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|
"""Step through a stream of tokens."""
from __future__ import annotations
from typing import Iterable
from .exceptions import JSONPathSyntaxError
from .token import TOKEN_EOF
from .token import TOKEN_WHITESPACE
from .token import Token
class TokenStream:
"""Step through a stream of tokens."""
def __init__(self, token_iter: Iterable[Token]):
self.tokens = list(token_iter)
self.pos = 0
path = self.tokens[0].path if self.tokens else ""
self.eof = Token(TOKEN_EOF, "", -1, path)
def __str__(self) -> str: # pragma: no cover
return f"current: {self.current}\nnext: {self.peek}"
def current(self) -> Token:
"""Return the token at the current position in the stream."""
try:
return self.tokens[self.pos]
except IndexError:
return self.eof
def next(self) -> Token:
"""Return the token at the current position and advance the pointer."""
try:
token = self.tokens[self.pos]
self.pos += 1
return token
except IndexError:
return self.eof
def peek(self, offset: int = 1) -> Token:
"""Return the token at current position plus the offset.
Does not advance the pointer.
"""
try:
return self.tokens[self.pos + offset]
except IndexError:
return self.eof
def eat(self, kind: str, message: str | None = None) -> Token:
"""Assert tge type if the current token and advance the pointer."""
token = self.next()
if token.kind != kind:
raise JSONPathSyntaxError(
message or f"expected {kind}, found {token.kind!r}",
token=token,
)
return token
def expect(self, *typ: str) -> None:
"""Raise an exception of the current token is not in `typ`."""
token = self.current()
if token.kind not in typ:
if len(typ) == 1:
_typ = repr(typ[0])
else:
_typ = f"one of {typ!r}"
raise JSONPathSyntaxError(
f"expected {_typ}, found {token.kind!r}",
token=token,
)
def expect_peek(self, *typ: str) -> None:
"""Raise an exception of the current token is not in `typ`."""
token = self.peek()
if token.kind not in typ:
if len(typ) == 1:
_typ = repr(typ[0])
else:
_typ = f"one of {typ!r}"
raise JSONPathSyntaxError(
f"expected {_typ}, found {token.kind!r}",
token=token,
)
def expect_peek_not(self, typ: str, message: str) -> None:
"""Raise an exception if the next token kind of _typ_."""
if self.peek().kind == typ:
raise JSONPathSyntaxError(message, token=self.peek())
def skip_whitespace(self) -> bool:
"""Skip whitespace."""
if self.current().kind == TOKEN_WHITESPACE:
self.pos += 1
return True
return False
|
