#!/usr/bin/env python3

import os
import time
import mimetypes
import random
import json
import re
from slugify import slugify
from wolkje_files import file_name as fn


class UnknownMimeTypeError(Exception):
	pass
class NoSuchFolderError(Exception):
	pass
class NoSuchFileError(Exception):
	pass
class IllegalFileNameError(Exception):
	pass


_SECRETS_CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
_FOLDER_ID_LENGTH = 22
_PASSWORD_LENGTH = 32

FOLDER_ID_PATTERN = re.compile(r"^[A-Za-z0-9]{%d}$" % _FOLDER_ID_LENGTH)

def generate_secret(length):
	return "".join(
		_SECRETS_CHARACTERS[random.randint(0, len(_SECRETS_CHARACTERS) - 1)]
		for _ in range(length)
	)

def generate_new_folder_id():
	folder_id = generate_secret(_FOLDER_ID_LENGTH)
	while os.path.exists(_get_folder_path(folder_id)):
		folder_id = generate_secret(_FOLDER_ID_LENGTH)
	return folder_id

def generate_password():
	return generate_secret(_PASSWORD_LENGTH)


_BASE_STORAGE_DIR_ENVNAME = "WOLKJE_STORAGE_DIR"
_BASE_STORAGE_DIR = os.getenv(_BASE_STORAGE_DIR_ENVNAME)
if not _BASE_STORAGE_DIR:
	raise Exception(f"{_BASE_STORAGE_DIR_ENVNAME} not configured")
if not os.path.isdir(_BASE_STORAGE_DIR):
	raise Exception(f"{_BASE_STORAGE_DIR_ENVNAME} ({_BASE_STORAGE_DIR}) is not an existing directory")
_STORAGE_DIR = os.path.join(_BASE_STORAGE_DIR, "files")
os.makedirs(_STORAGE_DIR, exist_ok=True)

_INFO_FILE_NAME = ".folder.json"

_DATA_FILE_ENCODING = "utf-8"


def _get_folder_path(folder_id):
	return os.path.join(_STORAGE_DIR, folder_id)


def get_folder(folder_id):
	if not FOLDER_ID_PATTERN.fullmatch(folder_id):
		return None
	folder_path = _get_folder_path(folder_id)
	if not os.path.exists(folder_path):
		return None
	folder_info_path = os.path.join(folder_path, _INFO_FILE_NAME)
	if not os.path.exists(folder_info_path):
		return None

	with open(folder_info_path, "r", encoding=_DATA_FILE_ENCODING) as fh:
		data = {
			**json.load(fh),
			"folder_id": folder_id,
			"folder_path": folder_path,
			"folder_info_path": folder_info_path,
		}

	return data


def new_folder(folder_name):
	folder_id = generate_new_folder_id()

	folder_path = _get_folder_path(folder_id)
	folder_info_path = os.path.join(folder_path, _INFO_FILE_NAME)
	os.makedirs(folder_path)
	with open(folder_info_path, "x", encoding=_DATA_FILE_ENCODING) as fh:
		json.dump({
			"name": folder_name,
			"created": int(time.time()),
			"editing_password": generate_password(),
		}, fh, ensure_ascii=False)
	return get_folder(folder_id)


def ls(folder_id):
	folder = get_folder(folder_id)
	if not folder:
		return None
	return [
		filename
		for filename in os.listdir(folder["folder_path"])
		if not filename.startswith(".")
	]


_CHUNK_SIZE_BYTES = 4096
def save_file(folder_id, desired_file_name, file_stream, mime_type):
	folder = get_folder(folder_id)
	if not folder:
		raise NoSuchFolderError()

	ext = mimetypes.guess_extension(mime_type)
	if ext is None:
		raise UnknownMimeTypeError()

	file_name = fn.sanitize(fn.set_extension(desired_file_name, ext))
	if file_name is None:
		raise IllegalFileNameError()
	file_path = os.path.join(_get_folder_path(folder_id), file_name)

	with open(file_path, "wb") as fp:
		while True:
			chunk = file_stream.read(_CHUNK_SIZE_BYTES)
			if not chunk:
				break

			fp.write(chunk)

	return file_name


def open_file(folder_id, file_name):
	folder = get_folder(folder_id)
	if not folder:
		raise NoSuchFolderError()

	file_name = fn.sanitize(file_name)
	if file_name is None:
		raise IllegalFileNameError()
	file_path = os.path.join(_get_folder_path(folder_id), file_name)

	mime_type = mimetypes.guess_type(file_name)

	fp = open(file_path, "rb")
	content_length = os.path.getsize(file_path)

	return fp, content_length, mime_type