@top Problem { statement* }

statement {
  ProblemDeclaration {
    ckw<"problem"> QualifiedName "."
  } |
  ClassDefinition {
    ckw<"abstract">? ckw<"class"> RelationName
    (ckw<"extends"> sep<",", RelationName>)?
    (ClassBody {  "{" ReferenceDeclaration* "}" } | ".")
  } |
  EnumDefinition {
    ckw<"enum"> RelationName
    (EnumBody { "{" sep<",", UniqueNodeName> "}" } | ".")
  } |
  PredicateDefinition {
    (ckw<"error"> ckw<"pred">? | ckw<"pred">) RelationName ParameterList<Parameter>?
    PredicateBody { ("<->" sep<OrOp, Conjunction>)?  "." }
  } |
  Assertion {
    ckw<"default">? (NotOp | UnknownOp)? RelationName
    ParameterList<AssertionArgument> (":" LogicValue)? "."
  } |
  NodeValueAssertion {
    UniqueNodeName ":" Constant "."
  } |
  UniqueDeclaration {
    ckw<"unique"> sep<",", UniqueNodeName> "."
  } |
  ScopeDeclaration {
    ckw<"scope"> sep<",", ScopeElement> "."
  }
}

ReferenceDeclaration {
  (kw<"refers"> | kw<"contains">)?
  RelationName
  RelationName
  ( "[" Multiplicity? "]" )?
  (kw<"opposite"> RelationName)?
  ";"?
}

Parameter { RelationName? VariableName }

Conjunction { ("," | Literal)+ }

OrOp { ";" }

Literal { NotOp? Atom }

Atom { RelationName ParameterList<Argument>? }

Argument { VariableName | Constant }

AssertionArgument { NodeName | StarArgument | Constant }

Constant { Real | String }

LogicValue {
  ckw<"true"> | ckw<"false"> | ckw<"unknown"> | ckw<"error">
}

ScopeElement { RelationName ("=" | "+=") Multiplicity }

Multiplicity { (IntMult "..")? (IntMult | StarMult)}

RelationName { QualifiedName }

UniqueNodeName { QualifiedName }

VariableName { QualifiedName }

NodeName { QualifiedName }

QualifiedName { identifier ("::" identifier)* }

kw<term> { @specialize[@name={term}]<identifier, term> }

ckw<term> { @extend[@name={term}]<identifier, term> }

ParameterList<content> { "(" sep<",", content> ")" }

sep<separator, content> { sep1<separator, content>? }

sep1<separator, content> { content (separator content?)* }

@skip { LineComment | BlockComment | whitespace }

@tokens {
  whitespace { std.whitespace+ }

  LineComment { ("//" | "%") ![\n]* }

  BlockComment { "/*" blockCommentRest }

  blockCommentRest { ![*] blockCommentRest | "*" blockCommentAfterStar }

  blockCommentAfterStar { "/" | "*" blockCommentAfterStar | ![/*] blockCommentRest }

  @precedence { BlockComment, LineComment }

  identifier { $[A-Za-z_] $[a-zA-Z0-9_]* }

  int { $[0-9]+ }

  IntMult { int }

  StarMult { "*" }

  Real { "-"? (exponential | int ("." (int | exponential))?) }

  exponential { int ("e" | "E") ("+" | "-")? int }

  String {
    "'" (![\\'\n] | "\\" ![\n] | "\\\n")+ "'" |
    "\"" (![\\"\n] | "\\" (![\n] | "\n"))* "\""
  }

  NotOp { "!" }

  UnknownOp { "?" }

  StarArgument { "*" }

  "{" "}" "(" ")" "[" "]" "." ".." "," ":" "<->"
}

@detectDelim