from contextlib import suppress

from .exceptions import BundleError, ItemDependencyError, NoSuchItem
from .items import Item
from .items.actions import Action
from .utils.text import bold, mark_for_translation as _
from .utils.ui import io


class DummyItem:
    bundle = None
    cascade_skip = True
    triggered = False

    def __init__(self, *args, **kwargs):
        self.needed_by = []
        self.needs = []
        self.preceded_by = []
        self.precedes = []
        self.tags = []
        self.triggered_by = []
        self.triggers = []
        self._deps = []
        self._precedes_items = []

    def __lt__(self, other):
        return self.id < other.id

    def _precedes_incorrect_item(self):
        return False

    def apply(self, *args, **kwargs):
        return (Item.STATUS_OK, [])

    def test(self):
        pass


class BundleItem(DummyItem):
    """
    Represents a dependency on all items in a certain bundle.
    """
    ITEM_TYPE_NAME = 'bundle'

    def __init__(self, bundle):
        self.bundle = bundle
        super(BundleItem, self).__init__()

    def __repr__(self):
        return "<BundleItem: {}>".format(self.bundle.name)

    @property
    def id(self):
        return "bundle:{}".format(self.bundle.name)


class TagItem(DummyItem):
    """
    This item depends on all items with the given tag.
    """
    ITEM_TYPE_NAME = 'tag'

    def __init__(self, tag_name):
        self.tag_name = tag_name
        super(TagItem, self).__init__()

    def __repr__(self):
        return "<TagItem: {}>".format(self.tag_name)

    @property
    def id(self):
        return "tag:{}".format(self.tag_name)


class TypeItem(DummyItem):
    """
    Represents a dependency on all items of a certain type.
    """
    ITEM_TYPE_NAME = 'type'

    def __init__(self, item_type):
        self.item_type = item_type
        super(TypeItem, self).__init__()

    def __repr__(self):
        return "<TypeItem: {}>".format(self.item_type)

    @property
    def id(self):
        return "{}:".format(self.item_type)


def find_item(item_id, items):
    """
    Returns the first item with the given ID within the given list of
    items.
    """
    try:
        item = list(filter(lambda item: item.id == item_id, items))[0]
    except IndexError:
        raise NoSuchItem(_("item not found: {}").format(item_id))
    return item


def _find_items_of_types(item_types, items, include_dummy=False):
    """
    Returns a subset of items with any of the given types.
    """
    for item_id, item in items.items():
        if item_id.split(":", 1)[0] in item_types and (
            include_dummy or not isinstance(item, DummyItem)
        ):
            yield item


def _flatten_dependencies(items):
    """
    This will cause all dependencies - direct AND inherited - to be
    listed in item._flattened_deps.
    """
    for item in items.values():
        if not hasattr(item, '_flattened_deps'):
            _flatten_deps_for_item(item, items)

    for item in list(items.values()):
        item._incoming_deps = set()
        for other_item in list(items.values()):
            if isinstance(other_item, DummyItem):
                continue
            if item.id in other_item._flattened_deps:
                item._incoming_deps.add(other_item)
    return items


def _flatten_deps_for_item(item, items):
    """
    Recursively retrieves and returns a list of all inherited
    dependencies of the given item.

    This can handle loops, but will ignore them.
    """
    item._flattened_deps = set(item._deps)

    for dep in item._deps.copy():
        try:
            dep_item = items[dep]
        except KeyError:
            if dep.startswith("tag:"):
                # sometimes it is useful to be able to depend on a tag
                # without having to make sure it actually exists
                item._deps.remove(dep)
                continue
            else:
                raise ItemDependencyError(_(
                    "'{item}' in bundle '{bundle}' has a dependency (needs) "
                    "on '{dep}', which doesn't exist"
                ).format(
                    item=item.id,
                    bundle=item.bundle.name,
                    dep=dep,
                ))
        # Don't recurse if we have already resolved nested dependencies
        # for this item. Also serves as a guard against infinite
        # recursion when there are loops.
        if not hasattr(dep_item, '_flattened_deps'):
            _flatten_deps_for_item(dep_item, items)

        item._flattened_deps |= set(dep_item._flattened_deps)

    item._flattened_deps = sorted(item._flattened_deps)


def _has_trigger_path(items, item, target_item_id):
    """
    Returns True if the given item directly or indirectly (trough
    other items) triggers the item with the given target item id.
    """
    if target_item_id in item.triggers:
        return True
    for triggered_id in item.triggers:
        try:
            triggered_item = find_item(triggered_id, items)
        except NoSuchItem:
            # the triggered item may already have been skipped by
            # `bw apply -s`
            continue
        if _has_trigger_path(items, triggered_item, target_item_id):
            return True
    return False


def _inject_bundle_items(items):
    """
    Adds virtual items that depend on every item in a bundle.
    """
    bundle_items = {}
    for item in items.values():
        if item.bundle is None:
            continue
        if item.bundle.name not in bundle_items:
            bundle_items[item.bundle.name] = BundleItem(item.bundle)
        bundle_items[item.bundle.name]._deps.append(item.id)
    items.update({item.id: item for item in bundle_items.values()})
    return items


def _inject_canned_actions(items):
    """
    Looks for canned actions like "svc_upstart:mysql:reload" in item
    triggers and adds them to the list of items.
    """
    added_actions = {}
    for item in items.values():
        for triggered_item_id in item.triggers:
            if triggered_item_id in added_actions:
                # action has already been triggered
                continue

            try:
                type_name, item_name, action_name = triggered_item_id.split(":")
            except ValueError:
                # not a canned action
                continue

            target_item_id = "{}:{}".format(type_name, item_name)

            try:
                target_item = items[target_item_id]
            except KeyError:
                raise BundleError(_(
                    "{item} in bundle '{bundle}' triggers unknown item '{target_item}'"
                ).format(
                    bundle=item.bundle.name,
                    item=item.id,
                    target_item=target_item_id,
                ))

            try:
                action_attrs = target_item.get_canned_actions()[action_name]
            except KeyError:
                raise BundleError(_(
                    "{item} in bundle '{bundle}' triggers unknown "
                    "canned action '{action}' on {target_item}"
                ).format(
                    action=action_name,
                    bundle=item.bundle.name,
                    item=item.id,
                    target_item=target_item_id,
                ))

            action_attrs.update({'triggered': True})
            action = Action(
                item.bundle,
                triggered_item_id,
                action_attrs,
                skip_name_validation=True,
            )
            action._prepare_deps(items)
            added_actions[triggered_item_id] = action

    items.update({item.id: item for item in added_actions.values()})
    return items


def _inject_concurrency_blockers(items, node_os, node_os_version):
    """
    Looks for items with BLOCK_CONCURRENT set and inserts daisy-chain
    dependencies to force a sequential apply.
    """
    # find every item type that cannot be applied in parallel
    item_types = set()
    for item in items.values():
        item._concurrency_deps = []  # used for DOT (graphviz) output only
        if (
            not isinstance(item, DummyItem) and
            item.block_concurrent(node_os, node_os_version)
        ):
            item_types.add(item.__class__)

    # Now that we have collected all relevant types,
    # we must group them together when they overlap. E.g.:
    #
    #     Type1.block_concurrent(...) == ["type1", "type2"]
    #     Type2.block_concurrent(...) == ["type2", "type3"]
    #     Type4.block_concurrent(...) == ["type4"]
    #
    # becomes
    #
    #     ["type1", "type2", "type3"]
    #     ["type4"]
    #
    # because the first two types overlap in blocking type2. This is
    # necessary because existing dependencies from type3 to type1 need
    # to be taken into account when generating the daisy-chains
    # connecting the three types. If we processed blockers for Type1 and
    # Type2 independently, we might end up with two very different
    # chains for Type2, which may cause circular dependencies.

    chain_groups = []
    for item_type in item_types:
        block_concurrent = [item_type.ITEM_TYPE_NAME]
        block_concurrent.extend(item_type.block_concurrent(node_os, node_os_version))
        for blocked_types in chain_groups:
            for blocked_type in block_concurrent:
                if blocked_type in blocked_types:
                    blocked_types.extend(block_concurrent)
                    break
        else:
            chain_groups.append(block_concurrent)

    # daisy-chain all items of the chain group while respecting existing
    # dependencies between them
    for blocked_types in chain_groups:
        blocked_types = set(blocked_types)
        type_items = list(_find_items_of_types(
            blocked_types,
            items,
        ))
        processed_items = []
        for item in type_items:
            # disregard deps to items of other types
            item.__deps = list(filter(
                lambda dep: dep.split(":", 1)[0] in blocked_types,
                item._flattened_deps,
            ))
        previous_item = None
        while len(processed_items) < len(type_items):
            # find the first item without same-type deps we haven't
            # processed yet
            try:
                item = list(filter(
                    lambda item: not item.__deps and item not in processed_items,
                    type_items,
                ))[0]
            except IndexError:
                # this can happen if the flattened deps of all items of
                # this type already contain a dependency on another
                # item of this type
                break
            if previous_item is not None:  # unless we're at the first item
                # add dep to previous item -- unless it's already in there
                if previous_item.id not in item._deps:
                    item._deps.append(previous_item.id)
                    item._concurrency_deps.append(previous_item.id)
                    item._flattened_deps.append(previous_item.id)
            previous_item = item
            processed_items.append(item)
            # Now remove all deps on the processed item. This frees up
            # items depending *only* on the processed item to be
            # eligible for the next iteration of this loop.
            for other_item in type_items:
                with suppress(ValueError):
                    other_item.__deps.remove(item.id)
    return items


def _inject_tag_items(items):
    """
    Takes a list of items and adds tag items depending on each type of
    item in the list. Returns the appended list.
    """
    tag_items = {}
    for item in items.values():
        for tag in item.tags:
            if tag not in tag_items:
                tag_items[tag] = TagItem(tag)
            tag_items[tag]._deps.append(item.id)
    items.update({item.id: item for item in tag_items.values()})
    return items


def _inject_type_items(items):
    """
    Takes a list of items and adds dummy items depending on each type of
    item in the list. Returns the appended list.
    """
    type_items = {}
    for item in items.values():
        # create dummy items that depend on each item of their type
        item_type = item.id.split(":")[0]
        if item_type not in type_items:
            type_items[item_type] = TypeItem(item_type)
        type_items[item_type]._deps.append(item.id)

        # create DummyItem for every type
        for dep in item._deps:
            item_type = dep.split(":")[0]
            if item_type not in type_items:
                type_items[item_type] = TypeItem(item_type)

    items.update({item.id: item for item in type_items.values()})
    return items


def _inject_reverse_dependencies(items):
    """
    Looks for 'needed_by' deps and creates standard dependencies
    accordingly.
    """
    def add_dep(item, dep):
        if dep not in item._deps:
            item._deps.append(dep)
            item._reverse_deps.append(dep)

    for item in items.values():
        item._reverse_deps = []

    for item in items.values():
        for depending_item_id in item.needed_by:
            # bundle items
            if depending_item_id.startswith("bundle:"):
                depending_bundle_name = depending_item_id.split(":")[1]
                for depending_item in items.values():
                    if isinstance(depending_item, DummyItem):
                        # Type and TagItems don't have bundles
                        continue
                    if depending_item.bundle.name == depending_bundle_name:
                        add_dep(depending_item, item.id)

            # tag items
            if depending_item_id.startswith("tag:"):
                tag_name = depending_item_id.split(":")[1]
                for depending_item in items.values():
                    if tag_name in depending_item.tags:
                        add_dep(depending_item, item.id)

            # type items
            if depending_item_id.endswith(":"):
                target_type = depending_item_id[:-1]
                for depending_item in _find_items_of_types([target_type], items):
                    add_dep(depending_item, item.id)

            # single items
            else:
                try:
                    depending_item = items[depending_item_id]
                except KeyError:
                    raise ItemDependencyError(_(
                        "'{item}' in bundle '{bundle}' has a reverse dependency (needed_by) "
                        "on '{dep}', which doesn't exist"
                    ).format(
                        item=item.id,
                        bundle=item.bundle.name,
                        dep=depending_item_id,
                    ))
                add_dep(depending_item, item.id)
    return items


def _inject_reverse_triggers(items):
    """
    Looks for 'triggered_by' and 'precedes' attributes and turns them
    into standard triggers (defined on the opposing end).
    """
    for item in items.values():
        for triggering_item_id in item.triggered_by:
            try:
                triggering_item = items[triggering_item_id]
            except KeyError:
                raise ItemDependencyError(_(
                    "'{item}' in bundle '{bundle}' has a reverse trigger (triggered_by) "
                    "on '{dep}', which doesn't exist"
                ).format(
                    item=item.id,
                    bundle=item.bundle.name,
                    dep=triggering_item_id,
                ))
            if triggering_item.id.startswith("bundle:"):  # bundle items
                bundle_name = triggering_item.id.split(":")[1]
                for actual_triggering_item in items.values():
                    if triggering_item.bundle.name == bundle_name:
                        actual_triggering_item.triggers.append(item.id)
            elif triggering_item.id.startswith("tag:"):  # tag items
                tag_name = triggering_item.id.split(":")[1]
                for actual_triggering_item in items.values():
                    if tag_name in triggering_item.tags:
                        actual_triggering_item.triggers.append(item.id)
            elif triggering_item.id.endswith(":"):  # type items
                target_type = triggering_item.id[:-1]
                for actual_triggering_item in _find_items_of_types([target_type], items):
                    actual_triggering_item.triggers.append(item.id)
            else:
                triggering_item.triggers.append(item.id)
        for preceded_item_id in item.precedes:
            try:
                preceded_item = items[preceded_item_id]
            except KeyError:
                raise ItemDependencyError(_(
                    "'{item}' in bundle '{bundle}' has a reverse trigger (precedes) "
                    "on '{dep}', which doesn't exist"
                ).format(
                    item=item.id,
                    bundle=item.bundle.name,
                    dep=preceded_item_id,
                ))
            if preceded_item.id.startswith("bundle:"):  # bundle items
                bundle_name = preceded_item.id.split(":")[1]
                for actual_preceded_item in items.values():
                    if actual_preceded_item.bundle.name == bundle_name:
                        actual_preceded_item.preceded_by.append(item.id)
            elif preceded_item.id.startswith("tag:"):  # tag items
                tag_name = preceded_item.id.split(":")[1]
                for actual_preceded_item in items.values():
                    if tag_name in actual_preceded_item.tags:
                        actual_preceded_item.preceded_by.append(item.id)
            elif preceded_item.id.endswith(":"):  # type items
                target_type = preceded_item.id[:-1]
                for actual_preceded_item in _find_items_of_types([target_type], items):
                    actual_preceded_item.preceded_by.append(item.id)
            else:
                preceded_item.preceded_by.append(item.id)
    return items


def _inject_trigger_dependencies(items):
    """
    Injects dependencies from all triggered items to their triggering
    items.
    """
    for item in items.values():
        for triggered_item_id in item.triggers:
            try:
                triggered_item = items[triggered_item_id]
            except KeyError:
                raise BundleError(_(
                    "unable to find definition of '{item1}' triggered "
                    "by '{item2}' in bundle '{bundle}'"
                ).format(
                    bundle=item.bundle.name,
                    item1=triggered_item_id,
                    item2=item.id,
                ))
            if not triggered_item.triggered:
                raise BundleError(_(
                    "'{item1}' in bundle '{bundle1}' triggered "
                    "by '{item2}' in bundle '{bundle2}', "
                    "but missing 'triggered' attribute"
                ).format(
                    item1=triggered_item.id,
                    bundle1=triggered_item.bundle.name,
                    item2=item.id,
                    bundle2=item.bundle.name,
                ))
            triggered_item._deps.append(item.id)
    return items


def _inject_preceded_by_dependencies(items):
    """
    Injects dependencies from all triggering items to their
    preceded_by items and attaches triggering items to preceding items.
    """
    for item in items.values():
        if item.preceded_by and item.triggered:
            raise BundleError(_(
                "triggered item '{item}' in bundle '{bundle}' must not use "
                "'preceded_by' (use chained triggers instead)".format(
                    bundle=item.bundle.name,
                    item=item.id,
                ),
            ))
        for triggered_item_id in item.preceded_by:
            try:
                triggered_item = items[triggered_item_id]
            except KeyError:
                raise BundleError(_(
                    "unable to find definition of '{item1}' preceding "
                    "'{item2}' in bundle '{bundle}'"
                ).format(
                    bundle=item.bundle.name,
                    item1=triggered_item_id,
                    item2=item.id,
                ))
            if not triggered_item.triggered:
                raise BundleError(_(
                    "'{item1}' in bundle '{bundle1}' precedes "
                    "'{item2}' in bundle '{bundle2}', "
                    "but missing 'triggered' attribute"
                ).format(
                    item1=triggered_item.id,
                    bundle1=triggered_item.bundle.name,
                    item2=item.id,
                    bundle2=item.bundle.name if item.bundle else "N/A",
                ))
            triggered_item._precedes_items.append(item)
            item._deps.append(triggered_item.id)
    return items


@io.job_wrapper(_("{}  processing dependencies").format(bold("{1}")))
def prepare_dependencies(items, node_os, node_os_version):
    """
    Performs all dependency preprocessing on a list of items.
    """
    for item in items:
        item._check_bundle_collisions(items)
        item._check_loopback_dependency()
        item._prepare_deps(items)

    # transform items into a dict to prevent repeated item.id lookups
    items = {item.id: item for item in items}

    items = _inject_bundle_items(items)
    items = _inject_tag_items(items)
    items = _inject_type_items(items)
    items = _inject_canned_actions(items)
    items = _inject_reverse_triggers(items)
    items = _inject_reverse_dependencies(items)
    items = _inject_trigger_dependencies(items)
    items = _inject_preceded_by_dependencies(items)
    items = _flatten_dependencies(items)
    items = _inject_concurrency_blockers(items, node_os, node_os_version)

    for item in items.values():
        if not isinstance(item, DummyItem):
            item._check_redundant_dependencies()

    return list(items.values())


def remove_dep_from_items(items, dep):
    """
    Removes the given item id (dep) from the temporary list of
    dependencies of all items in the given list.
    """
    for item in items:
        with suppress(ValueError):
            item._deps.remove(dep)
    return items


def remove_item_dependents(items, dep_item, skipped=False):
    """
    Removes the items depending on the given item from the list of items.
    """
    removed_items = []
    for item in items:
        if dep_item.id in item._deps:
            if _has_trigger_path(items, dep_item, item.id):
                # triggered items cannot be removed here since they
                # may yet be triggered by another item and will be
                # skipped anyway if they aren't
                item._deps.remove(dep_item.id)
            elif skipped and isinstance(item, DummyItem) and \
                    dep_item.triggered and not dep_item.has_been_triggered:
                # don't skip dummy items because of untriggered members
                # see issue #151; separate elif for clarity
                item._deps.remove(dep_item.id)
            elif dep_item.id in item._concurrency_deps:
                # don't skip items just because of concurrency deps
                # separate elif for clarity
                item._deps.remove(dep_item.id)
            else:
                removed_items.append(item)

    for item in removed_items:
        items.remove(item)

    if removed_items:
        io.debug(
            "skipped these items because they depend on {item}, which was "
            "skipped previously: {skipped}".format(
                item=dep_item.id,
                skipped=", ".join([item.id for item in removed_items]),
            )
        )

    all_recursively_removed_items = []
    for removed_item in removed_items:
        if removed_item.cascade_skip:
            items, recursively_removed_items = \
                remove_item_dependents(items, removed_item, skipped=skipped)
            all_recursively_removed_items += recursively_removed_items
        else:
            items = remove_dep_from_items(items, removed_item.id)

    return (items, removed_items + all_recursively_removed_items)


def split_items_without_deps(items):
    """
    Takes a list of items and extracts the ones that don't have any
    dependencies. The extracted deps are returned as a list.
    """
    remaining_items = []
    removed_items = []
    for item in items:
        if item._deps:
            remaining_items.append(item)
        else:
            removed_items.append(item)
    return (remaining_items, removed_items)
