from sqlalchemy import text
from datetime import datetime

class StationProfile:
    def __init__(self):
        pass

    async def backfill_address_if_missing(self, session, station_hash, station_name, address):
        sql = """
        UPDATE t_station_profile_scd
        SET address = :address,
            station_name = :station_name
        WHERE station_hash = :station_hash
          AND (address IS NULL OR address = '')
        """
        result = await session.execute(text(sql), {
            "station_hash": station_hash,
            "station_name": station_name,
            "address": address
        })
        try:
            return int(result.rowcount or 0)
        except Exception:
            return 0

    async def save(self, session, id, station_hash, operator, station_name, address=None, coord_x=None, coord_y=None, valid_start_time=None):
        if valid_start_time is None:
            valid_start_time = datetime.now()

        # 1. Check current record
        select_sql = """
        SELECT operator, station_name, address, coord_x, coord_y 
        FROM t_station_profile_scd 
        WHERE station_hash = :station_hash AND is_current = 1
        """
        result = await session.execute(text(select_sql), {"station_hash": station_hash})
        current_row = result.fetchone()

        if current_row:
            if address is not None and address != "" and (current_row.address is None or current_row.address == ""):
                await self.backfill_address_if_missing(
                    session=session,
                    station_hash=station_hash,
                    station_name=station_name,
                    address=address
                )
                return

            # Merge logic: if new value is None, use old value
            # But we must respect if new value is explicitly provided (even empty string?)
            # Usually for crawler:
            # - station_name: always updated
            # - address: if new is None, use old.
            # - coord: if new is None, use old.
            
            merged_address = address if address is not None else current_row.address
            merged_coord_x = coord_x if coord_x is not None else current_row.coord_x
            merged_coord_y = coord_y if coord_y is not None else current_row.coord_y
            
            # Use merged values for comparison and insertion
            address = merged_address
            coord_x = merged_coord_x
            coord_y = merged_coord_y
            
            # Check if changed
            # Need to handle potential float/decimal diffs for coords if needed, 
            # but usually they are float in DB and float in python.
            
            is_same = (
                current_row.operator == operator and
                current_row.station_name == station_name and
                current_row.address == address and
                current_row.coord_x == coord_x and
                current_row.coord_y == coord_y
            )
            
            if is_same:
                return

            # Expire old record
            update_sql = """
            UPDATE t_station_profile_scd 
            SET is_current = 0, valid_end_time = :valid_start_time 
            WHERE station_hash = :station_hash AND is_current = 1
            """
            await session.execute(text(update_sql), {
                "valid_start_time": valid_start_time,
                "station_hash": station_hash
            })

        # 2. Insert new record (with potentially merged values)
        sql = """
        INSERT INTO t_station_profile_scd 
        (id, station_hash, operator, station_name, address, coord_x, coord_y, valid_start_time, is_current)
        VALUES 
        (:id, :station_hash, :operator, :station_name, :address, :coord_x, :coord_y, :valid_start_time, 1)
        """
        await session.execute(text(sql), {
            "id": id,
            "station_hash": station_hash,
            "operator": operator,
            "station_name": station_name,
            "address": address,
            "coord_x": coord_x,
            "coord_y": coord_y,
            "valid_start_time": valid_start_time
        })