llama_cpp/llama_grammar.py

"""Python implementation of llama grammar parser directly translated from C++ source file in vendor/llama.cpp/common/grammar-parser.cpp."""

# flake8: noqa
from pathlib import Path

from itertools import groupby
from typing import (
    Any,
    Set,
    List,
    Optional,
    Tuple,
    Union,
)

LLAMA_GRAMMAR_DEFAULT_ROOT = "root"


class LlamaGrammar:
    def __init__(self, *args, _grammar: str, **kwargs):
        self._grammar = _grammar
        self._root = LLAMA_GRAMMAR_DEFAULT_ROOT

    @classmethod
    def from_string(cls, grammar: str, verbose: bool = True) -> "LlamaGrammar":
        return cls(_grammar=grammar)

    @classmethod
    def from_file(cls, file: Union[str, Path], verbose: bool = True) -> "LlamaGrammar":
        try:
            with open(file) as f:
                grammar = f.read()
        except Exception as err:
            raise Exception(
                f"{cls.from_file.__name__}: error reading grammar file: {err}"
            )

        if grammar:
            return cls.from_string(grammar, verbose=verbose)

        raise ValueError(
            f"{cls.from_file.__name__}: error parsing grammar file: params_grammer is empty"
        )

    @classmethod
    def from_json_schema(cls, json_schema: str, verbose: bool = True) -> "LlamaGrammar":
        return cls.from_string(json_schema_to_gbnf(json_schema), verbose=verbose)


"""llama.cpp gbnf rules from vendor/llama.cpp/grammars"""

ARITHMETIC_GBNF = r"""
root  ::= (expr "=" ws term "\n")+
expr  ::= term ([-+*/] term)*
term  ::= ident | num | "(" ws expr ")" ws
ident ::= [a-z] [a-z0-9_]* ws
num   ::= [0-9]+ ws
ws    ::= [ \t\n]*
"""

C_GBNF = r"""
root ::= (declaration)*

declaration ::= dataType identifier "(" parameter? ")" "{" statement* "}"

dataType  ::= "int" ws | "float" ws | "char" ws
identifier ::= [a-zA-Z_] [a-zA-Z_0-9]*

parameter ::= dataType identifier

statement ::=
    ( dataType identifier ws "=" ws expression ";" ) |
    ( identifier ws "=" ws expression ";" ) |
    ( identifier ws "(" argList? ")" ";" ) |
    ( "return" ws expression ";" ) |
    ( "while" "(" condition ")" "{" statement* "}" ) |
    ( "for" "(" forInit ";" ws condition ";" ws forUpdate ")" "{" statement* "}" ) |
    ( "if" "(" condition ")" "{" statement* "}" ("else" "{" statement* "}")? ) |
    ( singleLineComment ) |
    ( multiLineComment )

forInit ::= dataType identifier ws "=" ws expression | identifier ws "=" ws expression
forUpdate ::= identifier ws "=" ws expression

condition ::= expression relationOperator expression
relationOperator ::= ("<=" | "<" | "==" | "!=" | ">=" | ">")

expression ::= term (("+" | "-") term)*
term ::= factor(("*" | "/") factor)*

factor ::= identifier | number | unaryTerm | funcCall | parenExpression
unaryTerm ::= "-" factor
funcCall ::= identifier "(" argList? ")"
parenExpression ::= "(" ws expression ws ")"

argList ::= expression ("," ws expression)*

number ::= [0-9]+

singleLineComment ::= "//" [^\n]* "\n"
multiLineComment ::= "/*" ( [^*] | ("*" [^/]) )* "*/"

ws ::= ([ \t\n]+)
"""

CHESS_GBNF = r"""
root   ::= object
value  ::= object | array | string | number | ("true" | "false" | "null") ws

object ::=
  "{" ws (
            string ":" ws value
    ("," ws string ":" ws value)*
  )? "}" ws

array  ::=
  "[" ws (
            value
    ("," ws value)*
  )? "]" ws

string ::=
  "\"" (
    [^"\\] |
    "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F]) # escapes
  )* "\"" ws

number ::= ("-"? ([0-9] | [1-9] [0-9]*)) ("." [0-9]+)? ([eE] [-+]? [0-9]+)? ws

# Optional space: by convention, applied in this grammar after literal chars when allowed
ws ::= ([ \t\n] ws)?
"""

JAPANESE_GBNF = r"""
root   ::= object
value  ::= object | array | string | number | ("true" | "false" | "null") ws

object ::=
  "{" ws (
            string ":" ws value
    ("," ws string ":" ws value)*
  )? "}" ws

array  ::=
  "[" ws (
            value
    ("," ws value)*
  )? "]" ws

string ::=
  "\"" (
    [^"\\] |
    "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F]) # escapes
  )* "\"" ws

number ::= ("-"? ([0-9] | [1-9] [0-9]*)) ("." [0-9]+)? ([eE] [-+]? [0-9]+)? ws

# Optional space: by convention, applied in this grammar after literal chars when allowed
ws ::= ([ \t\n] ws)?
"""

JSON_ARR_GBNF = r"""
# This is the same as json.gbnf but we restrict whitespaces at the end of the root array
# Useful for generating JSON arrays

root   ::= arr
value  ::= object | array | string | number | ("true" | "false" | "null") ws

arr  ::=
  "[\n" ws (
            value
    (",\n" ws value)*
  )? "]"

object ::=
  "{" ws (
            string ":" ws value
    ("," ws string ":" ws value)*
  )? "}" ws

array  ::=
  "[" ws (
            value
    ("," ws value)*
  )? "]" ws

string ::=
  "\"" (
    [^"\\\x7F\x00-\x1F] |
    "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F]) # escapes
  )* "\"" ws

number ::= ("-"? ([0-9] | [1-9] [0-9]*)) ("." [0-9]+)? ([eE] [-+]? [0-9]+)? ws

# Optional space: by convention, applied in this grammar after literal chars when allowed
ws ::= ([ \t\n] ws)?
"""


JSON_GBNF = r"""
root   ::= object
value  ::= object | array | string | number | ("true" | "false" | "null") ws

object ::=
  "{" ws (
            string ":" ws value
    ("," ws string ":" ws value)*
  )? "}" ws

array  ::=
  "[" ws (
            value
    ("," ws value)*
  )? "]" ws

string ::=
  "\"" (
    [^"\\\x7F\x00-\x1F] |
    "\\" (["\\bfnrt] | "u" [0-9a-fA-F]{4}) # escapes
  )* "\"" ws

number ::= ("-"? ([0-9] | [1-9] [0-9]{0,15})) ("." [0-9]+)? ([eE] [-+]? [0-9] [1-9]{0,15})? ws

# Optional space: by convention, applied in this grammar after literal chars when allowed
ws ::= | " " | "\n" [ \t]{0,20}
"""

LIST_GBNF = r"""
root ::= item+

# Excludes various line break characters
item ::= "- " [^\r\n\x0b\x0c\x85\u2028\u2029]+ "\n"
"""

"""llama.cpp json-schema to grammar converter from vendor/llama.cpp/examples/json-schema-to-grammar.py"""
import json
import re
from typing import List, Optional

# whitespace is constrained to a single space char to prevent model "running away" in
# whitespace. Also maybe improves generation quality?
SPACE_RULE = '" "?'


INVALID_RULE_CHARS_RE = re.compile(r"[^a-zA-Z0-9-]+")
GRAMMAR_LITERAL_ESCAPE_RE = re.compile(r'[\r\n"]')
GRAMMAR_LITERAL_ESCAPES = {"\r": "\\r", "\n": "\\n", '"': '\\"'}

# whitespace is constrained to a single space char to prevent model "running away" in
# whitespace. Also maybe improves generation quality?
SPACE_RULE = '" "?'


def _build_repetition(
    item_rule, min_items, max_items, separator_rule=None, item_rule_is_literal=False
):
    if not separator_rule:
        if min_items == 0 and max_items == 1:
            return f"{item_rule}?"
        elif min_items == 1 and max_items is None:
            return f"{item_rule}+"

    result = ""

    if min_items > 0:
        if item_rule_is_literal and separator_rule is None:
            result = '"' + (item_rule[1:-1] * min_items) + '"'
        else:
            result = (f" {separator_rule} " if separator_rule else " ").join(
                [item_rule] * min_items
            )

    def opt_repetitions(up_to_n, prefix_with_sep=False):
        """
        - n=4, no sep:             '(a (a (a (a)?)?)?)?'
        - n=4, sep=',', prefix:    '("," a ("," a ("," a ("," a)?)?)?)?'
        - n=4, sep=',', no prefix: '(a ("," a ("," a ("," a)?)?)?)?'
        """

        content = (
            f"{separator_rule} {item_rule}"
            if prefix_with_sep and separator_rule
            else item_rule
        )
        if up_to_n == 0:
            return ""
        elif up_to_n == 1:
            return f"({content})?"
        elif separator_rule and not prefix_with_sep:
            return f"({content} {opt_repetitions(up_to_n - 1, prefix_with_sep=True)})?"
        else:
            return (f"({content} " * up_to_n).rstrip() + (")?" * up_to_n)

    if min_items > 0 and max_items != min_items:
        result += " "

    if max_items is not None:
        result += opt_repetitions(max_items - min_items, prefix_with_sep=min_items > 0)
    else:
        item_operator = f'({separator_rule + " " if separator_rule else ""}{item_rule})'

        if min_items == 0 and separator_rule:
            result = f"({item_rule} {item_operator}*)?"
        else:
            result += f"{item_operator}*"

    return result


class BuiltinRule:
    def __init__(self, content: str, deps: list = None):
        self.content = content
        self.deps = deps or []


_up_to_15_digits = _build_repetition("[0-9]", 0, 15)

PRIMITIVE_RULES = {
    "boolean": BuiltinRule('("true" | "false") space', []),
    "decimal-part": BuiltinRule("[0-9] " + _up_to_15_digits, []),
    "integral-part": BuiltinRule("[0-9] | [1-9] " + _up_to_15_digits, []),
    "number": BuiltinRule(
        '("-"? integral-part) ("." decimal-part)? ([eE] [-+]? integral-part)? space',
        ["integral-part", "decimal-part"],
    ),
    "integer": BuiltinRule('("-"? integral-part) space', ["integral-part"]),
    "value": BuiltinRule(
        "object | array | string | number | boolean | null",
        ["object", "array", "string", "number", "boolean", "null"],
    ),
    "object": BuiltinRule(
        '"{" space ( string ":" space value ("," space string ":" space value)* )? "}" space',
        ["string", "value"],
    ),
    "array": BuiltinRule(
        '"[" space ( value ("," space value)* )? "]" space', ["value"]
    ),
    "uuid": BuiltinRule(
        r'"\"" '
        + ' "-" '.join("[0-9a-fA-F]" * n for n in [8, 4, 4, 4, 12])
        + r' "\"" space',
        [],
    ),
    "char": BuiltinRule(
        r'[^"\\] | "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F])',
        [],
    ),
    "string": BuiltinRule(r'"\"" char* "\"" space', ["char"]),
    "null": BuiltinRule('"null" space', []),
}

# TODO: support "uri", "email" string formats
STRING_FORMAT_RULES = {
    "date": BuiltinRule(
        '[0-9] [0-9] [0-9] [0-9] "-" ( "0" [1-9] | "1" [0-2] ) "-" ( "0" [1-9] | [1-2] [0-9] | "3" [0-1] )',
        [],
    ),
    "time": BuiltinRule(
        '([01] [0-9] | "2" [0-3]) ":" [0-5] [0-9] ":" [0-5] [0-9] ( "." [0-9] [0-9] [0-9] )? ( "Z" | ( "+" | "-" ) ( [01] [0-9] | "2" [0-3] ) ":" [0-5] [0-9] )',
        [],
    ),
    "date-time": BuiltinRule('date "T" time', ["date", "time"]),
    "date-string": BuiltinRule('"\\"" date "\\"" space', ["date"]),
    "time-string": BuiltinRule('"\\"" time "\\"" space', ["time"]),
    "date-time-string": BuiltinRule('"\\"" date-time "\\"" space', ["date-time"]),
}

DOTALL = "[\\U00000000-\\U0010FFFF]"
DOT = "[^\\x0A\\x0D]"

RESERVED_NAMES = set(
    ["root", "dot", *PRIMITIVE_RULES.keys(), *STRING_FORMAT_RULES.keys()]
)


NON_LITERAL_SET = set("|.()[]{}*+?")
ESCAPED_IN_REGEXPS_BUT_NOT_IN_LITERALS = set("[]()|{}*+?")


class SchemaConverter:
    def __init__(self, *, prop_order, allow_fetch, dotall, raw_pattern):
        self._prop_order = prop_order
        self._allow_fetch = allow_fetch
        self._dotall = dotall
        self._raw_pattern = raw_pattern
        self._rules = {
            "space": SPACE_RULE,
        }
        self._refs = {}
        self._refs_being_resolved = set()

    def _format_literal(self, literal):
        escaped = GRAMMAR_LITERAL_ESCAPE_RE.sub(
            lambda m: GRAMMAR_LITERAL_ESCAPES.get(m.group(0)), literal
        )
        return f'"{escaped}"'

    def not_literal(
        self, literal: str, dotall: bool = True, maybe_escaped_underscores=False
    ) -> str:
        """
        not_literal('a') -> '[^a]'
        not_literal('abc') -> '([^a] | "a" ([^b] | "b" ([^c])?)?)?'
        """
        assert len(literal) > 0, "Empty literal not supported"

        def recurse(i: int):
            c = literal[i]
            if maybe_escaped_underscores and c == "_":
                yield f"[^{c}\\\\]"
                yield " | "
                yield f'"\\\\"? "{c}"'
            else:
                yield f"[^{c}]"
            if i < len(literal) - 1:
                yield " | "
                yield self._format_literal(c)
                yield " ("
                yield from recurse(i + 1)
                yield ")?"

        return "".join(("(", *recurse(0), ")"))

    def _add_rule(self, name, rule):
        esc_name = INVALID_RULE_CHARS_RE.sub("-", name)
        if esc_name not in self._rules or self._rules[esc_name] == rule:
            key = esc_name
        else:
            i = 0
            while (
                f"{esc_name}{i}" in self._rules
                and self._rules[f"{esc_name}{i}"] != rule
            ):
                i += 1
            key = f"{esc_name}{i}"
        self._rules[key] = rule
        return key

    def resolve_refs(self, schema: dict, url: str):
        """
        Resolves all $ref fields in the given schema, fetching any remote schemas,
        replacing $ref with absolute reference URL and populating self._refs with the
        respective referenced (sub)schema dictionaries.
        """

        def visit(n: dict):
            if isinstance(n, list):
                return [visit(x) for x in n]
            elif isinstance(n, dict):
                ref = n.get("$ref")
                if ref is not None and ref not in self._refs:
                    if ref.startswith("https://"):
                        assert (
                            self._allow_fetch
                        ), "Fetching remote schemas is not allowed (use --allow-fetch for force)"
                        import requests

                        frag_split = ref.split("#")
                        base_url = frag_split[0]

                        target = self._refs.get(base_url)
                        if target is None:
                            target = self.resolve_refs(
                                requests.get(ref).json(), base_url
                            )
                            self._refs[base_url] = target

                        if len(frag_split) == 1 or frag_split[-1] == "":
                            return target
                    elif ref.startswith("#/"):
                        target = schema
                        ref = f"{url}{ref}"
                        n["$ref"] = ref
                    else:
                        raise ValueError(f"Unsupported ref {ref}")

                    for sel in ref.split("#")[-1].split("/")[1:]:
                        assert (
                            target is not None and sel in target
                        ), f"Error resolving ref {ref}: {sel} not in {target}"
                        target = target[sel]

                    self._refs[ref] = target
                else:
                    for v in n.values():
                        visit(v)

            return n

        return visit(schema)

    def _generate_union_rule(self, name, alt_schemas):
        return " | ".join(
            (
                self.visit(alt_schema, f'{name}{"-" if name else "alternative-"}{i}')
                for i, alt_schema in enumerate(alt_schemas)
            )
        )

    def _visit_pattern(self, pattern, name):
        """
        Transforms a regular expression pattern into a GBNF rule.

        Input: https://json-schema.org/understanding-json-schema/reference/regular_expressions
        Output: https://github.com/ggerganov/llama.cpp/blob/master/grammars/README.md

        Unsupported features: negative/positive lookaheads, greedy/non-greedy modifiers.

        Mostly a 1:1 translation, except for {x} / {x,} / {x,y} quantifiers for which
        we define sub-rules to keep the output lean.
        """

        assert pattern.startswith("^") and pattern.endswith(
            "$"
        ), 'Pattern must start with "^" and end with "$"'
        pattern = pattern[1:-1]
        sub_rule_ids = {}

        i = 0
        length = len(pattern)

        def to_rule(s: Tuple[str, bool]) -> str:
            (txt, is_literal) = s
            return '"' + txt + '"' if is_literal else txt

        def transform() -> Tuple[str, bool]:
            """
            Parse a unit at index i (advancing it), and return its string representation + whether it's a literal.
            """
            nonlocal i
            nonlocal pattern
            nonlocal sub_rule_ids

            start = i
            # For each component of this sequence, store its string representation and whether it's a literal.
            # We only need a flat structure here to apply repetition operators to the last item, and
            # to merge literals at the and (we're parsing grouped ( sequences ) recursively and don't treat '|' specially
            # (GBNF's syntax is luckily very close to regular expressions!)
            seq: list[Tuple[str, bool]] = []

            def get_dot():
                if self._dotall:
                    rule = DOTALL
                else:
                    # Accept any character... except \n and \r line break chars (\x0A and \xOD)
                    rule = DOT
                return self._add_rule(f"dot", rule)

            def join_seq():
                nonlocal seq
                ret = []
                for is_literal, g in groupby(seq, lambda x: x[1]):
                    if is_literal:
                        ret.append(("".join(x[0] for x in g), True))
                    else:
                        ret.extend(g)
                if len(ret) == 1:
                    return ret[0]
                return (" ".join(to_rule(x) for x in seq), False)

            while i < length:
                c = pattern[i]
                if c == ".":
                    seq.append((get_dot(), False))
                    i += 1
                elif c == "(":
                    i += 1
                    if i < length:
                        assert (
                            pattern[i] != "?"
                        ), f'Unsupported pattern syntax "{pattern[i]}" at index {i} of /{pattern}/'
                    seq.append((f"({to_rule(transform())})", False))
                elif c == ")":
                    i += 1
                    assert (
                        start > 0 and pattern[start - 1] == "("
                    ), f"Unbalanced parentheses; start = {start}, i = {i}, pattern = {pattern}"
                    return join_seq()
                elif c == "[":
                    square_brackets = c
                    i += 1
                    while i < length and pattern[i] != "]":
                        if pattern[i] == "\\":
                            square_brackets += pattern[i : i + 2]
                            i += 2
                        else:
                            square_brackets += pattern[i]
                            i += 1
                    assert (
                        i < length
                    ), f"Unbalanced square brackets; start = {start}, i = {i}, pattern = {pattern}"
                    square_brackets += "]"
                    i += 1
                    seq.append((square_brackets, False))
                elif c == "|":
                    seq.append(("|", False))
                    i += 1
                elif c in ("*", "+", "?"):
                    seq[-1] = (to_rule(seq[-1]) + c, False)
                    i += 1
                elif c == "{":
                    curly_brackets = c
                    i += 1
                    while i < length and pattern[i] != "}":
                        curly_brackets += pattern[i]
                        i += 1
                    assert (
                        i < length
                    ), f"Unbalanced curly brackets; start = {start}, i = {i}, pattern = {pattern}"
                    curly_brackets += "}"
                    i += 1
                    nums = [s.strip() for s in curly_brackets[1:-1].split(",")]
                    min_times = 0
                    max_times = None
                    try:
                        if len(nums) == 1:
                            min_times = int(nums[0])
                            max_times = min_times
                        else:
                            assert len(nums) == 2
                            min_times = int(nums[0]) if nums[0] else 0
                            max_times = int(nums[1]) if nums[1] else None
                    except ValueError:
                        raise ValueError(
                            f"Invalid quantifier {curly_brackets} in /{pattern}/"
                        )

                    (sub, sub_is_literal) = seq[-1]

                    if not sub_is_literal:
                        id = sub_rule_ids.get(sub)
                        if id is None:
                            id = self._add_rule(f"{name}-{len(sub_rule_ids) + 1}", sub)
                            sub_rule_ids[sub] = id
                        sub = id

                    seq[-1] = (
                        _build_repetition(
                            f'"{sub}"' if sub_is_literal else sub,
                            min_times,
                            max_times,
                            item_rule_is_literal=sub_is_literal,
                        ),
                        False,
                    )
                else:
                    literal = ""
                    while i < length:
                        if pattern[i] == "\\" and i < length - 1:
                            next = pattern[i + 1]
                            if next in ESCAPED_IN_REGEXPS_BUT_NOT_IN_LITERALS:
                                i += 1
                                literal += pattern[i]
                                i += 1
                            else:
                                literal += pattern[i : i + 2]
                                i += 2
                        elif pattern[i] == '"' and not self._raw_pattern:
                            literal += '\\"'
                            i += 1
                        elif pattern[i] not in NON_LITERAL_SET and (
                            i == length - 1
                            or literal == ""
                            or pattern[i + 1] == "."
                            or pattern[i + 1] not in NON_LITERAL_SET
                        ):
                            literal += pattern[i]
                            i += 1
                        else:
                            break
                    if literal:
                        seq.append((literal, True))

            return join_seq()

        return self._add_rule(
            name,
            (
                to_rule(transform())
                if self._raw_pattern
                else '"\\"" ' + to_rule(transform()) + ' "\\"" space'
            ),
        )

    def _resolve_ref(self, ref):
        ref_name = ref.split("/")[-1]
        if ref_name not in self._rules and ref not in self._refs_being_resolved:
            self._refs_being_resolved.add(ref)
            resolved = self._refs[ref]
            ref_name = self.visit(resolved, ref_name)
            self._refs_being_resolved.remove(ref)
        return ref_name

    def _generate_constant_rule(self, value):
        return self._format_literal(json.dumps(value))

    def visit(self, schema, name):
        schema_type = schema.get("type")
        schema_format = schema.get("format")
        rule_name = name + "-" if name in RESERVED_NAMES else name or "root"

        if (ref := schema.get("$ref")) is not None:
            return self._add_rule(rule_name, self._resolve_ref(ref))

        elif "oneOf" in schema or "anyOf" in schema:
            return self._add_rule(
                rule_name,
                self._generate_union_rule(name, schema.get("oneOf") or schema["anyOf"]),
            )

        elif isinstance(schema_type, list):
            return self._add_rule(
                rule_name,
                self._generate_union_rule(name, [{"type": t} for t in schema_type]),
            )

        elif "const" in schema:
            return self._add_rule(
                rule_name, self._generate_constant_rule(schema["const"])
            )

        elif "enum" in schema:
            rule = " | ".join((self._generate_constant_rule(v) for v in schema["enum"]))
            return self._add_rule(rule_name, rule)

        elif schema_type in (None, "object") and (
            "properties" in schema
            or (
                "additionalProperties" in schema
                and schema["additionalProperties"] is not True
            )
        ):
            required = set(schema.get("required", []))
            properties = list(schema.get("properties", {}).items())
            return self._add_rule(
                rule_name,
                self._build_object_rule(
                    properties, required, name, schema.get("additionalProperties")
                ),
            )

        elif schema_type in (None, "object") and "allOf" in schema:
            required = set()
            properties = []
            hybrid_name = name

            def add_component(comp_schema, is_required):
                if (ref := comp_schema.get("$ref")) is not None:
                    comp_schema = self._refs[ref]

                if "properties" in comp_schema:
                    for prop_name, prop_schema in comp_schema["properties"].items():
                        properties.append((prop_name, prop_schema))
                        if is_required:
                            required.add(prop_name)

            for t in schema["allOf"]:
                if "anyOf" in t:
                    for tt in t["anyOf"]:
                        add_component(tt, is_required=False)
                else:
                    add_component(t, is_required=True)

            return self._add_rule(
                rule_name,
                self._build_object_rule(
                    properties, required, hybrid_name, additional_properties=[]
                ),
            )

        elif schema_type in (None, "array") and (
            "items" in schema or "prefixItems" in schema
        ):
            items = schema.get("items") or schema["prefixItems"]
            if isinstance(items, list):
                return self._add_rule(
                    rule_name,
                    '"[" space '
                    + ' "," space '.join(
                        self.visit(item, f'{name}{"-" if name else ""}tuple-{i}')
                        for i, item in enumerate(items)
                    )
                    + ' "]" space',
                )
            else:
                item_rule_name = self.visit(items, f'{name}{"-" if name else ""}item')
                min_items = schema.get("minItems", 0)
                max_items = schema.get("maxItems")
                return self._add_rule(
                    rule_name,
                    '"[" space '
                    + _build_repetition(
                        item_rule_name, min_items, max_items, separator_rule='"," space'
                    )
                    + ' "]" space',
                )

        elif schema_type in (None, "string") and "pattern" in schema:
            return self._visit_pattern(schema["pattern"], rule_name)

        elif schema_type in (None, "string") and re.match(
            r"^uuid[1-5]?$", schema_format or ""
        ):
            return self._add_primitive(
                "root" if rule_name == "root" else schema_format,
                PRIMITIVE_RULES["uuid"],
            )

        elif (
            schema_type in (None, "string")
            and f"{schema_format}-string" in STRING_FORMAT_RULES
        ):
            prim_name = f"{schema_format}-string"
            return self._add_rule(
                rule_name,
                self._add_primitive(prim_name, STRING_FORMAT_RULES[prim_name]),
            )

        elif schema_type == "string" and (
            "minLength" in schema or "maxLength" in schema
        ):
            char_rule = self._add_primitive("char", PRIMITIVE_RULES["char"])
            min_len = schema.get("minLength", 0)
            max_len = schema.get("maxLength")

            return self._add_rule(
                rule_name,
                r'"\"" '
                + _build_repetition(char_rule, min_len, max_len)
                + r' "\"" space',
            )

        elif (schema_type == "object") or (len(schema) == 0):
            return self._add_rule(
                rule_name, self._add_primitive("object", PRIMITIVE_RULES["object"])
            )

        else:
            assert schema_type in PRIMITIVE_RULES, f"Unrecognized schema: {schema}"
            # TODO: support minimum, maximum, exclusiveMinimum, exclusiveMaximum at least for zero
            return self._add_primitive(
                "root" if rule_name == "root" else schema_type,
                PRIMITIVE_RULES[schema_type],
            )

    def _add_primitive(self, name: str, rule: BuiltinRule):
        n = self._add_rule(name, rule.content)

        for dep in rule.deps:
            dep_rule = PRIMITIVE_RULES.get(dep) or STRING_FORMAT_RULES.get(dep)
            assert dep_rule, f"Rule {dep} not known"
            if dep not in self._rules:
                self._add_primitive(dep, dep_rule)
        return n

    def _build_object_rule(
        self,
        properties: List[Tuple[str, Any]],
        required: Set[str],
        name: str,
        additional_properties: Union[bool, Any],
    ):
        prop_order = self._prop_order
        # sort by position in prop_order (if specified) then by original order
        sorted_props = [
            kv[0]
            for _, kv in sorted(
                enumerate(properties),
                key=lambda ikv: (prop_order.get(ikv[1][0], len(prop_order)), ikv[0]),
            )
        ]

        prop_kv_rule_names = {}
        for prop_name, prop_schema in properties:
            prop_rule_name = self.visit(
                prop_schema, f'{name}{"-" if name else ""}{prop_name}'
            )
            prop_kv_rule_names[prop_name] = self._add_rule(
                f'{name}{"-" if name else ""}{prop_name}-kv',
                rf'{self._format_literal(json.dumps(prop_name))} space ":" space {prop_rule_name}',
            )
        required_props = [k for k in sorted_props if k in required]
        optional_props = [k for k in sorted_props if k not in required]

        if additional_properties == True or isinstance(additional_properties, dict):
            sub_name = f'{name}{"-" if name else ""}additional'
            value_rule = self.visit(
                {} if additional_properties == True else additional_properties,
                f"{sub_name}-value",
            )
            prop_kv_rule_names["*"] = self._add_rule(
                f"{sub_name}-kv",
                self._add_primitive("string", PRIMITIVE_RULES["string"])
                + f' ":" space {value_rule}',
            )
            optional_props.append("*")

        rule = '"{" space '
        rule += ' "," space '.join(prop_kv_rule_names[k] for k in required_props)

        if optional_props:
            rule += " ("
            if required_props:
                rule += ' "," space ( '

            def get_recursive_refs(ks, first_is_optional):
                [k, *rest] = ks
                kv_rule_name = prop_kv_rule_names[k]
                if k == "*":
                    res = self._add_rule(
                        f'{name}{"-" if name else ""}additional-kvs',
                        f'{kv_rule_name} ( "," space ' + kv_rule_name + " )*",
                    )
                elif first_is_optional:
                    res = f'( "," space {kv_rule_name} )?'
                else:
                    res = kv_rule_name
                if len(rest) > 0:
                    res += " " + self._add_rule(
                        f'{name}{"-" if name else ""}{k}-rest',
                        get_recursive_refs(rest, first_is_optional=True),
                    )
                return res

            rule += " | ".join(
                get_recursive_refs(optional_props[i:], first_is_optional=False)
                for i in range(len(optional_props))
            )
            if required_props:
                rule += " )"
            rule += " )?"

        rule += ' "}" space'

        return rule

    def format_grammar(self):
        return "\n".join(
            f"{name} ::= {rule}"
            for name, rule in sorted(self._rules.items(), key=lambda kv: kv[0])
        )


def json_schema_to_gbnf(schema: str, prop_order: Optional[List[str]] = None):
    prop_order = prop_order or []
    schema = json.loads(schema)
    prop_order = {name: idx for idx, name in enumerate(prop_order)}
    converter = SchemaConverter(
        prop_order=prop_order, allow_fetch=False, dotall=False, raw_pattern=False
    )
    schema = converter.resolve_refs(schema, "stdin")
    converter.visit(schema, "")
    return converter.format_grammar()