backend/core/query_planner.py

"""
Multi-Step Query Planner

Detects complex queries that require multiple datasets or operations,
decomposes them into atomic steps, and orchestrates execution.
"""

import json
import logging
from dataclasses import dataclass, field
from typing import List, Dict, Any, Optional
from enum import Enum

logger = logging.getLogger(__name__)


class StepType(Enum):
    """Types of query steps."""
    DATA_QUERY = "data_query"      # Simple data retrieval
    AGGREGATION = "aggregation"    # COUNT, SUM, GROUP BY
    COMPARISON = "comparison"      # Comparing results from previous steps
    SPATIAL_JOIN = "spatial_join"  # Joining datasets spatially
    COMBINE = "combine"            # Merge/combine step results


@dataclass
class QueryStep:
    """A single atomic step in a query plan."""
    step_id: str
    step_type: StepType
    description: str
    tables_needed: List[str]
    sql_template: Optional[str] = None
    depends_on: List[str] = field(default_factory=list)
    result_name: str = ""  # Name for intermediate result
    
    def to_dict(self) -> Dict[str, Any]:
        return {
            "step_id": self.step_id,
            "step_type": self.step_type.value,
            "description": self.description,
            "tables_needed": self.tables_needed,
            "sql_template": self.sql_template,
            "depends_on": self.depends_on,
            "result_name": self.result_name
        }


@dataclass 
class QueryPlan:
    """Complete execution plan for a complex query."""
    original_query: str
    is_complex: bool
    steps: List[QueryStep] = field(default_factory=list)
    parallel_groups: List[List[str]] = field(default_factory=list)  # Steps that can run in parallel
    final_combination_logic: str = ""
    
    def to_dict(self) -> Dict[str, Any]:
        return {
            "original_query": self.original_query,
            "is_complex": self.is_complex,
            "steps": [s.to_dict() for s in self.steps],
            "parallel_groups": self.parallel_groups,
            "final_combination_logic": self.final_combination_logic
        }


class QueryPlanner:
    """
    Multi-step query planning service.
    
    Analyzes queries to determine complexity and decomposes
    complex queries into executable atomic steps.
    """
    
    _instance = None
    
    # Keywords that often indicate multi-step queries
    COMPLEXITY_INDICATORS = [
        "compare", "comparison", "versus", "vs",
        "more than", "less than", "higher than", "lower than",
        "both", "and also", "as well as",
        "ratio", "percentage", "proportion",
        "correlation", "relationship between",
        "combine", "merge", "together with",
        "relative to", "compared to",
        "difference between", "gap between"
    ]
    
    # Keywords indicating multiple distinct data types
    MULTI_DOMAIN_KEYWORDS = {
        "health": ["hospital", "clinic", "healthcare", "health", "medical"],
        "education": ["school", "university", "education", "college", "student"],
        "infrastructure": ["road", "bridge", "infrastructure", "building"],
        "environment": ["forest", "water", "environment", "park", "protected"],
        "population": ["population", "demographic", "census", "people", "resident"]
    }
    
    def __new__(cls):
        if cls._instance is None:
            cls._instance = super(QueryPlanner, cls).__new__(cls)
            cls._instance.initialized = False
        return cls._instance
    
    def __init__(self):
        if self.initialized:
            return
        self.initialized = True
    
    def detect_complexity(self, query: str) -> Dict[str, Any]:
        """
        Analyze a query to determine if it requires multi-step planning.
        
        Returns:
            {
                "is_complex": bool,
                "reason": str,
                "detected_domains": List[str],
                "complexity_indicators": List[str]
            }
        """
        query_lower = query.lower()
        
        # Check for complexity indicators
        found_indicators = [
            ind for ind in self.COMPLEXITY_INDICATORS 
            if ind in query_lower
        ]
        
        # Check for multiple data domains
        found_domains = []
        for domain, keywords in self.MULTI_DOMAIN_KEYWORDS.items():
            if any(kw in query_lower for kw in keywords):
                found_domains.append(domain)
        
        # Determine complexity
        is_complex = (
            len(found_indicators) > 0 and len(found_domains) >= 2
        ) or (
            len(found_domains) >= 3
        ) or (
            any(x in query_lower for x in ["compare", "ratio", "correlation", "versus", " vs "])
            and len(found_domains) >= 2
        )
        
        reason = ""
        if is_complex:
            if len(found_domains) >= 2:
                reason = f"Query involves multiple data domains: {', '.join(found_domains)}"
            if found_indicators:
                reason += f". Contains comparison/aggregation keywords: {', '.join(found_indicators[:3])}"
        
        return {
            "is_complex": is_complex,
            "reason": reason,
            "detected_domains": found_domains,
            "complexity_indicators": found_indicators
        }
    
    async def plan_query(
        self, 
        query: str, 
        available_tables: List[str],
        llm_gateway
    ) -> QueryPlan:
        """
        Create an execution plan for a complex query.
        
        Uses LLM to decompose the query into atomic steps.
        """
        from backend.core.prompts import QUERY_PLANNING_PROMPT
        
        # Build table context
        table_list = "\n".join(f"- {t}" for t in available_tables)
        
        prompt = QUERY_PLANNING_PROMPT.format(
            user_query=query,
            available_tables=table_list
        )
        
        try:
            response = await llm_gateway.generate_response(prompt, [])
            
            # Parse JSON response
            response_clean = response.strip()
            if response_clean.startswith("```json"):
                response_clean = response_clean[7:]
            if response_clean.startswith("```"):
                response_clean = response_clean[3:]
            if response_clean.endswith("```"):
                response_clean = response_clean[:-3]
            
            plan_data = json.loads(response_clean.strip())
            
            # Convert to QueryPlan
            steps = []
            for i, step_data in enumerate(plan_data.get("steps", [])):
                step = QueryStep(
                    step_id=f"step_{i+1}",
                    step_type=StepType(step_data.get("type", "data_query")),
                    description=step_data.get("description", ""),
                    tables_needed=step_data.get("tables", []),
                    sql_template=step_data.get("sql_hint", None),
                    depends_on=step_data.get("depends_on", []),
                    result_name=step_data.get("result_name", f"result_{i+1}")
                )
                steps.append(step)
            
            # Determine parallel groups (steps with no dependencies can run together)
            parallel_groups = self._compute_parallel_groups(steps)
            
            return QueryPlan(
                original_query=query,
                is_complex=True,
                steps=steps,
                parallel_groups=parallel_groups,
                final_combination_logic=plan_data.get("combination_logic", "")
            )
            
        except Exception as e:
            logger.error(f"Query planning failed: {e}")
            # Return single-step fallback
            return QueryPlan(
                original_query=query,
                is_complex=False,
                steps=[],
                parallel_groups=[],
                final_combination_logic=""
            )
    
    def _compute_parallel_groups(self, steps: List[QueryStep]) -> List[List[str]]:
        """
        Compute which steps can be executed in parallel.
        
        Steps with no dependencies (or only completed dependencies) 
        can run together.
        """
        if not steps:
            return []
        
        groups = []
        executed = set()
        remaining = {s.step_id: s for s in steps}
        
        while remaining:
            # Find steps whose dependencies are all satisfied
            ready = [
                step_id for step_id, step in remaining.items()
                if all(dep in executed for dep in step.depends_on)
            ]
            
            if not ready:
                # Avoid infinite loop - add remaining as sequential
                ready = list(remaining.keys())[:1]
            
            groups.append(ready)
            
            for step_id in ready:
                executed.add(step_id)
                del remaining[step_id]
        
        return groups
    

# Singleton accessor
_query_planner: Optional[QueryPlanner] = None


def get_query_planner() -> QueryPlanner:
    """Get the singleton query planner instance."""
    global _query_planner
    if _query_planner is None:
        _query_planner = QueryPlanner()
    return _query_planner