"""A simple number and datetime addition JSON API.
Run the app:

    $ python examples/tornado_example.py

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

    $ pip install httpie
    $ http GET :5001/
    $ http GET :5001/ name==Ada
    $ http POST :5001/add x=40 y=2
    $ http POST :5001/dateadd value=1973-04-10 addend=63
    $ http POST :5001/dateadd value=2014-10-23 addend=525600 unit=minutes
"""
import datetime as dt

import tornado.ioloop
from tornado.web import RequestHandler
from webargs import fields, validate
from webargs.tornadoparser import use_args, use_kwargs


class BaseRequestHandler(RequestHandler):
    def write_error(self, status_code, **kwargs):
        """Write errors as JSON."""
        self.set_header("Content-Type", "application/json")
        if "exc_info" in kwargs:
            etype, exc, traceback = kwargs["exc_info"]
            if hasattr(exc, "messages"):
                self.write({"errors": exc.messages})
                if getattr(exc, "headers", None):
                    for name, val in exc.headers.items():
                        self.set_header(name, val)
                self.finish()


class HelloHandler(BaseRequestHandler):
    """A welcome page."""

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

    @use_args(hello_args)
    def get(self, args):
        response = {"message": "Welcome, {}!".format(args["name"])}
        self.write(response)


class AdderHandler(BaseRequestHandler):
    """An addition endpoint."""

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

    @use_kwargs(add_args)
    def post(self, x, y):
        self.write({"result": x + y})


class DateAddHandler(BaseRequestHandler):
    """A date 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"])
        ),
    }

    @use_kwargs(dateadd_args)
    def post(self, value, addend, unit):
        """A date adder endpoint."""
        value = value or dt.datetime.utcnow()
        if unit == "minutes":
            delta = dt.timedelta(minutes=addend)
        else:
            delta = dt.timedelta(days=addend)
        result = value + delta
        self.write({"result": result.isoformat()})


if __name__ == "__main__":
    app = tornado.web.Application(
        [(r"/", HelloHandler), (r"/add", AdderHandler), (r"/dateadd", DateAddHandler)],
        debug=True,
    )
    port = 5001
    app.listen(port)
    print(f"Serving on port {port}")
    tornado.ioloop.IOLoop.instance().start()