feat: Add historical data storage for daily and monthly usage tracking

src/claude_monitor/cli/main.py

@@ -385,6 +385,29 @@
     logger = logging.getLogger(__name__)
 
     try:
+        # Parse date filters early so they can be used for both current and historical data
+        from datetime import datetime, timedelta
+        from claude_monitor.utils.time_utils import TimezoneHandler
+
+        tz = TimezoneHandler(args.timezone)
+
+        def _parse_date(date_str: Optional[str]):
+            if not date_str:
+                return None
+            for fmt in ("%Y-%m-%d", "%Y.%m.%d", "%Y/%m/%d"):
+                try:
+                    return tz.ensure_timezone(datetime.strptime(date_str, fmt))
+                except ValueError:
+                    continue
+            print_themed(f"Invalid date format: {date_str}. Use YYYY-MM-DD.", style="warning")
+            return None
+
+        start_dt = _parse_date(getattr(args, "start_date", None))
+        end_dt = _parse_date(getattr(args, "end_date", None))
+
+        # Make end date inclusive by adding one day (entries use precise timestamps)
+        end_dt_inclusive = end_dt + timedelta(days=1) if end_dt else None
+
         # Create aggregator with appropriate mode
         aggregator = UsageAggregator(
             data_path=str(data_path),
@@ -395,9 +418,87 @@
         # Create table controller
         controller = TableViewsController(console=console)
 
-        # Get aggregated data
+        # Get aggregated data with date filters
         logger.info(f"Loading {view_mode} usage data...")
-        aggregated_data = aggregator.aggregate()
+        aggregated_data = aggregator.aggregate(start_dt, end_dt_inclusive)
+
+        # Initialize history manager for daily and monthly views
+        history_mode = getattr(args, "history", "auto")
+        if history_mode != "off":
+            from claude_monitor.data.history_manager import HistoryManager
+            history_manager = HistoryManager()
+
+            if view_mode == "daily":
+                # Load historical data if in auto or readonly mode
+                if history_mode in ["auto", "readonly"]:
+                    # Load historical data using the same date filters
+                    historical_data = history_manager.load_historical_daily_data(
+                        start_date=start_dt,
+                        end_date=end_dt_inclusive
+                    )
+
+                    if historical_data:
+                        print_themed(f"Loaded {len(historical_data)} days from history", style="info")
+
+                        # Merge with current data
+                        aggregated_data = history_manager.merge_with_current_data(
+                            aggregated_data, historical_data
+                        )
+                        print_themed(f"Displaying {len(aggregated_data)} total days", style="info")
+
+                # Save current data to history if in auto or writeonly mode
+                if aggregated_data and history_mode in ["auto", "writeonly"]:
+                    saved_count = history_manager.save_daily_data(aggregated_data)
+                    if saved_count > 0:
+                        print_themed(f"Saved {saved_count} days to history", style="success")
+
+            elif view_mode == "monthly":
+                # For monthly view, always work with daily data and aggregate to monthly
+                if history_mode in ["auto", "readonly"]:
+                    # Get current daily data first
+                    daily_aggregator = UsageAggregator(
+                        data_path=str(data_path),
+                        aggregation_mode="daily",
+                        timezone=args.timezone,
+                    )
+                    current_daily = daily_aggregator.aggregate(start_dt, end_dt_inclusive)
+
+                    # Load historical daily data
+                    daily_historical = history_manager.load_historical_daily_data(
+                        start_date=start_dt,
+                        end_date=end_dt_inclusive
+                    )
+
+                    # Save current daily data to history if in auto mode
+                    if history_mode == "auto" and current_daily:
+                        saved = history_manager.save_daily_data(current_daily)
+                        if saved > 0:
+                            print_themed(f"Saved {saved} days to history", style="success")
+
+                    # Merge current and historical daily data
+                    all_daily = []
+                    if current_daily and daily_historical:
+                        all_daily = history_manager.merge_with_current_data(
+                            current_daily, daily_historical
+                        )
+                        print_themed(f"Merged {len(current_daily)} current + {len(daily_historical)} historical days", style="info")
+                    elif current_daily:
+                        all_daily = current_daily
+                        print_themed(f"Using {len(current_daily)} current days", style="info")
+                    elif daily_historical:
+                        all_daily = daily_historical
+                        print_themed(f"Using {len(daily_historical)} historical days", style="info")
+
+                    # Always aggregate daily data into monthly
+                    if all_daily:
+                        monthly_from_daily = history_manager.aggregate_monthly_from_daily(all_daily)
+
+                        if monthly_from_daily:
+                            # Replace the initial aggregated_data with the one from daily
+                            aggregated_data = monthly_from_daily
+                            print_themed(f"Displaying {len(aggregated_data)} months aggregated from {len(all_daily)} days", style="info")
+                        else:
+                            print_themed("No monthly data could be aggregated from daily data", style="warning")
 
         if not aggregated_data:
             print_themed(f"No usage data found for {view_mode} view", style="warning")

src/claude_monitor/core/settings.py

@@ -138,6 +138,16 @@ def _get_system_time_format() -> str:
         description="Display theme (light, dark, classic, auto)",
     )
 
+    start_date: Optional[str] = Field(
+        default=None,
+        description="Start date for filtering data (YYYY-MM-DD format)"
+    )
+
+    end_date: Optional[str] = Field(
+        default=None,
+        description="End date for filtering data (YYYY-MM-DD format)"
+    )
+
     custom_limit_tokens: Optional[int] = Field(
         default=None, gt=0, description="Token limit for custom plan"
     )
@@ -170,6 +180,11 @@ def _get_system_time_format() -> str:
 
     clear: bool = Field(default=False, description="Clear saved configuration")
 
+    history: Literal["auto", "off", "readonly", "writeonly"] = Field(
+        default="auto",
+        description="History mode: auto (save+load), off (disable), readonly (load only), writeonly (save only)"
+    )
+
     @field_validator("plan", mode="before")
     @classmethod
     def validate_plan(cls, v: Any) -> str:
@@ -240,6 +255,20 @@ def validate_log_level(cls, v: str) -> str:
             raise ValueError(f"Invalid log level: {v}")
         return v_upper
 
+    @field_validator("history", mode="before")
+    @classmethod
+    def validate_history(cls, v: Any) -> str:
+        """Validate and normalize history mode value."""
+        if isinstance(v, str):
+            v_lower = v.lower()
+            valid_modes = ["auto", "off", "readonly", "writeonly"]
+            if v_lower in valid_modes:
+                return v_lower
+            raise ValueError(
+                f"Invalid history mode: {v}. Must be one of: {', '.join(valid_modes)}"
+            )
+        return v
+
     @classmethod
     def settings_customise_sources(
         cls,
@@ -350,5 +379,8 @@ def to_namespace(self) -> argparse.Namespace:
         args.log_level = self.log_level
         args.log_file = str(self.log_file) if self.log_file else None
         args.version = self.version
+        args.start_date = self.start_date
+        args.end_date = self.end_date
+        args.history = self.history
 
         return args

src/claude_monitor/data/aggregator.py

@@ -266,9 +266,17 @@ def calculate_totals(self, aggregated_data: List[Dict[str, Any]]) -> Dict[str, A
             "entries_count": total_stats.count,
         }
 
-    def aggregate(self) -> List[Dict[str, Any]]:
+    def aggregate(
+        self,
+        start_date: Optional[datetime] = None,
+        end_date: Optional[datetime] = None
+    ) -> List[Dict[str, Any]]:
         """Main aggregation method that reads data and returns aggregated results.
 
+        Args:
+            start_date: Optional start date filter
+            end_date: Optional end date filter
+
         Returns:
             List of aggregated data based on aggregation_mode
         """
@@ -288,10 +296,10 @@ def aggregate(self) -> List[Dict[str, Any]]:
             if entry.timestamp.tzinfo is None:
                 entry.timestamp = self.timezone_handler.ensure_timezone(entry.timestamp)
 
-        # Aggregate based on mode
+        # Aggregate based on mode with date filters
         if self.aggregation_mode == "daily":
-            return self.aggregate_daily(entries)
+            return self.aggregate_daily(entries, start_date, end_date)
         elif self.aggregation_mode == "monthly":
-            return self.aggregate_monthly(entries)
+            return self.aggregate_monthly(entries, start_date, end_date)
         else:
             raise ValueError(f"Invalid aggregation mode: {self.aggregation_mode}")