#
# SchoolTool - common information systems platform for school administration
# Copyright (c) 2012 Shuttleworth Foundation
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
"""Skills document model."""
import itertools

from persistent import Persistent
from zope.container.btree import BTreeContainer
from zope.container.contained import Contained
from zope.component import adapts, adapter
from zope.component import getUtility
from zope.interface import implements, implementer
from zope.intid import addIntIdSubscriber
from zope.intid.interfaces import IIntIds
from zope.lifecycleevent import ObjectAddedEvent
from zope.lifecycleevent.interfaces import IObjectRemovedEvent
from zope.security.proxy import removeSecurityProxy

from schooltool.app.app import InitBase, StartUpBase
from schooltool.app.interfaces import ISchoolToolApplication
from schooltool.cando import interfaces
from schooltool.cando.skill import URISkillSet
from schooltool.relationship import URIObject
from schooltool.relationship import RelationshipSchema, RelationshipProperty
from schooltool.relationship.interfaces import InvalidRelationship
from schooltool.relationship.interfaces import IBeforeRelationshipEvent
from schooltool.relationship.interfaces import IBeforeRemovingRelationshipEvent


URILayer = URIObject(
    'http://schooltool.org/ns/cando/model/layer',
    'Layer',
    'A layer of the model.')

URIParentLayer = URIObject(
    'http://schooltool.org/ns/cando/model/parent_layer',
    'Parent layer',
    'A parent layer.')

URILayerLink = URIObject(
    'http://schooltool.org/ns/cando/model/layer_link',
    'Layer link',
    'A link between two layers in the model.')

LayerLink = RelationshipSchema(URILayerLink,
                              parent=URIParentLayer,
                              child=URILayer)


URINodeLink = URIObject(
    'http://schooltool.org/ns/cando/model/node_link',
    'Node link',
    'A link between two nodes in the model.')

URINode = URIObject(
    'http://schooltool.org/ns/cando/model/node',
    'Node',
    'A node.')

URIParentNode = URIObject(
    'http://schooltool.org/ns/cando/model/parent_node',
    'Parent node',
    'A parent node.')

NodeLink = RelationshipSchema(URINodeLink,
                              parent=URIParentNode,
                              child=URINode)

URINodeLayer = URIObject(
    'http://schooltool.org/ns/cando/model/node_layer',
    'Node layer',
    'A model layer the node is in.')

NodeLayer = RelationshipSchema(URINodeLayer,
                               node=URINode,
                               layer=URILayer)


URINodeSkillSets = URIObject(
    'http://schooltool.org/ns/cando/model/node_skillsets',
    'Node skillsets',
    'Skillsets this model node implements.')

NodeSkillSets = RelationshipSchema(
    URINodeSkillSets,
    node=URINode,
    skillset=URISkillSet)
# XXX: order in extra_info if neccessary


URIDocument = URIObject(
    'http://schooltool.org/ns/cando/model/document',
    'Document',
    'A document.')

URIDocumentHierarchy = URIObject(
    'http://schooltool.org/ns/cando/model/document_hierarchy',
    'Document hierarchy',
    'A model layer that is in the document hierarchy.')

DocumentHierarchy = RelationshipSchema(URIDocumentHierarchy,
                                       document=URIDocument,
                                       layer=URILayer)


class LayerContainer(BTreeContainer):
    """Container of layers."""
    implements(interfaces.ILayerContainer)


class Layer(Persistent, Contained):
    implements(interfaces.ILayerContained)

    title = None
    parents = RelationshipProperty(URILayerLink, URILayer, URIParentLayer)
    children = RelationshipProperty(URILayerLink, URIParentLayer, URILayer)

    def __init__(self, title):
        self.title = title

    def __repr__(self):
        return '<%s %r>' % (self.__class__.__name__, self.title)


@adapter(ISchoolToolApplication)
@implementer(interfaces.ILayerContainer)
def getLayerContainer(app):
    return app['schooltool.cando.layer']


class LayerAppInit(InitBase):

    def __call__(self):
        self.app['schooltool.cando.layer'] = LayerContainer()


class LayerStartUp(StartUpBase):

    def __call__(self):
        if 'schooltool.cando.layer' not in self.app:
            self.app['schooltool.cando.layer'] = LayerContainer()


class NodeContainer(BTreeContainer):
    """Container of nodes."""
    implements(interfaces.INodeContainer)


class Node(Persistent, Contained):
    implements(interfaces.INodeContained)

    title = u''
    description = u''
    label = u''
    layers = RelationshipProperty(URINodeLayer, URINode, URILayer)
    parents = RelationshipProperty(URINodeLink, URINode, URIParentNode)
    children = RelationshipProperty(URINodeLink, URIParentNode, URINode)
    skillsets = RelationshipProperty(URINodeSkillSets, URINode, URISkillSet)

    def __init__(self, title=u'', description=u'', label=u''):
        self.title = title
        self.description = description
        self.label = label

    def findPaths(self):
        paths = [(self,)]
        expanded = True
        while expanded:
            expanded = False
            prev_paths = paths
            paths = []
            for path in prev_paths:
                parents = sorted(list(path[0].parents), key=lambda n:n.__name__)
                if parents:
                    for parent in parents:
                        paths.append((parent,)+path)
                        expanded = True
                else:
                    paths.append(path)
        return paths

    def __repr__(self):
        return '<%s %r %s>' % (self.__class__.__name__, self.title,
                               ', '.join([str(l) for l in self.layers]))


@adapter(ISchoolToolApplication)
@implementer(interfaces.INodeContainer)
def getNodeContainer(app):
    return app['schooltool.cando.node']


class NodeAppInit(InitBase):

    def __call__(self):
        self.app['schooltool.cando.node'] = NodeContainer()


class NodeStartUp(StartUpBase):

    def __call__(self):
        if 'schooltool.cando.node' not in self.app:
            self.app['schooltool.cando.node'] = NodeContainer()


class CyclicRelationship(InvalidRelationship):

    def __init__(self, child, parent, parents):
        self.child = child
        self.parent = parent
        self.parents = parents
        InvalidRelationship.__init__(self, child, parent, parents)

    def __str__(self):
        return '%s' % (
            '\n'.join([
                    'child %s' % self.child,
                    'target parent %s' % self.parent,
                    'distant parents %s' % ', '.join(
                        sorted([str(l) for l in self.parents]))
                    ]))


def _expand_nodes(nodes, functor, recursive=True):
    nodes = set(nodes)
    open = set(nodes)
    parents = set()
    while open:
        p = open.pop()
        if p not in parents:
            if recursive or p in nodes:
                open.update(set(functor(p)).difference(parents))
            if p not in nodes:
                parents.add(p)
    return parents


@adapter(IBeforeRelationshipEvent)
def preventLayerCycles(event):
    match = event.match(LayerLink)
    if match is None:
        match = event.match(NodeLink)
    if match is None:
        return
    parent = removeSecurityProxy(match.parent)
    child = removeSecurityProxy(match.child)
    # Explicitly don't handle existing child-parent relationships,
    # only parent loops.  So, check only parents of parent node.
    parents = _expand_nodes(nodes=[parent], functor=lambda n: n.parents)
    if child in parents:
        raise CyclicRelationship(child, parent, parents)


class ViolateLayerModel(InvalidRelationship):
    pass


def validateAgainstNode(candidate, distant_parent, valid_layers):
    open = set([distant_parent])
    while open:
        # Walk up to parents with layers and check if our layers are valid
        with_no_layers = set()
        for model_node in open:
            node_layers = list(model_node.layers)
            if node_layers:
                for layer in node_layers:
                    if layer not in valid_layers:
                        raise ViolateLayerModel('\n'.join([
                            'candidate %s' % candidate,
                            'acceptable parent layers %s' % ', '.join(
                                sorted([str(l) for l in valid_layers])),
                            'violates parent %s' % model_node]))
            else:
                with_no_layers.add(model_node)
        open = _expand_nodes(nodes=with_no_layers,
                             functor=lambda n:n.parents,
                             recursive=False)


@adapter(IBeforeRelationshipEvent)
def nodeLinkDoesntViolateModel(event):
    match = event.match(NodeLink)
    if match is None:
        return
    parent = removeSecurityProxy(match.parent)
    child = removeSecurityProxy(match.child)

    child_layers = set(child.layers)
    if child_layers:
        valid_layers = _expand_nodes(child_layers,
                                     functor=lambda n: n.parents,
                                     recursive=False)
        validateAgainstNode(child, parent, valid_layers)

    def expand_children_if_without_layers(node):
        if node.layers:
            return []
        return NodeLink.query(parent=node)

    check_children = _expand_nodes(nodes=[child],
                                   functor=expand_children_if_without_layers)
    for node in check_children:
        node_layers = set(node.layers)
        if node_layers:
            valid_layers = set(itertools.chain(*[n.parents for n in node_layers]))
            validateAgainstNode(node, parent, valid_layers)


class InvalidLayerLink(InvalidRelationship):

    def __init__(self, layer=None, node=None, offends_node=None):
        self.layer = layer
        self.node = node
        self.offends_node = offends_node
        InvalidRelationship.__init__(
            self, layer, node, offends_node)

    def __str__(self):
        return '%s' % (
            '\n'.join([
                    'setting layer %s' % self.layer,
                    'for node %s' % self.node,
                    'offends node %s' % self.offends_node,
                    ]))


def makeLayerValidator(functor, valid_set, invalid_set):
    def validator(node):
        node_layers = set(node.layers)
        offending_layers = node_layers.intersection(invalid_set)
        if offending_layers:
            raise InvalidLayerLink(offends_node=node)
        if not node_layers.isdisjoint(valid_set):
            # valid layer found, stop expanding
            return []
        return functor(node)
    return validator


@adapter(IBeforeRelationshipEvent)
def nodeLayerDoesntViolateModel(event):
    match = event.match(NodeLayer)
    if match is None:
        return
    node = removeSecurityProxy(match.node)
    layer = removeSecurityProxy(match.layer)

    get_layer_parents = lambda l:LayerLink.query(child=l)
    get_layer_children = lambda l:LayerLink.query(parent=l)

    immediate_parents = set(_expand_nodes(
            [layer], functor=get_layer_parents, recursive=False))
    distant_parents = set(_expand_nodes(
            immediate_parents, functor=get_layer_parents))
    all_parents = immediate_parents.union(distant_parents)

    immediate_children = set(_expand_nodes(
            [layer], functor=get_layer_children, recursive=False))
    distant_children = set(_expand_nodes(
            immediate_children, functor=get_layer_children))
    all_children = immediate_children.union(distant_children)

    valid_parents = immediate_parents
    invalid_parents = distant_parents.union(all_children)

    get_node_parents = lambda l:NodeLink.query(child=l)
    get_node_children = lambda l:NodeLink.query(parent=l)

    try:
        _expand_nodes([node], functor=makeLayerValidator(
                functor=get_node_parents,
                valid_set=valid_parents,
                invalid_set=invalid_parents,
                ))
    except InvalidLayerLink, e:
        raise InvalidLayerLink(
            layer=layer, node=node, offends_node=e.offends_node)

    valid_children = immediate_children
    invalid_children = distant_children.union(all_parents)

    try:
        _expand_nodes([node], functor=makeLayerValidator(
                functor=get_node_children,
                valid_set=valid_children,
                invalid_set=invalid_children,
                ))
    except InvalidLayerLink, e:
        raise InvalidLayerLink(
            layer=layer, node=node, offends_node=e.offends_node)


class CannotRemoveLayer(InvalidRelationship):

    def __init__(self, layer=None, node=None,
                 parent_nodes=None, child_nodes=None):
        self.layer = layer
        self.node = node
        self.parent_nodes = parent_nodes
        self.child_nodes = child_nodes
        InvalidRelationship.__init__(
            self, layer, node, parent_nodes, child_nodes)

    def __str__(self):
        return '%s' % (
            '\n'.join([
                    'setting layer %s' % self.layer,
                    'for node %s' % self.node,
                    'breaks parents %s' % ', '.join(
                        sorted([str(l) for l in self.parent_nodes])),
                    'and children %s' % ', '.join(
                        sorted([str(l) for l in self.child_nodes])),
                    ]))


def makeNodeWithLayersFinder(layers, functor, result):
    def find_node_with_layers(node):
        matched_layers = layers.intersection(set(node.layers))
        if matched_layers:
            result.append(node)
            return []
        return functor(node)
    return find_node_with_layers


@adapter(IBeforeRemovingRelationshipEvent)
def removingLayerDoesntViolateModel(event):
    match = event.match(NodeLayer)
    if match is None:
        return
    node = removeSecurityProxy(match.node)
    layer = removeSecurityProxy(match.layer)
    get_layer_parents = lambda l:LayerLink.query(child=l)
    get_layer_children = lambda l:LayerLink.query(parent=l)
    immediate_parents = set(_expand_nodes(
            [layer], functor=get_layer_parents, recursive=False))
    immediate_children = set(_expand_nodes(
            [layer], functor=get_layer_children, recursive=False))

    get_node_parents = lambda l:NodeLink.query(child=l)
    parent_nodes_in_model = []
    _expand_nodes(
        [node],
        functor=makeNodeWithLayersFinder(
            immediate_parents, get_node_parents, parent_nodes_in_model
            ))

    get_node_children = lambda l:NodeLink.query(parent=l)
    child_nodes_in_model = []
    _expand_nodes(
        [node],
        functor=makeNodeWithLayersFinder(
            immediate_children, get_node_children, child_nodes_in_model
            ))

    if parent_nodes_in_model and child_nodes_in_model:
        raise CannotRemoveLayer(
            layer=layer, node=node,
            parent_nodes=parent_nodes_in_model,
            child_nodes=child_nodes_in_model)


class DocumentContainer(BTreeContainer):
    """Container of documents."""
    implements(interfaces.IDocumentContainer)


class Document(Node):
    implements(interfaces.IDocumentContained)

    hierarchy = RelationshipProperty(URIDocumentHierarchy, URIDocument,
                                     URILayer)

    def getOrderedHierarchy(self):
        layers = list(self.hierarchy)
        result = []
        for index, layer in enumerate(layers):
            for parent in layer.parents:
                if parent in layers:
                    break
            else:
                result.append(layer)
                layers.pop(index)
                break
        if not result:
            return result
        while layers:
            for index, layer in enumerate(layers):
                if result[-1] in layer.parents:
                    result.append(layer)
                    layers.pop(index)
                    break
            else:
                break
        return result

    def __repr__(self):
        return '<%s %r %s>' % (self.__class__.__name__, self.title,
            ', '.join([str(l) for l in self.getOrderedHierarchy()]))


@adapter(ISchoolToolApplication)
@implementer(interfaces.IDocumentContainer)
def getDocumentContainer(app):
    return app['schooltool.cando.document']


class DocumentAppInit(InitBase):

    def __call__(self):
        self.app['schooltool.cando.document'] = DocumentContainer()


class DocumentStartUp(StartUpBase):

    def __call__(self):
        if 'schooltool.cando.document' not in self.app:
            self.app['schooltool.cando.document'] = DocumentContainer()

