/*
  Copyright 2011-2020 David Robillard <d@drobilla.net>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include "byte_source.h"
#include "node.h"
#include "reader.h"
#include "serd_internal.h"
#include "stack.h"
#include "string_utils.h"
#include "uri_utils.h"

#include "serd/serd.h"

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define TRY(st, exp)      \
  do {                    \
    if (((st) = (exp))) { \
      return (st);        \
    }                     \
  } while (0)

static inline bool
fancy_syntax(const SerdReader* reader)
{
  return reader->syntax == SERD_TURTLE || reader->syntax == SERD_TRIG;
}

static SerdStatus
read_collection(SerdReader* reader, ReadContext ctx, SerdNode** dest);

static SerdStatus
read_predicateObjectList(SerdReader* reader, ReadContext ctx, bool* ate_dot);

static inline uint8_t
read_HEX(SerdReader* reader)
{
  const int c = peek_byte(reader);
  if (is_xdigit(c)) {
    return (uint8_t)eat_byte_safe(reader, c);
  }

  r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid hexadecimal digit `%c'\n", c);
  return 0;
}

// Read UCHAR escape, initial \ is already eaten by caller
static inline SerdStatus
read_UCHAR(SerdReader* reader, SerdNode* dest, uint32_t* char_code)
{
  const int b      = peek_byte(reader);
  unsigned  length = 0;
  switch (b) {
  case 'U':
    length = 8;
    break;
  case 'u':
    length = 4;
    break;
  default:
    return SERD_ERR_BAD_SYNTAX;
  }
  eat_byte_safe(reader, b);

  uint8_t buf[9] = {0, 0, 0, 0, 0, 0, 0, 0, 0};
  for (unsigned i = 0; i < length; ++i) {
    if (!(buf[i] = read_HEX(reader))) {
      return SERD_ERR_BAD_SYNTAX;
    }
  }

  char*          endptr = NULL;
  const uint32_t code   = (uint32_t)strtoul((const char*)buf, &endptr, 16);
  assert(endptr == (char*)buf + length);

  unsigned size = 0;
  if (code < 0x00000080) {
    size = 1;
  } else if (code < 0x00000800) {
    size = 2;
  } else if (code < 0x00010000) {
    size = 3;
  } else if (code < 0x00110000) {
    size = 4;
  } else {
    r_err(reader,
          SERD_ERR_BAD_SYNTAX,
          "unicode character 0x%X out of range\n",
          code);
    *char_code          = 0xFFFD;
    const SerdStatus st = push_bytes(reader, dest, replacement_char, 3);
    return st ? st : SERD_SUCCESS;
  }

  // Build output in buf
  // (Note # of bytes = # of leading 1 bits in first byte)
  uint32_t c = code;
  switch (size) {
  case 4:
    buf[3] = (uint8_t)(0x80u | (c & 0x3Fu));
    c >>= 6;
    c |= (16 << 12); // set bit 4
                     // fallthru
  case 3:
    buf[2] = (uint8_t)(0x80u | (c & 0x3Fu));
    c >>= 6;
    c |= (32 << 6); // set bit 5
                    // fallthru
  case 2:
    buf[1] = (uint8_t)(0x80u | (c & 0x3Fu));
    c >>= 6;
    c |= 0xC0; // set bits 6 and 7
               // fallthru
  case 1:
    buf[0] = (uint8_t)c;
    // fallthru
  default:
    break;
  }

  *char_code = code;
  return push_bytes(reader, dest, buf, size);
}

// Read ECHAR escape, initial \ is already eaten by caller
static inline SerdStatus
read_ECHAR(SerdReader* reader, SerdNode* dest, SerdNodeFlags* flags)
{
  const int c = peek_byte(reader);
  switch (c) {
  case 't':
    eat_byte_safe(reader, 't');
    return push_byte(reader, dest, '\t');
  case 'b':
    eat_byte_safe(reader, 'b');
    return push_byte(reader, dest, '\b');
  case 'n':
    *flags |= SERD_HAS_NEWLINE;
    eat_byte_safe(reader, 'n');
    return push_byte(reader, dest, '\n');
  case 'r':
    *flags |= SERD_HAS_NEWLINE;
    eat_byte_safe(reader, 'r');
    return push_byte(reader, dest, '\r');
  case 'f':
    eat_byte_safe(reader, 'f');
    return push_byte(reader, dest, '\f');
  case '\\':
  case '"':
  case '\'':
    return push_byte(reader, dest, eat_byte_safe(reader, c));
  default:
    return SERD_ERR_BAD_SYNTAX;
  }
}

static inline SerdStatus
bad_char(SerdReader* reader, const char* fmt, uint8_t c)
{
  // Skip bytes until the next start byte
  for (int b = peek_byte(reader); b != EOF && ((uint8_t)b & 0x80);) {
    eat_byte_safe(reader, b);
    b = peek_byte(reader);
  }

  r_err(reader, SERD_ERR_BAD_SYNTAX, fmt, c);
  return reader->strict ? SERD_ERR_BAD_SYNTAX : SERD_FAILURE;
}

static SerdStatus
read_utf8_bytes(SerdReader* reader, uint8_t bytes[4], uint32_t* size, uint8_t c)
{
  *size = utf8_num_bytes(c);
  if (*size <= 1 || *size > 4) {
    return bad_char(reader, "invalid UTF-8 start 0x%X\n", c);
  }

  bytes[0] = c;
  for (unsigned i = 1; i < *size; ++i) {
    const int b = peek_byte(reader);
    if (b == EOF || ((uint8_t)b & 0x80) == 0) {
      return bad_char(reader, "invalid UTF-8 continuation 0x%X\n", (uint8_t)b);
    }

    eat_byte_safe(reader, b);
    bytes[i] = (uint8_t)b;
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_utf8_character(SerdReader* reader, SerdNode* dest, uint8_t c)
{
  uint32_t   size     = 0;
  uint8_t    bytes[4] = {0, 0, 0, 0};
  SerdStatus st       = read_utf8_bytes(reader, bytes, &size, c);
  if (st) {
    push_bytes(reader, dest, replacement_char, 3);
    return st;
  }

  return push_bytes(reader, dest, bytes, size);
}

static SerdStatus
read_utf8_code(SerdReader* reader, SerdNode* dest, uint32_t* code, uint8_t c)
{
  uint32_t   size     = 0;
  uint8_t    bytes[4] = {0, 0, 0, 0};
  SerdStatus st       = read_utf8_bytes(reader, bytes, &size, c);
  if (st) {
    push_bytes(reader, dest, replacement_char, 3);
    return st;
  }

  if (!(st = push_bytes(reader, dest, bytes, size))) {
    *code = parse_counted_utf8_char(bytes, size);
  }

  return st;
}

// Read one character (possibly multi-byte)
// The first byte, c, has already been eaten by caller
static inline SerdStatus
read_character(SerdReader*    reader,
               SerdNode*      dest,
               SerdNodeFlags* flags,
               uint8_t        c)
{
  if (!(c & 0x80)) {
    switch (c) {
    case 0xA:
    case 0xD:
      *flags |= SERD_HAS_NEWLINE;
      break;
    case '"':
    case '\'':
      *flags |= SERD_HAS_QUOTE;
      break;
    default:
      break;
    }

    return push_byte(reader, dest, c);
  }
  return read_utf8_character(reader, dest, c);
}

// [10] comment ::= '#' ( [^#xA #xD] )*
static void
read_comment(SerdReader* reader)
{
  eat_byte_safe(reader, '#');
  int c = 0;
  while (((c = peek_byte(reader)) != 0xA) && c != 0xD && c != EOF && c) {
    eat_byte_safe(reader, c);
  }
}

// [24] ws ::= #x9 | #xA | #xD | #x20 | comment
static inline bool
read_ws(SerdReader* reader)
{
  const int c = peek_byte(reader);
  switch (c) {
  case 0x9:
  case 0xA:
  case 0xD:
  case 0x20:
    eat_byte_safe(reader, c);
    return true;
  case '#':
    read_comment(reader);
    return true;
  default:
    return false;
  }
}

static inline bool
read_ws_star(SerdReader* reader)
{
  while (read_ws(reader)) {
  }

  return true;
}

static inline bool
peek_delim(SerdReader* reader, const char delim)
{
  read_ws_star(reader);
  return peek_byte(reader) == delim;
}

static inline bool
eat_delim(SerdReader* reader, const char delim)
{
  if (peek_delim(reader, delim)) {
    eat_byte_safe(reader, delim);
    return read_ws_star(reader);
  }

  return false;
}

// STRING_LITERAL_LONG_QUOTE and STRING_LITERAL_LONG_SINGLE_QUOTE
// Initial triple quotes are already eaten by caller
static SerdStatus
read_STRING_LITERAL_LONG(SerdReader*    reader,
                         SerdNode*      ref,
                         SerdNodeFlags* flags,
                         uint8_t        q)
{
  SerdStatus st = SERD_SUCCESS;

  while (!(st && reader->strict)) {
    const int c = peek_byte(reader);
    if (c == '\\') {
      eat_byte_safe(reader, c);
      uint32_t code = 0;
      if ((st = read_ECHAR(reader, ref, flags)) &&
          (st = read_UCHAR(reader, ref, &code))) {
        return r_err(reader, st, "invalid escape `\\%c'\n", peek_byte(reader));
      }
    } else if (c == q) {
      eat_byte_safe(reader, q);
      const int q2 = eat_byte_safe(reader, peek_byte(reader));
      const int q3 = peek_byte(reader);
      if (q2 == q && q3 == q) { // End of string
        eat_byte_safe(reader, q3);
        break;
      }
      *flags |= SERD_HAS_QUOTE;
      push_byte(reader, ref, c);
      st = read_character(reader, ref, flags, (uint8_t)q2);
    } else if (c == EOF) {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "end of file in long string\n");
    } else {
      st =
        read_character(reader, ref, flags, (uint8_t)eat_byte_safe(reader, c));
    }
  }

  return (st && reader->strict) ? st : SERD_SUCCESS;
}

// STRING_LITERAL_QUOTE and STRING_LITERAL_SINGLE_QUOTE
// Initial quote is already eaten by caller
static SerdStatus
read_STRING_LITERAL(SerdReader*    reader,
                    SerdNode*      ref,
                    SerdNodeFlags* flags,
                    uint8_t        q)
{
  SerdStatus st = SERD_SUCCESS;

  while (!(st && reader->strict)) {
    const int c    = peek_byte(reader);
    uint32_t  code = 0;
    switch (c) {
    case EOF:
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "end of file in short string\n");
    case '\n':
    case '\r':
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "line end in short string\n");
    case '\\':
      eat_byte_safe(reader, c);
      if ((st = read_ECHAR(reader, ref, flags)) &&
          (st = read_UCHAR(reader, ref, &code))) {
        return r_err(reader, st, "invalid escape `\\%c'\n", peek_byte(reader));
      }
      break;
    default:
      if (c == q) {
        eat_byte_check(reader, q);
        return SERD_SUCCESS;
      } else {
        st =
          read_character(reader, ref, flags, (uint8_t)eat_byte_safe(reader, c));
      }
    }
  }

  return st ? st
            : (eat_byte_check(reader, q) ? SERD_SUCCESS : SERD_ERR_BAD_SYNTAX);
}

static SerdStatus
read_String(SerdReader* reader, SerdNode* node, SerdNodeFlags* flags)
{
  const int q1 = peek_byte(reader);
  eat_byte_safe(reader, q1);

  const int q2 = peek_byte(reader);
  if (q2 == EOF) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected end of file\n");
  }

  if (q2 != q1) { // Short string (not triple quoted)
    return read_STRING_LITERAL(reader, node, flags, (uint8_t)q1);
  }

  eat_byte_safe(reader, q2);
  const int q3 = peek_byte(reader);
  if (q3 == EOF) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected end of file\n");
  }

  if (q3 != q1) { // Empty short string ("" or '')
    return SERD_SUCCESS;
  }

  if (!fancy_syntax(reader)) {
    return r_err(
      reader, SERD_ERR_BAD_SYNTAX, "syntax does not support long literals\n");
  }

  eat_byte_safe(reader, q3);
  return read_STRING_LITERAL_LONG(reader, node, flags, (uint8_t)q1);
}

static inline bool
is_PN_CHARS_BASE(const uint32_t c)
{
  return ((c >= 0x00C0 && c <= 0x00D6) || (c >= 0x00D8 && c <= 0x00F6) ||
          (c >= 0x00F8 && c <= 0x02FF) || (c >= 0x0370 && c <= 0x037D) ||
          (c >= 0x037F && c <= 0x1FFF) || (c >= 0x200C && c <= 0x200D) ||
          (c >= 0x2070 && c <= 0x218F) || (c >= 0x2C00 && c <= 0x2FEF) ||
          (c >= 0x3001 && c <= 0xD7FF) || (c >= 0xF900 && c <= 0xFDCF) ||
          (c >= 0xFDF0 && c <= 0xFFFD) || (c >= 0x10000 && c <= 0xEFFFF));
}

static SerdStatus
read_PN_CHARS_BASE(SerdReader* reader, SerdNode* dest)
{
  uint32_t   code = 0;
  const int  c    = peek_byte(reader);
  SerdStatus st   = SERD_SUCCESS;
  if (is_alpha(c)) {
    push_byte(reader, dest, eat_byte_safe(reader, c));
  } else if (c == EOF || !(c & 0x80)) {
    return SERD_FAILURE;
  } else if ((st = read_utf8_code(
                reader, dest, &code, (uint8_t)eat_byte_safe(reader, c)))) {
    return st;
  } else if (!is_PN_CHARS_BASE(code)) {
    r_err(
      reader, SERD_ERR_BAD_SYNTAX, "invalid character U+%04X in name\n", code);
    if (reader->strict) {
      return SERD_ERR_BAD_SYNTAX;
    }
  }
  return st;
}

static inline bool
is_PN_CHARS(const uint32_t c)
{
  return (is_PN_CHARS_BASE(c) || c == 0xB7 || (c >= 0x0300 && c <= 0x036F) ||
          (c >= 0x203F && c <= 0x2040));
}

static SerdStatus
read_PN_CHARS(SerdReader* reader, SerdNode* dest)
{
  uint32_t   code = 0;
  const int  c    = peek_byte(reader);
  SerdStatus st   = SERD_SUCCESS;
  if (is_alpha(c) || is_digit(c) || c == '_' || c == '-') {
    push_byte(reader, dest, eat_byte_safe(reader, c));
  } else if (c == EOF || !(c & 0x80)) {
    return SERD_FAILURE;
  } else if ((st = read_utf8_code(
                reader, dest, &code, (uint8_t)eat_byte_safe(reader, c)))) {
    return st;
  } else if (!is_PN_CHARS(code)) {
    return r_err(
      reader, SERD_ERR_BAD_SYNTAX, "invalid character U+%04X in name\n", code);
  }
  return st;
}

static SerdStatus
read_PERCENT(SerdReader* reader, SerdNode* dest)
{
  push_byte(reader, dest, eat_byte_safe(reader, '%'));
  const uint8_t h1 = read_HEX(reader);
  const uint8_t h2 = read_HEX(reader);
  if (h1 && h2) {
    push_byte(reader, dest, h1);
    return push_byte(reader, dest, h2);
  }

  return SERD_ERR_BAD_SYNTAX;
}

static SerdStatus
read_PN_LOCAL_ESC(SerdReader* reader, SerdNode* dest)
{
  eat_byte_safe(reader, '\\');

  const int c = peek_byte(reader);
  switch (c) {
  case '!':
  case '#':
  case '$':
  case '%':
  case '&':
  case '\'':
  case '(':
  case ')':
  case '*':
  case '+':
  case ',':
  case '-':
  case '.':
  case '/':
  case ';':
  case '=':
  case '?':
  case '@':
  case '_':
  case '~':
    push_byte(reader, dest, eat_byte_safe(reader, c));
    break;
  default:
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid escape\n");
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_PLX(SerdReader* reader, SerdNode* dest)
{
  const int c = peek_byte(reader);
  switch (c) {
  case '%':
    return read_PERCENT(reader, dest);
  case '\\':
    return read_PN_LOCAL_ESC(reader, dest);
  default:
    return SERD_FAILURE;
  }
}

static SerdStatus
read_PN_LOCAL(SerdReader* reader, SerdNode* dest, bool* ate_dot)
{
  int        c                      = peek_byte(reader);
  SerdStatus st                     = SERD_SUCCESS;
  bool       trailing_unescaped_dot = false;
  switch (c) {
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9':
  case ':':
  case '_':
    push_byte(reader, dest, eat_byte_safe(reader, c));
    break;
  default:
    if ((st = read_PLX(reader, dest)) > SERD_FAILURE) {
      return r_err(reader, st, "bad escape\n");
    } else if (st != SERD_SUCCESS && read_PN_CHARS_BASE(reader, dest)) {
      return SERD_FAILURE;
    }
  }

  while ((c = peek_byte(reader))) { // Middle: (PN_CHARS | '.' | ':')*
    if (c == '.' || c == ':') {
      push_byte(reader, dest, eat_byte_safe(reader, c));
    } else if ((st = read_PLX(reader, dest)) > SERD_FAILURE) {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "bad escape\n");
    } else if (st != SERD_SUCCESS && (st = read_PN_CHARS(reader, dest))) {
      break;
    }
    trailing_unescaped_dot = (c == '.');
  }

  if (trailing_unescaped_dot) {
    // Ate trailing dot, pop it from stack/node and inform caller
    --dest->n_bytes;
    serd_stack_pop(&reader->stack, 1);
    *ate_dot = true;
  }

  return (st > SERD_FAILURE) ? st : SERD_SUCCESS;
}

// Read the remainder of a PN_PREFIX after some initial characters
static SerdStatus
read_PN_PREFIX_tail(SerdReader* reader, SerdNode* dest)
{
  SerdStatus st = SERD_SUCCESS;
  int        c  = 0;
  while ((c = peek_byte(reader))) { // Middle: (PN_CHARS | '.')*
    if (c == '.') {
      if ((st = push_byte(reader, dest, eat_byte_safe(reader, c)))) {
        return st;
      }
    } else if ((st = read_PN_CHARS(reader, dest))) {
      break;
    }
  }

  if (!st && serd_node_string(dest)[dest->n_bytes - 1] == '.' &&
      read_PN_CHARS(reader, dest)) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "prefix ends with `.'\n");
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_PN_PREFIX(SerdReader* reader, SerdNode* dest)
{
  if (!read_PN_CHARS_BASE(reader, dest)) {
    return read_PN_PREFIX_tail(reader, dest);
  }

  return SERD_FAILURE;
}

static SerdStatus
read_LANGTAG(SerdReader* reader, SerdNode** dest)
{
  int c = peek_byte(reader);
  if (!is_alpha(c)) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected `%c'\n", c);
  }

  if (!(*dest = push_node(reader, SERD_LITERAL, "", 0))) {
    return SERD_ERR_OVERFLOW;
  }

  SerdStatus st = SERD_SUCCESS;
  TRY(st, push_byte(reader, *dest, eat_byte_safe(reader, c)));
  while ((c = peek_byte(reader)) && is_alpha(c)) {
    TRY(st, push_byte(reader, *dest, eat_byte_safe(reader, c)));
  }
  while (peek_byte(reader) == '-') {
    TRY(st, push_byte(reader, *dest, eat_byte_safe(reader, '-')));
    while ((c = peek_byte(reader)) && (is_alpha(c) || is_digit(c))) {
      TRY(st, push_byte(reader, *dest, eat_byte_safe(reader, c)));
    }
  }
  return SERD_SUCCESS;
}

static SerdStatus
read_IRIREF_scheme(SerdReader* reader, SerdNode* dest)
{
  int c = peek_byte(reader);
  if (!is_alpha(c)) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "bad IRI scheme start `%c'\n", c);
  }

  while ((c = peek_byte(reader)) != EOF) {
    if (c == '>') {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "missing IRI scheme\n");
    }

    if (!is_uri_scheme_char(c)) {
      return r_err(reader,
                   SERD_ERR_BAD_SYNTAX,
                   "bad IRI scheme char U+%04X (%c)\n",
                   (unsigned)c,
                   (char)c);
    }

    push_byte(reader, dest, eat_byte_safe(reader, c));
    if (c == ':') {
      return SERD_SUCCESS; // End of scheme
    }
  }

  return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected end of file\n");
}

static SerdStatus
read_IRIREF(SerdReader* reader, SerdNode** dest)
{
  if (!eat_byte_check(reader, '<')) {
    return SERD_ERR_BAD_SYNTAX;
  }

  *dest = push_node(reader, SERD_URI, "", 0);

  if (!fancy_syntax(reader) && read_IRIREF_scheme(reader, *dest)) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "expected IRI scheme\n");
  }

  SerdStatus st   = SERD_SUCCESS;
  uint32_t   code = 0;
  while (!st) {
    const int c = eat_byte_safe(reader, peek_byte(reader));
    switch (c) {
    case '"':
    case '<':
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "invalid IRI character `%c'\n", c);
    case '>':
      return SERD_SUCCESS;
    case '\\':
      if (read_UCHAR(reader, *dest, &code)) {
        return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid IRI escape\n");
      }
      switch (code) {
      case 0:
      case ' ':
      case '<':
      case '>':
        return r_err(reader,
                     SERD_ERR_BAD_SYNTAX,
                     "invalid escaped IRI character U+%04X\n",
                     code);
      default:
        break;
      }
      break;
    case '^':
    case '`':
    case '{':
    case '|':
    case '}':
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "invalid IRI character `%c'\n", c);
    default:
      if (c <= 0x20) {
        r_err(reader,
              SERD_ERR_BAD_SYNTAX,
              "invalid IRI character (escape %%%02X)\n",
              (unsigned)c);
        if (reader->strict) {
          return SERD_ERR_BAD_SYNTAX;
        }
        st = SERD_FAILURE;
        push_byte(reader, *dest, c);
      } else if (!(c & 0x80)) {
        push_byte(reader, *dest, c);
      } else if (read_utf8_character(reader, *dest, (uint8_t)c)) {
        if (reader->strict) {
          return SERD_ERR_BAD_SYNTAX;
        }
      }
    }
  }

  return st;
}

static SerdStatus
read_PrefixedName(SerdReader* reader,
                  SerdNode*   dest,
                  bool        read_prefix,
                  bool*       ate_dot)
{
  SerdStatus st = SERD_SUCCESS;
  if (read_prefix && ((st = read_PN_PREFIX(reader, dest)) > SERD_FAILURE)) {
    return st;
  }

  if (peek_byte(reader) != ':') {
    return SERD_FAILURE;
  }

  push_byte(reader, dest, eat_byte_safe(reader, ':'));

  st = read_PN_LOCAL(reader, dest, ate_dot);

  return (st > SERD_FAILURE) ? st : SERD_SUCCESS;
}

static SerdStatus
read_0_9(SerdReader* reader, SerdNode* str, bool at_least_one)
{
  unsigned   count = 0;
  SerdStatus st    = SERD_SUCCESS;
  for (int c = 0; is_digit((c = peek_byte(reader))); ++count) {
    TRY(st, push_byte(reader, str, eat_byte_safe(reader, c)));
  }

  if (at_least_one && count == 0) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "expected digit\n");
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_number(SerdReader*    reader,
            SerdNode**     dest,
            SerdNode**     datatype,
            SerdNodeFlags* flags,
            bool*          ate_dot)
{
#define XSD_DECIMAL NS_XSD "decimal"
#define XSD_DOUBLE NS_XSD "double"
#define XSD_INTEGER NS_XSD "integer"

  *dest = push_node(reader, SERD_LITERAL, "", 0);

  SerdStatus st          = SERD_SUCCESS;
  int        c           = peek_byte(reader);
  bool       has_decimal = false;
  if (!*dest) {
    return SERD_ERR_OVERFLOW;
  }

  if (c == '-' || c == '+') {
    push_byte(reader, *dest, eat_byte_safe(reader, c));
  }

  if ((c = peek_byte(reader)) == '.') {
    has_decimal = true;
    // decimal case 2 (e.g. '.0' or `-.0' or `+.0')
    push_byte(reader, *dest, eat_byte_safe(reader, c));
    TRY(st, read_0_9(reader, *dest, true));
  } else {
    // all other cases ::= ( '-' | '+' ) [0-9]+ ( . )? ( [0-9]+ )? ...
    TRY(st, read_0_9(reader, *dest, true));
    if ((c = peek_byte(reader)) == '.') {
      has_decimal = true;

      // Annoyingly, dot can be end of statement, so tentatively eat
      eat_byte_safe(reader, c);
      c = peek_byte(reader);
      if (!is_digit(c) && c != 'e' && c != 'E') {
        *ate_dot = true;     // Force caller to deal with stupid grammar
        return SERD_SUCCESS; // Next byte is not a number character
      }

      push_byte(reader, *dest, '.');
      read_0_9(reader, *dest, false);
    }
  }
  c = peek_byte(reader);
  if (c == 'e' || c == 'E') {
    // double
    push_byte(reader, *dest, eat_byte_safe(reader, c));
    switch ((c = peek_byte(reader))) {
    case '+':
    case '-':
      push_byte(reader, *dest, eat_byte_safe(reader, c));
    default:
      break;
    }
    TRY(st, read_0_9(reader, *dest, true));
    *datatype = push_node(reader, SERD_URI, XSD_DOUBLE, sizeof(XSD_DOUBLE) - 1);
  } else if (has_decimal) {
    *datatype =
      push_node(reader, SERD_URI, XSD_DECIMAL, sizeof(XSD_DECIMAL) - 1);
  } else {
    *datatype =
      push_node(reader, SERD_URI, XSD_INTEGER, sizeof(XSD_INTEGER) - 1);
  }

  if (*datatype) {
    *flags |= SERD_HAS_DATATYPE;
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_iri(SerdReader* reader, SerdNode** dest, bool* ate_dot)
{
  switch (peek_byte(reader)) {
  case '<':
    return read_IRIREF(reader, dest);
  default:
    if (!(*dest = push_node(reader, SERD_CURIE, "", 0))) {
      return SERD_ERR_OVERFLOW;
    }
    return read_PrefixedName(reader, *dest, true, ate_dot);
  }
}

static SerdStatus
read_literal(SerdReader*    reader,
             SerdNode**     dest,
             SerdNode**     datatype,
             SerdNode**     lang,
             SerdNodeFlags* flags,
             bool*          ate_dot)
{
  *dest = push_node(reader, SERD_LITERAL, "", 0);

  SerdStatus st = read_String(reader, *dest, flags);
  if (st) {
    *dest = NULL;
    return st;
  }

  switch (peek_byte(reader)) {
  case '@':
    eat_byte_safe(reader, '@');
    *flags |= SERD_HAS_LANGUAGE;
    if ((st = read_LANGTAG(reader, lang))) {
      return r_err(reader, st, "bad literal\n");
    }
    break;
  case '^':
    eat_byte_safe(reader, '^');
    eat_byte_check(reader, '^');
    *flags |= SERD_HAS_DATATYPE;
    if ((st = read_iri(reader, datatype, ate_dot))) {
      return r_err(reader, st, "bad literal\n");
    }
    break;
  }
  return SERD_SUCCESS;
}

static SerdStatus
read_verb(SerdReader* reader, SerdNode** dest)
{
  const size_t orig_stack_size = reader->stack.size;
  if (peek_byte(reader) == '<') {
    return read_IRIREF(reader, dest);
  }

  /* Either a qname, or "a".  Read the prefix first, and if it is in fact
     "a", produce that instead.
  */
  if (!(*dest = push_node(reader, SERD_CURIE, "", 0))) {
    return SERD_ERR_OVERFLOW;
  }

  SerdStatus st      = read_PN_PREFIX(reader, *dest);
  bool       ate_dot = false;
  SerdNode*  node    = *dest;
  const int  next    = peek_byte(reader);
  if (!st && node->n_bytes == 1 && serd_node_string(node)[0] == 'a' &&
      next != ':' && !is_PN_CHARS_BASE((uint32_t)next)) {
    serd_stack_pop_to(&reader->stack, orig_stack_size);
    *dest = push_node(reader, SERD_URI, NS_RDF "type", 47);
    return SERD_SUCCESS;
  }

  if (st > SERD_FAILURE || read_PrefixedName(reader, *dest, false, &ate_dot) ||
      ate_dot) {
    *dest = NULL;
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "bad verb\n");
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_BLANK_NODE_LABEL(SerdReader* reader, SerdNode** dest, bool* ate_dot)
{
  eat_byte_safe(reader, '_');
  eat_byte_check(reader, ':');

  SerdNode* n = *dest = push_node(reader,
                                  SERD_BLANK,
                                  reader->bprefix ? reader->bprefix : "",
                                  reader->bprefix_len);

  int c = peek_byte(reader); // First: (PN_CHARS | '_' | [0-9])
  if (is_digit(c) || c == '_') {
    push_byte(reader, n, eat_byte_safe(reader, c));
  } else if (read_PN_CHARS(reader, n)) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid name start\n");
  }

  while ((c = peek_byte(reader))) { // Middle: (PN_CHARS | '.')*
    if (c == '.') {
      push_byte(reader, n, eat_byte_safe(reader, c));
    } else if (read_PN_CHARS(reader, n)) {
      break;
    }
  }

  char* buf = serd_node_buffer(n);
  if (buf[n->n_bytes - 1] == '.' && read_PN_CHARS(reader, n)) {
    // Ate trailing dot, pop it from stack/node and inform caller
    --n->n_bytes;
    serd_stack_pop(&reader->stack, 1);
    *ate_dot = true;
  }

  if (fancy_syntax(reader)) {
    if (is_digit(buf[reader->bprefix_len + 1])) {
      if ((buf[reader->bprefix_len]) == 'b') {
        buf[reader->bprefix_len] = 'B'; // Prevent clash
        reader->seen_genid       = true;
      } else if (reader->seen_genid && buf[reader->bprefix_len] == 'B') {
        return r_err(reader,
                     SERD_ERR_ID_CLASH,
                     "found both `b' and `B' blank IDs, prefix required\n");
      }
    }
  }
  return SERD_SUCCESS;
}

static SerdNode*
read_blankName(SerdReader* reader)
{
  eat_byte_safe(reader, '=');
  if (eat_byte_check(reader, '=') != '=') {
    r_err(reader, SERD_ERR_BAD_SYNTAX, "expected `='\n");
    return NULL;
  }

  SerdNode* subject = 0;
  bool      ate_dot = false;
  read_ws_star(reader);
  read_iri(reader, &subject, &ate_dot);
  return subject;
}

static SerdStatus
read_anon(SerdReader* reader, ReadContext ctx, bool subject, SerdNode** dest)
{
  const SerdStatementFlags old_flags = *ctx.flags;
  bool                     empty     = false;
  eat_byte_safe(reader, '[');
  if ((empty = peek_delim(reader, ']'))) {
    *ctx.flags |= (subject) ? SERD_EMPTY_S : SERD_EMPTY_O;
  } else {
    *ctx.flags |= (subject) ? SERD_ANON_S_BEGIN : SERD_ANON_O_BEGIN;
    if (peek_delim(reader, '=')) {
      if (!(*dest = read_blankName(reader)) || !eat_delim(reader, ';')) {
        return SERD_ERR_BAD_SYNTAX;
      }
    }
  }

  if (!*dest) {
    *dest = blank_id(reader);
  }

  SerdStatus st = SERD_SUCCESS;
  if (ctx.subject) {
    TRY(st, emit_statement(reader, ctx, *dest));
  }

  ctx.subject = *dest;
  if (!empty) {
    *ctx.flags &= ~(unsigned)SERD_LIST_CONT;
    if (!subject) {
      *ctx.flags |= SERD_ANON_CONT;
    }
    bool ate_dot_in_list = false;
    read_predicateObjectList(reader, ctx, &ate_dot_in_list);
    if (ate_dot_in_list) {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "`.' inside blank\n");
    }
    read_ws_star(reader);
    serd_sink_write_end(reader->sink, *dest);
    *ctx.flags = old_flags;
  }
  return (eat_byte_check(reader, ']') == ']') ? SERD_SUCCESS
                                              : SERD_ERR_BAD_SYNTAX;
}

/* If emit is true: recurses, calling statement_sink for every statement
   encountered, and leaves stack in original calling state (i.e. pops
   everything it pushes). */
static SerdStatus
read_object(SerdReader* reader, ReadContext* ctx, bool emit, bool* ate_dot)
{
  static const char* const XSD_BOOLEAN     = NS_XSD "boolean";
  static const size_t      XSD_BOOLEAN_LEN = 40;

  const size_t orig_stack_size = reader->stack.size;

  SerdStatus ret = SERD_FAILURE;

  bool      simple   = (ctx->subject != 0);
  SerdNode* o        = 0;
  SerdNode* datatype = 0;
  SerdNode* lang     = 0;
  uint32_t  flags    = 0;
  const int c        = peek_byte(reader);
  if (!fancy_syntax(reader)) {
    switch (c) {
    case '"':
    case ':':
    case '<':
    case '_':
      break;
    default:
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "expected: ':', '<', or '_'\n");
    }
  }
  switch (c) {
  case EOF:
  case ')':
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "expected object\n");
  case '[':
    simple = false;
    ret    = read_anon(reader, *ctx, false, &o);
    break;
  case '(':
    simple = false;
    ret    = read_collection(reader, *ctx, &o);
    break;
  case '_':
    ret = read_BLANK_NODE_LABEL(reader, &o, ate_dot);
    break;
  case '<':
  case ':':
    ret = read_iri(reader, &o, ate_dot);
    break;
  case '+':
  case '-':
  case '.':
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9':
    ret = read_number(reader, &o, &datatype, &flags, ate_dot);
    break;
  case '\"':
  case '\'':
    ret = read_literal(reader, &o, &datatype, &lang, &flags, ate_dot);
    break;
  default:
    /* Either a boolean literal, or a qname.  Read the prefix first, and if
       it is in fact a "true" or "false" literal, produce that instead.
    */
    if (!(o = push_node(reader, SERD_CURIE, "", 0))) {
      return SERD_ERR_OVERFLOW;
    }

    while (!read_PN_CHARS_BASE(reader, o)) {
    }
    if ((o->n_bytes == 4 && !memcmp(serd_node_string(o), "true", 4)) ||
        (o->n_bytes == 5 && !memcmp(serd_node_string(o), "false", 5))) {
      flags    = flags | SERD_HAS_DATATYPE;
      o->type  = SERD_LITERAL;
      datatype = push_node(reader, SERD_URI, XSD_BOOLEAN, XSD_BOOLEAN_LEN);
      ret      = SERD_SUCCESS;
    } else if (read_PN_PREFIX_tail(reader, o) > SERD_FAILURE) {
      ret = SERD_ERR_BAD_SYNTAX;
    } else {
      if ((ret = read_PrefixedName(reader, o, false, ate_dot))) {
        ret = ret > SERD_FAILURE ? ret : SERD_ERR_BAD_SYNTAX;
        return r_err(reader, ret, "expected prefixed name\n");
      }
    }
  }

  if (!ret && simple && o) {
    o->flags = flags;
  }

  if (!ret && emit && simple) {
    ret = emit_statement(reader, *ctx, o);
  } else if (!ret && !emit) {
    ctx->object   = o;
    ctx->datatype = datatype;
    ctx->lang     = lang;
    return SERD_SUCCESS;
  }

  serd_stack_pop_to(&reader->stack, orig_stack_size);
#ifndef NDEBUG
  assert(reader->stack.size == orig_stack_size);
#endif
  return ret;
}

static SerdStatus
read_objectList(SerdReader* reader, ReadContext ctx, bool* ate_dot)
{
  SerdStatus st = SERD_SUCCESS;
  TRY(st, read_object(reader, &ctx, true, ate_dot));
  if (!fancy_syntax(reader) && peek_delim(reader, ',')) {
    return r_err(
      reader, SERD_ERR_BAD_SYNTAX, "syntax does not support abbreviation\n");
  }

  while (!*ate_dot && eat_delim(reader, ',')) {
    st = read_object(reader, &ctx, true, ate_dot);
  }

  return st;
}

static SerdStatus
read_predicateObjectList(SerdReader* reader, ReadContext ctx, bool* ate_dot)
{
  const size_t orig_stack_size = reader->stack.size;

  SerdStatus st = SERD_SUCCESS;
  while (!(st = read_verb(reader, &ctx.predicate)) && read_ws_star(reader) &&
         !(st = read_objectList(reader, ctx, ate_dot))) {
    if (*ate_dot) {
      serd_stack_pop_to(&reader->stack, orig_stack_size);
      return SERD_SUCCESS;
    }

    bool ate_semi = false;
    int  c        = 0;
    do {
      read_ws_star(reader);
      switch (c = peek_byte(reader)) {
      case EOF:
        serd_stack_pop_to(&reader->stack, orig_stack_size);
        return r_err(reader, SERD_ERR_BAD_SYNTAX, "unexpected end of file\n");
      case '.':
      case ']':
      case '}':
        serd_stack_pop_to(&reader->stack, orig_stack_size);
        return SERD_SUCCESS;
      case ';':
        eat_byte_safe(reader, c);
        ate_semi = true;
      }
    } while (c == ';');

    if (!ate_semi) {
      serd_stack_pop_to(&reader->stack, orig_stack_size);
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "missing ';' or '.'\n");
    }
  }

  serd_stack_pop_to(&reader->stack, orig_stack_size);
  ctx.predicate = 0;
  return st;
}

static SerdStatus
end_collection(SerdReader* reader, ReadContext ctx, SerdStatus st)
{
  *ctx.flags &= ~(unsigned)SERD_LIST_CONT;
  if (!st) {
    return (eat_byte_check(reader, ')') == ')') ? SERD_SUCCESS
                                                : SERD_ERR_BAD_SYNTAX;
  }
  return st;
}

static SerdStatus
read_collection(SerdReader* reader, ReadContext ctx, SerdNode** dest)
{
  SerdStatus st = SERD_SUCCESS;
  eat_byte_safe(reader, '(');
  bool end = peek_delim(reader, ')');
  *dest    = end ? reader->rdf_nil : blank_id(reader);
  if (ctx.subject) {
    // subject predicate _:head
    *ctx.flags |= (end ? 0 : SERD_LIST_O_BEGIN);
    TRY(st, emit_statement(reader, ctx, *dest));
    *ctx.flags |= SERD_LIST_CONT;
  } else {
    *ctx.flags |= (end ? 0 : SERD_LIST_S_BEGIN);
  }

  if (end) {
    return end_collection(reader, ctx, st);
  }

  /* The order of node allocation here is necessarily not in stack order,
     so we create two nodes and recycle them throughout. */
  SerdNode* n1 =
    push_node_padded(reader, genid_size(reader), SERD_BLANK, "", 0);
  SerdNode* node = n1;
  SerdNode* rest = 0;

  if (!n1) {
    return SERD_ERR_OVERFLOW;
  }

  ctx.subject = *dest;
  while (!peek_delim(reader, ')')) {
    // _:node rdf:first object
    ctx.predicate = reader->rdf_first;
    bool ate_dot  = false;
    if ((st = read_object(reader, &ctx, true, &ate_dot)) || ate_dot) {
      return end_collection(reader, ctx, st);
    }

    if (!(end = peek_delim(reader, ')'))) {
      /* Give rest a new ID.  Done as late as possible to ensure it is
         used and > IDs generated by read_object above. */
      if (!rest) {
        rest = blank_id(reader); // First pass, push
      } else {
        set_blank_id(reader, rest, genid_size(reader));
      }
    }

    // _:node rdf:rest _:rest
    *ctx.flags |= SERD_LIST_CONT;
    ctx.predicate = reader->rdf_rest;
    TRY(st, emit_statement(reader, ctx, (end ? reader->rdf_nil : rest)));

    ctx.subject = rest;        // _:node = _:rest
    rest        = node;        // _:rest = (old)_:node
    node        = ctx.subject; // invariant
  }

  return end_collection(reader, ctx, st);
}

static SerdStatus
read_subject(SerdReader* reader, ReadContext ctx, SerdNode** dest, int* s_type)
{
  SerdStatus st      = SERD_SUCCESS;
  bool       ate_dot = false;
  switch ((*s_type = peek_byte(reader))) {
  case '[':
    read_anon(reader, ctx, true, dest);
    break;
  case '(':
    st = read_collection(reader, ctx, dest);
    break;
  case '_':
    st = read_BLANK_NODE_LABEL(reader, dest, &ate_dot);
    break;
  default:
    st = read_iri(reader, dest, &ate_dot);
  }

  if (ate_dot) {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "subject ends with `.'\n");
  }

  return st;
}

static SerdStatus
read_labelOrSubject(SerdReader* reader, SerdNode** dest)
{
  bool ate_dot = false;
  switch (peek_byte(reader)) {
  case '[':
    eat_byte_safe(reader, '[');
    read_ws_star(reader);
    if (!eat_byte_check(reader, ']')) {
      return SERD_ERR_BAD_SYNTAX;
    }
    *dest = blank_id(reader);
    return SERD_SUCCESS;
  case '_':
    return read_BLANK_NODE_LABEL(reader, dest, &ate_dot);
  default:
    if (!read_iri(reader, dest, &ate_dot)) {
      return SERD_SUCCESS;
    } else {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "expected label or subject\n");
    }
  }
}

static SerdStatus
read_triples(SerdReader* reader, ReadContext ctx, bool* ate_dot)
{
  SerdStatus st = SERD_FAILURE;
  if (ctx.subject) {
    read_ws_star(reader);
    switch (peek_byte(reader)) {
    case '.':
      *ate_dot = eat_byte_safe(reader, '.');
      return SERD_FAILURE;
    case '}':
      return SERD_FAILURE;
    }
    st = read_predicateObjectList(reader, ctx, ate_dot);
  }

  ctx.subject = ctx.predicate = 0;
  return st > SERD_FAILURE ? st : SERD_SUCCESS;
}

static SerdStatus
read_base(SerdReader* reader, bool sparql, bool token)
{
  SerdStatus st = SERD_SUCCESS;
  if (token) {
    TRY(st, eat_string(reader, "base", 4));
  }

  read_ws_star(reader);

  SerdNode* uri = NULL;
  TRY(st, read_IRIREF(reader, &uri));
  TRY(st, serd_sink_write_base(reader->sink, uri));

  read_ws_star(reader);
  if (!sparql) {
    return eat_byte_check(reader, '.') ? SERD_SUCCESS : SERD_ERR_BAD_SYNTAX;
  }

  if (peek_byte(reader) == '.') {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "full stop after SPARQL BASE\n");
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_prefixID(SerdReader* reader, bool sparql, bool token)
{
  SerdStatus st = SERD_SUCCESS;
  if (token) {
    TRY(st, eat_string(reader, "prefix", 6));
  }

  read_ws_star(reader);
  SerdNode* name = push_node(reader, SERD_LITERAL, "", 0);
  if (!name) {
    return SERD_ERR_OVERFLOW;
  }

  if ((st = read_PN_PREFIX(reader, name)) > SERD_FAILURE) {
    return st;
  }

  if (eat_byte_check(reader, ':') != ':') {
    return SERD_ERR_BAD_SYNTAX;
  }

  read_ws_star(reader);
  SerdNode* uri = NULL;
  TRY(st, read_IRIREF(reader, &uri));

  st = serd_sink_write_prefix(reader->sink, name, uri);

  if (!sparql) {
    read_ws_star(reader);
    st = eat_byte_check(reader, '.') ? SERD_SUCCESS : SERD_ERR_BAD_SYNTAX;
  }
  return st;
}

static SerdStatus
read_directive(SerdReader* reader)
{
  const bool sparql = peek_byte(reader) != '@';
  if (!sparql) {
    eat_byte_safe(reader, '@');
    switch (peek_byte(reader)) {
    case 'B':
    case 'P':
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "uppercase directive\n");
    }
  }

  switch (peek_byte(reader)) {
  case 'B':
  case 'b':
    return read_base(reader, sparql, true);
  case 'P':
  case 'p':
    return read_prefixID(reader, sparql, true);
  default:
    break;
  }

  return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid directive\n");
}

static SerdStatus
read_wrappedGraph(SerdReader* reader, ReadContext* ctx)
{
  if (!eat_byte_check(reader, '{')) {
    return SERD_ERR_BAD_SYNTAX;
  }

  read_ws_star(reader);
  while (peek_byte(reader) != '}') {
    const size_t orig_stack_size = reader->stack.size;
    bool         ate_dot         = false;
    int          s_type          = 0;

    ctx->subject  = 0;
    SerdStatus st = read_subject(reader, *ctx, &ctx->subject, &s_type);
    if (st) {
      return r_err(reader, SERD_ERR_BAD_SYNTAX, "bad subject\n");
    }

    if (read_triples(reader, *ctx, &ate_dot) && s_type != '[') {
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "missing predicate object list\n");
    }

    serd_stack_pop_to(&reader->stack, orig_stack_size);
    read_ws_star(reader);
    if (peek_byte(reader) == '.') {
      eat_byte_safe(reader, '.');
    }
    read_ws_star(reader);
  }

  eat_byte_safe(reader, '}');
  read_ws_star(reader);
  if (peek_byte(reader) == '.') {
    return r_err(reader, SERD_ERR_BAD_SYNTAX, "graph followed by `.'\n");
  }

  return SERD_SUCCESS;
}

static int
tokcmp(SerdNode* node, const char* tok, size_t n)
{
  return ((!node || node->n_bytes != n)
            ? -1
            : serd_strncasecmp(serd_node_string(node), tok, n));
}

SerdStatus
read_n3_statement(SerdReader* reader)
{
  SerdStatementFlags flags   = 0;
  ReadContext        ctx     = {0, 0, 0, 0, 0, 0, &flags};
  bool               ate_dot = false;
  int                s_type  = 0;
  SerdStatus         st      = SERD_SUCCESS;
  read_ws_star(reader);
  switch (peek_byte(reader)) {
  case '\0':
    eat_byte_safe(reader, '\0');
    return SERD_FAILURE;
  case EOF:
    return SERD_FAILURE;
  case '@':
    if (!fancy_syntax(reader)) {
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "syntax does not support directives\n");
    }
    TRY(st, read_directive(reader));
    read_ws_star(reader);
    break;
  case '{':
    if (reader->syntax == SERD_TRIG) {
      TRY(st, read_wrappedGraph(reader, &ctx));
      read_ws_star(reader);
    } else {
      return r_err(
        reader, SERD_ERR_BAD_SYNTAX, "syntax does not support graphs\n");
    }
    break;
  default:
    if ((st = read_subject(reader, ctx, &ctx.subject, &s_type)) >
        SERD_FAILURE) {
      return st;
    }

    if (!tokcmp(ctx.subject, "base", 4)) {
      st = read_base(reader, true, false);
    } else if (!tokcmp(ctx.subject, "prefix", 6)) {
      st = read_prefixID(reader, true, false);
    } else if (!tokcmp(ctx.subject, "graph", 5)) {
      read_ws_star(reader);
      TRY(st, read_labelOrSubject(reader, &ctx.graph));
      read_ws_star(reader);
      TRY(st, read_wrappedGraph(reader, &ctx));
      ctx.graph = 0;
      read_ws_star(reader);
    } else if (read_ws_star(reader) && peek_byte(reader) == '{') {
      if (s_type == '(' || (s_type == '[' && !*ctx.flags)) {
        return r_err(reader, SERD_ERR_BAD_SYNTAX, "invalid graph name\n");
      }
      ctx.graph   = ctx.subject;
      ctx.subject = NULL;
      TRY(st, read_wrappedGraph(reader, &ctx));
      read_ws_star(reader);
    } else if ((st = read_triples(reader, ctx, &ate_dot))) {
      if (st == SERD_FAILURE && s_type == '[') {
        return SERD_SUCCESS;
      }

      if (ate_dot) {
        return r_err(
          reader, SERD_ERR_BAD_SYNTAX, "unexpected end of statement\n");
      }

      return st > SERD_FAILURE ? st : SERD_ERR_BAD_SYNTAX;
    } else if (!ate_dot) {
      read_ws_star(reader);
      st = (eat_byte_check(reader, '.') == '.') ? SERD_SUCCESS
                                                : SERD_ERR_BAD_SYNTAX;
    }
    break;
  }
  return st;
}

static void
skip_until(SerdReader* reader, uint8_t byte)
{
  for (int c = 0; (c = peek_byte(reader)) && c != byte;) {
    eat_byte_safe(reader, c);
  }
}

SerdStatus
read_turtleTrigDoc(SerdReader* reader)
{
  while (!reader->source.eof) {
    const size_t     orig_stack_size = reader->stack.size;
    const SerdStatus st              = read_n3_statement(reader);
    if (st > SERD_FAILURE) {
      if (reader->strict) {
        serd_stack_pop_to(&reader->stack, orig_stack_size);
        return st;
      }
      skip_until(reader, '\n');
    }
    serd_stack_pop_to(&reader->stack, orig_stack_size);
  }
  return SERD_SUCCESS;
}

SerdStatus
read_nquadsDoc(SerdReader* reader)
{
  SerdStatus st = SERD_SUCCESS;
  while (!reader->source.eof) {
    const size_t orig_stack_size = reader->stack.size;

    SerdStatementFlags flags   = 0;
    ReadContext        ctx     = {0, 0, 0, 0, 0, 0, &flags};
    bool               ate_dot = false;
    int                s_type  = 0;
    read_ws_star(reader);
    if (peek_byte(reader) == EOF) {
      break;
    }

    if (peek_byte(reader) == '@') {
      r_err(
        reader, SERD_ERR_BAD_SYNTAX, "syntax does not support directives\n");
      return SERD_ERR_BAD_SYNTAX;
    }

    // subject predicate object
    if ((st = read_subject(reader, ctx, &ctx.subject, &s_type)) ||
        !read_ws_star(reader) || (st = read_IRIREF(reader, &ctx.predicate)) ||
        !read_ws_star(reader) ||
        (st = read_object(reader, &ctx, false, &ate_dot))) {
      return st;
    }

    if (!ate_dot) { // graphLabel?
      read_ws_star(reader);
      switch (peek_byte(reader)) {
      case '.':
        break;
      case '_':
        TRY(st, read_BLANK_NODE_LABEL(reader, &ctx.graph, &ate_dot));
        break;
      default:
        TRY(st, read_IRIREF(reader, &ctx.graph));
      }

      // Terminating '.'
      read_ws_star(reader);
      if (!eat_byte_check(reader, '.')) {
        return SERD_ERR_BAD_SYNTAX;
      }
    }

    TRY(st, emit_statement(reader, ctx, ctx.object));

    serd_stack_pop_to(&reader->stack, orig_stack_size);
  }
  return SERD_SUCCESS;
}