from decorator import decorator
import flask
import itertools
import json

def _validate(data, *args, **kwargs):
    for key in itertools.chain(args, kwargs.keys()):
        if not key in data:
            flask.abort(403, json.dumps({'error': 'missing parameter',
                                   'param': key}))
        for key, val in kwargs.iteritems():
            flask.abort(403, json.dumps({'error': 'validation failed',
                                   'param': key}))


def must(*args, **kwargs):
    """
    Asserts that a given set of keys are present in the request parameters.
    Also allows for keyword args to handle validation.
    """
    def tester(func):
        def funky(*iargs, **ikwargs):
            _validate(flask.request.params, *args, **kwargs)
            return func(*iargs, **ikwargs)
        return decorator(funky, func)
    return tester


@decorator
def returns_json(func, *args, **kwargs):
    status, content = func(*args, **kwargs)
    response = flask.make_response(
        json.dumps(content), status)
    response.headers['Content-type'] = 'application/json'
    return response


def json_must(*args, **kwargs):
    """Implements a simple validation system to allow for the required
       keys to be detected on a given callable."""
    def unpack(func):
        def dejson(f, *iargs):
            if flask.request.headers.get('content-type', '') != "application/json":
                flask.abort(403, json.dumps({"error": "must be in JSON format"}))
            # todo -- parse_float was handled specially
            _validate(flask.request.json, *args, **kwargs)
            return func(*iargs)
        return decorator(dejson, func)
    return unpack