/**
 * Copyright © 2016  Mattias Andrée <maandree@member.fsf.org>
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */
#define _DEFAULT_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <alloca.h>
#include <errno.h>
#include <string.h>


#define t(...)  do { if (__VA_ARGS__) goto fail; } while (0)


static const char* argv0;


char* compare(const char* restrict e, const char* restrict c)
{
  size_t en = strlen(e);
  size_t cn = strlen(c);
  size_t** matrix = alloca((en + 1) * sizeof(size_t*));
  char** path_matrix = alloca((en + 1) * sizeof(char*));
  size_t ei, ci, ri = 0;
  char* rc = NULL;
  
  for (ei = 0; ei <= en; ei++)
    {
      matrix[ei] = alloca((cn + 1) * sizeof(size_t));
      matrix[ei][0] = ei;
      path_matrix[ei] = alloca((cn + 1) * sizeof(char));
      path_matrix[ei][0] = '|';
    }
  for (ci = 0; ci <= cn; ci++)
    {
      matrix[0][ci] = ci;
      path_matrix[0][ci] = '-';
    }
  path_matrix[0][0] = '\0';
  
  e--, c--;
  
  for (ei = 1; ei <= en; ei++)
    for (ci = 1; ci <= cn; ci++)
      {
	size_t d = matrix[ei - 1][ci - 1];
	size_t l = matrix[ei + 0][ci - 1];
	size_t u = matrix[ei - 1][ci + 0];
	size_t lu = 1 + (l < u ? l : u);
	int ch = (e[ei] != c[ci]);
	d += (size_t)ch;
	matrix[ei][ci] = d < lu ? d : lu;
	path_matrix[ei][ci] = d < lu ? (ch ? '\\' : '=') : (l < u ? '-' : '|');
      }
  
  t (!(rc = malloc((en + cn + 2) * sizeof(char))));
  
#if 0
  for (ei = 0; ei <= en; ei++)
    {
      for (ci = 0; ci <= cn; ci++)
	printf("%zu%s", matrix[ei][ci], ci == cn ? "" :
	                                path_matrix[ei][ci + 1] == '-' ? "\033[1;32m-\033[m" : " ");
      printf("\n");
      if (ei < en)
	for (ci = 0; ci < cn; ci++)
	  printf("%s%s", path_matrix[ei + 1][ci + 0] == '|' ? "\033[1;31m|\033[m" : " ",
			 path_matrix[ei + 1][ci + 1] == '\\' ? "\033[1;33m\\\033[m" :
			 path_matrix[ei + 1][ci + 1] == '=' ? "\033[1;39m\\\033[m" : " ");
      printf("\n");
    }
#endif
  
  rc[ri++] = '\0';
  for (ei = en, ci = cn; ei + ci;)
    switch (path_matrix[ei][ci])
      {
      case '=':   ei--, ci--;  rc[ri++] = '=';  break;
      case '\\':  ei--, ci--;  rc[ri++] = '!';  break;
      case '|':   ei--;        rc[ri++] = '-';  break;
      case '-':         ci--;  rc[ri++] = '+';  break;
      default:
	abort();
      }
  rc[ri] = '\0';
  
 fail:
  return rc;
}


int main(int argc, char* argv[])
{
  char* correct;
  char* entered = NULL;
  size_t n = 0;
  void* new;
  char* w;
  char* r;
  char* path = NULL;
  char* path_;
  char* p;
  int rc = 0;
  
  argv0 = argc ? argv[0] : "learn-your-telephone-number";
  if (argc != 2)
    goto usage;
  
  correct = alloca((2 * strlen(argv[1]) + 1) * sizeof(char));
  for (w = correct, r = argv[1]; *r; r++)
    if      (isdigit(*r))  *w++ = *r;
    else if (isalpha(*r))  goto usage;
    else if (*r == '+')    *w++ = '0', *w++ = '0';
  *w = '\0';
  
  t (fprintf(stdout, "Enter your telephone number: ") < 0);
  t (fflush(stdout));
  t (errno = 0, getline(&entered, &n, stdin) < 0);
  n = strlen(entered) - 1;
  entered[n] = '\0';
  
  t (!(new = realloc(entered, (2 * n + 1) * sizeof(char))));
  entered = new;
  memmove(r = (entered + n), w = (entered), n + 1);
  for (; *r; r++)
    if      (isdigit(*r))  *w++ = *r;
    else if (*r == '+')    *w++ = '0', *w++ = '0';
  *w = '\0';
  
  if (!strcmp(entered, correct))
    goto done;
  t (!(path = compare(entered, correct)));
  
  path_ = strchr(path + 1, '\0');
  t (fprintf(stdout, "\033[A\033[KEntered: ") < 0);
  for (p = entered; *--path_;)
    switch (*path_)
      {
      case '=':  t (fprintf(stdout, "\033[39m%c", *p++) < 0);  break;
      case '!':  t (fprintf(stdout, "\033[31m%c", *p++) < 0);  break;
      case '+':  t (fprintf(stdout, " ")                < 0);  break;
      case '-':  t (fprintf(stdout, "\033[31m%c", *p++) < 0);  break;
      }
  t (fprintf(stdout, "\033[m\n") < 0);
  
  path_ = strchr(path + 1, '\0');
  t (fprintf(stdout, "Correct: ") < 0);
  for (p = correct; *--path_;)
    switch (*path_)
      {
      case '=':  t (fprintf(stdout, "\033[39m%c", *p++) < 0);  break;
      case '!':  t (fprintf(stdout, "\033[32m%c", *p++) < 0);  break;
      case '+':  t (fprintf(stdout, "\033[32m%c", *p++) < 0);  break;
      case '-':  t (fprintf(stdout, " ")                < 0);  break;
      }
  t (fprintf(stdout, "\033[m\n") < 0);
  
  rc = 1;
 done:
  free(entered);
  free(path);
  return rc;
 fail:
  rc = 1;
  if (errno == 0)
    goto done;
  perror(argv0);
  rc = 2;
  goto done;
 usage:
  fprintf(stderr, "usage: %s YOUR-TELEPHONE-NUMBER\n", argv0);
  return 2;
}