From e4ae41340f4bc8b91a479bccc610cc9af81b210b Mon Sep 17 00:00:00 2001
From: Arthur Milchior <Arthur@Milchior.fr>
Date: Fri, 6 Mar 2020 16:25:02 +0100
Subject: [PATCH] Hook to decide whether a note should be added.

---
 qt/aqt/addcards.py       |  6 +++++-
 qt/aqt/gui_hooks.py      | 39 +++++++++++++++++++++++++++++++++++++++
 qt/tools/genhooks_gui.py | 12 ++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/qt/aqt/addcards.py b/qt/aqt/addcards.py
index be6308e30..d2adc2966 100644
--- a/qt/aqt/addcards.py
+++ b/qt/aqt/addcards.py
@@ -167,8 +167,12 @@ class AddCards(QDialog):
     def addNote(self, note) -> Optional[Note]:
         note.model()["did"] = self.deckChooser.selectedId()
         ret = note.dupeOrEmpty()
+        rejection = None
         if ret == 1:
-            showWarning(_("The first field is empty."), help="AddItems#AddError")
+            rejection = _("The first field is empty.")
+        rejection = gui_hooks.add_card_accepts(rejection, note)
+        if rejection is not None:
+            showWarning(rejection, help="AddItems#AddError")
             return None
         if "{{cloze:" in note.model()["tmpls"][0]["qfmt"]:
             if not self.mw.col.models._availClozeOrds(
diff --git a/qt/aqt/gui_hooks.py b/qt/aqt/gui_hooks.py
index eed241f7e..7262d2198 100644
--- a/qt/aqt/gui_hooks.py
+++ b/qt/aqt/gui_hooks.py
@@ -23,6 +23,45 @@ from aqt.qt import QDialog, QMenu
 # @@AUTOGEN@@
 
 
+class _AddCardAcceptsFilter:
+    """Decides whether the note should be added to the collection or
+        not. It is assumed to come from the addCards window.
+
+        reason_to_already_reject is the first reason to reject that
+        was found, or None. If your filter wants to reject, it should
+        replace return the reason to reject. Otherwise return the
+        input."""
+
+    _hooks: List[Callable[[Optional[str], "anki.notes.Note"], Optional[str]]] = []
+
+    def append(
+        self, cb: Callable[[Optional[str], "anki.notes.Note"], Optional[str]]
+    ) -> None:
+        """(reason_to_already_reject: Optional[str], note: anki.notes.Note)"""
+        self._hooks.append(cb)
+
+    def remove(
+        self, cb: Callable[[Optional[str], "anki.notes.Note"], Optional[str]]
+    ) -> None:
+        if cb in self._hooks:
+            self._hooks.remove(cb)
+
+    def __call__(
+        self, reason_to_already_reject: Optional[str], note: anki.notes.Note
+    ) -> Optional[str]:
+        for filter in self._hooks:
+            try:
+                reason_to_already_reject = filter(reason_to_already_reject, note)
+            except:
+                # if the hook fails, remove it
+                self._hooks.remove(filter)
+                raise
+        return reason_to_already_reject
+
+
+add_card_accepts = _AddCardAcceptsFilter()
+
+
 class _AddCardsDidAddNoteHook:
     _hooks: List[Callable[["anki.notes.Note"], None]] = []
 
diff --git a/qt/tools/genhooks_gui.py b/qt/tools/genhooks_gui.py
index dcf543979..011ca9ace 100644
--- a/qt/tools/genhooks_gui.py
+++ b/qt/tools/genhooks_gui.py
@@ -412,6 +412,18 @@ def emptyNewCard():
         args=["note: anki.notes.Note"],
         legacy_hook="AddCards.noteAdded",
     ),
+    Hook(
+        name="add_card_accepts",
+        args=["reason_to_already_reject: Optional[str]", "note: anki.notes.Note"],
+        return_type="Optional[str]",
+        doc="""Decides whether the note should be added to the collection or
+        not. It is assumed to come from the addCards window.
+
+        reason_to_already_reject is the first reason to reject that
+        was found, or None. If your filter wants to reject, it should
+        replace return the reason to reject. Otherwise return the
+        input.""",
+    ),
     # Editing
     ###################
     Hook(