nameko http entrypoint router

import inspect

from nameko.extensions import ENTRYPOINT_EXTENSIONS_ATTR
from nameko.web.handlers import HttpRequestHandler
from werkzeug.routing import Map, Rule


class ResolveUrlError(Exception):
    pass


class Router:
    def __init__(self, service_cls, host=None):
        self.service_cls = service_cls
        self.host = host

        routes = self.get_routes()
        self.map = self.url_map(routes)

    def get_routes(self):
        routes = []

        for method_name, method in inspect.getmembers(self.service_cls, inspect.isfunction):
            entrypoints = getattr(method, ENTRYPOINT_EXTENSIONS_ATTR, [])
            entrypoint_routes = [
                (entrypoint.url, method_name, entrypoint.method.split(',')) for entrypoint in entrypoints
                if isinstance(entrypoint, HttpRequestHandler)
            ]
            routes.extend(entrypoint_routes)
        return routes

    def url_map(self, routes):
        rules = [Rule(path, endpoint=endpoint, methods=methods) for path, endpoint, methods in routes]
        return Map(rules)

    def resolve(self, endpoint, host: str = None, **values):
        host = self.host or host

        if host.startswith('http'):
            scheme, host = host.split('://')
        else:
            scheme = 'http'

        adapter = self.map.bind(server_name=host, url_scheme=scheme)

        try:
            return adapter.build(endpoint, values=values, force_external=True)
        except Exception as e:
            raise ResolveUrlError(f'Can not resolve url: {endpoint}') from e
            
            
# Dependency example

class RouterDependency(DependencyProvider):
    def get_dependency(self, worker_ctx):
        config = self.container.config.copy()
        return http.Router(self.container.service_cls, host=config['HOST'])
        
        
# Usage example

class Service:
    name = 'service'    
    router = RouterDependency()

    @http('GET', '/a/b/<c>')
    def meth(self, request):
        pass
        
    def another_method(self):
        url = self.router.resolve('meth', c=123)
        url = self.router.resolve('meth', host='http://example.com', c=123)  # Override host