/* Let's show tux with ls in a utf8 terminal, for the lol.
 * version 2023-09-16
 *
 *Usage:
 * install chafa: apt install chafa
 * cd /tmp
 * wget "https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Tux.svg/506px-Tux.svg.png"
 * chafa 506px-Tux.svg.png > linux.txt
 * gcc -Wall -o funny_ls funny_ls.c
 * mkdir o
 * cd o
 * ../funny_ls < ../linux.txt
 * ls           (shows weird file names)
 * ls --zero    (shows tux)
 * if ls --zero fails (it works with gnu coreutils 9.1), try:
 * ls --literal --show-control-chars -1
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char filename[4096];
int fn_size;

void fn(char *c)
{
  int l = strlen(c);
  if (l + fn_size > 4000) { printf("filename too long\n"); exit(1); }
  strcpy(filename + fn_size, c);
  fn_size += l;
}

void fn_pos(int l, int c)
{
  char pos[32];
  sprintf(pos, "\x1b[%3.3d;%3.3dH", l, c);
  fn(pos);
}

void mk(void)
{
  FILE *f = fopen(filename, "w");
  fclose(f);
  fn_size = 0;
}

char stack[256][256];
int stack_size;

void push(char *s)
{
  if (stack_size == 256) { printf("stack full\n"); exit(1); }
  if (strlen(s) > 200) { printf("string too long\n"); exit(1); }
  strcpy(stack[stack_size], s);
  stack_size++;
}

enum { NEWLINE, ESC, UTF8, END };

int utf8(int c, char *out)
{
  int c0, c1, c2, c3;
  int val;
  c0 = c;

#define V do { printf("bad utf8\n"); exit(1); } while(0)
  *out++ = c0;

  if (c0 == 0xc0 || c0 == 0xc1 || c0 >= 0xf5) V;
  if (!(c0 & 0x80)) {
    val = c0;
  } else
  if ((c0 & 0xe1) == 0xc0) { /* 110xxxxx */
    c = getchar(); if (c == EOF) V; c1 = c;
    if ((c & 0xc0) != 0x80) V;
    val = ((c0 & 0x1f) << 6) | (c1 & 0x3f);
    if (val < 0x80 || val > 0x7ff) V;
    *out++ = c1;
  } else
  if ((c0 & 0xf0) == 0xe0) { /* 1110xxxx */
    c = getchar(); if (c == EOF) V; c1 = c;
    c = getchar(); if (c == EOF) V; c2 = c;
    if ((c1 & 0xc0) != 0x80 ||
        (c2 & 0xc0) != 0x80) V;
    val = ((c0 & 0x0f) << (6*2)) | ((c1 & 0x3f) << 6) | (c2 & 0x3f);
    if (val < 0x800 || val > 0xffff) V;
    *out++ = c1;
    *out++ = c2;
  } else
  if ((c0 & 0xf8) == 0xf0) { /* 11110xxx */
    c = getchar(); if (c == EOF) V; c1 = c;
    c = getchar(); if (c == EOF) V; c2 = c;
    c = getchar(); if (c == EOF) V; c3 = c;
    if ((c1 & 0xc0) != 0x80 ||
        (c2 & 0xc0) != 0x80 ||
        (c3 & 0xc0) != 0x80) V;
    val = ((c0 & 0x07) << (6*3)) | ((c1 & 0x3f) << (6*2)) |
          ((c2 & 0x3f) << 6) | (c3 & 0x3f);
    if (val < 0x10000 || val > 0x10ffff) V;
    *out++ = c1;
    *out++ = c2;
    *out++ = c3;
  } else V;
  /* we don't deal with values > 0xffff */
  if (val > 0xffff) V;
  *out = 0;
  return UTF8;
}

int next(char *v)
{
  int c;
  int out = 0;
  c = getchar();
  if (c == EOF) return END;
  if (c == '\n') return NEWLINE;
  if (c != '\x1b') return utf8(c, v);
  v[out++] = c;
  do {
    if (out == 127) { printf("too long\n"); exit(1); }
    v[out++] = c = getchar();
  } while (c != 'm');
  v[out] = 0;
  return ESC;
}

int main(void)
{
  char v[128];
  int c = 1, l = 1;
  int t;
  int i;

  do {
    t = next(v);
    if (t == NEWLINE) {
      c = 1;
      l++;
    }
    if (t == UTF8) {
      fn_pos(l, c);
      for (i = 0; i < stack_size; i++) fn(stack[i]);
      fn(v);
      mk();
      stack_size = 0;
      c++;
    }
    if (t ==  ESC) {
      push(v);
    }
  } while (t != END);

  l++;
  c = 1;
  fn_pos(l, c);
  fn("\x1b[0m");
  mk();

  c = l = 0;
  fn_pos(0, 0);
  fn("\x1b[2J");
  mk();

  return 0;
}