from __future__ import unicode_literals

from .fragment import FragmentFD
from ..compat import compat_urllib_error
from ..utils import (
	DownloadError,
	urljoin,
)


class DashSegmentsFD(FragmentFD):
	"""
  Download segments in a DASH manifest
  """

	FD_NAME = 'dashsegments'

	def real_download(self, filename, info_dict):
		fragment_base_url = info_dict.get('fragment_base_url')
		fragments = info_dict['fragments'][:1] if self.params.get(
			'test', False) else info_dict['fragments']

		ctx = {
			'filename': filename,
			'total_frags': len(fragments),
		}

		self._prepare_and_start_frag_download(ctx)

		fragment_retries = self.params.get('fragment_retries', 0)
		skip_unavailable_fragments = self.params.get('skip_unavailable_fragments', True)

		frag_index = 0
		for i, fragment in enumerate(fragments):
			frag_index += 1
			if frag_index <= ctx['fragment_index']:
				continue
			# In DASH, the first segment contains necessary headers to
			# generate a valid MP4 file, so always abort for the first segment
			fatal = i == 0 or not skip_unavailable_fragments
			count = 0
			while count <= fragment_retries:
				try:
					fragment_url = fragment.get('url')
					if not fragment_url:
						assert fragment_base_url
						fragment_url = urljoin(fragment_base_url, fragment['path'])
					success, frag_content = self._download_fragment(ctx, fragment_url, info_dict)
					if not success:
						return False
					self._append_fragment(ctx, frag_content)
					break
				except compat_urllib_error.HTTPError as err:
					# YouTube may often return 404 HTTP error for a fragment causing the
					# whole download to fail. However if the same fragment is immediately
					# retried with the same request data this usually succeeds (1-2 attemps
					# is usually enough) thus allowing to download the whole file successfully.
					# To be future-proof we will retry all fragments that fail with any
					# HTTP error.
					count += 1
					if count <= fragment_retries:
						self.report_retry_fragment(err, frag_index, count, fragment_retries)
				except DownloadError:
					# Don't retry fragment if error occurred during HTTP downloading
					# itself since it has own retry settings
					if not fatal:
						self.report_skip_fragment(frag_index)
						break
					raise

			if count > fragment_retries:
				if not fatal:
					self.report_skip_fragment(frag_index)
					continue
				self.report_error('giving up after %s fragment retries' % fragment_retries)
				return False

		self._finish_frag_download(ctx)

		return True
