from aiofile import async_open
import os
import time
import mimetypes
from os import path

mimetypes.init()
# In production we highly recommend to use CDN like CloudFlare or/and NGINX or similar for static files
async def sendfile(res, req, filename):
    # read headers before the first await
    if_modified_since = req.get_header("if-modified-since")
    range_header = req.get_header("range")
    bytes_range = None
    start = 0
    end = -1
    # parse range header
    if range_header:
        bytes_range = range_header.replace("bytes=", "").split("-")
        start = int(bytes_range[0])
        if bytes_range[1]:
            end = int(bytes_range[1])
    try:
        exists = path.exists(filename)
        # not found
        if not exists:
            return res.write_status(404).end(b"Not Found")

        # get size and last modified date
        stats = os.stat(filename)
        total_size = stats.st_size
        size = total_size
        last_modified = time.strftime(
            "%a, %d %b %Y %H:%M:%S GMT", time.gmtime(stats.st_mtime)
        )

        # check if modified since is provided
        if if_modified_since == last_modified:
            return res.write_status(304).end_without_body()
        # tells the browser the last modified date
        res.write_header(b"Last-Modified", last_modified)

        # add content type
        (content_type, encoding) = mimetypes.guess_type(filename, strict=True)
        if content_type and encoding:
            res.write_header(b"Content-Type", "%s; %s" % (content_type, encoding))
        elif content_type:
            res.write_header(b"Content-Type", content_type)

        async with async_open(filename, "rb") as fd:
            # check range and support it
            if start > 0 or not end == -1:
                if end < 0 or end >= size:
                    end = size - 1
                size = end - start + 1
                fd.seek(start)
                if start > total_size or size > total_size or size < 0 or start < 0:
                    return res.write_status(416).end_without_body()
                res.write_status(206)
            else:
                end = size - 1
                res.write_status(200)

            # tells the browser that we support range
            # TODO: FIX BYTE RANGE IN ASYNC
            # res.write_header(b'Accept-Ranges', b'bytes')
            # res.write_header(b'Content-Range', 'bytes %d-%d/%d' % (start, end, total_size))

            pending_size = size
            # keep sending until abort or done
            while not res.aborted:
                chunk_size = 16384  # 16kb chunks
                if chunk_size > pending_size:
                    chunk_size = pending_size
                buffer = await fd.read(chunk_size)
                pending_size = pending_size - chunk_size
                (ok, done) = await res.send_chunk(buffer, size)
                if not ok or done:  # if cannot send probably aborted
                    break

    except Exception as error:
        res.write_status(500).end("Internal Error")


def in_directory(file, directory):
    # make both absolute
    directory = path.join(path.realpath(directory), "")
    file = path.realpath(file)
    # return true, if the common prefix of both is equal to directory
    # e.g. /a/b/c/d.rst and directory is /a/b, the common prefix is /a/b
    return path.commonprefix([file, directory]) == directory


def static_route(app, route, directory):
    def route_handler(res, req):
        url = req.get_url()
        res.grab_aborted_handler()
        url = url[len(route) : :]
        if url.startswith("/"):
            url = url[1::]
        filename = path.join(path.realpath(directory), url)

        if not in_directory(filename, directory):
            res.write_status(404).end_without_body()
            return
        res.run_async(sendfile(res, req, filename))

    if route.startswith("/"):
        route = route[1::]
    app.get("%s/*" % route, route_handler)