#include <stddef.h>
#include <inttypes.h>
#include <assert.h>
#include <stdbool.h>

#include "nvim/types.h"
#include "nvim/mbyte.h"
#include "nvim/ascii.h"

const uint8_t utf8len_tab_zero[] = {
  //1 2 3 4 5 6 7 8 9 A B C D E F 0 1 2 3 4 5 6 7 8 9 A B C D E F
  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,  // 0
  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,  // 2
  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,  // 4
  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,  // 6
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // 8
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // A
  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,  // C
  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,6,6,0,0,  // E
};

const uint8_t utf8len_tab[] = {
  // ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?A ?B ?C ?D ?E ?F
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 0?
  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,  // 2?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 3?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 4?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 5?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 6?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 7?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 8?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 9?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // A?
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // B?
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // C?
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // D?
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,  // E?
  4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1,  // F?
};

int utf_ptr2char(const char_u *const p)
{
  if (p[0] < 0x80) {  // Be quick for ASCII.
    return p[0];
  }

  const uint8_t len = utf8len_tab_zero[p[0]];
  if (len > 1 && (p[1] & 0xc0) == 0x80) {
    if (len == 2) {
      return ((p[0] & 0x1f) << 6) + (p[1] & 0x3f);
    }
    if ((p[2] & 0xc0) == 0x80) {
      if (len == 3) {
        return (((p[0] & 0x0f) << 12) + ((p[1] & 0x3f) << 6)
                + (p[2] & 0x3f));
      }
      if ((p[3] & 0xc0) == 0x80) {
        if (len == 4) {
          return (((p[0] & 0x07) << 18) + ((p[1] & 0x3f) << 12)
                  + ((p[2] & 0x3f) << 6) + (p[3] & 0x3f));
        }
        if ((p[4] & 0xc0) == 0x80) {
          if (len == 5) {
            return (((p[0] & 0x03) << 24) + ((p[1] & 0x3f) << 18)
                    + ((p[2] & 0x3f) << 12) + ((p[3] & 0x3f) << 6)
                    + (p[4] & 0x3f));
          }
          if ((p[5] & 0xc0) == 0x80 && len == 6) {
            return (((p[0] & 0x01) << 30) + ((p[1] & 0x3f) << 24)
                    + ((p[2] & 0x3f) << 18) + ((p[3] & 0x3f) << 12)
                    + ((p[4] & 0x3f) << 6) + (p[5] & 0x3f));
          }
        }
      }
    }
  }
  // Illegal value: just return the first byte.
  return p[0];
}

bool utf_composinglike(const char_u *p1, const char_u *p2)
{
  return false;
}

char_u *string_convert(const vimconv_T *conv, char_u *data, size_t *size)
{
  return NULL;
}

int utf_ptr2len_len(const char_u *p, int size)
{
  int len;
  int i;
  int m;

  len = utf8len_tab[*p];
  if (len == 1)
    return 1;           /* NUL, ascii or illegal lead byte */
  if (len > size)
    m = size;           /* incomplete byte sequence. */
  else
    m = len;
  for (i = 1; i < m; ++i)
    if ((p[i] & 0xc0) != 0x80)
      return 1;
  return len;
}

int utfc_ptr2len_len(const char_u *p, int size)
{
  int len;
  int prevlen;

  if (size < 1 || *p == NUL)
    return 0;
  if (p[0] < 0x80 && (size == 1 || p[1] < 0x80))   /* be quick for ASCII */
    return 1;

  /* Skip over first UTF-8 char, stopping at a NUL byte. */
  len = utf_ptr2len_len(p, size);

  /* Check for illegal byte and incomplete byte sequence. */
  if ((len == 1 && p[0] >= 0x80) || len > size)
    return 1;

  /*
   * Check for composing characters.  We can handle only the first six, but
   * skip all of them (otherwise the cursor would get stuck).
   */
  prevlen = 0;
  while (len < size) {
    int len_next_char;

    if (p[len] < 0x80)
      break;

    /*
     * Next character length should not go beyond size to ensure that
     * UTF_COMPOSINGLIKE(...) does not read beyond size.
     */
    len_next_char = utf_ptr2len_len(p + len, size - len);
    if (len_next_char > size - len)
      break;

    if (!UTF_COMPOSINGLIKE(p + prevlen, p + len))
      break;

    /* Skip over composing char */
    prevlen = len;
    len += len_next_char;
  }
  return len;
}

int utf_char2len(const int c)
{
  if (c < 0x80) {
    return 1;
  } else if (c < 0x800) {
    return 2;
  } else if (c < 0x10000) {
    return 3;
  } else if (c < 0x200000) {
    return 4;
  } else if (c < 0x4000000) {
    return 5;
  } else {
    return 6;
  }
}

int utf_char2bytes(const int c, char_u *const buf)
{
  if (c < 0x80) {  // 7 bits
    buf[0] = c;
    return 1;
  } else if (c < 0x800) {  // 11 bits
    buf[0] = 0xc0 + ((unsigned)c >> 6);
    buf[1] = 0x80 + (c & 0x3f);
    return 2;
  } else if (c < 0x10000) {  // 16 bits
    buf[0] = 0xe0 + ((unsigned)c >> 12);
    buf[1] = 0x80 + (((unsigned)c >> 6) & 0x3f);
    buf[2] = 0x80 + (c & 0x3f);
    return 3;
  } else if (c < 0x200000) {  // 21 bits
    buf[0] = 0xf0 + ((unsigned)c >> 18);
    buf[1] = 0x80 + (((unsigned)c >> 12) & 0x3f);
    buf[2] = 0x80 + (((unsigned)c >> 6) & 0x3f);
    buf[3] = 0x80 + (c & 0x3f);
    return 4;
  } else if (c < 0x4000000) {  // 26 bits
    buf[0] = 0xf8 + ((unsigned)c >> 24);
    buf[1] = 0x80 + (((unsigned)c >> 18) & 0x3f);
    buf[2] = 0x80 + (((unsigned)c >> 12) & 0x3f);
    buf[3] = 0x80 + (((unsigned)c >> 6) & 0x3f);
    buf[4] = 0x80 + (c & 0x3f);
    return 5;
  } else {  // 31 bits
    buf[0] = 0xfc + ((unsigned)c >> 30);
    buf[1] = 0x80 + (((unsigned)c >> 24) & 0x3f);
    buf[2] = 0x80 + (((unsigned)c >> 18) & 0x3f);
    buf[3] = 0x80 + (((unsigned)c >> 12) & 0x3f);
    buf[4] = 0x80 + (((unsigned)c >> 6) & 0x3f);
    buf[5] = 0x80 + (c & 0x3f);
    return 6;
  }
}

int utf_ptr2len(const char_u *const p)
{
  if (*p == NUL) {
    return 0;
  }
  const int len = utf8len_tab[*p];
  for (int i = 1; i < len; i++) {
    if ((p[i] & 0xc0) != 0x80) {
      return 1;
    }
  }
  return len;
}

int utfc_ptr2len(const char_u *const p)
{
  uint8_t b0 = (uint8_t)(*p);

  if (b0 == NUL) {
    return 0;
  }
  if (b0 < 0x80 && p[1] < 0x80) {  // be quick for ASCII
    return 1;
  }

  // Skip over first UTF-8 char, stopping at a NUL byte.
  int len = utf_ptr2len(p);

  // Check for illegal byte.
  if (len == 1 && b0 >= 0x80) {
    return 1;
  }

  // Check for composing characters.  We can handle only the first six, but
  // skip all of them (otherwise the cursor would get stuck).
  int prevlen = 0;
  for (;;) {
    if (p[len] < 0x80 || !UTF_COMPOSINGLIKE(p + prevlen, p + len)) {
      return len;
    }

    // Skip over composing char.
    prevlen = len;
    len += utf_ptr2len(p + len);
  }
}

void mb_copy_char(const char_u **fp, char_u **tp)
{
  const size_t l = utfc_ptr2len(*fp);

  memmove(*tp, *fp, (size_t)l);
  *tp += l;
  *fp += l;
}