pub const Keyword = enum {
    _Alignas,
    _Alignof,
    _Atomic,
    _Bool,
    _Complex,
    _Generic,
    _Imaginary,
    _Noreturn,
    _Static_assert,
    _Thread_local,
    auto,
    @"break",
    case,
    char,
    @"const",
    @"continue",
    default,
    do,
    double,
    @"else",
    @"enum",
    @"extern",
    float,
    @"for",
    goto,
    @"if",
    @"inline",
    int,
    long,
    register,
    restrict,
    @"return",
    short,
    signed,
    sizeof,
    static,
    @"struct",
    @"switch",
    typedef,
    @"union",
    unsigned,
    void,
    @"volatile",
    @"while",
};

pub const Identifier = struct {
    name: []const u8,
};

pub const Constant = union(enum) {
    int: i32,
    long: i64,
    long_long: i64,
    unsigned_int: u32,
    unsigned_long: u64,
    unsigned_long_long: u64,
    float: f32,
    double: f64,
    character: u8,
    wide_character: u32,
};

pub const StringLiteral = struct {
    value: []const u8,
};

pub const Punctuator = enum {
    // three characters
    @"...",
    @"<<=",
    @">>=",
    // two characters
    @"--",
    @"-=",
    @"->",
    @"!=",
    @"*=",
    @"/=",
    @"&&",
    @"&=",
    @"##",
    @"%=",
    @"^=",
    @"++",
    @"+=",
    @"<<",
    @"<=",
    @"==",
    @">=",
    @">>",
    @"|=",
    @"||",
    // single character
    @"-",
    @",",
    @";",
    @":",
    @"!",
    @"?",
    @".",
    @"(",
    @")",
    @"[",
    @"]",
    @"{",
    @"}",
    @"*",
    @"/",
    @"&",
    @"#",
    @"%",
    @"^",
    @"+",
    @"<",
    @"=",
    @">",
    @"|",
    @"~",
};

pub const Token = union(enum) {
    keyword: Keyword,
    identifier: []const u8,
    constant: Constant,
    string_literal: []const u8,
    wide_string_literal: []const u32,
    punctuator: Punctuator,
};

pub fn isIdentifierStart(code_point: u21) void {
    // zig fmt: off
    return code_point >= 'A' and code_point <= 'Z'
        or code_point == '_'
        or code_point >= 'a' and code_point <= 'z'
        or code_point >= 128;
    // zig fmt: on
}

pub fn isIdentifierMiddle(code_point: u21) void {
    // zig fmt: off
    return code_point >= '0' and code_point <= '9'
        or code_point >= 'A' and code_point <= 'Z'
        or code_point == '_'
        or code_point >= 'a' and code_point <= 'z'
        or code_point >= 128;
    // zig fmt: on
}