//   This file is part of uVM.
//
//   uVM is free software: you can redistribute it and/or modify
//   it under the terms of the GNU General Public License as published by
//   the Free Software Foundation, either version 3 of the License, or
//   (at your option) any later version.
//
//   uVM is distributed in the hope that it will be useful,
//   but WITHOUT ANY WARRANTY; without even the implied warranty of
//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//   GNU General Public License for more details.
//
//   You should have received a copy of the GNU General Public License
//   along with uVM.  If not, see <http://www.gnu.org/licenses/>.
//

#include <vector>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>

#include "../include/cpu.h"
#include "../include/logging.h"

CPU::CPU(unsigned int stack_size) {
  // If someone says stack_size 0 they are in for a surprise
  stack = (int*)malloc(stack_size * sizeof(int));
}

CPU::~CPU() {
  if(stack != NULL) {
    free(stack);
  }
}

// Load loads the code into CPU memory...and always returns true
bool CPU::load(std::vector<int> c) {
  code = c;
  return true;
}

// Run is the main loop of the entire CPU. It handles each opcode individually.
//
// At the end of each run the stack pointer and instruction pointer are reset to get the CPU
// ready to load the next program.
void CPU::run() {
  while(code[ip] != CPU::opcode::HALT && ip != code.size()) {
    switch(code[ip]) {
      case CPU::opcode::IPUSH: {
        LogMemWithArg(ip, CPU::opcode_map[code[ip]], code[ip + 1]);
        stack[++sp] = code[++ip];
        ip++;
        break;
      }
      case CPU::opcode::ISAVE0: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        t0 = stack[sp--];
        ip++;
        break;
      }
      case CPU::opcode::ISAVE1: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        t1 = stack[sp--];
        ip++;
        break;
      }
      case CPU::opcode::ISAVE2: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        t2 = stack[sp--];
        ip++;
        break;
      }
      case CPU::opcode::ILOAD0: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        stack[++sp] = t0;
        ip++;
        break;
      }
      case CPU::opcode::ILOAD1: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        stack[++sp] = t1;
        ip++;
        break;
      }
      case CPU::opcode::ILOAD2: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        stack[++sp] = t2;
        ip++;
        break;
      }
      case CPU::opcode::IADD: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        stack[sp] = a + b;
        ip++;
        break;
      }
      case CPU::opcode::IDIV: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        stack[sp] = a / b;
        ip++;
        break;
      }
      case CPU::opcode::IREM: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        stack[sp] = a % b;
        ip++;
        break;
      }
      case CPU::opcode::CMP: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        cf = a == b;
        ip++;
        break;
      }
      case CPU::opcode::JC: {
        LogMemWithArg(ip, CPU::opcode_map[code[ip]], code[ip + 1]);
        if(cf) {
          ip = code[ip + 1];
        } else {
          ip += 2;
        }
        break;
      }
      case CPU::opcode::ISUB: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        stack[sp] = a - b;
        ip++;
        break;
      }
      case CPU::opcode::IMUL: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        int a = stack[sp--];
        int b = stack[sp--];
        stack[sp] = a * b;
        ip++;
        break;
      }
      case CPU::opcode::JMP: {
        LogMemWithArg(ip, CPU::opcode_map[code[ip]], code[ip + 1]);
        ip = code[ip + 1];
        break;
      }
      case CPU::opcode::PRINT: {
        LogMem(ip, CPU::opcode_map[code[ip]]);
        printf("%d\n", stack[sp]);
        sp--;
        ip++;
        break;
      }
    }
  }

  sp = -1;
  ip = 0;
}