#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/mman.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

#define MEMORY_SIZE 65536  // 64KB memory (adjustable)
uint32_t memory[MEMORY_SIZE];  // Memory array

typedef enum {
    OP_ADD,    // dest = src1 + src2
    OP_MOV,    // dest = src1
    OP_JMP,    // jump to address
    OP_HALT    // terminate execution
} Opcode;

void run_vm() {
    uint32_t pc = 0;  // Program counter
    while (1) {
        // Fetch instruction
        Opcode opcode = memory[pc];
        uint32_t src1_addr = memory[pc + 1];
        uint32_t src2_addr = memory[pc + 2];
        uint32_t dest_addr = memory[pc + 3];
        pc += 4;  // Advance to next instruction

        // Validate addresses (safety check)
        if (src1_addr >= MEMORY_SIZE || src2_addr >= MEMORY_SIZE || dest_addr >= MEMORY_SIZE) {
            printf("Invalid memory address!\n");
            exit(1);
        }

        // Execute instruction
        switch (opcode) {
            case OP_ADD:
                memory[dest_addr] = memory[src1_addr] + memory[src2_addr];
                break;
            case OP_MOV:
                memory[dest_addr] = memory[src1_addr];
                break;
            case OP_JMP:
                pc = src1_addr;  // Jump to address
                break;
            case OP_HALT:
                return;
            default:
                printf("Unknown opcode: %d\n", opcode);
                exit(1);
        }
    }
}

int main() {
    // Initialize memory
    memory[0] = OP_ADD;     // Opcode
    memory[1] = 100;          // A (src1)
    memory[2] = 101;          // B (src2)
    memory[3] = 102;          // C (dest)
    memory[100] = 5;          // Value of A
    memory[101] = 7;          // Value of B
    memory[4] = OP_HALT;     // Terminate after ADD

    run_vm();

    printf("Result at address 102: %u\n", memory[102]);  // Output: 12
    return 0;
}