# XPath parsing

import copy

import warnings

from Parser import Parser

import util

import xml_dom

##### Path elements

class XpathElem:

    def __init__(self, name='', value=None, is_attr=False):

        self.name = name

        self.value = value

        self.is_attr = is_attr

        self.is_positive = True

        self.is_lookup_only = False

        self.is_ptr = False

        self.keys = []

        self.attrs = []

        self.other_branches = [] # temp implementation for split paths

    def __repr__(self):

        str_ = ''

        if not self.is_positive: str_ += '!'

        if self.is_attr: str_ += '@'

        if self.name == '': str_ += '""'

        else: str_ += self.name

        if self.is_lookup_only: str_ += '?'

        if self.keys != []: str_ += repr(self.keys)

        if self.attrs != []: str_ += ':'+repr(self.attrs)

        if self.is_ptr: str_ += '->'

        if self.other_branches != []: str_ += '{'+repr(self.other_branches)+'}'

        if self.value != None: str_ += '='+repr(self.value)

        return str_

    def __eq__(self, other): return self.__dict__ == other.__dict__

empty_elem = XpathElem()

def elem_is_empty(elem): return elem == empty_elem

def is_self(elem): return elem.name == '' or elem.name == '.'

def is_parent(elem): return elem.name == '..'

##### Paths

def is_positive(path): return path[0].is_positive

def is_rooted(path): return elem_is_empty(path[0])

def value(path): return path[-1].value

def set_value(path, value):

    '''Caller must make a shallow copy of the path to prevent modifications from

    propagating to other copies of the path (a deep copy is not needed)'''

    path[-1] = copy.copy(path[-1]) # don't modify other copies of the path

    path[-1].value = value

def backward_id(elem):

    if len(elem.keys) >= 1 and value(elem.keys[0]) == None: return elem.keys[0]

    else: return None

instance_level = 1 # root's grandchildren

def obj(path):

    obj_path = copy.deepcopy(path[:instance_level+1])

    obj_path[-1].is_ptr = False # prevent pointer w/o target

    return obj_path

def set_id(path, id_, has_types=True):

    '''Caller must make a shallow copy of the path to prevent modifications from

    propagating to other copies of the path (a deep copy is not needed)'''

    if has_types: id_level = instance_level

    else: id_level = 0 # root's children

    if is_self(path[0]): id_level += 1 # explicit root element

    id_elem = path[id_level] = copy.copy(path[id_level])

        # don't modify other copies of the path

    id_elem.keys = id_elem.keys[:] # don't modify other copies of the elem

    id_elem.keys.append([XpathElem('id', id_, True)])

def is_id(path): return path[0].is_attr and path[0].name == 'id'

def is_instance(elem): return elem.keys != [] and is_id(elem.keys[0])

##### Parsing

def expand_abbr(name, repl):

    before, abbr, after = name.partition('*')

    if abbr != '': name = before+repl+after

    return name

_cache = {}

def parse(str_):

    try: return _cache[str_]

    except KeyError: pass

    parser = Parser(str_)

    def _path():

        is_positive = not parser.str_('!')

        tree = []

        while True:

            # Split path

            if parser.str_('{'):

                last = tree[-1]

                last.other_branches = _paths()

                parser.str_('}', required=True)

                if parser.str_('/'): # common subpath after {}

                    subpath = _path()

                    for branch in last.other_branches: branch += subpath

                tree += last.other_branches.pop(0) # use first path for now

                break # anything after split path has already been parsed

            elem = XpathElem(is_attr=parser.str_('@'), name=_value())

            elem.is_lookup_only = parser.str_('?')

            # Keys used to match nodes

            if parser.str_('['):

                elem.keys = _paths()

                parser.str_(']', required=True)

            # Attrs created when no matching node exists

            if parser.str_(':'):

                parser.str_('[', required=True)

                elem.attrs = _paths()

                parser.str_(']', required=True)

            elem.is_ptr = parser.str_('->')

            tree.append(elem)

            # Lookahead assertion

            if parser.str_('('):

                parser.str_('/', required=True) # next / is inside ()

                path = _path()

                parser.str_(')', required=True)

                elem.keys.append(path)

                tree += path

            if not parser.str_('/'): break

        tree[0].is_positive = is_positive

        # Value

        if parser.str_('='):

            if parser.str_('$'): # reference (different from a pointer)

                value = _path()

            else: value = _value() # literal value

            set_value(tree, value)

        # Expand * abbrs

        for i in reversed(xrange(len(tree))):

            elem = tree[i]

            if elem.is_ptr: offset = 2

            else: offset = 1

            try: repl = tree[i+offset].name

            except IndexError: pass # no replacement elem

            else: elem.name = expand_abbr(elem.name, repl)

        return tree

    def _value():

        if parser.str_('"'):

            value = parser.re(r'[^"]*')

            parser.str_('"', required=True)

        else: value = parser.re(r'(?:(?:\w+:)*[\w.*]+)?')

        return value

    def _paths():

        paths = []

        while True:

            paths.append(_path())

            if not parser.str_(','): break

        return paths

    path = _path()

    parser.end()

    _cache[str_] = path

    return path

##### Querying/creating XML trees

def get(root, xpath, create=False, last_only=None, limit=1, allow_rooted=True):

    '''Warning: The last_only optimization may put data that should be together

    into separate nodes'''

    if last_only == None: last_only = create

    if limit == None or limit > 1: last_only = False

    if util.is_str(xpath): xpath = parse(xpath)

    # Handle edge cases

    if xpath == []: return [root]

    if create and not is_positive(xpath): return []

    # Define vars

    doc = root.ownerDocument

    if allow_rooted and is_rooted(xpath): root = doc.documentElement

    elem = xpath[0]

    # Find possible matches

    children = []

    if elem.is_attr:

        child = root.getAttributeNode(elem.name)

        if child != None: children = [child]

    elif is_self(elem): children = [root]

    elif is_parent(elem):

        parent = xml_dom.parent(root)

        if parent == None: return [] # don't try to create doc root's parent

        root = parent

        children = [root]

    else:

        children = xml_dom.by_tag_name(root, elem.name,

            last_only and (elem.keys == [] or is_instance(elem)))

    # Retrieve elem value

    value_ = elem.value

    if util.is_list(value_): # reference (different from a pointer)

        targets = get(root, value_)

        try: target = targets[0]

        except IndexError:

            warnings.warn(UserWarning('XPath reference target missing: '

                +str(value_)+'\nXPath: '+str(xpath)))

            value_ = None

        else: value_ = xml_dom.value(target)

    # Check each match

    nodes = []

    for child in children:

        is_match = value_ == None or xml_dom.value(child) == value_

        for attr in elem.keys:

            if not is_match: break

            is_match = ((get(child, attr, False, last_only,

                allow_rooted=False) != []) == is_positive(attr))

        if is_match:

            nodes.append(child)

            if limit != None and len(nodes) >= limit: break

    # Create node

    if nodes == []:

        if not create or elem.is_lookup_only: return []

        if elem.is_attr:

            root.setAttribute(elem.name, '')

            node = root.getAttributeNode(elem.name)

        elif util.list_eq_is(children, [root]): node = root

        else: node = root.appendChild(doc.createElement(elem.name))

        if value_ != None: xml_dom.set_value(node, value_)

        nodes.append(node)

    path_value = value(xpath)

    xpath = xpath[1:] # rest of XPath

    next = []

    for node in nodes:

        # Create attrs

        if create:

            for attr in elem.keys + elem.attrs:

                get(node, attr, create, last_only, allow_rooted=False)

        # Follow pointer

        if elem.is_ptr:

            root = doc.documentElement

            xpath = copy.deepcopy(xpath)

            id_path = backward_id(xpath[instance_level])

            if id_path != None: # backward (child-to-parent) pointer with ID key

                id_path[0].name = expand_abbr(id_path[0].name, node.tagName)

                set_value(id_path, xml_dom.get_id(node)) # modify xpath's id key

            else: # forward (parent-to-child) pointer

                id_ = xml_dom.value(node)

                obj_xpath = obj(xpath) # target object

                if id_ == None or get(root, obj_xpath, False, True) == []:

                    # no target or target keys don't match

                    if not create: continue

                    # Use last target object's ID + 1

                    obj_xpath[-1].keys = [] # just get by tag name

                    last = get(root, obj_xpath, False, True)

                    if last != []: id_ = str(int(xml_dom.get_id(last[0])) + 1)

                    else: id_ = '0'

                    # Will append if target keys didn't match.

                    # Use lookahead assertion to avoid this.

                    xml_dom.set_value(node, id_)

                else: last_only = False

                set_id(xpath, id_)

        else: root = node

        next += get(root, xpath, create, last_only, limit, allow_rooted=False)

        for branch in elem.other_branches:

            branch = branch[:] # don't modify input!

            set_value(branch, path_value)

            next += get(node, branch, create, last_only, limit,

                allow_rooted=False)

    return next

def put_obj(root, xpath, id_, has_types, value=None):

    if util.is_str(xpath): xpath = parse(xpath)

    xpath = xpath[:] # don't modify input!

    set_id(xpath, id_, has_types)

    if value != None: set_value(xpath, value)

    get(root, xpath, True)

def path2xml(xpath, first_branch=True):

    root = xml_dom.create_doc().documentElement

    get(root, xpath, True)

    return root

def xml_set_id(root, id_): xml_dom.set_id(root.firstChild, id_)