/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2012 Blender Foundation. All rights reserved. */

/** \file
 * \ingroup intern_utf_conv
 */

#include "utfconv.h"

size_t count_utf_8_from_16(const wchar_t *string16)
{
  int i;
  size_t count = 0;
  wchar_t u = 0;
  if (!string16) {
    return 0;
  }

  for (i = 0; (u = string16[i]); i++) {
    if (u < 0x0080) {
      count += 1;
    }
    else {
      if (u < 0x0800) {
        count += 2;
      }
      else {
        if (u < 0xD800) {
          count += 3;
        }
        else {
          if (u < 0xDC00) {
            i++;
            if ((u = string16[i]) == 0) {
              break;
            }
            if (u >= 0xDC00 && u < 0xE000) {
              count += 4;
            }
          }
          else {
            if (u < 0xE000) {
              /* Illegal. */
            }
            else {
              count += 3;
            }
          }
        }
      }
    }
  }

  return ++count;
}

size_t count_utf_16_from_8(const char *string8)
{
  size_t count = 0;
  char u;
  char type = 0;
  unsigned int u32 = 0;

  if (!string8) {
    return 0;
  }

  for (; (u = *string8); string8++) {
    if (type == 0) {
      if ((u & 0x01 << 7) == 0) {
        count++;
        u32 = 0;
        continue;
      }  // 1 utf-8 char
      if ((u & 0x07 << 5) == 0xC0) {
        type = 1;
        u32 = u & 0x1F;
        continue;
      }  // 2 utf-8 char
      if ((u & 0x0F << 4) == 0xE0) {
        type = 2;
        u32 = u & 0x0F;
        continue;
      }  // 3 utf-8 char
      if ((u & 0x1F << 3) == 0xF0) {
        type = 3;
        u32 = u & 0x07;
        continue;
      }  // 4 utf-8 char
      continue;
    }
    if ((u & 0xC0) == 0x80) {
      u32 = (u32 << 6) | (u & 0x3F);
      type--;
    }
    else {
      u32 = 0;
      type = 0;
    }

    if (type == 0) {
      if ((0 < u32 && u32 < 0xD800) || (0xE000 <= u32 && u32 < 0x10000)) {
        count++;
      }
      else if (0x10000 <= u32 && u32 < 0x110000) {
        count += 2;
      }
      u32 = 0;
    }
  }

  return ++count;
}

int conv_utf_16_to_8(const wchar_t *in16, char *out8, size_t size8)
{
  char *out8end = out8 + size8;
  wchar_t u = 0;
  int err = 0;
  if (!size8 || !in16 || !out8) {
    return UTF_ERROR_NULL_IN;
  }
  out8end--;

  for (; out8 < out8end && (u = *in16); in16++, out8++) {
    if (u < 0x0080) {
      *out8 = u;
    }
    else if (u < 0x0800) {
      if (out8 + 1 >= out8end) {
        break;
      }
      *out8++ = (0x3 << 6) | (0x1F & (u >> 6));
      *out8 = (0x1 << 7) | (0x3F & (u));
    }
    else if (u < 0xD800 || u >= 0xE000) {
      if (out8 + 2 >= out8end) {
        break;
      }
      *out8++ = (0x7 << 5) | (0xF & (u >> 12));
      *out8++ = (0x1 << 7) | (0x3F & (u >> 6));
      *out8 = (0x1 << 7) | (0x3F & (u));
    }
    else if (u < 0xDC00) {
      wchar_t u2 = *++in16;

      if (!u2) {
        break;
      }
      if (u2 >= 0xDC00 && u2 < 0xE000) {
        if (out8 + 3 >= out8end) {
          break;
        }
        unsigned int uc = 0x10000 + (u2 - 0xDC00) + ((u - 0xD800) << 10);

        *out8++ = (0xF << 4) | (0x7 & (uc >> 18));
        *out8++ = (0x1 << 7) | (0x3F & (uc >> 12));
        *out8++ = (0x1 << 7) | (0x3F & (uc >> 6));
        *out8 = (0x1 << 7) | (0x3F & (uc));
      }
      else {
        out8--;
        err |= UTF_ERROR_ILLCHAR;
      }
    }
    else if (u < 0xE000) {
      out8--;
      err |= UTF_ERROR_ILLCHAR;
    }
  }

  *out8 = *out8end = 0;

  if (*in16) {
    err |= UTF_ERROR_SMALL;
  }

  return err;
}

int conv_utf_8_to_16(const char *in8, wchar_t *out16, size_t size16)
{
  char u;
  char type = 0;
  unsigned int u32 = 0;
  wchar_t *out16end = out16 + size16;
  int err = 0;
  if (!size16 || !in8 || !out16) {
    return UTF_ERROR_NULL_IN;
  }
  out16end--;

  for (; out16 < out16end && (u = *in8); in8++) {
    if (type == 0) {
      if ((u & 0x01 << 7) == 0) {
        *out16 = u;
        out16++;
        u32 = 0;
        continue;
      }  // 1 utf-8 char
      if ((u & 0x07 << 5) == 0xC0) {
        type = 1;
        u32 = u & 0x1F;
        continue;
      }  // 2 utf-8 char
      if ((u & 0x0F << 4) == 0xE0) {
        type = 2;
        u32 = u & 0x0F;
        continue;
      }  // 3 utf-8 char
      if ((u & 0x1F << 3) == 0xF0) {
        type = 3;
        u32 = u & 0x07;
        continue;
      }  // 4 utf-8 char
      err |= UTF_ERROR_ILLCHAR;
      continue;
    }
    if ((u & 0xC0) == 0x80) {
      u32 = (u32 << 6) | (u & 0x3F);
      type--;
    }
    else {
      u32 = 0;
      type = 0;
      err |= UTF_ERROR_ILLSEQ;
    }

    if (type == 0) {
      if ((0 < u32 && u32 < 0xD800) || (0xE000 <= u32 && u32 < 0x10000)) {
        *out16 = u32;
        out16++;
      }
      else if (0x10000 <= u32 && u32 < 0x110000) {
        if (out16 + 1 >= out16end) {
          break;
        }
        u32 -= 0x10000;
        *out16 = 0xD800 + (u32 >> 10);
        out16++;
        *out16 = 0xDC00 + (u32 & 0x3FF);
        out16++;
      }
      u32 = 0;
    }
  }

  *out16 = *out16end = 0;

  if (*in8) {
    err |= UTF_ERROR_SMALL;
  }

  return err;
}

/* UNUSED FUNCTIONS */
#if 0
static int is_ascii(const char *in8)
{
  for (; *in8; in8++)
    if (0x80 & *in8)
      return 0;

  return 1;
}

static void utf_8_cut_end(char *inout8, size_t maxcutpoint)
{
  char *cur = inout8 + maxcutpoint;
  char cc;
  if (!inout8)
    return;

  cc = *cur;
}
#endif

char *alloc_utf_8_from_16(const wchar_t *in16, size_t add)
{
  size_t bsize = count_utf_8_from_16(in16);
  char *out8 = NULL;
  if (!bsize) {
    return NULL;
  }
  out8 = (char *)malloc(sizeof(char) * (bsize + add));
  conv_utf_16_to_8(in16, out8, bsize);
  return out8;
}

wchar_t *alloc_utf16_from_8(const char *in8, size_t add)
{
  size_t bsize = count_utf_16_from_8(in8);
  wchar_t *out16 = NULL;
  if (!bsize) {
    return NULL;
  }
  out16 = (wchar_t *)malloc(sizeof(wchar_t) * (bsize + add));
  conv_utf_8_to_16(in8, out16, bsize);
  return out16;
}