#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

#include "jv.h"

#include "jv_dtoa.h"

#include "jv_unicode.h"

#include "jv_alloc.h"

#include "jv_dtoa.h"

typedef const char* presult;

#ifndef MAX_PARSING_DEPTH

#define MAX_PARSING_DEPTH (10000)

#endif

#define TRY(x) do {presult msg__ = (x); if (msg__) return msg__; } while(0)

#ifdef __GNUC__

#define pfunc __attribute__((warn_unused_result)) presult

#else

#define pfunc presult

#endif

enum last_seen {

  JV_LAST_NONE = 0,

  JV_LAST_OPEN_ARRAY = '[',

  JV_LAST_OPEN_OBJECT = '{',

  JV_LAST_COLON = ':',

  JV_LAST_COMMA = ',',

  JV_LAST_VALUE = 'V',

};

struct jv_parser {

  const char* curr_buf;

  int curr_buf_length;

  int curr_buf_pos;

  int curr_buf_is_partial;

  int eof;

  unsigned bom_strip_position;

  int flags;

  jv* stack;                   // parser

  int stackpos;                // parser

  int stacklen;                // both (optimization; it's really pathlen for streaming)

  jv path;                     // streamer

  enum last_seen last_seen;    // streamer

  jv output;                   // streamer

  jv next;                     // both

  char* tokenbuf;

  int tokenpos;

  int tokenlen;

  int line, column;

  struct dtoa_context dtoa;

  enum {

    JV_PARSER_NORMAL,

    JV_PARSER_STRING,

    JV_PARSER_STRING_ESCAPE,

    JV_PARSER_WAITING_FOR_RS // parse error, waiting for RS

  } st;

  unsigned int last_ch_was_ws:1;

};

static void parser_init(struct jv_parser* p, int flags) {

  p->flags = flags;

  if ((p->flags & JV_PARSE_STREAMING)) {

    p->path = jv_array();

  } else {

    p->path = jv_invalid();

    p->flags &= ~(JV_PARSE_STREAM_ERRORS);

  }

  p->stack = 0;

  p->stacklen = p->stackpos = 0;

  p->last_seen = JV_LAST_NONE;

  p->output = jv_invalid();

  p->next = jv_invalid();

  p->tokenbuf = 0;

  p->tokenlen = p->tokenpos = 0;

  if ((p->flags & JV_PARSE_SEQ))

    p->st = JV_PARSER_WAITING_FOR_RS;

  else

    p->st = JV_PARSER_NORMAL;

  p->eof = 0;

  p->curr_buf = 0;

  p->curr_buf_length = p->curr_buf_pos = p->curr_buf_is_partial = 0;

  p->bom_strip_position = 0;

  p->last_ch_was_ws = 0;

  p->line = 1;

  p->column = 0;

  jvp_dtoa_context_init(&p->dtoa);

}

static void parser_reset(struct jv_parser* p) {

  if ((p->flags & JV_PARSE_STREAMING)) {

    jv_free(p->path);

    p->path = jv_array();

    p->stacklen = 0;

  }

  p->last_seen = JV_LAST_NONE;

  jv_free(p->output);

  p->output = jv_invalid();

  jv_free(p->next);

  p->next = jv_invalid();

  for (int i=0; i<p->stackpos; i++)

    jv_free(p->stack[i]);

  p->stackpos = 0;

  p->tokenpos = 0;

  p->st = JV_PARSER_NORMAL;

}

static void parser_free(struct jv_parser* p) {

  parser_reset(p);

  jv_free(p->path);

  jv_free(p->output);

  jv_mem_free(p->stack);

  jv_mem_free(p->tokenbuf);

  jvp_dtoa_context_free(&p->dtoa);

}

static pfunc value(struct jv_parser* p, jv val) {

  if ((p->flags & JV_PARSE_STREAMING)) {

    if (jv_is_valid(p->next) || p->last_seen == JV_LAST_VALUE) {

      jv_free(val);

      return "Expected separator between values";

    }

    if (p->stacklen > 0)

      p->last_seen = JV_LAST_VALUE;

    else

      p->last_seen = JV_LAST_NONE;

  } else {

    if (jv_is_valid(p->next)) {

      jv_free(val);

      return "Expected separator between values";

    }

  }

  jv_free(p->next);

  p->next = val;

  return 0;

}

static void push(struct jv_parser* p, jv v) {

  assert(p->stackpos <= p->stacklen);

  if (p->stackpos == p->stacklen) {

    p->stacklen = p->stacklen * 2 + 10;

    p->stack = jv_mem_realloc(p->stack, p->stacklen * sizeof(jv));

  }

  assert(p->stackpos < p->stacklen);

  p->stack[p->stackpos++] = v;

}

static pfunc parse_token(struct jv_parser* p, char ch) {

  switch (ch) {

  case '[':

    if (p->stackpos >= MAX_PARSING_DEPTH) return "Exceeds depth limit for parsing";

    if (jv_is_valid(p->next)) return "Expected separator between values";

    push(p, jv_array());

    break;

  case '{':

    if (p->stackpos >= MAX_PARSING_DEPTH) return "Exceeds depth limit for parsing";

    if (jv_is_valid(p->next)) return "Expected separator between values";

    push(p, jv_object());

    break;

  case ':':

    if (!jv_is_valid(p->next))

      return "Expected string key before ':'";

    if (p->stackpos == 0 || jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_OBJECT)

      return "':' not as part of an object";

    if (jv_get_kind(p->next) != JV_KIND_STRING)

      return "Object keys must be strings";

    push(p, p->next);

    p->next = jv_invalid();

    break;

  case ',':

    if (!jv_is_valid(p->next))

      return "Expected value before ','";

    if (p->stackpos == 0)

      return "',' not as part of an object or array";

    if (jv_get_kind(p->stack[p->stackpos-1]) == JV_KIND_ARRAY) {

      p->stack[p->stackpos-1] = jv_array_append(p->stack[p->stackpos-1], p->next);

      p->next = jv_invalid();

    } else if (jv_get_kind(p->stack[p->stackpos-1]) == JV_KIND_STRING) {

      assert(p->stackpos > 1 && jv_get_kind(p->stack[p->stackpos-2]) == JV_KIND_OBJECT);

      p->stack[p->stackpos-2] = jv_object_set(p->stack[p->stackpos-2],

                                              p->stack[p->stackpos-1], p->next);

      p->stackpos--;

      p->next = jv_invalid();

    } else {

      // this case hits on input like {"a", "b"}

      return "Objects must consist of key:value pairs";

    }

    break;

  case ']':

    if (p->stackpos == 0 || jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_ARRAY)

      return "Unmatched ']'";

    if (jv_is_valid(p->next)) {

      p->stack[p->stackpos-1] = jv_array_append(p->stack[p->stackpos-1], p->next);

      p->next = jv_invalid();

    } else {

      if (jv_array_length(jv_copy(p->stack[p->stackpos-1])) != 0) {

        // this case hits on input like [1,2,3,]

        return "Expected another array element";

      }

    }

    jv_free(p->next);

    p->next = p->stack[--p->stackpos];

    break;

  case '}':

    if (p->stackpos == 0)

      return "Unmatched '}'";

    if (jv_is_valid(p->next)) {

      if (jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_STRING)

        return "Objects must consist of key:value pairs";

      assert(p->stackpos > 1 && jv_get_kind(p->stack[p->stackpos-2]) == JV_KIND_OBJECT);

      p->stack[p->stackpos-2] = jv_object_set(p->stack[p->stackpos-2],

                                              p->stack[p->stackpos-1], p->next);

      p->stackpos--;

      p->next = jv_invalid();

    } else {

      if (jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_OBJECT)

        return "Unmatched '}'";

      if (jv_object_length(jv_copy(p->stack[p->stackpos-1])) != 0)

        return "Expected another key-value pair";

    }

    jv_free(p->next);

    p->next = p->stack[--p->stackpos];

    break;

  }

  return 0;

}

static pfunc stream_token(struct jv_parser* p, char ch) {

  jv_kind k;

  jv last;

  switch (ch) {

  case '[':

    if (jv_is_valid(p->next))

      return "Expected a separator between values";

    if (p->last_seen == JV_LAST_OPEN_OBJECT)

      // Looks like {["foo"]}

      return "Expected string key after '{', not '['";

    if (p->last_seen == JV_LAST_COMMA) {

      last = jv_array_get(jv_copy(p->path), p->stacklen - 1);

      k = jv_get_kind(last);

      jv_free(last);

      if (k != JV_KIND_NUMBER)

        // Looks like {"x":"y",["foo"]}

        return "Expected string key after ',' in object, not '['";

    }

    p->path = jv_array_append(p->path, jv_number(0)); // push

    p->last_seen = JV_LAST_OPEN_ARRAY;

    p->stacklen++;

    break;

  case '{':

    if (p->last_seen == JV_LAST_VALUE)

      return "Expected a separator between values";

    if (p->last_seen == JV_LAST_OPEN_OBJECT)

      // Looks like {{"foo":"bar"}}

      return "Expected string key after '{', not '{'";

    if (p->last_seen == JV_LAST_COMMA) {

      last = jv_array_get(jv_copy(p->path), p->stacklen - 1);

      k = jv_get_kind(last);

      jv_free(last);

      if (k != JV_KIND_NUMBER)

        // Looks like {"x":"y",{"foo":"bar"}}

        return "Expected string key after ',' in object, not '{'";

    }

    // Push object key: null, since we don't know it yet

    p->path = jv_array_append(p->path, jv_null()); // push

    p->last_seen = JV_LAST_OPEN_OBJECT;

    p->stacklen++;

    break;

  case ':':

    last = jv_invalid();

    if (p->stacklen == 0 || jv_get_kind(last = jv_array_get(jv_copy(p->path), p->stacklen - 1)) == JV_KIND_NUMBER) {

      jv_free(last);

      return "':' not as part of an object";

    }

    jv_free(last);

    if (!jv_is_valid(p->next) || p->last_seen == JV_LAST_NONE)

      return "Expected string key before ':'";

    if (jv_get_kind(p->next) != JV_KIND_STRING)

      return "Object keys must be strings";

    if (p->last_seen != JV_LAST_VALUE)

      return "':' should follow a key";

    p->last_seen = JV_LAST_COLON;

    p->path = jv_array_set(p->path, p->stacklen - 1, p->next);

    p->next = jv_invalid();

    break;

  case ',':

    if (p->last_seen != JV_LAST_VALUE)

      return "Expected value before ','";

    if (p->stacklen == 0)

      return "',' not as part of an object or array";

    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);

    k = jv_get_kind(last);

    if (k == JV_KIND_NUMBER) {

      int idx = jv_number_value(last);

      if (jv_is_valid(p->next)) {

        p->output = JV_ARRAY(jv_copy(p->path), p->next);

        p->next = jv_invalid();

      }

      p->path = jv_array_set(p->path, p->stacklen - 1, jv_number(idx + 1));

      p->last_seen = JV_LAST_COMMA;

    } else if (k == JV_KIND_STRING) {

      if (jv_is_valid(p->next)) {

        p->output = JV_ARRAY(jv_copy(p->path), p->next);

        p->next = jv_invalid();

      }

      p->path = jv_array_set(p->path, p->stacklen - 1, jv_null()); // ready for another key:value pair

      p->last_seen = JV_LAST_COMMA;

    } else {

      assert(k == JV_KIND_NULL);

      // this case hits on input like {,}

      // make sure to handle input like {"a", "b"} and {"a":, ...}

      jv_free(last);

      return "Objects must consist of key:value pairs";

    }

    jv_free(last);

    break;

  case ']':

    if (p->stacklen == 0)

      return "Unmatched ']' at the top-level";

    if (p->last_seen == JV_LAST_COMMA)

      return "Expected another array element";

    if (p->last_seen == JV_LAST_OPEN_ARRAY)

      assert(!jv_is_valid(p->next));

    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);

    k = jv_get_kind(last);

    jv_free(last);

    if (k != JV_KIND_NUMBER)

      return "Unmatched ']' in the middle of an object";

    if (jv_is_valid(p->next)) {

      p->output = JV_ARRAY(jv_copy(p->path), p->next, jv_true());

      p->next = jv_invalid();

    } else if (p->last_seen != JV_LAST_OPEN_ARRAY) {

      p->output = JV_ARRAY(jv_copy(p->path));

    }

    p->path = jv_array_slice(p->path, 0, --(p->stacklen)); // pop

    //assert(!jv_is_valid(p->next));

    jv_free(p->next);

    p->next = jv_invalid();

    if (p->last_seen == JV_LAST_OPEN_ARRAY)

      p->output = JV_ARRAY(jv_copy(p->path), jv_array()); // Empty arrays are leaves

    if (p->stacklen == 0)

      p->last_seen = JV_LAST_NONE;

    else

      p->last_seen = JV_LAST_VALUE;

    break;

  case '}':

    if (p->stacklen == 0)

      return "Unmatched '}' at the top-level";

    if (p->last_seen == JV_LAST_COMMA)

      return "Expected another key:value pair";

    if (p->last_seen == JV_LAST_OPEN_OBJECT)

      assert(!jv_is_valid(p->next));

    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);

    k = jv_get_kind(last);

    jv_free(last);

    if (k == JV_KIND_NUMBER)

      return "Unmatched '}' in the middle of an array";

    if (jv_is_valid(p->next)) {

      if (k != JV_KIND_STRING)

        return "Objects must consist of key:value pairs";

      p->output = JV_ARRAY(jv_copy(p->path), p->next, jv_true());

      p->next = jv_invalid();

    } else {

      // Perhaps {"a":[]}

      if (p->last_seen == JV_LAST_COLON)

        // Looks like {"a":}

        return "Missing value in key:value pair";

      if (p->last_seen == JV_LAST_COMMA)

        // Looks like {"a":0,}

        return "Expected another key-value pair";

      if (p->last_seen == JV_LAST_OPEN_ARRAY)

        return "Unmatched '}' in the middle of an array";

      if (p->last_seen != JV_LAST_VALUE && p->last_seen != JV_LAST_OPEN_OBJECT)

        return "Unmatched '}'";

      if (p->last_seen != JV_LAST_OPEN_OBJECT)

        p->output = JV_ARRAY(jv_copy(p->path));

    }

    p->path = jv_array_slice(p->path, 0, --(p->stacklen)); // pop

    jv_free(p->next);

    p->next = jv_invalid();

    if (p->last_seen == JV_LAST_OPEN_OBJECT)

      p->output = JV_ARRAY(jv_copy(p->path), jv_object()); // Empty arrays are leaves

    if (p->stacklen == 0)

      p->last_seen = JV_LAST_NONE;

    else

      p->last_seen = JV_LAST_VALUE;

    break;

  }

  return 0;

}

static void tokenadd(struct jv_parser* p, char c) {

  assert(p->tokenpos <= p->tokenlen);

  if (p->tokenpos >= (p->tokenlen - 1)) {

    p->tokenlen = p->tokenlen*2 + 256;

    p->tokenbuf = jv_mem_realloc(p->tokenbuf, p->tokenlen);

  }

  assert(p->tokenpos < p->tokenlen);

  p->tokenbuf[p->tokenpos++] = c;

}

static int unhex4(char* hex) {

  int r = 0;

  for (int i=0; i<4; i++) {

    char c = *hex++;

    int n;

    if ('0' <= c && c <= '9') n = c - '0';

    else if ('a' <= c && c <= 'f') n = c - 'a' + 10;

    else if ('A' <= c && c <= 'F') n = c - 'A' + 10;

    else return -1;

    r <<= 4;

    r |= n;

  }

  return r;

}

static pfunc found_string(struct jv_parser* p) {

  char* in = p->tokenbuf;

  char* out = p->tokenbuf;

  char* end = p->tokenbuf + p->tokenpos;

  while (in < end) {

    char c = *in++;

    if (c == '\\') {

      if (in >= end)

        return "Expected escape character at end of string";

      c = *in++;

      switch (c) {

      case '\\':

      case '"':

      case '/': *out++ = c;    break;

      case 'b': *out++ = '\b'; break;

      case 'f': *out++ = '\f'; break;

      case 't': *out++ = '\t'; break;

      case 'n': *out++ = '\n'; break;

      case 'r': *out++ = '\r'; break;

      case 'u':

        /* ahh, the complicated case */

        if (in + 4 > end)

          return "Invalid \\uXXXX escape";

        int hexvalue = unhex4(in);

        if (hexvalue < 0)

          return "Invalid characters in \\uXXXX escape";

        unsigned long codepoint = (unsigned long)hexvalue;

        in += 4;

        if (0xD800 <= codepoint && codepoint <= 0xDBFF) {

          /* who thought UTF-16 surrogate pairs were a good idea? */

          if (in + 6 > end || in[0] != '\\' || in[1] != 'u')

            return "Invalid \\uXXXX\\uXXXX surrogate pair escape";

          unsigned long surrogate = unhex4(in+2);

          if (!(0xDC00 <= surrogate && surrogate <= 0xDFFF))

            return "Invalid \\uXXXX\\uXXXX surrogate pair escape";

          in += 6;

          codepoint = 0x10000 + (((codepoint - 0xD800) << 10)

                                 |(surrogate - 0xDC00));

        }

        if (codepoint > 0x10FFFF)

          codepoint = 0xFFFD; // U+FFFD REPLACEMENT CHARACTER

        out += jvp_utf8_encode(codepoint, out);

        break;

      default:

        return "Invalid escape";

      }

    } else {

      if (!(c & ~0x1F))

        return "Invalid string: control characters from U+0000 through U+001F must be escaped";

      *out++ = c;

    }

  }

  TRY(value(p, jv_string_sized(p->tokenbuf, out - p->tokenbuf)));

  p->tokenpos = 0;

  return 0;

}

static pfunc check_literal(struct jv_parser* p) {

  if (p->tokenpos == 0) return 0;

  const char* pattern = 0;

  int plen;

  jv v;

  switch (p->tokenbuf[0]) {

  case 't': pattern = "true"; plen = 4; v = jv_true(); break;

  case 'f': pattern = "false"; plen = 5; v = jv_false(); break;

  case '\'':

    return "Invalid string literal; expected \", but got '";

  case 'n':

    // if it starts with 'n', it could be a literal "nan"

    if (p->tokenpos > 1 && p->tokenbuf[1] == 'u') {

      pattern = "null"; plen = 4; v = jv_null();

    }

  }

  if (pattern) {

    if (p->tokenpos != plen) return "Invalid literal";

    for (int i=0; i<plen; i++)

      if (p->tokenbuf[i] != pattern[i])

        return "Invalid literal";

    TRY(value(p, v));

  } else {

    // FIXME: better parser

    p->tokenbuf[p->tokenpos] = 0;

#ifdef USE_DECNUM

    jv number = jv_number_with_literal(p->tokenbuf);

    if (jv_get_kind(number) == JV_KIND_INVALID) {

      return "Invalid numeric literal";

    }

    TRY(value(p, number));

#else

    char *end = 0;

    double d = jvp_strtod(&p->dtoa, p->tokenbuf, &end);

    if (end == 0 || *end != 0) {

      return "Invalid numeric literal";

    }

    TRY(value(p, jv_number(d)));

#endif

  }

  p->tokenpos = 0;

  return 0;

}

typedef enum {

  LITERAL,

  WHITESPACE,

  STRUCTURE,

  QUOTE,

  INVALID

} chclass;

static chclass classify(char c) {

  switch (c) {

  case ' ':

  case '\t':

  case '\r':

  case '\n':

    return WHITESPACE;

  case '"':

    return QUOTE;

  case '[':

  case ',':

  case ']':

  case '{':

  case ':':

  case '}':

    return STRUCTURE;

  default:

    return LITERAL;

  }

}

static const presult OK = "output produced";

static int parse_check_done(struct jv_parser* p, jv* out) {

  if (p->stackpos == 0 && jv_is_valid(p->next)) {

    *out = p->next;

    p->next = jv_invalid();

    return 1;

  } else {

    return 0;

  }

}

static int stream_check_done(struct jv_parser* p, jv* out) {

  if (p->stacklen == 0 && jv_is_valid(p->next)) {

    *out = JV_ARRAY(jv_copy(p->path),p->next);

    p->next = jv_invalid();

    return 1;

  } else if (jv_is_valid(p->output)) {

    if (jv_array_length(jv_copy(p->output)) > 2) {

      // At end of an array or object, necessitating one more output by

      // which to indicate this

      *out = jv_array_slice(jv_copy(p->output), 0, 2);

      p->output = jv_array_slice(p->output, 0, 1);      // arrange one more output

    } else {

      // No further processing needed

      *out = p->output;

      p->output = jv_invalid();

    }

    return 1;

  } else {

    return 0;

  }

}

static int seq_check_truncation(struct jv_parser* p) {

  return (!p->last_ch_was_ws && (p->stackpos > 0 || p->tokenpos > 0 || jv_get_kind(p->next) == JV_KIND_NUMBER));

}

static int stream_seq_check_truncation(struct jv_parser* p) {

  jv_kind k = jv_get_kind(p->next);

  return (p->stacklen > 0 || k == JV_KIND_NUMBER || k == JV_KIND_TRUE || k == JV_KIND_FALSE || k == JV_KIND_NULL);

}

static int parse_is_top_num(struct jv_parser* p) {

  return (p->stackpos == 0 && jv_get_kind(p->next) == JV_KIND_NUMBER);

}

static int stream_is_top_num(struct jv_parser* p) {

  return (p->stacklen == 0 && jv_get_kind(p->next) == JV_KIND_NUMBER);

}

#define check_done(p, o) \

   (((p)->flags & JV_PARSE_STREAMING) ? stream_check_done((p), (o)) : parse_check_done((p), (o)))

#define token(p, ch) \

   (((p)->flags & JV_PARSE_STREAMING) ? stream_token((p), (ch)) : parse_token((p), (ch)))

#define check_truncation(p) \

   (((p)->flags & JV_PARSE_STREAMING) ? stream_seq_check_truncation((p)) : seq_check_truncation((p)))

#define is_top_num(p) \

   (((p)->flags & JV_PARSE_STREAMING) ? stream_is_top_num((p)) : parse_is_top_num((p)))

static pfunc scan(struct jv_parser* p, char ch, jv* out) {

  p->column++;

  if (ch == '\n') {

    p->line++;

    p->column = 0;

  }

  if ((p->flags & JV_PARSE_SEQ)

      && ch == '\036' /* ASCII RS; see draft-ietf-json-sequence-07 */) {

    if (check_truncation(p)) {

      if (check_literal(p) == 0 && is_top_num(p))

        return "Potentially truncated top-level numeric value";

      return "Truncated value";

    }

    TRY(check_literal(p));

    if (p->st == JV_PARSER_NORMAL && check_done(p, out))

      return OK;

    // shouldn't happen?

    assert(!jv_is_valid(*out));

    parser_reset(p);

    jv_free(*out);

    *out = jv_invalid();

    return OK;

  }

  presult answer = 0;

  p->last_ch_was_ws = 0;

  if (p->st == JV_PARSER_NORMAL) {

    chclass cls = classify(ch);

    if (cls == WHITESPACE)

      p->last_ch_was_ws = 1;

    if (cls != LITERAL) {

      TRY(check_literal(p));

      if (check_done(p, out)) answer = OK;

    }

    switch (cls) {

    case LITERAL:

      tokenadd(p, ch);

      break;

    case WHITESPACE:

      break;

    case QUOTE:

      p->st = JV_PARSER_STRING;

      break;

    case STRUCTURE:

      TRY(token(p, ch));

      break;

    case INVALID:

      return "Invalid character";

    }

    if (check_done(p, out)) answer = OK;

  } else {

    if (ch == '"' && p->st == JV_PARSER_STRING) {

      TRY(found_string(p));

      p->st = JV_PARSER_NORMAL;

      if (check_done(p, out)) answer = OK;

    } else {

      tokenadd(p, ch);

      if (ch == '\\' && p->st == JV_PARSER_STRING) {

        p->st = JV_PARSER_STRING_ESCAPE;

      } else {

        p->st = JV_PARSER_STRING;

      }

    }

  }

  return answer;

}

struct jv_parser* jv_parser_new(int flags) {

  struct jv_parser* p = jv_mem_alloc(sizeof(struct jv_parser));

  parser_init(p, flags);

  p->flags = flags;

  return p;

}

void jv_parser_free(struct jv_parser* p) {

  parser_free(p);

  jv_mem_free(p);

}

static const unsigned char UTF8_BOM[] = {0xEF,0xBB,0xBF};

int jv_parser_remaining(struct jv_parser* p) {

  if (p->curr_buf == 0)

    return 0;

  return (p->curr_buf_length - p->curr_buf_pos);

}

void jv_parser_set_buf(struct jv_parser* p, const char* buf, int length, int is_partial) {

  assert((p->curr_buf == 0 || p->curr_buf_pos == p->curr_buf_length)

         && "previous buffer not exhausted");

  while (length > 0 && p->bom_strip_position < sizeof(UTF8_BOM)) {

    if ((unsigned char)*buf == UTF8_BOM[p->bom_strip_position]) {

      // matched a BOM character

      buf++;

      length--;

      p->bom_strip_position++;

    } else {

      if (p->bom_strip_position == 0) {

        // no BOM in this document

        p->bom_strip_position = sizeof(UTF8_BOM);

      } else {

        // malformed BOM (prefix present, rest missing)

        p->bom_strip_position = 0xff;

      }

    }

  }

  p->curr_buf = buf;

  p->curr_buf_length = length;

  p->curr_buf_pos = 0;

  p->curr_buf_is_partial = is_partial;

}

static jv make_error(struct jv_parser*, const char *, ...) JV_PRINTF_LIKE(2, 3);

static jv make_error(struct jv_parser* p, const char *fmt, ...) {

  va_list ap;

  va_start(ap, fmt);

  jv e = jv_string_vfmt(fmt, ap);

  va_end(ap);

  if ((p->flags & JV_PARSE_STREAM_ERRORS))

    return JV_ARRAY(e, jv_copy(p->path));

  return jv_invalid_with_msg(e);

}

jv jv_parser_next(struct jv_parser* p) {

  if (p->eof)

    return jv_invalid();

  if (!p->curr_buf)

    return jv_invalid(); // Need a buffer

  if (p->bom_strip_position == 0xff) {

    if (!(p->flags & JV_PARSE_SEQ))

      return jv_invalid_with_msg(jv_string("Malformed BOM"));

    p->st =JV_PARSER_WAITING_FOR_RS;

    parser_reset(p);

  }

  jv value = jv_invalid();

  if ((p->flags & JV_PARSE_STREAMING) && stream_check_done(p, &value))

    return value;

  char ch;

  presult msg = 0;

  while (!msg && p->curr_buf_pos < p->curr_buf_length) {

    ch = p->curr_buf[p->curr_buf_pos++];

    if (p->st == JV_PARSER_WAITING_FOR_RS) {

      if (ch == '\n') {

        p->line++;

        p->column = 0;

      } else {

        p->column++;

      }

      if (ch == '\036')

        p->st = JV_PARSER_NORMAL;

      continue; // need to resync, wait for RS

    }

    msg = scan(p, ch, &value);

  }

  if (msg == OK) {

    return value;

  } else if (msg) {

    jv_free(value);

    if (ch != '\036' && (p->flags & JV_PARSE_SEQ)) {

      // Skip to the next RS

      p->st = JV_PARSER_WAITING_FOR_RS;

      value = make_error(p, "%s at line %d, column %d (need RS to resync)", msg, p->line, p->column);

      parser_reset(p);

      return value;

    }

    value = make_error(p, "%s at line %d, column %d", msg, p->line, p->column);

    parser_reset(p);

    if (!(p->flags & JV_PARSE_SEQ)) {

      // We're not parsing a JSON text sequence; throw this buffer away.

      // XXX We should fail permanently here.

      p->curr_buf = 0;

      p->curr_buf_pos = 0;

    } // Else ch must be RS; don't clear buf so we can start parsing again after this ch

    return value;

  } else if (p->curr_buf_is_partial) {

    assert(p->curr_buf_pos == p->curr_buf_length);

    // need another buffer

    return jv_invalid();

  } else {

    // at EOF

    p->eof = 1;

    assert(p->curr_buf_pos == p->curr_buf_length);

    jv_free(value);

    if (p->st == JV_PARSER_WAITING_FOR_RS)

      return make_error(p, "Unfinished abandoned text at EOF at line %d, column %d", p->line, p->column);

    if (p->st != JV_PARSER_NORMAL) {

      value = make_error(p, "Unfinished string at EOF at line %d, column %d", p->line, p->column);

      parser_reset(p);

      p->st = JV_PARSER_WAITING_FOR_RS;

      return value;

    }

    if ((msg = check_literal(p))) {

      value = make_error(p, "%s at EOF at line %d, column %d", msg, p->line, p->column);

      parser_reset(p);

      p->st = JV_PARSER_WAITING_FOR_RS;

      return value;

    }

    if (((p->flags & JV_PARSE_STREAMING) && p->stacklen != 0) ||

        (!(p->flags & JV_PARSE_STREAMING) && p->stackpos != 0)) {

      value = make_error(p, "Unfinished JSON term at EOF at line %d, column %d", p->line, p->column);

      parser_reset(p);

      p->st = JV_PARSER_WAITING_FOR_RS;

      return value;

    }

    // p->next is either invalid (nothing here, but no syntax error)

    // or valid (this is the value). either way it's the thing to return

    if ((p->flags & JV_PARSE_STREAMING) && jv_is_valid(p->next)) {

      value = JV_ARRAY(jv_copy(p->path), p->next); // except in streaming mode we've got to make it [path,value]

    } else {

      value = p->next;

    }

    p->next = jv_invalid();

    if ((p->flags & JV_PARSE_SEQ) && !p->last_ch_was_ws && jv_get_kind(value) == JV_KIND_NUMBER) {

      jv_free(value);

      return make_error(p, "Potentially truncated top-level numeric value at EOF at line %d, column %d", p->line, p->column);

    }

    return value;

  }

}

jv jv_parse_sized_custom_flags(const char* string, int length, int flags) {

  struct jv_parser parser;

  parser_init(&parser, flags);

  jv_parser_set_buf(&parser, string, length, 0);

  jv value = jv_parser_next(&parser);

  if (jv_is_valid(value)) {

    jv next = jv_parser_next(&parser);

    if (jv_is_valid(next)) {

      // multiple JSON values, we only wanted one

      jv_free(value);

      jv_free(next);

      value = jv_invalid_with_msg(jv_string("Unexpected extra JSON values"));

    } else if (jv_invalid_has_msg(jv_copy(next))) {

      // parser error after the first JSON value

      jv_free(value);

      value = next;

    } else {

      // a single valid JSON value

      jv_free(next);

    }

  } else if (jv_invalid_has_msg(jv_copy(value))) {

    // parse error, we'll return it

  } else {

    // no value at all

    jv_free(value);

    value = jv_invalid_with_msg(jv_string("Expected JSON value"));

  }

  parser_free(&parser);

  if (!jv_is_valid(value) && jv_invalid_has_msg(jv_copy(value))) {

    jv msg = jv_invalid_get_msg(value);

    value = jv_invalid_with_msg(jv_string_fmt("%s (while parsing '%s')",

                                              jv_string_value(msg),

                                              string));

    jv_free(msg);

  }

  return value;

}

jv jv_parse_sized(const char* string, int length) {

  return jv_parse_sized_custom_flags(string, length, 0);

}

jv jv_parse(const char* string) {

  return jv_parse_sized(string, strlen(string));

}

jv jv_parse_custom_flags(const char* string, int flags) {

  return jv_parse_sized_custom_flags(string, strlen(string), flags);

}