Added a diva playlist downloader

PFERD/diva.py

@@ -0,0 +1,133 @@
+import logging
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any, Callable, List, Optional
+
+import requests
+
+from .logging import FatalException, PrettyLogger
+from .organizer import Organizer
+from .tmp_dir import TmpDir
+from .transform import Transformable
+from .utils import stream_to_path
+
+LOGGER = logging.getLogger(__name__)
+PRETTY = PrettyLogger(LOGGER)
+
+
+@dataclass
+class DivaDownloadInfo(Transformable):
+    """
+    Information about a DIVA video
+    """
+    url: str
+
+
+DivaDownloadStrategy = Callable[[Organizer, DivaDownloadInfo], bool]
+
+
+def diva_download_new(organizer: Organizer, info: DivaDownloadInfo) -> bool:
+    """
+    Accepts only new files.
+    """
+    resolved_file = organizer.resolve(info.path)
+    if not resolved_file.exists():
+        return True
+    PRETTY.ignored_file(info.path, "local file exists")
+    return False
+
+
+class DivaPlaylistCrawler:
+    # pylint: disable=too-few-public-methods
+    """
+    A crawler for DIVA playlists.
+    """
+
+    _BASE_URL = "https://mediaservice.bibliothek.kit.edu/asset/collection.json"
+
+    def __init__(self, playlist_id: str):
+        self._id = playlist_id
+
+    def crawl(self) -> List[DivaDownloadInfo]:
+        """
+        Crawls the playlist given in the constructor.
+        """
+        response = requests.get(self._BASE_URL, params={"collection": self._id})
+        if response.status_code != 200:
+            raise FatalException(f"Server returned status {response.status_code}.")
+
+        body = response.json()
+
+        if body["error"]:
+            raise FatalException(f"Server returned error {body['error']!r}.")
+
+        result = body["result"]
+
+        if result["resultCount"] > result["pageSize"]:
+            PRETTY.warning("Did not receive all results, some will be missing")
+
+        download_infos: List[DivaDownloadInfo] = []
+
+        for video in result["resultList"]:
+            title = video["title"]
+            collection_title = self._follow_path(["collection", "title"], video)
+            url = self._follow_path(
+                ["resourceList", "derivateList", "mp4", "url"],
+                video
+            )
+
+            if url and collection_title and title:
+                path = Path(collection_title, title + ".mp4")
+                download_infos.append(DivaDownloadInfo(path, url))
+            else:
+                PRETTY.warning(f"Incomplete video found: {title!r} {collection_title!r} {url!r}")
+
+        return download_infos
+
+    @staticmethod
+    def _follow_path(path: List[str], obj: Any) -> Optional[Any]:
+        """
+        Follows a property path through an object, bailing at the first None.
+        """
+        current = obj
+        for path_step in path:
+            if path_step in current:
+                current = current[path_step]
+            else:
+                return None
+        return current
+
+
+class DivaDownloader:
+    """
+    A downloader for DIVA videos.
+    """
+
+    def __init__(self, tmp_dir: TmpDir, organizer: Organizer, strategy: DivaDownloadStrategy):
+        self._tmp_dir = tmp_dir
+        self._organizer = organizer
+        self._strategy = strategy
+        self._session = requests.session()
+
+    def download_all(self, infos: List[DivaDownloadInfo]) -> None:
+        """
+        Download multiple files one after the other.
+        """
+        for info in infos:
+            self.download(info)
+
+    def download(self, info: DivaDownloadInfo) -> None:
+        """
+        Download a single file.
+        """
+        if not self._strategy(self._organizer, info):
+            self._organizer.mark(info.path)
+            return
+
+        with self._session.get(info.url, stream=True) as response:
+            if response.status_code == 200:
+                tmp_file = self._tmp_dir.new_path()
+                stream_to_path(response, tmp_file)
+                self._organizer.accept_file(tmp_file, info.path)
+            else:
+                PRETTY.warning(f"Could not download file, got response {response.status_code}")