"""
Fetchers retrieve remote data and return it in a format suitable for further processing, they also return its version, which should be considered opaque, though it is usually a checksum.
"""

import sqlite3
from typing import Tuple
import pandas as pd
import requests
import hashlib
import io
import zipfile
from .run import Run
from .logger import logger

def fetch_onet_database(run: Run) -> Tuple[sqlite3.Connection, str]:
    """
    Downloads the O*NET database, creates a local SQLite file from it, and returns a connection.
    The version is the sha256 of the downloaded zip file.
    """
    url = "https://www.onetcenter.org/dl_files/database/db_29_1_mysql.zip"
    logger.info(f"Downloading O*NET database from {url}")
    response = requests.get(url, stream=True)
    response.raise_for_status()

    # Read content into memory
    zip_content = response.content
    version = hashlib.sha256(zip_content).hexdigest()
    logger.info(f"O*NET database version (sha256): {version}")

    db_path = run.cache_dir / f"onet_{version}.db"

    if db_path.exists():
        logger.info(f"Using cached O*NET database: {db_path}")
        conn = sqlite3.connect(db_path)
        # Set PRAGMA for foreign keys on every connection
        conn.execute("PRAGMA foreign_keys = ON;")
        return conn, version

    logger.info(f"Creating new O*NET database: {db_path}")
    conn = sqlite3.connect(db_path)

    # Set performance PRAGMAs for fast import
    logger.info("Creating new SQLite database with performance settings")
    conn.executescript("""
        PRAGMA journal_mode = OFF;
        PRAGMA synchronous = 0;
        PRAGMA cache_size = 1000000;
        PRAGMA locking_mode = EXCLUSIVE;
        PRAGMA temp_store = MEMORY;
        PRAGMA foreign_keys = ON;
    """)

    with zipfile.ZipFile(io.BytesIO(zip_content)) as z:
        sql_scripts = []
        for filename in sorted(z.namelist()):
            if filename.endswith(".sql"):
                sql_scripts.append(z.read(filename).decode('utf-8'))

        if not sql_scripts:
            raise RuntimeError("No SQL files found in the O*NET zip archive.")

        # Combine and execute all SQL files in one transaction
        full_script = "BEGIN TRANSACTION;\n" + "\n".join(sql_scripts) + "\nCOMMIT;"

        logger.info("Executing SQL files in alphabetical order (single transaction mode)")
        conn.executescript(full_script)
        logger.info("Database populated successfully. Restoring reliability settings...")

    # Restore reliability-focused settings after import
    conn.executescript("""
        PRAGMA journal_mode = WAL;
        PRAGMA synchronous = NORMAL;
        PRAGMA locking_mode = NORMAL;
        PRAGMA temp_store = DEFAULT;
        PRAGMA foreign_keys = ON;
        PRAGMA optimize;
    """)
    conn.execute("VACUUM;")
    conn.commit()
    logger.info("Reliability settings restored and database optimized successfully!")

    return conn, version

def fetch_oesm_data(run: Run) -> Tuple[pd.DataFrame, str]:
    """
    Downloads the OESM national data from the BLS website.
    The version is the sha256 of the downloaded zip file.
    """
    url = "https://www.bls.gov/oes/special-requests/oesm23nat.zip"
    logger.info(f"Downloading OESM data from {url}")
    response = requests.get(url)
    response.raise_for_status()

    zip_content = response.content
    version = hashlib.sha256(zip_content).hexdigest()
    logger.info(f"OESM data version (sha256): {version}")

    parquet_path = run.cache_dir / f"oesm_{version}.parquet"
    if parquet_path.exists():
        logger.info(f"Using cached OESM data: {parquet_path}")
        return pd.read_parquet(parquet_path), version

    logger.info(f"Creating new OESM data cache: {parquet_path}")
    with zipfile.ZipFile(io.BytesIO(zip_content)) as z:
        # Find the excel file in the zip
        excel_filename = None
        for filename in z.namelist():
            logger.debug(f"Found file in OESM zip: {filename}")
            if filename.lower().endswith(".xlsx"):
                excel_filename = filename
                break

        if excel_filename is None:
            raise FileNotFoundError("Could not find the Excel file in the OESM zip archive.")

        logger.info(f"Reading {excel_filename} from zip archive.")
        with z.open(excel_filename) as f:
            df = pd.read_excel(f, engine='openpyxl')

    df.to_parquet(parquet_path)
    logger.info(f"Saved OESM data to cache: {parquet_path}")
    return df, version

def fetch_epoch_remote_data(run: Run) -> Tuple[pd.DataFrame, str]:
    """
    Downloads the EPOCH AI remote work task data.
    The version is the sha256 of the downloaded CSV file.
    """
    # This is the direct download link constructed from the Google Drive share link
    url = "https://drive.google.com/uc?export=download&id=1GrHhuYIgaCCgo99dZ_40BWraz-fzo76r"
    logger.info(f"Downloading EPOCH remote data from Google Drive: {url}")

    # Need to handle potential cookies/redirects from Google Drive
    session = requests.Session()
    response = session.get(url, stream=True)
    response.raise_for_status()

    csv_content = response.content
    version = hashlib.sha256(csv_content).hexdigest()
    logger.info(f"EPOCH remote data version (sha256): {version}")

    parquet_path = run.cache_dir / f"epoch_remote_{version}.parquet"
    if parquet_path.exists():
        logger.info(f"Using cached EPOCH remote data: {parquet_path}")
        return pd.read_parquet(parquet_path), version

    logger.info(f"Creating new EPOCH remote data cache: {parquet_path}")
    df = pd.read_csv(io.BytesIO(csv_content))
    df.to_parquet(parquet_path)
    logger.info(f"Saved EPOCH remote data to cache: {parquet_path}")

    return df, version