"""A simple number and datetime addition JSON API.
Demonstrates different strategies for parsing arguments
with the FalconParser.

Run the app:

    $ pip install gunicorn
    $ gunicorn examples.falcon_example:app

Try the following with httpie (a cURL-like utility, http://httpie.org):

    $ pip install httpie
    $ http GET :8000/
    $ http GET :8000/ name==Ada
    $ http POST :8000/add x=40 y=2
    $ http POST :8000/dateadd value=1973-04-10 addend=63
    $ http POST :8000/dateadd value=2014-10-23 addend=525600 unit=minutes
"""
import datetime as dt

from webargs.core import json

import falcon
from webargs import fields, validate
from webargs.falconparser import use_args, use_kwargs, parser

### Middleware and hooks ###


class JSONTranslator:
    def process_response(self, req, resp, resource):
        if "result" not in req.context:
            return
        resp.body = json.dumps(req.context["result"])


def add_args(argmap, **kwargs):
    def hook(req, resp, params):
        req.context["args"] = parser.parse(argmap, req=req, **kwargs)

    return hook


### Resources ###


class HelloResource:
    """A welcome page."""

    hello_args = {"name": fields.Str(missing="Friend", location="query")}

    @use_args(hello_args)
    def on_get(self, req, resp, args):
        req.context["result"] = {"message": "Welcome, {}!".format(args["name"])}


class AdderResource:
    """An addition endpoint."""

    adder_args = {"x": fields.Float(required=True), "y": fields.Float(required=True)}

    @use_kwargs(adder_args)
    def on_post(self, req, resp, x, y):
        req.context["result"] = {"result": x + y}


class DateAddResource:
    """A datetime adder endpoint."""

    dateadd_args = {
        "value": fields.Date(required=False),
        "addend": fields.Int(required=True, validate=validate.Range(min=1)),
        "unit": fields.Str(
            missing="days", validate=validate.OneOf(["minutes", "days"])
        ),
    }

    @falcon.before(add_args(dateadd_args))
    def on_post(self, req, resp):
        """A datetime adder endpoint."""
        args = req.context["args"]
        value = args["value"] or dt.datetime.utcnow()
        if args["unit"] == "minutes":
            delta = dt.timedelta(minutes=args["addend"])
        else:
            delta = dt.timedelta(days=args["addend"])
        result = value + delta
        req.context["result"] = {"result": result.isoformat()}


app = falcon.API(middleware=[JSONTranslator()])
app.add_route("/", HelloResource())
app.add_route("/add", AdderResource())
app.add_route("/dateadd", DateAddResource())