#!/usr/bin/env python

"""

Attribute access plan translation.

Copyright (C) 2014-2018, 2023 Paul Boddie <paul@boddie.org.uk>

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 3 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, see <http://www.gnu.org/licenses/>.

"""

from encoders import encode_access_location

class AccessPlan:

    "An attribute access plan."

    def __init__(self, name, test, test_type, base, traversed, traversal_modes,

                 remaining, context, context_test, first_method, final_method,

                 origin, accessor_kinds):

        "Initialise the plan."

        # With instance attribute initialisers, the assignment below would be

        # generated automatically.

        (

            self.name, self.test, self.test_type, self.base,

            self.traversed, self.traversal_modes, self.remaining,

            self.context, self.context_test,

            self.first_method, self.final_method,

            self.origin, self.accessor_kinds) = (

            name, test, test_type, base,

            traversed, traversal_modes, remaining,

            context, context_test,

            first_method, final_method,

            origin, accessor_kinds)

        # Define the first attribute access and subsequent accesses.

        self.first_attrname = None

        self.traversed_attrnames = traversed

        self.traversed_attrname_modes = traversal_modes

        self.remaining_attrnames = remaining

        if traversed:

            self.first_attrname = traversed[0]

            self.traversed_attrnames = traversed[1:]

            self.traversed_attrname_modes = traversal_modes[1:]

        elif remaining:

            self.first_attrname = remaining[0]

            self.remaining_attrnames = remaining[1:]

    def access_first_attribute(self):

        "Return whether the first attribute is to be accessed."

        return self.final_method in ("access", "access-invoke", "assign") or \

            self.all_subsequent_attributes()

    def assigning_first_attribute(self):

        "Return whether the first attribute access involves assignment."

        return not self.all_subsequent_attributes() and self.final_method == "assign"

    def get_first_attribute_name(self):

        "Return any first attribute name to be used in an initial access."

        return self.first_attrname

    def all_subsequent_attributes(self):

        "Return all subsequent attribute names involved in accesses."

        return self.traversed_attrnames + self.remaining_attrnames

    def attribute_traversals(self):

        "Return a collection of (attribute name, traversal mode) tuples."

        return zip(self.traversed_attrnames, self.traversed_attrname_modes)

    def stored_accessor(self):

        "Return the variable used to obtain the accessor."

        return self.assigning_first_attribute() and "<target_accessor>" or "<accessor>"

    def stored_accessor_modifier(self):

        "Return the variable used to set the accessor."

        return self.assigning_first_attribute() and "<set_target_accessor>" or "<set_accessor>"

    def get_original_accessor(self):

        "Return the original accessor details."

        # Identify any static original accessor.

        if self.base:

            return self.base

        # Employ names as contexts unless the context needs testing and

        # potentially updating. In such cases, temporary context storage is

        # used instead.

        elif self.name and not (self.context_test == "test" and

            self.final_method in ("access-invoke", "static-invoke")):

            return "<name>"

        # Use a generic placeholder representing the access expression in

        # the general case.

        else:

            return "<expr>"

    def get_instructions(self):

        "Return a list of instructions corresponding to the plan."

        # Emit instructions by appending them to a list.

        instructions = []

        emit = instructions.append

        # Set up any initial instructions.

        accessor, context = self.process_initialisation(emit)

        # Apply any test.

        if self.test[0] == "test":

            test_accessor = accessor = ("__%s_%s_%s" % self.test, accessor, self.test_type)

        else:

            test_accessor = None

        # Perform the first or final access.

        # The access only needs performing if the resulting accessor is used.

        accessor = self.process_first_attribute(accessor, emit)

        # Perform accesses for the traversed and remaining attributes.

        accessor, context = self.process_traversed_attributes(accessor, context, emit)

        accessor, context = self.process_remaining_attributes(accessor, context, emit)

        # Make any accessor test available if not emitted.

        test_accessor = not instructions and test_accessor or None

        # Perform the access on the actual target.

        accessor = self.process_attribute_access(accessor, context, test_accessor, emit)

        # Produce an advisory instruction regarding the context.

        self.process_context_identity(context, emit)

        # Produce an advisory instruction regarding the final attribute.

        if self.origin:

            emit(("<final_identity>", self.origin))

        return instructions

    def process_initialisation(self, emit):

        """

        Use 'emit' to generate instructions for any initialisation of attribute

        access. Return the potentially revised accessor and context indicators.

        """

        # Identify any static original accessor.

        original_accessor = self.get_original_accessor()

        # Determine whether the first access involves assignment.

        set_accessor = self.stored_accessor_modifier()

        stored_accessor = self.stored_accessor()

        # Set the context if already available.

        context = None

        if self.context == "base":

            accessor = context = (self.base,)

        elif self.context == "original-accessor":

            # Prevent re-evaluation of any dynamic expression by storing it.

            if original_accessor == "<expr>":

                if self.final_method in ("access-invoke", "static-invoke"):

                    emit(("<set_context>", original_accessor))

                    accessor = context = ("<context>",)

                else:

                    emit((set_accessor, original_accessor))

                    accessor = context = (stored_accessor,)

            else:

                accessor = context = (original_accessor,)

        # Assigning does not set the context.

        elif self.context in ("final-accessor", "unset") and self.access_first_attribute():

            # Prevent re-evaluation of any dynamic expression by storing it.

            if original_accessor == "<expr>":

                emit((set_accessor, original_accessor))

                accessor = (stored_accessor,)

            else:

                accessor = (original_accessor,)

        else:

            accessor = None

        return accessor, context

    def process_first_attribute(self, accessor, emit):

        """

        Using 'accessor', use 'emit' to generate instructions for any first

        attribute access. Return the potentially revised accessor.

        """

        if self.access_first_attribute():

            attrname = self.get_first_attribute_name()

            assigning = self.assigning_first_attribute()

            if self.first_method == "relative-class":

                if assigning:

                    emit(("__store_via_class", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__load_via_class", accessor, attrname)

            elif self.first_method == "relative-object":

                if assigning:

                    emit(("__store_via_object", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__load_via_object", accessor, attrname)

            elif self.first_method == "relative-object-class":

                if assigning:

                    emit(("__get_class_and_store", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__get_class_and_load", accessor, attrname)

            elif self.first_method == "check-class":

                if assigning:

                    emit(("__check_and_store_via_class", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__check_and_load_via_class", accessor, attrname)

            elif self.first_method == "check-object":

                if assigning:

                    emit(("__check_and_store_via_object", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__check_and_load_via_object", accessor, attrname)

            elif self.first_method == "check-object-class":

                if assigning:

                    emit(("__check_and_store_via_any", accessor, attrname, "<assexpr>"))

                else:

                    accessor = ("__check_and_load_via_any", accessor, attrname)

        return accessor

    def process_traversed_attributes(self, accessor, context, emit):

        """

        Using 'accessor' and 'context', use 'emit' to generate instructions

        for the traversed attribute accesses. Return the potentially revised

        accessor and context indicators.

        """

        # Traverse attributes using the accessor.

        num_remaining = len(self.all_subsequent_attributes())

        if self.traversed_attrnames:

            for attrname, traversal_mode in self.attribute_traversals():

                assigning = num_remaining == 1 and self.final_method == "assign"

                # Set the context, if appropriate.

                if num_remaining == 1 and self.final_method != "assign" and self.context == "final-accessor":

                    # Invoked attributes employ a separate context accessed

                    # during invocation.

                    if self.final_method in ("access-invoke", "static-invoke"):

                        emit(("<set_context>", accessor))

                        accessor = context = "<context>"

                    # A private context within the access is otherwise

                    # retained.

                    else:

                        emit(("<set_private_context>", accessor))

                        accessor = context = "<private_context>"

                # Perform the access only if not achieved directly.

                if num_remaining > 1 or self.final_method in ("access", "access-invoke", "assign"):

                    if traversal_mode == "class":

                        if assigning:

                            emit(("__store_via_class", accessor, attrname, "<assexpr>"))

                        else:

                            accessor = ("__load_via_class", accessor, attrname)

                    else:

                        if assigning:

                            emit(("__store_via_object", accessor, attrname, "<assexpr>"))

                        else:

                            accessor = ("__load_via_object", accessor, attrname)

                num_remaining -= 1

        return accessor, context

    def process_remaining_attributes(self, accessor, context, emit):

        """

        Using 'accessor' and 'context', use 'emit' to generate instructions

        for the remaining attribute accesses. Return the potentially revised

        accessor and context indicators.

        """

        remaining = self.remaining_attrnames

        if remaining:

            num_remaining = len(remaining)

            for attrname in remaining:

                assigning = num_remaining == 1 and self.final_method == "assign"

                # Set the context, if appropriate.

                if num_remaining == 1 and self.final_method != "assign" and self.context == "final-accessor":

                    # Invoked attributes employ a separate context accessed

                    # during invocation.

                    if self.final_method in ("access-invoke", "static-invoke"):

                        emit(("<set_context>", accessor))

                        accessor = context = "<context>"

                    # A private context within the access is otherwise

                    # retained.

                    else:

                        emit(("<set_private_context>", accessor))

                        accessor = context = "<private_context>"

                # Perform the access only if not achieved directly.

                if num_remaining > 1 or self.final_method in ("access", "access-invoke", "assign"):

                    # Constrain instructions involving certain special

                    # attribute names.

                    to_search = attrname == "__data__" and "object" or "any"

                    if assigning:

                        emit(("__check_and_store_via_%s" % to_search, accessor, attrname, "<assexpr>"))

                    else:

                        accessor = ("__check_and_load_via_%s" % to_search, accessor, attrname)

                num_remaining -= 1

        return accessor, context

    def process_attribute_access(self, accessor, context, test_accessor, emit):

        """

        Using 'accessor','context' and any 'test_accessor' operation, use 'emit'

        to generate instructions for the final attribute access. Return the

        potentially revised accessor.

        """

        # Define or emit the means of accessing the actual target.

        if self.final_method in ("static", "static-assign", "static-invoke"):

            if test_accessor:

                emit(test_accessor)

            # Assignments to known attributes.

            if self.final_method == "static-assign":

                parent, attrname = self.origin.rsplit(".", 1)

                emit(("__store_via_object", parent, attrname, "<assexpr>"))

            # Invoked attributes employ a separate context.

            elif self.final_method in ("static", "static-invoke"):

                accessor = ("__load_static_ignore", self.origin)

        # Wrap accesses in context operations.

        if self.context_test == "test":

            # Test and combine the context with static attribute details.

            if self.final_method == "static":

                emit(("__load_static_test", context, self.origin))

            # Test the context, storing it separately if required for the

            # immediately invoked static attribute.

            elif self.final_method == "static-invoke":

                emit(("<test_context_static>", context, self.origin))

            # Test the context, storing it separately if required for an

            # immediately invoked attribute.

            elif self.final_method == "access-invoke":

                emit(("<test_context_revert>", context, accessor))

            # Test the context and update the attribute details if

            # appropriate.

            else:

                emit(("__test_context", context, accessor))

        elif self.context_test == "replace":

            # Produce an object with updated context.

            if self.final_method == "static":

                emit(("__load_static_replace", context, self.origin))

            # Omit the context update operation where the target is static

            # and the context is recorded separately.

            elif self.final_method == "static-invoke":

                pass

            # If a separate context is used for an immediate invocation,

            # produce the attribute details unchanged.

            elif self.final_method == "access-invoke":

                emit(accessor)

            # Update the context in the attribute details.

            else:

                emit(("__update_context", context, accessor))

        # Omit the accessor for assignments and for invocations of static

        # targets. Otherwise, emit the accessor which may involve the

        # invocation of a test.

        elif self.final_method not in ("assign", "static-assign", "static-invoke"):

            emit(accessor)

        return accessor

    def process_context_identity(self, context, emit):

        """

        Using 'context', use 'emit' to generate instructions to test the context

        identity.

        """

        if context:

            # Only verify the context for invocation purposes if a suitable

            # test has been performed.

            if self.context_test in ("ignore", "replace") or \

               self.final_method in ("access-invoke", "static-invoke"):

                emit(("<context_identity_verified>", context))

            else:

                emit(("<context_identity>", context))

    def write(self, f, location):

        "Write the plan to file 'f' with the given 'location' information."

        print >>f, encode_access_location(location), \

                   self.name or "{}", \

                   self.test and "-".join(self.test) or "{}", \

                   self.test_type or "{}", \

                   self.base or "{}", \

                   ".".join(self.traversed_attrnames) or "{}", \

                   ".".join(self.traversed_attrname_modes) or "{}", \

                   ".".join(self.remaining_attrnames) or "{}", \

                   self.context, self.context_test, \

                   self.first_method, self.final_method, self.origin or "{}", \

                   ",".join(self.accessor_kinds)

# vim: tabstop=4 expandtab shiftwidth=4