(in-package "CL-USER")


(defstruct (y-emu (:conc-name y-))

  addr
  data
  readmem
  writemem
  type
  rst

  ir
  pc

  d

  csp
  dsp

  datamem

  tos
  
  litbase
  
  addro

  regA
  regB
  regC
  regD

  dataeno

  datbus

  dat_source
  dat_dest

  addr_source

  cdsp_source
  cdsp_dest

  cdspbus

  pcb_source

  mic_inst
  
  micr_pc

  aluOp
  aluOut
)

(defparameter cpu0 (make-y-emu))

(setf (y-pc cpu0) 128)

(defun high? (sig)
  (= sig 1))

(defun low? (sig)
  (= sig 0))


(defparameter *micro_store* (make-array 2048 :initial-element 0))
(defparameter *branch_store* (make-array 128 :initial-element 0))

(defun extract-field (n a b)
  (let ((mask (- (expt 2 (+ (- a b) 1)) 1)))
    (setf mask (ash mask b))
    (ash (logand mask n) (- b))))


(defun decode-micro-inst (mic-inst)
  (values
   (extract-field mic-inst 31 27) 

   (extract-field mic-inst 26 22)
   (extract-field mic-inst 21 17)

   (extract-field mic-inst 16 14)
   (extract-field mic-inst 13 11)

   (extract-field mic-inst 10 9)

   (extract-field mic-inst 7 7)
   (extract-field mic-inst 8 8)

   (extract-field mic-inst 6 0)

   (extract-field mic-inst 35 32)))


(defun next-micr-pc (mic-pc mic-br)
  (if (= 0 mic-br)
      (+ mic-pc 1)
    (aref *branch_store* mic-br)))

(defun alu-proc (opA opB opC aluOp)
  opA)

(defun step-regs-cpu-1 (cpu)
  (let ((d (y-d cpu)))
    (case (y-dat_dest cpu)
      (0 (setf (y-ir cpu) (y-datbus cpu)))
      (1 (setf (y-tos cpu) (y-datbus cpu)))
      (2 (setf (y-litbase cpu) (y-datbus cpu)))
      (3 (setf (y-regA cpu) (y-datbus cpu)))
      (t (err (y-dat_dest cpu))))

    (case (y-cdsp_dest cpu)
      (0 (setf (y-csp cpu) (y-cdspbus cpu)))
      (1 (setf (y-dsp cpu) (y-cdspbus cpu)))
      (2 (setf (y-csp cpu) (y-datbus cpu)))
      (3 (setf (y-dsp cpu) (y-datbus cpu)))
      (t (err (y-cdsp_dest cpu))))

    (case (y-pcb_source cpu)
      (0 (setf (y-pc cpu) (+ (y-pc cpu) 4)))
      (1 (setf (y-pc cpu) (+ (y-pc cpu) d)))
      (2 (setf (y-pc cpu) (y-datbus cpu)))
      (t (err (y-pcb_source cpu))))))

(defun set-cpu-sources-1 (cpu)

  (set-addro cpu)
  (set-datbus cpu)
  (set-cdspbus cpu))


(defun set-addro (cpu)
  (let ((d (y-d cpu)))
    (setf
     (y-addro cpu)
     (case (y-addr_source cpu)
       (0 (y-dsp cpu))
       (1 (+ (y-dsp cpu) 4))
       (2 (- (y-dsp cpu) 4))
       (3 (+ (y-dsp cpu) d))
       
       (4 (y-csp cpu))
       (5 (+ (y-csp cpu) 4))
       (6 (- (y-csp cpu) 4))
       (7 (+ (y-csp cpu) d))

       (8 (y-pc cpu))
       
       (9 (y-aluOut cpu))
       
       (10 (+ (y-litbase cpu) d))

       (t 'z)))))

(defun set-datbus (cpu)
  )

(defun set-cdspbus (cpu)
  )


(defun err (n)
  (format t "error ~A in ~A ~%" n 0))

(defun extract-d (ir)
  (let ((mask (- (expt 2 16) - 1)))
    (ash (logand ir mask) 2)))

(defun step-y-emu (cpu addr data rst)
  (let ((addr_source nil)
        (dat_source nil)
        (dat_dest nil)
        (cdsp_source nil)
        (cdsp_dest nil)
        (pcb_source nil)
        (dataeno nil)
        (readmem nil)
        (micr_pc nil)
        (aluOp nil))

    (when (high? rst)
      (setf (y-pc cpu) 0)
      (setf (y-micr_pc cpu) 0)
      (return-from step-y-emu))

    (setf (y-d) (extract-d (y-ir cpu)))

    (setf (y-aluOut cpu) (alu-proc (y-tos cpu) (y-datbus cpu) (y-regA cpu) (y-aluOp cpu)))

    (step-regs-cpu-1 cpu)
  
    (setf (y-mic_inst cpu) (aref *micro_store* (y-micr_pc cpu)))

    (multiple-value-setq (addr_source dat_source dat_dest cdsp_source cdsp_dest pcb_source dataeno readmem micr_br aluOp)
        (decode-micro-inst (y-mic_inst cpu)))
    
    (setf (y-addr_source cpu) addr_source)

    (setf (y-dat_source cpu) dat_source)
    (setf (y-dat_dest cpu) dat_dest)

    (setf (y-cdsp_source cpu) cdsp_source)
    (setf (y-cdsp_dest cpu) cdsp_dest)

    (setf (y-pcb_source cpu) pcb_source)

    (setf (y-dataeno cpu) dataeno)
    (setf (y-readmem cpu) readmem)
    (setf (y-micr_pc cpu) (next-micr-pc (y-micr_pc cpu) micr_br))

    (setf (y-aluOp cpu) aluOp)

    (if (low? (y-dataeno cpu))
        (setf (y-datamem cpu) data)
      (setf (y-datamem cpu) 'z))

    (set-cpu-sources-1 cpu)

    (set addr (y-addro cpu))

    (if (high? (y-dataeno cpu))
      (setf (y-data cpu) (y-datbus cpu)))))