import getpass
import logging
import typing
import uuid

import asyncmy
from sqlalchemy.dialects.mysql import pymysql
from sqlalchemy.engine.cursor import CursorResultMetaData
from sqlalchemy.engine.interfaces import Dialect, ExecutionContext
from sqlalchemy.engine.row import Row
from sqlalchemy.sql import ClauseElement
from sqlalchemy.sql.ddl import DDLElement

from databases.core import LOG_EXTRA, DatabaseURL
from databases.interfaces import ConnectionBackend, DatabaseBackend, TransactionBackend

logger = logging.getLogger("databases")


class AsyncMyBackend(DatabaseBackend):
    def __init__(
        self, database_url: typing.Union[DatabaseURL, str], **options: typing.Any
    ) -> None:
        self._database_url = DatabaseURL(database_url)
        self._options = options
        self._dialect = pymysql.dialect(paramstyle="pyformat")
        self._dialect.supports_native_decimal = True
        self._pool = None

    def _get_connection_kwargs(self) -> dict:
        url_options = self._database_url.options

        kwargs = {}
        min_size = url_options.get("min_size")
        max_size = url_options.get("max_size")
        pool_recycle = url_options.get("pool_recycle")
        ssl = url_options.get("ssl")

        if min_size is not None:
            kwargs["minsize"] = int(min_size)
        if max_size is not None:
            kwargs["maxsize"] = int(max_size)
        if pool_recycle is not None:
            kwargs["pool_recycle"] = int(pool_recycle)
        if ssl is not None:
            kwargs["ssl"] = {"true": True, "false": False}[ssl.lower()]

        for key, value in self._options.items():
            # Coerce 'min_size' and 'max_size' for consistency.
            if key == "min_size":
                key = "minsize"
            elif key == "max_size":
                key = "maxsize"
            kwargs[key] = value

        return kwargs

    async def connect(self) -> None:
        assert self._pool is None, "DatabaseBackend is already running"
        kwargs = self._get_connection_kwargs()
        self._pool = await asyncmy.create_pool(
            host=self._database_url.hostname,
            port=self._database_url.port or 3306,
            user=self._database_url.username or getpass.getuser(),
            password=self._database_url.password,
            db=self._database_url.database,
            autocommit=True,
            **kwargs,
        )

    async def disconnect(self) -> None:
        assert self._pool is not None, "DatabaseBackend is not running"
        self._pool.close()
        await self._pool.wait_closed()
        self._pool = None

    def connection(self) -> "AsyncMyConnection":
        return AsyncMyConnection(self, self._dialect)


class CompilationContext:
    def __init__(self, context: ExecutionContext):
        self.context = context


class AsyncMyConnection(ConnectionBackend):
    def __init__(self, database: AsyncMyBackend, dialect: Dialect):
        self._database = database
        self._dialect = dialect
        self._connection = None  # type: typing.Optional[asyncmy.Connection]

    async def acquire(self) -> None:
        assert self._connection is None, "Connection is already acquired"
        assert self._database._pool is not None, "DatabaseBackend is not running"
        self._connection = await self._database._pool.acquire()

    async def release(self) -> None:
        assert self._connection is not None, "Connection is not acquired"
        assert self._database._pool is not None, "DatabaseBackend is not running"
        await self._database._pool.release(self._connection)
        self._connection = None

    async def fetch_all(self, query: ClauseElement) -> typing.List[typing.Sequence]:
        assert self._connection is not None, "Connection is not acquired"
        query_str, args, context = self._compile(query)
        async with self._connection.cursor() as cursor:
            try:
                await cursor.execute(query_str, args)
                rows = await cursor.fetchall()
                metadata = CursorResultMetaData(context, cursor.description)
                return [
                    Row(
                        metadata,
                        metadata._processors,
                        metadata._keymap,
                        Row._default_key_style,
                        row,
                    )
                    for row in rows
                ]
            finally:
                await cursor.close()

    async def fetch_one(self, query: ClauseElement) -> typing.Optional[typing.Sequence]:
        assert self._connection is not None, "Connection is not acquired"
        query_str, args, context = self._compile(query)
        async with self._connection.cursor() as cursor:
            try:
                await cursor.execute(query_str, args)
                row = await cursor.fetchone()
                if row is None:
                    return None
                metadata = CursorResultMetaData(context, cursor.description)
                return Row(
                    metadata,
                    metadata._processors,
                    metadata._keymap,
                    Row._default_key_style,
                    row,
                )
            finally:
                await cursor.close()

    async def execute(self, query: ClauseElement) -> typing.Any:
        assert self._connection is not None, "Connection is not acquired"
        query_str, args, context = self._compile(query)
        async with self._connection.cursor() as cursor:
            try:
                await cursor.execute(query_str, args)
                if cursor.lastrowid == 0:
                    return cursor.rowcount
                return cursor.lastrowid
            finally:
                await cursor.close()

    async def execute_many(self, queries: typing.List[ClauseElement]) -> None:
        assert self._connection is not None, "Connection is not acquired"
        async with self._connection.cursor() as cursor:
            try:
                for single_query in queries:
                    single_query, args, context = self._compile(single_query)
                    await cursor.execute(single_query, args)
            finally:
                await cursor.close()

    async def iterate(
        self, query: ClauseElement
    ) -> typing.AsyncGenerator[typing.Any, None]:
        assert self._connection is not None, "Connection is not acquired"
        query_str, args, context = self._compile(query)
        async with self._connection.cursor() as cursor:
            try:
                await cursor.execute(query_str, args)
                metadata = CursorResultMetaData(context, cursor.description)
                async for row in cursor:
                    yield Row(
                        metadata,
                        metadata._processors,
                        metadata._keymap,
                        Row._default_key_style,
                        row,
                    )
            finally:
                await cursor.close()

    def transaction(self) -> TransactionBackend:
        return AsyncMyTransaction(self)

    def _compile(
        self, query: ClauseElement
    ) -> typing.Tuple[str, dict, CompilationContext]:
        compiled = query.compile(
            dialect=self._dialect, compile_kwargs={"render_postcompile": True}
        )

        execution_context = self._dialect.execution_ctx_cls()
        execution_context.dialect = self._dialect

        if not isinstance(query, DDLElement):
            args = compiled.construct_params()
            for key, val in args.items():
                if key in compiled._bind_processors:
                    args[key] = compiled._bind_processors[key](val)

            execution_context.result_column_struct = (
                compiled._result_columns,
                compiled._ordered_columns,
                compiled._textual_ordered_columns,
                compiled._loose_column_name_matching,
            )
        else:
            args = {}

        query_message = compiled.string.replace(" \n", " ").replace("\n", " ")
        logger.debug("Query: %s Args: %s", query_message, repr(args), extra=LOG_EXTRA)
        return compiled.string, args, CompilationContext(execution_context)

    @property
    def raw_connection(self) -> asyncmy.connection.Connection:
        assert self._connection is not None, "Connection is not acquired"
        return self._connection


class AsyncMyTransaction(TransactionBackend):
    def __init__(self, connection: AsyncMyConnection):
        self._connection = connection
        self._is_root = False
        self._savepoint_name = ""

    async def start(
        self, is_root: bool, extra_options: typing.Dict[typing.Any, typing.Any]
    ) -> None:
        assert self._connection._connection is not None, "Connection is not acquired"
        self._is_root = is_root
        if self._is_root:
            await self._connection._connection.begin()
        else:
            id = str(uuid.uuid4()).replace("-", "_")
            self._savepoint_name = f"STARLETTE_SAVEPOINT_{id}"
            async with self._connection._connection.cursor() as cursor:
                try:
                    await cursor.execute(f"SAVEPOINT {self._savepoint_name}")
                finally:
                    await cursor.close()

    async def commit(self) -> None:
        assert self._connection._connection is not None, "Connection is not acquired"
        if self._is_root:
            await self._connection._connection.commit()
        else:
            async with self._connection._connection.cursor() as cursor:
                try:
                    await cursor.execute(f"RELEASE SAVEPOINT {self._savepoint_name}")
                finally:
                    await cursor.close()

    async def rollback(self) -> None:
        assert self._connection._connection is not None, "Connection is not acquired"
        if self._is_root:
            await self._connection._connection.rollback()
        else:
            async with self._connection._connection.cursor() as cursor:
                try:
                    await cursor.execute(
                        f"ROLLBACK TO SAVEPOINT {self._savepoint_name}"
                    )
                finally:
                    await cursor.close()
