Send at most one grouped birthday reminder email

Collects birthdays in the next 7 days, groups them into sections
(Today/Tomorrow/In N days), and sends a single email.

Fixes #201.

update.py

@@ -21,6 +21,7 @@ import agenda.mail
 import agenda.thespacedevs
 import agenda.types
 import agenda.uk_holiday
+from agenda.event import Event
 from agenda.types import StrDict
 from web_view import app
 
@@ -295,7 +296,11 @@ def update_gandi(config: flask.config.Config) -> None:
 
 
 def check_birthday_reminders(config: flask.config.Config) -> None:
-    """Check for upcoming birthdays and send email reminders."""
+    """Send at most one grouped birthday reminder email per day.
+
+    Collects birthdays in the next 7 days, groups them into sections
+    (Today/Tomorrow/In N days), and sends a single email.
+    """
     today = date.today()
     data_dir = config["PERSONAL_DATA"]
     entities_file = os.path.join(data_dir, "entities.yaml")
@@ -303,55 +308,65 @@ def check_birthday_reminders(config: flask.config.Config) -> None:
     if not os.path.exists(entities_file):
         return
 
-    # Get upcoming birthdays (next 7 days)
     birthdays = agenda.birthday.get_birthdays(today, entities_file)
-    upcoming_birthdays = []
 
-    for birthday in birthdays:
-        days_until = (birthday.date - today).days
+    # Collect next 7 days into a dict keyed by days-until
+    by_days: dict[int, list[Event]] = {}
+    for ev in birthdays:
+        days_until = (ev.as_date - today).days
         if 0 <= days_until <= 7:
-            upcoming_birthdays.append((birthday, days_until))
+            by_days.setdefault(days_until, []).append(ev)
 
-    if not upcoming_birthdays:
+    if not by_days:
         return
 
-    # Group birthdays by days until
-    birthday_groups = {}
-    for birthday, days_until in upcoming_birthdays:
-        if days_until not in birthday_groups:
-            birthday_groups[days_until] = []
-        birthday_groups[days_until].append(birthday)
+    # Build subject
+    headings: list[str] = []
+    if 0 in by_days:
+        headings.append("today")
+    if 1 in by_days:
+        headings.append("tomorrow")
+    others = sum(1 for k in by_days.keys() if k not in (0, 1))
+    if others:
+        plural = "s" if others != 1 else ""
+        headings.append(f"{others} other{plural}")
+    subject = (
+        f"🎂 Birthday reminders ({', '.join(headings)})"
+        if headings
+        else "🎂 Birthday reminders"
+    )
 
-    # Send reminder emails
-    for days_until, birthdays in birthday_groups.items():
-        if days_until == 0:
-            subject = "🎂 Birthday Today!"
-        elif days_until == 1:
-            subject = "🎂 Birthday Tomorrow!"
+    # Build body (UK style dates)
+    lines: list[str] = ["Upcoming birthdays (next 7 days):", ""]
+    for delta in sorted(by_days.keys()):
+        if delta == 0:
+            lines.append("Today")
+        elif delta == 1:
+            lines.append("Tomorrow")
         else:
-            subject = f"🎂 Birthday in {days_until} days"
+            lines.append(f"In {delta} days")
 
-        body_lines = ["Birthday Reminder:\n"]
-        for birthday in birthdays:
-            date_str = birthday.date.strftime("%A, %B %d, %Y")
-            if days_until == 0:
-                body_lines.append(f"Today: {birthday.title} - {date_str}")
-            elif days_until == 1:
-                body_lines.append(f"Tomorrow: {birthday.title} - {date_str}")
-            else:
-                body_lines.append(f"{date_str}: {birthday.title}")
-
-        body_lines.append(
-            f"\nView all birthdays: https://edwardbetts.com/agenda/birthdays"
+        entries = sorted(
+            by_days[delta],
+            key=lambda e: (e.as_date, (e.title or e.name or "")),
         )
 
-        body = "\n".join(body_lines)
+        for ev in entries:
+            d = ev.as_date
+            # Portable UK-style date: weekday, D Month YYYY
+            date_str = f"{d:%A}, {d.day} {d:%B %Y}"
+            label = ev.title or ev.name
+            lines.append(f"  • {label} — {date_str}")
 
-        if sys.stdin.isatty():
-            print(f"Birthday reminder: {subject}")
-            print(body)
+        lines.append("")
 
-        agenda.mail.send_mail(config, subject, body)
+    lines.append("View all birthdays: https://edwardbetts.com/agenda/birthdays")
+    body = "\n".join(lines)
+
+    if sys.stdin.isatty():
+        print(f"Birthday reminder: {subject}\n{body}")
+
+    agenda.mail.send_mail(config, subject, body)
 
 
 def main() -> None: