#lang racket/base

(require "../version-case/version-case.rkt"
         (for-syntax racket/base))



(version-case
  [(version<= "5.2.0.900" (version))

   ;; Parsing Racket 5.1.2 bytecode structures into our own structures.
   (require "path-rewriter.rkt"
            "../compiler/expression-structs.rkt"
            "../compiler/lexical-structs.rkt"
            "../parameters.rkt"
            "../get-module-bytecode.rkt"
            syntax/modresolve
            compiler/zo-parse
            racket/path
            racket/match
            racket/list)


   (provide parse-bytecode)



   ;; current-module-path-index-resolver: (module-path-index (U Path #f) -> (U Symbol Path)) -> void
   ;; The module path index resolver figures out how to translate module path indices to module names.
   (define current-module-path-index-resolver 
     (make-parameter 
      (lambda (mpi relative-to)
        (cond
         [(eq? mpi #f)
          (current-module-path)]
         [(self-module-path-index? mpi)
          (current-module-path)]
         [else
          (resolve-module-path-index mpi relative-to)]))))


   (define current-module-path-resolver 
     (make-parameter 
      (lambda (module-path relative-to)
        (resolve-module-path module-path relative-to))))



   (define (self-module-path-index? mpi)
     (let-values ([(x y) (module-path-index-split mpi)])
       (and (eq? x #f)
            (eq? y #f))))


   (define (explode-module-path-index mpi)
     (let-values ([(x y) (module-path-index-split mpi)])
       (cond
        [(module-path-index? y)
         (cons x (explode-module-path-index y))]
        [else
         (list x y)])))
   



   ;; seen-closures: (hashof symbol -> symbol)
   ;; As we're parsing, we watch for closure cycles.  On any subsequent time where
   ;; we see a closure cycle, we break the cycle by generating an EmptyClosureReference.
   ;; The map is from the gen-id to the entry-point label of the lambda.
   (define seen-closures (make-parameter (make-hasheq)))






   ;; Code is copied-and-pasted from compiler/decompile.  Maps the primval ids to their respective
   ;; symbolic names.
   (define primitive-table
     ;; Figure out number-to-id mapping for kernel functions in `primitive'
     (let ([bindings
            (let ([ns (make-base-empty-namespace)])
              (parameterize ([current-namespace ns])
                (namespace-require ''#%kernel)
                (namespace-require ''#%unsafe)
                (namespace-require ''#%flfxnum)
                (namespace-require ''#%futures)
                (for/list ([l (namespace-mapped-symbols)])
                          (cons l (with-handlers ([exn:fail? (lambda (x) 
                                                               #f)])
                                    (compile l))))))]
           [table (make-hash)])
       (for ([b (in-list bindings)])
            (let ([v (and (cdr b)
                          (zo-parse (let ([out (open-output-bytes)])
                                      (write (cdr b) out)
                                      (close-output-port out)
                                      (open-input-bytes (get-output-bytes out)))))])
              (let ([n (match v
                         [(struct compilation-top (_ prefix (struct primval (n)))) n]
                         [else #f])])
                (hash-set! table n (car b)))))
       table))








   ;; parse-bytecode: (U Input-Port Path) -> Expression
   ;;
   ;; Given an input port, assumes the input is the byte representation of compiled-code.
   ;;
   ;; Given a path, assumes the path is for a module.  It gets the module bytecode, and parses
   ;; that.
   ;;
   ;; TODO: this may be doing too much work.  It doesn't quite feel like the right elements
   ;; are being manipulated here.
   (define (parse-bytecode in)
     (cond
      [(input-port? in)
       (parameterize ([seen-closures (make-hasheq)])
         (let ([compilation-top (zo-parse in)])
           (parse-top compilation-top)))]
      
      [(compiled-expression? in)
       (let ([op (open-output-bytes)])
         (write in op)
         (parse-bytecode (open-input-bytes (get-output-bytes op))))]

      [(path? in)
       (let*-values ([(normal-path) (normalize-path in)]
                     [(base file-path dir?) (split-path normal-path)])
         (parameterize ([current-module-path normal-path]
                        [current-directory (cond [(path? base)
                                                  base]
                                                 [else
                                                  (error 'parse-bytecode)])])
           (define module-bytecode (get-module-bytecode normal-path))
           (parse-bytecode (open-input-bytes module-bytecode))))]    
      [else
       (error 'parse-bytecode "Don't know how to parse from ~e" in)]))


   




   (define (parse-top a-top)
     (match a-top
       [(struct compilation-top (max-let-depth prefix code))
        (maybe-fix-module-name
         (make-Top (parse-prefix prefix) 
                   (parse-top-code code)))]))



   ;; maybe-fix-module-name: expression -> expression
   ;; When we're compiling a module directly from memory, it doesn't have a file path.
   ;; We rewrite the ModuleLocator to its given name.
   (define (maybe-fix-module-name exp)
     (match exp
       [(struct Top (top-prefix 
                     (struct Module ((and name (? symbol?))
                                     (struct ModuleLocator ('self 'self))
                                     module-prefix
                                     module-requires
                                     module-provides
                                     module-code))))
        (make-Top top-prefix
                  (make-Module name
                               (make-ModuleLocator name name) (current-module-path)
                               module-prefix
                               module-requires
                               module-provides
                               module-code))]
       [else
        exp]))



   (define (parse-prefix a-prefix)
     (match a-prefix
       [(struct prefix (num-lifts toplevels stxs))
        (make-Prefix 
         (append (map parse-prefix-toplevel toplevels)
                 (map (lambda (x) #f) stxs)
                 (if (empty? stxs) empty (list #f))
                 (build-list num-lifts (lambda (i) #f))))]))


   ;; parse-top-code: (U form Any -> Expression)
   (define (parse-top-code code)
     (cond
      [(form? code)
       (parse-form code)]
      [else
       (make-Constant code)]))


   ;; parse-prefix-toplevel: (U #f symbol global-bucket module-variable) -> (U False Symbol GlobalBucket ModuleVariable)
   (define (parse-prefix-toplevel a-toplevel)
     (cond
      [(eq? a-toplevel #f)
       #f]
      [(symbol? a-toplevel)
       a-toplevel]
      [(global-bucket? a-toplevel)
       (make-GlobalBucket (global-bucket-name a-toplevel))]
      [(module-variable? a-toplevel)
       (let ([resolver (current-module-path-index-resolver)])
         (make-ModuleVariable (module-variable-sym a-toplevel)
                              (let ([resolved-path-name
                                     (resolver (module-variable-modidx a-toplevel) (current-module-path))])
                                (wrap-module-name resolved-path-name))))]))

   (define (wrap-module-name resolved-path-name)
     (cond
      [(symbol? resolved-path-name)
       (make-ModuleLocator resolved-path-name resolved-path-name)]
      [(path? resolved-path-name)
       (let ([rewritten-path (rewrite-path resolved-path-name)])
         (cond
          [(symbol? rewritten-path)
           (make-ModuleLocator (rewrite-path resolved-path-name)
                               (normalize-path resolved-path-name))]
          [else
           (error 'wrap-module-name "Unable to resolve module path ~s."
                  resolved-path-name)]))]))
   
   



   ;; parse-form: form -> (U Expression)
   (define (parse-form a-form)
     (cond
      [(def-values? a-form)
       (parse-def-values a-form)]

      [(def-syntaxes? a-form)
       (parse-def-syntaxes a-form)]
      
      [(req? a-form)
       (parse-req a-form)]
      
      [(seq? a-form)
       (parse-seq a-form)]
      
      [(splice? a-form)
       (parse-splice a-form)]
      
      [(mod? a-form)
       (parse-mod a-form)]
      
      [(expr? a-form)
       (parse-expr a-form)]

      [else
       (error 'parse-form "~s" a-form)]))


   ;; parse-def-values: def-values -> Expression
   (define (parse-def-values form)
     (match form 
       ;; Explicit check for inline-variant first, since that's the only place
       ;; it apppears
       [(struct def-values (ids (struct inline-variant (direct inline))))
        (make-DefValues (map parse-toplevel ids)
                        (parse-expr direct))]
       
       [(struct def-values (ids rhs))
        (make-DefValues (map parse-toplevel ids)
                        (parse-expr-seq-constant rhs))]))



   (define (parse-def-syntaxes form)
     ;; Currently, treat def-syntaxes as a no-op.  The compiler will not produce
     ;; syntax transformers.
     (make-Constant (void)))



   (define (parse-req form)
     (let ([resolver (current-module-path-resolver)])
       (match form
         [(struct req (reqs dummy))
          (let ([require-statement (parse-req-reqs reqs)])
            (match require-statement
              [(list '#%require (and (? module-path?) path))
               (let ([resolved-path ((current-module-path-resolver) path (current-module-path))])
                 (cond
                  [(symbol? resolved-path)
                   (make-Require (make-ModuleLocator resolved-path resolved-path))]
                  [(path? resolved-path)
                   (let ([rewritten-path (rewrite-path resolved-path)])
                     (cond
                      [(symbol? rewritten-path)
                       (make-Require (make-ModuleLocator rewritten-path
                                                         (normalize-path resolved-path)))]
                      [else
                       (printf "Internal error: I don't know how to handle the require for ~s" require-statement)
                       (error 'parse-req)]))]
                  [else
                   (printf "Internal error: I don't know how to handle the require for ~s" require-statement)
                   (error 'parse-req)]))]
              [else
               (printf "Internal error: I don't know how to handle the require for ~s" require-statement)
               (error 'parse-req)]))])))
   
   ;; parse-req-reqs: (stx -> (listof ModuleLocator))
   (define (parse-req-reqs reqs)
     (match reqs
       [(struct stx (encoded))
        (unwrap-wrapped encoded)]))

   (define (unwrap-wrapped encoded)
     (cond [(wrapped? encoded)
            (match encoded 
              [(struct wrapped (datum wraps certs))
               (unwrap-wrapped datum)])]
           [(pair? encoded)
            (cons (unwrap-wrapped (car encoded))
                  (unwrap-wrapped (cdr encoded)))]
           [(null? encoded)
            null]
           [else
            encoded]))




   ;; parse-seq: seq -> Expression
   (define (parse-seq form)
     (match form
       [(struct seq (forms))
        (make-Seq (map parse-form-item forms))]))


   ;; parse-form-item: (U form Any) -> Expression
   (define (parse-form-item item)
     (cond
      [(form? item)
       (parse-form item)]
      [else
       (make-Constant item)]))


   ;; parse-splice: splice -> Expression
   (define (parse-splice form)
     (match form
       [(struct splice (forms))
        (make-Splice (map parse-splice-item forms))]))


   ;; parse-splice-item: (U form Any) -> Expression
   (define (parse-splice-item item)
     (cond
      [(form? item)
       (parse-form item)]
      [else
       (make-Constant item)]))


   ;; parse-mod: mod -> Expression
   (define (parse-mod form)
     (match form
       [(struct mod (name srcname self-modidx prefix provides requires
                          body syntax-body unexported max-let-depth dummy lang-info
                          internal-context))
        (let ([self-path 
               ((current-module-path-index-resolver)
                self-modidx
                (current-module-path))])
          (cond
           [(symbol? self-path)
            (make-Module name
                         (make-ModuleLocator self-path self-path)
                         (parse-prefix prefix)
                         (parse-mod-requires self-modidx requires)
                         (parse-mod-provides self-modidx provides)
                         (parse-mod-body body))]
           [else
            (let ([rewritten-path (rewrite-path self-path)])
              (cond
               [(symbol? rewritten-path)
                (make-Module name
                             (make-ModuleLocator rewritten-path 
                                                 (normalize-path self-path))
                             (parse-prefix prefix)
                             (parse-mod-requires self-modidx requires)
                             (parse-mod-provides self-modidx provides)
                             (parse-mod-body body))]
               [else
                (error 'parse-mod "Internal error: unable to resolve module path ~s" self-path)]))]))]))


   ;; parse-mod-requires: module-path-index (listof (pair (U Integer #f) (listof module-path-index))) -> (listof ModuleLocator)
   (define (parse-mod-requires enclosing-module-path-index requires)
     ;; We only care about phase 0 --- the runtime.
     (let ([resolver (current-module-path-index-resolver)])
       (let loop ([requires requires])
         (cond
          [(empty? requires)
           empty]
          [(= (car (first requires))
              0)
           (map (lambda (m) 
                  (let ([enclosing-path (resolver enclosing-module-path-index (current-module-path))])
                    (cond
                     [(symbol? enclosing-path)
                      (wrap-module-name (resolver m (current-module-path)))]
                     [(path? enclosing-path)
                      (wrap-module-name (resolver m enclosing-path))])))
                (cdr (first requires)))]
          [else
           (loop (rest requires))]))))



   (define (parse-mod-provides enclosing-module-path-index provides)
     (let* ([resolver
             (current-module-path-index-resolver)]
            [enclosing-path
             (resolver enclosing-module-path-index (current-module-path))]
            [subresolver
             (lambda (p)
               (cond
                [(symbol? enclosing-path)
                 (wrap-module-name (resolver p (current-module-path)))]
                [(path? enclosing-path)
                 (wrap-module-name (resolver p enclosing-path))]))])
       (let loop ([provides provides])
         (cond
          [(empty? provides)
           empty]
          [(= (first (first provides)) 0)
           (let ([provided-values (second (first provides))])
             (for/list ([v provided-values])
                       (match v
                         [(struct provided (name src src-name nom-mod
                                                 src-phase protected?))
                          (make-ModuleProvide src-name name (subresolver src))])))]
          [else
           (loop (rest provides))]))))






   ;; parse-mod-body: (listof (or/c form? any/c)) -> Expression
   (define (parse-mod-body body)
     (let ([parse-item (lambda (item)
                         (cond
                          [(form? item)
                           (parse-form item)]
                          [else
                           (make-Constant item)]))])
       (make-Splice (map parse-item body))))



   (define (make-lam-label)
     (make-label 'lamEntry))
   
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

   (define (parse-expr expr)
     (cond
      [(lam? expr)
       (parse-lam expr (make-lam-label))]
      [(closure? expr)
       (parse-closure expr)]
      [(case-lam? expr)
       (parse-case-lam expr)]
      [(let-one? expr)
       (parse-let-one expr)]
      [(let-void? expr)
       (parse-let-void expr)]
      [(install-value? expr)
       (parse-install-value expr)]
      [(let-rec? expr)
       (parse-let-rec expr)]
      [(boxenv? expr)
       (parse-boxenv expr)]
      [(localref? expr)
       (parse-localref expr)]
      [(toplevel? expr)
       (parse-toplevel expr)]
      [(topsyntax? expr)
       (parse-topsyntax expr)]
      [(application? expr)
       (parse-application expr)]
      [(branch? expr)
       (parse-branch expr)]
      [(with-cont-mark? expr)
       (parse-with-cont-mark expr)]
      [(beg0? expr)
       (parse-beg0 expr)]
      [(varref? expr)
       (parse-varref expr)]
      [(assign? expr)
       (parse-assign expr)]
      [(apply-values? expr)
       (parse-apply-values expr)]
      [(primval? expr)
       (parse-primval expr)]))

   (define (parse-lam expr entry-point-label)
     (match expr
       [(struct lam (name flags num-params param-types rest? closure-map closure-types toplevel-map max-let-depth body))
        (let ([lam-name (extract-lam-name name)])
          (make-Lam lam-name 
                    num-params 
                    rest?
                    (parse-expr-seq-constant body)
                    (vector->list closure-map)
                    entry-point-label))]))
   

   ;; parse-closure: closure -> (U Lam EmptyClosureReference)
   ;; Either parses as a regular lambda, or if we come across the same closure twice,
   ;; breaks the cycle by creating an EmptyClosureReference with the pre-existing lambda
   ;; entry point.
   (define (parse-closure expr)
     (match expr
       [(struct closure (code gen-id))
        (let ([seen (seen-closures)])
          (cond
           [(hash-has-key? seen gen-id)
            (match code
              [(struct lam (name flags num-params param-types rest? closure-map closure-types toplevel-map max-let-depth body))
               (let ([lam-name (extract-lam-name name)])
                 (make-EmptyClosureReference lam-name 
                                             num-params 
                                             rest?
                                             (hash-ref seen gen-id)))])]
           [else
            (let ([fresh-entry-point (make-lam-label)])
              (hash-set! seen gen-id fresh-entry-point)
              (parse-lam code fresh-entry-point))]))]))



   ;; extract-lam-name: (U Symbol Vector) -> (U Symbol LamPositionalName)
   (define (extract-lam-name name)
     (cond
      [(symbol? name)
       name]
      [(vector? name)
       (match name
         [(vector (and (? symbol?) sym)
                  (and (? path?) source) 
                  (and (? number?) line)
                  (and (? number?) column)
                  (and (? number?) offset)
                  (and (? number?) span)
                  _)
          (let ([try-to-rewrite (rewrite-path source)])
            (make-LamPositionalName sym
                                    (if try-to-rewrite
                                        (symbol->string try-to-rewrite)
                                        (path->string source))
                                    line
                                    column 
                                    offset
                                    span))]
         [(vector (and (? symbol?) sym)
                  (and (? symbol?) source) 
                  (and (? number?) line)
                  (and (? number?) column)
                  (and (? number?) offset)
                  (and (? number?) span)
                  _)
          (make-LamPositionalName sym
                                  (symbol->string source)
                                  line
                                  column 
                                  offset
                                  span)]
         [else
          (string->symbol (format "~s" name))])]
      [else
       'unknown
       ;; The documentation says that the name must be a symbol or vector, but I'm seeing cases
       ;; where it returns the empty list when there's no information available.
       ]))




   (define (parse-case-lam exp)
     (match exp
       [(struct case-lam (name clauses))
        (let ([case-lam-label (make-lam-label)])
          (make-CaseLam (extract-lam-name name)
                        (map (lambda (l) 
                               (cond
                                [(closure? l)
                                 (parse-closure l)]
                                [else
                                 (parse-lam l (make-lam-label))]))
                             clauses)
                        case-lam-label))]))


   (define (parse-let-one expr)
     (match expr
       [(struct let-one (rhs body flonum? unused?))
        ;; fixme: use flonum? and unused? to generate better code.
        (make-Let1 (parse-expr-seq-constant rhs)
                   (parse-expr-seq-constant body))]))


   ;; parse-expr-seq-constant: (U expr seq Any) -> Expression
   (define (parse-expr-seq-constant x)
     (cond
      [(expr? x) (parse-expr x)]
      [(seq? x) (parse-seq x)]
      [else (make-Constant x)]))


   (define (parse-let-void expr)
     (match expr
       [(struct let-void (count boxes? body))
        (make-LetVoid count (parse-expr-seq-constant body) boxes?)]))


   (define (parse-install-value expr)
     (match expr
       [(struct install-value (count pos boxes? rhs body))
        (make-Seq (list (make-InstallValue count pos (parse-expr-seq-constant rhs) boxes?)
                        (parse-expr-seq-constant body)))]))


   (define (parse-let-rec expr)
     (match expr
       [(struct let-rec (procs body))
        (make-LetRec (map (lambda (p) (parse-lam p (make-lam-label)))
                          procs)
                     (parse-expr-seq-constant body))]))

   (define (parse-boxenv expr)
     (match expr
       [(struct boxenv (pos body))
        (make-BoxEnv pos (parse-expr-seq-constant body))]))


   (define (parse-localref expr)
     (match expr
       [(struct localref (unbox? pos clear? other-clears? flonum?))
        ;; FIXME: we should use clear? at the very least: as I understand it,
        ;; this is here to maintain safe-for-space behavior.
        ;; We should also make use of flonum information to generate better code.
        (make-LocalRef pos unbox?)]))


   (define (parse-toplevel expr)
     (match expr
       ;; FIXME: we should also keep track of const? and ready? to produce better code, and to
       ;; do the required runtime checks when necessary (const?=#f, ready?=#f)
       [(struct toplevel (depth pos const? ready?))
        (make-ToplevelRef depth
                          pos
                          const?
                          (if (and (not const?) (not ready?))
                              #t
                              #f))]))


   (define (parse-topsyntax expr)
     ;; We should not get into this because we're only parsing the runtime part of
     ;; the bytecode.  Treated as a no-op.
     (make-Constant (void)))


   (define (parse-application expr)
     (match expr
       [(struct application (rator rands))
        (make-App (parse-application-rator rator)
                  (map parse-application-rand rands))]))

   (define (parse-application-rator rator)
     (cond
      [(expr? rator)
       (parse-expr rator)]
      [(seq? rator)
       (parse-seq rator)]
      [else
       (make-Constant rator)]))

   (define (parse-application-rand rand)
     (cond
      [(expr? rand)
       (parse-expr rand)]
      [(seq? rand)
       (parse-seq rand)]
      [else
       (make-Constant rand)]))


   (define (parse-branch expr)
     (match expr
       [(struct branch (test then else))
        (make-Branch (parse-expr-seq-constant test)
                     (parse-expr-seq-constant then)
                     (parse-expr-seq-constant else))]))


   (define (parse-with-cont-mark expr)
     (match expr
       [(struct with-cont-mark (key val body))
        (make-WithContMark (parse-expr-seq-constant key)
                           (parse-expr-seq-constant val)
                           (parse-expr-seq-constant body))]))

   (define (parse-beg0 expr)
     (match expr
       [(struct beg0 (seq))     
        (make-Begin0 (map parse-expr-seq-constant seq))]))


   (define (parse-varref expr)
     (match expr
       [(struct varref (toplevel dummy))
        (make-VariableReference (parse-toplevel toplevel))]))

   (define (parse-assign expr)
     (match expr
       [(struct assign ((struct toplevel (depth pos const? ready?)) rhs undef-ok?))
        (make-ToplevelSet depth pos (parse-expr-seq-constant rhs))]))


   (define (parse-apply-values expr)
     (match expr
       [(struct apply-values (proc args-expr))
        (make-ApplyValues (parse-expr-seq-constant proc)
                          (parse-expr-seq-constant args-expr))]))


   (define (parse-primval expr)
     (match expr
       [(struct primval (id))
        (let ([name (hash-ref primitive-table id)])
          (make-PrimitiveKernelValue name))]))]



  [else
   (void)])