import os
import io
import sys
import yaml
import string
import hashlib
from collections import defaultdict

from Cryptodome.Cipher import AES
from Cryptodome.Util import Padding
from aiohttp import web


class AttrDict(dict):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.__dict__ = self

    def update(self, *d, **kwargs):
        for key, val in (d[0] if d else kwargs).items():
            setattr(self, key, val)

    def __getattr__(self, item):
        return self.setdefault(item, AttrDict())


def cast_to_ad(d):
    if not isinstance(d, AttrDict):
        d = AttrDict(d)
    for k, v in dict(d.items()).items():
        if " " in k:
            del d[k]
            d[k.replace(" ", "_")] = v
        if isinstance(v, dict):
            d[k] = cast_to_ad(v)
    return d


def sizeof_fmt(num, suffix='B'):
    for unit in ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi']:
        if abs(num) < 1024.0:
            return f"{num:3.1f}{unit}{suffix}"
        num /= 1024.0
    return f"{num:.1f}Yi{suffix}"


async def prepare(_, handler):
    async def prepare_handler(req):
        if 'acc' not in req.match_info:
            return web.Response(text='bad request', status=400)
        return await handler(req, req.match_info["acc"], file_db[req.match_info["acc"]])
    return prepare_handler


async def handle_upload(req, acc, acc_db):
    if conf.auth and req.headers.get('auth') not in conf.auth_tokens:
        return web.Response(text='access denied', status=403)
    reader = await req.multipart()
    file = await reader.next()

    filename = os.path.basename(file.filename)

    if not os.path.isdir(f'{conf.data_path}/{acc}'):
        os.mkdir(f'{conf.data_path}/{acc}')

    for _ in range(100):
        hb = os.urandom(conf.url_hash_len//2)
        h = hb.hex()
        if h not in acc_db:
            break
    else:
        return web.Response(text='server full', status=500)

    acc_db[h] = filename
    local_fname = f'{conf.data_path}/{acc}/{h}_{filename}'
    ext = os.path.splitext(filename)[1] if conf.show_ext else ''
    os.fdopen(os.open(local_fname, os.O_WRONLY | os.O_CREAT, 0o600)).close()
    try:
        valid_file = await recv_file(file, local_fname)
    except IOError:
        return web.Response(text='internal io error', status=500)
    if valid_file:
        c = AES.new(conf.del_crypt_key, AES.MODE_CBC)
        hb = Padding.pad(hb, AES.block_size)
        del_h = (c.encrypt(hb) + c.iv).hex()
        return web.Response(text=f'{conf.protocol}://{acc}{conf.prefix}/{h[:conf.url_hash_len]}{ext}\n'
                                 f'{conf.protocol}://{acc}{conf.prefix}/del/{del_h}')
    os.unlink(local_fname)
    del acc_db[h]
    return web.Response(text=f'file is bigger than {sizeof_fmt(conf.max_filesize)}', status=413)


async def recv_file(file, local_fname):
    size = 0
    with io.BufferedWriter(open(local_fname, 'wb')) as f:
        while True:
            chunk = await file.read_chunk()
            if not chunk:
                return True
            size += len(chunk)
            if size > conf.max_filesize:
                return False
            f.write(chunk)


async def handle_delete(req, acc, acc_db):
    chashiv = req.match_info.get('hash', 'x')
    if not set(chashiv).issubset(valid_hash_chars) or len(chashiv) != 64:
        return web.Response(text='invalid delete link', status=400)
    chashiv = bytes.fromhex(chashiv)

    c = AES.new(conf.del_crypt_key, AES.MODE_CBC, iv=chashiv[AES.block_size:])
    fhash = c.decrypt(chashiv[:AES.block_size])
    try:
        fhash = Padding.unpad(fhash, AES.block_size).hex()
    except ValueError:
        pass
    if fhash not in acc_db or len(fhash) == 32:
        return web.Response(text='this file doesn\'t exist on the server', status=404)
    os.unlink(f"{conf.data_path}/{acc}/{fhash}_{acc_db[fhash]}")
    del acc_db[fhash]
    return web.Response(text='file deleted')


async def handle_download(req, acc, acc_db):
    fhash = req.match_info.get('hash', '').split('.', 1)[0]
    if fhash not in acc_db:
        return web.Response(text='file not found', status=404)
    return web.FileResponse(f"{conf.data_path}/{acc}/{fhash}_{acc_db[fhash]}", headers={
        'CONTENT-DISPOSITION': f'inline;filename="{acc_db[fhash]}"'
    })


def main():
    if not os.path.isdir(conf.data_path):
        os.mkdir(conf.data_path)
    for acc in os.listdir(conf.data_path):
        if not os.path.isdir(f'{conf.data_path}/{acc}'):
            continue
        for file in os.listdir(f"{conf.data_path}/{acc}"):
            if "_" in file:
                fhash, fname = file.split('_', 1)
                file_db[acc][fhash] = fname

    app = web.Application(middlewares=[prepare])
    app.router.add_post(conf.prefix + '/post/{acc}', handle_upload)
    app.router.add_get(conf.prefix + '/del/{hash}/{acc}', handle_delete)
    app.router.add_get(conf.prefix + '/{hash}/{acc}', handle_download)

    web.run_app(app, port=80)


if __name__ == '__main__':
    valid_hash_chars = set(string.hexdigits)
    file_db = defaultdict(dict)
    confname = sys.argv[1] if sys.argv[1:] and os.path.isfile(sys.argv[1]) else 'config.yaml'
    with open(confname) as cf:
        conf = cast_to_ad(yaml.load(cf))
    if conf.url_hash_len > 31:
        raise ValueError('url_hash_len can\'t be bigger than 31')
    if not set(conf.max_filesize.replace(' ', ''))\
            .issubset(valid_hash_chars | {'*'}):
        raise ValueError('max_filsize only can contain numbers and *')
    conf.max_filesize = eval(conf.max_filesize)
    conf.auth_tokens = set(conf.tokens)
    conf.prefix = conf.prefix.strip("/")
    if conf.prefix:
        conf.prefix = f'/{conf.prefix}'
    conf.del_crypt_key = hashlib.md5(conf.del_crypt_key.encode()).digest()[:16]
    main()