feat: 4.0 - Backend API - Streak calculation utility

dashboard/api.py

@@ -35,6 +35,107 @@ GITEA_URL = os.environ.get('GITEA_URL', 'https://gitea.romfast.ro')
 GITEA_ORG = os.environ.get('GITEA_ORG', 'romfast')
 GITEA_TOKEN = os.environ.get('GITEA_TOKEN', '')
 
+
+def calculate_streak(completions, frequency):
+    """
+    Calculate the current streak for a habit based on completions array.
+    
+    Args:
+        completions: List of ISO timestamp strings representing completion dates
+        frequency: 'daily' or 'weekly'
+    
+    Returns:
+        int: The current streak count (days for daily, weeks for weekly)
+    
+    Rules:
+        - Counts consecutive periods from most recent completion backwards
+        - Daily: counts consecutive days without gaps
+        - Weekly: counts consecutive 7-day periods
+        - Returns 0 for no completions
+        - Returns 0 if streak is broken (gap detected)
+        - Today's completion counts even if previous days were missed
+    """
+    from datetime import datetime, timedelta
+    
+    # No completions = no streak
+    if not completions:
+        return 0
+    
+    # Parse all completion dates and sort descending (most recent first)
+    try:
+        completion_dates = []
+        for comp in completions:
+            dt = datetime.fromisoformat(comp.replace('Z', '+00:00'))
+            # Convert to date only (ignore time)
+            completion_dates.append(dt.date())
+        
+        completion_dates = sorted(set(completion_dates), reverse=True)
+    except (ValueError, AttributeError):
+        return 0
+    
+    if not completion_dates:
+        return 0
+    
+    # Get today's date
+    today = datetime.now().date()
+    
+    if frequency == 'daily':
+        # For daily habits, count consecutive days
+        streak = 0
+        expected_date = completion_dates[0]
+        
+        # If most recent completion is today or yesterday, start counting
+        if expected_date < today - timedelta(days=1):
+            # Streak is broken (last completion was more than 1 day ago)
+            return 0
+        
+        for completion in completion_dates:
+            if completion == expected_date:
+                streak += 1
+                expected_date -= timedelta(days=1)
+            elif completion < expected_date:
+                # Gap found, streak is broken
+                break
+        
+        return streak
+    
+    elif frequency == 'weekly':
+        # For weekly habits, count consecutive weeks (7-day periods)
+        streak = 0
+        
+        # Most recent completion
+        most_recent = completion_dates[0]
+        
+        # Check if most recent completion is within current week
+        days_since = (today - most_recent).days
+        if days_since > 6:
+            # Last completion was more than a week ago, streak is broken
+            return 0
+        
+        # Start counting from the week of the most recent completion
+        current_week_start = most_recent - timedelta(days=most_recent.weekday())
+        
+        for i in range(len(completion_dates)):
+            week_start = current_week_start - timedelta(days=i * 7)
+            week_end = week_start + timedelta(days=6)
+            
+            # Check if there's a completion in this week
+            has_completion = any(
+                week_start <= comp <= week_end
+                for comp in completion_dates
+            )
+            
+            if has_completion:
+                streak += 1
+            else:
+                # No completion in this week, streak is broken
+                break
+        
+        return streak
+    
+    return 0
+
+
 class TaskBoardHandler(SimpleHTTPRequestHandler):
     
     def do_POST(self):