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

Handles all database operations for decision logs, tracking important
decisions made during work for future reference.
"""

from typing import Optional
from uuid import UUID

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

from api.models.decision_log import DecisionLog
from api.schemas.decision_log import DecisionLogCreate, DecisionLogUpdate


def get_decision_logs(
    db: Session,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[DecisionLog], int]:
    """
    Retrieve a paginated list of decision logs.

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

    Returns:
        tuple: (list of decision logs, total count)
    """
    # Get total count
    total = db.query(DecisionLog).count()

    # Get paginated results, ordered by most recent first
    logs = (
        db.query(DecisionLog)
        .order_by(DecisionLog.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return logs, total


def get_decision_log_by_id(db: Session, log_id: UUID) -> DecisionLog:
    """
    Retrieve a single decision log by its ID.

    Args:
        db: Database session
        log_id: UUID of the decision log to retrieve

    Returns:
        DecisionLog: The decision log object

    Raises:
        HTTPException: 404 if decision log not found
    """
    log = db.query(DecisionLog).filter(DecisionLog.id == str(log_id)).first()

    if not log:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"DecisionLog with ID {log_id} not found"
        )

    return log


def get_decision_logs_by_project(
    db: Session,
    project_id: UUID,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[DecisionLog], int]:
    """
    Retrieve decision logs 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 decision logs, total count)
    """
    # Get total count for project
    total = db.query(DecisionLog).filter(
        DecisionLog.project_id == str(project_id)
    ).count()

    # Get paginated results
    logs = (
        db.query(DecisionLog)
        .filter(DecisionLog.project_id == str(project_id))
        .order_by(DecisionLog.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return logs, total


def get_decision_logs_by_session(
    db: Session,
    session_id: UUID,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[DecisionLog], int]:
    """
    Retrieve decision logs 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 decision logs, total count)
    """
    # Get total count for session
    total = db.query(DecisionLog).filter(
        DecisionLog.session_id == str(session_id)
    ).count()

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

    return logs, total


def get_decision_logs_by_impact(
    db: Session,
    impact: str,
    skip: int = 0,
    limit: int = 100
) -> tuple[list[DecisionLog], int]:
    """
    Retrieve decision logs filtered by impact level.

    Args:
        db: Database session
        impact: Impact level (low, medium, high, critical)
        skip: Number of records to skip
        limit: Maximum number of records to return

    Returns:
        tuple: (list of decision logs, total count)
    """
    # Validate impact level
    valid_impacts = ["low", "medium", "high", "critical"]
    if impact.lower() not in valid_impacts:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=f"Invalid impact level. Must be one of: {', '.join(valid_impacts)}"
        )

    # Get total count for impact
    total = db.query(DecisionLog).filter(
        DecisionLog.impact == impact.lower()
    ).count()

    # Get paginated results
    logs = (
        db.query(DecisionLog)
        .filter(DecisionLog.impact == impact.lower())
        .order_by(DecisionLog.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return logs, total


def create_decision_log(
    db: Session,
    log_data: DecisionLogCreate
) -> DecisionLog:
    """
    Create a new decision log.

    Args:
        db: Database session
        log_data: Decision log creation data

    Returns:
        DecisionLog: The created decision log object

    Raises:
        HTTPException: 500 if database error occurs
    """
    try:
        # Create new decision log instance
        db_log = DecisionLog(**log_data.model_dump())

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

        return db_log

    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 decision log: {str(e)}"
        )


def update_decision_log(
    db: Session,
    log_id: UUID,
    log_data: DecisionLogUpdate
) -> DecisionLog:
    """
    Update an existing decision log.

    Args:
        db: Database session
        log_id: UUID of the decision log to update
        log_data: Decision log update data

    Returns:
        DecisionLog: The updated decision log object

    Raises:
        HTTPException: 404 if decision log not found
        HTTPException: 500 if database error occurs
    """
    # Get existing log
    log = get_decision_log_by_id(db, log_id)

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

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

        db.commit()
        db.refresh(log)

        return log

    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 decision log: {str(e)}"
        )


def delete_decision_log(db: Session, log_id: UUID) -> dict:
    """
    Delete a decision log by its ID.

    Args:
        db: Database session
        log_id: UUID of the decision log to delete

    Returns:
        dict: Success message

    Raises:
        HTTPException: 404 if decision log not found
        HTTPException: 500 if database error occurs
    """
    # Get existing log (raises 404 if not found)
    log = get_decision_log_by_id(db, log_id)

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

        return {
            "message": "DecisionLog deleted successfully",
            "log_id": str(log_id)
        }

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