import time

class CPU:
    def __init__(self):
        self.running = False
        self.IP = 254
        self.acc = 0
        self.flags = { 'C': False, 'Z': False, 'N': False, 'Eq': False }
        self.instruction = { 'opcode': False, 'operand': False }
        self.memory = False


    def load_memory(self, bytes):
        self.memory = bytes + bytearray(256 - len(bytes))
        # print(self.memory)

    def start(self):
        self.running = True

    def step(self):
        if self.IP >= 255: # TODO CHECK
            self.IP = 0
        print("IP:", toHex(self.IP))
        self.instruction['opcode'] = self.memory[self.IP]
        self.IP = self.IP+1
        self.instruction['operand'] = self.memory[self.IP]
        self.IP = self.IP+1
        self.nums2mnems[self.instruction['opcode']](self, self.instruction['operand'])

        print("instr:", toHex(self.instruction['opcode']), toHex(self.instruction['operand']))
        print("mnem:", self.nums2mnems[self.instruction['opcode']])
        print("acc:", self.acc, "N:", self.flags['N'])
        print("running:", self.running)
        print()
        # self.print_screen()
        print("byte 26 (keyboard):", self.memory[26])
        print()

    def hlt(self, operand):
        self.running = False

    def nop(self, operand):
        pass

    def lda_lit(self, operand):
        self.acc = operand
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False
        
    def lda_mem(self, operand):
        self.acc = self.memory[operand]
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False

    def sta_lit(self, operand):
        self.memory[operand] = self.acc

    def sta_mem(self, operand):
        self.memory[self.memory[operand]] = self.acc

    def add_lit(self, operand):
        self.acc = self.acc + operand
        if self.acc > 255:
            self.acc = self.acc % 256
            self.flags['C'] = True
        else:
            self.flags['C'] = False
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False

    def add_mem(self, operand):
        self.acc = self.acc + self.memory[operand]
        if self.acc > 255:
            self.acc = self.acc % 256
            self.flags['C'] = True
        else:
            self.flags['C'] = False
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False

    def sub_lit(self, operand):
        self.acc = self.acc - operand
        if self.acc < 0:
            self.acc = self.acc % 256
            self.flags['C'] = True
        else:
            self.flags['C'] = False
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False

    def sub_mem(self, operand):
        self.acc = self.acc - self.memory[operand]
        if self.acc > 255:
            self.acc = self.acc % 256
            self.flags['C'] = True
        else:
            self.flags['C'] = False
        self.flags['Z'] = True if self.acc == 0 else False
        self.flags['Eq'] = True if self.acc == operand else False
        self.flags['N'] = True if self.acc > 127 else False

    def jmp_lit(self, operand):
        self.IP = operand

    def jmp_mem(self, operand):
        self.IP = self.memory[operand]

    def ske(self, operand): # FIXME
#        if self.flags['Eq']:
#            self.IP += 2
        if self.acc == operand:
            self.IP += 2

    def skz(self, operand):
        if self.flags['Z']:
            self.IP += 2

    def skn(self, operand):
        if self.flags['N']:
            self.IP += 2

    def skc(self, operand):
        if self.flags['C']:
            self.IP += 2

    def cst(self, operand):
        self.flags['C'] = True

    def ccl(self, operand):
        self.flags['C'] = False

    nums2mnems = {
        0: hlt,      # x0
        1: nop,      # x1
        2: lda_lit,  # 02
        3: sta_lit,  # 03
        4: add_lit,  # 04
        5: sub_lit,  # 05
        6: jmp_lit,  # 06
        7: ske,      # x7
        8: skz,      # x8
        9: skn,      # x9
        10: skc,     # A
        11: cst,     # B
        12: ccl,     # C
        16: hlt,     # 
        17: nop,     # 
        18: lda_mem, # 12
        19: sta_mem, # 13
        20: add_mem, # 14
        21: sub_mem, # 15
        22: jmp_mem, # 16
        23: ske,
        24: skz,
        25: skn,
        26: skc,
        27: cst,
        28: ccl,
    }