# 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

import abdl.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="")

    str_literal = (Combine(Suppress("'")
            + (Suppress("%") + ("'" | "%") | Literal("%") + (CharsNotIn("") | StringEnd()).setParseAction(abdl.exceptions.PatternError._str_escape) | CharsNotIn("%'"))[...]
            + (Suppress("'") | StringEnd().setParseAction(abdl.exceptions.PatternError._str_end))) + skippable)
    str_literal.setParseAction(lambda toks: [_vm.StringKey(toks)])

    re_literal = (Combine(Suppress("/")
            + (Suppress("%") + ("/" | "%") | Literal("%") + (CharsNotIn("") | StringEnd()).setParseAction(abdl.exceptions.PatternError._re_escape) | CharsNotIn("%/"))[...]
            + (Suppress("/") | StringEnd().setParseAction(abdl.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 + Optional(Suppress("$")) + identifier)
    type_.setParseAction(lambda toks: [_vm.ApplyPredicate(toks)])

    # support for objects-as-keys
    keysubtree = (Suppress("[")
            + Group(type_[...] + subtree)
            + (Suppress("]") | (CharsNotIn("") | StringEnd()).setParseAction(abdl.exceptions.PatternError._unexpected_tok)) + 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(")") | CharsNotIn("").setParseAction(abdl.exceptions.PatternError._unexpected_tok) | StringEnd().setParseAction(abdl.exceptions.PatternError._unexpected_tok)) + 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 | CharsNotIn("").setParseAction(abdl.exceptions.PatternError._unexpected_tok)) + StringEnd()).parseWithTabs()

BUILT_SYNTAX = _build_syntax()