chore: Halkyon Learn moves into apps/learn

Its server, client, app and curator, and the tools that write its
assets (maps, Anki fixtures, icons), as they are; paths are fixed in
the commits that follow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/tool/anki/make_fixtures.py

@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+"""Builds the Anki packages the app's import tests read, with Anki itself.
+
+The `anki` Python package is Anki's own backend, so the packages are exactly
+what Anki exports: one collection, exported in the latest format, in the
+legacy format ("Support older Anki versions"), and repacked the way Anki
+before 2.1.50 wrote packages (only `collection.anki2`, no `meta`).
+
+The collection holds, on purpose:
+- a Basic note with bold text, a line break, an image, and two tags, one of
+  them hierarchical (deck "Japanese");
+- a "Basic (and reversed card)" note with a sound, both its cards answered,
+  one of them first wrong (deck "Japanese::Animals");
+- a Cloze note with two deletions, never reviewed;
+- a Basic note with a list and HTML entities ("Japanese::Animals");
+- a manual reschedule in the review log (no answer).
+
+A second deck (`anki_furigana*.apkg`) has a note type that shows its
+Reading through Anki's furigana filter, and the same text in its Expression.
+
+Run from the repository root, in a virtual environment with Anki's package:
+
+    python3 -m venv /tmp/anki && /tmp/anki/bin/pip install anki==26.9.3
+    /tmp/anki/bin/python tool/anki/make_fixtures.py
+
+It rewrites halkyon_learn_flutter/test/feature/anki/fixtures/*.apkg. Ids and
+times differ on every run; the tests don't depend on them.
+"""
+
+import io
+import os
+import tempfile
+import zipfile
+from pathlib import Path
+
+from anki.collection import Collection, ExportAnkiPackageOptions
+from anki.decks import DeckId
+
+OUT = Path("halkyon_learn_flutter/test/feature/anki/fixtures")
+
+# Valid files, so the packages also serve to try the import by hand: a 1x1
+# PNG (one orange pixel), and 0.26 s of silence as an MP3 (ten MPEG-1 Layer
+# III frames, 128 kbit/s, 44.1 kHz, mono, whose zeroed side information
+# decodes to silence).
+PNG = bytes.fromhex(
+    "89504e470d0a1a0a0000000d49484452000000010000000108060000001f15c489"
+    "0000000d49444154789c63f8dfc0f01f000680027f104c1be10000000049454e44ae426082"
+)
+MP3 = (bytes.fromhex("fffb90c4") + bytes(413)) * 10
+
+AGAIN, GOOD, EASY = 0, 2, 3
+
+
+def main():
+    OUT.mkdir(parents=True, exist_ok=True)
+    with tempfile.TemporaryDirectory() as work:
+        col = Collection(os.path.join(work, "collection.anki2"))
+        col.media.write_data("cat.png", PNG)
+        col.media.write_data("neko.mp3", MP3)
+        japanese = col.decks.id("Japanese")
+        animals = col.decks.id("Japanese::Animals")
+
+        def add(model, deck, fields, tags):
+            note = col.new_note(col.models.by_name(model))
+            for i, field in enumerate(fields):
+                note.fields[i] = field
+            note.tags = tags
+            col.add_note(note, DeckId(deck))
+            return note
+
+        def answer(card_id, rating):
+            card = col.get_card(card_id)
+            card.start_timer()
+            states = col._backend.get_scheduling_states(card.id)
+            col.sched.answer_card(
+                col.sched.build_answer(card=card, states=states, rating=rating)
+            )
+
+        cat = add(
+            "Basic",
+            japanese,
+            ["<b>猫</b>", 'cat<br>a pet<img src="cat.png">'],
+            ["animal", "JLPT::N5"],
+        )
+        dog = add(
+            "Basic (and reversed card)",
+            animals,
+            ["犬 [sound:neko.mp3]", "dog"],
+            ["animal"],
+        )
+        add("Cloze", japanese, ["{{c1::Tokyo}} is the capital of {{c2::Japan::country}}", "extra"], [])
+        add(
+            "Basic",
+            animals,
+            ["<ul><li>one</li><li>two</li></ul>", "&lt;tag&gt; &amp; more"],
+            [],
+        )
+
+        answer(cat.card_ids()[0], EASY)
+        forward, reverse = sorted(dog.card_ids(), key=lambda c: col.get_card(c).ord)
+        answer(forward, AGAIN)
+        answer(forward, GOOD)
+        answer(reverse, EASY)
+        col.sched.set_due_date([cat.card_ids()[0]], "5")
+
+        for legacy, name in [(False, "anki_latest.apkg"), (True, "anki_legacy.apkg")]:
+            col.export_anki_package(
+                out_path=str(OUT / name),
+                options=ExportAnkiPackageOptions(
+                    with_scheduling=True,
+                    with_deck_configs=False,
+                    with_media=True,
+                    legacy=legacy,
+                ),
+                limit=None,
+            )
+        col.close()
+
+    # Before 2.1.50: the collection as collection.anki2, no meta, no stub.
+    with zipfile.ZipFile(OUT / "anki_legacy.apkg") as legacy:
+        out = io.BytesIO()
+        with zipfile.ZipFile(out, "w", zipfile.ZIP_DEFLATED) as old:
+            for info in legacy.infolist():
+                if info.filename in ("meta", "collection.anki2"):
+                    continue
+                name = "collection.anki2" if info.filename == "collection.anki21" else info.filename
+                old.writestr(name, legacy.read(info.filename))
+    (OUT / "anki_before_2_1_50.apkg").write_bytes(out.getvalue())
+
+
+def furigana():
+    """A deck whose note type shows a field through Anki's furigana filter,
+    in the latest format and the legacy one: the import turns that field's
+    漢字[かんじ] into readings, and leaves the same text in another field."""
+    with tempfile.TemporaryDirectory() as work:
+        col = Collection(os.path.join(work, "collection.anki2"))
+        models = col.models
+        model = models.new("Japanese (furigana)")
+        for name in ("Expression", "Reading", "Meaning"):
+            models.add_field(model, models.new_field(name))
+        template = models.new_template("Recognition")
+        template["qfmt"] = "{{Expression}}"
+        template["afmt"] = "{{FrontSide}}<hr id=answer>{{furigana:Reading}}<br>{{Meaning}}"
+        models.add_template(model, template)
+        models.add(model)
+        note = col.new_note(col.models.by_name("Japanese (furigana)"))
+        note.fields[0] = "日本語[にほんご]"
+        note.fields[1] = "日本語[にほんご]を 勉強[べんきょう]する"
+        note.fields[2] = "to study Japanese"
+        col.add_note(note, DeckId(col.decks.id("Furigana")))
+        for legacy, name in [
+            (False, "anki_furigana.apkg"),
+            (True, "anki_furigana_legacy.apkg"),
+        ]:
+            col.export_anki_package(
+                out_path=str(OUT / name),
+                options=ExportAnkiPackageOptions(
+                    with_scheduling=False,
+                    with_deck_configs=False,
+                    with_media=False,
+                    legacy=legacy,
+                ),
+                limit=None,
+            )
+        col.close()
+
+
+if __name__ == "__main__":
+    main()
+    furigana()