# -*- coding: utf-8 -*-
"""Decorators for registering schema pre-processing and post-processing methods.
These should be imported from the top-level `marshmallow` module.

Example: ::

    from marshmallow import (
        Schema, pre_load, pre_dump, post_load, validates_schema,
        validates, fields, ValidationError
    )

    class UserSchema(Schema):

        email = fields.Str(required=True)
        age = fields.Integer(required=True)

        @post_load
        def lowerstrip_email(self, item):
            item['email'] = item['email'].lower().strip()
            return item

        @pre_load(pass_many=True)
        def remove_envelope(self, data, many):
            namespace = 'results' if many else 'result'
            return data[namespace]

        @post_dump(pass_many=True)
        def add_envelope(self, data, many):
            namespace = 'results' if many else 'result'
            return {namespace: data}

        @validates_schema
        def validate_email(self, data):
            if len(data['email']) < 3:
                raise ValidationError('Email must be more than 3 characters', 'email')

        @validates('age')
        def validate_age(self, data):
            if data < 14:
                raise ValidationError('Too young!')

.. note::
    These decorators only work with instance methods. Class and static
    methods are not supported.

.. warning::
    The invocation order of decorated methods of the same type is not guaranteed.
    If you need to guarantee order of different processing steps, you should put
    them in the same processing method.
"""
from __future__ import unicode_literals

import functools


PRE_DUMP = 'pre_dump'
POST_DUMP = 'post_dump'
PRE_LOAD = 'pre_load'
POST_LOAD = 'post_load'
VALIDATES = 'validates'
VALIDATES_SCHEMA = 'validates_schema'


def validates(field_name):
    """Register a field validator.

    :param str field_name: Name of the field that the method validates.
    """
    return tag_processor(VALIDATES, None, False, field_name=field_name)


def validates_schema(fn=None, pass_many=False, pass_original=False, skip_on_field_errors=True):
    """Register a schema-level validator.

    By default, receives a single object at a time, regardless of whether ``many=True``
    is passed to the `Schema`. If ``pass_many=True``, the raw data (which may be a collection)
    and the value for ``many`` is passed.

    If ``pass_original=True``, the original data (before unmarshalling) will be passed as
    an additional argument to the method.

    If ``skip_on_field_errors=True``, this validation method will be skipped whenever
    validation errors have been detected when validating fields.

    .. versionchanged:: 3.0.0b1
        ``skip_on_field_errors`` defaults to `True`.
    """
    return tag_processor(VALIDATES_SCHEMA, fn, pass_many, pass_original=pass_original,
                         skip_on_field_errors=skip_on_field_errors)


def pre_dump(fn=None, pass_many=False):
    """Register a method to invoke before serializing an object. The method
    receives the object to be serialized and returns the processed object.

    By default, receives a single object at a time, regardless of whether ``many=True``
    is passed to the `Schema`. If ``pass_many=True``, the raw data (which may be a collection)
    and the value for ``many`` is passed.
    """
    return tag_processor(PRE_DUMP, fn, pass_many)


def post_dump(fn=None, pass_many=False, pass_original=False):
    """Register a method to invoke after serializing an object. The method
    receives the serialized object and returns the processed object.

    By default, receives a single object at a time, transparently handling the ``many``
    argument passed to the Schema. If ``pass_many=True``, the raw data
    (which may be a collection) and the value for ``many`` is passed.
    """
    return tag_processor(POST_DUMP, fn, pass_many, pass_original=pass_original)


def pre_load(fn=None, pass_many=False):
    """Register a method to invoke before deserializing an object. The method
    receives the data to be deserialized and returns the processed data.

    By default, receives a single datum at a time, transparently handling the ``many``
    argument passed to the Schema. If ``pass_many=True``, the raw data
    (which may be a collection) and the value for ``many`` is passed.
    """
    return tag_processor(PRE_LOAD, fn, pass_many)


def post_load(fn=None, pass_many=False, pass_original=False):
    """Register a method to invoke after deserializing an object. The method
    receives the deserialized data and returns the processed data.

    By default, receives a single datum at a time, transparently handling the ``many``
    argument passed to the Schema. If ``pass_many=True``, the raw data
    (which may be a collection) and the value for ``many`` is passed.
    """
    return tag_processor(POST_LOAD, fn, pass_many, pass_original=pass_original)


def tag_processor(tag_name, fn, pass_many, **kwargs):
    """Tags decorated processor function to be picked up later.

    .. note::
        Currently ony works with functions and instance methods. Class and
        static methods are not supported.

    :return: Decorated function if supplied, else this decorator with its args
        bound.
    """
    # Allow using this as either a decorator or a decorator factory.
    if fn is None:
        return functools.partial(
            tag_processor, tag_name, pass_many=pass_many, **kwargs
        )

    # Set a marshmallow_tags attribute instead of wrapping in some class,
    # because I still want this to end up as a normal (unbound) method.
    try:
        marshmallow_tags = fn.__marshmallow_tags__
    except AttributeError:
        fn.__marshmallow_tags__ = marshmallow_tags = set()
    # Also save the kwargs for the tagged function on
    # __marshmallow_kwargs__, keyed by (<tag_name>, <pass_many>)
    try:
        marshmallow_kwargs = fn.__marshmallow_kwargs__
    except AttributeError:
        fn.__marshmallow_kwargs__ = marshmallow_kwargs = {}
    marshmallow_tags.add((tag_name, pass_many))
    marshmallow_kwargs[(tag_name, pass_many)] = kwargs

    return fn
