import logging
from werkzeug.utils import cached_property
from piecrust.configuration import ConfigurationError
from piecrust.page import Page


REALM_USER = 0
REALM_THEME = 1
REALM_NAMES = {
        REALM_USER: 'User',
        REALM_THEME: 'Theme'}


MODE_PARSING = 0
MODE_CREATING = 1


logger = logging.getLogger(__name__)


def build_pages(app, factories):
    with app.env.page_repository.startBatchGet():
        for f in factories:
            yield f.buildPage()


class InvalidFileSystemEndpointError(Exception):
    def __init__(self, source_name, fs_endpoint):
        super(InvalidFileSystemEndpointError, self).__init__(
                "Invalid file-system endpoint for source '%s': %s" %
                (source_name, fs_endpoint))


class PageFactory(object):
    """ A class responsible for creating a page.
    """
    def __init__(self, source, rel_path, metadata):
        self.source = source
        self.rel_path = rel_path
        self.metadata = metadata

    @cached_property
    def ref_spec(self):
        return '%s:%s' % (self.source.name, self.rel_path)

    @cached_property
    def path(self):
        return self.source.resolveRef(self.rel_path)

    def buildPage(self):
        repo = self.source.app.env.page_repository
        if repo is not None:
            cache_key = '%s:%s' % (self.source.name, self.rel_path)
            return repo.get(cache_key, self._doBuildPage)
        return self._doBuildPage()

    def _doBuildPage(self):
        logger.debug("Building page: %s" % self.path)
        page = Page(self.source, self.metadata, self.rel_path)
        # Load it right away, especially when using the page repository,
        # because we'll be inside a critical scope.
        page._load()
        return page


class PageSource(object):
    """ A source for pages, e.g. a directory with one file per page.
    """
    def __init__(self, app, name, config):
        self.app = app
        self.name = name
        self.config = config or {}
        self.config.setdefault('realm', REALM_USER)
        self._factories = None
        self._provider_type = None

    def __getattr__(self, name):
        try:
            return self.config[name]
        except KeyError:
            raise AttributeError()

    @property
    def is_theme_source(self):
        return self.realm == REALM_THEME

    @property
    def root_dir(self):
        if self.is_theme_source:
            return self.app.theme_dir
        return self.app.root_dir

    def getPages(self):
        return build_pages(self.app, self.getPageFactories())

    def getPage(self, metadata):
        rel_path, metadata = self.findPagePath(metadata, MODE_PARSING)
        if rel_path is None:
            return None
        return Page(self, metadata, rel_path)

    def getPageFactories(self):
        if self._factories is None:
            self._factories = list(self.buildPageFactories())
        return self._factories

    def buildPageFactories(self):
        raise NotImplementedError()

    def resolveRef(self, ref_path):
        raise NotImplementedError()

    def findPagePath(self, metadata, mode):
        raise NotImplementedError()

    def buildDataProvider(self, page, user_data):
        if self._provider_type is None:
            cls = next((pt for pt in self.app.plugin_loader.getDataProviders()
                        if pt.PROVIDER_NAME == self.data_type),
                       None)
            if cls is None:
                raise ConfigurationError(
                        "Unknown data provider type: %s" % self.data_type)
            self._provider_type = cls

        return self._provider_type(self, page, user_data)

    def getTaxonomyPageRef(self, tax_name):
        tax_pages = self.config.get('taxonomy_pages')
        if tax_pages is None:
            return None
        return tax_pages.get(tax_name)