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"""
Hierarchical Retrieval Architecture for Production-Grade RAG

Implements a three-tier retrieval system:
1. Tier 1: Knowledge Base Routing - Routes queries to relevant KBs
2. Tier 2: Document Filtering - Filters by metadata
3. Tier 3: Chunk Refinement - Precise vector retrieval

This architecture addresses scalability and precision limitations
in production environments with large document collections.
"""

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


@dataclass
class RetrievalConfig:
    """Configuration for hierarchical retrieval"""
    
    # Tier 1: KB Routing
    enable_kb_routing: bool = True
    kb_routing_method: str = "auto"  # "auto", "rule_based", "llm_based", "all"
    kb_routing_threshold: float = 0.5
    
    # Tier 2: Document Filtering
    enable_doc_filtering: bool = True
    metadata_fields: List[str] = field(default_factory=list)  # Key metadata fields to use
    enable_metadata_similarity: bool = False  # Fuzzy matching for text metadata
    metadata_similarity_threshold: float = 0.7
    
    # Tier 3: Chunk Refinement
    enable_parent_child_chunking: bool = False
    use_summary_mapping: bool = False
    chunk_refinement_top_k: int = 10
    
    # General settings
    max_candidates_per_tier: int = 100
    enable_hybrid_search: bool = True
    vector_weight: float = 0.7
    keyword_weight: float = 0.3


@dataclass
class RetrievalResult:
    """Result from hierarchical retrieval"""
    
    query: str
    selected_kbs: List[str] = field(default_factory=list)
    filtered_docs: List[Dict[str, Any]] = field(default_factory=list)
    retrieved_chunks: List[Dict[str, Any]] = field(default_factory=list)
    
    # Metadata about retrieval process
    tier1_candidates: int = 0
    tier2_candidates: int = 0
    tier3_candidates: int = 0
    
    total_time_ms: float = 0.0
    tier1_time_ms: float = 0.0
    tier2_time_ms: float = 0.0
    tier3_time_ms: float = 0.0


class HierarchicalRetrieval:
    """
    Three-tier hierarchical retrieval system for production-grade RAG.
    
    This class orchestrates the retrieval process across three tiers:
    - Tier 1: Routes query to relevant knowledge bases
    - Tier 2: Filters documents by metadata
    - Tier 3: Performs precise chunk-level retrieval
    """
    
    def __init__(self, config: Optional[RetrievalConfig] = None):
        """
        Initialize hierarchical retrieval system.
        
        Args:
            config: Configuration for retrieval behavior
        """
        self.config = config or RetrievalConfig()
        self.logger = logging.getLogger(__name__)
    
    def retrieve(
        self,
        query: str,
        kb_ids: List[str],
        top_k: int = 10,
        filters: Optional[Dict[str, Any]] = None
    ) -> RetrievalResult:
        """
        Perform hierarchical retrieval.
        
        Args:
            query: User query
            kb_ids: List of knowledge base IDs to search
            top_k: Number of final chunks to return
            filters: Optional metadata filters
            
        Returns:
            RetrievalResult with chunks and metadata
        """
        import time
        start_time = time.time()
        
        result = RetrievalResult(query=query)
        
        # Tier 1: Knowledge Base Routing
        tier1_start = time.time()
        selected_kbs = self._tier1_kb_routing(query, kb_ids)
        result.selected_kbs = selected_kbs
        result.tier1_candidates = len(selected_kbs)
        result.tier1_time_ms = (time.time() - tier1_start) * 1000
        
        if not selected_kbs:
            self.logger.warning(f"No knowledge bases selected for query: {query}")
            result.total_time_ms = (time.time() - start_time) * 1000
            return result
        
        # Tier 2: Document Filtering
        tier2_start = time.time()
        filtered_docs = self._tier2_document_filtering(
            query, selected_kbs, filters
        )
        result.filtered_docs = filtered_docs
        result.tier2_candidates = len(filtered_docs)
        result.tier2_time_ms = (time.time() - tier2_start) * 1000
        
        if not filtered_docs:
            self.logger.warning(f"No documents passed filtering for query: {query}")
            result.total_time_ms = (time.time() - start_time) * 1000
            return result
        
        # Tier 3: Chunk Refinement
        tier3_start = time.time()
        chunks = self._tier3_chunk_refinement(
            query, filtered_docs, top_k
        )
        result.retrieved_chunks = chunks
        result.tier3_candidates = len(chunks)
        result.tier3_time_ms = (time.time() - tier3_start) * 1000
        
        result.total_time_ms = (time.time() - start_time) * 1000
        
        self.logger.info(
            f"Hierarchical retrieval completed: "
            f"{result.tier1_candidates} KBs -> "
            f"{result.tier2_candidates} docs -> "
            f"{result.tier3_candidates} chunks "
            f"in {result.total_time_ms:.2f}ms"
        )
        
        return result
    
    def _tier1_kb_routing(
        self,
        query: str,
        kb_ids: List[str]
    ) -> List[str]:
        """
        Tier 1: Route query to relevant knowledge bases.
        
        Args:
            query: User query
            kb_ids: Available knowledge base IDs
            
        Returns:
            List of selected KB IDs
        """
        if not self.config.enable_kb_routing:
            return kb_ids
        
        method = self.config.kb_routing_method
        
        if method == "all":
            # Use all provided KBs
            return kb_ids
        
        elif method == "rule_based":
            # Rule-based routing (placeholder for custom rules)
            return self._rule_based_routing(query, kb_ids)
        
        elif method == "llm_based":
            # LLM-based routing (placeholder for LLM integration)
            return self._llm_based_routing(query, kb_ids)
        
        else:  # "auto"
            # Auto mode: intelligent routing based on query analysis
            return self._auto_routing(query, kb_ids)
    
    def _rule_based_routing(
        self,
        query: str,
        kb_ids: List[str]
    ) -> List[str]:
        """
        Rule-based KB routing using predefined rules.
        
        This is a placeholder for custom routing logic.
        Users can extend this with domain-specific rules.
        """
        # TODO: Implement rule-based routing
        # For now, return all KBs
        return kb_ids
    
    def _llm_based_routing(
        self,
        query: str,
        kb_ids: List[str]
    ) -> List[str]:
        """
        LLM-based KB routing using language model.
        
        This is a placeholder for LLM integration.
        """
        # TODO: Implement LLM-based routing
        # For now, return all KBs
        return kb_ids
    
    def _auto_routing(
        self,
        query: str,
        kb_ids: List[str]
    ) -> List[str]:
        """
        Auto routing using query analysis.
        
        This is a placeholder for intelligent routing.
        """
        # TODO: Implement auto routing with query analysis
        # For now, return all KBs
        return kb_ids
    
    def _tier2_document_filtering(
        self,
        query: str,
        kb_ids: List[str],
        filters: Optional[Dict[str, Any]] = None
    ) -> List[Dict[str, Any]]:
        """
        Tier 2: Filter documents by metadata.
        
        Args:
            query: User query
            kb_ids: Selected knowledge base IDs
            filters: Metadata filters
            
        Returns:
            List of filtered documents
        """
        if not self.config.enable_doc_filtering:
            # Skip filtering, return placeholder
            return []
        
        # TODO: Implement document filtering logic
        # This would integrate with the existing document service
        # to filter by metadata fields
        
        filtered_docs = []
        
        # Placeholder: would query documents from selected KBs
        # and apply metadata filters
        
        return filtered_docs
    
    def _tier3_chunk_refinement(
        self,
        query: str,
        filtered_docs: List[Dict[str, Any]],
        top_k: int
    ) -> List[Dict[str, Any]]:
        """
        Tier 3: Perform precise chunk-level retrieval.
        
        Args:
            query: User query
            filtered_docs: Documents that passed Tier 2 filtering
            top_k: Number of chunks to return
            
        Returns:
            List of retrieved chunks
        """
        # TODO: Implement chunk refinement logic
        # This would integrate with existing vector search
        # and optionally use parent-child chunking
        
        chunks = []
        
        # Placeholder: would perform vector search within
        # the filtered document set
        
        return chunks


class KBRouter:
    """
    Knowledge Base Router for Tier 1.
    
    Handles routing logic to select relevant KBs based on query intent.
    """
    
    def __init__(self):
        self.logger = logging.getLogger(__name__)
    
    def route(
        self,
        query: str,
        available_kbs: List[Dict[str, Any]],
        method: str = "auto"
    ) -> List[str]:
        """
        Route query to relevant knowledge bases.
        
        Args:
            query: User query
            available_kbs: List of available KB metadata
            method: Routing method ("auto", "rule_based", "llm_based")
            
        Returns:
            List of selected KB IDs
        """
        # TODO: Implement routing logic
        return [kb["id"] for kb in available_kbs]


class DocumentFilter:
    """
    Document Filter for Tier 2.
    
    Handles metadata-based document filtering.
    """
    
    def __init__(self):
        self.logger = logging.getLogger(__name__)
    
    def filter(
        self,
        query: str,
        documents: List[Dict[str, Any]],
        metadata_fields: List[str],
        filters: Optional[Dict[str, Any]] = None
    ) -> List[Dict[str, Any]]:
        """
        Filter documents by metadata.
        
        Args:
            query: User query
            documents: List of documents to filter
            metadata_fields: Key metadata fields to consider
            filters: Explicit metadata filters
            
        Returns:
            Filtered list of documents
        """
        # TODO: Implement filtering logic
        return documents


class ChunkRefiner:
    """
    Chunk Refiner for Tier 3.
    
    Handles precise chunk-level retrieval with optional parent-child support.
    """
    
    def __init__(self):
        self.logger = logging.getLogger(__name__)
    
    def refine(
        self,
        query: str,
        doc_ids: List[str],
        top_k: int,
        use_parent_child: bool = False
    ) -> List[Dict[str, Any]]:
        """
        Perform precise chunk retrieval.
        
        Args:
            query: User query
            doc_ids: Document IDs to search within
            top_k: Number of chunks to return
            use_parent_child: Whether to use parent-child chunking
            
        Returns:
            List of retrieved chunks
        """
        # TODO: Implement chunk refinement logic
        return []