# ast_utils.py
#
# Copyright 2021 James Westman <james@jwestman.net>
#
# This file is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation; either version 3 of the
# License, or (at your option) any later version.
#
# This file 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# SPDX-License-Identifier: LGPL-3.0-or-later

import typing as T
from collections import ChainMap, defaultdict

from . import ast
from .errors import *
from .lsp_utils import SemanticToken
from .utils import lazy_prop
from .xml_emitter import XmlEmitter


class Children:
    """ Allows accessing children by type using array syntax. """
    def __init__(self, children):
        self._children = children
    def __iter__(self):
        return iter(self._children)
    def __getitem__(self, key):
        return [child for child in self._children if isinstance(child, key)]


class AstNode:
    """ Base class for nodes in the abstract syntax tree. """

    completers: T.List = []

    def __init__(self, group, children, tokens, incomplete=False):
        self.group = group
        self.children = Children(children)
        self.tokens = ChainMap(tokens, defaultdict(lambda: None))
        self.incomplete = incomplete

        self.parent = None
        for child in self.children:
            child.parent = self

    def __init_subclass__(cls):
        cls.completers = []
        cls.validators = [getattr(cls, f) for f in dir(cls) if hasattr(getattr(cls, f), "_validator")]


    @property
    def root(self):
        if self.parent is None:
            return self
        else:
            return self.parent.root

    def parent_by_type(self, type):
        if self.parent is None:
            return None
        elif isinstance(self.parent, type):
            return self.parent
        else:
            return self.parent.parent_by_type(type)

    def validate_parent_type(self, ns: str, name: str, err_msg: str):
        parent = self.root.gir.get_type(name, ns)
        container_type = self.parent_by_type(ast.Object).gir_class
        if container_type and not container_type.assignable_to(parent):
            raise CompileError(f"{container_type.full_name} is not a {parent.full_name}, so it doesn't have {err_msg}")

    @lazy_prop
    def errors(self):
        return list(self._get_errors())

    def _get_errors(self):
        for validator in self.validators:
            try:
                validator(self)
            except AlreadyCaughtError:
                pass
            except CompileError as e:
                yield e

        for child in self.children:
            yield from child._get_errors()

    def _attrs_by_type(self, attr_type):
        for name in dir(type(self)):
            item = getattr(type(self), name)
            if isinstance(item, attr_type):
                yield name, item

    def generate(self) -> str:
        """ Generates an XML string from the node. """
        xml = XmlEmitter()
        self.emit_xml(xml)
        return xml.result

    def emit_xml(self, xml: XmlEmitter):
        """ Emits the XML representation of this AST node to the XmlEmitter. """
        raise NotImplementedError()

    def get_docs(self, idx: int) -> T.Optional[str]:
        for name, attr in self._attrs_by_type(Docs):
            if attr.token_name:
                token = self.group.tokens.get(attr.token_name)
                if token and token.start <= idx < token.end:
                    return getattr(self, name)
            else:
                return getattr(self, name)

        for child in self.children:
            if child.group.start <= idx < child.group.end:
                docs = child.get_docs(idx)
                if docs is not None:
                    return docs

        return None

    def get_semantic_tokens(self) -> T.Iterator[SemanticToken]:
        for child in self.children:
            yield from child.get_semantic_tokens()


    def iterate_children_recursive(self) -> T.Iterator["AstNode"]:
        yield self
        for child in self.children:
            yield from child.iterate_children_recursive()


def validate(token_name=None, end_token_name=None, skip_incomplete=False):
    """ Decorator for functions that validate an AST node. Exceptions raised
    during validation are marked with range information from the tokens. Also
    creates a cached property out of the function. """

    def decorator(func):
        def inner(self):
            if skip_incomplete and self.incomplete:
                return

            try:
                func(self)
            except CompileError as e:
                # If the node is only partially complete, then an error must
                # have already been reported at the parsing stage
                if self.incomplete:
                    return

                # This mess of code sets the error's start and end positions
                # from the tokens passed to the decorator, if they have not
                # already been set
                if e.start is None:
                    if token := self.group.tokens.get(token_name):
                        e.start = token.start
                    else:
                        e.start = self.group.start

                if e.end is None:
                    if token := self.group.tokens.get(end_token_name):
                        e.end = token.end
                    elif token := self.group.tokens.get(token_name):
                        e.end = token.end
                    else:
                        e.end = self.group.end

                # Re-raise the exception
                raise e

        inner._validator = True
        return inner

    return decorator


class Docs:
    def __init__(self, func, token_name=None):
        self.func = func
        self.token_name = token_name

    def __get__(self, instance, owner):
        if instance is None:
            return self
        return self.func(instance)


def docs(*args, **kwargs):
    """ Decorator for functions that return documentation for tokens. """

    def decorator(func):
        return Docs(func, *args, **kwargs)

    return decorator