from typing import Iterable
from backend.app.db.models.energy_assessments import (
    EnergyAssessment, EnergyAssessmentScenarios, EnergyAssessmentDocuments, DocumentTypeEnum
)
from sqlalchemy.orm import Session
from sqlalchemy.exc import IntegrityError
from typing import Optional, List, Dict
from sqlalchemy import desc
from utils.logger import setup_logger

logger = setup_logger()


def bulk_insert_energy_assessments(session: Session, data_list: List[dict]) -> Dict[int, int]:
    """
    This function inserts or updates multiple energy assessment records into the database and returns a mapping of
    uprn to energy_assessment_id.

    :param session: The SQLAlchemy session.
    :param data_list: A list of dictionaries containing energy assessment data.
    :return: A dictionary mapping each uprn to its corresponding energy_assessment_id.
    """
    uprn_to_assessment_id = {}

    try:
        for data in data_list:
            uprn = data.get('uprn')
            inspection_date = data.get('inspection_date')

            # Check if a record with the same uprn and inspection_date exists
            existing_record = session.query(EnergyAssessment).filter_by(
                uprn=uprn,
                inspection_date=inspection_date
            ).first()

            if existing_record:
                # Update the existing record with new data
                for key, value in data.items():
                    setattr(existing_record, key, value)
                session.add(existing_record)

                # Map the uprn to the existing record's ID
                uprn_to_assessment_id[uprn] = existing_record.id
            else:
                # Insert a new record
                new_assessment = EnergyAssessment(**data)
                session.add(new_assessment)

                # Flush the session to get the newly created ID before commit
                session.flush()

                # Map the uprn to the new record's ID
                uprn_to_assessment_id[uprn] = new_assessment.id

        # Commit the transaction
        session.commit()
        logger.info("All records inserted or updated successfully.")

    except IntegrityError as e:
        # Rollback the session in case of error
        session.rollback()
        logger.info(f"Error occurred: {e}")

    return uprn_to_assessment_id


def get_latest_assessments_for_uprns(
    session: Session,
    uprns: Iterable[int],
) -> dict[int, dict]:
    """
    Fetch the latest energy assessment per UPRN in a single query.

    Returns a dict:
        uprn -> assessment_dict | empty_response
    """

    uprns = [u for u in uprns if u]
    if not uprns:
        return {}

    # DISTINCT ON requires matching ORDER BY
    records = (
        session.query(EnergyAssessment)
        .filter(EnergyAssessment.uprn.in_(uprns))
        .order_by(
            EnergyAssessment.uprn,
            desc(EnergyAssessment.inspection_date),
        )
        .distinct(EnergyAssessment.uprn)
        .all()
    )

    result: dict[int, dict] = {}

    for record in records:
        result[record.uprn] = record.to_dict()

    # Fill missing uprns with empty response
    uprn_set = set(uprns)
    found_set = set(result.keys())

    missing_uprns = uprn_set - found_set

    for uprn in missing_uprns:
        result[uprn] = EnergyAssessment.empty_response()

    return result


def create_scenarios_for_documents(session: Session, document_list: List[dict], uprn_to_assessment_id: dict):
    """
    Creates scenarios for documents by UPRN and links them to the energy assessments.

    :param session: The SQLAlchemy session.
    :param document_list: A list of dictionaries containing document data.
    :param uprn_to_assessment_id: A dictionary mapping UPRN to energy_assessment_id.
    """
    try:
        for document in document_list:
            uprn = document.get('uprn')
            scenario_name = document.get('scenario_id')

            if scenario_name:
                # Get the associated energy_assessment_id for the UPRN
                energy_assessment_id = uprn_to_assessment_id.get(uprn)

                # Check if the scenario already exists
                existing_scenario = session.query(EnergyAssessmentScenarios).filter_by(
                    scenario_name=scenario_name,
                    energy_assessment_id=energy_assessment_id
                ).first()

                if not existing_scenario:
                    # Create the scenario
                    new_scenario = EnergyAssessmentScenarios(
                        scenario_name=scenario_name,
                        energy_assessment_id=energy_assessment_id
                    )
                    session.add(new_scenario)
                    session.flush()  # Get the new scenario ID

                    # Update document with new scenario ID
                    document['scenario_id'] = new_scenario.id
                else:
                    # If the scenario already exists, just use its ID
                    document['scenario_id'] = existing_scenario.id

        # Commit the scenarios
        session.commit()
        logger.info("Scenarios created successfully.")

    except IntegrityError as e:
        session.rollback()
        logger.info(f"Error occurred: {e}")


def create_documents(session: Session, document_list: List[dict]):
    """
    Inserts documents into the energy_assessment_documents table, linking them to scenarios and assessments.

    :param session: The SQLAlchemy session.
    :param document_list: A list of dictionaries containing document data.
    """
    try:
        for document in document_list:
            # Ensure the document_type is cast to Enum
            new_document = EnergyAssessmentDocuments(
                uprn=document['uprn'],
                document_type=DocumentTypeEnum(document['document_type']).value,
                document_location=document['document_location'],
                energy_assessment_id=document['energy_assessment_id'],
                scenario_id=document.get('scenario_id')  # Might be None if no scenario
            )

            session.add(new_document)

        # Commit all document insertions
        session.commit()
        logger.info("Documents created successfully.")

    except IntegrityError as e:
        session.rollback()
        logger.info(f"Error occurred: {e}")