# CSS1 parser for a PEG parser generator.
# and a user command parser
# Doesn't support import statements.


STYLESHEET      ← (CDO / CDC)*  (RULESET/DECLARATIONS/COMMENT/ATRULE)* (CDO / CDC)*
RULESET         ← SELECTORS "{" DECLARATIONS? "}"
SELECTORS       ← SELECTOR ("," SELECTOR)*
SELECTOR        ← ( "*" / NAME ID? CLASS? PSEUDO_CLASS? /
                  ID CLASS? PSEUDO_CLASS? /
                  CLASS PSEUDO_CLASS? /
                  PSEUDO_CLASS )+ PSEUDO_ELEMENT* / PSEUDO_ELEMENT 
ATRULE          ← ATID (STRING / URL) ";" / ATID "{" DECLARATIONS "}" 
NAME            ← <IDENT>
DECLARATIONS    ← DECLARATION (';' DECLARATION)* ';'?
DECLARATION     ← NAME ":" EXPR PRIO? / COMMENT 
OPERATOR        ← '/' / ','
# UNARY_OPERATOR  ← '-' / '+'
PRIO            ← IMPORTANT
EXPR            ← TERM (OPERATOR TERM)*
TERM            ← STRING / PERCENTAGE / LENGTH / HEXCOLOR / URL / RGB / NUM / IDENT
~COMMENT        ←  "/*" (!("*/").)* "*/"
ATID            ← < "@" [a-zA-Z][-_a-zA-Z0-9]+ >
IMPORTANT       ← < "!" WS "important" >
IDENT           ← < [-_a-zA-Z][-_a-zA-Z0-9]* >
PERCENTAGE      ← < NUM > "%"
NUM             ← < [+-]*[0-9]+ / [0-9]* "." [0-9]+ >
LENGTH          ← NUM UNIT 
UNIT            ← <"pt" / "mm" / "pt" / "in" / "px" / "em" / "ex" >
PSEUDO_ELEMENT  ←  <":first-letter" / ":first-line" >
PSEUDO_CLASS    ←  <":hover" / ":link" / ":mark" / ":active" / ":visited" >
HEXCOLOR        ← "#" < ([0-9a-fA-F])+ > 
ID              ← "#" < IDENT >
CLASS           ← "." < IDENT >

# Raw string macro.
RAWSM(O,C)          ← O < (!(C).)* > C
# Escaped string macro.
ESCSM(O,C)          ← O < (!(C)STRCHAR)* > C
# String escapes
STRESC1      ← "\\" [nrtfv\'\\"\[\]\\]
STRESC2      ← "\\" [0-3] [0-7] [0-7]
STRESC3      ← "\\" [0-7] [0-7]*
STRESC4      ← "\\x" [0-9a-fA-F] [0-9a-fA-F]?
STRESC5      ← "\\u" [0-9a-fA-F]+
STRNOESC     ← (!('\\\\').)
STRCHAR      ←   STRESC1 / STRESC2 / STRESC3 / STRESC4 / STRESC5 / STRNOESC  
# Strings
STRING       ← ESCSM("\"", "\"") / ESCSM("'", "'")
URL                 ← "url(" STRING  ")"
RGB                 ← < "rgb("[ \t]*[0-9]+[ \t]* "," [ \t]*[0-9]+[ \t]* "," [ \t]*[0-9]+[ \t]*  ")" >
~WS                 ←   [ \t\n\r]*
CDO                 ←   "<!--"
CDC                 ←   "-->"
%whitespace         ←   [ \t\n\r]*
# %word             ←  [a-zA-Z][-+/*_a-zA-Z0-9]*