(module type-equal-unit mzscheme
  
  (require 
   "signatures.ss"
   "type-def-structs.ss"
   "effect-structs.ss"
   "planet-requires.ss"
   (lib "unit.ss")
   (lib "match.ss")
   (lib "67.ss" "srfi"))
  
  (provide (all-defined))
  
  (require-libs)
  (define-unit type-equal@
    (import type-structs^ subst^ effect-structs^)
    (export type-equal^)
    
    (define (rename a b)
      (match* (a b)
              [($ poly vs1 b1) ($ poly vs2 b2) (let ([vs* (map (lambda (v) (make-tvar (gensym v))) vs1)])
                                                 (list (subst-all (map list vs1 vs*) b1)
                                                       (subst-all (map list vs2 vs*) b2)))]
              [($ mu v1 b1) ($ mu v2 b2) (let ([v* (make-tvar (gensym v1))])
                                           (list (subst v1 v* b1)
                                                 (subst v2 v* b2)))]))
    
    (define (poly-equal? comp? p1 p2)
      (match (list p1 p2)
        [(($ poly v1 b1) ($ poly v2 b2))
         (and (= (length v1) (length v2))
              (apply comp? (rename p1 p2)))]))
    
    (define (mu-equal? comp? m1 m2)
      (match (list m1 m2)
        [(($ mu v1 b1) ($ mu v2 b2))
         (apply comp? (rename m1 m2))]))
    
    (define (opaque-ty-equal? _ m1 m2)
      (module-identifier=? (opaque-ty-pred m1) (opaque-ty-pred m2)))
    
    (define type-equal-rules 
      (add-equiv-rule
       opaque-ty? opaque-ty-equal?
       (add-equiv-rule
        mu? mu-equal?
        (add-equiv-rule
         poly? poly-equal?
         (add-equiv-rule/leaf set:set? set:equal? default-equiv-rules)))))
    
    (define tc-result-equal-rules
      (add-equiv-rule/leaf
       identifier? (lambda (a b) (eq? (syntax-e a) (syntax-e b)))
       type-equal-rules))
    
    (define type-equal? (make-equiv type-equal-rules))
    (define tc-result-equal? (make-equiv tc-result-equal-rules))
    
    (current-equiv-rules type-equal-rules)
    
    (define-syntax match*
      (syntax-rules ()
        [(match* (vars ...) [pats ... expr] ...)
         (match (list vars ...)
           [(pats ...) expr] ...)]))
    
    ;; FIXME - not done yet
    (define (effect-compare s t)
        (select-compare
         s t
         [true-effect? 0]
         [false-effect? 0]
         [latent-var-true-effect? 0]
         [latent-var-false-effect? 0]
         [restrict-effect? (type-compare (restrict-effect-t s) (restrict-effect-t t))
                           (symbol-compare (syntax-e (restrict-effect-v s) (restrict-effect-v t)))]
         [remove-effect? (type-compare (remove-effect-t s) (remove-effect-t t))
                         (symbol-compare (syntax-e (remove-effect-v s) (remove-effect-v t)))]
         [latent-restrict-effect? (type-compare (restrict-effect-t s) (restrict-effect-t t))]
         [latent-remove-effect? (type-compare (remove-effect-t s) (remove-effect-t t))]
         [var-true-effect? (symbol-compare (syntax-e (var-true-effect-v s) (var-true-effect-v t)))]         
         [var-false-effect? (symbol-compare (syntax-e (var-false-effect-v s) (var-false-effect-v t)))]         
         ))
    
    (define (type-compare s t)
      
      (define (arr-ty-compare s t)
        (match (list s t)
          [(($ arr dom1 rng1 rest1 thn-eff1 els-eff1) ($ arr dom2 rng2 rest2 thn-eff2 els-eff2))
           (refine-compare
            (list-compare type-compare dom1 dom2)
            (type-compare rest1 rest2)
            (type-compare rng1 rng2)
            (list-compare effect-compare thn-eff1 thn-eff2)
            (list-compare effect-compare els-eff1 els-eff2))]))
      (define (union-elems/in-order s) (set:elements (union-elems s)))
      (select-compare 
       s t
       [dynamic? 0]
       [univ? 0]       
       [tvar? (symbol-compare (tvar-name s) (tvar-name t))]
       [base-type? (symbol-compare (base-type-name s) (base-type-name t))]
       [value? (default-compare (value-v s) (value-v t))]
       [poly? (apply type-compare (rename s t))]
       [mu? (apply type-compare (rename s t))]
       [values-ty? (list-compare type-compare (values-ty-types s) (values-ty-types t))]
       [funty? (list-compare arr-ty-compare (funty-arities s) (funty-arities t))]
       [pair-ty? (type-compare (pair-ty-car s) (pair-ty-car t))
                 (type-compare (pair-ty-cdr s) (pair-ty-cdr t))]
       [vec? (type-compare (vec-elem s) (vec-elem t))]
       [struct-ty? (symbol-compare (struct-ty-name s) (struct-ty-name t))
                   (type-compare (struct-ty-parent s) (struct-ty-parent t))
                   (list-compare type-compare (struct-ty-flds s) (struct-ty-flds t))]                     
       [union? (list-compare type-compare
                             (union-elems/in-order s)
                             (union-elems/in-order t))]
       [opaque-ty? (let* ([p1 (opaque-ty-pred s)]
                          [p2 (opaque-ty-pred t)]
                          [p1* (syntax-e p1)]
                          [p2* (syntax-e p2)])
                     (unless
                       (eq? (eq? p1* p2*)
                            (module-identifier=? p1 p2))
                       (error 'typecheck "internal error in type-compare"))
                     (symbol-compare p1* p2*))]
       ))
    
    (define (type<? a b)
      (<? type-compare a b))
    )
  
  
  
  
  )