"""Read historical station measurements from PostgreSQL."""

import datetime
import os
from typing import Dict, List, Optional

from sqlalchemy import create_engine, text


class PostgresHistory:
    def __init__(self, connection_string: Optional[str] = None, engine=None):
        connection_string = connection_string or os.getenv("POSTGRES_CONNECTION_STRING")
        if engine is None and not connection_string:
            raise RuntimeError("POSTGRES_CONNECTION_STRING is not configured")
        self.engine = engine or create_engine(connection_string, pool_pre_ping=True)

    def station_history(
        self,
        station_code: str,
        start: datetime.datetime,
        end: datetime.datetime,
        limit: int = 2000,
    ) -> List[Dict]:
        if not 1 <= limit <= 10000:
            raise ValueError("limit must be between 1 and 10000")
        if start >= end:
            raise ValueError("start must be before end")

        query = text(
            """
            SELECT m.timestamp, s.station_code, m.water_level,
                   m.discharge, m.discharge_percent
            FROM water_measurements m
            JOIN stations s ON m.station_id = s.id
            WHERE s.station_code = :station_code
              AND m.timestamp >= :start_time
              AND m.timestamp <= :end_time
            ORDER BY m.timestamp ASC
            LIMIT :limit
            """
        )
        with self.engine.connect() as connection:
            rows = connection.execute(
                query,
                {
                    "station_code": station_code,
                    "start_time": start,
                    "end_time": end,
                    "limit": limit,
                },
            )
            result = []
            for row in rows:
                timestamp = row[0]
                if isinstance(timestamp, str):
                    timestamp = datetime.datetime.fromisoformat(timestamp)
                result.append(
                    {
                        "timestamp": timestamp,
                        "station_code": row[1],
                        "water_level": float(row[2]) if row[2] is not None else None,
                        "discharge": float(row[3]) if row[3] is not None else None,
                        "discharge_percent": float(row[4]) if row[4] is not None else None,
                    }
                )
            return result