ferroni 2.7.0

//! Port of `regsyntax.c`, and of the Oniguruma and Ruby syntaxes from
//! `regparse.c`. It holds one `OnigSyntax*` static per language and the
//! functions that read and change a syntax. Pass a static to
//! [`RegexBuilder::syntax`](crate::api::RegexBuilder::syntax), or pass a typed
//! [`Syntax`](crate::api::Syntax) to
//! [`RegexBuilder::syntax_mode`](crate::api::RegexBuilder::syntax_mode).

#![allow(non_upper_case_globals)]

use std::sync::{OnceLock, RwLock};

use crate::oniguruma::*;

// === Composite Helper Constants (from regint.h) ===

pub(crate) const SYN_POSIX_COMMON_OP: u32 = ONIG_SYN_OP_DOT_ANYCHAR
    | ONIG_SYN_OP_POSIX_BRACKET
    | ONIG_SYN_OP_DECIMAL_BACKREF
    | ONIG_SYN_OP_BRACKET_CC
    | ONIG_SYN_OP_ASTERISK_ZERO_INF
    | ONIG_SYN_OP_LINE_ANCHOR
    | ONIG_SYN_OP_ESC_CONTROL_CHARS;

pub(crate) const SYN_GNU_REGEX_OP: u32 = ONIG_SYN_OP_DOT_ANYCHAR
    | ONIG_SYN_OP_BRACKET_CC
    | ONIG_SYN_OP_POSIX_BRACKET
    | ONIG_SYN_OP_DECIMAL_BACKREF
    | ONIG_SYN_OP_BRACE_INTERVAL
    | ONIG_SYN_OP_LPAREN_SUBEXP
    | ONIG_SYN_OP_VBAR_ALT
    | ONIG_SYN_OP_ASTERISK_ZERO_INF
    | ONIG_SYN_OP_PLUS_ONE_INF
    | ONIG_SYN_OP_QMARK_ZERO_ONE
    | ONIG_SYN_OP_ESC_AZ_BUF_ANCHOR
    | ONIG_SYN_OP_ESC_CAPITAL_G_BEGIN_ANCHOR
    | ONIG_SYN_OP_ESC_W_WORD
    | ONIG_SYN_OP_ESC_B_WORD_BOUND
    | ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END
    | ONIG_SYN_OP_ESC_S_WHITE_SPACE
    | ONIG_SYN_OP_ESC_D_DIGIT
    | ONIG_SYN_OP_LINE_ANCHOR;

pub(crate) const SYN_GNU_REGEX_BV: u32 = ONIG_SYN_CONTEXT_INDEP_ANCHORS
    | ONIG_SYN_CONTEXT_INDEP_REPEAT_OPS
    | ONIG_SYN_CONTEXT_INVALID_REPEAT_OPS
    | ONIG_SYN_ALLOW_INVALID_INTERVAL
    | ONIG_SYN_BACKSLASH_ESCAPE_IN_CC
    | ONIG_SYN_ALLOW_DOUBLE_RANGE_OP_IN_CC;

// === Default meta char table (shared by all built-in syntaxes) ===

const DEFAULT_META_CHAR_TABLE: OnigMetaCharTableType = OnigMetaCharTableType {
    esc: b'\\' as OnigCodePoint,
    anychar: ONIG_INEFFECTIVE_META_CHAR,
    anytime: ONIG_INEFFECTIVE_META_CHAR,
    zero_or_one_time: ONIG_INEFFECTIVE_META_CHAR,
    one_or_more_time: ONIG_INEFFECTIVE_META_CHAR,
    anychar_anytime: ONIG_INEFFECTIVE_META_CHAR,
};

// === Syntax Definitions ===

/// Plain text with no metacharacters (`Syntax::Asis`).
pub static OnigSyntaxASIS: OnigSyntaxType = OnigSyntaxType {
    op: 0,
    op2: ONIG_SYN_OP2_INEFFECTIVE_ESCAPE,
    behavior: 0,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// POSIX basic regular expressions (`Syntax::PosixBasic`).
pub static OnigSyntaxPosixBasic: OnigSyntaxType = OnigSyntaxType {
    op: SYN_POSIX_COMMON_OP | ONIG_SYN_OP_ESC_LPAREN_SUBEXP | ONIG_SYN_OP_ESC_BRACE_INTERVAL,
    op2: 0,
    behavior: ONIG_SYN_BRE_ANCHOR_AT_EDGE_OF_SUBEXP,
    options: ONIG_OPTION_SINGLELINE.union(ONIG_OPTION_MULTILINE),
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// POSIX extended regular expressions (`Syntax::PosixExtended`).
pub static OnigSyntaxPosixExtended: OnigSyntaxType = OnigSyntaxType {
    op: SYN_POSIX_COMMON_OP
        | ONIG_SYN_OP_LPAREN_SUBEXP
        | ONIG_SYN_OP_BRACE_INTERVAL
        | ONIG_SYN_OP_PLUS_ONE_INF
        | ONIG_SYN_OP_QMARK_ZERO_ONE
        | ONIG_SYN_OP_VBAR_ALT,
    op2: 0,
    behavior: ONIG_SYN_CONTEXT_INDEP_ANCHORS
        | ONIG_SYN_CONTEXT_INDEP_REPEAT_OPS
        | ONIG_SYN_CONTEXT_INVALID_REPEAT_OPS
        | ONIG_SYN_ALLOW_UNMATCHED_CLOSE_SUBEXP
        | ONIG_SYN_ALLOW_DOUBLE_RANGE_OP_IN_CC,
    options: ONIG_OPTION_SINGLELINE.union(ONIG_OPTION_MULTILINE),
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// GNU Emacs regular expressions (`Syntax::Emacs`).
pub static OnigSyntaxEmacs: OnigSyntaxType = OnigSyntaxType {
    op: ONIG_SYN_OP_DOT_ANYCHAR
        | ONIG_SYN_OP_BRACKET_CC
        | ONIG_SYN_OP_ESC_BRACE_INTERVAL
        | ONIG_SYN_OP_ESC_LPAREN_SUBEXP
        | ONIG_SYN_OP_ESC_VBAR_ALT
        | ONIG_SYN_OP_ASTERISK_ZERO_INF
        | ONIG_SYN_OP_PLUS_ONE_INF
        | ONIG_SYN_OP_QMARK_ZERO_ONE
        | ONIG_SYN_OP_DECIMAL_BACKREF
        | ONIG_SYN_OP_LINE_ANCHOR
        | ONIG_SYN_OP_ESC_CONTROL_CHARS,
    op2: ONIG_SYN_OP2_ESC_GNU_BUF_ANCHOR | ONIG_SYN_OP2_QMARK_GROUP_EFFECT,
    behavior: ONIG_SYN_ALLOW_EMPTY_RANGE_IN_CC,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// grep's basic regular expressions, with the GNU `\+`, `\?` and `\|`
/// operators (`Syntax::Grep`).
pub static OnigSyntaxGrep: OnigSyntaxType = OnigSyntaxType {
    op: ONIG_SYN_OP_DOT_ANYCHAR
        | ONIG_SYN_OP_BRACKET_CC
        | ONIG_SYN_OP_POSIX_BRACKET
        | ONIG_SYN_OP_ESC_BRACE_INTERVAL
        | ONIG_SYN_OP_ESC_LPAREN_SUBEXP
        | ONIG_SYN_OP_ESC_VBAR_ALT
        | ONIG_SYN_OP_ASTERISK_ZERO_INF
        | ONIG_SYN_OP_ESC_PLUS_ONE_INF
        | ONIG_SYN_OP_ESC_QMARK_ZERO_ONE
        | ONIG_SYN_OP_LINE_ANCHOR
        | ONIG_SYN_OP_ESC_W_WORD
        | ONIG_SYN_OP_ESC_B_WORD_BOUND
        | ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END
        | ONIG_SYN_OP_DECIMAL_BACKREF,
    op2: 0,
    behavior: ONIG_SYN_ALLOW_EMPTY_RANGE_IN_CC
        | ONIG_SYN_NOT_NEWLINE_IN_NEGATIVE_CC
        | ONIG_SYN_BRE_ANCHOR_AT_EDGE_OF_SUBEXP,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// GNU regex syntax, where unescaped `(`, `)` and `|` are operators
/// (`Syntax::GnuRegex`).
pub static OnigSyntaxGnuRegex: OnigSyntaxType = OnigSyntaxType {
    op: SYN_GNU_REGEX_OP,
    op2: 0,
    behavior: SYN_GNU_REGEX_BV,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// Java regular expressions, as in `java.util.regex` (`Syntax::Java`).
pub static OnigSyntaxJava: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2)
        & !(ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END | ONIG_SYN_OP_POSIX_BRACKET),
    op2: ONIG_SYN_OP2_ESC_CAPITAL_Q_QUOTE
        | ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_PERL
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_REPEAT
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_INTERVAL
        | ONIG_SYN_OP2_CCLASS_SET_OP
        | ONIG_SYN_OP2_ESC_V_VTAB
        | ONIG_SYN_OP2_ESC_U_HEX4
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ISOLATED_OPTION_CONTINUE_BRANCH
        | ONIG_SYN_DIFFERENT_LEN_ALT_LOOK_BEHIND
        | ONIG_SYN_VARIABLE_LEN_LOOK_BEHIND
        | ONIG_SYN_ALLOW_CHAR_TYPE_FOLLOWED_BY_MINUS_IN_CC,
    options: ONIG_OPTION_SINGLELINE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// Perl regular expressions, without named groups (`Syntax::Perl`).
pub static OnigSyntaxPerl: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2
        | ONIG_SYN_OP_ESC_X_BRACE_HEX8
        | ONIG_SYN_OP_ESC_O_BRACE_OCTAL
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL)
        & !ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END,
    op2: ONIG_SYN_OP2_ESC_CAPITAL_Q_QUOTE
        | ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_PERL
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_REPEAT
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_INTERVAL
        | ONIG_SYN_OP2_QMARK_LPAREN_IF_ELSE
        | ONIG_SYN_OP2_QMARK_TILDE_ABSENT_GROUP
        | ONIG_SYN_OP2_QMARK_BRACE_CALLOUT_CONTENTS
        | ONIG_SYN_OP2_ASTERISK_CALLOUT_NAME
        | ONIG_SYN_OP2_ESC_X_Y_TEXT_SEGMENT
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY
        | ONIG_SYN_OP2_ESC_P_BRACE_CIRCUMFLEX_NOT
        | ONIG_SYN_OP2_ESC_CAPITAL_K_KEEP
        | ONIG_SYN_OP2_ESC_CAPITAL_R_GENERAL_NEWLINE
        | ONIG_SYN_OP2_ESC_CAPITAL_N_O_SUPER_DOT,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ISOLATED_OPTION_CONTINUE_BRANCH
        | ONIG_SYN_ALLOW_CHAR_TYPE_FOLLOWED_BY_MINUS_IN_CC
        | ONIG_SYN_ESC_P_WITH_ONE_CHAR_PROP,
    options: ONIG_OPTION_SINGLELINE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// Perl regular expressions with named groups (`Syntax::PerlNg`).
pub static OnigSyntaxPerl_NG: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2
        | ONIG_SYN_OP_ESC_X_BRACE_HEX8
        | ONIG_SYN_OP_ESC_O_BRACE_OCTAL
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL)
        & !ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END,
    op2: ONIG_SYN_OP2_ESC_CAPITAL_Q_QUOTE
        | ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_PERL
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_REPEAT
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_INTERVAL
        | ONIG_SYN_OP2_QMARK_LPAREN_IF_ELSE
        | ONIG_SYN_OP2_QMARK_TILDE_ABSENT_GROUP
        | ONIG_SYN_OP2_QMARK_BRACE_CALLOUT_CONTENTS
        | ONIG_SYN_OP2_ASTERISK_CALLOUT_NAME
        | ONIG_SYN_OP2_ESC_X_Y_TEXT_SEGMENT
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY
        | ONIG_SYN_OP2_ESC_P_BRACE_CIRCUMFLEX_NOT
        | ONIG_SYN_OP2_QMARK_LT_NAMED_GROUP
        | ONIG_SYN_OP2_ESC_K_NAMED_BACKREF
        | ONIG_SYN_OP2_ESC_G_SUBEXP_CALL
        | ONIG_SYN_OP2_ESC_CAPITAL_K_KEEP
        | ONIG_SYN_OP2_ESC_CAPITAL_R_GENERAL_NEWLINE
        | ONIG_SYN_OP2_ESC_CAPITAL_N_O_SUPER_DOT
        | ONIG_SYN_OP2_QMARK_PERL_SUBEXP_CALL,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ISOLATED_OPTION_CONTINUE_BRANCH
        | ONIG_SYN_CAPTURE_ONLY_NAMED_GROUP
        | ONIG_SYN_ALLOW_MULTIPLEX_DEFINITION_NAME
        | ONIG_SYN_ALLOW_CHAR_TYPE_FOLLOWED_BY_MINUS_IN_CC
        | ONIG_SYN_ESC_P_WITH_ONE_CHAR_PROP,
    options: ONIG_OPTION_SINGLELINE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// Python regular expressions, as in the `re` module of Python 3.9
/// (`Syntax::Python`).
pub static OnigSyntaxPython: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL)
        & !(ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END | ONIG_SYN_OP_POSIX_BRACKET),
    op2: ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_PERL
        | ONIG_SYN_OP2_QMARK_LPAREN_IF_ELSE
        | ONIG_SYN_OP2_ASTERISK_CALLOUT_NAME
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY
        | ONIG_SYN_OP2_ESC_P_BRACE_CIRCUMFLEX_NOT
        | ONIG_SYN_OP2_QMARK_CAPITAL_P_NAME
        | ONIG_SYN_OP2_ESC_CAPITAL_K_KEEP
        | ONIG_SYN_OP2_ESC_V_VTAB
        | ONIG_SYN_OP2_ESC_U_HEX4,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ISOLATED_OPTION_CONTINUE_BRANCH
        | ONIG_SYN_ALLOW_INTERVAL_LOW_ABBREV
        | ONIG_SYN_PYTHON,
    options: ONIG_OPTION_SINGLELINE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// Oniguruma's own syntax, which [`Regex::new`](crate::api::Regex::new) uses
/// (`Syntax::Oniguruma`).
pub static OnigSyntaxOniguruma: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2
        | ONIG_SYN_OP_ESC_X_BRACE_HEX8
        | ONIG_SYN_OP_ESC_O_BRACE_OCTAL
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL)
        & !ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END,
    op2: ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_ONIGURUMA
        | ONIG_SYN_OP2_QMARK_LT_NAMED_GROUP
        | ONIG_SYN_OP2_ESC_K_NAMED_BACKREF
        | ONIG_SYN_OP2_QMARK_LPAREN_IF_ELSE
        | ONIG_SYN_OP2_QMARK_TILDE_ABSENT_GROUP
        | ONIG_SYN_OP2_QMARK_BRACE_CALLOUT_CONTENTS
        | ONIG_SYN_OP2_ASTERISK_CALLOUT_NAME
        | ONIG_SYN_OP2_ESC_X_Y_TEXT_SEGMENT
        | ONIG_SYN_OP2_ESC_CAPITAL_R_GENERAL_NEWLINE
        | ONIG_SYN_OP2_ESC_CAPITAL_N_O_SUPER_DOT
        | ONIG_SYN_OP2_ESC_CAPITAL_K_KEEP
        | ONIG_SYN_OP2_ESC_G_SUBEXP_CALL
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY
        | ONIG_SYN_OP2_ESC_P_BRACE_CIRCUMFLEX_NOT
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_REPEAT
        | ONIG_SYN_OP2_CCLASS_SET_OP
        | ONIG_SYN_OP2_ESC_CAPITAL_C_BAR_CONTROL
        | ONIG_SYN_OP2_ESC_CAPITAL_M_BAR_META
        | ONIG_SYN_OP2_ESC_V_VTAB
        | ONIG_SYN_OP2_ESC_H_XDIGIT
        | ONIG_SYN_OP2_ESC_U_HEX4,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ALLOW_INTERVAL_LOW_ABBREV
        | ONIG_SYN_DIFFERENT_LEN_ALT_LOOK_BEHIND
        | ONIG_SYN_VARIABLE_LEN_LOOK_BEHIND
        | ONIG_SYN_CAPTURE_ONLY_NAMED_GROUP
        | ONIG_SYN_ALLOW_MULTIPLEX_DEFINITION_NAME
        | ONIG_SYN_FIXED_INTERVAL_IS_GREEDY_ONLY
        | ONIG_SYN_ALLOW_INVALID_CODE_END_OF_RANGE_IN_CC
        | ONIG_SYN_WARN_CC_OP_NOT_ESCAPED
        | ONIG_SYN_ESC_P_WITH_ONE_CHAR_PROP
        | ONIG_SYN_WARN_REDUNDANT_NESTED_REPEAT
        | ONIG_SYN_WHOLE_OPTIONS,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

/// PROTOTYPE: opt-in syntax used only by the issue #44 research harness.
///
/// This preserves the normal Oniguruma syntax while allowing the two AST
/// constructs whose ECMAScript semantics the spike is evaluating. It is
/// deliberately hidden from generated public documentation and should be
/// removed or replaced by a reviewed API when the spike concludes.
#[doc(hidden)]
pub fn prototype_ecmascript_lookbehind_syntax() -> &'static OnigSyntaxType {
    static SYNTAX: OnceLock<OnigSyntaxType> = OnceLock::new();
    SYNTAX.get_or_init(|| {
        let mut syntax = OnigSyntaxOniguruma.clone();
        syntax.behavior |= FERRONI_SYN_ALLOW_CAPTURE_IN_NEGATIVE_LOOK_BEHIND
            | FERRONI_SYN_ALLOW_LOOK_AHEAD_IN_NEGATIVE_LOOK_BEHIND
            | FERRONI_SYN_UNMATCHED_BACKREF_MATCHES_EMPTY;
        syntax
    })
}

/// Ruby regular expressions (`Syntax::Ruby`).
pub static OnigSyntaxRuby: OnigSyntaxType = OnigSyntaxType {
    op: (SYN_GNU_REGEX_OP
        | ONIG_SYN_OP_QMARK_NON_GREEDY
        | ONIG_SYN_OP_ESC_OCTAL3
        | ONIG_SYN_OP_ESC_X_HEX2
        | ONIG_SYN_OP_ESC_X_BRACE_HEX8
        | ONIG_SYN_OP_ESC_O_BRACE_OCTAL
        | ONIG_SYN_OP_ESC_CONTROL_CHARS
        | ONIG_SYN_OP_ESC_C_CONTROL)
        & !ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END,
    op2: ONIG_SYN_OP2_QMARK_GROUP_EFFECT
        | ONIG_SYN_OP2_OPTION_RUBY
        | ONIG_SYN_OP2_QMARK_LT_NAMED_GROUP
        | ONIG_SYN_OP2_ESC_K_NAMED_BACKREF
        | ONIG_SYN_OP2_QMARK_LPAREN_IF_ELSE
        | ONIG_SYN_OP2_QMARK_TILDE_ABSENT_GROUP
        | ONIG_SYN_OP2_ESC_X_Y_TEXT_SEGMENT
        | ONIG_SYN_OP2_ESC_CAPITAL_R_GENERAL_NEWLINE
        | ONIG_SYN_OP2_ESC_CAPITAL_K_KEEP
        | ONIG_SYN_OP2_ESC_G_SUBEXP_CALL
        | ONIG_SYN_OP2_ESC_P_BRACE_CHAR_PROPERTY
        | ONIG_SYN_OP2_ESC_P_BRACE_CIRCUMFLEX_NOT
        | ONIG_SYN_OP2_PLUS_POSSESSIVE_REPEAT
        | ONIG_SYN_OP2_CCLASS_SET_OP
        | ONIG_SYN_OP2_ESC_CAPITAL_C_BAR_CONTROL
        | ONIG_SYN_OP2_ESC_CAPITAL_M_BAR_META
        | ONIG_SYN_OP2_ESC_V_VTAB
        | ONIG_SYN_OP2_ESC_H_XDIGIT
        | ONIG_SYN_OP2_ESC_U_HEX4,
    behavior: SYN_GNU_REGEX_BV
        | ONIG_SYN_ALLOW_INTERVAL_LOW_ABBREV
        | ONIG_SYN_DIFFERENT_LEN_ALT_LOOK_BEHIND
        | ONIG_SYN_CAPTURE_ONLY_NAMED_GROUP
        | ONIG_SYN_ALLOW_MULTIPLEX_DEFINITION_NAME
        | ONIG_SYN_FIXED_INTERVAL_IS_GREEDY_ONLY
        | ONIG_SYN_WARN_CC_OP_NOT_ESCAPED
        | ONIG_SYN_WARN_REDUNDANT_NESTED_REPEAT,
    options: ONIG_OPTION_NONE,
    meta_char_table: DEFAULT_META_CHAR_TABLE,
};

// === Default Syntax ===

static ONIG_DEFAULT_SYNTAX: RwLock<&OnigSyntaxType> = RwLock::new(&OnigSyntaxOniguruma);

#[cfg_attr(coverage_nightly, coverage(off))]
pub(crate) fn onig_get_default_syntax() -> &'static OnigSyntaxType {
    // Safety: the RwLock always holds a &'static ref
    *ONIG_DEFAULT_SYNTAX.read().unwrap()
}

/// Sets the default syntax, or Oniguruma's syntax for `None`, and returns 0.
/// Ferroni stores the value but never reads it: the POSIX and GNU wrappers that
/// use the default in C are not ported ([ADR-012](https://ferroni.dev/adr/012-posix-and-gnu-api-not-ported)),
/// and [`onig_new`](crate::regcomp::onig_new) takes its syntax as an argument.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_default_syntax(syntax: Option<&'static OnigSyntaxType>) -> i32 {
    let syntax = syntax.unwrap_or(&OnigSyntaxOniguruma);
    *ONIG_DEFAULT_SYNTAX.write().unwrap() = syntax;
    0
}

// === Syntax Manipulation Functions ===

/// Copies every field of `from` into `to`. The built-in syntaxes are immutable
/// statics, so copy one before changing it with the `onig_set_syntax_*`
/// functions.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_copy_syntax(to: &mut OnigSyntaxType, from: &OnigSyntaxType) {
    *to = from.clone();
}

/// Replaces the `op` operator flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_syntax_op(syntax: &mut OnigSyntaxType, op: u32) {
    syntax.op = op;
}

/// Replaces the `op2` operator flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_syntax_op2(syntax: &mut OnigSyntaxType, op2: u32) {
    syntax.op2 = op2;
}

/// Replaces the behavior flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_syntax_behavior(syntax: &mut OnigSyntaxType, behavior: u32) {
    syntax.behavior = behavior;
}

/// Replaces the option flags that `syntax` turns on for every pattern.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_syntax_options(syntax: &mut OnigSyntaxType, options: OnigOptionType) {
    syntax.options = options;
}

/// Returns the `op` operator flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_get_syntax_op(syntax: &OnigSyntaxType) -> u32 {
    syntax.op
}

/// Returns the `op2` operator flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_get_syntax_op2(syntax: &OnigSyntaxType) -> u32 {
    syntax.op2
}

/// Returns the behavior flags of `syntax`.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_get_syntax_behavior(syntax: &OnigSyntaxType) -> u32 {
    syntax.behavior
}

/// Returns the option flags that `syntax` turns on for every pattern.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_get_syntax_options(syntax: &OnigSyntaxType) -> OnigOptionType {
    syntax.options
}

// === Meta Char Setter (USE_VARIABLE_META_CHARS) ===

/// Sets one meta character of `syntax`. `what` names it with an
/// `ONIG_META_CHAR_*` constant, and `code` is its new value. Returns 0, or
/// `ONIGERR_INVALID_ARGUMENT` when `what` is unknown.
#[cfg_attr(coverage_nightly, coverage(off))]
pub fn onig_set_meta_char(syntax: &mut OnigSyntaxType, what: u32, code: OnigCodePoint) -> i32 {
    match what {
        ONIG_META_CHAR_ESCAPE => syntax.meta_char_table.esc = code,
        ONIG_META_CHAR_ANYCHAR => syntax.meta_char_table.anychar = code,
        ONIG_META_CHAR_ANYTIME => syntax.meta_char_table.anytime = code,
        ONIG_META_CHAR_ZERO_OR_ONE_TIME => syntax.meta_char_table.zero_or_one_time = code,
        ONIG_META_CHAR_ONE_OR_MORE_TIME => syntax.meta_char_table.one_or_more_time = code,
        ONIG_META_CHAR_ANYCHAR_ANYTIME => syntax.meta_char_table.anychar_anytime = code,
        _ => return ONIGERR_INVALID_ARGUMENT,
    }
    0
}