# SPDX-License-Identifier: GPL-2.0-only
#
# This file is part of Nominatim. (https://nominatim.org)
#
# Copyright (C) 2023 by the Nominatim developer community.
# For a full list of authors see the git log.
"""
Implementation of classes for API access via libraries.
"""
from typing import Mapping, Optional, Any, AsyncIterator
import asyncio
import contextlib
from pathlib import Path

import sqlalchemy as sa
import sqlalchemy.ext.asyncio as sa_asyncio
import asyncpg

from nominatim.config import Configuration
from nominatim.api.status import get_status, StatusResult

class NominatimAPIAsync:
    """ API loader asynchornous version.
    """
    def __init__(self, project_dir: Path,
                 environ: Optional[Mapping[str, str]] = None) -> None:
        self.config = Configuration(project_dir, environ)
        self.server_version = 0

        self._engine_lock = asyncio.Lock()
        self._engine: Optional[sa_asyncio.AsyncEngine] = None


    async def setup_database(self) -> None:
        """ Set up the engine and connection parameters.

            This function will be implicitly called when the database is
            accessed for the first time. You may also call it explicitly to
            avoid that the first call is delayed by the setup.
        """
        async with self._engine_lock:
            if self._engine:
                return

            dsn = self.config.get_database_params()

            dburl = sa.engine.URL.create(
                       'postgresql+asyncpg',
                       database=dsn.get('dbname'),
                       username=dsn.get('user'), password=dsn.get('password'),
                       host=dsn.get('host'), port=int(dsn['port']) if 'port' in dsn else None,
                       query={k: v for k, v in dsn.items()
                              if k not in ('user', 'password', 'dbname', 'host', 'port')})
            engine = sa_asyncio.create_async_engine(
                             dburl, future=True,
                             connect_args={'server_settings': {
                                'DateStyle': 'sql,european',
                                'max_parallel_workers_per_gather': '0'
                             }})

            try:
                async with engine.begin() as conn:
                    result = await conn.scalar(sa.text('SHOW server_version_num'))
                    self.server_version = int(result)
            except asyncpg.PostgresError:
                self.server_version = 0

            if self.server_version >= 110000:
                @sa.event.listens_for(engine.sync_engine, "connect") # type: ignore[misc]
                def _on_connect(dbapi_con: Any, _: Any) -> None:
                    cursor = dbapi_con.cursor()
                    cursor.execute("SET jit_above_cost TO '-1'")
                # Make sure that all connections get the new settings
                await self.close()

            self._engine = engine


    async def close(self) -> None:
        """ Close all active connections to the database. The NominatimAPIAsync
            object remains usable after closing. If a new API functions is
            called, new connections are created.
        """
        if self._engine is not None:
            await self._engine.dispose()


    @contextlib.asynccontextmanager
    async def begin(self) -> AsyncIterator[sa_asyncio.AsyncConnection]:
        """ Create a new connection with automatic transaction handling.

            This function may be used to get low-level access to the database.
            Refer to the documentation of SQLAlchemy for details how to use
            the connection object.
        """
        if self._engine is None:
            await self.setup_database()

        assert self._engine is not None

        async with self._engine.begin() as conn:
            yield conn


    async def status(self) -> StatusResult:
        """ Return the status of the database.
        """
        try:
            async with self.begin() as conn:
                status = await get_status(conn)
        except asyncpg.PostgresError:
            return StatusResult(700, 'Database connection failed')

        return status


class NominatimAPI:
    """ API loader, synchronous version.
    """

    def __init__(self, project_dir: Path,
                 environ: Optional[Mapping[str, str]] = None) -> None:
        self._loop = asyncio.new_event_loop()
        self._async_api = NominatimAPIAsync(project_dir, environ)


    def close(self) -> None:
        """ Close all active connections to the database. The NominatimAPIAsync
            object remains usable after closing. If a new API functions is
            called, new connections are created.
        """
        self._loop.run_until_complete(self._async_api.close())
        self._loop.close()


    def status(self) -> StatusResult:
        """ Return the status of the database.
        """
        return self._loop.run_until_complete(self._async_api.status())