#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <malloc.h>
#include <string.h>
#include <sys/mman.h>

#define RAMSIZE 0x1000

extern uint32_t instructions;
extern void reset6502(void);
extern void step6502(void);
extern void nmi6502(void);

uint8_t *ram, *screen, *f000;


uint8_t read6502(uint16_t address) {
  if (address == _END) {
    printf("DONE\n");
    exit(0);
  }
  uint8_t value = 0x00;
  if (address < RAMSIZE) {
    if (address >= RAMSIZE-16) {
      // emulate memory error in uppermost page
      value = ram[address] & 0xf7;
    } else if (address >= 0x0100 && address <= 0x01ff) {
      // simulate broken LSB in stack page
      value = ram[address & 0xfffe];
    } else {
      value = ram[address];
    }
    printf("%08x: READ  %04x -> %02x\n", instructions, address, value);
  } else if (address >= 0x8000 && address <= 0x8fff) {
    // screen buffer is mirrored 4 times, discard upper 2 bytes
    value = screen[address & 0x03ff];
    printf("%08x: READ  %04x -> %02x\n", instructions, address, value);
  } else if (address >= 0xf000) {
    value = f000[address-0xf000];
    printf("%08x: READ  %04x -> %02x\n", instructions, address, value);
  } else {
    printf("%08x: READ  %04x -> not implemented\n", instructions, address);
  }
  return value;
}

void write6502(uint16_t address, uint8_t value) {
  if (address < RAMSIZE) {
    printf("%08x: WRITE %04x <- %02x\n", instructions, address, value);
    // simulate broken LSB in stack page
    if (address >= 0x100 && address <= 0x1ff) {
      ram[address & 0xfffe] = value;
    } else {
      ram[address] = value;
    }
  } else if (address >= 0x8000 && address <= 0x8fff) {
    // Replace non-printable characters with dot
    if (value < 32 || value > 126) {
      value = '.';
    }
    printf("%08x: WRITE %04x <- %02x, SCREEN(%d,%d)\n", instructions, address, value, (address&0x03ff)%40, (address&0x03ff)/40);
    screen[address & 0x03ff] = value;
  } else {
    printf("%08x: WRITE %04x <- %02x; READONLY\n", instructions, address, value);
  }
}

// Trigger a NMI on SIGINT
void intv(int foo) {
  nmi6502();
}

int main() {
  ram = (uint8_t*) malloc(RAMSIZE);
  screen = (uint8_t*) malloc(0x400);
  memset(screen, 'X', 0x400);
  int ffd = open("out/memtest4k-f000-ascii.emu6502.bin", O_RDONLY);
  f000 = mmap(0, 0x1000, PROT_READ, MAP_PRIVATE, ffd, 0);

  reset6502();
  signal(SIGINT, intv);
  while (1) {
    usleep(1);
    step6502();
    printf("pass: %02x, address: %02x%02x\n", ram[4], ram[1], ram[2]);
    printf("┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓\n");
    for (uint8_t row = 0; row < 25; ++row) {
      printf("┃%.40s┃\n", screen + 40*row);
    }
    printf("┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛\n");
  }
  
}