import getpass
import json
import logging
import typing
import uuid

import aiopg
from aiopg.sa.engine import APGCompiler_psycopg2
from sqlalchemy.dialects.postgresql.psycopg2 import PGDialect_psycopg2
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 DatabaseURL
from databases.interfaces import ConnectionBackend, DatabaseBackend, TransactionBackend

logger = logging.getLogger("databases")


class AiopgBackend(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 = self._get_dialect()
        self._pool = None

    def _get_dialect(self) -> Dialect:
        dialect = PGDialect_psycopg2(
            json_serializer=json.dumps, json_deserializer=lambda x: x
        )
        dialect.statement_compiler = APGCompiler_psycopg2
        dialect.implicit_returning = True
        dialect.supports_native_enum = True
        dialect.supports_smallserial = True  # 9.2+
        dialect._backslash_escapes = False
        dialect.supports_sane_multi_rowcount = True  # psycopg 2.0.9+
        dialect._has_native_hstore = True
        dialect.supports_native_decimal = True

        return dialect

    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")
        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 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 aiopg.create_pool(
            host=self._database_url.hostname,
            port=self._database_url.port,
            user=self._database_url.username or getpass.getuser(),
            password=self._database_url.password,
            database=self._database_url.database,
            **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) -> "AiopgConnection":
        return AiopgConnection(self, self._dialect)


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


class AiopgConnection(ConnectionBackend):
    def __init__(self, database: AiopgBackend, dialect: Dialect):
        self._database = database
        self._dialect = dialect
        self._connection = None  # type: typing.Optional[aiopg.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)
        cursor = await self._connection.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:
            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)
        cursor = await self._connection.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:
            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)
        cursor = await self._connection.cursor()
        try:
            await cursor.execute(query_str, args)
            return cursor.lastrowid
        finally:
            cursor.close()

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

    def transaction(self) -> TransactionBackend:
        return AiopgTransaction(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 = {}

        logger.debug("Query: %s\nArgs: %s", compiled.string, args)
        return compiled.string, args, CompilationContext(execution_context)

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


class AiopgTransaction(TransactionBackend):
    def __init__(self, connection: AiopgConnection):
        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
        cursor = await self._connection._connection.cursor()
        if self._is_root:
            await cursor.execute("BEGIN")
        else:
            id = str(uuid.uuid4()).replace("-", "_")
            self._savepoint_name = f"STARLETTE_SAVEPOINT_{id}"
            try:
                await cursor.execute(f"SAVEPOINT {self._savepoint_name}")
            finally:
                cursor.close()

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

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