/* Parser combinators for binary formats.
 * Copyright (C) 2012  Meredith L. Patterson, Dan "TQ" Hirsch
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include "hammer.h"
#include "internal.h"
#include "allocator.h"
#include <assert.h>
#include <ctype.h>
#include <error.h>
#include <limits.h>
#include <stdarg.h>
#include <string.h>

#define a_new_(arena, typ, count) ((typ*)h_arena_malloc((arena), sizeof(typ)*(count)))
#define a_new(typ, count) a_new_(state->arena, typ, count)
// we can create a_new0 if necessary. It would allocate some memory and immediately zero it out.

static guint djbhash(const uint8_t *buf, size_t len) {
  guint hash = 5381;
  while (len--) {
    hash = hash * 33 + *buf++;
  }
  return hash;
}

HParserCacheValue* recall(HParserCacheKey *k, HParseState *state) {
  HParserCacheValue *cached = g_hash_table_lookup(state->cache, k);
  HRecursionHead *head = g_hash_table_lookup(state->recursion_heads, k);
  if (!head) { // No heads found
    return cached;
  } else { // Some heads found
    if (!cached && head->head_parser != k->parser && !g_slist_find(head->involved_set, k->parser)) {
      // Nothing in the cache, and the key parser is not involved
      HParseResult *tmp = g_new(HParseResult, 1);
      tmp->ast = NULL; tmp->arena = state->arena;
      HParserCacheValue *ret = g_new(HParserCacheValue, 1);
      ret->value_type = PC_RIGHT; ret->right = tmp;
      return ret;
    }
    if (g_slist_find(head->eval_set, k->parser)) {
      // Something is in the cache, and the key parser is in the eval set. Remove the key parser from the eval set of the head. 
      head->eval_set = g_slist_remove_all(head->eval_set, k->parser);
      HParseResult *tmp_res = k->parser->fn(k->parser->env, state);
      if (tmp_res)
	tmp_res->arena = state->arena;
      // we know that cached has an entry here, modify it
      cached->value_type = PC_RIGHT;
      cached->right = tmp_res;
    }
    return cached;
  }
}

/* Setting up the left recursion. We have the LR for the rule head;
 * we modify the involved_sets of all LRs in the stack, until we 
 * see the current parser again.
 */

void setupLR(const HParser *p, GQueue *stack, HLeftRec *rec_detect) {
  if (!rec_detect->head) {
    HRecursionHead *some = g_new(HRecursionHead, 1);
    some->head_parser = p; some->involved_set = NULL; some->eval_set = NULL;
    rec_detect->head = some;
  }
  size_t i = 0;
  HLeftRec *lr = g_queue_peek_nth(stack, i);
  while (lr && lr->rule != p) {
    lr->head = rec_detect->head;
    lr->head->involved_set = g_slist_prepend(lr->head->involved_set, (gpointer)lr->rule);
  }
}

/* If recall() returns NULL, we need to store a dummy failure in the cache and compute the
 * future parse. 
 */

HParseResult* grow(HParserCacheKey *k, HParseState *state, HRecursionHead *head) {
  // Store the head into the recursion_heads
  g_hash_table_replace(state->recursion_heads, k, head);
  HParserCacheValue *old_cached = g_hash_table_lookup(state->cache, k);
  if (!old_cached || PC_LEFT == old_cached->value_type)
    errx(1, "impossible match");
  HParseResult *old_res = old_cached->right;
  
  // reset the eval_set of the head of the recursion at each beginning of growth
  head->eval_set = head->involved_set;
  HParseResult *tmp_res;
  if (k->parser) {
    tmp_res = k->parser->fn(k->parser->env, state);
    if (tmp_res)
      tmp_res->arena = state->arena;
  } else
    tmp_res = NULL;
  if (tmp_res) {
    if ((old_res->ast->index < tmp_res->ast->index) || 
	(old_res->ast->index == tmp_res->ast->index && old_res->ast->bit_offset < tmp_res->ast->bit_offset)) {
      HParserCacheValue *v = g_new(HParserCacheValue, 1);
      v->value_type = PC_RIGHT; v->right = tmp_res;
      g_hash_table_replace(state->cache, k, v);
      return grow(k, state, head);
    } else {
      // we're done with growing, we can remove data from the recursion head
      g_hash_table_remove(state->recursion_heads, k);
      HParserCacheValue *cached = g_hash_table_lookup(state->cache, k);
      if (cached && PC_RIGHT == cached->value_type) {
	return cached->right;
      } else {
	errx(1, "impossible match");
      }
    }
  } else {
    g_hash_table_remove(state->recursion_heads, k);
    return old_res;
  }
}

HParseResult* lr_answer(HParserCacheKey *k, HParseState *state, HLeftRec *growable) {
  if (growable->head) {
    if (growable->head->head_parser != k->parser) {
      // not the head rule, so not growing
      return growable->seed;
    }
    else {
      // update cache
      HParserCacheValue *v = g_new(HParserCacheValue, 1);
      v->value_type = PC_RIGHT; v->right = growable->seed;
      g_hash_table_replace(state->cache, k, v);
      if (!growable->seed)
	return NULL;
      else
	return grow(k, state, growable->head);
    }
  } else {
    errx(1, "lrAnswer with no head");
  }
}

/* Warth's recursion. Hi Alessandro! */
HParseResult* h_do_parse(const HParser* parser, HParseState *state) {
  HParserCacheKey *key = a_new(HParserCacheKey, 1);
  key->input_pos = state->input_stream; key->parser = parser;
  HParserCacheValue *m = recall(key, state);
  // check to see if there is already a result for this object...
  if (!m) {
    // It doesn't exist, so create a dummy result to cache
    HLeftRec *base = a_new(HLeftRec, 1);
    base->seed = NULL; base->rule = parser; base->head = NULL;
    g_queue_push_head(state->lr_stack, base);
    // cache it
    HParserCacheValue *dummy = a_new(HParserCacheValue, 1);
    dummy->value_type = PC_LEFT; dummy->left = base;
    g_hash_table_replace(state->cache, key, dummy);
    // parse the input
    HParseResult *tmp_res;
    if (parser) {
      HInputStream bak = state->input_stream;
      tmp_res = parser->fn(parser->env, state);
      if (tmp_res) {
	tmp_res->arena = state->arena;
	if (!state->input_stream.overrun) {
	  tmp_res->bit_length = ((state->input_stream.index - bak.index) << 3);
	  if (state->input_stream.endianness & BIT_BIG_ENDIAN)
	    tmp_res->bit_length += state->input_stream.bit_offset - bak.bit_offset;
	  else
	    tmp_res->bit_length += bak.bit_offset - state->input_stream.bit_offset;
	} else
	  tmp_res->bit_length = 0;
      }
    } else
      tmp_res = NULL;
    if (state->input_stream.overrun)
      return NULL; // overrun is always failure.
#ifdef CONSISTENCY_CHECK
    if (!tmp_res) {
      state->input_stream = INVALID;
      state->input_stream.input = key->input_pos.input;
    }
#endif
    // the base variable has passed equality tests with the cache
    g_queue_pop_head(state->lr_stack);
    // setupLR, used below, mutates the LR to have a head if appropriate, so we check to see if we have one
    if (NULL == base->head) {
      HParserCacheValue *right = a_new(HParserCacheValue, 1);
      right->value_type = PC_RIGHT; right->right = tmp_res;
      g_hash_table_replace(state->cache, key, right);
      return tmp_res;
    } else {
      base->seed = tmp_res;
      HParseResult *res = lr_answer(key, state, base);
      return res;
    }
  } else {
    // it exists!
    if (PC_LEFT == m->value_type) {
      setupLR(parser, state->lr_stack, m->left);
      return m->left->seed; // BUG: this might not be correct
    } else {
      return m->right;
    }
  }
}

/* Helper function, since these lines appear in every parser */
static HParseResult* make_result(HParseState *state, HParsedToken *tok) {
  HParseResult *ret = a_new(HParseResult, 1);
  ret->ast = tok;
  ret->arena = state->arena;
  return ret;
}

typedef struct {
  uint8_t *str;
  uint8_t len;
} HToken;

 static HParseResult* parse_unimplemented(void* env, HParseState *state) {
  (void) env;
  (void) state;
  static HParsedToken token = {
    .token_type = TT_ERR
  };
  static HParseResult result = {
    .ast = &token
  };
  return &result;
}

static HParser unimplemented __attribute__((unused)) = {
  .fn = parse_unimplemented,
  .env = NULL
};

struct bits_env {
  uint8_t length;
  uint8_t signedp;
};

static HParseResult* parse_bits(void* env, HParseState *state) {
  struct bits_env *env_ = env;
  HParsedToken *result = a_new(HParsedToken, 1);
  result->token_type = (env_->signedp ? TT_SINT : TT_UINT);
  if (env_->signedp)
    result->sint = h_read_bits(&state->input_stream, env_->length, true);
  else
    result->uint = h_read_bits(&state->input_stream, env_->length, false);
  return make_result(state, result);
}

const HParser* h_bits(size_t len, bool sign) {
  struct bits_env *env = g_new(struct bits_env, 1);
  env->length = len;
  env->signedp = sign;
  HParser *res = g_new(HParser, 1);
  res->fn = parse_bits;
  res->env = env;
  return res;
}

#define SIZED_BITS(name_pre, len, signedp) \
  const HParser* h_##name_pre##len () {	       \
    return h_bits(len, signedp);	       \
  }
SIZED_BITS(int, 8, true)
SIZED_BITS(int, 16, true)
SIZED_BITS(int, 32, true)
SIZED_BITS(int, 64, true)
SIZED_BITS(uint, 8, false)
SIZED_BITS(uint, 16, false)
SIZED_BITS(uint, 32, false)
SIZED_BITS(uint, 64, false)

static HParseResult* parse_token(void *env, HParseState *state) {
  HToken *t = (HToken*)env;
  for (int i=0; i<t->len; ++i) {
    uint8_t chr = (uint8_t)h_read_bits(&state->input_stream, 8, false);
    if (t->str[i] != chr) {
      return NULL;
    }
  }
  HParsedToken *tok = a_new(HParsedToken, 1);
  tok->token_type = TT_BYTES; tok->bytes.token = t->str; tok->bytes.len = t->len;
  return make_result(state, tok);
}

const HParser* h_token(const uint8_t *str, const size_t len) { 
  HToken *t = g_new(HToken, 1);
  t->str = (uint8_t*)str, t->len = len;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_token; ret->env = t;
  return (const HParser*)ret;
}

static HParseResult* parse_ch(void* env, HParseState *state) {
  uint8_t c = (uint8_t)GPOINTER_TO_UINT(env);
  uint8_t r = (uint8_t)h_read_bits(&state->input_stream, 8, false);
  if (c == r) {
    HParsedToken *tok = a_new(HParsedToken, 1);    
    tok->token_type = TT_UINT; tok->uint = r;
    return make_result(state, tok);
  } else {
    return NULL;
  }
}

const HParser* h_ch(const uint8_t c) {  
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_ch; ret->env = GUINT_TO_POINTER(c);
  return (const HParser*)ret;
}

static HParseResult* parse_whitespace(void* env, HParseState *state) {
  char c;
  HInputStream bak;
  do {
    bak = state->input_stream;
    c = h_read_bits(&state->input_stream, 8, false);
    if (state->input_stream.overrun)
      return NULL;
  } while (isspace(c));
  state->input_stream = bak;
  return h_do_parse((HParser*)env, state);
}

const HParser* h_whitespace(const HParser* p) {
  HParser *ret = g_new(HParser, 1);
  ret->fn  = parse_whitespace;
  ret->env = (void*)p;
  return ret;
}

typedef struct {
  const HParser *p;
  HAction action;
} HParseAction;

static HParseResult* parse_action(void *env, HParseState *state) {
  HParseAction *a = (HParseAction*)env;
  if (a->p && a->action) {
    HParseResult *tmp = h_do_parse(a->p, state);
    //HParsedToken *tok = a->action(h_do_parse(a->p, state));
    const HParsedToken *tok = a->action(tmp);
    return make_result(state, (HParsedToken*)tok);
  } else // either the parser's missing or the action's missing
    return NULL;
}

const HParser* h_action(const HParser* p, const HAction a) { 
  HParser *res = g_new(HParser, 1);
  res->fn = parse_action;
  HParseAction *env = g_new(HParseAction, 1);
  env->p = p;
  env->action = a;
  res->env = (void*)env;
  return res;
}

static HParseResult* parse_charset(void *env, HParseState *state) {
  uint8_t in = h_read_bits(&state->input_stream, 8, false);
  HCharset cs = (HCharset)env;

  if (charset_isset(cs, in)) {
    HParsedToken *tok = a_new(HParsedToken, 1);
    tok->token_type = TT_UINT; tok->uint = in;
    return make_result(state, tok);    
  } else
    return NULL;
}

const HParser* h_ch_range(const uint8_t lower, const uint8_t upper) {
  HParser *ret = g_new(HParser, 1);
  HCharset cs = new_charset();
  for (int i = 0; i < 256; i++)
    charset_set(cs, i, (lower <= i) && (i <= upper));
  ret->fn = parse_charset; ret->env = (void*)cs;
  return (const HParser*)ret;
}

typedef struct {
  const HParser *p;
  int64_t lower;
  int64_t upper;
} HRange;

static HParseResult* parse_int_range(void *env, HParseState *state) {
  HRange *r_env = (HRange*)env;
  HParseResult *ret = h_do_parse(r_env->p, state);
  if (!ret || !ret->ast)
    return NULL;
  switch(ret->ast->token_type) {
  case TT_SINT:
    if (r_env->lower <= ret->ast->sint && r_env->upper >= ret->ast->sint)
      return ret;
    else
      return NULL;
  case TT_UINT:
    if ((uint64_t)r_env->lower <= ret->ast->uint && (uint64_t)r_env->upper >= ret->ast->uint)
      return ret;
    else
      return NULL;
  default:
    return NULL;
  }
}

const HParser* h_int_range(const HParser *p, const int64_t lower, const int64_t upper) {
  struct bits_env *b_env = p->env;
  // p must be an integer parser, which means it's using parse_bits
  assert_message(p->fn == parse_bits, "int_range requires an integer parser"); 
  // if it's a uint parser, it can't be uint64
  assert_message(!(b_env->signedp) ? (b_env->length < 64) : true, "int_range can't use a uint64 parser");
  // and regardless, the bounds need to fit in the parser in question
  switch(b_env->length) {
  case 32:
    if (b_env->signedp)
      assert_message(lower >= INT_MIN && upper <= INT_MAX, "bounds for 32-bit signed integer exceeded");
    else
      assert_message(lower >= 0 && upper <= UINT_MAX, "bounds for 32-bit unsigned integer exceeded");
    break;
  case 16:
    if (b_env->signedp)
      assert_message(lower >= SHRT_MIN && upper <= SHRT_MAX, "bounds for 16-bit signed integer exceeded");
    else
      assert_message(lower >= 0 && upper <= USHRT_MAX, "bounds for 16-bit unsigned integer exceeded");
    break;
  case 8:
    if (b_env->signedp)
      assert_message(lower >= SCHAR_MIN && upper <= SCHAR_MAX, "bounds for 8-bit signed integer exceeded");
    else
      assert_message(lower >= 0 && upper <= UCHAR_MAX, "bounds for 8-bit unsigned integer exceeded");
    break;
  default:
    // how'd that happen? if we got here, this parser is broken.
    return NULL;
  }

  HRange *r_env = g_new(HRange, 1);
  r_env->p = p;
  r_env->lower = lower;
  r_env->upper = upper;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_int_range;
  ret->env = (void*)r_env;
  return ret;
}

const HParser* h_not_in(const uint8_t *options, int count) {
  HParser *ret = g_new(HParser, 1);
  HCharset cs = new_charset();
  for (int i = 0; i < 256; i++)
    charset_set(cs, i, 1);
  for (int i = 0; i < count; i++)
    charset_set(cs, options[i], 0);

  ret->fn = parse_charset; ret->env = (void*)cs;
  return (const HParser*)ret;
}

static HParseResult* parse_end(void *env, HParseState *state) {
  if (state->input_stream.index == state->input_stream.length) {
    HParseResult *ret = a_new(HParseResult, 1);
    ret->ast = NULL;
    return ret;
  } else {
    return NULL;
  }
}

const HParser* h_end_p() { 
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_end; ret->env = NULL;
  return (const HParser*)ret;
}

static HParseResult* parse_nothing() {
  // not a mistake, this parser always fails
  return NULL;
}

const HParser* h_nothing_p() { 
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_nothing; ret->env = NULL;
  return (const HParser*)ret;
}

typedef struct {
  size_t len;
  const HParser **p_array;
} HSequence;

static HParseResult* parse_sequence(void *env, HParseState *state) {
  HSequence *s = (HSequence*)env;
  HCountedArray *seq = h_carray_new_sized(state->arena, (s->len > 0) ? s->len : 4);
  for (size_t i=0; i<s->len; ++i) {
    HParseResult *tmp = h_do_parse(s->p_array[i], state);
    // if the interim parse fails, the whole thing fails
    if (NULL == tmp) {
      return NULL;
    } else {
      if (tmp->ast)
	h_carray_append(seq, (void*)tmp->ast);
    }
  }
  HParsedToken *tok = a_new(HParsedToken, 1);
  tok->token_type = TT_SEQUENCE; tok->seq = seq;
  return make_result(state, tok);
}

const HParser* h_sequence(const HParser *p, ...) {
  va_list ap;
  size_t len = 0;
  const HParser *arg;
  va_start(ap, p);
  do {
    len++;
    arg = va_arg(ap, const HParser *);
  } while (arg);
  va_end(ap);
  HSequence *s = g_new(HSequence, 1);
  s->p_array = g_new(const HParser *, len);

  va_start(ap, p);
  s->p_array[0] = p;
  for (size_t i = 1; i < len; i++) {
    s->p_array[i] = va_arg(ap, const HParser *);
  } while (arg);
  va_end(ap);

  s->len = len;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_sequence; ret->env = (void*)s;
  return ret;
}

static HParseResult* parse_choice(void *env, HParseState *state) {
  HSequence *s = (HSequence*)env;
  HInputStream backup = state->input_stream;
  for (size_t i=0; i<s->len; ++i) {
    if (i != 0)
      state->input_stream = backup;
    HParseResult *tmp = h_do_parse(s->p_array[i], state);
    if (NULL != tmp)
      return tmp;
  }
  // nothing succeeded, so fail
  return NULL;
}

const HParser* h_choice(const HParser* p, ...) {
  va_list ap;
  size_t len = 0;
  HSequence *s = g_new(HSequence, 1);

  const HParser *arg;
  va_start(ap, p);
  do {
    len++;
    arg = va_arg(ap, const HParser *);
  } while (arg);
  va_end(ap);
  s->p_array = g_new(const HParser *, len);

  va_start(ap, p);
  s->p_array[0] = p;
  for (size_t i = 1; i < len; i++) {
    s->p_array[i] = va_arg(ap, const HParser *);
  } while (arg);
  va_end(ap);

  s->len = len;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_choice; ret->env = (void*)s;
  return ret;
}

typedef struct {
  const HParser *p1;
  const HParser *p2;
} HTwoParsers;

// return token size in bits...
size_t token_length(HParseResult *pr) {
  if (pr) {
    return pr->bit_length;
  } else {
    return 0;
  }
}

static HParseResult* parse_butnot(void *env, HParseState *state) {
  HTwoParsers *parsers = (HTwoParsers*)env;
  // cache the initial state of the input stream
  HInputStream start_state = state->input_stream;
  HParseResult *r1 = h_do_parse(parsers->p1, state);
  // if p1 failed, bail out early
  if (NULL == r1) {
    return NULL;
  } 
  // cache the state after parse #1, since we might have to back up to it
  HInputStream after_p1_state = state->input_stream;
  state->input_stream = start_state;
  HParseResult *r2 = h_do_parse(parsers->p2, state);
  // TODO(mlp): I'm pretty sure the input stream state should be the post-p1 state in all cases
  state->input_stream = after_p1_state;
  // if p2 failed, restore post-p1 state and bail out early
  if (NULL == r2) {
    return r1;
  }
  size_t r1len = token_length(r1);
  size_t r2len = token_length(r2);
  // if both match but p1's text is shorter than than p2's (or the same length), fail
  if (r1len <= r2len) {
    return NULL;
  } else {
    return r1;
  }
}

const HParser* h_butnot(const HParser* p1, const HParser* p2) { 
  HTwoParsers *env = g_new(HTwoParsers, 1);
  env->p1 = p1; env->p2 = p2;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_butnot; ret->env = (void*)env;
  return ret;
}

static HParseResult* parse_difference(void *env, HParseState *state) {
  HTwoParsers *parsers = (HTwoParsers*)env;
  // cache the initial state of the input stream
  HInputStream start_state = state->input_stream;
  HParseResult *r1 = h_do_parse(parsers->p1, state);
  // if p1 failed, bail out early
  if (NULL == r1) {
    return NULL;
  } 
  // cache the state after parse #1, since we might have to back up to it
  HInputStream after_p1_state = state->input_stream;
  state->input_stream = start_state;
  HParseResult *r2 = h_do_parse(parsers->p2, state);
  // TODO(mlp): I'm pretty sure the input stream state should be the post-p1 state in all cases
  state->input_stream = after_p1_state;
  // if p2 failed, restore post-p1 state and bail out early
  if (NULL == r2) {
    return r1;
  }
  size_t r1len = token_length(r1);
  size_t r2len = token_length(r2);
  // if both match but p1's text is shorter than p2's, fail
  if (r1len < r2len) {
    return NULL;
  } else {
    return r1;
  }
}

const HParser* h_difference(const HParser* p1, const HParser* p2) { 
  HTwoParsers *env = g_new(HTwoParsers, 1);
  env->p1 = p1; env->p2 = p2;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_difference; ret->env = (void*)env;
  return ret;
}

static HParseResult* parse_xor(void *env, HParseState *state) {
  HTwoParsers *parsers = (HTwoParsers*)env;
  // cache the initial state of the input stream
  HInputStream start_state = state->input_stream;
  HParseResult *r1 = h_do_parse(parsers->p1, state);
  HInputStream after_p1_state = state->input_stream;
  // reset input stream, parse again
  state->input_stream = start_state;
  HParseResult *r2 = h_do_parse(parsers->p2, state);
  if (NULL == r1) {
    if (NULL != r2) {
      return r2;
    } else {
      return NULL;
    }
  } else {
    if (NULL == r2) {
      state->input_stream = after_p1_state;
      return r1;
    } else {
      return NULL;
    }
  }
}

const HParser* h_xor(const HParser* p1, const HParser* p2) { 
  HTwoParsers *env = g_new(HTwoParsers, 1);
  env->p1 = p1; env->p2 = p2;
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_xor; ret->env = (void*)env;
  return ret;
}

typedef struct {
  const HParser *p, *sep;
  size_t count;
  bool min_p;
} HRepeat;

static HParseResult *parse_many(void* env, HParseState *state) {
  HRepeat *env_ = (HRepeat*) env;
  HCountedArray *seq = h_carray_new_sized(state->arena, (env_->count > 0 ? env_->count : 4));
  size_t count = 0;
  HInputStream bak;
  while (env_->min_p || env_->count > count) {
    bak = state->input_stream;
    if (count > 0) {
      HParseResult *sep = h_do_parse(env_->sep, state);
      if (!sep)
	goto err0;
    }
    HParseResult *elem = h_do_parse(env_->p, state);
    if (!elem)
      goto err0;
    if (elem->ast)
      h_carray_append(seq, (void*)elem->ast);
    count++;
  }
  if (count < env_->count)
    goto err;
 succ:
  ; // necessary for the label to be here...
  HParsedToken *res = a_new(HParsedToken, 1);
  res->token_type = TT_SEQUENCE;
  res->seq = seq;
  return make_result(state, res);
 err0:
  if (count >= env_->count) {
    state->input_stream = bak;
    goto succ;
  }
 err:
  state->input_stream = bak;
  return NULL;
}

const HParser* h_many(const HParser* p) {
  HParser *res = g_new(HParser, 1);
  HRepeat *env = g_new(HRepeat, 1);
  env->p = p;
  env->sep = h_epsilon_p();
  env->count = 0;
  env->min_p = true;
  res->fn = parse_many;
  res->env = env;
  return res;
}

const HParser* h_many1(const HParser* p) {
  HParser *res = g_new(HParser, 1);
  HRepeat *env = g_new(HRepeat, 1);
  env->p = p;
  env->sep = h_epsilon_p();
  env->count = 1;
  env->min_p = true;
  res->fn = parse_many;
  res->env = env;
  return res;
}

const HParser* h_repeat_n(const HParser* p, const size_t n) {
  HParser *res = g_new(HParser, 1);
  HRepeat *env = g_new(HRepeat, 1);
  env->p = p;
  env->sep = h_epsilon_p();
  env->count = n;
  env->min_p = false;
  res->fn = parse_many;
  res->env = env;
  return res;
}

static HParseResult* parse_ignore(void* env, HParseState* state) {
  HParseResult *res0 = h_do_parse((HParser*)env, state);
  if (!res0)
    return NULL;
  HParseResult *res = a_new(HParseResult, 1);
  res->ast = NULL;
  res->arena = state->arena;
  return res;
}
const HParser* h_ignore(const HParser* p) {
  HParser* ret = g_new(HParser, 1);
  ret->fn = parse_ignore;
  ret->env = (void*)p;
  return ret;
}

static HParseResult* parse_optional(void* env, HParseState* state) {
  HInputStream bak = state->input_stream;
  HParseResult *res0 = h_do_parse((HParser*)env, state);
  if (res0)
    return res0;
  state->input_stream = bak;
  HParsedToken *ast = a_new(HParsedToken, 1);
  ast->token_type = TT_NONE;
  return make_result(state, ast);
}

const HParser* h_optional(const HParser* p) {
  assert_message(p->fn != parse_ignore, "Thou shalt ignore an option, rather than the other way 'round.");
  HParser *ret = g_new(HParser, 1);
  ret->fn = parse_optional;
  ret->env = (void*)p;
  return ret;
}

const HParser* h_sepBy(const HParser* p, const HParser* sep) {
  HParser *res = g_new(HParser, 1);
  HRepeat *env = g_new(HRepeat, 1);
  env->p = p;
  env->sep = sep;
  env->count = 0;
  env->min_p = true;
  res->fn = parse_many;
  res->env = env;
  return res;
}

const HParser* h_sepBy1(const HParser* p, const HParser* sep) {
  HParser *res = g_new(HParser, 1);
  HRepeat *env = g_new(HRepeat, 1);
  env->p = p;
  env->sep = sep;
  env->count = 1;
  env->min_p = true;
  res->fn = parse_many;
  res->env = env;
  return res;
}

static HParseResult* parse_epsilon(void* env, HParseState* state) {
  (void)env;
  HParseResult* res = a_new(HParseResult, 1);
  res->ast = NULL;
  res->arena = state->arena;
  return res;
}

const HParser* h_epsilon_p() {
  HParser *res = g_new(HParser, 1);
  res->fn = parse_epsilon;
  res->env = NULL;
  return res;
}

static HParseResult* parse_indirect(void* env, HParseState* state) {
  return h_do_parse(env, state);
}
void h_bind_indirect(HParser* indirect, HParser* inner) {
  indirect->env = inner;
}

HParser* h_indirect() {
  HParser *res = g_new(HParser, 1);
  res->fn = parse_indirect;
  res->env = NULL;
  return res;
}

typedef struct {
  const HParser *p;
  HPredicate pred;
} HAttrBool;

static HParseResult* parse_attr_bool(void *env, HParseState *state) {
  HAttrBool *a = (HAttrBool*)env;
  HParseResult *res = h_do_parse(a->p, state);
  if (res && res->ast) {
    if (a->pred(res))
      return res;
    else
      return NULL;
  } else
    return NULL;
}

const HParser* h_attr_bool(const HParser* p, HPredicate pred) { 
  HParser *res = g_new(HParser, 1);
  res->fn = parse_attr_bool;
  HAttrBool *env = g_new(HAttrBool, 1);
  env->p = p;
  env->pred = pred;
  res->env = (void*)env;
  return res;
}

typedef struct {
  const HParser *length;
  const HParser *value;
} HLenVal;

static HParseResult* parse_length_value(void *env, HParseState *state) {
  HLenVal *lv = (HLenVal*)env;
  HParseResult *len = h_do_parse(lv->length, state);
  if (!len)
    return NULL;
  if (len->ast->token_type != TT_UINT)
    errx(1, "Length parser must return an unsigned integer");
  HParser epsilon_local = {
    .fn = parse_epsilon,
    .env = NULL
  };
  HRepeat repeat = {
    .p = lv->value,
    .sep = &epsilon_local,
    .count = len->ast->uint,
    .min_p = false
  };
  return parse_many(&repeat, state);
}

const HParser* h_length_value(const HParser* length, const HParser* value) {
  HParser *res = g_new(HParser, 1);
  res->fn = parse_length_value;
  HLenVal *env = g_new(HLenVal, 1);
  env->length = length;
  env->value = value;
  res->env = (void*)env;
  return res;
}

static HParseResult *parse_and(void* env, HParseState* state) {
  HInputStream bak = state->input_stream;
  HParseResult *res = h_do_parse((HParser*)env, state);
  state->input_stream = bak;
  if (res)
    return make_result(state, NULL);
  return NULL;
}

const HParser* h_and(const HParser* p) {
  // zero-width postive lookahead
  HParser *res = g_new(HParser, 1);
  res->env = (void*)p;
  res->fn = parse_and;
  return res;
}

static HParseResult* parse_not(void* env, HParseState* state) {
  HInputStream bak = state->input_stream;
  if (h_do_parse((HParser*)env, state))
    return NULL;
  else {
    state->input_stream = bak;
    return make_result(state, NULL);
  }
}

const HParser* h_not(const HParser* p) {
  HParser *res = g_new(HParser, 1);
  res->fn = parse_not;
  res->env = (void*)p;
  return res;
}

static guint cache_key_hash(gconstpointer key) {
  return djbhash(key, sizeof(HParserCacheKey));
}
static gboolean cache_key_equal(gconstpointer key1, gconstpointer key2) {
  return memcmp(key1, key2, sizeof(HParserCacheKey)) == 0;
}


HParseResult* h_parse(const HParser* parser, const uint8_t* input, size_t length) { 
  // Set up a parse state...
  HArena * arena = h_new_arena(0);
  HParseState *parse_state = a_new_(arena, HParseState, 1);
  parse_state->cache = g_hash_table_new(cache_key_hash, // hash_func
					cache_key_equal);// key_equal_func
  parse_state->input_stream.input = input;
  parse_state->input_stream.index = 0;
  parse_state->input_stream.bit_offset = 8; // bit big endian
  parse_state->input_stream.overrun = 0;
  parse_state->input_stream.endianness = BIT_BIG_ENDIAN | BYTE_BIG_ENDIAN;
  parse_state->input_stream.length = length;
  parse_state->lr_stack = g_queue_new();
  parse_state->recursion_heads = g_hash_table_new(cache_key_hash,
						  cache_key_equal);
  parse_state->arena = arena;
  HParseResult *res = h_do_parse(parser, parse_state);
  g_queue_free(parse_state->lr_stack);
  g_hash_table_destroy(parse_state->recursion_heads);
  // tear down the parse state
  g_hash_table_destroy(parse_state->cache);
  if (!res)
    h_delete_arena(parse_state->arena);

  return res;
}

#ifdef INCLUDE_TESTS

#include "test_suite.h"
static void test_token(void) {
  const HParser *token_ = h_token((const uint8_t*)"95\xa2", 3);

  g_check_parse_ok(token_, "95\xa2", 3, "<39.35.a2>");
  g_check_parse_failed(token_, "95", 2);
}

static void test_ch(void) {
  const HParser *ch_ = h_ch(0xa2);

  g_check_parse_ok(ch_, "\xa2", 1, "u0xa2");
  g_check_parse_failed(ch_, "\xa3", 1);
}

static void test_ch_range(void) {
  const HParser *range_ = h_ch_range('a', 'c');

  g_check_parse_ok(range_, "b", 1, "u0x62");
  g_check_parse_failed(range_, "d", 1);
}

//@MARK_START
static void test_int64(void) {
  const HParser *int64_ = h_int64();

  g_check_parse_ok(int64_, "\xff\xff\xff\xfe\x00\x00\x00\x00", 8, "s-0x200000000");
  g_check_parse_failed(int64_, "\xff\xff\xff\xfe\x00\x00\x00", 7);
}

static void test_int32(void) {
  const HParser *int32_ = h_int32();

  g_check_parse_ok(int32_, "\xff\xfe\x00\x00", 4, "s-0x20000");
  g_check_parse_failed(int32_, "\xff\xfe\x00", 3);
}

static void test_int16(void) {
  const HParser *int16_ = h_int16();

  g_check_parse_ok(int16_, "\xfe\x00", 2, "s-0x200");
  g_check_parse_failed(int16_, "\xfe", 1);
}

static void test_int8(void) {
  const HParser *int8_ = h_int8();

  g_check_parse_ok(int8_, "\x88", 1, "s-0x78");
  g_check_parse_failed(int8_, "", 0);
}

static void test_uint64(void) {
  const HParser *uint64_ = h_uint64();

  g_check_parse_ok(uint64_, "\x00\x00\x00\x02\x00\x00\x00\x00", 8, "u0x200000000");
  g_check_parse_failed(uint64_, "\x00\x00\x00\x02\x00\x00\x00", 7);
}

static void test_uint32(void) {
  const HParser *uint32_ = h_uint32();

  g_check_parse_ok(uint32_, "\x00\x02\x00\x00", 4, "u0x20000");
  g_check_parse_failed(uint32_, "\x00\x02\x00", 3);
}

static void test_uint16(void) {
  const HParser *uint16_ = h_uint16();

  g_check_parse_ok(uint16_, "\x02\x00", 2, "u0x200");
  g_check_parse_failed(uint16_, "\x02", 1);
}

static void test_uint8(void) {
  const HParser *uint8_ = h_uint8();

  g_check_parse_ok(uint8_, "\x78", 1, "u0x78");
  g_check_parse_failed(uint8_, "", 0);
}
//@MARK_END

static void test_int_range(void) {
  const HParser *int_range_ = h_int_range(h_uint8(), 3, 10);
  
  g_check_parse_ok(int_range_, "\x05", 1, "u0x5");
  g_check_parse_failed(int_range_, "\xb", 1);
}

#if 0
static void test_float64(void) {
  const HParser *float64_ = h_float64();

  g_check_parse_ok(float64_, "\x3f\xf0\x00\x00\x00\x00\x00\x00", 8, 1.0);
  g_check_parse_failed(float64_, "\x3f\xf0\x00\x00\x00\x00\x00", 7);
}

static void test_float32(void) {
  const HParser *float32_ = h_float32();

  g_check_parse_ok(float32_, "\x3f\x80\x00\x00", 4, 1.0);
  g_check_parse_failed(float32_, "\x3f\x80\x00");
}
#endif


static void test_whitespace(void) {
  const HParser *whitespace_ = h_whitespace(h_ch('a'));

  g_check_parse_ok(whitespace_, "a", 1, "u0x61");
  g_check_parse_ok(whitespace_, " a", 2, "u0x61");
  g_check_parse_ok(whitespace_, "  a", 3, "u0x61");
  g_check_parse_ok(whitespace_, "\ta", 2, "u0x61");
  g_check_parse_failed(whitespace_, "_a", 2);
}

#include <ctype.h>

const HParsedToken* upcase(const HParseResult *p) {
  switch(p->ast->token_type) {
  case TT_SEQUENCE:
    {
      HParsedToken *ret = a_new_(p->arena, HParsedToken, 1);
      HCountedArray *seq = h_carray_new_sized(p->arena, p->ast->seq->used);
      ret->token_type = TT_SEQUENCE;
      for (size_t i=0; i<p->ast->seq->used; ++i) {
	if (TT_UINT == ((HParsedToken*)p->ast->seq->elements[i])->token_type) {
	  HParsedToken *tmp = a_new_(p->arena, HParsedToken, 1);
	  tmp->token_type = TT_UINT;
	  tmp->uint = toupper(((HParsedToken*)p->ast->seq->elements[i])->uint);
	  h_carray_append(seq, tmp);
	} else {
	  h_carray_append(seq, p->ast->seq->elements[i]);
	}
      }
      ret->seq = seq;
      return (const HParsedToken*)ret;
    }
  case TT_UINT:
    {
      HParsedToken *ret = a_new_(p->arena, HParsedToken, 1);
      ret->token_type = TT_UINT;
      ret->uint = toupper(p->ast->uint);
      return (const HParsedToken*)ret;
    }
  default:
    return p->ast;
  }
}

static void test_action(void) {
  const HParser *action_ = h_action(h_sequence(h_choice(h_ch('a'), 
							h_ch('A'), 
							NULL), 
					       h_choice(h_ch('b'), 
							h_ch('B'), 
						      NULL), 
					       NULL), 
				    upcase);
  
  g_check_parse_ok(action_, "ab", 2, "(u0x41 u0x42)");
  g_check_parse_ok(action_, "AB", 2, "(u0x41 u0x42)");
}

static void test_not_in(void) {
  uint8_t options[3] = { 'a', 'b', 'c' };
  const HParser *not_in_ = h_not_in(options, 3);
  g_check_parse_ok(not_in_, "d", 1, "u0x64");
  g_check_parse_failed(not_in_, "a", 1);

}

static void test_end_p(void) {
  const HParser *end_p_ = h_sequence(h_ch('a'), h_end_p(), NULL);
  g_check_parse_ok(end_p_, "a", 1, "(u0x61)");
  g_check_parse_failed(end_p_, "aa", 2);
}

static void test_nothing_p(void) {
  const HParser *nothing_p_ = h_nothing_p();
  g_check_parse_failed(nothing_p_, "a", 1);
}

static void test_sequence(void) {
  const HParser *sequence_1 = h_sequence(h_ch('a'), h_ch('b'), NULL);
  const HParser *sequence_2 = h_sequence(h_ch('a'), h_whitespace(h_ch('b')), NULL);

  g_check_parse_ok(sequence_1, "ab", 2, "(u0x61 u0x62)");
  g_check_parse_failed(sequence_1, "a", 1);
  g_check_parse_failed(sequence_1, "b", 1);
  g_check_parse_ok(sequence_2, "ab", 2, "(u0x61 u0x62)");
  g_check_parse_ok(sequence_2, "a b", 3, "(u0x61 u0x62)");
  g_check_parse_ok(sequence_2, "a  b", 4, "(u0x61 u0x62)");  
}

static void test_choice(void) {
  const HParser *choice_ = h_choice(h_ch('a'), h_ch('b'), NULL);

  g_check_parse_ok(choice_, "a", 1, "u0x61");
  g_check_parse_ok(choice_, "b", 1, "u0x62");
  g_check_parse_failed(choice_, "c", 1);
}

static void test_butnot(void) {
  const HParser *butnot_1 = h_butnot(h_ch('a'), h_token((const uint8_t*)"ab", 2));
  const HParser *butnot_2 = h_butnot(h_ch_range('0', '9'), h_ch('6'));

  g_check_parse_ok(butnot_1, "a", 1, "u0x61");
  g_check_parse_failed(butnot_1, "ab", 2);
  g_check_parse_ok(butnot_1, "aa", 2, "u0x61");
  g_check_parse_failed(butnot_2, "6", 1);
}

static void test_difference(void) {
  const HParser *difference_ = h_difference(h_token((const uint8_t*)"ab", 2), h_ch('a'));

  g_check_parse_ok(difference_, "ab", 2, "<61.62>");
  g_check_parse_failed(difference_, "a", 1);
}

static void test_xor(void) {
  const HParser *xor_ = h_xor(h_ch_range('0', '6'), h_ch_range('5', '9'));

  g_check_parse_ok(xor_, "0", 1, "u0x30");
  g_check_parse_ok(xor_, "9", 1, "u0x39");
  g_check_parse_failed(xor_, "5", 1);
  g_check_parse_failed(xor_, "a", 1);
}

static void test_many(void) {
  const HParser *many_ = h_many(h_choice(h_ch('a'), h_ch('b'), NULL));
  g_check_parse_ok(many_, "adef", 4, "(u0x61)");
  g_check_parse_ok(many_, "bdef", 4, "(u0x62)");
  g_check_parse_ok(many_, "aabbabadef", 10, "(u0x61 u0x61 u0x62 u0x62 u0x61 u0x62 u0x61)");
  g_check_parse_ok(many_, "daabbabadef", 11, "()");
}

static void test_many1(void) {
  const HParser *many1_ = h_many1(h_choice(h_ch('a'), h_ch('b'), NULL));

  g_check_parse_ok(many1_, "adef", 4, "(u0x61)");
  g_check_parse_ok(many1_, "bdef", 4, "(u0x62)");
  g_check_parse_ok(many1_, "aabbabadef", 10, "(u0x61 u0x61 u0x62 u0x62 u0x61 u0x62 u0x61)");
  g_check_parse_failed(many1_, "daabbabadef", 11);  
}

static void test_repeat_n(void) {
  const HParser *repeat_n_ = h_repeat_n(h_choice(h_ch('a'), h_ch('b'), NULL), 2);

  g_check_parse_failed(repeat_n_, "adef", 4);
  g_check_parse_ok(repeat_n_, "abdef", 5, "(u0x61 u0x62)");
  g_check_parse_failed(repeat_n_, "dabdef", 6);
}

static void test_optional(void) {
  const HParser *optional_ = h_sequence(h_ch('a'), h_optional(h_choice(h_ch('b'), h_ch('c'), NULL)), h_ch('d'), NULL);
  
  g_check_parse_ok(optional_, "abd", 3, "(u0x61 u0x62 u0x64)");
  g_check_parse_ok(optional_, "acd", 3, "(u0x61 u0x63 u0x64)");
  g_check_parse_ok(optional_, "ad", 2, "(u0x61 null u0x64)");
  g_check_parse_failed(optional_, "aed", 3);
  g_check_parse_failed(optional_, "ab", 2);
  g_check_parse_failed(optional_, "ac", 2);
}

static void test_ignore(void) {
  const HParser *ignore_ = h_sequence(h_ch('a'), h_ignore(h_ch('b')), h_ch('c'), NULL);

  g_check_parse_ok(ignore_, "abc", 3, "(u0x61 u0x63)");
  g_check_parse_failed(ignore_, "ac", 2);
}

static void test_sepBy1(void) {
  const HParser *sepBy1_ = h_sepBy1(h_choice(h_ch('1'), h_ch('2'), h_ch('3'), NULL), h_ch(','));

  g_check_parse_ok(sepBy1_, "1,2,3", 5, "(u0x31 u0x32 u0x33)");
  g_check_parse_ok(sepBy1_, "1,3,2", 5, "(u0x31 u0x33 u0x32)");
  g_check_parse_ok(sepBy1_, "1,3", 3, "(u0x31 u0x33)");
  g_check_parse_ok(sepBy1_, "3", 1, "(u0x33)");
}

static void test_epsilon_p(void) {
  const HParser *epsilon_p_1 = h_sequence(h_ch('a'), h_epsilon_p(), h_ch('b'), NULL);
  const HParser *epsilon_p_2 = h_sequence(h_epsilon_p(), h_ch('a'), NULL);
  const HParser *epsilon_p_3 = h_sequence(h_ch('a'), h_epsilon_p(), NULL);
  
  g_check_parse_ok(epsilon_p_1, "ab", 2, "(u0x61 u0x62)");
  g_check_parse_ok(epsilon_p_2, "a", 1, "(u0x61)");
  g_check_parse_ok(epsilon_p_3, "a", 1, "(u0x61)");
}

static void test_attr_bool(void) {

}

static void test_and(void) {
  const HParser *and_1 = h_sequence(h_and(h_ch('0')), h_ch('0'), NULL);
  const HParser *and_2 = h_sequence(h_and(h_ch('0')), h_ch('1'), NULL);
  const HParser *and_3 = h_sequence(h_ch('1'), h_and(h_ch('2')), NULL);

  g_check_parse_ok(and_1, "0", 1, "(u0x30)");
  g_check_parse_failed(and_2, "0", 1);
  g_check_parse_ok(and_3, "12", 2, "(u0x31)");
}

static void test_not(void) {
  const HParser *not_1 = h_sequence(h_ch('a'), h_choice(h_ch('+'), h_token((const uint8_t*)"++", 2), NULL), h_ch('b'), NULL);
  const HParser *not_2 = h_sequence(h_ch('a'),
				   h_choice(h_sequence(h_ch('+'), h_not(h_ch('+')), NULL),
					  h_token((const uint8_t*)"++", 2),
					  NULL), h_ch('b'), NULL);

  g_check_parse_ok(not_1, "a+b", 3, "(u0x61 u0x2b u0x62)");
  g_check_parse_failed(not_1, "a++b", 4);
  g_check_parse_ok(not_2, "a+b", 3, "(u0x61 (u0x2b) u0x62)");
  g_check_parse_ok(not_2, "a++b", 4, "(u0x61 <2b.2b> u0x62)");
}

void register_parser_tests(void) {
  g_test_add_func("/core/parser/token", test_token);
  g_test_add_func("/core/parser/ch", test_ch);
  g_test_add_func("/core/parser/ch_range", test_ch_range);
  g_test_add_func("/core/parser/int64", test_int64);
  g_test_add_func("/core/parser/int32", test_int32);
  g_test_add_func("/core/parser/int16", test_int16);
  g_test_add_func("/core/parser/int8", test_int8);
  g_test_add_func("/core/parser/uint64", test_uint64);
  g_test_add_func("/core/parser/uint32", test_uint32);
  g_test_add_func("/core/parser/uint16", test_uint16);
  g_test_add_func("/core/parser/uint8", test_uint8);
  g_test_add_func("/core/parser/int_range", test_int_range);
#if 0
  g_test_add_func("/core/parser/float64", test_float64);
  g_test_add_func("/core/parser/float32", test_float32);
#endif
  g_test_add_func("/core/parser/whitespace", test_whitespace);
  g_test_add_func("/core/parser/action", test_action);
  g_test_add_func("/core/parser/not_in", test_not_in);
  g_test_add_func("/core/parser/end_p", test_end_p);
  g_test_add_func("/core/parser/nothing_p", test_nothing_p);
  g_test_add_func("/core/parser/sequence", test_sequence);
  g_test_add_func("/core/parser/choice", test_choice);
  g_test_add_func("/core/parser/butnot", test_butnot);
  g_test_add_func("/core/parser/difference", test_difference);
  g_test_add_func("/core/parser/xor", test_xor);
  g_test_add_func("/core/parser/many", test_many);
  g_test_add_func("/core/parser/many1", test_many1);
  g_test_add_func("/core/parser/repeat_n", test_repeat_n);
  g_test_add_func("/core/parser/optional", test_optional);
  g_test_add_func("/core/parser/sepBy1", test_sepBy1);
  g_test_add_func("/core/parser/epsilon_p", test_epsilon_p);
  g_test_add_func("/core/parser/attr_bool", test_attr_bool);
  g_test_add_func("/core/parser/and", test_and);
  g_test_add_func("/core/parser/not", test_not);
  g_test_add_func("/core/parser/ignore", test_ignore);
}

#endif // #ifdef INCLUDE_TESTS