import logging

from volatility.framework import interfaces

vollog = logging.getLogger(__name__)


class ConstructionMagic(interfaces.automagic.AutomagicInterface):
    """Runs through the requirement tree and from the bottom up attempts to construct all TranslationLayerRequirements

       This should run first to prevent existing configurations getting re-configured
    """
    priority = 0

    def __call__(self, context, config_path, requirement, optional = False):
        if not requirement.validate(context, config_path):
            # Having called validate at the top level tells us both that we need to dig deeper
            # but also ensures that TranslationLayerRequirements have got the correct subrequirements if their class is populated

            success = True
            subreq_config_path = interfaces.configuration.path_join(config_path, requirement.name)
            for subreq in requirement.requirements.values():
                self(context, subreq_config_path, subreq, optional or subreq.optional)
                valid = subreq.validate(context, subreq_config_path)
                # We want to traverse optional paths, so don't check until we've tried to validate
                # We also don't want to emit a debug message when a parent is optional, hence the optional parameter
                if not valid and not (optional or subreq.optional):
                    vollog.debug("Failed on requirement: {}".format(subreq_config_path))
                    success = False
            if not success:
                return False
            elif isinstance(requirement, interfaces.configuration.ConstructableRequirementInterface):
                # We know all the subrequirements are filled, so let's populate
                requirement.construct(context, config_path)
        return True