"""
ConversationContext service layer for business logic and database operations.

Handles all database operations for conversation contexts, providing context
recall and retrieval functionality for Claude's memory system.
"""

import json
from typing import List, Optional
from uuid import UUID

from fastapi import HTTPException, status
from sqlalchemy import or_
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from api.models.conversation_context import ConversationContext
from api.schemas.conversation_context import ConversationContextCreate, ConversationContextUpdate
from api.utils.context_compression import format_for_injection


def get_conversation_contexts(
    db: Session,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[ConversationContext], int]:
    """
    Retrieve a paginated list of conversation contexts.

    Args:
        db: Database session
        skip: Number of records to skip (for pagination)
        limit: Maximum number of records to return

    Returns:
        tuple: (list of conversation contexts, total count)
    """
    # Get total count
    total = db.query(ConversationContext).count()

    # Get paginated results, ordered by relevance and recency
    contexts = (
        db.query(ConversationContext)
        .order_by(ConversationContext.relevance_score.desc(), ConversationContext.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return contexts, total


def get_conversation_context_by_id(db: Session, context_id: UUID) -> ConversationContext:
    """
    Retrieve a single conversation context by its ID.

    Args:
        db: Database session
        context_id: UUID of the conversation context to retrieve

    Returns:
        ConversationContext: The conversation context object

    Raises:
        HTTPException: 404 if conversation context not found
    """
    context = db.query(ConversationContext).filter(ConversationContext.id == str(context_id)).first()

    if not context:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"ConversationContext with ID {context_id} not found"
        )

    return context


def get_conversation_contexts_by_project(
    db: Session,
    project_id: UUID,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[ConversationContext], int]:
    """
    Retrieve conversation contexts for a specific project.

    Args:
        db: Database session
        project_id: UUID of the project
        skip: Number of records to skip
        limit: Maximum number of records to return

    Returns:
        tuple: (list of conversation contexts, total count)
    """
    # Get total count for project
    total = db.query(ConversationContext).filter(
        ConversationContext.project_id == str(project_id)
    ).count()

    # Get paginated results
    contexts = (
        db.query(ConversationContext)
        .filter(ConversationContext.project_id == str(project_id))
        .order_by(ConversationContext.relevance_score.desc(), ConversationContext.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return contexts, total


def get_conversation_contexts_by_session(
    db: Session,
    session_id: UUID,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[ConversationContext], int]:
    """
    Retrieve conversation contexts for a specific session.

    Args:
        db: Database session
        session_id: UUID of the session
        skip: Number of records to skip
        limit: Maximum number of records to return

    Returns:
        tuple: (list of conversation contexts, total count)
    """
    # Get total count for session
    total = db.query(ConversationContext).filter(
        ConversationContext.session_id == str(session_id)
    ).count()

    # Get paginated results
    contexts = (
        db.query(ConversationContext)
        .filter(ConversationContext.session_id == str(session_id))
        .order_by(ConversationContext.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return contexts, total


def get_recall_context(
    db: Session,
    project_id: Optional[UUID] = None,
    tags: Optional[List[str]] = None,
    limit: int = 10,
    min_relevance_score: float = 5.0
) -> str:
    """
    Get relevant contexts formatted for Claude prompt injection.

    This is the main context recall function that retrieves the most relevant
    contexts and formats them for efficient injection into Claude's prompt.

    Args:
        db: Database session
        project_id: Optional project ID to filter by
        tags: Optional list of tags to filter by
        limit: Maximum number of contexts to retrieve (default 10)
        min_relevance_score: Minimum relevance score threshold (default 5.0)

    Returns:
        str: Token-efficient markdown string ready for prompt injection
    """
    # Build query
    query = db.query(ConversationContext)

    # Filter by project if specified
    if project_id:
        query = query.filter(ConversationContext.project_id == str(project_id))

    # Filter by minimum relevance score
    query = query.filter(ConversationContext.relevance_score >= min_relevance_score)

    # Filter by tags if specified
    if tags:
        # Check if any of the provided tags exist in the JSON tags field
        # This uses PostgreSQL's JSON operators
        tag_filters = []
        for tag in tags:
            tag_filters.append(ConversationContext.tags.contains(f'"{tag}"'))
        if tag_filters:
            query = query.filter(or_(*tag_filters))

    # Order by relevance score and get top results
    contexts = query.order_by(
        ConversationContext.relevance_score.desc()
    ).limit(limit).all()

    # Convert to dictionary format for formatting
    context_dicts = []
    for ctx in contexts:
        context_dict = {
            "content": ctx.dense_summary or ctx.title,
            "type": ctx.context_type,
            "tags": json.loads(ctx.tags) if ctx.tags else [],
            "relevance_score": ctx.relevance_score
        }
        context_dicts.append(context_dict)

    # Use compression utility to format for injection
    return format_for_injection(context_dicts)


def create_conversation_context(
    db: Session,
    context_data: ConversationContextCreate
) -> ConversationContext:
    """
    Create a new conversation context.

    Args:
        db: Database session
        context_data: Conversation context creation data

    Returns:
        ConversationContext: The created conversation context object

    Raises:
        HTTPException: 500 if database error occurs
    """
    try:
        # Create new conversation context instance
        db_context = ConversationContext(**context_data.model_dump())

        # Add to database
        db.add(db_context)
        db.commit()
        db.refresh(db_context)

        return db_context

    except IntegrityError as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Database error: {str(e)}"
        )
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to create conversation context: {str(e)}"
        )


def update_conversation_context(
    db: Session,
    context_id: UUID,
    context_data: ConversationContextUpdate
) -> ConversationContext:
    """
    Update an existing conversation context.

    Args:
        db: Database session
        context_id: UUID of the conversation context to update
        context_data: Conversation context update data

    Returns:
        ConversationContext: The updated conversation context object

    Raises:
        HTTPException: 404 if conversation context not found
        HTTPException: 500 if database error occurs
    """
    # Get existing context
    context = get_conversation_context_by_id(db, context_id)

    try:
        # Update only provided fields
        update_data = context_data.model_dump(exclude_unset=True)

        # Apply updates
        for field, value in update_data.items():
            setattr(context, field, value)

        db.commit()
        db.refresh(context)

        return context

    except HTTPException:
        db.rollback()
        raise
    except IntegrityError as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Database error: {str(e)}"
        )
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to update conversation context: {str(e)}"
        )


def delete_conversation_context(db: Session, context_id: UUID) -> dict:
    """
    Delete a conversation context by its ID.

    Args:
        db: Database session
        context_id: UUID of the conversation context to delete

    Returns:
        dict: Success message

    Raises:
        HTTPException: 404 if conversation context not found
        HTTPException: 500 if database error occurs
    """
    # Get existing context (raises 404 if not found)
    context = get_conversation_context_by_id(db, context_id)

    try:
        db.delete(context)
        db.commit()

        return {
            "message": "ConversationContext deleted successfully",
            "context_id": str(context_id)
        }

    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to delete conversation context: {str(e)}"
        )