from django.db import models

class superModel:
    def _serialize(self):
        fields = self._meta.fields
        # fields that can't be null and are not 'id'
        nnf = [f for f in fields if not f.null and f.name != 'id']
        d = {}
        for f in nnf:
            if not isinstance(f, models.ForeignKey):
                d[f.name] = getattr(self, f.name)
            else:
                d[f.name] = getattr(self, f.name).id
        return d

    def _default(cls):
        """Returns a dictionary with defaults for blank/default fields
        and None for required fields."""
        fields = cls._meta.fields
        nnf = [f for f in fields if not f.null and f.name != 'id']
        d = {}
        for f in nnf:
            # check if it's an auto_now_add DateTimeField
            if isinstance(f, models.DateTimeField):
                if f.auto_now_add: continue
            # if f has a default lets use it...
            if f.has_default(): d[f.name] = f.default
            elif f.blank: d[f.name] = ''
            else: d[f.name] = None
        return d

    # by default, we'll do nothing to the value
    def _filter_value(key, value): return value

    def _flatten_post(post):
        "Takes a mutable copy of a serialized POST and returns it with correct keys."
        for key,val in post.items():
            try:
                post[key.split('_')[1]] = val
                del post[key]
            except: pass
        return post

    def _merge_post(c, request, obj=None):
        post = c._flatten_post(request.POST.copy())
        if obj == None: obj = c._default()
        else: obj = obj._serialize()
        for key,value in obj.items():
            if post.has_key(key):
                post[key] = c._filter_value(key, post[key])
            else:
                post[key] = obj[key]
        return post

    _default = classmethod(_default)
    _merge_post = classmethod(_merge_post)
    _flatten_post = staticmethod(_flatten_post)