less.ebnf

#  lexer token
semi = ';';
dot = '.';
comma = ',';
colon = ':';
left_parenthesis = '(';
right_parenthesis = ')';
plus = '+';
minus = '-';
less_than = '<';
at ='@';
left_square_bracket = '[';
right_square_bracket = ']';
reverse_solidus = "\\";
left_curly_bracket = "{";
right_curly_bracket = "}";
forswrd_slash = "/";
equal = "=";
asterisk = "*";
wave = "~";
dashmatch = "|=";
includes = "~=";
exclude = "^=";
all_match = "*=";
CDOToken = "<!--";
CDCTOken = "-->";
more_than = ">";
white_space = ? white space characters ? ;
all_characters = ? all visible characters?;
digital = "0" | "1" | "2" | "3" |"4" |"5" | "6" | "7" | "8" | "9";


# combaintion token
str = single_str | double_str;
single_str = "'" , {all_characters - "'"} ,"'";
double_str = '"', {all_characters - '"'},'"';

operator = plus | minus | asterisk | forswrd_slash;

number = [ "-" | "+" | "."], digit ,[ {digit} ], ["e" | "E"];

ident = all_characters, [{all_characters | digit}];

percentage = digital, "%";
# 14px 32rem ..
dimension = digital, ident;

comment = "/*", all_characters , "*/";

function_token = ident , "(";

at_keyword = at,ident;
hash_token = "#" , ident;

#  有点和function token 是一样的
url_token = "url(", all_characters, ")";

# grammer 
style_sheets = rule_list | 
rule = selector_list , declaration_list;
# @media() {};
# @import();
# @keyframes slidein {}
at_rule = at,ident, all_characters
simple_at_rule = at_charset,
at_charset = at,'charset' ,str;
at_namespace = at,'namespace',ident,[url_token];
at_media = at,ident, "(", 
at_import = at,str , [url | str] , [layer | layer(ident)] , import_conditions;
import_conditions = ["supports(", [support_condition | declaration] , ")"];

# @abc str
at_select_two = at,ident, ,";";
# @a
at_select_one = at ,ident ,[str | declaration_list | ({ident} ,declaration_list)] ;
container_condition = 

declaration_list = "{",[{declaration}],"}";
declaration = property , ":" , expression, {'important'};
property = [asterisk] , ident;

selector_list = simple_selector,[{white_space|",",simple_selector}]
simple_selector = class_selector | id_selector | asterisk_selector | element_selector
                    pseudo_selector | target_selector;

class_selector = dot,ident;
id_selector = hash_token;
asterisk_selector = asterisk;
element_selector = ident;
children_selector = simple_selector ,">", simple_selector;
borther_selector = simple_selector, "+", simple_selector;
every_selector = simple_selector, "~", simple_selector;
target_selector = "[",ident,["="|"~="|"|="|"^="|"$="|"*=",ident] "]";
pseudo_selector = ":", [":"],ident | call_expr;



term = digit | dimension | str | ident | url_token | dot | colon 
        | hash_token | plus | minus | asterisk | forswrd_slash | percentage 
        | ("(",term,")") | variable_declaration | call_expr;

# @a: 123 + 12px;
# @a: {};
variable_declaration = at_keyword,expression | 
# a() 
call_expr = function_token,expression,")";

# 1 + 2  
# 1 + a()
expression = term, { comma | forswrd_slash | equal, term };

# media query start
not = "not";
only = "only";
media_query = media_condition | ([not | only], media_type [and, media_condition_without_or]);
media_type = ident;
media_condition = media_not | madia_in_parens [{media_and} | {media_or}]
media_condition_without_or = media_not | media_in_parens , {media_and};
media_not = not, media_in_parens;
media_and = and, media_in_parens;
media_or = or,media_in_parens;
media_in_parens = media_condition | media_feature | general_enclose;
media_feature = [mf_plain | mf_boolean | mf_range];
mf_plain = mf_name : mf_value;
mf_boolean = mf_name;
mf_range = (mf_name,mf_comparision,mf_value)|
            (mf_value,mf_comparision,mf_name)|
            (mf_value,mf_lt,mf_name,mf_lt,mf_value)|
            (mf_value,mf_gt,mf_name,mf_gt,mf_value);
mf_name = ident;
mf_value = number | dimension, ident | ratio;
mf_lt = "<",["="];
mf_gt = ">",["="];
mf_eq = "=";
mf_comparision = mf_lf | mf_gt |mf_eq;
            


# media query end