(* µLang v1 grammar — https://ulang.dev/spec/v1/syntax
   Reference implementation: ulang-lite 61af4281ed6fd09d5f9f2100d3960630d757ae49 (MIT) *)

file          = { contract } ;
contract      = "CONTRACT" name "{"
                  [ mode ] [ context ] [ trigger ]
                  [ guarantee ] [ prohibition ] [ observability ]
                "}" ;
mode          = "ENFORCEMENT_MODE" ":"
                ( "enforced" | "ENFORCED" | "advisory" | "ADVISORY" | "audit" | "AUDIT" ) ;

context       = "CONTEXT" "{" { entities } [ constants ] "}" ;
entities      = "ENTITIES" [ name ] "{" field { field } "}" ;
field         = name ":" type ;
type          = "int" | "float" | "bool" | "string"
              | name [ "<" type { "," type } ">" ] ;
constants     = "CONSTANTS" [ name ] "{" { constant } "}" ;
constant      = name ":" type ( "==" | "=" ) literal [ source ] ;

trigger       = "TRIGGER" "{" event { event } "}" ;
event         = name [ "(" [ args ] ")" ] [ "WHEN" condition ] ;

guarantee     = "GUARANTEE" "{" { "ENSURE" clause } "}" ;
prohibition   = "PROHIBITION" "{" { "FORBID" clause } "}" ;
clause        = name [ "(" [ args ] ")" ] [ "WHEN" condition ] [ source ] ;

observability = "OBSERVABILITY" "{" { "LOG" string "ON" word } "}" ;

source        = "[" "SOURCE:" text "]" ;

condition     = conjunction { "OR" conjunction } ;
conjunction   = primary { "AND" primary } ;
primary       = "(" condition ")"
              | value [ op value ]
              | word "=" value ;                  (* assignment: outside the subset *)
op            = "==" | "!=" | "<=" | ">=" | "<" | ">" ;
value         = term { "-" integer } ;            (* subtraction: outside the subset *)
term          = integer | float | string | boolean
              | word [ "(" [ args ] ")" ]         (* a call: outside the subset *)
              | "(" value ")" ;                   (* right-hand side only *)
args          = value { "," value } ;
literal       = integer | float | string | boolean ;