import sqlite3
from threading import Lock
from typing import Generic, TypeVar, Union, get_args
from pydantic import BaseModel, parse_raw_as
from .item_storage import ItemStorageABC, PaginatedResults

T = TypeVar('T', bound=BaseModel)

sqlite_memory = ':memory:'

class SqliteItemStorage(ItemStorageABC, Generic[T]):
    _filename: str
    _table_name: str
    _conn: sqlite3.Connection
    _cursor: sqlite3.Cursor
    _id_field: str
    _lock: Lock

    def __init__(self, filename: str, table_name: str, id_field: str = 'id'):
        super().__init__()

        self._filename = filename
        self._table_name = table_name
        self._id_field = id_field # TODO: validate that T has this field
        self._lock = Lock()

        self._conn = sqlite3.connect(self._filename, check_same_thread=False) # TODO: figure out a better threading solution
        self._cursor = self._conn.cursor()

        self._create_table()

    def _create_table(self):
        try:
            self._lock.acquire()
            self._cursor.execute(f'''CREATE TABLE IF NOT EXISTS {self._table_name} (
                item TEXT,
                id TEXT GENERATED ALWAYS AS (json_extract(item, '$.{self._id_field}')) VIRTUAL NOT NULL);''')
            self._cursor.execute(f'''CREATE UNIQUE INDEX IF NOT EXISTS {self._table_name}_id ON {self._table_name}(id);''')
        finally:
            self._lock.release()

    def _parse_item(self, item: str) -> T:
        item_type = get_args(self.__orig_class__)[0]
        return parse_raw_as(item_type, item)

    def set(self, item: T):
        try:
            self._lock.acquire()
            self._cursor.execute(f'''INSERT OR REPLACE INTO {self._table_name} (item) VALUES (?);''', (item.json(),))
        finally:
            self._lock.release()
        self._on_changed(item)

    def get(self, id: str) -> Union[T, None]:
        try:
            self._lock.acquire()
            self._cursor.execute(f'''SELECT item FROM {self._table_name} WHERE id = ?;''', (str(id),))
            result = self._cursor.fetchone()
        finally:
            self._lock.release()

        if not result:
            return None

        return self._parse_item(result[0])

    def delete(self, id: str):
        try:
            self._lock.acquire()
            self._cursor.execute(f'''DELETE FROM {self._table_name} WHERE id = ?;''', (str(id),))
        finally:
            self._lock.release()
        self._on_deleted(id)

    def list(self, page: int = 0, per_page: int = 10) -> PaginatedResults[T]:
        try:
            self._lock.acquire()
            self._cursor.execute(f'''SELECT item FROM {self._table_name} LIMIT ? OFFSET ?;''', (per_page, page * per_page))
            result = self._cursor.fetchall()

            items = list(map(lambda r: self._parse_item(r[0]), result))

            self._cursor.execute(f'''SELECT count(*) FROM {self._table_name};''')
            count = self._cursor.fetchone()[0]
        finally:
            self._lock.release()

        pageCount = int(count / per_page) + 1

        return PaginatedResults[T](
            items = items,
            page = page,
            pages = pageCount,
            per_page = per_page,
            total = count
        )
    
    def search(self, query: str, page: int = 0, per_page: int = 10) -> PaginatedResults[T]:
        try:
            self._lock.acquire()
            self._cursor.execute(f'''SELECT item FROM {self._table_name} WHERE item LIKE ? LIMIT ? OFFSET ?;''', (f'%{query}%', per_page, page * per_page))
            result = self._cursor.fetchall()

            items = list(map(lambda r: self._parse_item(r[0]), result))

            self._cursor.execute(f'''SELECT count(*) FROM {self._table_name} WHERE item LIKE ?;''', (f'%{query}%',))
            count = self._cursor.fetchone()[0]
        finally:
            self._lock.release()

        pageCount = int(count / per_page) + 1

        return PaginatedResults[T](
            items = items,
            page = page,
            pages = pageCount,
            per_page = per_page,
            total = count
        )