"""
BIGQUERY DATA SOURCE BASE CLASS
Kimball Data Warehouse Architecture

Layer Assignment:
    RAW     (Bronze) → Tempat load data mentah dari sumber eksternal
    STAGING (Silver) → etl_logs, etl_metadata (via helpers)
    DW      (Gold)   → dim_*, fact_* (di file terpisah)

Subclass yang menggunakan DataSource:
    FAODataSource       → load ke RAW (Bronze) : raw_fao
    WorldBankDataSource → load ke RAW (Bronze) : raw_worldbank
    UNICEFDataSource    → load ke RAW (Bronze) : raw_unicef
"""

from abc import ABC, abstractmethod
import pandas as pd
import logging
from datetime import datetime
from typing import Dict
import json

from scripts.bigquery_config import get_bigquery_client, get_table_id, table_exists, CONFIG
from scripts.bigquery_helpers import log_update, load_to_bigquery, read_from_bigquery, save_etl_metadata
from google.cloud import bigquery


class DataSource(ABC):
    """
    Abstract base class untuk semua sumber data dengan template ETL pattern.
    Menggunakan Kimball DW methodology.

    Kimball Flow untuk setiap DataSource:
        fetch_data()        → Extract dari sumber eksternal (FAO/WB/UNICEF)
        transform_data()    → Transform ke format standar
        validate_data()     → Cek kualitas data
        load_to_database()  → Load ke RAW layer (Bronze)
        save_metadata()     → Simpan metadata ke AUDIT layer

    Subclass wajib implement:
        fetch_data()
        transform_data()
    """

    def __init__(self, client: bigquery.Client = None):
        self.client           = client if client else get_bigquery_client()
        self.logger           = logging.getLogger(self.__class__.__name__)
        self.logger.propagate = False

        self.data            = None
        self.table_name      = None
        self.target_layer    = "bronze"
        self.asean_countries = CONFIG['asean_countries']

        self.metadata = {
            'source_class'       : self.__class__.__name__,
            'table_name'         : None,
            'execution_timestamp': None,
            'duration_seconds'   : None,
            'rows_fetched'       : 0,
            'rows_transformed'   : 0,
            'rows_loaded'        : 0,
            'completeness_pct'   : 0,
            'config_snapshot'    : json.dumps({
                'threshold': float(CONFIG['matching']['threshold']),
                'weights'  : {k: float(v) for k, v in CONFIG['matching']['weights'].items()}
            }),
            'validation_metrics' : '{}'
        }

    @abstractmethod
    def fetch_data(self) -> pd.DataFrame:
        pass

    @abstractmethod
    def transform_data(self, df: pd.DataFrame) -> pd.DataFrame:
        pass

    def validate_data(self, df: pd.DataFrame) -> Dict:
        validation = {
            'total_rows'      : int(len(df)),
            'total_columns'   : int(len(df.columns)),
            'null_count'      : {k: int(v) for k, v in df.isnull().sum().to_dict().items()},
            'null_percentage' : {
                k: float(v)
                for k, v in (df.isnull().sum() / len(df) * 100).round(2).to_dict().items()
            },
            'duplicate_count' : int(df.duplicated().sum()),
            'completeness_pct': float(round((1 - df.isnull().sum().sum() / df.size) * 100, 2)),
            'memory_usage_mb' : float(round(df.memory_usage(deep=True).sum() / 1024**2, 2))
        }

        year_cols = [col for col in df.columns if 'year' in col.lower() or 'tahun' in col.lower()]
        if year_cols:
            year_col = year_cols[0]
            validation['year_range'] = {
                'min'         : int(df[year_col].min()) if not df[year_col].isnull().all() else None,
                'max'         : int(df[year_col].max()) if not df[year_col].isnull().all() else None,
                'unique_years': int(df[year_col].nunique())
            }

        return validation

    def load_to_database(self, df: pd.DataFrame, table_name: str):
        try:
            load_to_bigquery(
                self.client,
                df,
                table_name,
                layer='bronze',
                write_disposition="WRITE_TRUNCATE"
            )

            log_update(
                self.client,
                layer='RAW',
                table_name=table_name,
                update_method='full_refresh',
                rows_affected=len(df)
            )

        except Exception as e:
            log_update(
                self.client,
                layer='RAW',
                table_name=table_name,
                update_method='full_refresh',
                rows_affected=0,
                status='failed',
                error_msg=str(e)
            )
            raise

    def save_metadata(self):
        try:
            self.metadata['table_name'] = self.table_name

            if isinstance(self.metadata.get('validation_metrics'), dict):
                self.metadata['validation_metrics'] = json.dumps(
                    self.metadata['validation_metrics']
                )

            save_etl_metadata(self.client, self.metadata)

        except Exception as e:
            self.logger.warning(f"Failed to save ETL metadata to AUDIT: {str(e)}")

    def run(self) -> pd.DataFrame:
        start_time = datetime.now()
        self.metadata['execution_timestamp'] = start_time

        try:
            # 1. EXTRACT
            raw_data = self.fetch_data()
            self.metadata['rows_fetched'] = len(raw_data) if hasattr(raw_data, '__len__') else 0

            # 2. TRANSFORM
            self.data = self.transform_data(raw_data)
            self.metadata['rows_transformed'] = len(self.data)

            # 3. VALIDATE
            validation = self.validate_data(self.data)
            self.metadata['completeness_pct']   = validation.get('completeness_pct', 0)
            self.metadata['validation_metrics'] = json.dumps({
                'total_rows'      : validation['total_rows'],
                'completeness_pct': validation['completeness_pct'],
                'duplicate_count' : validation['duplicate_count']
            })

            # 4. LOAD → RAW layer (Bronze)
            self.load_to_database(self.data, self.table_name)
            self.metadata['rows_loaded'] = len(self.data)

            # 5. METADATA → AUDIT layer
            end_time = datetime.now()
            self.metadata['duration_seconds'] = (end_time - start_time).total_seconds()
            self.save_metadata()

            return self.data

        except Exception as e:
            raise


print("DataSource base class loaded — Kimball DW Architecture")
print("  Default target layer : RAW (Bronze)")
print("  Audit logs           : AUDIT via etl_logs")
print("  ETL metadata         : AUDIT via etl_metadata")