from __future__ import annotations

import contextlib
from cachetools import LRUCache
from typing import Mapping

from utils.lib import DotDict

from .connection import conn
from .queries import insert, insert_many, select_where, update_where, upsert, delete_where, update_many


# Global cache of interfaces
tables: Mapping[str, Table] = DotDict()


class Table:
    """
    Transparent interface to a single table structure in the database.
    Contains standard methods to access the table.
    Intended to be subclassed to provide more derivative access for specific tables.
    """
    conn = conn
    queries = DotDict()

    def __init__(self, name, attach_as=None):
        self.name = name
        tables[attach_as or name] = self

    def select_where(self, *args, **kwargs):
        with self.conn:
            return select_where(self.name, *args, **kwargs)

    def select_one_where(self, *args, **kwargs):
        rows = self.select_where(*args, **kwargs)
        return rows[0] if rows else None

    def update_where(self, *args, **kwargs):
        with self.conn:
            return update_where(self.name, *args, **kwargs)

    def delete_where(self, *args, **kwargs):
        with self.conn:
            return delete_where(self.name, *args, **kwargs)

    def insert(self, *args, **kwargs):
        with self.conn:
            return insert(self.name, *args, **kwargs)

    def insert_many(self, *args, **kwargs):
        with self.conn:
            return insert_many(self.name, *args, **kwargs)

    def update_many(self, *args, **kwargs):
        with self.conn:
            return update_many(self.name, *args, **kwargs)

    def upsert(self, *args, **kwargs):
        with self.conn:
            return upsert(self.name, *args, **kwargs)

    def save_query(self, func):
        """
        Decorator to add a saved query to the table.
        """
        self.queries[func.__name__] = func


class Row:
    __slots__ = ('table', 'data', '_pending')

    conn = conn

    def __init__(self, table, data, *args, **kwargs):
        super().__setattr__('table', table)
        self.data = data
        self._pending = None

    @property
    def rowid(self):
        return self.table.id_from_row(self.data)

    def __repr__(self):
        return "Row[{}]({})".format(
            self.table.name,
            ', '.join("{}={!r}".format(field, getattr(self, field)) for field in self.table.columns)
        )

    def __getattr__(self, key):
        if key in self.table.columns:
            if self._pending and key in self._pending:
                return self._pending[key]
            else:
                return self.data[key]
        else:
            raise AttributeError(key)

    def __setattr__(self, key, value):
        if key in self.table.columns:
            if self._pending is None:
                self.update(**{key: value})
            else:
                self._pending[key] = value
        else:
            super().__setattr__(key, value)

    @contextlib.contextmanager
    def batch_update(self):
        if self._pending:
            raise ValueError("Nested batch updates for {}!".format(self.__class__.__name__))

        self._pending = {}
        try:
            yield self._pending
        finally:
            if self._pending:
                self.update(**self._pending)
            self._pending = None

    def _refresh(self):
        row = self.table.select_one_where(self.table.dict_from_id(self.rowid))
        if not row:
            raise ValueError("Refreshing a {} which no longer exists!".format(type(self).__name__))
        self.data = row

    def update(self, **values):
        rows = self.table.update_where(values, **self.table.dict_from_id(self.rowid))
        self.data = rows[0]

    @classmethod
    def _select_where(cls, _extra=None, **conditions):
        return select_where(cls._table, **conditions)

    @classmethod
    def _insert(cls, **values):
        return insert(cls._table, **values)

    @classmethod
    def _update_where(cls, values, **conditions):
        return update_where(cls._table, values, **conditions)


class RowTable(Table):
    __slots__ = (
        'name',
        'columns',
        'id_col',
        'multi_key',
        'row_cache'
    )

    conn = conn

    def __init__(self, name, columns, id_col, use_cache=True, cache=None, cache_size=1000, **kwargs):
        super().__init__(name, **kwargs)
        self.name = name
        self.columns = columns
        self.id_col = id_col
        self.multi_key = isinstance(id_col, tuple)
        self.row_cache = (cache or LRUCache(cache_size)) if use_cache else None

    def id_from_row(self, row):
        if self.multi_key:
            return tuple(row[key] for key in self.id_col)
        else:
            return row[self.id_col]

    def dict_from_id(self, rowid):
        if self.multi_key:
            return dict(zip(self.id_col, rowid))
        else:
            return {self.id_col: rowid}

    # Extend original Table update methods to modify the cached rows
    def insert(self, *args, **kwargs):
        data = super().insert(*args, **kwargs)
        if self.row_cache is not None:
            self.row_cache[self.id_from_row(data)] = Row(self, data)
        return data

    def insert_many(self, *args, **kwargs):
        data = super().insert_many(*args, **kwargs)
        if self.row_cache is not None:
            for data_row in data:
                cached_row = self.row_cache.get(self.id_from_row(data_row), None)
                if cached_row is not None:
                    cached_row.data = data_row
        return data

    def update_where(self, *args, **kwargs):
        data = super().update_where(*args, **kwargs)
        if self.row_cache is not None:
            for data_row in data:
                cached_row = self.row_cache.get(self.id_from_row(data_row), None)
                if cached_row is not None:
                    cached_row.data = data_row
        return data

    def update_many(self, *args, **kwargs):
        data = super().update_many(*args, **kwargs)
        if self.row_cache is not None:
            for data_row in data:
                cached_row = self.row_cache.get(self.id_from_row(data_row), None)
                if cached_row is not None:
                    cached_row.data = data_row
        return data

    def delete_where(self, *args, **kwargs):
        data = super().delete_where(*args, **kwargs)
        if self.row_cache is not None:
            for data_row in data:
                self.row_cache.pop(self.id_from_row(data_row), None)
        return data

    def upsert(self, *args, **kwargs):
        data = super().upsert(*args, **kwargs)
        if self.row_cache is not None:
            rowid = self.id_from_row(data)
            cached_row = self.row_cache.get(rowid, None)
            if cached_row is not None:
                cached_row.data = data
            else:
                self.row_cache[rowid] = Row(self, data)
        return data

    # New methods to fetch and create rows
    def _make_rows(self, *data_rows):
        """
        Create or retrieve Row objects for each provided data row.
        If the rows already exist in cache, updates the cached row.
        """
        if self.row_cache is not None:
            rows = []
            for data_row in data_rows:
                rowid = self.id_from_row(data_row)

                cached_row = self.row_cache.get(rowid, None)
                if cached_row is not None:
                    cached_row.data = data_row
                    row = cached_row
                else:
                    row = Row(self, data_row)
                    self.row_cache[rowid] = row
                rows.append(row)
        else:
            rows = [Row(self, data_row) for data_row in data_rows]
        return rows

    def create_row(self, *args, **kwargs):
        data = self.insert(*args, **kwargs)
        return self._make_rows(data)[0]

    def fetch_rows_where(self, *args, **kwargs):
        # TODO: Handle list of rowids here?
        data = self.select_where(*args, **kwargs)
        return self._make_rows(*data)

    def fetch(self, rowid):
        """
        Fetch the row with the given id, retrieving from cache where possible.
        """
        row = self.row_cache.get(rowid, None) if self.row_cache is not None else None
        if row is None:
            rows = self.fetch_rows_where(**self.dict_from_id(rowid))
            row = rows[0] if rows else None
        return row

    def fetch_or_create(self, rowid=None, **kwargs):
        """
        Helper method to fetch a row with the given id or fields, or create it if it doesn't exist.
        """
        if rowid is not None:
            row = self.fetch(rowid)
        else:
            data = self.select_where(**kwargs)
            row = self._make_rows(data[0])[0] if data else None

        if row is None:
            creation_kwargs = kwargs
            if rowid is not None:
                creation_kwargs.update(self.dict_from_id(rowid))
            row = self.create_row(**creation_kwargs)
        return row