from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy import create_engine
from sqlalchemy.orm import Session, sessionmaker
from sqlalchemy import select

from dotenv import load_dotenv
import os 
load_dotenv()
PADDING = int(os.getenv("FILES_PADDING"))
DATABASE_NAME = os.getenv("DATABASE_NAME")

engine = create_engine(f"sqlite:///{DATABASE_NAME}")
session = Session(bind=engine)

class Base(DeclarativeBase): pass
  
class File(Base):
    __tablename__ = "files"
  
    id = Column(Integer, primary_key=True, index=True)
    extension = Column(String, nullable=True)
    name = Column(String)
    content_type = Column(String)
    size = Column(Integer)
    hash = Column(String)

    def __repr__(self):
        return f"<File(id={self.id}, extension='{self.extension}', hash='{self.hash}')>"

def to_base36(n: int, width: int) -> str:
    if n < 0:
        raise ValueError("Only non-negative integers supported")

    chars = "0123456789abcdefghijklmnopqrstuvwxyz"
    if n == 0:
        return "0".rjust(width, "0")

    result = []
    while n > 0:
        n, rem = divmod(n, 36)
        result.append(chars[rem])
    return "".join(reversed(result)).rjust(width, "0")


def from_base36(s: str) -> int:
    chars = "0123456789abcdefghijklmnopqrstuvwxyz"
    char_to_val = {c: i for i, c in enumerate(chars)}

    s = s.lower().lstrip("0")
    if not s:  
        return 0

    n = 0
    for ch in s:
        if ch not in char_to_val:
            raise ValueError(f"Invalid base36 character: {ch}")
        n = n * 36 + char_to_val[ch]
    return n

Base.metadata.create_all(bind=engine)

def get_all_files():
    with Session(autoflush=False, bind=engine) as db:
        statement = select(File)
        return db.scalars(statement).all()

def file_exists(size: int, hash_value: str) -> bool:
    with Session(bind=engine) as db:
        statement = select(File).where(
            File.size == size,
            File.hash == hash_value
        )
        
        existed_file = db.scalars(statement).first()

        if existed_file is None:
            return None

        url = f"{to_base36(existed_file.id, PADDING)}"
        if existed_file.extension:
            url += f".{existed_file.extension}"

        return url


def add_file(filename: str, content_type, size: int, hash):
    with Session(autoflush=False, bind=engine) as db:
        new_file = File()
        if "." in filename:
            new_file.name, new_file.extension = filename.rsplit(".", 1)
        else:
            new_file.name = filename
            new_file.extension = None
        new_file.content_type = content_type
        new_file.size = size 
        new_file.hash = hash 
        db.add(new_file)
        db.commit()
        url = f"{to_base36(new_file.id, PADDING)}"
        if new_file.extension:
            url += f".{new_file.extension}"

        return url


def remove_file(file_url: str):
    with Session(autoflush=False, bind=engine) as db:
        file_id = from_base36(file_url.rsplit(".")[0])
        file = db.get(File, file_id)
        if not file:
            return None
        db.delete(file)
        db.commit() 
        return True

if __name__ == "__main__":
    for i in get_all_files():
        print(f"{i.id} {i.name}.{i.extension} ({i.hash}) {i.content_type} {i.size}")