socketify.py/src/socketify/helpers.py

import os
import time
import mimetypes
import inspect
from os import path

mimetypes.init()

# We have an version of this using aiofile and aiofiles
# This is an sync version without any dependencies is normally much faster in CPython and PyPy3
# In production we highly recomend 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 broswer 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)
        
        with 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 
            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 = 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)



def middleware(*functions):
    #we use Optional data=None at the end so you can use and middleware inside a middleware
    async def middleware_route(res, req, data=None):
        some_async_as_run = False
        #cicle to all middlewares
        for function in functions:
            #detect if is coroutine or not
            if inspect.iscoroutinefunction(function):
                #in async query string, arguments and headers are only valid until the first await
                if not some_async_as_run:
                     #get_headers will preserve headers (and cookies) inside req, after await
                    headers = req.get_headers() 
                    #get_parameters will preserve all params inside req after await 
                    params = req.get_parameters()
                    #get queries will preserve all queries inside req after await 
                    queries = req.get_queries()
                    #mark to only grab header, params and queries one time
                    some_async_as_run = True 
                data = await function(res, req, data)
            else:
                #call middlewares
                data = function(res, req, data)
            #stops if returns Falsy
            if not data:
                break

    return middleware_route


class MiddlewareRouter():
    def __init__(self, app, *middlewares):
        self.app = app
        self.middlewares = middlewares

    def get(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.get(path, middleware(*middies))
        return self

    def post(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.post(path, middleware(*middies))
        return self
    def options(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.options(path, middleware(*middies))
        return self
    def delete(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.delete(path, middleware(*middies))
        return self
    def patch(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.patch(path, middleware(*middies))
        return self
    def put(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.put(path, middleware(*middies))
        return self
    def head(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.head(path, middleware(*middies))
        return self
    def connect(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.connect(path, middleware(*middies))
        return self
    def trace(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.trace(path, middleware(*middies))
        return self
    def any(self, path, handler):
        middies = list(self.middlewares)
        middies.append(handler)
        self.app.any(path, middleware(*middies))
        return self