"""
Weather data sync - fetches daily weather from Open-Meteo archive API (ERA5).
Location: Stow on the Wold, GL54 1JX (lat=51.9253, lon=-1.7272, elev=230m).
No API key required. Stores one row per day, upserts on re-fetch.
"""
import logging
from datetime import date, timedelta
from typing import Optional

import httpx
from dateutil.relativedelta import relativedelta
from sqlalchemy import text

from database import SyncSessionLocal

logger = logging.getLogger(__name__)

OPEN_METEO_URL = "https://archive-api.open-meteo.com/v1/archive"

# Fallback defaults — overridden by system_config at runtime
_DEFAULT_LATITUDE = 51.9253
_DEFAULT_LONGITUDE = -1.7272
_DEFAULT_TIMEZONE = "Europe/London"

DAILY_VARIABLES = [
    "temperature_2m_max",
    "temperature_2m_min",
    "temperature_2m_mean",
    "precipitation_sum",
    "rain_sum",
    "snowfall_sum",
    "snow_depth_max",
    "windspeed_10m_max",
    "sunshine_duration",
    "weathercode",
]


async def sync_weather_data(
    from_date: date,
    to_date: date,
    triggered_by: str = "scheduler"
) -> dict:
    """Fetch daily weather from Open-Meteo and upsert into weather_data."""
    logger.info(f"Starting weather sync {from_date} to {to_date}")

    db = SyncSessionLocal()
    try:
        # Read location config from system_config (falls back to defaults if not set)
        cfg_result = db.execute(
            text("""
            SELECT config_key, config_value FROM system_config
            WHERE config_key IN ('weather_latitude', 'weather_longitude', 'weather_timezone')
            """)
        )
        cfg = {row.config_key: row.config_value for row in cfg_result.fetchall()}
        latitude = float(cfg.get("weather_latitude") or _DEFAULT_LATITUDE)
        longitude = float(cfg.get("weather_longitude") or _DEFAULT_LONGITUDE)
        timezone = cfg.get("weather_timezone") or _DEFAULT_TIMEZONE

        db.execute(
            text("""
            INSERT INTO sync_log (sync_type, source, started_at, status, date_from, date_to, triggered_by)
            VALUES ('weather', 'open_meteo', NOW(), 'running', :from_date, :to_date, :triggered_by)
            """),
            {"from_date": from_date, "to_date": to_date, "triggered_by": triggered_by}
        )
        db.commit()

        params = {
            "latitude": latitude,
            "longitude": longitude,
            "start_date": from_date.isoformat(),
            "end_date": to_date.isoformat(),
            "daily": ",".join(DAILY_VARIABLES),
            "timezone": timezone,
        }

        async with httpx.AsyncClient(timeout=30.0) as client:
            response = await client.get(OPEN_METEO_URL, params=params)
            response.raise_for_status()
            data = response.json()

        daily = data.get("daily", {})
        dates = daily.get("time", [])

        if not dates:
            raise Exception("No data returned from Open-Meteo API")

        records_upserted = 0

        for i, date_str in enumerate(dates):
            def val(key, idx=i):
                v = daily.get(key, [])
                return v[idx] if idx < len(v) else None

            sunshine_s = val("sunshine_duration")
            sunshine_h = round(sunshine_s / 3600, 2) if sunshine_s is not None else None

            db.execute(
                text("""
                INSERT INTO weather_data (
                    date,
                    temperature_max, temperature_min, temperature_mean,
                    precipitation_sum, rain_sum, snowfall_sum, snow_depth_max,
                    windspeed_max, sunshine_hours, weathercode,
                    fetched_at
                ) VALUES (
                    :date,
                    :temp_max, :temp_min, :temp_mean,
                    :precip, :rain, :snowfall, :snow_depth,
                    :wind, :sunshine, :weathercode,
                    NOW()
                )
                ON CONFLICT (date) DO UPDATE SET
                    temperature_max = :temp_max,
                    temperature_min = :temp_min,
                    temperature_mean = :temp_mean,
                    precipitation_sum = :precip,
                    rain_sum = :rain,
                    snowfall_sum = :snowfall,
                    snow_depth_max = :snow_depth,
                    windspeed_max = :wind,
                    sunshine_hours = :sunshine,
                    weathercode = :weathercode,
                    fetched_at = NOW()
                """),
                {
                    "date": date_str,
                    "temp_max": val("temperature_2m_max"),
                    "temp_min": val("temperature_2m_min"),
                    "temp_mean": val("temperature_2m_mean"),
                    "precip": val("precipitation_sum"),
                    "rain": val("rain_sum"),
                    "snowfall": val("snowfall_sum"),
                    "snow_depth": val("snow_depth_max"),
                    "wind": val("windspeed_10m_max"),
                    "sunshine": sunshine_h,
                    "weathercode": val("weathercode"),
                }
            )
            records_upserted += 1

        db.commit()

        db.execute(
            text("""
            UPDATE sync_log
            SET completed_at = NOW(), status = 'success',
                records_fetched = :fetched, records_created = :created
            WHERE id = (
                SELECT id FROM sync_log
                WHERE source = 'open_meteo' AND status = 'running'
                ORDER BY started_at DESC LIMIT 1
            )
            """),
            {"fetched": len(dates), "created": records_upserted}
        )
        db.commit()

        logger.info(f"Weather sync completed: {records_upserted} days upserted")
        return {"records_fetched": len(dates), "records_upserted": records_upserted}

    except Exception as e:
        logger.error(f"Weather sync failed: {e}")
        try:
            db.rollback()
            db.execute(
                text("""
                UPDATE sync_log
                SET completed_at = NOW(), status = 'failed', error_message = :error
                WHERE id = (
                    SELECT id FROM sync_log
                    WHERE source = 'open_meteo' AND status = 'running'
                    ORDER BY started_at DESC LIMIT 1
                )
                """),
                {"error": str(e)[:500]}
            )
            db.commit()
        except Exception as log_error:
            logger.error(f"Failed to update sync_log: {log_error}")
        raise
    finally:
        db.close()


async def run_weather_sync(triggered_by: str = "scheduler"):
    """Daily scheduled sync — last 7 days to catch ERA5 corrections."""
    from_date = date.today() - timedelta(days=7)
    to_date = date.today()
    await sync_weather_data(from_date, to_date, triggered_by=triggered_by)


async def run_weather_backfill(
    from_date: date,
    to_date: date,
    triggered_by: str = "manual"
) -> dict:
    """Backfill in 6-month chunks so progress is logged incrementally."""
    logger.info(f"Starting weather backfill {from_date} to {to_date}")
    total_upserted = 0

    chunk_start = from_date
    while chunk_start <= to_date:
        chunk_end = min(chunk_start + relativedelta(months=6) - timedelta(days=1), to_date)
        logger.info(f"Weather backfill chunk: {chunk_start} to {chunk_end}")
        result = await sync_weather_data(chunk_start, chunk_end, triggered_by=triggered_by)
        total_upserted += result.get("records_upserted", 0)
        chunk_start = chunk_end + timedelta(days=1)

    logger.info(f"Weather backfill complete: {total_upserted} total days")
    return {"records_upserted": total_upserted}