# Copyright (C) 2018 The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information

from types import GeneratorType


def merge(*dicts):
    """Given an iterator of dicts, merge them losing no information.

    Args:
        *dicts: arguments are all supposed to be dict to merge into one

    Returns:
        dict merged without losing information

    """
    def _extend(existing_val, value):
        """Given an existing value and a value (as potential lists), merge
           them together without repetition.

        """
        if isinstance(value, (list, map, GeneratorType)):
            vals = value
        else:
            vals = [value]
        for v in vals:
            if v in existing_val:
                continue
            existing_val.append(v)
        return existing_val

    d = {}
    for data in dicts:
        if not isinstance(data, dict):
            raise ValueError(
                'dicts is supposed to be a variable arguments of dict')

        for key, value in data.items():
            existing_val = d.get(key)
            if not existing_val:
                d[key] = value
                continue
            if isinstance(existing_val, (list, map, GeneratorType)):
                new_val = _extend(existing_val, value)
            elif isinstance(existing_val, dict):
                if isinstance(value, dict):
                    new_val = merge(existing_val, value)
                else:
                    new_val = _extend([existing_val], value)
            else:
                new_val = _extend([existing_val], value)
            d[key] = new_val
    return d