from __future__ import unicode_literals
from __future__ import absolute_import
from . import util

from copy import deepcopy

def iteritems_compat(d):
    """Return an iterator over the (key, value) pairs of a dictionary.
    Copied from `six` module."""
    return iter(getattr(d, _iteritems)())

class OrderedDict(dict):
    """
    A dictionary that keeps its keys in the order in which they're inserted.
    
    Copied from Django's SortedDict with some modifications.

    """
    def __new__(cls, *args, **kwargs):
        instance = super(OrderedDict, cls).__new__(cls, *args, **kwargs)
        instance.keyOrder = []
        return instance

    def __init__(self, data=None):
        if data is None or isinstance(data, dict):
            data = data or []
            super(OrderedDict, self).__init__(data)
            self.keyOrder = list(data) if data else []
        else:
            super(OrderedDict, self).__init__()
            super_set = super(OrderedDict, self).__setitem__
            for key, value in data:
                # Take the ordering from first key
                if key not in self:
                    self.keyOrder.append(key)
                # But override with last value in data (dict() does this)
                super_set(key, value)

    def __deepcopy__(self, memo):
        return self.__class__([(key, deepcopy(value, memo))
                               for key, value in self.items()])

    def __copy__(self):
        # The Python's default copy implementation will alter the state
        # of self. The reason for this seems complex but is likely related to
        # subclassing dict.
        return self.copy()

    def __setitem__(self, key, value):
        if key not in self:
            self.keyOrder.append(key)
        super(OrderedDict, self).__setitem__(key, value)

    def __delitem__(self, key):
        super(OrderedDict, self).__delitem__(key)
        self.keyOrder.remove(key)

    def __iter__(self):
        return iter(self.keyOrder)

    def __reversed__(self):
        return reversed(self.keyOrder)

    def pop(self, k, *args):
        result = super(OrderedDict, self).pop(k, *args)
        try:
            self.keyOrder.remove(k)
        except ValueError:
            # Key wasn't in the dictionary in the first place. No problem.
            pass
        return result

    def popitem(self):
        result = super(OrderedDict, self).popitem()
        self.keyOrder.remove(result[0])
        return result

    def _iteritems(self):
        for key in self.keyOrder:
            yield key, self[key]

    def _iterkeys(self):
        for key in self.keyOrder:
            yield key

    def _itervalues(self):
        for key in self.keyOrder:
            yield self[key]

    if util.PY3:
        items = _iteritems
        keys = _iterkeys
        values = _itervalues
    else:
        iteritems = _iteritems
        iterkeys = _iterkeys
        itervalues = _itervalues

        def items(self):
            return [(k, self[k]) for k in self.keyOrder]

        def keys(self):
            return self.keyOrder[:]

        def values(self):
            return [self[k] for k in self.keyOrder]

    def update(self, dict_):
        for k, v in iteritems_compat(dict_):
            self[k] = v

    def setdefault(self, key, default):
        if key not in self:
            self.keyOrder.append(key)
        return super(OrderedDict, self).setdefault(key, default)

    def value_for_index(self, index):
        """Returns the value of the item at the given zero-based index."""
        return self[self.keyOrder[index]]

    def insert(self, index, key, value):
        """Inserts the key, value pair before the item with the given index."""
        if key in self.keyOrder:
            n = self.keyOrder.index(key)
            del self.keyOrder[n]
            if n < index:
                index -= 1
        self.keyOrder.insert(index, key)
        super(OrderedDict, self).__setitem__(key, value)

    def copy(self):
        """Returns a copy of this object."""
        # This way of initializing the copy means it works for subclasses, too.
        return self.__class__(self)

    def __repr__(self):
        """
        Replaces the normal dict.__repr__ with a version that returns the keys
        in their Ordered order.
        """
        return '{%s}' % ', '.join(['%r: %r' % (k, v) for k, v in iteritems_compat(self)])

    def clear(self):
        super(OrderedDict, self).clear()
        self.keyOrder = []

    def index(self, key):
        """ Return the index of a given key. """
        try:
            return self.keyOrder.index(key)
        except ValueError:
            raise ValueError("Element '%s' was not found in OrderedDict" % key)

    def index_for_location(self, location):
        """ Return index or None for a given location. """
        if location == '_begin':
            i = 0
        elif location == '_end':
            i = None
        elif location.startswith('<') or location.startswith('>'):
            i = self.index(location[1:])
            if location.startswith('>'):
                if i >= len(self):
                    # last item
                    i = None
                else:
                    i += 1
        else:
            raise ValueError('Not a valid location: "%s". Location key '
                             'must start with a ">" or "<".' % location)
        return i

    def add(self, key, value, location):
        """ Insert by key location. """
        i = self.index_for_location(location)
        if i is not None:
            self.insert(i, key, value)
        else:
            self.__setitem__(key, value)

    def link(self, key, location):
        """ Change location of an existing item. """
        n = self.keyOrder.index(key)
        del self.keyOrder[n]
        try:
            i = self.index_for_location(location)
            if i is not None:
                self.keyOrder.insert(i, key)
            else:
                self.keyOrder.append(key)
        except Exception as e:
            # restore to prevent data loss and reraise
            self.keyOrder.insert(n, key)
            raise e
