# XML-database conversion

from xml.dom import Node

import db_util

import xml_util

from xml_util import name_of

ptr_suffix = '_id'

def is_ptr(node_name): return node_name.endswith(ptr_suffix)

def ptr_type(node_name):

    assert is_ptr(node_name)

    return node_name[:-len(ptr_suffix)]

def ptr_target(node):

    assert is_ptr(name_of(node))

    return xml_util.first_elem(node)

def pkey_name(node_name): return node_name+ptr_suffix

def is_field(node_name): return node_name.find('.') >= 0

def field_name(node_name):

    if is_field(node_name): return node_name.partition('.')[2]

    else: return node_name

def is_db_export(node_name): return node_name.find('.') >= 1 # has prefix

def find_by_name(node, name):

    for parent in xml_util.NodeParentIter(node):

        if name_of(parent) == name: return parent

        else:

            for child in xml_util.NodeElemIter(parent):

                child_name = field_name(name_of(child))

                if is_ptr(child_name):

                    if ptr_type(child_name) == name: return ptr_target(child)

                elif child_name == name: return child

    return None

def xml2db(node, db):

    def _main(node):

        for child in xml_util.NodeElemIter(node):

            if not xml_util.is_text(child): _obj(child) # not XML metadata

    def _obj(node):

        table = name_of(node)

        db_util.check_name(table)

        pkey = pkey_name(table)

        row = {}

        children = []

        iter_ = xml_util.NodeElemIter(node)

        # Skip any pkey

        child_name = name_of(iter_.curr()) # first child

        if is_db_export(child_name) and is_ptr(child_name)\

        or field_name(child_name) == pkey: iter_.next()

        # Divide children into fields and children with fkeys to parent

        for child in iter_:

            if is_field(name_of(child)): row.update([_field(child)])

            else: children.append(child)

        # Add fkey to parent

        parent_id = xml_util.get_id(node.parentNode)

        if parent_id != '': row[pkey_name(name_of(node.parentNode))] = parent_id

        # Insert node

        for try_num in range(2):

            try:

                xml_util.set_id(node, db_util.insert_or_get(db, table, row,

                    pkey, row_ct_ref))

                break

            except db_util.NullValueException, ex:

                if try_num > 0: raise # exception still raised after retry

                # Search for required column in ancestors and their children

                target = find_by_name(node, ptr_type(ex.col))

                if target == None: raise

                row[ex.col] = xml_util.get_id(target)

        # Insert children with fkeys to parent

        for child in children: _obj(child)

    def _field(node):

        if xml_util.is_text(node): value = xml_util.value(node)

        else:

            child = xml_util.first_elem(node)

            _obj(child)

            value = xml_util.get_id(child)

        return (field_name(name_of(node)), value)

    row_ct_ref = [0]

    _main(node)

    return row_ct_ref[0]