image-match/python/py/Lib/site-packages/lark/parsers/lalr_parser_state.py

from copy import deepcopy, copy
from typing import Dict, Any, Generic, List
from ..lexer import Token, LexerThread
from ..common import ParserCallbacks

from .lalr_analysis import Shift, ParseTableBase, StateT
from lark.exceptions import UnexpectedToken

###{standalone

class ParseConf(Generic[StateT]):
    __slots__ = 'parse_table', 'callbacks', 'start', 'start_state', 'end_state', 'states'

    parse_table: ParseTableBase[StateT]
    callbacks: ParserCallbacks
    start: str

    start_state: StateT
    end_state: StateT
    states: Dict[StateT, Dict[str, tuple]]

    def __init__(self, parse_table: ParseTableBase[StateT], callbacks: ParserCallbacks, start: str):
        self.parse_table = parse_table

        self.start_state = self.parse_table.start_states[start]
        self.end_state = self.parse_table.end_states[start]
        self.states = self.parse_table.states

        self.callbacks = callbacks
        self.start = start

class ParserState(Generic[StateT]):
    __slots__ = 'parse_conf', 'lexer', 'state_stack', 'value_stack'

    parse_conf: ParseConf[StateT]
    lexer: LexerThread
    state_stack: List[StateT]
    value_stack: list

    def __init__(self, parse_conf: ParseConf[StateT], lexer: LexerThread, state_stack=None, value_stack=None):
        self.parse_conf = parse_conf
        self.lexer = lexer
        self.state_stack = state_stack or [self.parse_conf.start_state]
        self.value_stack = value_stack or []

    @property
    def position(self) -> StateT:
        return self.state_stack[-1]

    # Necessary for match_examples() to work
    def __eq__(self, other) -> bool:
        if not isinstance(other, ParserState):
            return NotImplemented
        return len(self.state_stack) == len(other.state_stack) and self.position == other.position

    def __copy__(self):
        return self.copy()

    def copy(self, deepcopy_values=True) -> 'ParserState[StateT]':
        return type(self)(
            self.parse_conf,
            self.lexer, # XXX copy
            copy(self.state_stack),
            deepcopy(self.value_stack) if deepcopy_values else copy(self.value_stack),
        )

    def feed_token(self, token: Token, is_end=False) -> Any:
        state_stack = self.state_stack
        value_stack = self.value_stack
        states = self.parse_conf.states
        end_state = self.parse_conf.end_state
        callbacks = self.parse_conf.callbacks

        while True:
            state = state_stack[-1]
            try:
                action, arg = states[state][token.type]
            except KeyError:
                expected = {s for s in states[state].keys() if s.isupper()}
                raise UnexpectedToken(token, expected, state=self, interactive_parser=None)

            assert arg != end_state

            if action is Shift:
                # shift once and return
                assert not is_end
                state_stack.append(arg)
                value_stack.append(token if token.type not in callbacks else callbacks[token.type](token))
                return
            else:
                # reduce+shift as many times as necessary
                rule = arg
                size = len(rule.expansion)
                if size:
                    s = value_stack[-size:]
                    del state_stack[-size:]
                    del value_stack[-size:]
                else:
                    s = []

                value = callbacks[rule](s) if callbacks else s

                _action, new_state = states[state_stack[-1]][rule.origin.name]
                assert _action is Shift
                state_stack.append(new_state)
                value_stack.append(value)

                if is_end and state_stack[-1] == end_state:
                    return value_stack[-1]
###}