# app/services/memory/indexing/retrieval.py
"""
Memory Retrieval Engine.

Provides hybrid retrieval capabilities combining:
- Vector similarity search
- Temporal filtering
- Entity filtering
- Outcome filtering
- Relevance scoring
- Result caching
"""

import hashlib
import logging
from dataclasses import dataclass, field
from datetime import UTC, datetime
from typing import Any, TypeVar
from uuid import UUID

from app.services.memory.types import (
    Episode,
    Fact,
    MemoryType,
    Outcome,
    Procedure,
    RetrievalResult,
)

from .index import (
    MemoryIndexer,
    get_memory_indexer,
)

logger = logging.getLogger(__name__)

T = TypeVar("T", Episode, Fact, Procedure)


def _utcnow() -> datetime:
    """Get current UTC time as timezone-aware datetime."""
    return datetime.now(UTC)


@dataclass
class RetrievalQuery:
    """Query parameters for memory retrieval."""

    # Text/semantic query
    query_text: str | None = None
    query_embedding: list[float] | None = None

    # Temporal filters
    start_time: datetime | None = None
    end_time: datetime | None = None
    recent_seconds: float | None = None

    # Entity filters
    entities: list[tuple[str, str]] | None = None
    entity_match_all: bool = False

    # Outcome filters
    outcomes: list[Outcome] | None = None

    # Memory type filter
    memory_types: list[MemoryType] | None = None

    # Result options
    limit: int = 10
    min_relevance: float = 0.0

    # Retrieval mode
    use_vector: bool = True
    use_temporal: bool = True
    use_entity: bool = True
    use_outcome: bool = True

    def to_cache_key(self) -> str:
        """Generate a cache key for this query."""
        key_parts = [
            self.query_text or "",
            str(self.start_time),
            str(self.end_time),
            str(self.recent_seconds),
            str(self.entities),
            str(self.outcomes),
            str(self.memory_types),
            str(self.limit),
            str(self.min_relevance),
        ]
        key_string = "|".join(key_parts)
        return hashlib.sha256(key_string.encode()).hexdigest()[:32]


@dataclass
class ScoredResult:
    """A retrieval result with relevance score."""

    memory_id: UUID
    memory_type: MemoryType
    relevance_score: float
    score_breakdown: dict[str, float] = field(default_factory=dict)
    metadata: dict[str, Any] = field(default_factory=dict)


@dataclass
class CacheEntry:
    """A cached retrieval result."""

    results: list[ScoredResult]
    created_at: datetime
    ttl_seconds: float
    query_key: str

    def is_expired(self) -> bool:
        """Check if this cache entry has expired."""
        age = (_utcnow() - self.created_at).total_seconds()
        return age > self.ttl_seconds


class RelevanceScorer:
    """
    Calculates relevance scores for retrieved memories.

    Combines multiple signals:
    - Vector similarity (if available)
    - Temporal recency
    - Entity match count
    - Outcome preference
    - Importance/confidence
    """

    def __init__(
        self,
        vector_weight: float = 0.4,
        recency_weight: float = 0.2,
        entity_weight: float = 0.2,
        outcome_weight: float = 0.1,
        importance_weight: float = 0.1,
    ) -> None:
        """
        Initialize the relevance scorer.

        Args:
            vector_weight: Weight for vector similarity (0-1)
            recency_weight: Weight for temporal recency (0-1)
            entity_weight: Weight for entity matches (0-1)
            outcome_weight: Weight for outcome preference (0-1)
            importance_weight: Weight for importance score (0-1)
        """
        total = (
            vector_weight
            + recency_weight
            + entity_weight
            + outcome_weight
            + importance_weight
        )
        # Normalize weights
        self.vector_weight = vector_weight / total
        self.recency_weight = recency_weight / total
        self.entity_weight = entity_weight / total
        self.outcome_weight = outcome_weight / total
        self.importance_weight = importance_weight / total

    def score(
        self,
        memory_id: UUID,
        memory_type: MemoryType,
        vector_similarity: float | None = None,
        timestamp: datetime | None = None,
        entity_match_count: int = 0,
        entity_total: int = 1,
        outcome: Outcome | None = None,
        importance: float = 0.5,
        preferred_outcomes: list[Outcome] | None = None,
    ) -> ScoredResult:
        """
        Calculate a relevance score for a memory.

        Args:
            memory_id: ID of the memory
            memory_type: Type of memory
            vector_similarity: Similarity score from vector search (0-1)
            timestamp: Timestamp of the memory
            entity_match_count: Number of matching entities
            entity_total: Total entities in query
            outcome: Outcome of the memory
            importance: Importance score of the memory (0-1)
            preferred_outcomes: Outcomes to prefer

        Returns:
            Scored result with breakdown
        """
        breakdown: dict[str, float] = {}

        # Vector similarity score
        if vector_similarity is not None:
            breakdown["vector"] = vector_similarity
        else:
            breakdown["vector"] = 0.5  # Neutral if no vector

        # Recency score (exponential decay)
        if timestamp:
            age_hours = (_utcnow() - timestamp).total_seconds() / 3600
            # Decay with half-life of 24 hours
            breakdown["recency"] = 2 ** (-age_hours / 24)
        else:
            breakdown["recency"] = 0.5

        # Entity match score
        if entity_total > 0:
            breakdown["entity"] = entity_match_count / entity_total
        else:
            breakdown["entity"] = 1.0  # No entity filter = full score

        # Outcome score
        if preferred_outcomes and outcome:
            breakdown["outcome"] = 1.0 if outcome in preferred_outcomes else 0.0
        else:
            breakdown["outcome"] = 0.5  # Neutral if no preference

        # Importance score
        breakdown["importance"] = importance

        # Calculate weighted sum
        total_score = (
            breakdown["vector"] * self.vector_weight
            + breakdown["recency"] * self.recency_weight
            + breakdown["entity"] * self.entity_weight
            + breakdown["outcome"] * self.outcome_weight
            + breakdown["importance"] * self.importance_weight
        )

        return ScoredResult(
            memory_id=memory_id,
            memory_type=memory_type,
            relevance_score=total_score,
            score_breakdown=breakdown,
        )


class RetrievalCache:
    """
    In-memory cache for retrieval results.

    Supports TTL-based expiration and LRU eviction.
    """

    def __init__(
        self,
        max_entries: int = 1000,
        default_ttl_seconds: float = 300,
    ) -> None:
        """
        Initialize the cache.

        Args:
            max_entries: Maximum cache entries
            default_ttl_seconds: Default TTL for entries
        """
        self._cache: dict[str, CacheEntry] = {}
        self._max_entries = max_entries
        self._default_ttl = default_ttl_seconds
        self._access_order: list[str] = []
        logger.info(
            f"Initialized RetrievalCache with max_entries={max_entries}, "
            f"ttl={default_ttl_seconds}s"
        )

    def get(self, query_key: str) -> list[ScoredResult] | None:
        """
        Get cached results for a query.

        Args:
            query_key: Cache key for the query

        Returns:
            Cached results or None if not found/expired
        """
        if query_key not in self._cache:
            return None

        entry = self._cache[query_key]
        if entry.is_expired():
            del self._cache[query_key]
            if query_key in self._access_order:
                self._access_order.remove(query_key)
            return None

        # Update access order (LRU)
        if query_key in self._access_order:
            self._access_order.remove(query_key)
        self._access_order.append(query_key)

        logger.debug(f"Cache hit for {query_key}")
        return entry.results

    def put(
        self,
        query_key: str,
        results: list[ScoredResult],
        ttl_seconds: float | None = None,
    ) -> None:
        """
        Cache results for a query.

        Args:
            query_key: Cache key for the query
            results: Results to cache
            ttl_seconds: TTL for this entry (or default)
        """
        # Evict if at capacity
        while len(self._cache) >= self._max_entries and self._access_order:
            oldest_key = self._access_order.pop(0)
            if oldest_key in self._cache:
                del self._cache[oldest_key]

        entry = CacheEntry(
            results=results,
            created_at=_utcnow(),
            ttl_seconds=ttl_seconds or self._default_ttl,
            query_key=query_key,
        )

        self._cache[query_key] = entry
        self._access_order.append(query_key)
        logger.debug(f"Cached {len(results)} results for {query_key}")

    def invalidate(self, query_key: str) -> bool:
        """
        Invalidate a specific cache entry.

        Args:
            query_key: Cache key to invalidate

        Returns:
            True if entry was found and removed
        """
        if query_key in self._cache:
            del self._cache[query_key]
            if query_key in self._access_order:
                self._access_order.remove(query_key)
            return True
        return False

    def invalidate_by_memory(self, memory_id: UUID) -> int:
        """
        Invalidate all cache entries containing a specific memory.

        Args:
            memory_id: Memory ID to invalidate

        Returns:
            Number of entries invalidated
        """
        keys_to_remove = []
        for key, entry in self._cache.items():
            if any(r.memory_id == memory_id for r in entry.results):
                keys_to_remove.append(key)

        for key in keys_to_remove:
            self.invalidate(key)

        if keys_to_remove:
            logger.debug(
                f"Invalidated {len(keys_to_remove)} cache entries for {memory_id}"
            )
        return len(keys_to_remove)

    def clear(self) -> int:
        """
        Clear all cache entries.

        Returns:
            Number of entries cleared
        """
        count = len(self._cache)
        self._cache.clear()
        self._access_order.clear()
        logger.info(f"Cleared {count} cache entries")
        return count

    def get_stats(self) -> dict[str, Any]:
        """Get cache statistics."""
        expired_count = sum(1 for e in self._cache.values() if e.is_expired())
        return {
            "total_entries": len(self._cache),
            "expired_entries": expired_count,
            "max_entries": self._max_entries,
            "default_ttl_seconds": self._default_ttl,
        }


class RetrievalEngine:
    """
    Hybrid retrieval engine for memory search.

    Combines multiple index types for comprehensive retrieval:
    - Vector search for semantic similarity
    - Temporal index for time-based filtering
    - Entity index for entity-based lookups
    - Outcome index for success/failure filtering

    Results are scored and ranked using relevance scoring.
    """

    def __init__(
        self,
        indexer: MemoryIndexer | None = None,
        scorer: RelevanceScorer | None = None,
        cache: RetrievalCache | None = None,
        enable_cache: bool = True,
    ) -> None:
        """
        Initialize the retrieval engine.

        Args:
            indexer: Memory indexer (defaults to singleton)
            scorer: Relevance scorer (defaults to new instance)
            cache: Retrieval cache (defaults to new instance)
            enable_cache: Whether to enable result caching
        """
        self._indexer = indexer or get_memory_indexer()
        self._scorer = scorer or RelevanceScorer()
        self._cache = cache or RetrievalCache() if enable_cache else None
        self._enable_cache = enable_cache
        logger.info(f"Initialized RetrievalEngine with cache={enable_cache}")

    async def retrieve(
        self,
        query: RetrievalQuery,
        use_cache: bool = True,
    ) -> RetrievalResult[ScoredResult]:
        """
        Retrieve relevant memories using hybrid search.

        Args:
            query: Retrieval query parameters
            use_cache: Whether to use cached results

        Returns:
            Retrieval result with scored items
        """
        start_time = _utcnow()

        # Check cache
        cache_key = query.to_cache_key()
        if use_cache and self._cache:
            cached = self._cache.get(cache_key)
            if cached:
                latency = (_utcnow() - start_time).total_seconds() * 1000
                return RetrievalResult(
                    items=cached,
                    total_count=len(cached),
                    query=query.query_text or "",
                    retrieval_type="cached",
                    latency_ms=latency,
                    metadata={"cache_hit": True},
                )

        # Collect candidates from each index
        candidates: dict[UUID, dict[str, Any]] = {}

        # Vector search
        if query.use_vector and query.query_embedding:
            vector_results = await self._indexer.vector_index.search(
                query=query.query_embedding,
                limit=query.limit * 3,  # Get more for filtering
                min_similarity=query.min_relevance,
                memory_type=query.memory_types[0] if query.memory_types else None,
            )
            for entry in vector_results:
                if entry.memory_id not in candidates:
                    candidates[entry.memory_id] = {
                        "memory_type": entry.memory_type,
                        "sources": [],
                    }
                candidates[entry.memory_id]["vector_similarity"] = entry.metadata.get(
                    "similarity", 0.5
                )
                candidates[entry.memory_id]["sources"].append("vector")

        # Temporal search
        if query.use_temporal and (
            query.start_time or query.end_time or query.recent_seconds
        ):
            temporal_results = await self._indexer.temporal_index.search(
                query=None,
                limit=query.limit * 3,
                start_time=query.start_time,
                end_time=query.end_time,
                recent_seconds=query.recent_seconds,
                memory_type=query.memory_types[0] if query.memory_types else None,
            )
            for temporal_entry in temporal_results:
                if temporal_entry.memory_id not in candidates:
                    candidates[temporal_entry.memory_id] = {
                        "memory_type": temporal_entry.memory_type,
                        "sources": [],
                    }
                candidates[temporal_entry.memory_id]["timestamp"] = (
                    temporal_entry.timestamp
                )
                candidates[temporal_entry.memory_id]["sources"].append("temporal")

        # Entity search
        if query.use_entity and query.entities:
            entity_results = await self._indexer.entity_index.search(
                query=None,
                limit=query.limit * 3,
                entities=query.entities,
                match_all=query.entity_match_all,
                memory_type=query.memory_types[0] if query.memory_types else None,
            )
            for entity_entry in entity_results:
                if entity_entry.memory_id not in candidates:
                    candidates[entity_entry.memory_id] = {
                        "memory_type": entity_entry.memory_type,
                        "sources": [],
                    }
                # Count entity matches
                entity_count = candidates[entity_entry.memory_id].get(
                    "entity_match_count", 0
                )
                candidates[entity_entry.memory_id]["entity_match_count"] = (
                    entity_count + 1
                )
                candidates[entity_entry.memory_id]["sources"].append("entity")

        # Outcome search
        if query.use_outcome and query.outcomes:
            outcome_results = await self._indexer.outcome_index.search(
                query=None,
                limit=query.limit * 3,
                outcomes=query.outcomes,
                memory_type=query.memory_types[0] if query.memory_types else None,
            )
            for outcome_entry in outcome_results:
                if outcome_entry.memory_id not in candidates:
                    candidates[outcome_entry.memory_id] = {
                        "memory_type": outcome_entry.memory_type,
                        "sources": [],
                    }
                candidates[outcome_entry.memory_id]["outcome"] = outcome_entry.outcome
                candidates[outcome_entry.memory_id]["sources"].append("outcome")

        # Score and rank candidates
        scored_results: list[ScoredResult] = []
        entity_total = len(query.entities) if query.entities else 1

        for memory_id, data in candidates.items():
            scored = self._scorer.score(
                memory_id=memory_id,
                memory_type=data["memory_type"],
                vector_similarity=data.get("vector_similarity"),
                timestamp=data.get("timestamp"),
                entity_match_count=data.get("entity_match_count", 0),
                entity_total=entity_total,
                outcome=data.get("outcome"),
                preferred_outcomes=query.outcomes,
            )
            scored.metadata["sources"] = data.get("sources", [])

            # Filter by minimum relevance
            if scored.relevance_score >= query.min_relevance:
                scored_results.append(scored)

        # Sort by relevance score
        scored_results.sort(key=lambda x: x.relevance_score, reverse=True)

        # Apply limit
        final_results = scored_results[: query.limit]

        # Cache results
        if use_cache and self._cache and final_results:
            self._cache.put(cache_key, final_results)

        latency = (_utcnow() - start_time).total_seconds() * 1000

        logger.info(
            f"Retrieved {len(final_results)} results from {len(candidates)} candidates "
            f"in {latency:.2f}ms"
        )

        return RetrievalResult(
            items=final_results,
            total_count=len(candidates),
            query=query.query_text or "",
            retrieval_type="hybrid",
            latency_ms=latency,
            metadata={
                "cache_hit": False,
                "candidates_count": len(candidates),
                "filtered_count": len(scored_results),
            },
        )

    async def retrieve_similar(
        self,
        embedding: list[float],
        limit: int = 10,
        min_similarity: float = 0.5,
        memory_types: list[MemoryType] | None = None,
    ) -> RetrievalResult[ScoredResult]:
        """
        Retrieve memories similar to a given embedding.

        Args:
            embedding: Query embedding
            limit: Maximum results
            min_similarity: Minimum similarity threshold
            memory_types: Filter by memory types

        Returns:
            Retrieval result with scored items
        """
        query = RetrievalQuery(
            query_embedding=embedding,
            limit=limit,
            min_relevance=min_similarity,
            memory_types=memory_types,
            use_temporal=False,
            use_entity=False,
            use_outcome=False,
        )
        return await self.retrieve(query)

    async def retrieve_recent(
        self,
        hours: float = 24,
        limit: int = 10,
        memory_types: list[MemoryType] | None = None,
    ) -> RetrievalResult[ScoredResult]:
        """
        Retrieve recent memories.

        Args:
            hours: Number of hours to look back
            limit: Maximum results
            memory_types: Filter by memory types

        Returns:
            Retrieval result with scored items
        """
        query = RetrievalQuery(
            recent_seconds=hours * 3600,
            limit=limit,
            memory_types=memory_types,
            use_vector=False,
            use_entity=False,
            use_outcome=False,
        )
        return await self.retrieve(query)

    async def retrieve_by_entity(
        self,
        entity_type: str,
        entity_value: str,
        limit: int = 10,
        memory_types: list[MemoryType] | None = None,
    ) -> RetrievalResult[ScoredResult]:
        """
        Retrieve memories by entity.

        Args:
            entity_type: Type of entity
            entity_value: Entity value
            limit: Maximum results
            memory_types: Filter by memory types

        Returns:
            Retrieval result with scored items
        """
        query = RetrievalQuery(
            entities=[(entity_type, entity_value)],
            limit=limit,
            memory_types=memory_types,
            use_vector=False,
            use_temporal=False,
            use_outcome=False,
        )
        return await self.retrieve(query)

    async def retrieve_successful(
        self,
        limit: int = 10,
        memory_types: list[MemoryType] | None = None,
    ) -> RetrievalResult[ScoredResult]:
        """
        Retrieve successful memories.

        Args:
            limit: Maximum results
            memory_types: Filter by memory types

        Returns:
            Retrieval result with scored items
        """
        query = RetrievalQuery(
            outcomes=[Outcome.SUCCESS],
            limit=limit,
            memory_types=memory_types,
            use_vector=False,
            use_temporal=False,
            use_entity=False,
        )
        return await self.retrieve(query)

    def invalidate_cache(self) -> int:
        """
        Invalidate all cached results.

        Returns:
            Number of entries invalidated
        """
        if self._cache:
            return self._cache.clear()
        return 0

    def invalidate_cache_for_memory(self, memory_id: UUID) -> int:
        """
        Invalidate cache entries containing a specific memory.

        Args:
            memory_id: Memory ID to invalidate

        Returns:
            Number of entries invalidated
        """
        if self._cache:
            return self._cache.invalidate_by_memory(memory_id)
        return 0

    def get_cache_stats(self) -> dict[str, Any]:
        """Get cache statistics."""
        if self._cache:
            return self._cache.get_stats()
        return {"enabled": False}


# Singleton retrieval engine instance
_engine: RetrievalEngine | None = None


def get_retrieval_engine() -> RetrievalEngine:
    """Get the singleton retrieval engine instance."""
    global _engine
    if _engine is None:
        _engine = RetrievalEngine()
    return _engine