/*
 * An implementation of what I call the "Sea of Stars" algorithm for
 * POSIX fnmatch(). The basic idea is that we factor the pattern into
 * a head component (which we match first and can reject without ever
 * measuring the length of the string), an optional tail component
 * (which only exists if the pattern contains at least one star), and
 * an optional "sea of stars", a set of star-separated components
 * between the head and tail. After the head and tail matches have
 * been removed from the input string, the components in the "sea of
 * stars" are matched sequentially by searching for their first
 * occurrence past the end of the previous match.
 *
 * - Rich Felker, April 2012
 */

#include <string.h>
#include <fnmatch.h>
#include <stdlib.h>
#include <wchar.h>
#include <wctype.h>
#include "locale_impl.h"

#define END 0
#define UNMATCHABLE -2
#define BRACKET -3
#define QUESTION -4
#define STAR -5

static int str_next(const char* str, size_t n, size_t* step) {
  if (!n) {
    *step = 0;
    return 0;
  }
  if (str[0] >= 128U) {
    wchar_t wc;
    int k = mbtowc(&wc, str, n);
    if (k < 0) {
      *step = 1;
      return -1;
    }
    *step = k;
    return wc;
  }
  *step = 1;
  return str[0];
}

static int pat_next(const char* pat, size_t m, size_t* step, int flags) {
  int esc = 0;
  if (!m || !*pat) {
    *step = 0;
    return END;
  }
  *step = 1;
  if (pat[0] == '\\' && pat[1] && !(flags & FNM_NOESCAPE)) {
    *step = 2;
    pat++;
    esc = 1;
    goto escaped;
  }
  if (pat[0] == '[') {
    size_t k = 1;
    if (k < m)
      if (pat[k] == '^' || pat[k] == '!')
        k++;
    if (k < m)
      if (pat[k] == ']')
        k++;
    for (; k < m && pat[k] && pat[k] != ']'; k++) {
      if (k + 1 < m && pat[k + 1] && pat[k] == '[' &&
          (pat[k + 1] == ':' || pat[k + 1] == '.' || pat[k + 1] == '=')) {
        int z = pat[k + 1];
        k += 2;
        if (k < m && pat[k])
          k++;
        while (k < m && pat[k] && (pat[k - 1] != z || pat[k] != ']'))
          k++;
        if (k == m || !pat[k])
          break;
      }
    }
    if (k == m || !pat[k]) {
      *step = 1;
      return '[';
    }
    *step = k + 1;
    return BRACKET;
  }
  if (pat[0] == '*')
    return STAR;
  if (pat[0] == '?')
    return QUESTION;
escaped:
  if (pat[0] >= 128U) {
    wchar_t wc;
    int k = mbtowc(&wc, pat, m);
    if (k < 0) {
      *step = 0;
      return UNMATCHABLE;
    }
    *step = k + esc;
    return wc;
  }
  return pat[0];
}

static int casefold(int k) {
  int c = towupper(k);
  return c == k ? towlower(k) : c;
}

static int match_bracket(const char* p, int k, int kfold) {
  wchar_t wc;
  int inv = 0;
  p++;
  if (*p == '^' || *p == '!') {
    inv = 1;
    p++;
  }
  if (*p == ']') {
    if (k == ']')
      return !inv;
    p++;
  } else if (*p == '-') {
    if (k == '-')
      return !inv;
    p++;
  }
  wc = p[-1];
  for (; *p != ']'; p++) {
    if (p[0] == '-' && p[1] != ']') {
      wchar_t wc2;
      int l = mbtowc(&wc2, p + 1, 4);
      if (l < 0)
        return 0;
      if (wc <= wc2)
        if ((unsigned)k - wc <= wc2 - wc || (unsigned)kfold - wc <= wc2 - wc)
          return !inv;
      p += l - 1;
      continue;
    }
    if (p[0] == '[' && (p[1] == ':' || p[1] == '.' || p[1] == '=')) {
      const char* p0 = p + 2;
      int z = p[1];
      p += 3;
      while (p[-1] != z || p[0] != ']')
        p++;
      if (z == ':' && p - 1 - p0 < 16) {
        char buf[16];
        memcpy(buf, p0, p - 1 - p0);
        buf[p - 1 - p0] = 0;
        if (iswctype(k, wctype(buf)) || iswctype(kfold, wctype(buf)))
          return !inv;
      }
      continue;
    }
    if (*p < 128U) {
      wc = (unsigned char)*p;
    } else {
      int l = mbtowc(&wc, p, 4);
      if (l < 0)
        return 0;
      p += l - 1;
    }
    if (wc == k || wc == kfold)
      return !inv;
  }
  return inv;
}

static int fnmatch_internal(const char* pat,
                            size_t m,
                            const char* str,
                            size_t n,
                            int flags) {
  const char *p, *ptail, *endpat;
  const char *s, *stail, *endstr;
  size_t pinc, sinc, tailcnt = 0;
  int c, k, kfold;

  if (flags & FNM_PERIOD) {
    if (*str == '.' && *pat != '.')
      return FNM_NOMATCH;
  }
  for (;;) {
    switch ((c = pat_next(pat, m, &pinc, flags))) {
      case UNMATCHABLE:
        return FNM_NOMATCH;
      case STAR:
        pat++;
        m--;
        break;
      default:
        k = str_next(str, n, &sinc);
        if (k <= 0)
          return (c == END) ? 0 : FNM_NOMATCH;
        str += sinc;
        n -= sinc;
        kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
        if (c == BRACKET) {
          if (!match_bracket(pat, k, kfold))
            return FNM_NOMATCH;
        } else if (c != QUESTION && k != c && kfold != c) {
          return FNM_NOMATCH;
        }
        pat += pinc;
        m -= pinc;
        continue;
    }
    break;
  }

  /* Compute real pat length if it was initially unknown/-1 */
  m = strnlen(pat, m);
  endpat = pat + m;

  /* Find the last * in pat and count chars needed after it */
  for (p = ptail = pat; p < endpat; p += pinc) {
    switch (pat_next(p, endpat - p, &pinc, flags)) {
      case UNMATCHABLE:
        return FNM_NOMATCH;
      case STAR:
        tailcnt = 0;
        ptail = p + 1;
        break;
      default:
        tailcnt++;
        break;
    }
  }

  /* Past this point we need not check for UNMATCHABLE in pat,
   * because all of pat has already been parsed once. */

  /* Compute real str length if it was initially unknown/-1 */
  n = strnlen(str, n);
  endstr = str + n;
  if (n < tailcnt)
    return FNM_NOMATCH;

  /* Find the final tailcnt chars of str, accounting for UTF-8.
   * On illegal sequences we may get it wrong, but in that case
   * we necessarily have a matching failure anyway. */
  for (s = endstr; s > str && tailcnt; tailcnt--) {
    if (s[-1] < 128U || MB_CUR_MAX == 1)
      s--;
    else
      while ((unsigned char)*--s - 0x80U < 0x40 && s > str)
        ;
  }
  if (tailcnt)
    return FNM_NOMATCH;
  stail = s;

  /* Check that the pat and str tails match */
  p = ptail;
  for (;;) {
    c = pat_next(p, endpat - p, &pinc, flags);
    p += pinc;
    if ((k = str_next(s, endstr - s, &sinc)) <= 0) {
      if (c != END)
        return FNM_NOMATCH;
      break;
    }
    s += sinc;
    kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
    if (c == BRACKET) {
      if (!match_bracket(p - pinc, k, kfold))
        return FNM_NOMATCH;
    } else if (c != QUESTION && k != c && kfold != c) {
      return FNM_NOMATCH;
    }
  }

  /* We're all done with the tails now, so throw them out */
  endstr = stail;
  endpat = ptail;

  /* Match pattern components until there are none left */
  while (pat < endpat) {
    p = pat;
    s = str;
    for (;;) {
      c = pat_next(p, endpat - p, &pinc, flags);
      p += pinc;
      /* Encountering * completes/commits a component */
      if (c == STAR) {
        pat = p;
        str = s;
        break;
      }
      k = str_next(s, endstr - s, &sinc);
      if (!k)
        return FNM_NOMATCH;
      kfold = flags & FNM_CASEFOLD ? casefold(k) : k;
      if (c == BRACKET) {
        if (!match_bracket(p - pinc, k, kfold))
          break;
      } else if (c != QUESTION && k != c && kfold != c) {
        break;
      }
      s += sinc;
    }
    if (c == STAR)
      continue;
    /* If we failed, advance str, by 1 char if it's a valid
     * char, or past all invalid bytes otherwise. */
    k = str_next(str, endstr - str, &sinc);
    if (k > 0)
      str += sinc;
    else
      for (str++; str_next(str, endstr - str, &sinc) < 0; str++)
        ;
  }

  return 0;
}

int fnmatch(const char* pat, const char* str, int flags) {
  const char *s, *p;
  size_t inc;
  int c;
  if (flags & FNM_PATHNAME)
    for (;;) {
      for (s = str; *s && *s != '/'; s++)
        ;
      for (p = pat; (c = pat_next(p, -1, &inc, flags)) != END && c != '/';
           p += inc)
        ;
      if (c != *s && (!*s || !(flags & FNM_LEADING_DIR)))
        return FNM_NOMATCH;
      if (fnmatch_internal(pat, p - pat, str, s - str, flags))
        return FNM_NOMATCH;
      if (!c)
        return 0;
      str = s + 1;
      pat = p + inc;
    }
  else if (flags & FNM_LEADING_DIR) {
    for (s = str; *s; s++) {
      if (*s != '/')
        continue;
      if (!fnmatch_internal(pat, -1, str, s - str, flags))
        return 0;
    }
  }
  return fnmatch_internal(pat, -1, str, -1, flags);
}