#------------------------------------------------------------------------------
# pycparser: c_parser.py
#
# CParser class: Parser and AST builder for the C language
#
# Eli Bendersky [http://eli.thegreenplace.net]
# License: BSD
#------------------------------------------------------------------------------
import re

from .ply import yacc

from . import c_ast
from .c_lexer import CLexer
from .plyparser import PLYParser, Coord, ParseError, parameterized, template
from .ast_transforms import fix_switch_cases


@template
class CParser(PLYParser):
    def __init__(
            self,
            lex_optimize=True,
            lexer=CLexer,
            lextab='pycparser.lextab',
            yacc_optimize=True,
            yacctab='pycparser.yacctab',
            yacc_debug=False,
            taboutputdir=''):
        """ Create a new CParser.

            Some arguments for controlling the debug/optimization
            level of the parser are provided. The defaults are
            tuned for release/performance mode.
            The simple rules for using them are:
            *) When tweaking CParser/CLexer, set these to False
            *) When releasing a stable parser, set to True

            lex_optimize:
                Set to False when you're modifying the lexer.
                Otherwise, changes in the lexer won't be used, if
                some lextab.py file exists.
                When releasing with a stable lexer, set to True
                to save the re-generation of the lexer table on
                each run.

            lexer:
                Set this parameter to define the lexer to use if
                you're not using the default CLexer.

            lextab:
                Points to the lex table that's used for optimized
                mode. Only if you're modifying the lexer and want
                some tests to avoid re-generating the table, make
                this point to a local lex table file (that's been
                earlier generated with lex_optimize=True)

            yacc_optimize:
                Set to False when you're modifying the parser.
                Otherwise, changes in the parser won't be used, if
                some parsetab.py file exists.
                When releasing with a stable parser, set to True
                to save the re-generation of the parser table on
                each run.

            yacctab:
                Points to the yacc table that's used for optimized
                mode. Only if you're modifying the parser, make
                this point to a local yacc table file

            yacc_debug:
                Generate a parser.out file that explains how yacc
                built the parsing table from the grammar.

            taboutputdir:
                Set this parameter to control the location of generated
                lextab and yacctab files.
        """
        self.clex = lexer(
            error_func=self._lex_error_func,
            on_lbrace_func=self._lex_on_lbrace_func,
            on_rbrace_func=self._lex_on_rbrace_func,
            type_lookup_func=self._lex_type_lookup_func)

        self.clex.build(
            optimize=lex_optimize,
            lextab=lextab,
            outputdir=taboutputdir)
        self.tokens = self.clex.tokens

        rules_with_opt = [
            'abstract_declarator',
            'assignment_expression',
            'declaration_list',
            'declaration_specifiers_no_type',
            'designation',
            'expression',
            'identifier_list',
            'init_declarator_list',
            'id_init_declarator_list',
            'initializer_list',
            'parameter_type_list',
            'block_item_list',
            'type_qualifier_list',
            'struct_declarator_list'
        ]

        for rule in rules_with_opt:
            self._create_opt_rule(rule)

        self.cparser = yacc.yacc(
            module=self,
            start='translation_unit_or_empty',
            debug=yacc_debug,
            optimize=yacc_optimize,
            tabmodule=yacctab,
            outputdir=taboutputdir)

        # Stack of scopes for keeping track of symbols. _scope_stack[-1] is
        # the current (topmost) scope. Each scope is a dictionary that
        # specifies whether a name is a type. If _scope_stack[n][name] is
        # True, 'name' is currently a type in the scope. If it's False,
        # 'name' is used in the scope but not as a type (for instance, if we
        # saw: int name;
        # If 'name' is not a key in _scope_stack[n] then 'name' was not defined
        # in this scope at all.
        self._scope_stack = [dict()]

        # Keeps track of the last token given to yacc (the lookahead token)
        self._last_yielded_token = None

    def parse(self, text, filename='', debuglevel=0):
        """ Parses C code and returns an AST.

            text:
                A string containing the C source code

            filename:
                Name of the file being parsed (for meaningful
                error messages)

            debuglevel:
                Debug level to yacc
        """
        self.clex.filename = filename
        self.clex.reset_lineno()
        self._scope_stack = [dict()]
        self._last_yielded_token = None
        return self.cparser.parse(
                input=text,
                lexer=self.clex,
                debug=debuglevel)

    ######################--   PRIVATE   --######################

    def _push_scope(self):
        self._scope_stack.append(dict())

    def _pop_scope(self):
        assert len(self._scope_stack) > 1
        self._scope_stack.pop()

    def _add_typedef_name(self, name, coord):
        """ Add a new typedef name (ie a TYPEID) to the current scope
        """
        if not self._scope_stack[-1].get(name, True):
            self._parse_error(
                "Typedef %r previously declared as non-typedef "
                "in this scope" % name, coord)
        self._scope_stack[-1][name] = True

    def _add_identifier(self, name, coord):
        """ Add a new object, function, or enum member name (ie an ID) to the
            current scope
        """
        if self._scope_stack[-1].get(name, False):
            self._parse_error(
                "Non-typedef %r previously declared as typedef "
                "in this scope" % name, coord)
        self._scope_stack[-1][name] = False

    def _is_type_in_scope(self, name):
        """ Is *name* a typedef-name in the current scope?
        """
        for scope in reversed(self._scope_stack):
            # If name is an identifier in this scope it shadows typedefs in
            # higher scopes.
            in_scope = scope.get(name)
            if in_scope is not None: return in_scope
        return False

    def _lex_error_func(self, msg, line, column):
        self._parse_error(msg, self._coord(line, column))

    def _lex_on_lbrace_func(self):
        self._push_scope()

    def _lex_on_rbrace_func(self):
        self._pop_scope()

    def _lex_type_lookup_func(self, name):
        """ Looks up types that were previously defined with
            typedef.
            Passed to the lexer for recognizing identifiers that
            are types.
        """
        is_type = self._is_type_in_scope(name)
        return is_type

    def _get_yacc_lookahead_token(self):
        """ We need access to yacc's lookahead token in certain cases.
            This is the last token yacc requested from the lexer, so we
            ask the lexer.
        """
        return self.clex.last_token

    # To understand what's going on here, read sections A.8.5 and
    # A.8.6 of K&R2 very carefully.
    #
    # A C type consists of a basic type declaration, with a list
    # of modifiers. For example:
    #
    # int *c[5];
    #
    # The basic declaration here is 'int c', and the pointer and
    # the array are the modifiers.
    #
    # Basic declarations are represented by TypeDecl (from module c_ast) and the
    # modifiers are FuncDecl, PtrDecl and ArrayDecl.
    #
    # The standard states that whenever a new modifier is parsed, it should be
    # added to the end of the list of modifiers. For example:
    #
    # K&R2 A.8.6.2: Array Declarators
    #
    # In a declaration T D where D has the form
    #   D1 [constant-expression-opt]
    # and the type of the identifier in the declaration T D1 is
    # "type-modifier T", the type of the
    # identifier of D is "type-modifier array of T"
    #
    # This is what this method does. The declarator it receives
    # can be a list of declarators ending with TypeDecl. It
    # tacks the modifier to the end of this list, just before
    # the TypeDecl.
    #
    # Additionally, the modifier may be a list itself. This is
    # useful for pointers, that can come as a chain from the rule
    # p_pointer. In this case, the whole modifier list is spliced
    # into the new location.
    def _type_modify_decl(self, decl, modifier):
        """ Tacks a type modifier on a declarator, and returns
            the modified declarator.

            Note: the declarator and modifier may be modified
        """
        #~ print '****'
        #~ decl.show(offset=3)
        #~ modifier.show(offset=3)
        #~ print '****'

        modifier_head = modifier
        modifier_tail = modifier

        # The modifier may be a nested list. Reach its tail.
        #
        while modifier_tail.type:
            modifier_tail = modifier_tail.type

        # If the decl is a basic type, just tack the modifier onto
        # it
        #
        if isinstance(decl, c_ast.TypeDecl):
            modifier_tail.type = decl
            return modifier
        else:
            # Otherwise, the decl is a list of modifiers. Reach
            # its tail and splice the modifier onto the tail,
            # pointing to the underlying basic type.
            #
            decl_tail = decl

            while not isinstance(decl_tail.type, c_ast.TypeDecl):
                decl_tail = decl_tail.type

            modifier_tail.type = decl_tail.type
            decl_tail.type = modifier_head
            return decl

    # Due to the order in which declarators are constructed,
    # they have to be fixed in order to look like a normal AST.
    #
    # When a declaration arrives from syntax construction, it has
    # these problems:
    # * The innermost TypeDecl has no type (because the basic
    #   type is only known at the uppermost declaration level)
    # * The declaration has no variable name, since that is saved
    #   in the innermost TypeDecl
    # * The typename of the declaration is a list of type
    #   specifiers, and not a node. Here, basic identifier types
    #   should be separated from more complex types like enums
    #   and structs.
    #
    # This method fixes these problems.
    #
    def _fix_decl_name_type(self, decl, typename):
        """ Fixes a declaration. Modifies decl.
        """
        # Reach the underlying basic type
        #
        type = decl
        while not isinstance(type, c_ast.TypeDecl):
            type = type.type

        decl.name = type.declname
        type.quals = decl.quals

        # The typename is a list of types. If any type in this
        # list isn't an IdentifierType, it must be the only
        # type in the list (it's illegal to declare "int enum ..")
        # If all the types are basic, they're collected in the
        # IdentifierType holder.
        #
        for tn in typename:
            if not isinstance(tn, c_ast.IdentifierType):
                if len(typename) > 1:
                    self._parse_error(
                        "Invalid multiple types specified", tn.coord)
                else:
                    type.type = tn
                    return decl

        if not typename:
            # Functions default to returning int
            #
            if not isinstance(decl.type, c_ast.FuncDecl):
                self._parse_error(
                        "Missing type in declaration", decl.coord)
            type.type = c_ast.IdentifierType(
                    ['int'],
                    coord=decl.coord)
        else:
            # At this point, we know that typename is a list of IdentifierType
            # nodes. Concatenate all the names into a single list.
            #