from functools import wraps
from flask import request
import jsonschema


class ValidationError(Exception):
    def __init__(self, message):
        Exception.__init__(self)
        self.message = message


def _check_parameter_exists(param):
    if not param in request.args:
        raise ValidationError("No {} is specified".format(param))


def _is_number(s):
    try:
        float(s)
        return True
    except ValueError:
        return False


def validate_jsonschema(schema):
    def decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            if not request.json:
                raise ValidationError("Payload is not valid json")
            try:
                j = request.json
                jsonschema.validate(j, schema)
            except jsonschema.ValidationError as e:
                raise ValidationError(e.message)
            except jsonschema.SchemaError as e:
                raise ValidationError(e.message)
            return f(*args, **kwargs)

        return wrapper

    return decorator


def validate_exists(*keys):
    def decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            for key in keys:
                _check_parameter_exists(key)
            return f(*args, **kwargs)

        return wrapper

    return decorator


def validate_number(*keys):
    def decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            for key in keys:
                _check_parameter_exists(key)
                value = request.args.get(key)
                if not _is_number(value):
                    raise ValidationError("{} is not a number".format(key))
            return f(*args, **kwargs)

        return wrapper

    return decorator


def validate_any_of(key, values):
    def decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            _check_parameter_exists(key)
            value = request.args.get(key)
            if not value in values:
                raise ValidationError(
                    "{} contains an invalid value, must be one of: {}".format(
                        key, values
                    )
                )
            return f(*args, **kwargs)

        return wrapper

    return decorator