import re
from app.data_loader import loader

class IntentParser:
    def __init__(self):
        pass

    def parse(self, text):
        text = text.lower()
        
        response = {
            "intent": "general_chat", # Default to LLM
            "item_code": None,
            "location": None,
            "horizon_days": None,
            "extra": {}
        }

        # 1. Detect Intent (order matters - more specific checks first)
        if any(x in text for x in ["list items", "show catalog", "what items", "available items", "list available", "show items"]):
            response["intent"] = "list_items"
        elif any(x in text for x in ["forecast", "demand", "predict", "future", "sales"]):
            response["intent"] = "demand_forecast"
        elif any(x in text for x in ["details", "info", "about", "price", "description"]):
            response["intent"] = "item_details"
        elif any(x in text for x in ["inventory", "stock", "how many", "available", "on hand"]):
            response["intent"] = "check_inventory"
        elif any(x in text for x in ["supplier", "vendor", "who supplies", "lead time"]):
            response["intent"] = "supplier_info"
        elif any(x in text for x in ["buy", "order", "purchase", "requisition"]):
            response["intent"] = "create_requisition"
        elif any(x in text for x in ["status", "alerts", "dashboard", "overview"]):
            response["intent"] = "system_status"
        elif any(x in text for x in ["pdf", "download", "report", "file"]):
            response["intent"] = "generate_report"

        # 2. Extract Item Code
        # Look for patterns like FS1234, BMS0001, etc. (2-3 letters + 4 digits)
        item_match = re.search(r'\b([a-z]{2,3}\d{4})\b', text)
        if item_match:
            response["item_code"] = item_match.group(1).upper()
        else:
            # Fallback: check against known items in DB
            if loader.items_df is not None:
                known_items = loader.items_df['item_code'].tolist()
                for item in known_items:
                    if item.lower() in text:
                        response["item_code"] = item
                        break

        # 2.5 Extract Quantity (for orders)
        qty_match = re.search(r'\b(\d+)\s*(?:units|pcs|pieces)?\b', text)
        if qty_match:
            # Avoid confusing horizon days with quantity if possible
            # If "days" is not next to it, assume qty
            if "day" not in text[qty_match.end():qty_match.end()+5]:
                response["extra"]["qty"] = int(qty_match.group(1))

        # 3. Extract Location
        if re.search(r'\b(na|north america|usa|us)\b', text):
            response["location"] = "NA"
        elif re.search(r'\b(eu|europe|uk|germany)\b', text):
            response["location"] = "EU"
        elif re.search(r'\b(apac|asia|china|india)\b', text):
            response["location"] = "APAC"

        # 4. Extract Horizon
        response["horizon_days"] = self._parse_horizon(text)

        return response

    def _parse_horizon(self, text):
        days = None
        
        # Explicit days
        days_match = re.search(r'(\d+)\s*days?', text)
        if days_match:
            return int(days_match.group(1))
            
        # Weeks
        weeks_match = re.search(r'(\d+)\s*weeks?', text)
        if weeks_match:
            return int(weeks_match.group(1)) * 7
            
        # Months
        months_match = re.search(r'(\d+)\s*months?', text)
        if months_match:
            return int(months_match.group(1)) * 30

        # Keywords
        if "next week" in text:
            return 7
        if "next month" in text:
            return 30
        if "next year" in text:
            return 365
        if "tomorrow" in text:
            return 1
            
        return days

parser = IntentParser()