import os
import sys
import threading
from dataclasses import dataclass
from datetime import datetime, timedelta
from typing import Optional
from uuid import uuid4, UUID

import bcrypt
import psycopg

from app.fallback import MockConnection


@dataclass
class Letter:
    id: int
    title: str
    contents: str


@dataclass
class User:
    id: int
    email: str
    tier: int

    def in_free_tier(self) -> bool:
        return self.tier == 1


@dataclass
class UserWithHash:
    user: User
    password_hash: str


host = os.environ.get('UNDERCOVER_POSTGRES_HOST')
db_name = os.environ.get('UNDERCOVER_POSTGRES_DBNAME')
port = os.environ.get('UNDERCOVER_POSTGRES_PORT')
db_user = os.environ.get('UNDERCOVER_POSTGRES_USER')

db_available = host and db_name and port and db_user and os.environ.get('UNDERCOVER_POSTGRES_PASSWORD')

if db_available:
    def connect() -> psycopg.Connection:
        return psycopg.connect(
            host=host,
            dbname=db_name,
            port=port,
            user=db_user,
            password=os.environ.get('UNDERCOVER_POSTGRES_PASSWORD'))
else:
    sys.stderr.write('Database login not configured: DB access is disabled.\n')
    sys.stderr.write('  To enable, ensure UNDERCOVER_POSTGRES_{HOST,DBNAME,PORT,USER,PASSWORD} are set.\n')

    def connect() -> object:
        return MockConnection()


def login(user_email: str, password: str) -> bool:
    pw_bytes: bytes = password.encode('utf-8')
    user = __get_user_with_hash(user_email)
    if user:
        return bcrypt.checkpw(pw_bytes, user.password_hash.encode('utf-8'))
    return False


def __gen_pw_hash(password: str) -> str:
    pw_bytes = password.encode('utf-8')
    salt = bcrypt.gensalt()
    pw_hash = bcrypt.hashpw(pw_bytes, salt)
    return pw_hash.decode('utf-8')


def add_user(username: str, password: str) -> None:
    pw_hash = __gen_pw_hash(password)
    with connect() as con:
        cur = con.cursor()
        cur.execute("INSERT INTO users(email, password) VALUES (%s, %s)", (username, pw_hash))
        con.commit()


def delete_user(username: str) -> None:
    with connect() as con:
        cur = con.cursor()
        cur.execute("DELETE FROM users WHERE email = %s", (username,))
        con.commit()


def add_letter(user_id: int, letter_title: str, letter_content: str) -> None:
    with connect() as con:
        cur = con.cursor()
        cur.execute("INSERT INTO letter_data(user_id, letter_name, letter_data) VALUES (%s, %s, %s)",
                    (user_id, letter_title, letter_content))
        con.commit()


def edit_letter(letter_id: int, letter_title: str, letter_content: str) -> None:
    with connect() as con:
        cur = con.cursor()
        cur.execute("UPDATE letter_data SET letter_name = %s, letter_data = %s WHERE id = %s",
                    (letter_title, letter_content, letter_id))
        con.commit()


def get_user_letters(user_id: int) -> list[Letter]:
    with connect() as con:
        cur = con.cursor()
        cur.execute("SELECT id, letter_name, letter_data FROM letter_data WHERE user_id = %s", (str(user_id),))
        return list(map(lambda row: Letter(row[0], row[1], row[2]), cur.fetchall()))


def get_user(email: str) -> Optional[User]:
    user_with_hash = __get_user_with_hash(email)
    if user_with_hash:
        return user_with_hash.user
    return None


def __get_user_with_hash(email: str) -> Optional[UserWithHash]:
    """
    :param email:
    :return: User without their password_hash
    """
    with connect() as con:
        cur = con.cursor()
        cur.execute("SELECT id, password, tier FROM users WHERE users.email ILIKE %s", (email,))
        row = cur.fetchone()
        if row:
            user_id, password, tier = row
            return UserWithHash(User(user_id, email, tier), password)
        return None


RESET_TIME = timedelta(minutes=-1 * 15)


def initiate_password_reset(email: str) -> Optional[UUID]:
    user = get_user(email)
    if not user:
        return None
    reset_id = uuid4()
    with connect() as con:
        cur = con.cursor()
        cur.execute(
            "INSERT INTO resets(user_id, id, reset_time) VALUES (%s, %s, NOW())",
            (user.id, reset_id)
        )
        threading.Timer(RESET_TIME.total_seconds(), delete_reset_row, [reset_id]).start()
        con.commit()
        return reset_id


def delete_reset_row(reset_id: UUID) -> None:
    with connect() as con:
        cur = con.cursor()
        cur.execute("DELETE FROM resets WHERE id = %s", (reset_id,))
        con.commit()


def complete_reset(reset_id: str, new_password: str) -> bool:
    with connect() as con:
        cur = con.cursor()
        cur.execute("SELECT reset_time, user_id FROM resets WHERE id = %s", (reset_id,))
        row = cur.fetchone()
        if not row or not row[0]:
            return False
        reset_time, user_id = row
        if reset_time > (datetime.utcnow() + RESET_TIME):
            cur.execute("DELETE FROM resets WHERE id = %s", (reset_id,))
            password_hash = __gen_pw_hash(new_password)
            cur.execute("UPDATE users SET password = %s WHERE id = %s", (password_hash, user_id))
            con.commit()
            return True
        return False