"""A simple URL shortener using Werkzeug and redis."""
import os
from urllib.parse import urlsplit

import redis
from jinja2 import Environment
from jinja2 import FileSystemLoader
from werkzeug.exceptions import HTTPException
from werkzeug.exceptions import NotFound
from werkzeug.middleware.shared_data import SharedDataMiddleware
from werkzeug.routing import Map
from werkzeug.routing import Rule
from werkzeug.utils import redirect
from werkzeug.wrappers import Request
from werkzeug.wrappers import Response


def base36_encode(number):
    assert number >= 0, "positive integer required"
    if number == 0:
        return "0"
    base36 = []
    while number != 0:
        number, i = divmod(number, 36)
        base36.append("0123456789abcdefghijklmnopqrstuvwxyz"[i])
    return "".join(reversed(base36))


def is_valid_url(url):
    parts = urlsplit(url)
    return parts.scheme in ("http", "https")


def get_hostname(url):
    return urlsplit(url).netloc


class Shortly:
    def __init__(self, config):
        self.redis = redis.Redis(
            config["redis_host"], config["redis_port"], decode_responses=True
        )
        template_path = os.path.join(os.path.dirname(__file__), "templates")
        self.jinja_env = Environment(
            loader=FileSystemLoader(template_path), autoescape=True
        )
        self.jinja_env.filters["hostname"] = get_hostname

        self.url_map = Map(
            [
                Rule("/", endpoint="new_url"),
                Rule("/<short_id>", endpoint="follow_short_link"),
                Rule("/<short_id>+", endpoint="short_link_details"),
            ]
        )

    def on_new_url(self, request):
        error = None
        url = ""
        if request.method == "POST":
            url = request.form["url"]
            if not is_valid_url(url):
                error = "Please enter a valid URL"
            else:
                short_id = self.insert_url(url)
                return redirect(f"/{short_id}+")
        return self.render_template("new_url.html", error=error, url=url)

    def on_follow_short_link(self, request, short_id):
        link_target = self.redis.get(f"url-target:{short_id}")
        if link_target is None:
            raise NotFound()
        self.redis.incr(f"click-count:{short_id}")
        return redirect(link_target)

    def on_short_link_details(self, request, short_id):
        link_target = self.redis.get(f"url-target:{short_id}")
        if link_target is None:
            raise NotFound()
        click_count = int(self.redis.get(f"click-count:{short_id}") or 0)
        return self.render_template(
            "short_link_details.html",
            link_target=link_target,
            short_id=short_id,
            click_count=click_count,
        )

    def error_404(self):
        response = self.render_template("404.html")
        response.status_code = 404
        return response

    def insert_url(self, url):
        short_id = self.redis.get(f"reverse-url:{url}")
        if short_id is not None:
            return short_id
        url_num = self.redis.incr("last-url-id")
        short_id = base36_encode(url_num)
        self.redis.set(f"url-target:{short_id}", url)
        self.redis.set(f"reverse-url:{url}", short_id)
        return short_id

    def render_template(self, template_name, **context):
        t = self.jinja_env.get_template(template_name)
        return Response(t.render(context), mimetype="text/html")

    def dispatch_request(self, request):
        adapter = self.url_map.bind_to_environ(request.environ)
        try:
            endpoint, values = adapter.match()
            return getattr(self, f"on_{endpoint}")(request, **values)
        except NotFound:
            return self.error_404()
        except HTTPException as e:
            return e

    def wsgi_app(self, environ, start_response):
        request = Request(environ)
        response = self.dispatch_request(request)
        return response(environ, start_response)

    def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)


def create_app(redis_host="localhost", redis_port=6379, with_static=True):
    app = Shortly({"redis_host": redis_host, "redis_port": redis_port})
    if with_static:
        app.wsgi_app = SharedDataMiddleware(
            app.wsgi_app, {"/static": os.path.join(os.path.dirname(__file__), "static")}
        )
    return app


if __name__ == "__main__":
    from werkzeug.serving import run_simple

    app = create_app()
    run_simple("127.0.0.1", 5000, app, use_debugger=True, use_reloader=True)