# This file is part of A Boneless Datastructure Language
# Copyright (C) 2020  Soni L.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import pyparsing

from abdl import exceptions
from abdl import _vm

def _build_syntax():
    # pylint: disable=protected-access
    from pyparsing import Suppress, Literal, Forward, CharsNotIn, StringEnd, Combine, Optional, Group, Word, srange, Empty

    subtree = Forward()

    skippable = Optional("?", default="")

    escape_char = Literal("%")
    str_token = Literal("'")
    re_token = Literal("/")

    unexpected_token = CharsNotIn("", exact=1).setParseAction(exceptions.PatternError._unexpected_tok)
    unexpected_end = StringEnd().setParseAction(exceptions.PatternError._unexpected_tok)

    str_literal = (Combine(Suppress(str_token)
            + (Suppress(escape_char) + (str_token | escape_char) | escape_char + CharsNotIn("", exact=1).setParseAction(exceptions.PatternError._str_escape) | CharsNotIn("%'"))[...]
            + (Suppress(str_token) | StringEnd().setParseAction(exceptions.PatternError._str_end))) + skippable)
    str_literal.setParseAction(lambda toks: [_vm.StringKey(toks)])

    re_literal = (Combine(Suppress(re_token)
            + (Suppress(escape_char) + (re_token | escape_char) | escape_char + CharsNotIn("", exact=1).setParseAction(exceptions.PatternError._re_escape) | CharsNotIn("%/"))[...]
            + (Suppress(re_token) | StringEnd().setParseAction(exceptions.PatternError._re_end))) + skippable)
    re_literal.setParseAction(lambda toks: [_vm.RegexKey(toks)])

    arrow = Literal("->")
    arrow.setParseAction(lambda: [_vm.Arrow()])

    identifier = Word(srange("[A-Za-z_]"), srange("[A-Za-z0-9_]"))
    identifier.setParseAction(lambda toks: [_vm.Ident(toks)])

    parameter = (Suppress("$") + skippable + identifier)
    parameter.setParseAction(lambda toks: [_vm.Param(toks)])

    type_ = (Suppress(":") + skippable + Suppress("$") + identifier)
    type_.setParseAction(lambda toks: [_vm.ApplyPredicate(toks)])

    # support for objects-as-keys
    keysubtree = (Suppress("[") + Group(type_[...] + subtree) + (Suppress("]") | unexpected_token | unexpected_end) + skippable)
    keysubtree.setParseAction(lambda toks: [_vm.KeySubtree(toks)])

    # represents key matching - switches from "key" to "value"
    tag = (identifier + Optional(parameter | str_literal | re_literal | keysubtree) | parameter | str_literal | re_literal | keysubtree) + type_[...] + Empty().setParseAction(lambda: [_vm.End()])

    # multiple value matching
    valuesubtree = (Suppress("(") + Group(subtree) + (Suppress(")") | unexpected_token | unexpected_end) + Optional("?", default=""))
    valuesubtree.setParseAction(lambda toks: [_vm.ValueSubtree(toks)])

    # arrow and tag, value subtree
    subtree <<= (arrow + tag)[...] + (valuesubtree + Empty().setParseAction(lambda: [_vm.End()]))[...]

    return ((subtree | unexpected_token) + StringEnd()).parseWithTabs()

BUILT_SYNTAX = _build_syntax()