bemaniutils/bemani/protocol/xml.py

import copy
import struct
from typing import Any, Dict, Final, Iterator, List, Optional, Tuple

from bemani.protocol.stream import InputStream
from bemani.protocol.node import Node


class XmlEncodingException(Exception):
    """
    An exception that is thrown when we encounter an error encoding to or decoding from XML.
    """


class XmlDecoder:
    """
    A hand-rolled XML parser, suitable for parsing old-style XML documents in
    game data or from legacy game traffic. I did consider using lxml and other
    data stores, but they insist on mangling data inside binary/string blobs
    making them unsuitable for a protocol with exact specifications.
    """

    def __init__(self, data: bytes, encoding: str) -> None:
        """
        Initialize the XML decoder.

        Parameters:
            data - String XML data which should be decoded into Nodes.
            encoding - The expected encoding of the XML.
        """
        self.stream = InputStream(data)
        self.root: Optional[Node] = None
        self.current: List[Node] = []
        self.encoding = encoding

    def __start_element(self, tag: bytes, attributes: Dict[str, str]) -> None:
        """
        Called when we encounter an element open tag. Also called when we encounter
        an empty element. Creates a new node with the specified name and attributes.

        Parameters:
            tag - The string tag name.
            attributes - A dictionary keyed by attribute name and whose values are the string
                         attribute values. This attribute values should already be decoded from
                         the XML's encoding.
        """
        data_type = attributes.get('__type')

        array_str = attributes.get('__count')
        if array_str is not None:
            array = True
        else:
            array = False

        if data_type is None:
            # Special case for nodes that don't have a type
            node = Node(name=tag.decode('ascii'), type=Node.NODE_TYPE_VOID)
        else:
            # Get the data value
            type_int = Node.typename_to_type(data_type)
            if type_int is None:
                raise XmlEncodingException(f'Invalid node type {data_type} for node {tag.decode("ascii")}')

            node = Node(name=tag.decode('ascii'), type=type_int, array=array)

        # Now, do the attributes
        for attr in attributes:
            if attr == '__type' or attr == '__count':
                # Skip these, handled
                continue
            else:
                node.set_attribute(attr, attributes[attr])

        self.current.append(node)

    def __end_element(self, tag: bytes) -> None:
        """
        Called when we encounter an element close tag. Also called when we encounter an empty element,
        after __start_element is called. Does bookkeeping related to element order.

        Parameters:
            tag - The string tag name.
        """
        node = self.current.pop()

        if node.name != tag.decode('ascii'):
            raise Exception(f'Logic error, expected {tag.decode("ascii")} but got {node.name}')

        if len(self.current) == 0:
            self.root = node
        else:
            parent = self.current[-1]
            parent.add_child(node)

    def __yield_values(self, text: str) -> Iterator[str]:
        value = ''

        for c in text:
            if c.isspace():
                if len(value) > 0:
                    yield value
                    value = ''
            else:
                value = value + c

        if len(value) > 0:
            yield value

    def __text(self, text: bytes) -> None:
        """
        Called when we finish parsing arbitrary non-element text. Note that the text passed in is in
        the XML document's encoding and it is this function's responsibility to decode it.

        Parameters:
            text - String text value of the node, as encoded by the XML document's encoding.
        """
        try:
            value = text.decode(self.encoding)
        except UnicodeDecodeError:
            raise XmlEncodingException('Failed to decode text node with given encoding')

        if len(self.current) > 0:
            data_type = self.current[-1].data_type
            composite = self.current[-1].is_composite
            array = self.current[-1].is_array

            if data_type == 'void':
                # We can't handle this
                return

            if data_type == 'str':
                # Do nothing, already fine
                value = value.replace('&', '&')
                value = value.replace('&lt;', '<')
                value = value.replace('&gt;', '>')
                value = value.replace('&apos;', '\'')
                value = value.replace('&quot;', '\"')
                if self.current[-1].value is None:
                    self.current[-1].set_value(value)
                else:
                    self.current[-1].set_value(self.current[-1].value + value)
            elif data_type == 'bin':
                # Convert from a hex string
                def hex_to_bin(hexval: str) -> bytes:
                    intval = int(hexval, 16)
                    return struct.pack('>B', intval)

                # Remove any spaces first
                value = ''.join([c for c in value if not c.isspace()])
                if self.current[-1].value is None:
                    self.current[-1].set_value(b''.join([hex_to_bin(value[i:(i + 2)]) for i in range(0, len(value), 2)]))
                else:
                    self.current[-1].set_value(self.current[-1].value + b''.join([hex_to_bin(value[i:(i + 2)]) for i in range(0, len(value), 2)]))
            elif data_type == 'ip4':
                # Do nothing, already fine
                self.current[-1].set_value(value)
            elif data_type == 'bool':
                def conv_bool(val: str) -> bool:
                    if val and val.lower() in ['0', 'false']:
                        return False
                    else:
                        return True

                if array or composite:
                    self.current[-1].set_value([conv_bool(v) for v in self.__yield_values(value)])
                else:
                    self.current[-1].set_value(conv_bool(value))
            elif data_type == 'float':
                if array or composite:
                    self.current[-1].set_value([float(v) for v in self.__yield_values(value)])
                else:
                    self.current[-1].set_value(float(value))
            else:
                if array or composite:
                    self.current[-1].set_value([int(v) for v in self.__yield_values(value)])
                else:
                    self.current[-1].set_value(int(value))

    def __parse_attributes(self, attributes: bytes) -> Dict[str, str]:
        """
        Given a string representing zero or more possible attributes, parse them into
        a dictionary.

        Returns:
            A dictionary keyed by the attribute name and who's values are unescaped strings.
            If no attributes exist, this returns an empty dictionary.
        """
        attr_stream = InputStream(attributes)
        parsed_attrs: Dict[str, str] = {}
        state = 'space'
        attr = b''
        val = b''

        def unescape(value: bytes) -> str:
            val = value.decode(self.encoding)
            val = val.replace('&amp;', '&')
            val = val.replace('&lt;', '<')
            val = val.replace('&gt;', '>')
            val = val.replace('&apos;', '\'')
            val = val.replace('&quot;', '\"')
            val = val.replace('&#13;', '\r')
            return val.replace('&#10;', '\n')

        while True:
            c = attr_stream.read_byte()

            if c is None:
                return parsed_attrs
            if state == 'space':
                if not c.isspace():
                    state = 'attr'
                    attr = c
            elif state == 'attr':
                if c == b'=':
                    attr = attr.strip()
                    state = 'valstart'
                else:
                    attr = attr + c
            elif state == 'valstart':
                if c == b'"':
                    state = 'valdouble'
                    val = b''
                elif c == b'\'':
                    state = 'valsingle'
                    val = b''
            elif state == 'valdouble':
                if c == b'"':
                    state = 'space'
                    parsed_attrs[attr.decode('ascii')] = unescape(val)
                else:
                    val = val + c
            elif state == 'valsingle':
                if c == b'\'':
                    state = 'space'
                    parsed_attrs[attr.decode('ascii')] = unescape(val)
                else:
                    val = val + c

    def __split_node(self, content: bytes) -> Tuple[bytes, bytes]:
        node_stream = InputStream(content)
        tag = b''
        attributes = b''
        state = "tag"

        while True:
            c = node_stream.read_byte()

            if c is None:
                break
            if state == "tag":
                if c.isspace():
                    state = "space"
                else:
                    tag = tag + c
            elif state == "space":
                if not c.isspace():
                    attributes = c
                    state = "attributes"
            elif state == "attributes":
                attributes = attributes + c

        return (tag, attributes)

    def __handle_node(self, content: bytes) -> None:
        """
        Called whenever we encounter any node type. Filters out special nodes,
        determines whether this is a start, end or empty node, and fires off
        calls to the respective __start_element and __end_element functions.

        Parameters:
            The node contents, minus the < and > characters. This will be encoded
            in the XML document's encoding.
        """
        if content[:1] == b'?' and content[-1:] == b'?':
            # Special node, parse to get the encoding.
            tag, attributes = self.__split_node(content[1:-1])
            if tag == b'xml':
                attributes_dict = self.__parse_attributes(attributes)
                if 'encoding' in attributes_dict:
                    self.encoding = attributes_dict['encoding']
            return

        if content[:1] == b'/':
            # We got an element end
            self.__end_element(content[1:])
        else:
            # We got a start element
            if content[-1:] == b'/':
                # This is an empty element
                empty = True
                content = content[:-1]
            else:
                # This node has subnodes or text
                empty = False

            tag, attributes = self.__split_node(content)
            self.__start_element(tag, self.__parse_attributes(attributes))
            if empty:
                self.__end_element(tag)

    def get_tree(self) -> Optional[Node]:
        """
        Walk the XML document and parse into nodes.

        Returns:
            A Node object representing the root of the XML document.
        """
        state = 'text'
        text = b''
        node = b''

        while True:
            c = self.stream.read_byte()

            if c is None:
                return self.root
            elif state == 'text':
                if c == b'<':
                    self.__text(text)
                    state = 'node'
                    node = b''
                else:
                    text = text + c
            elif state == 'node':
                if c == b'>':
                    self.__handle_node(node)
                    state = 'text'
                    text = b''
                else:
                    node = node + c


class XmlEncoder:
    def __init__(self, tree: Node, encoding: str) -> None:
        """
        Initialize the XML encoder.

        Parameters:
            tree - A binary blob of data to be decoded
            encoding - A string representing the text encoding for string elements. Should be either
                       'shift-jis', 'euc-jp', 'utf-8' or 'ascii'.
        """
        self.tree = tree
        self.encoding = encoding

    def get_data(self) -> bytes:
        magic = f'<?xml version="1.0" encoding="{self.encoding}"?>'.encode('ascii')
        payload = self.to_xml(self.tree)

        return magic + payload

    def to_xml(self, node: Node) -> bytes:
        """
        Convert this node, attributes and all children to an XML-like representation of the tree.

        Parameters:
            node: A Node representing the root of the tree to be encoded.

        Returns:
            Bytes representing the XML-like data for this node and all children.
        """
        attrs_dict = copy.deepcopy(node.attributes)
        order = sorted(attrs_dict.keys())
        if node.data_length != 0:
            # Represent type and length
            if node.is_array:
                if node.value is None:
                    attrs_dict['__count'] = '0'
                else:
                    attrs_dict['__count'] = str(len(node.value))
                order.insert(0, '__count')
            attrs_dict['__type'] = node.data_type
            order.insert(0, '__type')

        def escape(val: Any, attr: bool=False) -> bytes:
            if isinstance(val, str):
                val = val.replace('&', '&amp;')
                val = val.replace('<', '&lt;')
                val = val.replace('>', '&gt;')
                val = val.replace('\'', '&apos;')
                val = val.replace('\"', '&quot;')
                if attr:
                    val = val.replace('\r', '&#13;')
                    val = val.replace('\n', '&#10;')

                return val.encode(self.encoding)
            else:
                return str(val).encode('ascii')

        if attrs_dict:
            attrs = b' ' + b' '.join([b''.join([attr.encode('ascii'), b'="', escape(attrs_dict[attr], attr=True), b'"']) for attr in order])
        else:
            attrs = b''

        if node.children:
            # Has children nodes
            children = [self.to_xml(child) for child in node.children]
            string = b''.join([
                b'<',
                node.name.encode('ascii'),
                attrs,
                b'>',
                b''.join(children),
                b'</',
                node.name.encode('ascii'),
                b'>',
            ])
        else:
            # Doesn't have children nodes
            if node.data_length == 0:
                # Void node
                string = b''.join([
                    b'<',
                    node.name.encode('ascii'),
                    attrs,
                    b'/>',
                ])
            else:
                # Node with values
                if node.is_array or node.is_composite:
                    if node.value is None:
                        vals = ''
                    else:
                        if node.data_type == 'bool':
                            vals = ' '.join([('1' if val else '0') for val in node.value])
                        else:
                            vals = ' '.join([str(val) for val in node.value])
                    binary = vals.encode('ascii')
                elif node.data_type == 'str':
                    binary = escape(node.value)
                elif node.data_type == 'bool':
                    binary = b'1' if node.value else b'0'
                elif node.data_type == 'ip4':
                    vals = '.'.join([str(val) for val in node.value])
                    binary = vals.encode('ascii')
                elif node.data_type == 'bin':
                    # Convert to a hex string
                    def bin_to_hex(binary: int) -> str:
                        val = hex(binary)[2:]
                        while len(val) < 2:
                            val = '0' + val
                        return val

                    vals = ''.join([bin_to_hex(v) for v in node.value])
                    binary = vals.encode('ascii')
                else:
                    vals = str(node.value)
                    binary = vals.encode('ascii')

                string = b''.join([
                    b'<',
                    node.name.encode('ascii'),
                    attrs,
                    b'>',
                    binary,
                    b'</',
                    node.name.encode('ascii'),
                    b'>',
                ])

        return string


class XmlEncoding:
    """
    Wrapper class representing an XML encoding.
    """
    # The string values should match the constants in EAmuseProtocol.
    # I have no better way to link these than to write this comment,
    # as otherwise we would have a circular dependency.
    ACCEPTED_ENCODINGS: Final[List[str]] = ['shift-jis', 'euc-jp', 'utf-8', 'ascii']

    def __init__(self) -> None:
        """
        Initialize the encoding object.
        """
        self.encoding: Optional[str] = None

    def __fix_encoding(self, encoding: str) -> str:
        """
        Given an encoding, try to normalize it, looking for specific ways that
        older games might send it back.

        Parameters:
            encoding - The encoding we want to normalize.

        Returns:
            A new encoding string that is equivalent but normalized.
        """
        encoding = encoding.lower()
        encoding = encoding.replace('_', '-')
        return encoding

    def decode(self, data: bytes, skip_on_exceptions: bool=False) -> Optional[Node]:
        """
        Given a data blob, decode the data with the current encoding. Will set
        the class property value 'encoding' to the encoding used on the last
        decode.

        Parameters:
            data - Blob of text representing the data to decode.

        Returns:
            Node object representing the root of the decoded tree, or None
            if we couldn't decode the object for some reason.
        """
        # Always assume this, unless we get told otherwise in the XML
        self.encoding = 'shift-jis'

        # Decode property/value
        try:
            xml = XmlDecoder(data, self.encoding)
            tree = xml.get_tree()
            self.encoding = xml.encoding
            return tree
        except XmlEncodingException:
            if skip_on_exceptions:
                return None
            else:
                raise

    def encode(self, tree: Node, encoding: Optional[str]=None) -> bytes:
        """
        Given a tree of Node objects, encode the data with the current encoding.

        Parameters:
            tree - Node tree representing the data to encode
            encoding - The text encoding to use. If None, will try to use the encoding from
                       the last successful decode

        Returns:
            String blob representing encoded data as XML.
        """
        # Ensure we got the right encoding
        if encoding is None:
            encoding = self.encoding
        if encoding is None:
            raise XmlEncodingException('Unknown encoding')

        encoding = self.__fix_encoding(encoding)
        if encoding not in XmlEncoding.ACCEPTED_ENCODINGS:
            # XML pages only support a few encodings.
            raise XmlEncodingException(f"Invalid text encoding {encoding}")

        xml = XmlEncoder(tree, encoding)
        return xml.get_data()