feat(yt): pull cookies from firefox dev edition, firefox, then chrome

age/login-gated videos need browser cookies to download.
`ydl_opts` becomes a computed_field that picks the first available source.

src/music/commands/download.py

@@ -1,12 +1,13 @@
 import asyncio
+import glob
 import os
 import re
 from pathlib import Path
-from typing import ClassVar
 
 from pydantic_settings import CliImplicitFlag, CliPositionalArg
 import structlog
 import yt_dlp
+import yt_dlp.cookies
 from mutagen.easyid3 import EasyID3
 from pydantic import Field, computed_field
 from shazamio import Shazam
@@ -73,22 +74,24 @@ def current_quarter() -> Path:
     return Path().home() / "Music" / f"{date.quarter}_{date.year}"
 
 
+def _cookiesfrombrowser() -> tuple | None:
+    """First available cookies source: firefox dev edition, firefox, then chrome."""
+    for root in yt_dlp.cookies._firefox_browser_dirs():
+        # dev edition lives in a randomly-prefixed dir, so pass an absolute path
+        matches = glob.glob(os.path.join(root, "*.dev-edition-default"))
+        if matches:
+            return ("firefox", matches[0], None, None)
+    if any(yt_dlp.cookies._firefox_cookie_dbs(yt_dlp.cookies._firefox_browser_dirs())):
+        return ("firefox", None, None, None)
+    return ("chrome", None, None, None)
+
+
 class YtDownload(Command):
     """
     download a youtube song from {URL} to current quarter dir.
     """
 
     url: CliPositionalArg[str] = Field(description="youtube url to download")
-    ydl_opts: ClassVar = {
-        "format": "mp3/bestaudio/best",
-        "postprocessors": [
-            {
-                "key": "FFmpegExtractAudio",
-                "preferredcodec": "mp3",
-            }
-        ],
-        "remote_components": ["ejs:github"],
-    }
     parents: CliImplicitFlag[bool] = Field(
         default=True, description="create the parent dirs if not exists"
     )
@@ -99,6 +102,24 @@ class YtDownload(Command):
         date = DateParse()
         return Path().home() / "Music" / f"{date.quarter}_{date.year}"
 
+    @computed_field()
+    @property
+    def ydl_opts(self) -> dict:
+        opts = {
+            "format": "mp3/bestaudio/best",
+            "postprocessors": [
+                {
+                    "key": "FFmpegExtractAudio",
+                    "preferredcodec": "mp3",
+                }
+            ],
+            "remote_components": ["ejs:github"],
+        }
+        cookies = _cookiesfrombrowser()
+        if cookies is not None:
+            opts["cookiesfrombrowser"] = cookies
+        return opts
+
     def run(self) -> None:
         os.chdir(Path.home() / "Downloads")
         with yt_dlp.YoutubeDL(self.ydl_opts) as ydl: