from sqlalchemy import text
from datetime import datetime
import json

class StationPriceSchedule:
    def __init__(self):
        pass

    async def save(self, session, id, station_hash, schedule_json, valid_start_time=None):
        if valid_start_time is None:
            valid_start_time = datetime.now()
        
        # Ensure json is string with consistent formatting
        schedule_json_str = None
        if schedule_json is not None:
            if isinstance(schedule_json, (dict, list)):
                schedule_json_str = json.dumps(schedule_json, ensure_ascii=False, sort_keys=True)
            else:
                schedule_json_str = schedule_json

        # 1. Check current record
        select_sql = """
        SELECT schedule_json 
        FROM t_station_price_schedule_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:
            row_json = current_row.schedule_json
            
            # Normalize row_json for comparison
            if row_json:
                try:
                    if isinstance(row_json, str):
                        row_json_obj = json.loads(row_json)
                        row_json = json.dumps(row_json_obj, ensure_ascii=False, sort_keys=True)
                except Exception:
                    pass

            if row_json == schedule_json_str:
                # No change, skip insert
                return

            # Expire old record
            update_sql = """
            UPDATE t_station_price_schedule_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
        sql = """
        INSERT INTO t_station_price_schedule_scd
        (id, station_hash, schedule_json, valid_start_time, is_current)
        VALUES
        (:id, :station_hash, :schedule_json, :valid_start_time, 1)
        """
        await session.execute(text(sql), {
            "id": id,
            "station_hash": station_hash,
            "schedule_json": schedule_json_str,
            "valid_start_time": valid_start_time
        })