Track battery percentage history; skip poll write when value unchanged

models.py

@@ -1,3 +1,5 @@
+from datetime import datetime
+
 from sqlalchemy import Column, Integer, String, Text, ForeignKey
 from sqlalchemy.orm import declarative_base, relationship
 
@@ -61,6 +63,11 @@ class Battery(Base):
         order_by="ChargeLog.charged_date",
         cascade="all, delete-orphan",
     )
+    pct_logs = relationship(
+        "BatteryPctLog", back_populates="battery",
+        order_by="BatteryPctLog.recorded_at.desc()",
+        cascade="all, delete-orphan",
+    )
 
     def is_available(self):
         return self.status == "available"
@@ -103,3 +110,18 @@ class ChargeLog(Base):
 
     def __repr__(self):
         return f"<ChargeLog {self.battery_id} {self.charged_date}>"
+
+
+class BatteryPctLog(Base):
+    __tablename__ = "battery_pct_log"
+
+    id          = Column(Integer, primary_key=True, autoincrement=True)
+    battery_id  = Column(Integer, ForeignKey("battery.id", ondelete="CASCADE"), nullable=False)
+    percentage  = Column(Integer, nullable=False)
+    recorded_at = Column(String(19), nullable=False)  # "YYYY-MM-DD HH:MM:SS"
+    source      = Column(String(10), nullable=True)   # 'poll', 'manual', 'charge'
+
+    battery = relationship("Battery", back_populates="pct_logs")
+
+    def __repr__(self):
+        return f"<BatteryPctLog {self.battery_id} {self.recorded_at} {self.percentage}%>"