import logging
from piecrust.data.filters import PaginationFilter, IsFilterClause, NotClause
from piecrust.environment import AbortedSourceUseError
from piecrust.events import Event
from piecrust.sources.base import PageSource
from piecrust.sources.interfaces import IPaginationSource


logger = logging.getLogger(__name__)


class SliceIterator(object):
    def __init__(self, it, offset=0, limit=-1):
        self.it = it
        self.offset = offset
        self.limit = limit
        self.current_page = None
        self.has_more = False
        self.inner_count = -1
        self.next_page = None
        self.prev_page = None
        self._cache = None

    def __iter__(self):
        if self._cache is None:
            inner_list = list(self.it)
            self.inner_count = len(inner_list)

            if self.limit > 0:
                self.has_more = self.inner_count > (self.offset + self.limit)
                self._cache = inner_list[self.offset:self.offset + self.limit]
            else:
                self.has_more = False
                self._cache = inner_list[self.offset:]

            if self.current_page:
                try:
                    idx = inner_list.index(self.current_page)
                except ValueError:
                    idx = -1
                if idx >= 0:
                    if idx < self.inner_count - 1:
                        self.next_page = inner_list[idx + 1]
                    if idx > 0:
                        self.prev_page = inner_list[idx - 1]

        return iter(self._cache)


class SettingFilterIterator(object):
    def __init__(self, it, fil_conf, setting_accessor=None):
        self.it = it
        self.fil_conf = fil_conf
        self._fil = None
        self.setting_accessor = setting_accessor

    def __iter__(self):
        if self._fil is None:
            self._fil = PaginationFilter(value_accessor=self.setting_accessor)
            self._fil.addClausesFromConfig(self.fil_conf)

        for i in self.it:
            if self._fil.pageMatches(i):
                yield i


class NaturalSortIterator(object):
    def __init__(self, it, reverse=False):
        self.it = it
        self.reverse = reverse

    def __iter__(self):
        return iter(sorted(self.it, reverse=self.reverse))


class SettingSortIterator(object):
    def __init__(self, it, name, reverse=False, value_accessor=None):
        self.it = it
        self.name = name
        self.reverse = reverse
        self.value_accessor = value_accessor or self._default_value_accessor

    def __iter__(self):
        return iter(sorted(self.it, key=self._key_getter,
                           reverse=self.reverse))

    def _key_getter(self, item):
        key = self.value_accessor(item, self.name)
        if key is None:
            return 0
        return key

    @staticmethod
    def _default_value_accessor(item, name):
        try:
            return getattr(item, name)
        except AttributeError:
            return None


class PaginationFilterIterator(object):
    def __init__(self, it, fil):
        self.it = it
        self._fil = fil

    def __iter__(self):
        for page in self.it:
            if self._fil.pageMatches(page):
                yield page


class PageIterator(object):
    debug_render = []
    debug_render_doc_dynamic = ['_debugRenderDoc']
    debug_render_not_empty = True

    def __init__(self, source, current_page=None, pagination_filter=None,
            offset=0, limit=-1, locked=False):
        self._source = source
        self._current_page = current_page
        self._locked = False
        self._pages = source
        self._pagesData = None
        self._pagination_slicer = None
        self._has_sorter = False
        self._next_page = None
        self._prev_page = None
        self._iter_event = Event()

        if isinstance(source, IPaginationSource):
            src_it = source.getSourceIterator()
            if src_it is not None:
                self._pages = src_it

        # If we're currently baking, apply the default baker filter
        # to exclude things like draft posts.
        if (isinstance(source, PageSource) and
                source.app.config.get('baker/is_baking')):
            setting_name = source.app.config.get('baker/no_bake_setting',
                                                 'draft')
            accessor = self._getSettingAccessor()
            draft_filter = PaginationFilter(accessor)
            draft_filter.root_clause = NotClause()
            draft_filter.root_clause.addClause(
                    IsFilterClause(setting_name, True))
            self._simpleNonSortedWrap(
                    PaginationFilterIterator, draft_filter)

        # Apply any filter first, before we start sorting or slicing.
        if pagination_filter is not None:
            self._simpleNonSortedWrap(PaginationFilterIterator,
                                      pagination_filter)

        if offset > 0 or limit > 0:
            self.slice(offset, limit)

        self._locked = locked

    @property
    def total_count(self):
        self._load()
        if self._pagination_slicer is not None:
            return self._pagination_slicer.inner_count
        return len(self._pagesData)

    @property
    def next_page(self):
        self._load()
        return self._next_page

    @property
    def prev_page(self):
        self._load()
        return self._prev_page

    def __len__(self):
        self._load()
        return len(self._pagesData)

    def __getitem__(self, key):
        self._load()
        return self._pagesData[key]

    def __iter__(self):
        self._load()
        self._iter_event.fire()
        return iter(self._pagesData)

    def __getattr__(self, name):
        if name[:3] == 'is_' or name[:3] == 'in_':
            def is_filter(value):
                conf = {'is_%s' % name[3:]: value}
                accessor = self._getSettingAccessor()
                return self._simpleNonSortedWrap(SettingFilterIterator, conf,
                                                 accessor)
            return is_filter

        if name[:4] == 'has_':
            def has_filter(value):
                conf = {name: value}
                accessor = self._getSettingAccessor()
                return self._simpleNonSortedWrap(SettingFilterIterator, conf,
                                                 accessor)
            return has_filter

        if name[:5] == 'with_':
            def has_filter(value):
                conf = {'has_%s' % name[5:]: value}
                accessor = self._getSettingAccessor()
                return self._simpleNonSortedWrap(SettingFilterIterator, conf,
                                                 accessor)
            return has_filter

        return self.__getattribute__(name)

    def skip(self, count):
        return self._simpleWrap(SliceIterator, count)

    def limit(self, count):
        return self._simpleWrap(SliceIterator, 0, count)

    def slice(self, skip, limit):
        return self._simpleWrap(SliceIterator, skip, limit)

    def filter(self, filter_name):
        if self._current_page is None:
            raise Exception("Can't use `filter()` because no parent page was "
                            "set for this page iterator.")
        filter_conf = self._current_page.config.get(filter_name)
        if filter_conf is None:
            raise Exception("Couldn't find filter '%s' in the configuration "
                            "header for page: %s" %
                            (filter_name, self._current_page.path))
        accessor = self._getSettingAccessor()
        return self._simpleNonSortedWrap(SettingFilterIterator, filter_conf,
                                         accessor)

    def sort(self, setting_name=None, reverse=False):
        self._ensureUnlocked()
        self._unload()
        if setting_name is not None:
            accessor = self._getSettingAccessor()
            self._pages = SettingSortIterator(self._pages, setting_name,
                                              reverse, accessor)
        else:
            self._pages = NaturalSortIterator(self._pages, reverse)
        self._has_sorter = True
        return self

    def reset(self):
        self._ensureUnlocked()
        self._unload
        return self

    @property
    def _has_more(self):
        self._load()
        if self._pagination_slicer:
            return self._pagination_slicer.has_more
        return False

    def _simpleWrap(self, it_class, *args, **kwargs):
        self._ensureUnlocked()
        self._unload()
        self._ensureSorter()
        self._pages = it_class(self._pages, *args, **kwargs)
        if self._pagination_slicer is None and it_class is SliceIterator:
            self._pagination_slicer = self._pages
            self._pagination_slicer.current_page = self._current_page
        return self

    def _simpleNonSortedWrap(self, it_class, *args, **kwargs):
        self._ensureUnlocked()
        self._unload()
        self._pages = it_class(self._pages, *args, **kwargs)
        return self

    def _getSettingAccessor(self):
        accessor = None
        if isinstance(self._source, IPaginationSource):
            accessor = self._source.getSettingAccessor()
        return accessor

    def _ensureUnlocked(self):
        if self._locked:
            raise Exception(
                    "This page iterator has been locked, probably because "
                    "you're trying to tamper with pagination data.")

    def _ensureSorter(self):
        if self._has_sorter:
            return
        if isinstance(self._source, IPaginationSource):
            sort_it = self._source.getSorterIterator(self._pages)
            if sort_it is not None:
                self._pages = sort_it
        self._has_sorter = True

    def _unload(self):
        self._pagesData = None
        self._next_page = None
        self._prev_page = None

    def _load(self):
        if self._pagesData is not None:
            return

        if (self._current_page is not None and
                self._current_page.app.env.abort_source_use and
                isinstance(self._source, PageSource)):
            logger.debug("Aborting iteration from %s." %
                         self._current_page.ref_spec)
            raise AbortedSourceUseError()

        self._ensureSorter()

        it_chain = self._pages
        is_pgn_source = False
        if isinstance(self._source, IPaginationSource):
            is_pgn_source = True
            tail_it = self._source.getTailIterator(self._pages)
            if tail_it is not None:
                it_chain = tail_it

        self._pagesData = list(it_chain)

        if is_pgn_source and self._current_page and self._pagination_slicer:
            pn = [self._pagination_slicer.prev_page,
                    self._pagination_slicer.next_page]
            pn_it = self._source.getTailIterator(iter(pn))
            self._prev_page, self._next_page = (list(pn_it))

    def _debugRenderDoc(self):
        return "Contains %d items" % len(self)