#ifndef SIMDJSON_STRINGPARSING_H
#define SIMDJSON_STRINGPARSING_H

#include "simdjson/common_defs.h"
#include "simdjson/jsoncharutils.h"
#include "simdjson/parsedjson.h"


// begin copypasta
// These chars yield themselves: " \ /
// b -> backspace, f -> formfeed, n -> newline, r -> cr, t -> horizontal tab
// u not handled in this table as it's complex
static const uint8_t escape_map[256] = {
    0, 0, 0,    0, 0,    0, 0,    0, 0, 0, 0, 0, 0,    0, 0,    0, // 0x0.
    0, 0, 0,    0, 0,    0, 0,    0, 0, 0, 0, 0, 0,    0, 0,    0,
    0, 0, 0x22, 0, 0,    0, 0,    0, 0, 0, 0, 0, 0,    0, 0,    0x2f,
    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, // 0x4.
    0, 0, 0,    0, 0,    0, 0,    0, 0, 0, 0, 0, 0x5c, 0, 0,    0, // 0x5.
    0, 0, 0x08, 0, 0,    0, 0x0c, 0, 0, 0, 0, 0, 0,    0, 0x0a, 0, // 0x6.
    0, 0, 0x0d, 0, 0x09, 0, 0,    0, 0, 0, 0, 0, 0,    0, 0,    0, // 0x7.

    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,
    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,

    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,
    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,
};


// handle a unicode codepoint
// write appropriate values into dest
// src will advance 6 bytes or 12 bytes
// dest will advance a variable amount (return via pointer)
// return true if the unicode codepoint was valid
// We work in little-endian then swap at write time
WARN_UNUSED
really_inline bool handle_unicode_codepoint(const uint8_t **src_ptr, uint8_t **dst_ptr) {
  // hex_to_u32_nocheck fills high 16 bits of the return value with 1s if the
  // conversion isn't valid; we defer the check for this to inside the 
  // multilingual plane check
  uint32_t code_point = hex_to_u32_nocheck(*src_ptr + 2);
  *src_ptr += 6;
  // check for low surrogate for characters outside the Basic
  // Multilingual Plane.
  if (code_point >= 0xd800 && code_point < 0xdc00) {
    if (((*src_ptr)[0] != '\\') || (*src_ptr)[1] != 'u') {
      return false;
    }
    uint32_t code_point_2 = hex_to_u32_nocheck(*src_ptr + 2);
    
    // if the first code point is invalid we will get here, as we will go past
    // the check for being outside the Basic Multilingual plane. If we don't
    // find a \u immediately afterwards we fail out anyhow, but if we do, 
    // this check catches both the case of the first code point being invalid
    // or the second code point being invalid.
    if ((code_point | code_point_2) >> 16) {
        return false;
    }

    code_point =
        (((code_point - 0xd800) << 10) | (code_point_2 - 0xdc00)) + 0x10000;
    *src_ptr += 6;
  }
  size_t offset = codepoint_to_utf8(code_point, *dst_ptr);
  *dst_ptr += offset;
  return offset > 0;
}

WARN_UNUSED
really_inline  bool parse_string(const uint8_t *buf, UNUSED size_t len,
                                ParsedJson &pj, UNUSED const uint32_t depth, uint32_t offset) {
#ifdef SIMDJSON_SKIPSTRINGPARSING // for performance analysis, it is sometimes useful to skip parsing
  pj.write_tape(0, '"');// don't bother with the string parsing at all
  return true; // always succeeds
#else
  const uint8_t *src = &buf[offset + 1]; // we know that buf at offset is a "
  uint8_t *dst = pj.current_string_buf_loc;
#ifdef JSON_TEST_STRINGS // for unit testing
  uint8_t *const start_of_string = dst;
#endif
  while (1) {
    __m256i v = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(src));
    auto bs_bits =
        static_cast<uint32_t>(_mm256_movemask_epi8(_mm256_cmpeq_epi8(v, _mm256_set1_epi8('\\'))));
    auto quote_bits =
        static_cast<uint32_t>(_mm256_movemask_epi8(_mm256_cmpeq_epi8(v, _mm256_set1_epi8('"'))));
#define CHECKUNESCAPED
    // All Unicode characters may be placed within the
    // quotation marks, except for the characters that MUST be escaped:
    // quotation mark, reverse solidus, and the control characters (U+0000
    //through U+001F).
    // https://tools.ietf.org/html/rfc8259
#ifdef CHECKUNESCAPED
    __m256i unitsep = _mm256_set1_epi8(0x1F);
    __m256i unescaped_vec = _mm256_cmpeq_epi8(_mm256_max_epu8(unitsep,v),unitsep);// could do it with saturated subtraction
#endif // CHECKUNESCAPED

    uint32_t quote_dist = trailingzeroes(quote_bits);
    uint32_t bs_dist = trailingzeroes(bs_bits);
    // store to dest unconditionally - we can overwrite the bits we don't like
    // later
    _mm256_storeu_si256(reinterpret_cast<__m256i *>(dst), v);
    if (quote_dist < bs_dist) {
      // we encountered quotes first. Move dst to point to quotes and exit
      dst[quote_dist] = 0; // null terminate and get out

      pj.write_tape(pj.current_string_buf_loc - pj.string_buf, '"');

      pj.current_string_buf_loc = dst + quote_dist + 1; // the +1 is due to the 0 value
#ifdef CHECKUNESCAPED
      // check that there is no unescaped char before the quote
      auto unescaped_bits = static_cast<uint32_t>(_mm256_movemask_epi8(unescaped_vec));
      bool is_ok = ((quote_bits - 1) & (~ quote_bits) & unescaped_bits) == 0;
#ifdef JSON_TEST_STRINGS // for unit testing
       if(is_ok) foundString(buf + offset,start_of_string,pj.current_string_buf_loc - 1);
       else  foundBadString(buf + offset);
#endif // JSON_TEST_STRINGS
      return is_ok;
#else  //CHECKUNESCAPED
#ifdef JSON_TEST_STRINGS // for unit testing
       foundString(buf + offset,start_of_string,pj.current_string_buf_loc - 1);
#endif // JSON_TEST_STRINGS
      return true;
#endif //CHECKUNESCAPED
    } if (quote_dist > bs_dist) {
      uint8_t escape_char = src[bs_dist + 1];
#ifdef CHECKUNESCAPED
      // we are going to need the unescaped_bits to check for unescaped chars
      auto unescaped_bits = static_cast<uint32_t>(_mm256_movemask_epi8(unescaped_vec));
      if(((bs_bits - 1) & (~ bs_bits) & unescaped_bits) != 0) {
#ifdef JSON_TEST_STRINGS // for unit testing
        foundBadString(buf + offset);
#endif // JSON_TEST_STRINGS
        return false;
      }
#endif //CHECKUNESCAPED
      // we encountered backslash first. Handle backslash
      if (escape_char == 'u') {
        // move src/dst up to the start; they will be further adjusted
        // within the unicode codepoint handling code.
        src += bs_dist;
        dst += bs_dist;
        if (!handle_unicode_codepoint(&src, &dst)) {
#ifdef JSON_TEST_STRINGS // for unit testing
          foundBadString(buf + offset);
#endif // JSON_TEST_STRINGS
          return false;
        }
      } else {
        // simple 1:1 conversion. Will eat bs_dist+2 characters in input and
        // write bs_dist+1 characters to output
        // note this may reach beyond the part of the buffer we've actually
        // seen. I think this is ok
        uint8_t escape_result = escape_map[escape_char];
        if (escape_result == 0u) {
#ifdef JSON_TEST_STRINGS // for unit testing
          foundBadString(buf + offset);
#endif // JSON_TEST_STRINGS
          return false; // bogus escape value is an error
        }
        dst[bs_dist] = escape_result;
        src += bs_dist + 2;
        dst += bs_dist + 1;
      }
    } else {
      // they are the same. Since they can't co-occur, it means we encountered
      // neither.
      src += 32;
      dst += 32;
#ifdef CHECKUNESCAPED
      // check for unescaped chars
      if(_mm256_testz_si256(unescaped_vec,unescaped_vec) != 1) {
#ifdef JSON_TEST_STRINGS // for unit testing
          foundBadString(buf + offset);
#endif // JSON_TEST_STRINGS
        return false;
      }
#endif // CHECKUNESCAPED
    }
  }
  // can't be reached
  return true;
#endif // SIMDJSON_SKIPSTRINGPARSING
}


#endif