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path: root/sievelib/commands.py
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# coding: utf-8

"""
SIEVE commands representation

This module contains classes that represent known commands. They all
inherit from the Command class which provides generic method for
command manipulation or parsing.

There are three command types (each one represented by a class):
 * control (ControlCommand) : Control structures are needed to allow
   for multiple and conditional actions
 * action (ActionCommand) : Actions that can be applied on emails
 * test (TestCommand) : Tests are used in conditionals to decide which
   part(s) of the conditional to execute

Finally, each known command is represented by its own class which
provides extra information such as:
 * expected arguments,
 * completion callback,
 * etc.

"""
import sys

class UnknownCommand(Exception):
    """Specific exception raised when an unknown command is encountered"""
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return "unknown command %s" % self.name

class BadArgument(Exception):
    """Specific exception raised when a bad argument is encountered"""
    def __init__(self, command, seen, expected):
        self.command = command
        self.seen = seen
        self.expected = expected

    def __str__(self):
        return "bad argument %s for command %s (%s expected)" \
            % (self.seen, self.command, self.expected)

class BadValue(Exception):
    """Specific exception raised when a bad argument value is encountered"""
    def __init__(self, argument, value):
        self.argument = argument
        self.value = value

    def __str__(self):
        return "bad value %s for argument %s" \
            % (self.value, self.argument)


# Statement elements (see RFC, section 8.3)
# They are used in different commands.
comparator = {
        "name": "comparator",
        "type": [ "tag" ],
        "values": [ ":comparator" ],
        "extra_arg": {
                "type" : "string",
                "values" : [ '"i;octet"', '"i;ascii-casemap"' ],
            },
        "required": False
    }

address_part = {
        "name": "address-part",
        "values": [ ":localpart", ":domain", ":all" ],
        "type" : [ "tag" ],
        "required" : False
    }

match_type = {
        "name": "match-type",
        "values": [ ":is", ":contains", ":matches" ],
        "type": [ "tag" ],
        "required": False
    }

namespace = {
        "name": "namespace",
        "values": [ ":personal", ":global" ],
        "type": [ "tag" ],
        "required": False
    }

class Command(object):
    """
        Generic command representation.

        A command is described as follow:

            * A name
            * A type
            * A description of supported arguments
            * Does it accept an unkwown quantity of arguments? (ex: anyof, allof)
            * Does it accept children? (ie. subcommands)
            * Is it an extension?
            * Must follow only certain commands

    """
    _type = None
    variable_args_nb = False
    accept_children = False
    must_follow = None
    is_extension = False

    def __init__(self, parent=None):
        self.parent = parent
        self.arguments = {}
        self.children = []

        self.nextargpos = 0
        self.required_args = -1
        self.rargs_cnt = 0

        # for arguments that expect an argument :p (ex: :comparator)
        self.curarg = None

        self.name = self.__class__.__name__.replace("Command", "")
        self.name = self.name.lower()

    def __repr__(self):
        return "%s (type: %s)" % (self.name, self._type)

    def tosieve(self, indentlevel=0, target=sys.stdout):
        """
            Generate the sieve syntax corresponding to this command

            Recursive method.

            :param indentlevel: current indentation level
            :param target: opened file pointer where the content will be printed
        """
        self.__print(self.name, indentlevel, nocr=True, target=target)
        if self.has_arguments():
            for arg in self.args_definition:
                if not self.arguments.has_key(arg["name"]):
                    continue
                target.write(" ")
                value = self.arguments[arg["name"]]
                if type(value) == list:
                    if self.__get_arg_type(arg["name"]) == ["testlist"]:
                        target.write("(")
                        for t in value:
                            t.tosieve(target=target)
                            if value.index(t) != len(value) - 1:
                                target.write(", ")
                        target.write(")")
                    else:
                        target.write("[" + (", ".join(map(lambda v: '"%s"' % v.strip('"'), value))) + "]")
                    continue
                if isinstance(value, Command):
                    value.tosieve(indentlevel, target=target)
                    continue

                if type(value) is unicode:
                    value = value.encode("utf-8")

                if "tag" in arg["type"] and arg.get("write_tag", False):
                    target.write("%s " % arg["values"][0])

                if "string" in arg["type"]:
                    target.write('"%s"' % value.strip('"'))
                elif arg.has_key('extra_arg') and "string" in arg['extra_arg']['type']:
                    target.write('"%s"' % value.strip('"'))
                else:
                    target.write("%s" % value)

        if not self.accept_children:
            if self.get_type() != "test":
                print >>target, ";"
            return

        if self.get_type() != "control":
            return

        print >>target, " {"

        for ch in self.children:
            ch.tosieve(indentlevel + 4, target=target)

        self.__print("}", indentlevel, target=target)

    def __print(self, data, indentlevel, nocr=False, target=sys.stdout):
        text = "%s%s" % (" " * indentlevel, data)
        if nocr:
            target.write(text)
        else:
            print >>target, text

    def __get_arg_type(self, arg):
        """
            Return the type corresponding to the given name.

            :param arg: a defined argument name
        """

        for a in self.args_definition:
            if a["name"] == arg:
                return a["type"]
        return None

    def complete_cb(self):
        """
            Completion callback

            Called when a command is considered as complete by the parser.
        """

        pass

    def get_expected_first(self):
        """
            Return the first expected token for this command
        """

        return None

    def has_arguments(self):
        return len(self.args_definition) != 0

    def dump(self, indentlevel=0, target=sys.stdout):
        """
            Display the command

            Pretty printing of this command and its eventual arguments and
            children. (recursively)

            :param indentlevel: integer that indicates indentation level to apply
        """

        self.__print(self, indentlevel, target=target)
        indentlevel += 4
        if self.has_arguments():
            for arg in self.args_definition:
                if not self.arguments.has_key(arg["name"]):
                    continue
                value = self.arguments[arg["name"]]
                if type(value) == list:
                    if self.__get_arg_type(arg["name"]) == ["testlist"]:
                        for t in value:
                            t.dump(indentlevel, target)
                    else:
                        self.__print("[" + (",".join(value)) + "]", indentlevel, target=target)
                    continue
                if isinstance(value, Command):
                    value.dump(indentlevel, target)
                    continue
                self.__print(str(value), indentlevel, target=target)
        for ch in self.children:
            ch.dump(indentlevel, target)

    def addchild(self, child):
        """
            Add a new child to the command

            A child corresponds to a command located into a block (this
            command's block). It can be either an action or a control.

            :param child: the new child
            :return: True on succes, False otherwise
        """

        if not self.accept_children:
            return False
        self.children += [child]
        return True

    def iscomplete(self):
        """
            Check if the command is complete

            Check if all required arguments have been encountered. For
            commands that allow an undefined number of arguments, this
            method always returns False.

            :return: True if command is complete, False otherwise
        """

        if self.variable_args_nb:
            return False
        if self.required_args == -1:
            self.required_args = 0
            for arg in self.args_definition:
                if arg["required"]:
                    self.required_args += 1
        return self.rargs_cnt == self.required_args

    def get_type(self):
        """
            Return the command's type
        """

        if self._type is None:
            raise NotImplemented
        return self._type

    def __is_valid_value_for_arg(self, arg, value):
        """
            Check if value is allowed for arg

            Some commands only allow a limited set of values. The method
            always returns True for methods that do not provide such a
            set.

            :param arg: the argument's name
            :param value: the value to check
            :return: True on succes, False otherwise
        """

        if not arg.has_key("values"):
            return True

        if not isinstance(value, str) and not isinstance(value, basestring):
            if arg.has_key('type') and "stringlist" in arg['type']:
                return True
            else:
                return False

        return value.lower() in arg["values"]

    def check_next_arg(self, atype, avalue, add=True):
        """
            Argument validity checking

            This method is usually used by the parser to check if detected
            argument is allowed for this command.

            We make a distinction between required and optional
            arguments. Optional (or tagged) arguments can be provided
            unordered but the required ones.

            A special handling is also for arguments that require an
            argument (example: the :comparator argument expects a string
            argument).

            The "testlist" type is checked separately as we can't know in
            advance how many arguments will be provided.

            If the argument is incorrect, the method raises the
            appropriate exception, or return False to let the parser
            handle the exception.

            :param atype: the argument's type
            :param avalue: the argument's value
            :param add: indicates if this argument should be recorded on success
            :return: True on success, False otherwise
        """

        if not self.has_arguments():
            return False

        if self.iscomplete():
            return False

        if self.curarg is not None:
            if atype == self.curarg["extra_arg"]["type"]:
                if not self.curarg["extra_arg"].has_key("values") or \
                        avalue in self.curarg["extra_arg"]["values"]:
                    if add:
                        self.arguments[self.curarg["name"]] = avalue
                    self.nextargpos += 1
                    self.curarg = None
                    return True

            raise BadValue(self.curarg["name"], avalue)

        failed = False

        for arg in self.args_definition[self.nextargpos:]:
            if self.arguments.has_key(arg["name"]):
                continue

            if arg["required"]:
                if arg["type"] == ["testlist"]:
                    if not atype == "test":
                        failed = True
                    elif add:
                        if not self.arguments.has_key(arg["name"]):
                            self.arguments[arg["name"]] = []
                        self.arguments[arg["name"]].append(avalue)
                elif atype not in arg["type"] or \
                    not self.__is_valid_value_for_arg(arg, avalue):

                    failed = True
                else:
                    self.nextargpos += 1
                    if add:
                        self.arguments[arg["name"]] = avalue

                break

            if self.__is_valid_value_for_arg(arg, avalue):
                self.arguments[arg["name"]] = avalue
                if arg.has_key('extra_arg'):
                    self.curarg = arg
                    break
                self.nextargpos += 1
                break

        if failed:
            raise BadArgument(self.name, avalue,
                              self.args_definition[self.nextargpos]["type"])
        return True

    def __getitem__(self, name):
        """
            Shorcut to access a command argument

            :param name: the argument's name
        """

        found = False
        for ad in self.args_definition:
            if ad["name"] == name:
                found = True
                break
        if not found:
            raise KeyError(name)
        if not self.arguments.has_key(name):
            raise KeyError(name)
        return self.arguments[name]

class ControlCommand(Command):
    """
        Indermediate class to represent "control" commands
    """

    _type = "control"

class RequireCommand(ControlCommand):
    """
        The 'require' command

        This class has one big difference with others as it is used to
        store loaded extension names. (The result is we can check for
        unloaded extensions during the parsing)
    """

    args_definition = [
                {
                    "name": "capabilities",
                    "type": [ "string", "stringlist" ],
                    "required": True
            }
        ]

    loaded_extensions = []

    def complete_cb(self):
        if type(self.arguments["capabilities"]) == str:
            exts = [self.arguments["capabilities"]]
        else:
            exts = self.arguments["capabilities"]
        for ext in exts:
            ext = ext.strip('"')
            if not ext in RequireCommand.loaded_extensions:
                RequireCommand.loaded_extensions += [ext]

class StopCommand(ControlCommand):
    args_definition = []

class IfCommand(ControlCommand):
    accept_children = True

    args_definition = [
            {
                    "name": "test",
                    "type": [ "test" ],
                    "required": True
                }
        ]

    def get_expected_first(self):
        return ["identifier"]

class ElsifCommand(ControlCommand):
    accept_children = True
    must_follow = ["if", "elsif"]
    args_definition = [
        {"name": "test",
         "type": [ "test" ],
         "required": True}
        ]

    def get_expected_first(self):
        return ["identifier"]

class ElseCommand(ControlCommand):
    accept_children = True
    must_follow = ["if", "elsif"]
    args_definition = []

class ActionCommand(Command):
    """Indermediate class to represent "action" commands"""
    _type = "action"

class FileintoCommand(ActionCommand):
    is_extension = True
    args_definition = [
        {"name": "mailbox",
         "type": [ "string" ],
         "required": True}
        ]

class IncludeCommand(ControlCommand):
    is_extension = True
    accept_children = False
    args_definition = [
        namespace,
        {"name": "script",
         "type": [ "string" ],
         "required": True}
        ]

class AddflagCommand(ActionCommand):
    args_definition = [
            {
                    "name": "flag",
                    "type": [ "string" ],
                    "required": True
                }
        ]

class SetflagCommand(ActionCommand):
    args_definition = [
            {
                    "name": "flag",
                    "type": [ "string" ],
                    "required": True
                }
        ]

class RedirectCommand(ActionCommand):
    is_extension = False
    args_definition = [
            {
                    "name": "copy",
                    "values": [ ":copy" ],
                    "type": [ "tag" ],
                    "required": False
                },
            {
                    "name": "address",
                    "type": [ "string", "stringlist" ],
                    "required": True
                },
        ]

class KeepCommand(ActionCommand):
    args_definition = []

class DiscardCommand(ActionCommand):
    args_definition = []

class TestCommand(Command):
    """Indermediate class to represent "test" commands"""
    _type = "test"

class AddressCommand(TestCommand):
    args_definition = [
        comparator,
        address_part,
        match_type,
        {"name": "header-list",
         "type": [ "string", "stringlist" ],
         "required": True},
        {"name": "key-list",
         "type": [ "string", "stringlist" ],
         "required": True}
        ]

class AllofCommand(TestCommand):
    accept_children = True
    variable_args_nb = True

    args_definition = [
        {"name": "tests",
         "type": [ "testlist" ],
         "required": True}
        ]

    def get_expected_first(self):
        return ["left_parenthesis"]

class AnyofCommand(TestCommand):
    accept_children = True
    variable_args_nb = True

    args_definition = [
        {"name": "tests",
         "type": [ "testlist" ],
         "required": True}
        ]

    def get_expected_first(self):
        return ["left_parenthesis"]

class EnvelopeCommand(TestCommand):
    args_definition = [
        comparator,
        address_part,
        match_type,
        {"name": "header-list",
         "type": [ "string", "stringlist" ],
         "required": True},
        {"name": "key-list",
         "type": [ "string", "stringlist" ],
         "required": True}
        ]

class ExistsCommand(TestCommand):
    args_definition = [
        {"name": "header-names",
         "type": [ "string", "stringlist" ],
         "required": True}
        ]

class TrueCommand(TestCommand):
    args_definition = []

class FalseCommand(TestCommand):
    args_definition = []

class HeaderCommand(TestCommand):
    args_definition = [
        comparator,
        match_type,
        {"name": "header-names",
         "type": [ "string", "stringlist" ],
         "required": True},
        {"name": "key-list",
         "type": [ "string", "stringlist" ],
         "required": True}
        ]

class NotCommand(TestCommand):
    accept_children = True

    args_definition = [
        {"name": "test",
         "type": [ "test" ],
         "required": True}
        ]

    def get_expected_first(self):
        return ["identifier"]

class SizeCommand(TestCommand):
    args_definition = [
        {"name": "comparator",
         "type": [ "tag" ],
         "values": [ ":over", ":under" ],
         "required": True},
        {"name": "limit",
         "type": [ "number" ],
         "required": True},
        ]

class VacationCommand(ActionCommand):
    args_definition = [
        {"name": "days",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":days" ],
          "extra_arg": {"type": "number"},
          "required": False},
        {"name": "subject",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":subject" ],
          "extra_arg": {"type": "string"},
          "required": False},
        {"name": "from",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":from" ],
          "extra_arg": {"type": "string"},
          "required": False},
        {"name": "addresses",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":addresses" ],
          "extra_arg": {"type": "stringlist"},
          "required": False},
        {"name": "handle",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":handle" ],
          "extra_arg": {"type": "string"},
          "required": False},
        {"name": "mime",
          "type": [ "tag" ],
          "write_tag": True,
          "values": [ ":mime" ],
          "required": False},
        {"name": "reason",
         "type": [ "string" ],
         "required": True},
        ]


def get_command_instance(name, parent=None, checkexists=True):
    """Try to guess and create the appropriate command instance

    Given a command name (encountered by the parser), construct the
    associated class name and, if known, return a new instance.

    If the command is not known or has not been loaded using require,
    an UnknownCommand exception is raised.

    :param name: the command's name
    :param parent: the eventual parent command
    :return: a new class instance
    """
    cname = "%sCommand" % name.lower().capitalize()
    if not globals().has_key(cname) or \
            (checkexists and globals()[cname].is_extension and \
                 not name in RequireCommand.loaded_extensions):
        raise UnknownCommand(name)
    return globals()[cname](parent)