import sqlite3
import threading
from typing import cast
from pathlib import Path
from dataclasses import dataclass
from typing import Callable, ParamSpec, TypeVar, Generic

import dt
import utils
import config
from logger import LOGGER


T = TypeVar('T')
P = ParamSpec('P')
R = TypeVar('R')


@dataclass(frozen=True)
class ResponseBody(Generic[T]):
    """The generic response body for API return."""

    success: bool
    """True if this operation is successful, otherwise false."""
    error: str
    """The error message provided when operation failed."""
    data: T | None
    """The payload provided when operation successed."""


class DbException(Exception):
    """Error occurs when manipulating with database."""
    pass


def SafeDatabaseOperation(inner: Callable[P, R]) -> Callable[P, ResponseBody[R]]:
    def wrapper(*args, **kwargs) -> ResponseBody[R]:
        # extract self from args
        self: 'CalendarDatabase' = args[0]
        # get config
        cfg = config.get_config()

        with self.mutex:
            # try to fetching database and allocate database cursor
            try:
                db = self._get_db()
                self._allocate_cursor()
            except Exception as e:
                self._free_cursor()
                if cfg.others.debug:
                    LOGGER.exception(e)
                return ResponseBody(False, str(e), None)

            # do real data work
            try:
                currentTime = utils.GetCurrentTimestamp()
                if currentTime - self.latestClean > cfg.others.auto_token_clean_duration:
                    self.latestClean = currentTime
                    LOGGER.info('Cleaning outdated token...')
                    self.tokenOper_clean()

                result = ResponseBody(True, '', inner(*args, **kwargs))
                self._free_cursor()
                db.commit()
                return result
            except Exception as e:
                self._free_cursor()
                db.rollback()
                if cfg.others.debug:
                    LOGGER.exception(e)
                return ResponseBody(False, str(e), None)

    return wrapper

class CalendarDatabase:

    db: sqlite3.Connection | None
    cursor: sqlite3.Cursor | None
    mutex: threading.Lock
    latestClean: int

    def __init__(self):
        self.db = None
        self.cursor = None
        self.mutex = threading.Lock()
        self.latestClean = 0

    def open(self):
        if (self.db is not None):
            raise DbException('Database is already opened')

        cfg = config.get_config()
        match cfg.database.driver:
            case config.DatabaseDriver.SQLITE:
                self.db = sqlite3.connect(cast(config.SqliteDatabaseConfig, cfg.database.config).path, check_same_thread = False)
                self.db.execute('PRAGMA encoding = "UTF-8";')
                self.db.execute('PRAGMA foreign_keys = ON;')
            case config.DatabaseDriver.MYSQL:
                raise DbException('Not implemented database')
            case _:
                raise DbException('Unknow database type')

    def init(self, username: str, password: str):
        if (self.db is not None):
            raise DbException('Database is already opened')

        # establish tables
        cfg = config.get_config()
        backend_path = Path(__file__).resolve().parent
        backend_sql_path = backend_path / 'sql'
        match cfg.database.driver:
            case config.DatabaseDriver.SQLITE:
                sql_file = backend_sql_path / 'sqlite.sql'
            case config.DatabaseDriver.MYSQL:
                raise DbException('Not implemented database')
            case _:
                raise DbException('Unknow database type')

        self.open()
        db = self._get_db()

        self._allocate_cursor()
        cursor = self._get_cursor()

        # execute script for creating tables
        with open(sql_file, 'r', encoding='utf-8') as fsql:
            cursor.executescript(fsql.read())
        # add default user in user table
        cursor.execute('INSERT INTO user VALUES (?, ?, ?, ?);', (
            username,
            utils.ComputePasswordHash(password),
            1,
            utils.GenerateSalt()
        ))

        self._free_cursor()

        # commit to database
        db.commit()

    def close(self):
        if (self.db is None):
            LOGGER.warning('Try to close null database.')
        else:
            self._free_cursor()
            self.db.close()
            self.db = None

    def _get_db(self) -> sqlite3.Connection:
        if (self.db is None):
            raise DbException('There is no opened database')
        else:
            return self.db

    def _allocate_cursor(self) -> None:
        if (self.cursor is not None):
            raise DbException('There is already opened database cursor')
        else:
            self.cursor = self._get_db().cursor()

    def _get_cursor(self) -> sqlite3.Cursor:
        if (self.cursor is None):
            raise DbException('There is no opened database cursor')
        else:
            return self.cursor

    def _free_cursor(self) -> None:
        if (self.cursor is None):
            LOGGER.warning('Try to free null databse cursor.')
        else:
            self.cursor.close()
            self.cursor = None

    # ======================= token related internal operation
    def tokenOper_clean(self):
        # remove outdated token
        cursor = self._get_cursor()
        cursor.execute('DELETE FROM token WHERE [token_expire_on] <= ?',(utils.GetCurrentTimestamp(), ))

    def tokenOper_postpone_expireOn(self, token):
        cursor = self._get_cursor()
        cursor.execute('UPDATE token SET [token_expire_on] = ? WHERE [token] = ?;', (
            utils.GetTokenExpireOn(),
            token
        ))

    def tokenOper_check_valid(self, token):
        self.tokenOper_get_username(token)

    def tokenOper_is_admin(self, username):
        cursor = self._get_cursor()
        cursor.execute('SELECT [is_admin] FROM user WHERE [name] = ?;',(username, ))
        cache = cursor.fetchone()[0]
        return cache == 1

    def tokenOper_get_username(self, token):
        cursor = self._get_cursor()
        cursor.execute('SELECT [user] FROM token WHERE [token] = ? AND [token_expire_on] > ?;',(
            token,
            utils.GetCurrentTimestamp()
        ))
        result = cursor.fetchone()[0]
        # need postpone expire on time
        self.tokenOper_postpone_expireOn(token)
        return result
        
    # =============================== # =============================== operation function
    # =============================== common
    
    @SafeDatabaseOperation
    def common_salt(self, username):
        cursor = self._get_cursor()
        salt = utils.GenerateSalt()
        cursor.execute('UPDATE user SET [salt] = ? WHERE [name] = ?;', (
            salt,
            username
        ))
        return salt

    @SafeDatabaseOperation
    def common_login(self, username, password, clientUa, clientIp):
        cursor = self._get_cursor()
        cursor.execute('SELECT [password], [salt] FROM user WHERE [name] = ?;', (username, ))
        (gotten_salt, gotten_password) = cursor.fetchone()
        
        if password == utils.ComputePasswordHashWithSalt(gotten_password, gotten_salt):
            token = utils.GenerateToken(username)
            cursor.execute('UPDATE user SET [salt] = ? WHERE [name] = ?;', (
                utils.GenerateSalt(), # regenerate a new slat to prevent re-login try
                username
            ))
            cursor.execute('INSERT INTO token VALUES (?, ?, ?, ?, ?);', (
                username,
                token,
                utils.GetTokenExpireOn(), # add 2 day from now
                clientUa,
                clientIp,
            ))
            return token
        else:
            # throw a exception to indicate fail to login
            raise DbException('Login authentication failed')

    @SafeDatabaseOperation
    def common_webLogin(self, username, password, clientUa, clientIp):
        cursor = self._get_cursor()
        LOGGER.debug(f'WebLogin Username: {username}')
        LOGGER.debug(f'WebLogin Password: {password}')
        passwordHash = utils.ComputePasswordHash(password)
        LOGGER.debug(f'WebLogin Password Hash: {passwordHash}')

        cursor.execute('SELECT [name] FROM user WHERE [name] = ? AND [password] = ?;', (username, passwordHash))

        if len(cursor.fetchall()) != 0:
            token = utils.GenerateToken(username)
            cursor.execute('INSERT INTO token VALUES (?, ?, ?, ?, ?);', (
                username,
                token,
                utils.GetTokenExpireOn(), # add 2 day from now
                clientUa,
                clientIp,
            ))
            return token
        else:
            # throw a exception to indicate fail to login
            raise DbException('Login authentication failed')

    @SafeDatabaseOperation
    def common_logout(self, token):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)
        cursor.execute('DELETE FROM token WHERE [token] = ?;', (token, ))
        return True

    @SafeDatabaseOperation
    def common_tokenValid(self, token):
        self.tokenOper_check_valid(token)
        return True

    # =============================== calendar
    @SafeDatabaseOperation
    def calendar_getFull(self, token, startDateTime, endDateTime):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT calendar.* FROM calendar INNER JOIN collection \
                ON collection.uuid = calendar.belong_to \
                WHERE (collection.user = ? AND calendar.loop_date_time_end >= ? AND calendar.loop_date_time_start - (calendar.event_date_time_end - calendar.event_date_time_start) <= ?);', 
                (username, startDateTime, endDateTime))
        return cursor.fetchall()

    @SafeDatabaseOperation
    def calendar_getList(self, token, startDateTime, endDateTime):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT calendar.uuid FROM calendar INNER JOIN collection \
                ON collection.uuid = calendar.belong_to \
                WHERE (collection.user = ? AND calendar.loop_date_time_end >= ? AND calendar.loop_date_time_start - (calendar.event_date_time_end - calendar.event_date_time_start) <= ?);', 
                (username, startDateTime, endDateTime))
        return tuple(map(lambda x: x[0], cursor.fetchall()))

    @SafeDatabaseOperation
    def calendar_getDetail(self, token, uuid):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)
        cursor.execute('SELECT * FROM calendar WHERE [uuid] = ?;', (uuid, ))
        return cursor.fetchone()

    @SafeDatabaseOperation
    def calendar_update(self, token, uuid, lastChange, **optArgs):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        # get prev data
        cursor.execute('SELECT * FROM calendar WHERE [uuid] = ? AND [last_change] = ?;', (uuid, lastChange))
        analyseData = list(cursor.fetchone())

        # construct update data
        lastupdate = utils.GenerateUUID()
        sqlList = [
            '[last_change] = ?',
        ]
        argumentsList = [
            lastupdate,
        ]

        # analyse opt arg
        reAnalyseLoop = False

        cache = optArgs.get('belongTo', None)
        if cache is not None:
            sqlList.append('[belong_to] = ?')
            argumentsList.append(cache)
        cache = optArgs.get('title', None)
        if cache is not None:
            sqlList.append('[title] = ?')
            argumentsList.append(cache)
        cache = optArgs.get('description', None)
        if cache is not None:
            sqlList.append('[description] = ?')
            argumentsList.append(cache)
        cache = optArgs.get('eventDateTimeStart', None)
        if cache is not None:
            sqlList.append('[event_date_time_start] = ?')
            argumentsList.append(cache)
            reAnalyseLoop = True
            analyseData[5] = cache
        cache = optArgs.get('eventDateTimeEnd', None)
        if cache is not None:
            sqlList.append('[event_date_time_end] = ?')
            argumentsList.append(cache)
        cache = optArgs.get('loopRules', None)
        if cache is not None:
            sqlList.append('[loop_rules] = ?')
            argumentsList.append(cache)
            reAnalyseLoop = True
            analyseData[8] = cache
        cache = optArgs.get('timezoneOffset', None)
        if cache is not None:
            sqlList.append('[timezone_offset] = ?')
            argumentsList.append(cache)
            reAnalyseLoop = True
            analyseData[7] = cache

        if reAnalyseLoop:
            # re-compute loop data and upload it into list
            sqlList.append('[loop_date_time_start] = ?')
            argumentsList.append(analyseData[5])
            sqlList.append('[loop_date_time_end] = ?')
            argumentsList.append(str(dt.ResolveLoopStr(
                analyseData[8],
                analyseData[5],
                analyseData[7]
            )))

        # execute
        argumentsList.append(uuid)
        cursor.execute('UPDATE calendar SET {} WHERE [uuid] = ?;'.format(', '.join(sqlList)), 
        tuple(argumentsList))
        if cursor.rowcount != 1:
            raise DbException('Fail to update due to no matched rows or too much rows.')
        return lastupdate

    @SafeDatabaseOperation
    def calendar_add(self, token, belongTo, title, description, eventDateTimeStart, eventDateTimeEnd, loopRules, timezoneOffset):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        newuuid = utils.GenerateUUID()
        lastupdate = utils.GenerateUUID()

        # analyse loopRules and output following 2 fileds.
        loopDateTimeStart = eventDateTimeStart
        loopDateTimeEnd = dt.ResolveLoopStr(loopRules, eventDateTimeStart, timezoneOffset)

        cursor.execute('INSERT INTO calendar VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);', 
        (newuuid,
        belongTo,
        title,
        description,
        lastupdate,
        eventDateTimeStart,
        eventDateTimeEnd,
        timezoneOffset,
        loopRules,
        loopDateTimeStart,
        loopDateTimeEnd))
        return newuuid

    @SafeDatabaseOperation
    def calendar_delete(self, token, uuid, lastChange):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)
        cursor.execute('DELETE FROM calendar WHERE [uuid] = ? AND [last_change] = ?;', (uuid, lastChange))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')
        return True

    # =============================== collection
    @SafeDatabaseOperation
    def collection_getFullOwn(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT [uuid], [name], [last_change] FROM collection WHERE [user] = ?;', (username, ))
        return cursor.fetchall()

    @SafeDatabaseOperation
    def collection_getListOwn(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT [uuid] FROM collection WHERE [user] = ?;', (username, ))
        return tuple(map(lambda x: x[0], cursor.fetchall()))

    @SafeDatabaseOperation
    def collection_getDetailOwn(self, token, uuid):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT [uuid], [name], [last_change] FROM collection WHERE [user] = ? AND [uuid] = ?;', (username, uuid))
        return cursor.fetchone()

    @SafeDatabaseOperation
    def collection_addOwn(self, token, newname):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        newuuid = utils.GenerateUUID()
        lastupdate = utils.GenerateUUID()
        cursor.execute('INSERT INTO collection VALUES (?, ?, ?, ?);',
        (newuuid, newname, username, lastupdate))
        return newuuid

    @SafeDatabaseOperation
    def collection_updateOwn(self, token, uuid, newname, lastChange):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        lastupdate = utils.GenerateUUID()
        cursor.execute('UPDATE collection SET [name] = ?, [last_change] = ? WHERE [uuid] = ? AND [last_change] = ?;', (
            newname,
            lastupdate,
            uuid,
            lastChange
        ))
        if cursor.rowcount != 1:
            raise DbException('Fail to update due to no matched rows or too much rows.')
        return lastupdate

    @SafeDatabaseOperation
    def collection_deleteOwn(self, token, uuid, lastChange):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        cursor.execute('DELETE FROM collection WHERE [uuid] = ? AND [last_change] = ?;', (
            uuid,
            lastChange
        ))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')
        return True

    @SafeDatabaseOperation
    def collection_getSharing(self, token, uuid):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)
        cursor.execute('SELECT [target] FROM share WHERE [uuid] = ?;', (uuid, ))
        return tuple(map(lambda x: x[0], cursor.fetchall()))

    @SafeDatabaseOperation
    def collection_deleteSharing(self, token, uuid, target, lastChange):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        lastupdate = utils.GenerateUUID()
        cursor.execute('UPDATE collection SET [last_change] = ?, WHERE [uuid] = ? AND [last_change] = ?;', (lastupdate, uuid, lastChange))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')

        cursor.execute('DELETE FROM share WHERE [uuid] = ? AND [target] = ?;', (uuid, target))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')

        return lastupdate

    @SafeDatabaseOperation
    def collection_addSharing(self, token, uuid, target, lastChange):
        cursor = self._get_cursor()
        self.tokenOper_check_valid(token)

        lastupdate = utils.GenerateUUID()
        cursor.execute('UPDATE collection SET [last_change] = ? WHERE [uuid] = ? AND [last_change] = ?;', (lastupdate, uuid, lastChange))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')

        cursor.execute('SELECT * FROM share WHERE [uuid] = ? AND [target] = ?;', (uuid, target))
        if len(cursor.fetchall()) != 0:
            raise DbException('Fail to insert duplicated item.')
        cursor.execute('INSERT INTO share VALUES (?, ?);', (uuid, target))

        return lastupdate

    @SafeDatabaseOperation
    def collection_getShared(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT collection.uuid, collection.name, collection.user \
                FROM share INNER JOIN collection \
                ON share.uuid = collection.uuid \
                WHERE share.target = ?;', (username, ))
        return cursor.fetchall()

    # =============================== todo
    @SafeDatabaseOperation
    def todo_getFull(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT * FROM todo WHERE [belong_to] = ?;', (username, ))
        return cursor.fetchall()

    @SafeDatabaseOperation
    def todo_getList(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT [uuid] FROM todo WHERE [belong_to] = ?;', (username, ))
        return tuple(map(lambda x: x[0], cursor.fetchall()))

    @SafeDatabaseOperation
    def todo_getDetail(self, token, uuid):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('SELECT * FROM todo WHERE [belong_to] = ? AND [uuid] = ?;', (username, uuid))
        return cursor.fetchone()

    @SafeDatabaseOperation
    def todo_add(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        newuuid = utils.GenerateUUID()
        lastupdate = utils.GenerateUUID()
        returnedData = (
            newuuid,
            username,
            '',
            lastupdate,
        )
        cursor.execute('INSERT INTO todo VALUES (?, ?, ?, ?);', returnedData)
        return returnedData

    @SafeDatabaseOperation
    def todo_update(self, token, uuid, data, lastChange):
        cursor = self._get_cursor()
        # check valid token
        self.tokenOper_check_valid(token)

        # update
        newLastChange = utils.GenerateUUID()
        cursor.execute('UPDATE todo SET [data] = ?, [last_change] = ? WHERE [uuid] = ? AND [last_change] = ?;', (
            data,
            newLastChange,
            uuid,
            lastChange
        ))
        if cursor.rowcount != 1:
            raise DbException('Fail to update due to no matched rows or too much rows.')
        return newLastChange

    @SafeDatabaseOperation
    def todo_delete(self, token, uuid, lastChange):
        cursor = self._get_cursor()
        # check valid token
        self.tokenOper_check_valid(token)

        # delete
        cursor.execute('DELETE FROM todo WHERE [uuid] = ? AND [last_change] = ?;', (uuid, lastChange))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')
        return True


    # =============================== admin
    @SafeDatabaseOperation
    def admin_get(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        if not self.tokenOper_is_admin(username):
            raise DbException('Permission denied.')

        cursor.execute('SELECT [name], [is_admin] FROM user;')
        return tuple(map(lambda x: (x[0], x[1] == 1), cursor.fetchall()))

    @SafeDatabaseOperation
    def admin_add(self, token, newname):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        if not self.tokenOper_is_admin(username):
            raise DbException('Permission denied.')

        newpassword = utils.ComputePasswordHash(utils.GenerateUUID())
        cursor.execute('INSERT INTO user VALUES (?, ?, ?, ?);', (
            newname,
            newpassword,
            0,
            utils.GenerateSalt()
        ))
        return (newname, False)

    @SafeDatabaseOperation
    def admin_update(self, token, _username, **optArgs):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        if not self.tokenOper_is_admin(username):
            raise DbException('Permission denied.')

        # construct data
        sqlList = []
        argumentsList = []

        # analyse opt arg
        cache = optArgs.get('password', None)
        if cache is not None:
            sqlList.append('[password] = ?')
            argumentsList.append(utils.ComputePasswordHash(cache))
        cache = optArgs.get('isAdmin', None)
        if cache is not None:
            sqlList.append('[is_admin] = ?')
            argumentsList.append(1 if cache else 0)

        # execute
        argumentsList.append(_username)
        cursor.execute('UPDATE user SET {} WHERE [name] = ?;'.format(', '.join(sqlList)), 
        tuple(argumentsList))
        LOGGER.debug(cache)
        LOGGER.debug(tuple(argumentsList))
        if cursor.rowcount != 1:
            raise DbException('Fail to update due to no matched rows or too much rows.')
        return True

    @SafeDatabaseOperation
    def admin_delete(self, token, username):
        cursor = self._get_cursor()
        _username = self.tokenOper_get_username(token)
        if not self.tokenOper_is_admin(_username):
            raise DbException('Permission denied.')

        # delete
        cursor.execute('DELETE FROM user WHERE [name] = ?;', (username, ))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')
        return True

    # =============================== profile
    @SafeDatabaseOperation
    def profile_isAdmin(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        return self.tokenOper_is_admin(username)

    @SafeDatabaseOperation
    def profile_changePassword(self, token, newpassword):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)
        cursor.execute('UPDATE user SET [password] = ? WHERE [name] = ?;', (
            utils.ComputePasswordHash(newpassword),
            username
        ))
        return True

    @SafeDatabaseOperation
    def profile_getToken(self, token):
        cursor = self._get_cursor()
        username = self.tokenOper_get_username(token)

        cursor.execute('SELECT * FROM token WHERE [user] = ?;', (
            username,
        ))
        return cursor.fetchall()

    @SafeDatabaseOperation
    def profile_deleteToken(self, token, deleteToken):
        cursor = self._get_cursor()
        _username = self.tokenOper_get_username(token)

        # delete
        cursor.execute('DELETE FROM token WHERE [user] = ? AND [token] = ?;', (
            _username, 
            deleteToken
        ))
        if cursor.rowcount != 1:
            raise DbException('Fail to delete due to no matched rows or too much rows.')
        return True