/*
  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 "namespaces.h"
#include "node.h"
#include "reader.h"
#include "stack.h"
#include "string_utils.h"
#include "try.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>

#if defined(__clang__) && __clang_major__ >= 10
#  define SERD_FALLTHROUGH __attribute__((fallthrough))
_Pragma("clang diagnostic push")
_Pragma("clang diagnostic ignored \"-Wmissing-declarations\"")
#elif defined(__GNUC__) && __GNUC__ >= 7
#  define SERD_FALLTHROUGH __attribute__((fallthrough))
#else
#  define SERD_FALLTHROUGH
#endif

static bool
fancy_syntax(const SerdReader* const 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 uint8_t
read_HEX(SerdReader* const 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 SerdStatus
read_UCHAR(SerdReader* const reader,
           SerdNode* const   dest,
           uint32_t* const   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
    SERD_FALLTHROUGH;
  case 3:
    buf[2] = (uint8_t)(0x80u | (c & 0x3Fu));
    c >>= 6;
    c |= (32 << 6); // set bit 5
    SERD_FALLTHROUGH;
  case 2:
    buf[1] = (uint8_t)(0x80u | (c & 0x3Fu));
    c >>= 6;
    c |= 0xC0; // set bits 6 and 7
    SERD_FALLTHROUGH;
  case 1:
    buf[0] = (uint8_t)c;
    SERD_FALLTHROUGH;
  default:
    break;
  }

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

// Read ECHAR escape, initial \ is already eaten by caller
static SerdStatus
read_ECHAR(SerdReader* const reader, SerdNode* const dest)
{
  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':
    dest->flags |= SERD_HAS_NEWLINE;
    eat_byte_safe(reader, 'n');
    return push_byte(reader, dest, '\n');
  case 'r':
    dest->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 SerdStatus
bad_char(SerdReader* const reader, const char* const fmt, const 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* const reader,
                uint8_t           bytes[4],
                uint32_t* const   size,
                const 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* const reader,
                    SerdNode* const   dest,
                    const 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 (!tolerate_status(reader, st)) {
    return st;
  }

  if (st) {
    const SerdStatus rst = push_bytes(reader, dest, replacement_char, 3);
    return rst ? rst : st;
  }

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

static SerdStatus
read_utf8_code(SerdReader* const reader,
               SerdNode* const   dest,
               uint32_t* const   code,
               const 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) {
    const SerdStatus rst = push_bytes(reader, dest, replacement_char, 3);
    return rst ? rst : 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 SerdStatus
read_character(SerdReader* const reader, SerdNode* const dest, const uint8_t c)
{
  if (!(c & 0x80)) {
    switch (c) {
    case 0xA:
    case 0xD:
      dest->flags |= SERD_HAS_NEWLINE;
      break;
    case '"':
    case '\'':
      dest->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* const 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 bool
read_ws(SerdReader* const 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 bool
read_ws_star(SerdReader* const reader)
{
  while (read_ws(reader)) {
  }

  return true;
}

static bool
peek_delim(SerdReader* const reader, const uint8_t delim)
{
  read_ws_star(reader);
  return peek_byte(reader) == delim;
}

static bool
eat_delim(SerdReader* const reader, const uint8_t 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* const reader,
                         SerdNode* const   ref,
                         const uint8_t     q)
{
  SerdStatus st = SERD_SUCCESS;
  while (tolerate_status(reader, st)) {
    const int c = peek_byte(reader);
    if (c == '\\') {
      eat_byte_safe(reader, c);
      uint32_t code = 0;
      if ((st = read_ECHAR(reader, ref)) &&
          (st = read_UCHAR(reader, ref, &code))) {
        return r_err(reader, st, "invalid escape `\\%c'\n", peek_byte(reader));
      }
    } else if (c == EOF) {
      st = r_err(reader, SERD_ERR_NO_DATA, "unexpected end of file\n");
    } 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;
      }
      ref->flags |= SERD_HAS_QUOTE;
      if (!(st = push_byte(reader, ref, c))) {
        st = read_character(reader, ref, (uint8_t)q2);
      }
    } else {
      st = read_character(reader, ref, (uint8_t)eat_byte_safe(reader, c));
    }
  }

  return tolerate_status(reader, st) ? SERD_SUCCESS : st;
}

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

  while (tolerate_status(reader, st)) {
    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)) &&
          (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_safe(reader, q);
        return SERD_SUCCESS;
      } else {
        st = read_character(reader, ref, (uint8_t)eat_byte_safe(reader, c));
      }
    }
  }

  return tolerate_status(reader, st) ? SERD_SUCCESS : st;
}

static SerdStatus
read_String(SerdReader* const reader, SerdNode* const node)
{
  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, (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, (uint8_t)q1);
}

static 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* const reader, SerdNode* const dest)
{
  uint32_t   code = 0;
  const int  c    = peek_byte(reader);
  SerdStatus st   = SERD_SUCCESS;
  if (is_alpha(c)) {
    st = 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 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* const reader, SerdNode* const dest)
{
  uint32_t   code = 0;
  const int  c    = peek_byte(reader);
  SerdStatus st   = SERD_SUCCESS;
  if (is_alpha(c) || is_digit(c) || c == '_' || c == '-') {
    st = 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* const reader, SerdNode* const dest)
{
  SerdStatus st = push_byte(reader, dest, eat_byte_safe(reader, '%'));
  if (st) {
    return st;
  }

  const uint8_t h1 = read_HEX(reader);
  const uint8_t h2 = read_HEX(reader);
  if (!h1 || !h2) {
    return SERD_ERR_BAD_SYNTAX;
  }

  if (!(st = push_byte(reader, dest, h1))) {
    st = push_byte(reader, dest, h2);
  }

  return st;
}

static SerdStatus
read_PN_LOCAL_ESC(SerdReader* const reader, SerdNode* const 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 '~':
    return push_byte(reader, dest, eat_byte_safe(reader, c));
  default:
    break;
  }

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

static SerdStatus
read_PLX(SerdReader* const reader, SerdNode* const 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* const reader,
              SerdNode* const   dest,
              bool* const       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 '_':
    st = 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 == ':') {
      st = push_byte(reader, dest, eat_byte_safe(reader, c));
    } else if ((st = read_PLX(reader, dest)) > SERD_FAILURE) {
      return r_err(reader, st, "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->length;
    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* const reader, SerdNode* const dest)
{
  SerdStatus st = SERD_SUCCESS;
  int        c  = 0;
  while ((c = peek_byte(reader))) { // Middle: (PN_CHARS | '.')*
    if (c == '.') {
      st = push_byte(reader, dest, eat_byte_safe(reader, c));
    } else if ((st = read_PN_CHARS(reader, dest))) {
      break;
    }
  }

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

  return st;
}

static SerdStatus
read_PN_PREFIX(SerdReader* const reader, SerdNode* const dest)
{
  SerdStatus st = SERD_SUCCESS;

  if (!(st = read_PN_CHARS_BASE(reader, dest))) {
    return read_PN_PREFIX_tail(reader, dest);
  }

  return st;
}

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

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

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

static SerdStatus
read_IRIREF_scheme(SerdReader* const reader, SerdNode* const 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);
  }

  SerdStatus st = SERD_SUCCESS;
  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);
    }

    if ((st = push_byte(reader, dest, eat_byte_safe(reader, c)))) {
      return st;
    }

    if (c == ':') {
      return SERD_SUCCESS; // End of scheme
    }
  }

  return SERD_FAILURE;
}

static SerdStatus
read_IRIREF(SerdReader* const reader, SerdNode** const dest)
{
  SerdStatus st = SERD_SUCCESS;
  if ((st = eat_byte_check(reader, '<'))) {
    return st;
  }

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

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

  uint32_t code = 0;
  while (st <= SERD_FAILURE) {
    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) {
        st = r_err(reader,
                   SERD_ERR_BAD_SYNTAX,
                   "invalid IRI character (escape %%%02X)\n",
                   (unsigned)c);
        if (reader->strict) {
          break;
        }

        if (!(st = push_byte(reader, *dest, c))) {
          st = SERD_FAILURE;
        }
      } else if (!(c & 0x80)) {
        st = push_byte(reader, *dest, c);
      } else {
        st = read_utf8_character(reader, *dest, (uint8_t)c);
      }
    }
  }

  return tolerate_status(reader, st) ? SERD_SUCCESS : st;
}

static SerdStatus
read_PrefixedName(SerdReader* const reader,
                  SerdNode* const   dest,
                  const bool        read_prefix,
                  bool* const       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;
  }

  if ((st = push_byte(reader, dest, eat_byte_safe(reader, ':'))) ||
      (st = read_PN_LOCAL(reader, dest, ate_dot)) > SERD_FAILURE) {
    return st;
  }

  return SERD_SUCCESS;
}

static SerdStatus
read_0_9(SerdReader* const reader, SerdNode* const str, const 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 st;
}

static SerdStatus
read_number(SerdReader* const reader,
            SerdNode** const  dest,
            bool* const       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 == '+') {
    TRY(st, 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')
    TRY(st, 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
      }

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

  return SERD_SUCCESS;
}

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

static SerdStatus
read_literal(SerdReader* const reader,
             SerdNode** const  dest,
             bool* const       ate_dot)
{
  if (!(*dest = push_node(reader, SERD_LITERAL, "", 0))) {
    return SERD_ERR_OVERFLOW;
  }

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

  SerdNode* datatype = NULL;
  switch (peek_byte(reader)) {
  case '@':
    eat_byte_safe(reader, '@');
    (*dest)->flags |= SERD_HAS_LANGUAGE;
    TRY(st, read_LANGTAG(reader));
    break;
  case '^':
    eat_byte_safe(reader, '^');
    TRY(st, eat_byte_check(reader, '^'));
    (*dest)->flags |= SERD_HAS_DATATYPE;
    TRY(st, read_iri(reader, &datatype, ate_dot));
    break;
  }
  return SERD_SUCCESS;
}

static SerdStatus
read_VARNAME(SerdReader* const reader, SerdNode** const dest)
{
  // Simplified from SPARQL: VARNAME ::= (PN_CHARS_U | [0-9])+
  SerdNode*  n  = *dest;
  SerdStatus st = SERD_SUCCESS;
  int        c  = 0;
  peek_byte(reader);
  while ((c = peek_byte(reader))) {
    if (is_digit(c) || c == '_') {
      st = push_byte(reader, n, eat_byte_safe(reader, c));
    } else if ((st = read_PN_CHARS(reader, n))) {
      st = st > SERD_FAILURE ? st : SERD_SUCCESS;
      break;
    }
  }

  return st;
}

static SerdStatus
read_Var(SerdReader* const reader, SerdNode** const dest)
{
  if (!(reader->flags & SERD_READ_VARIABLES)) {
    return r_err(
      reader, SERD_ERR_BAD_SYNTAX, "syntax does not support variables\n");
  }

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

  assert(peek_byte(reader) == '$' || peek_byte(reader) == '?');
  serd_byte_source_advance(reader->source);

  return read_VARNAME(reader, dest);
}

static SerdStatus
read_verb(SerdReader* reader, SerdNode** dest)
{
  const size_t orig_stack_size = reader->stack.size;

  switch (peek_byte(reader)) {
  case '$':
  case '?':
    return read_Var(reader, dest);
  case '<':
    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);
  if (st > SERD_FAILURE) {
    return st;
  }

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

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

  return SERD_SUCCESS;
}

static SerdStatus
read_BLANK_NODE_LABEL(SerdReader* const reader,
                      SerdNode** const  dest,
                      bool* const       ate_dot)
{
  SerdStatus st = SERD_SUCCESS;

  eat_byte_safe(reader, '_');
  TRY(st, eat_byte_check(reader, ':'));

  if (!(*dest = push_node(reader,
                          SERD_BLANK,
                          reader->bprefix ? reader->bprefix : "",
                          reader->bprefix_len))) {
    return SERD_ERR_OVERFLOW;
  }

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

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

  if (st > SERD_FAILURE) {
    return st;
  }

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

  if (fancy_syntax(reader) && !(reader->flags & SERD_READ_EXACT_BLANKS)) {
    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 tolerate_status(reader, st) ? SERD_SUCCESS : st;
}

static SerdStatus
read_anon(SerdReader* const reader,
          ReadContext       ctx,
          const bool        subject,
          SerdNode** const  dest)
{
  eat_byte_safe(reader, '[');

  const SerdStatementFlags old_flags = *ctx.flags;
  const bool               empty     = peek_delim(reader, ']');

  if (subject) {
    *ctx.flags |= empty ? SERD_EMPTY_S : SERD_ANON_S;
  } else {
    *ctx.flags |= SERD_ANON_O;
  }

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

  // Emit statement with this anonymous object first
  SerdStatus st = SERD_SUCCESS;
  if (ctx.subject) {
    TRY(st, emit_statement(reader, ctx, *dest));
  }

  // Switch the subject to the anonymous node and read its description
  ctx.subject = *dest;
  if (!empty) {
    bool ate_dot_in_list = false;
    TRY(st, 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);
    *ctx.flags = old_flags;
  }

  if (!(subject && empty)) {
    TRY(st, serd_sink_write_end(reader->sink, *dest));
  }

  return eat_byte_check(reader, ']');
}

/* 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* const  reader,
            ReadContext* const ctx,
            const bool         emit,
            bool* const        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;
  const int  c      = peek_byte(reader);
  if (!fancy_syntax(reader)) {
    switch (c) {
    case '"':
    case ':':
    case '<':
    case '_':
      break;
    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 '$':
  case '?':
    ret = read_Var(reader, &o);
    break;
  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 '<':
    ret = read_IRIREF(reader, &o);
    break;
  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, ate_dot);
    break;
  case '\"':
  case '\'':
    ret = read_literal(reader, &o, 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 (!(ret = read_PN_CHARS_BASE(reader, o))) {
    }

    if (ret > SERD_FAILURE) {
      return ret;
    }

    if ((o->length == 4 && !memcmp(serd_node_string(o), "true", 4)) ||
        (o->length == 5 && !memcmp(serd_node_string(o), "false", 5))) {
      o->flags |= SERD_HAS_DATATYPE;
      o->type = SERD_LITERAL;
      if (!(push_node(reader, SERD_URI, XSD_BOOLEAN, XSD_BOOLEAN_LEN))) {
        ret = SERD_ERR_OVERFLOW;
      } else {
        ret = SERD_SUCCESS;
      }
    } else if ((ret = read_PN_PREFIX_tail(reader, o)) > SERD_FAILURE ||
               (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 && emit && simple && o) {
    ret = emit_statement(reader, *ctx, o);
  } else if (!ret && !emit) {
    ctx->object = o;
    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* const reader, ReadContext ctx, bool* const 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 (st <= SERD_FAILURE && !*ate_dot && eat_delim(reader, ',')) {
    st = read_object(reader, &ctx, true, ate_dot);
  }

  return st;
}

static SerdStatus
read_predicateObjectList(SerdReader* const reader,
                         ReadContext       ctx,
                         bool* const       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* const reader, const SerdStatus st)
{
  return st ? st : eat_byte_check(reader, ')');
}

static SerdStatus
read_collection(SerdReader* const reader,
                ReadContext       ctx,
                SerdNode** const  dest)
{
  SerdStatus st = SERD_SUCCESS;
  eat_byte_safe(reader, '(');
  bool end = peek_delim(reader, ')');
  *dest    = end ? reader->rdf_nil : blank_id(reader);

  if (!*dest) {
    return SERD_ERR_OVERFLOW;
  }

  if (ctx.subject) {
    // subject predicate _:head
    *ctx.flags |= (end ? 0 : SERD_LIST_O);
    TRY(st, emit_statement(reader, ctx, *dest));
  } else {
    *ctx.flags |= (end ? 0 : SERD_LIST_S);
  }

  if (end) {
    return end_collection(reader, 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_length(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, 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
        assert(rest);            // Can't overflow since read_object() popped
      } else {
        set_blank_id(reader, rest, genid_length(reader) + 1);
      }
    }

    // _:node rdf:rest _:rest
    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, st);
}

static SerdStatus
read_subject(SerdReader* const reader,
             ReadContext       ctx,
             SerdNode** const  dest,
             int* const        s_type)
{
  SerdStatus st      = SERD_SUCCESS;
  bool       ate_dot = false;
  switch ((*s_type = peek_byte(reader))) {
  case '$':
  case '?':
    st = read_Var(reader, dest);
    break;
  case '[':
    st = 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* const reader, SerdNode** const dest)
{
  SerdStatus st      = SERD_SUCCESS;
  bool       ate_dot = false;

  switch (peek_byte(reader)) {
  case '[':
    eat_byte_safe(reader, '[');
    read_ws_star(reader);
    if ((st = eat_byte_check(reader, ']'))) {
      return st;
    }
    *dest = blank_id(reader);
    return *dest ? SERD_SUCCESS : SERD_ERR_OVERFLOW;
  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* const reader, ReadContext ctx, bool* const 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* const reader, const bool sparql, const 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));

  if (reader->stack.size + sizeof(SerdNode) > reader->stack.buf_size) {
    return SERD_ERR_OVERFLOW;
  }

  serd_node_zero_pad(uri);
  TRY(st, serd_sink_write_base(reader->sink, uri));

  read_ws_star(reader);
  if (!sparql) {
    return eat_byte_check(reader, '.');
  }

  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* const reader, const bool sparql, const 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 ((st = eat_byte_check(reader, ':'))) {
    return st;
  }

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

  if (reader->stack.size + sizeof(SerdNode) > reader->stack.buf_size) {
    return SERD_ERR_OVERFLOW;
  }

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

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

static SerdStatus
read_directive(SerdReader* const 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* const reader, ReadContext* const ctx)
{
  SerdStatus st = SERD_SUCCESS;
  if ((st = eat_byte_check(reader, '{'))) {
    return st;
  }

  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;
    if ((st = read_subject(reader, *ctx, &ctx->subject, &s_type))) {
      return r_err(reader, st, "expected 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* const node, const char* const tok, const size_t n)
{
  return ((!node || node->length != n)
            ? -1
            : serd_strncasecmp(serd_node_string(node), tok, n));
}

SerdStatus
read_n3_statement(SerdReader* const reader)
{
  SerdStatementFlags flags   = 0;
  ReadContext        ctx     = {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 && (reader->strict || (s_type != '('))) {
        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, '.');
    }
    break;
  }
  return st;
}

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

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

    SerdStatementFlags flags   = 0;
    ReadContext        ctx     = {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;
    }

    if ((st = read_subject(reader, ctx, &ctx.subject, &s_type)) ||
        !read_ws_star(reader)) {
      return st;
    }

    switch (peek_byte(reader)) {
    case '$':
    case '?':
      st = read_Var(reader, &ctx.predicate);
      break;
    case '<':
      st = read_IRIREF(reader, &ctx.predicate);
      break;
    }

    if (st || !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_Var(reader, &ctx.graph));
        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);
      TRY(st, eat_byte_check(reader, '.'));
    }

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

#if defined(__clang__) && __clang_major__ >= 10
_Pragma("clang diagnostic pop")
#endif