte_pos = int(content_range_dict['last_byte_pos'])
    instance_length = (
        int(content_range_dict['instance_length'])
        if content_range_dict['instance_length']
        else None
    )

    # "A byte-content-range-spec with a byte-range-resp-spec whose
    # last- byte-pos value is less than its first-byte-pos value,
    # or whose instance-length value is less than or equal to its
    # last-byte-pos value, is invalid. The recipient of an invalid
    # byte-content-range- spec MUST ignore it and any content
    # transferred along with it."
    if (first_byte_pos >= last_byte_pos
            or (instance_length is not None
                and instance_length <= last_byte_pos)):
        raise ContentRangeError(
            'Invalid Content-Range returned: %r' % content_range)

    if (first_byte_pos != resumed_from
        or (instance_length is not None
            and last_byte_pos + 1 != instance_length)):
        # Not what we asked for.
        raise ContentRangeError(
            'Unexpected Content-Range returned (%r)'
            ' for the requested Range ("bytes=%d-")'
            % (content_range, resumed_from)
        )

    return last_byte_pos + 1


def filename_from_content_disposition(content_disposition):
    """
    Extract and validate filename from a Content-Disposition header.

    :param content_disposition: Content-Disposition value
    :return: the filename if present and valid, otherwise `None`

    """
    # attachment; filename=jkbr-httpie-0.4.1-20-g40bd8f6.tar.gz
    match = re.search('filename=(\S+)', content_disposition)
    if match and match.group(1):
        fn = match.group(1).strip('."')
        if re.match('^[a-zA-Z0-9._-]+$', fn):
            return fn


def filename_from_url(url, content_type):
    fn = urlsplit(url).path.rstrip('/')
    fn = os.path.basename(fn) if fn else 'index'
    if '.' not in fn and content_type:
        content_type = content_type.split(';')[0]
        if content_type == 'text/plain':
            # mimetypes returns '.ksh'
            ext = '.txt'
        else:
            ext = mimetypes.guess_extension(content_type)

        if ext == '.htm':  # Python 3
            ext = '.html'

        if ext:
            fn += ext

    return fn


def get_unique_filename(fn, exists=os.path.exists):
    attempt = 0
    while True:
        suffix = '-' + str(attempt) if attempt > 0 else ''
        if not exists(fn + suffix):
            return fn + suffix
        attempt += 1


class Download(object):

    def __init__(self, output_file=None,
                 resume=False, progress_file=sys.stderr):
        """
        :param resume: Should the download resume if partial download
                       already exists.
        :type resume: bool

        :param output_file: The file to store response body in. If not
                            provided, it will be guessed from the response.
        :type output_file: file

        :param progress_file: Where to report download progress.
        :type progress_file: file

        """
        self._output_file = output_file
        self._resume = resume
        self._resumed_from = 0
        self.finished = False

        self._status = Status()
        self._progress_reporter = ProgressReporter(
            status=self._status,
            output=progress_file
        )

    def pre_request(self, request_headers):
        """Called just before the HTTP request is sent.

        Might alter `request_headers`.

        :type request_headers: dict

        """
        # Disable content encoding so that we can resume, etc.
        request_headers['Accept-Encoding'] = None
        if self._resume:
            bytes_have = os.path.getsize(self._output_file.name)
            if bytes_have:
                # Set ``Range`` header to resume the download
                # TODO: Use "If-Range: mtime" to make sure it's fresh?
                request_headers['Range'] = 'bytes=%d-' % bytes_have
                self._resumed_from = bytes_have

    def start(self, response):
        """
        Initiate and return a stream for `response` body  with progress
        callback attached. Can be called only once.

        :param response: Initiated response object with headers already fetched
        :type response: requests.models.Response

        :return: RawStream, output_file

        """
        assert not self._status.time_started

        try:
            total_size = int(response.headers['Content-Length'])
        except (KeyError, ValueError, TypeError):
            total_size = None

        if self._output_file:
            if self._resume and response.status_code == PARTIAL_CONTENT:
                total_size = parse_content_range(
                    response.headers.get('Content-Range'),
                    self._resumed_from
                )

            else:
                self._resumed_from = 0
                try:
                    self._output_file.seek(0)
                    self._output_file.truncate()
                except IOError:
                    pass  # stdout
        else:
            # TODO: Should the filename be taken from response.history[0].url?
            # Output file not specified. Pick a name that doesn't exist yet.
            fn = None
            if 'Content-Disposition' in response.headers:
                fn = filename_from_content_disposition(
                    response.headers['Content-Disposition'])
            if not fn:
                fn = filename_from_url(
                    url=response.url,
                    content_type=response.headers.get('Content-Type'),
                )
            self._output_file = open(get_unique_filename(fn), mode='a+b')

        self._status.started(
            resumed_from=self._resumed_from,
            total_size=total_size
        )

        stream = RawStream(
            msg=HTTPResponse(response),
            with_headers=False,
            with_body=True,
            on_body_chunk_downloaded=self._chunk_downloaded,
            chunk_size=1024 * 8
        )

        self._progress_reporter.output.write(
            'Downloading %sto "%s"\n' % (
                (humanize_bytes(total_size) + ' '
                 if total_size is not None
                 else ''),
                self._output_file.name
            )
        )
        self._progress_reporter.report()

        return stream, self._output_file

    def finish(self):
        assert not self.finished
        self.finished = True
        self._status.finished()

    def failed(self):
        self.finish()
        self._progress_reporter.stop()

    @property
    def interrupted(self):
        return (
            self.finished
            and self._status.total_size
            and self._status.total_size != self._status.downloaded
        )

    def _chunk_downloaded(self, chunk):
        """
        A download progress callback.

        :param chunk: A chunk of response body data that has just
                      been downloaded and written to the output.
        :type chunk: bytes

        """
        self._status.chunk_downloaded(len(chunk))


class Status(object):
    """Holds details about the downland status."""

    def __init__(self):
        self.downloaded = 0
        self.total_size = None
        self.resumed_from = 0
        self.time_started = None
        self.time_finished = None

    def started(self, resumed_from=0, total_size=None):
        assert self.time_started is None
        if total_size is not None:
            self.total_size = total_size
        self.downloaded = self.resumed_from = resumed_from
        self.time_started = time()

    def chunk_downloaded(self, size):
        assert self.time_finished is None
        self.downloaded += size

    @property
    def has_finished(self):
        return self.time_finished is not None

    def finished(self):
        assert self.time_started is not None
        assert self.time_finished is None
        self.time_finished = time()


class ProgressReporter(object):
    """
    Reports download progress based on its status.

    Uses threading to periodically update the status (speed, ETA, etc.).

    """
    def __init__(self, status, output, tick=.1, update_interval=1):
        """

        :type status: Status
        :type output: file
        """
        self.status = status
        self.output = output
        self._tick = tick
        self._update_interval = update_interval
        self._spinner_pos = 0
        self._status_line = ''
        self._prev_bytes = 0
        self._prev_time = time()
        self._stop = False

    def stop(self):
        """Stop reporting on next tick."""
        self._stop = True

    def report(self):
        if self._stop:
            return
        if self.status.has_finished:
            self.sum_up()
        else:
            self.report_speed()
            threading.Timer(self._tick, self.report).start()

    def report_speed(self):

        now = time()

        if now - self._prev_time >= self._update_interval:
            downloaded = self.status.downloaded
            try:
                speed = ((downloaded - self._prev_bytes)
                         / (now - self._prev_time))
            except ZeroDivisionError:
                speed = 0

            if not self.status.total_size:
                self._status_line = PROGRESS_NO_CONTENT_LENGTH.format(
                    downloaded=humanize_bytes(downloaded),
                    speed=humanize_bytes(speed),
                )
            else:
                try:
                    percentage = downloaded / self.status.total_size * 100
                except ZeroDivisionError:
                    percentage = 0

                if not speed:
                    eta = '-:--:--'
                else:
                    s = int((self.status.total_size - downloaded) / speed)
                    h, s = divmod(s, 60 * 60)
                    m, s = divmod(s, 60)
                    eta = '{}:{:0>2}:{:0>2}'.format(h, m, s)

                self._status_line = PROGRESS.format(
                    percentage=percentage,
                    downloaded=humanize_bytes(downloaded),
                    speed=humanize_bytes(speed),
                    eta=eta,
                )

            self._prev_time = now
            self._prev_bytes = downloaded

        self.output.write(
            CLEAR_LINE
            + ' '
            + SPINNER[self._spinner_pos]
            + ' '
            + self._status_line
        )
        self.output.flush()

        self._spinner_pos = (self._spinner_pos + 1
                             if self._spinner_pos + 1 != len(SPINNER)
                             else 0)

    def sum_up(self):
        actually_downloaded = (self.status.downloaded
                               - self.status.resumed_from)
        time_taken = self.status.time_finished - self.status.time_started

        self.output.write(CLEAR_LINE)
        self.output.write(SUMMARY.format(
            downloaded=humanize_bytes(actually_downloaded),
            total=(self.status.total_size
                   and humanize_bytes(self.status.total_size)),
            speed=humanize_bytes(actually_downloaded / time_taken),
            time=time_taken,
        ))
        self.output.flush()