feat(settings): choose between Save As and saving into a folder

Downloading a selection of twenty files meant twenty Save As dialogs,
which is the wrong answer for the feature that had just been built.
Settings → Downloads now offers saving automatically, and that is the
default; asking every time stays available for people who want it.

The correction worth recording: a web page cannot be given a filesystem
path and cannot read one either. There is no ~/Downloads to configure and
nothing to type, on any operating system — which is also why none of this
will need changing on Windows. What a browser grants is a handle to a
folder the user picked in a dialog, so that is what the setting keeps:
picked once, stored in IndexedDB, re-confirmed once a session because the
grant comes back as a claim rather than a permission. Where no folder has
been granted, and in Firefox and Safari where none can be, files go to
the browser's own download folder — which on most machines is the folder
that was meant all along.

Automatic saving has one risk a dialog does not: it can silently replace
a file. It does not — a taken name gets a suffix before the extension,
`clip (2).mp4`, so a download folder does not fill up with files the
system no longer recognises. That, and the default, are what
test_downloads.py pins.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 97 insertions, 0 deletions

diff --git a/packages/meshbay-hub/tests/test_downloads.py b/packages/meshbay-hub/tests/test_downloads.py
new file mode 100644
index 0000000..cc4fdd1
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_downloads.py
@@ -0,0 +1,97 @@
+"""
+Where downloads are written.
+
+The module is mostly browser plumbing — a directory handle from a picker, kept
+in IndexedDB — but two pieces decide behaviour and can be checked here: that
+automatic is the default, and that writing into the same folder repeatedly does
+not quietly replace what is already there. The second one is the whole risk of
+the automatic mode: a Save As dialog warns you about a collision, and a folder
+you never look at does not.
+"""
+
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+STATIC = Path(__file__).resolve().parents[1] / "src" / "meshbay_hub" / "static"
+DOWNLOADS = STATIC / "downloads.js"
+
+pytestmark = pytest.mark.skipif(
+    shutil.which("node") is None or not DOWNLOADS.exists(),
+    reason="node or the SPA sources are not available")
+
+
+def _run(body, tmp_path):
+    module = tmp_path / "downloads.mjs"
+    module.write_text(DOWNLOADS.read_text())
+    script = tmp_path / "case.mjs"
+    script.write_text(
+        # A localStorage good enough for a preference, so the module can be
+        # imported outside a browser at all.
+        "const store = new Map();\n"
+        "globalThis.localStorage = {\n"
+        "  getItem: k => (store.has(k) ? store.get(k) : null),\n"
+        "  setItem: (k, v) => store.set(k, String(v)),\n"
+        "};\n"
+        f"const M = await import('{module.as_posix()}');\n"
+        "const out = [];\n"
+        "const say = (...a) => out.push(...a);\n"
+        f"{body}\n"
+        "console.log(JSON.stringify(out));\n")
+    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
+    assert proc.returncode == 0, proc.stderr
+    return json.loads(proc.stdout)
+
+
+def test_saving_automatically_is_the_default(tmp_path):
+    """
+    Grouped downloads are the reason this setting exists: twelve files must not
+    mean twelve dialogs unless someone asked for that.
+    """
+    assert _run("say(M.getMode());", tmp_path) == ["auto"]
+
+
+def test_the_choice_is_remembered_and_nothing_else_is_accepted(tmp_path):
+    result = _run("""
+M.setMode('ask');   say(M.getMode());
+M.setMode('auto');  say(M.getMode());
+M.setMode('nonsense'); say(M.getMode());
+""", tmp_path)
+    assert result == ["ask", "auto", "auto"]
+
+
+def test_a_second_copy_does_not_replace_the_first(tmp_path):
+    result = _run("""
+const taken = new Set(['clip.mp4', 'clip (2).mp4', 'notes']);
+const exists = async n => taken.has(n);
+say(await M.freeName('clip.mp4', exists));
+say(await M.freeName('other.mp4', exists));
+say(await M.freeName('notes', exists));
+say(await M.freeName('archive.tar.gz', exists));
+""", tmp_path)
+    assert result == [
+        "clip (3).mp4",      # (2) was taken as well
+        "other.mp4",         # free: left alone
+        "notes (2)",         # no extension to keep
+        "archive.tar.gz",    # free, and the double extension is not mangled
+    ]
+
+
+def test_the_suffix_goes_before_the_extension(tmp_path):
+    """
+    "clip.mp4 (2)" would stop being a video as far as the operating system is
+    concerned, which is how a download folder ends up full of files nothing opens.
+    """
+    result = _run("""
+say(await M.freeName('clip.mp4', async () => false));
+say(await M.freeName('clip.mp4', async n => n === 'clip.mp4'));
+""", tmp_path)
+    assert result == ["clip.mp4", "clip (2).mp4"]
+
+
+def test_a_browser_without_the_api_reports_it(tmp_path):
+    """`SUPPORTED` decides whether Settings offers a choice or an explanation."""
+    assert _run("say(M.SUPPORTED);", tmp_path) == [False]