/*
 * Copyright notice from original mutt:
 * Copyright (C) 2000 Edmund Grimley Evans <edmundo@rano.org>
 *
 * This file is part of mutt-ng, see http://www.muttng.org/.
 * It's licensed under the GNU General Public License,
 * please see the file GPL in the top level source directory.
 */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include "mutt.h"
#include "charset.h"
#include "imap_private.h"

#include "lib/mem.h"

static int Index_64[128] = {
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, 63, -1, -1, -1,
  52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
  -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
  -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
};

static char B64Chars[64] = {
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
  'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
  'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
  't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
  '8', '9', '+', ','
};

/*
 * Convert the data (u7,u7len) from RFC 2060's UTF-7 to UTF-8.
 * The result is null-terminated and returned, and also stored
 * in (*u8,*u8len) if u8 or u8len is non-zero.
 * If input data is invalid, return 0 and don't store anything.
 * RFC 2060 obviously intends the encoding to be unique (see
 * point 5 in section 5.1.3), so we reject any non-canonical
 * form, such as &ACY- (instead of &-) or &AMA-&AMA- (instead
 * of &AMAAwA-).
 */
static char *utf7_to_utf8 (const char *u7, size_t u7len, char **u8,
                           size_t * u8len)
{
  char *buf, *p;
  int b, ch, k;

  p = buf = mem_malloc (u7len + u7len / 8 + 1);

  for (; u7len; u7++, u7len--) {
    if (*u7 == '&') {
      u7++, u7len--;

      if (u7len && *u7 == '-') {
        *p++ = '&';
        continue;
      }

      ch = 0;
      k = 10;
      for (; u7len; u7++, u7len--) {
        if ((*u7 & 0x80) || (b = Index_64[(int) *u7]) == -1)
          break;
        if (k > 0) {
          ch |= b << k;
          k -= 6;
        }
        else {
          ch |= b >> (-k);
          if (ch < 0x80) {
            if (0x20 <= ch && ch < 0x7f)
              /* Printable US-ASCII */
              goto bail;
            *p++ = ch;
          }
          else if (ch < 0x800) {
            *p++ = 0xc0 | (ch >> 6);
            *p++ = 0x80 | (ch & 0x3f);
          }
          else {
            *p++ = 0xe0 | (ch >> 12);
            *p++ = 0x80 | ((ch >> 6) & 0x3f);
            *p++ = 0x80 | (ch & 0x3f);
          }
          ch = (b << (16 + k)) & 0xffff;
          k += 10;
        }
      }
      if (ch || k < 6)
        /* Non-zero or too many extra bits */
        goto bail;
      if (!u7len || *u7 != '-')
        /* BASE64 not properly terminated */
        goto bail;
      if (u7len > 2 && u7[1] == '&' && u7[2] != '-')
        /* Adjacent BASE64 sections */
        goto bail;
    }
    else if (*u7 < 0x20 || *u7 >= 0x7f)
      /* Not printable US-ASCII */
      goto bail;
    else
      *p++ = *u7;
  }
  *p++ = '\0';
  if (u8len)
    *u8len = p - buf;

  mem_realloc (&buf, p - buf);
  if (u8)
    *u8 = buf;
  return buf;

bail:
  mem_free (&buf);
  return 0;
}

/*
 * Convert the data (u8,u8len) from UTF-8 to RFC 2060's UTF-7.
 * The result is null-terminated and returned, and also stored
 * in (*u7,*u7len) if u7 or u7len is non-zero.
 * Unicode characters above U+FFFF are replaced by U+FFFE.
 * If input data is invalid, return 0 and don't store anything.
 */
static char *utf8_to_utf7 (const char *u8, size_t u8len, char **u7,
                           size_t * u7len)
{
  char *buf, *p;
  int ch;
  int n, i, b = 0, k = 0;
  int base64 = 0;

  /*
   * In the worst case we convert 2 chars to 7 chars. For example:
   * "\x10&\x10&..." -> "&ABA-&-&ABA-&-...".
   */
  p = buf = mem_malloc ((u8len / 2) * 7 + 6);

  while (u8len) {
    unsigned char c = *u8;

    if (c < 0x80)
      ch = c, n = 0;
    else if (c < 0xc2)
      goto bail;
    else if (c < 0xe0)
      ch = c & 0x1f, n = 1;
    else if (c < 0xf0)
      ch = c & 0x0f, n = 2;
    else if (c < 0xf8)
      ch = c & 0x07, n = 3;
    else if (c < 0xfc)
      ch = c & 0x03, n = 4;
    else if (c < 0xfe)
      ch = c & 0x01, n = 5;
    else
      goto bail;

    u8++, u8len--;
    if (n > u8len)
      goto bail;
    for (i = 0; i < n; i++) {
      if ((u8[i] & 0xc0) != 0x80)
        goto bail;
      ch = (ch << 6) | (u8[i] & 0x3f);
    }
    if (n > 1 && !(ch >> (n * 5 + 1)))
      goto bail;
    u8 += n, u8len -= n;

    if (ch < 0x20 || ch >= 0x7f) {
      if (!base64) {
        *p++ = '&';
        base64 = 1;
        b = 0;
        k = 10;
      }
      if (ch & ~0xffff)
        ch = 0xfffe;
      *p++ = B64Chars[b | ch >> k];
      k -= 6;
      for (; k >= 0; k -= 6)
        *p++ = B64Chars[(ch >> k) & 0x3f];
      b = (ch << (-k)) & 0x3f;
      k += 16;
    }
    else {
      if (base64) {
        if (k > 10)
          *p++ = B64Chars[b];
        *p++ = '-';
        base64 = 0;
      }
      *p++ = ch;
      if (ch == '&')
        *p++ = '-';
    }
  }

  if (u8len) {
    mem_free (&buf);
    return 0;
  }

  if (base64) {
    if (k > 10)
      *p++ = B64Chars[b];
    *p++ = '-';
  }

  *p++ = '\0';
  if (u7len)
    *u7len = p - buf;
  mem_realloc (&buf, p - buf);
  if (u7)
    *u7 = buf;
  return buf;

bail:
  mem_free (&buf);
  return 0;
}

void imap_utf7_encode (char **s)
{
  if (Charset) {
    char *t = str_dup (*s);

    if (!mutt_convert_string (&t, Charset, "UTF-8", 0)) {
      char *u7 = utf8_to_utf7 (t, strlen (t), NULL, 0);
      mem_free (s);
      *s = u7;
    }
    mem_free (&t);
  }
}

void imap_utf7_decode (char **s)
{
  if (Charset) {
    char *t = utf7_to_utf8 (*s, str_len (*s), 0, 0);

    if (t && !mutt_convert_string (&t, "UTF-8", Charset, 0)) {
      mem_free (s);
      *s = t;
    }
  }
}