Add SiteSetting model for admin-configurable settings

app/models/site_setting.py

@@ -0,0 +1,98 @@
+"""
+Key/value store for admin-configurable site settings.
+
+Values are strings on disk; the typed helpers below do the coercion. Reads
+are cached per process and the cache is dropped on write, so the settings
+page is authoritative without hitting the database on every request.
+
+Created by: Jess Rogerson (yelling commands at Claude.AI)
+"""
+
+from datetime import datetime
+import threading
+
+from app import db
+
+# Defaults are the behaviour LIM had before settings existed, except where
+# noted — anything not yet stored falls back to these.
+DEFAULTS = {
+    'allow_registration': 'true',
+    # Visibility given to newly created sets.
+    'default_visibility': 'private',
+    # Send logged-in users straight to their dashboard instead of the
+    # marketing homepage.
+    'home_redirect_dashboard': 'true',
+}
+
+VISIBILITIES = ('private', 'shared', 'public')
+
+_cache = {}
+_cache_lock = threading.Lock()
+
+
+class SiteSetting(db.Model):
+    """One configurable setting."""
+
+    __tablename__ = 'site_settings'
+
+    id = db.Column(db.Integer, primary_key=True)
+    key = db.Column(db.String(64), unique=True, nullable=False, index=True)
+    value = db.Column(db.Text, nullable=True)
+    updated_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow,
+                           onupdate=datetime.utcnow)
+
+    def __repr__(self):
+        return f'<SiteSetting {self.key}={self.value!r}>'
+
+    # -- reads --------------------------------------------------------------
+
+    @classmethod
+    def get(cls, key, default=None):
+        with _cache_lock:
+            if key in _cache:
+                return _cache[key]
+        try:
+            row = cls.query.filter_by(key=key).first()
+        except Exception:
+            # Table may not exist yet (first boot, before create_all).
+            return DEFAULTS.get(key, default)
+        value = row.value if row else DEFAULTS.get(key, default)
+        with _cache_lock:
+            _cache[key] = value
+        return value
+
+    @classmethod
+    def get_bool(cls, key, default=False):
+        value = cls.get(key)
+        if value is None:
+            return default
+        return str(value).strip().lower() in ('1', 'true', 'yes', 'on')
+
+    @classmethod
+    def all_settings(cls):
+        merged = dict(DEFAULTS)
+        try:
+            for row in cls.query.all():
+                merged[row.key] = row.value
+        except Exception:
+            pass
+        return merged
+
+    # -- writes -------------------------------------------------------------
+
+    @classmethod
+    def set(cls, key, value):
+        if isinstance(value, bool):
+            value = 'true' if value else 'false'
+        row = cls.query.filter_by(key=key).first()
+        if row:
+            row.value = value
+        else:
+            db.session.add(cls(key=key, value=value))
+        cls.clear_cache()
+        return value
+
+    @classmethod
+    def clear_cache(cls):
+        with _cache_lock:
+            _cache.clear()