;;;
;;; An implementation of the Memory Array Redcode Simulator (MARS)
;;;

(import (chicken io)
        (chicken string)
        (chicken random)
        (chicken condition)
        matchable
        wish)

;;; Constants
;;

(define core-size 20)
(define max-steps 10000)


;;; Instructions
;;

(define (make-instr opcode modifier A-mode A-num B-mode B-num name)
  (list opcode modifier A-mod A-num B-mode B-num name))

(define (instr-opcode instr) (list-ref instr 0))
(define (instr-modifier instr) (list-ref instr 1))
(define (instr-A-mode instr) (list-ref instr 2))
(define (instr-A-num instr) (list-ref instr 3))
(define (instr-B-mode instr) (list-ref instr 4))
(define (instr-B-num instr) (list-ref instr 5))
(define (instr-name instr) (list-ref instr 6))

(define (mode->string mode)
  (case mode
    ((immediate) "#")
    ((direct) "$")
    ((indirect-A) "*")
    ((indirect-B) "@")
    ((pre-indirect-A) "{")
    ((pre-indirect-B) "<")
    ((post-indirect-A) "}")
    ((post-indirect-B) ">")
    (else
     (error "Unknown mode."))))

(define (instr->string opcode modifier A-mode A-num B-mode B-num name)
  (conc opcode
        "." modifier
        " " (mode->string A-mode) A-num
        " " (mode->string B-mode) B-num
        " ;" name))
        
(define initial-instruction
  (make-instr 'DAT 'F 'immediate 0 'immediate 0 '()))


;;; Memory setup and addressing
;;

(define (make-core core-size opcode modifier A-mode A-num B-mode B-num)
  (let ((opcodes (make-vector core-size opcode))
        (modifiers (make-vector core-size modifier))
        (A-modes (make-vector core-size A-mode))
        (A-nums (make-vector core-size A-num))
        (B-modes (make-vector core-size B-mode))
        (B-nums (make-vector core-size B-num))
        (names (make-vector core-size '())))
    (lambda args
      (match args
        ((i 'copy-to j n)
         (vector-set! opcodes j (vector-ref opcodes i))
         (vector-set! modifiers j (vector-ref modifiers i))
         (vector-set! A-modes j (vector-ref A-modes i))
         (vector-set! A-nums j (vector-ref A-nums i))
         (vector-set! B-modes j (vector-ref B-modes i))
         (vector-set! B-nums j (vector-ref B-nums i))
         (vector-set! names j n))
        ((i 'copy-from-instr! instr)
         (vector-set! opcodes i (instr-opcode instr))
         (vector-set! modifiers i (instr-modifier instr))
         (vector-set! A-mode i (instr-A-mode instr))
         (vector-set! A-num i (instr-A-num instr))
         (vector-set! B-mode i (instr-B-mode instr))
         (vector-set! B-num i (instr-B-num instr))
         (vector-set! names i (instr-name instr)))
        ((i 'opcode) (vector-ref opcodes i))
        ((i 'modifier) (vector-ref modifiers i))
        ((i 'A-mode) (vector-ref A-modes i))
        ((i 'A-num) (vector-ref A-nums i))
        ((i 'B-mode) (vector-ref B-modes i))
        ((i 'B-num) (vector-ref B-nums i))
        ((i 'name) (vector-ref names i))
        ((i 'set-opcode! x n) (vector-set! opcodes i x) (vector-set! names i n))
        ((i 'set-modifier! x n) (vector-set! modifiers i x) (vector-set! names i n))
        ((i 'set-A-mode! x n) (vector-set! A-modes i x) (vector-set! names i n))
        ((i 'set-A-num! x n) (vector-set! A-nums i x) (vector-set! names i n))
        ((i 'set-B-mode! x n) (vector-set! B-modes i x) (vector-set! names i n))
        ((i 'set-B-num! x n) (vector-set! B-nums i x) (vector-set! names i n))
        (('dump)
         (let loop ((i 0))
           (unless (>= i core-size))
           (print* i ":\t")
           (instr->string (vector-ref opcodes i)
                          (vector-ref modifiers i)
                          (vector-ref A-modes i)
                          (vector-ref A-nums i)
                          (vector-ref B-modes i)
                          (vector-ref B-nums i)
                          (vector-ref names i))))))))

(define (addr+ . args)
  (foldl (lambda (a b)
           (modulo (+ a b core-size) core-size))
         0 args))

;;; Programmes
;;

(define (make-prog name instrs offset)
  (list name instrs offset))

(define (prog-name prog) (list-ref prog 0))
(define (prog-instrs prog) (list-ref prog 1))
(define (prog-offset prog) (list-ref prog 2))

(define (install-prog core prog addr)
  (let loop ((ptr addr)
             (instrs (prog-instrs prog)))
    (unless (null? instrs)
      (core ptr 'copy-from-instr! (car instrs))
      (loop (addr+ ptr 1) (cdr instrs))))
  (make-player (prog-name prog)
               (addr+ addr (prog-offset prog))))

(define (can-install-prog? core prog-len addr)
  (let loop ((ptr addr)
             (remaining prog-len))
    (if (= remaining 0)
        #t
        (if (null? (core ptr 'name))
            (loop (addr+ ptr 1)
                  (- remaining 1))
            #f))))

(define (install-progs core progs)
  (let loop ((players '())
             (progs-left progs))
    (if (null? progs-left)
        players
        (let ((addr (pseudo-random-integer core-size))
              (prog (car progs-left)))
          (if (can-install-prog? core (length (prog-instrs prog)) addr)
              (loop (cons (install-prog core prog addr) players)
                    (cdr progs-left))
              (loop players progs-left))))))

(define (make-player name ptr)
  (list name ptr))

(define (player-name player) (car player))
(define (player-ptrs player) (cdr player))

(define (player-set-ptrs! player ptrs)
  (set-cdr! player ptrs))


;;; Executive function
;;

(define (run players steps-left)
  (cond
   ((<= steps-left 0) players)      ;Tie between remaining players
   ;; ((<= (length players) 1) players) ;There's only one player left who thus wins
   (else
    (let* ((player (car players))
           (other-players (cdr players))
           (ptrs (player-ptrs player))
           (new-ptrs (execute-instr (car ptrs) (player-name player))))
      (if (null? new-ptrs)
          (run other-players (- steps-left 1))
          (begin
            (player-set-ptrs! player (append (cdr ptrs) new-ptrs))
            (run (append other-players (list player)) (- steps-left 1))))))))

(define (execute-instr ptr name)
  (let* ((instr (core-get ptr))
         (A-ptr (eval-operand (instr 'A-mode) (instr 'A-num) ptr))
         (B-ptr (eval-operand (instr 'B-mode) (instr 'B-num) ptr))
         (modifier (instr 'modifier)))
    (case (instr 'opcode)
      ((DAT)
       '()) ;Game over, man, game over!
      ((MOV)
       (if (eq? modifier 'I)
           ((core-get B-ptr) 'copy-from! (core-get A-ptr) name)
           (combine A-ptr B-ptr modifier name (lambda (x y) y)))
       (list (addr+ ptr 1)))
      ((ADD)
       (combine-and-store A-ptr B-ptr modifier name addr+)
       (list (addr+ ptr 1)))
      ((SUB)
       (combine-and-store A-ptr B-ptr modifier name
                          (lambda (x y) (addr+ x (- y))))
       (list (addr+ ptr 1)))
      ((MUL)
       (combine-and-store A-ptr B-ptr modifier name
                          (lambda (x y) (modulo (* (addr+ x core-size)
                                                   (addr+ y core-size))
                                                core-size)))
       (list (addr+ ptr 1)))
      ((DIV)
       (condition-case 
           (begin
             (combine-and-store A-ptr B-ptr modifier name
                                (lambda (x y) (quotient (addr x core-size)
                                                        (addr y core-size))))
             (list (addr+ ptr 1)))
         ((exn arithmetic) '())))
      ((MOD)
       (condition-case
           (begin
             (combine-and-store A-ptr B-ptr modifier name
                                (lambda (x y) (remainder (addr x core-size)
                                                         (addr y core-size))))
             (list (addr+ ptr 1)))
         ((exn arithmetic) '())))
      ((JMP)
       (list (addr+ ptr ((core-get A-ptr) 'A-num))))
      ((JMZ)
       (list (addr+ ptr (if (instr-zero? B-ptr modifier #f)
                            ((core-get A-ptr) 'A-num)
                            1))))
      ((JMN)
       (list (addr+ ptr (if (not (instr-zero? B-ptr modifier #f))
                            ((core-get A-ptr) 'A-num)
                            1))))
      ((DJN)
       (list (addr+ ptr (if (not (instr-zero? B-ptr modifier #t))
                            ((core-get A-ptr) 'A-num)
                            1))))
      ((SEQ CMP)
       (list (addr+ ptr (if (compare-instrs A-ptr B-ptr modifier =) 2 1))))
      ((SNE)
       (list (addr+ ptr (if (compare-instrs A-ptr B-ptr modifier =) 1 2))))
      ((SLT)
       (list (addr+ ptr (if (compare-instrs A-ptr B-ptr modifier <) 2 1))))
      ((SPL)
       (list (addr+ ptr 1) (addr+ ptr ((core-get A-ptr) 'A-num))))
      ((NOP)
       (list (addr+ ptr 1)))
      (else
       (error "Unrecognised opcode" (instr 'opcode))))))

(define (compare-instrs A-ptr B-ptr modifier test)
  (let ((A-instr (core-get A-ptr))
        (B-instr (core-get B-ptr)))
    (case modifier
      ((A) (test (A-instr 'A-num) (B-instr 'A-num)))
      ((B) (test (A-instr 'B-num) (B-instr 'B-num)))
      ((AB) (test (A-instr 'A-num) (B-instr 'B-num)))
      ((BA) (test (A-instr 'B-num) (B-instr 'A-num)))
      ((F) (and
            (test (A-instr 'A-num) (B-instr 'A-num))
            (test (A-instr 'B-num) (B-instr 'B-num))))
      ((X) (and
            (test (A-instr 'A-num) (B-instr 'B-num))
            (test (A-instr 'B-num) (B-instr 'A-num))))
      ((I) (and
            (if (eq? test =)
                (and
                 (eq? (A-instr 'opcode) (B-instr 'opcode))
                 (eq? (A-instr 'modifier) (B-instr 'modifier))
                 (eq? (A-instr 'A-mode) (B-instr 'B-mode))
                 (eq? (A-instr 'B-mode) (B-instr 'A-mode)))
                #t)
            (test (A-instr 'A-num) (B-instr 'B-num))
            (test (A-instr 'B-num) (B-instr 'A-num)))))))

(define (instr-zero? ptr modifier decrement)
  (let ((instr (core-get ptr)))
    (case modifier
      ((A AB)
       (if decrement (instr 'set-A-num! (addr+ (instr 'A-num) -1)))
       (= 0 (instr 'A-num)))
      ((A AB)
       (if decrement (instr 'set-B-num! (addr+ (instr 'B-num) -1)))
       (= 0 (instr 'B-num)))
      ((X I F)
       (if decrement
           (begin
             (instr 'set-A-num! (addr+ (instr 'A-num) -1))
             (instr 'set-B-num! (addr+ (instr 'B-num) -1))))
       (and (= 0 (instr 'A-num))
            (= 0 (instr 'B-num)))))))

(define (combine-and-store A-ptr B-ptr modifier name f)
  (case modifier
    ((A) ((core-get B-ptr) 'set-A-num!
          (f ((core-get B-ptr) 'A-num) ((core-get A-ptr) 'A-num)) name))
    ((B) ((core-get B-ptr) 'set-B-num!
          (f ((core-get B-ptr) 'B-num) ((core-get A-ptr) 'B-num)) name))
    ((AB) ((core-get B-ptr) 'set-B-num!
           (f ((core-get B-ptr) 'B-num) ((core-get A-ptr) 'A-num)) name))
    ((BA) ((core-get B-ptr) 'set-A-num!
           (f ((core-get B-ptr) 'A-num) ((core-get A-ptr) 'B-num)) name))
    ((F I) ((core-get B-ptr) 'set-A-num!
            (f ((core-get B-ptr) 'A-num) ((core-get A-ptr) 'A-num))) name
           ((core-get B-ptr) 'set-B-num!
            (f ((core-get B-ptr) 'B-num) ((core-get A-ptr) 'B-num)) name))
    ((X) ((core-get B-ptr) 'set-A-num!
          (f ((core-get B-ptr) 'A-num) ((core-get A-ptr) 'B-num)) name)
     ((core-get B-ptr) 'set-B-num!
      (f ((core-get B-ptr) 'B-num) ((core-get A-ptr) 'A-num)) name))))

(define (eval-operand mode num ptr)
  (addr+ ptr
         (case mode
           ((immediate) 0)
           ((direct) num)
           ((indirect-A) (addr+ num ((core-get (addr+ ptr num)) 'A-num)))
           ((indirect-B) (addr+ num ((core-get (addr+ ptr num)) 'B-num)))
           ((pre-indirect-A)
            (let ((aux-instr (core-get (addr+ ptr num))))
              ((aux-instr set-A-num! (addr+ -1 (aux-instr 'A-num))))
              (addr+ num (aux-instr 'A-num))))
           ((pre-indirect-B)
            (let ((aux-instr (core-get (addr+ ptr num))))
              (aux-instr set-B-num!(addr+ -1 (aux-instr 'B-num)))
              (addr+ num (aux-instr 'B-num))))
           ((post-indirect-A)
            (let* ((aux-instr (core-get (addr+ ptr num)))
                   (old-A-num (aux-instr 'A-num)))
              (aux-instr set-A-num! (addr+ 1 (aux-instr 'A-num)))
              (addr+ num old-A-num)))
           ((post-indirect-B)
            (let* ((aux-instr (core-get (addr+ ptr num)))
                   (old-B-num (aux-instr 'B-num)))
              (aux-instr set-B-num! (addr+ 1 (aux-instr 'B-num)))
              (addr+ num old-B-num)))
           (else
            (error "Unrecognized mode" mode)))))

;;; TEST CODE

(define addressing-test
  (make-prog 'at (list
                   (make-instr 'DAT 'F 'immediate 42 'immediate 53 'at)
                   (make-instr 'DAT 'F 'immediate 123 'immediate 256 'at)
                   (make-instr 'MOV 'A 'indirect-B 4 'direct 7 'at)
                   (make-instr 'NOP 'I 'immediate 0 'immediate 0 'at)
                   (make-instr 'NOP 'I 'immediate 0 'immediate 0 'at)
                   (make-instr 'NOP 'I 'immediate 0 'immediate 0 'at)
                   (make-instr 'DAT 'F 'immediate -5 'immediate -6 'at)) 2))

(define imp
  (make-prog 'imp (list (make-instr 'MOV 'I 'direct 0 'direct 1 'imp)) 0))

(define dwarf
  (make-prog 'dwarf (list
                     (make-instr 'DAT 'F 'immediate 0 'immediate -1 'dwarf)
                     (make-instr 'ADD 'AB 'immediate 5 'direct -1 'dwarf)
                     (make-instr 'MOV 'I 'direct -2 'indirect-B -2 'dwarf)
                     (make-instr 'JMP 'I 'immediate -2 'immediate 0 'dwarf)) 1))

(initialize-core)
(define players (install-progs (list dwarf imp)))

(dump-core)