;;-*-Lisp-*-
(in-package goal)

;; name: gcommon.gc
;; name in dgo: gcommon
;; dgos: KERNEL

;; gcommon is the first file compiled and loaded.
;; it's expected that this function will mostly be hand-decompiled



(defun identity ((x object))
  "Function which returns its input. The first function of the game!"
  x
  )


(defun 1/ ((x float))
  "Reciprocal floating point"
  ;; likely inlined? nothing calls this.
  (declare (inline))
  (/ 1. x)
  )

;; these next 4 functions are just function wrappers around the build in add/subtract/multiply/divide.
;; this will let you use + as an operation on integers and also as a function pointer.
(defun + ((x int) (y int))
  "Compute the sum of two integers"
  (+ x y)
  )

(defun - ((x int) (y int))
  "Compute the difference of two integers"
  (- x y)
  )

(defun * ((x int) (y int))
  "Compute the product of two integers"
  ;; TODO - verify that this matches the PS2 exactly.
  ;; Uses mult (three operand form) in MIPS
  (* x y)
  )

(defun / ((x int) (y int))
  "Compute the quotient of two integers"
  ;; TODO - verify this matches the PS2 exactly
  (/ x y)
  )

(defun ash ((value int) (shift-amount int))
  "Arithmetic shift value by shift-amount.  
  A positive shift-amount will shift to the left and a negative will shift to the right.
  "
  
  ;; currently the compiler does not support "ash", so this function is also used to implement "ash".
  ;; in the future, the compiler should be able to use constant propagation to turn constant shifts
  ;; into x86 constant shifts when possible (which are faster). The GOAL compiler seems to do this.
  
  ;; The original implementation was inline assembly, to take advantage of branch delay slots:
  ;;  (or v1 a0 r0)      ;; likely inserted by register coloring, not entirely needed
  ;;  (bgezl a1 end)     ;; branch to function end if positive shift (left)...
  ;;  (dsllv v0 v1 a1)   ;; do left shift in delay slot
  ;;  
  ;;  (dsubu a0 r0 a1)   ;; negative shift amount for right shift
  ;;  (dsrav v0 v1 a0)   ;; do right shift
  ;;  (label end)
  
  (declare (inline))
  (if (> shift-amount 0)
      ;; these correspond to x86-64 variable shift instructions.
      ;; the exact behavior of GOAL shifts (signed/unsigned) are unknown so for now shifts must
      ;; be manually specified.
      (shlv value shift-amount)
      (sarv value (- shift-amount))
      )
  )

(defun mod ((a int) (b int))
  "Compute mod.  It does what you expect for positive numbers.  For negative numbers, nobody knows what to expect.
  This is a 32-bit operation.  It uses an idiv on x86 and gets the remainder."
  
  ;; The original implementation is div, mfhi
  ;; todo - verify this is exactly the same as the PS2.
  (mod a b)
  )


(defun rem ((a int) (b int))
  "Compute remainder (32-bit).  It is identical to mod. It uses a idiv and gets the remainder"
  
  ;; The original implementation is div, mfhi
  ;; todo - verify this is exactly the same as the PS2.
  (mod a b)
  )

(defun abs ((a int))
  "Take the absolute value of an integer"
  
  ;; short function, good candidate for inlining
  (declare (inline))
  
  ;; The original implementation was inline assembly, to take advantage of branch delay slots:
  ;;  (or v0 a0 r0)     ;; move input to output unchanged, for positive case
  ;;  (bltzl v0 end)    ;; if negative, execute the branch delay slot below...
  ;;  (dsubu v0 r0 v0)  ;; negate
  ;;  (label end)
  
  
  (if (> a 0) ;; condition is "a > 0"
      a       ;; true case, return a
      (- a)   ;; false case, return -a. (- a) is like (- 0 a)
      )
  )

(defun min ((a int) (b int))
  "Compute minimum."
  
  ;; The original implementation was inline assembly, to take advantage of branch delay slots:
  ;;  (or v0 a0 r0)    ;; move first arg to output (case of second arg being min)
  ;;  (or v1 a1 r0)    ;; move second arg to v1 (likely strange coloring)
  ;;  (slt a0 v0 v1)   ;; compare args
  ;;  (movz v0 v1 a0)  ;; conditional move the second arg to v0 if it's the minimum
  
  (declare (inline))
  (if (> a b) b a)
  )

(defun max ((a int) (b int))
  "Compute maximum."
  (declare (inline))
  (if (> a b) a b)
  )

(defun logior ((a int) (b int))
  "Compute the bitwise inclusive-or"
  (logior a b)
  )

(defun logand ((a int) (b int))
  "Compute the bitwise and"
  (logand a b)
  )

(defun lognor ((a int) (b int))
  "Compute not or."
  ;; Note - MIPS has a 'nor' instruction, but x86 doesn't.
  ;; the GOAL x86 compiler therefore doesn't have a nor operation,
  ;; so lognor is implemented by this inline function instead.
  (declare (inline))
  (lognot (logior a b))
  )

(defun logxor ((a int) (b int))
  "Compute the logical exclusive-or"
  (logxor a b)
  )

(defun lognot ((a int))
  "Compute the bitwise not"
  (lognot a)
  )

(defun false-func ()
  "Return false"
  ;; In GOAL, #f is false.  It's a symbol. Each symbol exists as an object, and each symbol has a value
  ;; The value of the false symbol #f is the false symbol #f.
  
  ;; To get the symbol, instead of its value, we use quote.  Writing 'x is equivalent to (quote x)
  '#f
  )

(defun true-func ()
  "Return true"
  ;; GOAL consideres anything that's not #f to be true. But there's also an explicit true symbol.
  '#t
  )

;; The C Kernel implements the format function and creates a trampoline function in the GOAL heap which jumps to
;; format.  (In OpenGOAL, there's actually two trampoline functions, to make the 8 arguments all work.)
;; For some reason, the C Kernel names this trampoline function _format. We need to set the value of format
;; _format in order for format to work.

;; I suspect this was to let us define (yet another) function here which set up C-style var args (supported from C Kernel)
;; or 128-bit arguments (unimplemented in C Kernel), but both of these were never finished.
(define format _format)

;; vec4s - this is present in the game as a 128-bit integer child type full of 4 floats.
;; this doesn't seem to be used, and OpenGOAL doesn't support bitfields or 128-bit integers yet, so it is omitted.
;; I suspect this was unused because putting 4 floats in a 128-bit integer register is not an incredibly useful thing to do
;; - accessing all of these floats will be very slow.


(deftype bfloat (basic)
  ((data float :offset-assert 4))
  (:methods 
    (print (_type_) _type_ 2)    ;; we will override print later on. This is optional to include
    (inspect (_type_) _type_ 3)  ;; this is a parent method we won't override. This is also optional to inlcude
    )

  :size-assert 8
  :method-count-assert 9
  :flag-assert #x900000008
  )

(defmethod print bfloat ((obj bfloat))
  "Override the default print method to print a bfloat like a normal float"
  (format #t "~f" (-> obj data))
  obj
  )

;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Type System
;;;;;;;;;;;;;;;;;;;;;;;;;;

; The asize-of method should return the total size in memory used by an object.
; It's used for traversing heaps of basics and copying basics.
; Most basic/structure types are "fixed size", and their default asize-of method will simply
; return the "size" field of their type, so you don't have to worry about it.
; However, some types are dynamic (like a string) and require that you provide your own method.
; A common approach is to have an "allocated-length" field, then have the asize-of method return
;  (+ (-> obj type size) (* elem-size (-> obj allocated-length)))
; asize-of returns the actual size, including the type field, and can have any alignment.

;; A "type" object contains some basic information about a type as well as the list of methods.
;; Some types have more methods than others, so the method table makes "type" a dynamic type.
;; As a result, we should define an "asize-of" method for type. It's possibly unused and it's wrong.

(defmethod asize-of type ((obj type))
  "Get the size in memory of a type"
  ;; The 28 is 8 bytes too large. It's also strange that types have a 16-byte aligned size always, 
  ;; but this matches what the runtime does as well. There's no reason that I can see for this,
  ;; as other basics don't require 16-byte aligned sizes.
  ;; - this is perhaps accurate back when types where inside of the symbol table? Or before switching to u16's
  ;; for some of the type values?
  (align16 (+ 28 (* 4 (-> type allocated-length))))
  )

(defun basic-type? ((obj basic) (input-type type))
  "Is obj an object of type input-type, or of child type of input-type?
  Note: checking if a basic is of type object will return #f."
  (let ((basics-type (-> obj type))
        (object-type object))
    (until (eq? (set! basics-type (-> basics-type parent)) object-type)
           (if (eq? basics-type input-type)
               ;; return-from #f will return from the function with the value of #t
               (return-from #f #t)
               )
           )
    )
  #f ;; didn't find it, return false
  )

(defun type-type? ((a type) (b type))
  "is a a type (or child type) of type b?"
  (let ((object-type object))
    (until (or (eq? (set! a (-> a parent)) object-type)
               (zero? a)
               )
           (if (eq? a b)
               (return-from #f #t)
               )
           )
    )
  #f
  )

(defun find-parent-method ((the-type type) (method-id int))
  "Find the nearest parent which has a different method, and get that method.
  Use with extreme caution - if a checked parent has fewer methods than the child, it will
  access out-of-bounds memory. Returns the nothing function if it gets to the top and
  the parent has the same type, or if any parent has 0 as a method."
  (let* ((child-method (-> the-type method-table method-id))
         (parent-method child-method)
         )
    
    ;; keep looking until we find a different parent method
    (until (not (eq? parent-method child-method))
           ;; at the top of the type tree.
           (if (eq? the-type object)
               (return-from #f nothing)
               )
           
           (set! the-type (-> the-type parent))
           (set! parent-method (-> the-type method-table method-id))
           (if (eq? 0 (the int parent-method))
               (return-from #f nothing)
               )
           )
    parent-method
    )
  )

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; pair and list
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defun ref ((obj object) (idx int))
  "Get the nth item from a list.  No type checking or range checking is done, so be careful!"
  (dotimes (i idx (car obj))
    (set! obj (cdr obj))
    )
  )

(defmethod length pair ((obj pair))
  "Get the number of elements in a proper list"
  (if (eq? obj '())
      (return-from #f 0)
      )
  
  (let ((lst (cdr obj))
        (len 1))
    (while (and (not (eq? lst '()))
                (pair? lst)
                )
      (+1! len)
      (set! lst (cdr lst))
      )
    len)
  )

(defmethod asize-of pair ((obj pair))
  "Get the asize of a pair"
  (the-as int (-> pair size))
  )

(defun last ((obj object))
  "Get the last pair in a list."
  (while (not (eq? (cdr obj) '()))
    (set! obj (cdr obj))
    )
  obj
  )

(defun member ((obj object) (lst object))
  "if obj is a member of the list, return the pair containing obj as its car.
  if not, return #f."
  (while (and (not (eq? lst '()))
              (not (eq? (car lst) obj)))
    (set! lst (cdr lst))
    )
  
  (if (eq? lst '())
      #f
      lst
      )
  )

(define-extern name= (function basic basic symbol))

(defun nmember ((obj basic) (lst object))
  "If obj is a member of the list, return the pair containing obj as its car.
  If not, return #f.  Use name= (see gstring.gc) to check equality."
  (while (and (not (eq? lst '()))
              (not (name= (the basic (car lst)) obj))
              )
    (set! lst (cdr lst))
    )
  
  (if (eq? lst '())
      #f
      lst
      )
  )

(defun assoc ((item object) (alst object))
  "Get a pair with car of item from the association list (list of pairs) alst."
  (while (and (not (null? alst))
              (not (eq? (caar alst) item)))
    (set! alst (cdr alst))
    )
  (if (not (null? alst))
      (car alst)
      #f
      )
  )

(defun assoce ((item object) (alst object))
  "Like assoc, but a pair with car of 'else will match anything"
  (while (and (not (null? alst))
              (not (eq? (caar alst) item))
              (not (eq? (caar alst) 'else))
              )
    (set! alst (cdr alst))
    )
  (if (not (null? alst))
      (car alst)
      #f
      )
  )

;; todo
;; nassoc
;; nassce

(defun append! ((front object) (back object))
  "Append back to front."
  (if (null? front)
      (return-from #f back)
      )
  
  (let ((lst front))
    ;; seek to the end of front
    (while (not (null? (cdr lst)))
      (set! lst (cdr lst))
      )
    
    ;; this check seems not needed
    (if (not (null? lst))
        (set! (cdr lst) back)
        )
    
    front
    )
  )

(defun delete! ((item object) (lst object))
  "Delete the first occurance of item from a list and return the list.
  Does nothing if the item isn't in the list."
  (if (eq? (car lst) item)
      (return-from #f (the pair (cdr lst)))
      )
  
  (let ((iter (cdr lst))
        (rep lst))
    
    (while (and (not (null? iter))
                (not (eq? (car iter) item)))
      (set! rep iter)
      (set! iter (cdr iter))
      )
    
    (if (not (null? iter))
        (set! (cdr rep) (cdr iter))
        )
    )
  (the pair lst)
  )

(defun delete-car! ((item object) (lst object))
  "Like delete, but will delete if (car item-from-list) is equal to item.  Useful for deleting from association list by key."
  ;(format #t "call to delete car: ~A ~A~%" item lst)
  (if (eq? (caar lst) item)
      (return-from #f (cdr lst))
      )
  
  (let ((rep lst)
        (iter (cdr lst)))
    (while (and (not (null? iter))
                (not (eq? (caar iter) item)))
      (set! rep iter)
      (set! iter (cdr iter))
      )
    
    (if (not (null? iter))
        (set! (cdr rep) (cdr iter))
        )
    )
  lst
  )

(defun insert-cons! ((kv object) (alst object))
  "Insert key-value pair into an association list.  Also removes the old one if it was there."
  (cons kv (delete-car! (car kv) alst))
  )

(defun sort ((lst object) (compare (function object object object)))
  "Sort the given list in place.  Uses the given comparison function. The comparison function can 
  either return #t/#f or an integer, in which case the sign of the integer determines lt/gt."
  ;; in each iteration, we count how many changes we make. Once we make no changes, the list is sorted.
  (let ((changes -1)) 
    
    (while (not (zero? changes)) ;; outer loop
      (set! changes 0)      ;; reset changes for this iteration
      (let ((iter lst))     ;; iterate through list
        (while (and (not (null? (cdr iter)))
                    (pair? (cdr iter)))
          ;; L221
          (let* ((val1 (car iter))        ;; value at iterator
                 (val2 (car (cdr iter)))  ;; value after iterator
                 (c-result (compare val1 val2))) ;; run comparison function
            ;; check if val1 and val2 are in order. The compare function may either return #t
            ;; or it may return val1 - val2.  There is an issue if val1 - val2 happens to equal #t or #f.
            (unless (or
                      (and c-result (<= (the integer c-result) 0)) ;; not #f, and negative, we're sorted!
                      (eq? c-result #t) ;; explictly return #t, we're sorted!
                      )
              ;; these two aren't sorted! so we swap them and increment changes.
              (+1! changes)
              (set! (car iter) val2)
              (set! (car (cdr iter)) val1)
              )
            ;; move on to the next thing in the list.
            (set! iter (cdr iter))
            )
          )
        )
      )
    )
  lst
  )

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; inline array
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; a parent class for boxed "inline arrays" classes, 
;; An inline-array is an array with a bunch of objects back-to-back, as opposed to a bunch of
;; references back to back.
;; Most inline-arrays are unboxed and are just data - this is a somewhat rarely used container parent
;; class for a class that wraps an unboxed inline-array.
;; the "heap-base" field of the type is used to store the indexing scale.

(deftype inline-array-class (basic)
  ((length int32 :offset-assert 4)
   (allocated-length int32 :offset-assert 8)
   (data uint8 :dynamic)
   (_pad uint8 4)
   )
  (:methods (new (symbol type int) _type_ 0)    ;; we will override print later on. This is optional to include
            )
  )

(defmethod new inline-array-class ((allocation symbol) (type-to-make type) (cnt int))
  "Create a new inline-array.  Sets the length, allocated-length to cnt.  Uses the mysterious heap-base field
  of the type-to-make to determine the element size"
  (let* ((sz (+ (-> type-to-make size) (* (-> type-to-make heap-base) cnt)))
         (new-object (object-new (the int sz))))
    ;;(format 0 "create sz ~d at #x~X~%" sz new-object)
    (unless (zero? new-object)
      (set! (-> new-object length) cnt)
      (set! (-> new-object allocated-length) cnt)
      )
    new-object
    )
  )

(defmethod length inline-array-class ((obj inline-array-class))
  ;"Get the length of an inline-array"
  (-> obj length)
  )

(defmethod asize-of inline-array-class ((obj inline-array-class))
  ;"Get the size in memory of an inline-array-class"
  (+ (the-as int (-> obj type size))
     (* (-> obj allocated-length) (-> obj type heap-base))
     )
  )


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; array
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; boxed "pointer like" array.
;; unlike inline-array-class, all arrays are type array, but the content-type field stores the element type.
;; the stride of an array is 4, unless the element is a number, in which case the stride is the "size"

(defmethod new array ((allocation symbol) (type-to-make type) (content-type type) (size int))
  "Create a new array. The length and allocated-length are both set to size."
  (let ((obj (object-new (* size (if (type-type? content-type number)
                                     (-> content-type size)
                                     4
                                     )))))
    (set! (-> obj length) size)
    (set! (-> obj allocated-length) size)
    (set! (-> obj content-type) content-type)
    obj
    )
  )

;; todo array print and array inspect

(defmethod length array ((obj array))
  "Get the length field of an array."
  (-> obj length)
  )

(defmethod asize-of array ((obj array))
  "Get the size in memory of an array."
  (the int (+ (-> array size) (* (-> obj allocated-length) 
                                 (if (type-type? (-> obj content-type) number)
                                     (-> obj content-type size)
                                     4))))
  )



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; memcpy and similar
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defun mem-copy! ((dst pointer) (src pointer) (size int))
  "Copy memory from src to dst.  Size is in bytes.  This is not an efficient implementation,
  however, there are _no restrictions_ on size, alignment etc. Increasing address copy."
  (let ((i 0)
        (d (the pointer dst))
        (s (the pointer src))
        )
    
    (while (< i size)
      (set! (-> (the (pointer uint8) d) 0) (-> (the (pointer uint8) s) 0))
      (&+! d 1)
      (&+! s 1)
      (+1! i)
      )
    )
  dst
  )

(defun mem-set32! ((dst pointer) (value int) (n int))
  "Memset a 32-bit value n times.  Total memory filled is 4 * n bytes."
  (let ((p (the pointer dst))
        (i 0))
    (while (< i n)
      (set! (-> (the (pointer int32) p) 0) value)
      (&+! p 4)
      (+1! i)
      )
    )
  dst
  )


(defun print-tree-bitmask ((bitmask int) (len int))
  "The purpose of this function is unknown"
  (dotimes (i len #f)
    (if (zero? (logand bitmask 1))
      (format #t "    ")
      (format #t "|   ")
      )
    (set! bitmask (ash bitmask -1))
    )
  )