"""
This module contains interfaces for storage classes
"""

import os
import abc
import array
import shutil
import sqlite3
from typing import Any, TypeVar, Type, IO, Tuple, cast, List, Dict, Iterable

import yaml
try:
    from yaml import CLoader as Loader, CDumper as Dumper  # type: ignore
except ImportError:
    from yaml import Loader, Dumper  # type: ignore


from .result_classes import Storable, IStorable


class ISimpleStorage(metaclass=abc.ABCMeta):
    """interface for low-level storage, which doesn't support serialization
    and can operate only on bytes"""

    @abc.abstractmethod
    def put(self, value: bytes, path: str) -> None:
        pass

    @abc.abstractmethod
    def get(self, path: str) -> bytes:
        pass

    @abc.abstractmethod
    def rm(self, path: str) -> None:
        pass

    @abc.abstractmethod
    def sync(self) -> None:
        pass

    @abc.abstractmethod
    def __contains__(self, path: str) -> bool:
        pass

    @abc.abstractmethod
    def get_fd(self, path: str, mode: str = "rb+") -> IO:
        pass

    @abc.abstractmethod
    def sub_storage(self, path: str) -> 'ISimpleStorage':
        pass


class ISerializer(metaclass=abc.ABCMeta):
    """Interface for serialization class"""
    @abc.abstractmethod
    def pack(self, value: Storable) -> bytes:
        pass

    @abc.abstractmethod
    def unpack(self, data: bytes) -> Any:
        pass


class DBStorage(ISimpleStorage):

    create_tb_sql = "CREATE TABLE IF NOT EXISTS wally_storage (key text, data blob, type text)"
    insert_sql = "INSERT INTO wally_storage VALUES (?, ?, ?)"
    update_sql = "UPDATE wally_storage SET data=?, type=? WHERE key=?"
    select_sql = "SELECT data, type FROM wally_storage WHERE key=?"
    contains_sql = "SELECT 1 FROM wally_storage WHERE key=?"
    rm_sql = "DELETE FROM wally_storage WHERE key LIKE '{}%'"
    list2_sql = "SELECT key, length(data), type FROM wally_storage"

    def __init__(self, db_path: str = None, existing: bool = False,
                 prefix: str = None, db: sqlite3.Connection = None) -> None:

        assert not prefix or "'" not in prefix, "Broken sql prefix {!r}".format(prefix)

        if db_path:
            self.existing = existing
            if existing:
                if not os.path.isfile(db_path):
                    raise IOError("No storage found at {!r}".format(db_path))

            os.makedirs(os.path.dirname(db_path), exist_ok=True)
            try:
                self.db = sqlite3.connect(db_path)
            except sqlite3.OperationalError as exc:
                raise IOError("Can't open database at {!r}".format(db_path)) from exc

            self.db.execute(self.create_tb_sql)
        else:
            if db is None:
                raise ValueError("Either db or db_path parameter must be passed")
            self.db = db

        if prefix is None:
            self.prefix = ""
        elif not prefix.endswith('/'):
            self.prefix = prefix + '/'
        else:
            self.prefix = prefix

    def put(self, value: bytes, path: str) -> None:
        c = self.db.cursor()
        fpath = self.prefix + path
        c.execute(self.contains_sql, (fpath,))
        if len(c.fetchall()) == 0:
            c.execute(self.insert_sql, (fpath, value, 'yaml'))
        else:
            c.execute(self.update_sql, (value, 'yaml', fpath))

    def get(self, path: str) -> bytes:
        c = self.db.cursor()
        c.execute(self.select_sql, (self.prefix + path,))
        res = cast(List[Tuple[bytes, str]], c.fetchall())  # type: List[Tuple[bytes, str]]
        if not res:
            raise KeyError(path)
        assert len(res) == 1
        val, tp = res[0]
        assert tp == 'yaml'
        return val

    def rm(self, path: str) -> None:
        c = self.db.cursor()
        path = self.prefix + path
        assert "'" not in path, "Broken sql path {!r}".format(path)
        c.execute(self.rm_sql.format(path))

    def __contains__(self, path: str) -> bool:
        c = self.db.cursor()
        path = self.prefix + path
        c.execute(self.contains_sql, (self.prefix + path,))
        return len(c.fetchall()) != 0

    def print_tree(self):
        c = self.db.cursor()
        c.execute(self.list2_sql)
        data = list(c.fetchall())
        data.sort()
        print("------------------ DB ---------------------")
        for key, data_ln, type in data:
            print(key, data_ln, type)
        print("------------------ END --------------------")

    def get_fd(self, path: str, mode: str = "rb+") -> IO[bytes]:
        raise NotImplementedError("SQLITE3 doesn't provide fd-like interface")

    def sub_storage(self, path: str) -> 'DBStorage':
        return self.__class__(prefix=self.prefix + path, db=self.db)

    def sync(self):
        self.db.commit()


DB_REL_PATH = "__db__.db"


class FSStorage(ISimpleStorage):
    """Store all data in files on FS"""

    def __init__(self, root_path: str, existing: bool) -> None:
        self.root_path = root_path
        self.existing = existing

    def j(self, path: str) -> str:
        return os.path.join(self.root_path, path)

    def put(self, value: bytes, path: str) -> None:
        jpath = self.j(path)
        os.makedirs(os.path.dirname(jpath), exist_ok=True)
        with open(jpath, "wb") as fd:
            fd.write(value)

    def get(self, path: str) -> bytes:
        try:
            with open(self.j(path), "rb") as fd:
                return fd.read()
        except FileNotFoundError as exc:
            raise KeyError(path) from exc

    def rm(self, path: str) -> None:
        if os.path.isdir(path):
            shutil.rmtree(path, ignore_errors=True)
        elif os.path.exists(path):
            os.unlink(path)

    def __contains__(self, path: str) -> bool:
        return os.path.exists(self.j(path))

    def get_fd(self, path: str, mode: str = "rb+") -> IO[bytes]:
        jpath = self.j(path)

        if "cb" == mode:
            create_on_fail = True
            mode = "rb+"
        else:
            create_on_fail = False

        os.makedirs(os.path.dirname(jpath), exist_ok=True)

        try:
            fd = open(jpath, mode)
        except IOError:
            if not create_on_fail:
                raise
            fd = open(jpath, "wb")

        return cast(IO[bytes], fd)

    def sub_storage(self, path: str) -> 'FSStorage':
        return self.__class__(self.j(path), self.existing)

    def sync(self):
        pass


class YAMLSerializer(ISerializer):
    """Serialize data to yaml"""
    def pack(self, value: Storable) -> bytes:
        try:
            return yaml.dump(value, Dumper=Dumper, encoding="utf8")
        except Exception as exc:
            raise ValueError("Can't pickle object {!r} to yaml".format(type(value))) from exc

    def unpack(self, data: bytes) -> Any:
        return yaml.load(data, Loader=Loader)


class SAFEYAMLSerializer(ISerializer):
    """Serialize data to yaml"""
    def pack(self, value: Storable) -> bytes:
        try:
            return yaml.safe_dump(value, encoding="utf8")
        except Exception as exc:
            raise ValueError("Can't pickle object {!r} to yaml".format(type(value))) from exc

    def unpack(self, data: bytes) -> Any:
        return yaml.safe_load(data)


ObjClass = TypeVar('ObjClass', bound=IStorable)


class Storage:
    """interface for storage"""
    def __init__(self, fs_storage: ISimpleStorage, db_storage: ISimpleStorage, serializer: ISerializer) -> None:
        self.fs = fs_storage
        self.db = db_storage
        self.serializer = serializer

    def sub_storage(self, *path: str) -> 'Storage':
        fpath = "/".join(path)
        return self.__class__(self.fs.sub_storage(fpath), self.db.sub_storage(fpath), self.serializer)

    def put(self, value: Storable, *path: str) -> None:
        dct_value = value.raw() if isinstance(value, IStorable) else value
        serialized = self.serializer.pack(dct_value)
        fpath = "/".join(path)
        self.db.put(serialized, fpath)
        self.fs.put(serialized, fpath)

    def put_list(self, value: Iterable[IStorable], *path: str) -> None:
        serialized = self.serializer.pack([obj.raw() for obj in value])
        fpath = "/".join(path)
        self.db.put(serialized, fpath)
        self.fs.put(serialized, fpath)

    def get(self, *path: str) -> Any:
        return self.serializer.unpack(self.db.get("/".join(path)))

    def rm(self, *path: str) -> None:
        fpath = "/".join(path)
        self.fs.rm(fpath)
        self.db.rm(fpath)

    def __contains__(self, path: str) -> bool:
        return path in self.fs or path in self.db

    def put_raw(self, val: bytes, *path: str) -> None:
        self.fs.put(val, "/".join(path))

    def get_raw(self, *path: str) -> bytes:
        return self.fs.get("/".join(path))

    def get_fd(self, path: str, mode: str = "r") -> IO:
        return self.fs.get_fd(path, mode)

    def put_array(self, value: array.array, *path: str) -> None:
        with self.get_fd("/".join(path), "wb") as fd:
            value.tofile(fd)  # type: ignore

    def get_array(self, typecode: str, *path: str) -> array.array:
        res = array.array(typecode)
        path_s = "/".join(path)
        with self.get_fd(path_s, "rb") as fd:
            fd.seek(0, os.SEEK_END)
            size = fd.tell()
            fd.seek(0, os.SEEK_SET)
            assert size % res.itemsize == 0, "Storage object at path {} contains no array of {} or corrupted."\
                .format(path_s, typecode)
            res.fromfile(fd, size // res.itemsize)  # type: ignore
        return res

    def append(self, value: array.array, *path: str) -> None:
        with self.get_fd("/".join(path), "cb") as fd:
            fd.seek(0, os.SEEK_END)
            value.tofile(fd)  # type: ignore

    def load_list(self, obj_class: Type[ObjClass], *path: str) -> List[ObjClass]:
        path_s = "/".join(path)
        raw_val = cast(List[Dict[str, Any]], self.get(path_s))
        assert isinstance(raw_val, list)
        return [obj_class.fromraw(val) for val in raw_val]

    def load(self, obj_class: Type[ObjClass], *path: str) -> ObjClass:
        path_s = "/".join(path)
        return obj_class.fromraw(self.get(path_s))

    def sync(self) -> None:
        self.db.sync()
        self.fs.sync()

    def __enter__(self) -> 'Storage':
        return self

    def __exit__(self, x: Any, y: Any, z: Any) -> None:
        self.sync()


def make_storage(url: str, existing: bool = False) -> Storage:
    return Storage(FSStorage(url, existing),
                   DBStorage(os.path.join(url, DB_REL_PATH)),
                   SAFEYAMLSerializer())