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

#include "treetrie.h"
#include "fasthash.h"

/* These two only included for tt_dump_arena_dot_styled. */
#include "route.h"
#include <arpa/inet.h>

/* Customized special-purpose fasthash variation */
#define mix(h) ({					\
      (h) ^= (h) >> 23;					\
      (h) *= 0x2127599bf4325c37ULL;			\
      (h) ^= (h) >> 47; })
static inline uint64_t fasthash_4_ints(uint32_t v1, uint32_t v2, uint32_t v3, uint32_t v4) {
  const uint64_t    m = 0x880355f21e6d1965ULL;
  uint64_t h = (16 * m);
  uint64_t v;
  v = (((uint64_t) v2) << 32) | v1;
  h ^= mix(v);
  h *= m;
  v = (((uint64_t) v4) << 32) | v3;
  h ^= mix(v);
  h *= m;
  return mix(h);
}

static inline tt_hash_t hash(uint32_t tag,
			     uint32_t index,
			     tt_node_ptr_t a,
			     tt_node_ptr_t b)
{
  uint64_t x = fasthash_4_ints(tag, index, a, b);
  return x - (x >> 32);

  /* uint32_t keyblock[4] = { tag, */
  /* 			   index, */
  /* 			   a, */
  /* 			   b }; */
  /* assert(sizeof(keyblock) == 4 * sizeof(uint32_t)); */
  /* return (tt_hash_t) fasthash32(keyblock, sizeof(keyblock), 0); */
}

static inline tt_hash_t tt_hash_node(tt_arena_t *a, tt_node_ptr_t p) {
  tt_node_idx_t i = tt_ptr_idx(p);
  return hash(tt_ptr_tag(p),
	      a->headers[i].inuse.index,
	      a->nodes[i].a,
	      a->nodes[i].b);
}

static void chain_init(tt_arena_t *a, tt_free_chain_t *chain) {
  chain->head = chain->tail = TT_NO_IDX;
}

static void chain_append(tt_arena_t *a, tt_free_chain_t *chain, tt_node_idx_t i) {
  a->headers[i].next_free = TT_NO_IDX;
  if (chain->tail == TT_NO_IDX) {
    chain->head = i;
  } else {
    a->headers[chain->tail].next_free = i;
  }
  chain->tail = i;
}

static void chain_prepend(tt_arena_t *a, tt_free_chain_t *chain, tt_node_idx_t i) {
  a->headers[i].next_free = chain->head;
  if (chain->tail == TT_NO_IDX) {
    chain->tail = i;
  }
  chain->head = i;
}

/* Does not modify chain2. */
static void chain_splice(tt_arena_t *a, tt_free_chain_t *chain1, tt_free_chain_t *chain2) {
  if (chain2->head == TT_NO_IDX) {
    /* do nothing */
  } else if (chain1->head == TT_NO_IDX) {
    *chain1 = *chain2;
  } else {
    a->headers[chain1->tail].next_free = chain2->head;
    chain1->tail = chain2->tail;
  }
}

static tt_node_idx_t chain_pop(tt_arena_t *a, tt_free_chain_t *chain) {
  tt_node_idx_t i = chain->head;
  if (i != TT_NO_IDX) {
    chain->head = a->headers[i].next_free;
    if (chain->tail == i) {
      chain->tail = chain->head;
    }
  }
  return i;
}

int tt_arena_init(tt_arena_t *a,
		  void *atom_context,
		  void (*atom_incref)(void *context, tt_arena_t *a, tt_atom_t atom),
		  void (*atom_decref)(void *context, tt_arena_t *a, tt_atom_t atom))
{
  a->atom_context = atom_context;
  a->atom_incref = atom_incref;
  a->atom_decref = atom_decref;
  a->max_probe = 0;
  a->table_length = 16411; /* 16384; */
  a->table = calloc(a->table_length, sizeof(a->table[0]));
  a->headers = calloc(a->table_length, sizeof(a->headers[0]));
  a->nodes = calloc(a->table_length, sizeof(a->nodes[0]));
  a->free_count = 0;
  chain_init(a, &a->free_chain);

  if (a->table == NULL || a->headers == NULL || a->nodes == NULL) {
    free(a->table);
    free(a->headers);
    free(a->nodes);
    errno = ENOMEM;
    return -1;
  }

  {
    int i;
    for (i = 0; i < a->table_length; i++) {
      chain_append(a, &a->free_chain, i);
      a->free_count++;
    }
  }

  return 0;
}

static void register_node(tt_arena_t *a, tt_node_ptr_t p, tt_hash_t initial_hash) {
  tt_hash_t h = initial_hash;
  int i = 0;
  while (1) {
    unsigned int index = (h + i) % a->table_length;
    tt_node_ptr_t candidate = a->table[index].ptr;

    /* printf("checking robinhood at h %d i %d index %d candidate %d\n", h, i, index, candidate); */

    if (i > a->max_probe) {
      a->max_probe = i;
    }

    if (TT_NO_PTR_P(candidate)) {
      /* This slot in the table is free. */
      /* printf("slot free!\n"); */
      a->table[index].ptr = p;
      a->table[index].hash = h;
      break;
    }

    /* printf("slot not free.\n"); */
    {
      tt_hash_t candidate_h = a->table[index].hash;
      int distance = index - (candidate_h % a->table_length);
      if (distance < 0) distance += a->table_length;

      if (distance < i) {
	a->table[index].ptr = p;
	a->table[index].hash = h;
	h = candidate_h;
	i = distance + 1;
	p = candidate;
      } else {
	/* keep scanning. */
	i++;
      }
    }
  }
}

static int tt_grow(tt_arena_t *a) {
  tt_hashtable_entry_t *old_table = a->table;
  unsigned int old_table_length = a->table_length;
  unsigned int new_table_length = old_table_length << 1;

  /* printf("PREGROW\n"); */
  /* tt_dump_arena(a, 1); */

  {
    tt_hashtable_entry_t *new_table = calloc(new_table_length, sizeof(a->table[0]));
    tt_header_t *new_headers = realloc(a->headers, new_table_length * sizeof(a->headers[0]));
    tt_node_t *new_nodes = realloc(a->nodes, new_table_length * sizeof(a->nodes[0]));

    if (new_table == NULL || new_headers == NULL || new_nodes == NULL) {
      free(new_table);
      free(new_headers);
      free(new_nodes);
      errno = ENOMEM;
      return -1;
    }

    memset(new_headers + old_table_length, 0,
	   (new_table_length - old_table_length) * sizeof(a->headers[0]));
    memset(new_nodes + old_table_length, 0,
	   (new_table_length - old_table_length) * sizeof(a->nodes[0]));

    a->max_probe = 0;
    a->table_length = new_table_length;
    a->table = new_table;
    a->headers = new_headers;
    a->nodes = new_nodes;

    {
      int i;
      for (i = old_table_length; i < new_table_length; i++) {
	chain_append(a, &a->free_chain, i);
	a->free_count++;
      }
    }
  }

  /* printf("//////////////////////////////////////// GROW starting (length %d)\n", a->table_length); */

  {
    int i;
    for (i = 0; i < old_table_length; i++) {
      tt_node_ptr_t p = old_table[i].ptr;
      tt_hash_t h = old_table[i].hash;
      if (!TT_NO_PTR_P(p)) {
	register_node(a, p, h);
      }
    }
  }

  /* printf("//////////////////////////////////////// GROW finished (length %d)\n", a->table_length); */

  /* printf("POSTGROW\n"); */
  /* tt_dump_arena_summary(a); */

  free(old_table);
  return 0;
}

void tt_arena_done(tt_arena_t *a) {
  free(a->table);
  free(a->headers);
  free(a->nodes);
  memset(a, 0, sizeof(*a));
}

static size_t arena_size(tt_arena_t *a) {
  return sizeof(*a) +
    (a->table_length * sizeof(a->table[0])) +
    (a->table_length * sizeof(a->headers[0])) +
    (a->table_length * sizeof(a->nodes[0]));
}

void tt_dump_arena_summary(tt_arena_t *a) {
  printf("size in bytes: %lu\n", arena_size(a));
  printf("max_probe: %u\n", a->max_probe);
  printf("table_length: %u\n", a->table_length);
  printf("free_count: %u\n", a->free_count);
}

void tt_dump_arena(tt_arena_t *a, int show_free_chain) {
  tt_dump_arena_summary(a);

  if (show_free_chain) {
    int chain_counter = 0;
    tt_node_idx_t fp = a->free_chain.head;
    printf("free_chain:");
    while (fp != TT_NO_IDX) {
      if ((chain_counter % 10) == 0) {
	printf("\n   ");
      }
      printf(" %d", fp);
      fp = a->headers[fp].next_free;
      chain_counter++;
    }
    printf("\n");
  }

  {
    int i;
    for (i = 0; i < a->table_length; i++) {
      tt_node_ptr_t p = a->table[i].ptr;
      tt_node_idx_t n = tt_ptr_idx(p);

      if (TT_NO_PTR_P(p)) {
	continue;
      }

      if (n >= a->table_length) {
	printf("%12u -> %12u ?!?!?!\n", i, n);
      } else {
	tt_hash_t h = a->table[i].hash;
	int distance = i - (h % a->table_length);
	if (distance < 0) distance += a->table_length;
	printf("%12u -> %12u: dist %d ref %d ",
	       i,
	       n,
	       distance,
	       a->headers[n].inuse.refcount);
	switch (tt_ptr_tag(p)) {
	  case TT_TAG_TAIL:
	    printf("tail %u/%u\n",
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a));
	    break;
	  case TT_TAG_OK:
	    printf("ok %u/%u\n",
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a));
	    break;
	  case TT_TAG_BRANCH:
	    printf("branch %u/%u %u/%u\n",
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a),
		   tt_ptr_idx(a->nodes[n].b),
		   tt_ptr_tag(a->nodes[n].b));
	    break;
	  case TT_TAG_LEAF:
	    printf("leaf %u/%u %d\n",
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a),
		   (int) a->nodes[n].b);
	    break;
	  case TT_TAG_NODE:
	    printf("node index %d, %u/%u %u/%u\n",
		   a->headers[n].inuse.index,
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a),
		   tt_ptr_idx(a->nodes[n].b),
		   tt_ptr_tag(a->nodes[n].b));
	    break;
	  case TT_TAG_DICT:
	    printf("dict %u/%u %u\n",
		   tt_ptr_idx(a->nodes[n].a),
		   tt_ptr_tag(a->nodes[n].a),
		   a->nodes[n].b);
	    break;
	  default:
	    printf("???? %08x\n", p);
	    assert(0);
	}
      }
    }
  }
}

static void dump_dot_edge(tt_arena_t *a, tt_node_ptr_t p, int lr, char const *edgename) {
  tt_node_idx_t n = tt_ptr_idx(p);
  tt_tag_t target_t = tt_ptr_tag(lr ? a->nodes[n].b : a->nodes[n].a);
  if (target_t != TT_TAG_INVALID && target_t != TT_TAG_SPECIAL) {
    printf("  i%u_%u -> i%u_%u [label=\"%s\"];\n",
	   n,
	   tt_ptr_tag(p),
	   tt_ptr_idx(lr ? a->nodes[n].b : a->nodes[n].a),
	   target_t,
	   edgename);
  }
}

void tt_dump_arena_dot_styled(char const *rootlabel,
			      tt_node_ptr_t rootptr,
			      tt_arena_t *a,
			      int flags)
{
  int i;

  printf("digraph Arena {\n");
  printf("  root [shape=box, label=\"%s\"];\n", rootlabel);
  if (tt_ptr_tag(rootptr) != TT_TAG_INVALID && tt_ptr_tag(rootptr) != TT_TAG_SPECIAL) {
    printf("  root -> i%u_%u;\n",
	   tt_ptr_idx(rootptr),
	   tt_ptr_tag(rootptr));
  }
  for (i = 0; i < a->table_length; i++) {
    tt_node_ptr_t p = a->table[i].ptr;
    tt_node_idx_t n = tt_ptr_idx(p);

    if (TT_NO_PTR_P(p)) {
      continue;
    }

    if (n >= a->table_length) {
      printf("  // %12u -> %12u ?!?!?!\n", i, n);
    } else {
      tt_hash_t h = a->table[i].hash;
      int distance = i - (h % a->table_length);
      if (distance < 0) distance += a->table_length;
      printf("  i%u_%u [",
	     n,
	     tt_ptr_tag(p));
      switch (tt_ptr_tag(p)) {
	case TT_TAG_TAIL:
	  printf("label=\"tail");
	  break;
	case TT_TAG_OK:
	  printf("shape=underline,label=\"ok");
	  break;
	case TT_TAG_BRANCH:
	  printf("label=\"branch");
	  break;
	case TT_TAG_LEAF:
	  if (flags & TT_STYLE_TEXT_LABELS) {
	    char buf[5];
	    int v = (int) a->nodes[n].b;
	    if (v < -9 || v >= 32) {
	      int j;
	      v = htonl(v);
	      memcpy(buf, &v, 4);
	      for (j = 0; j < 4; j++) {
		if (buf[j] < 32) { buf[j] = ' '; }
	      }
	      buf[4] = '\0';
	    } else {
	      switch (v) {
		case TT_WILD: buf[0] = '*'; buf[1] = '\0'; break;
		case TT_BOS: buf[0] = buf[1] = '<'; buf[2] = '\0'; break;
		case TT_EOS: buf[0] = buf[1] = '>'; buf[2] = '\0'; break;
		case TT_BOC: buf[0] = buf[1] = '{'; buf[2] = '\0'; break;
		case TT_EOC: buf[0] = buf[1] = '}'; buf[2] = '\0'; break;
		default:
		  snprintf(buf, sizeof(buf), "%d", v);
		  buf[4] = '\0';
	      }
	    }
	    printf("shape=underline,label=\"leaf '%s'", buf);
	  } else {
	    printf("shape=underline,label=\"leaf a%d", (int) a->nodes[n].b);
	  }
	  break;
	case TT_TAG_NODE:
	  printf("label=\"node @%d", a->headers[n].inuse.index);
	  break;
	case TT_TAG_DICT:
	  printf("label=\"dict s%u", a->nodes[n].b);
	  break;
	default:
	  printf("???? %08x\n", p);
	  assert(0);
      }
      /* printf(" #%u d%d r%d\"];\n", i, distance, a->headers[n].inuse.refcount); */
      if (flags & TT_STYLE_HIDE_DETAILS) {
	printf("\"];\n");
      } else {
	printf(" i%u r%d\"];\n", n, a->headers[n].inuse.refcount);
      }
      switch (tt_ptr_tag(p)) {
	case TT_TAG_TAIL:
	  dump_dot_edge(a, p, 0, "trie");
	  break;
	case TT_TAG_OK:
	  dump_dot_edge(a, p, 0, "dict");
	  break;
	case TT_TAG_BRANCH:
	  dump_dot_edge(a, p, 0, "wild");
	  dump_dot_edge(a, p, 1, "others");
	  break;
	case TT_TAG_LEAF:
	  dump_dot_edge(a, p, 0, "trie");
	  break;
	case TT_TAG_NODE:
	  dump_dot_edge(a, p, 0, "zero");
	  dump_dot_edge(a, p, 1, "one");
	  break;
	case TT_TAG_DICT:
	  dump_dot_edge(a, p, 0, "root");
	  break;
	default:
	  printf("???? %08x\n", p);
	  assert(0);
      }
    }
  }
  printf("}\n");
}

void tt_dump_arena_dot(char const *rootlabel, tt_node_ptr_t rootptr, tt_arena_t *a) {
  tt_dump_arena_dot_styled(rootlabel, rootptr, a, 0);
}

void tt_arena_flush1(tt_arena_t *a, tt_free_chain_t *c) {
  tt_node_idx_t i = a->free_chain.head;
  chain_splice(a, c, &a->free_chain);
  chain_init(a, &a->free_chain);
  while (i != TT_NO_IDX) {
    tt_drop(a, a->nodes[i].a);
    tt_drop(a, a->nodes[i].b);
    a->nodes[i].a = TT_NO_PTR;
    a->nodes[i].b = TT_NO_PTR;
    i = a->headers[i].next_free;
  }
}

void tt_arena_flush(tt_arena_t *a) {
  tt_free_chain_t c;
  c.head = c.tail = TT_NO_IDX;
  while (a->free_chain.head != TT_NO_IDX) {
    tt_arena_flush1(a, &c);
  }
  a->free_chain = c;
}

static inline int heap_tag_p(tt_node_ptr_t p) {
  tt_tag_t tag = tt_ptr_tag(p);
  return tag != TT_TAG_SPECIAL && tag != TT_TAG_INVALID;
}

static void recycle_node(tt_arena_t *a, tt_node_ptr_t p) {
  tt_node_idx_t ni = tt_ptr_idx(p);
  tt_hash_t h;
  int i;

  /* printf("++++++++++++++++++++++++++++++++++++++++ recycling %d\n", ni); */

  assert(heap_tag_p(p));
  h = tt_hash_node(a, p);

  switch (tt_ptr_tag(p)) {
    case TT_TAG_LEAF:
      a->atom_decref(a->atom_context, a, a->nodes[ni].b);
      a->nodes[ni].b = TT_NO_PTR;
      break;
    case TT_TAG_DICT:
      a->nodes[ni].b = TT_NO_PTR;
      break;
    default:
      break;
  }
  chain_prepend(a, &a->free_chain, ni);
  a->free_count++;

  for (i = 0; i < a->max_probe+1; i++) {
    unsigned int index = (h + i) % a->table_length;
    tt_node_ptr_t candidate = a->table[index].ptr;

    /* printf("hunting i=%d index=%d p=%d candidate=%d\n", i, index, p, candidate); */
    assert(!TT_NO_PTR_P(candidate)); /* Internal error if node not in table */

    if (candidate == p) {
      /* We found it. Now swap in elements. */
      while (1) {
	unsigned int nextindex = (index + 1) % a->table_length;
	tt_node_ptr_t next_p = a->table[nextindex].ptr;
	tt_hash_t next_h;
	int distance;

	a->table[index].ptr = TT_NO_PTR;

	if (TT_NO_PTR_P(next_p)) {
	  break;
	}

	next_h = a->table[nextindex].hash;
	distance = nextindex - (next_h % a->table_length);
	if (distance < 0) distance += a->table_length;

	if (distance == 0) {
	  break;
	}

	a->table[index].ptr = next_p;
	a->table[index].hash = next_h;
	index = nextindex;
      }
      break;
    }
  }
}

inline tt_node_ptr_t tt_grab(tt_arena_t *a, tt_node_ptr_t p) {
  tt_node_idx_t i = tt_ptr_idx(p);
  tt_tag_t t = tt_ptr_tag(p);
  if (t != TT_TAG_INVALID && t != TT_TAG_SPECIAL
      && a->headers[i].inuse.refcount < TT_REFCOUNT_LIMIT) {
    a->headers[i].inuse.refcount++;
  }
  return p;
}

inline void tt_drop(tt_arena_t *a, tt_node_ptr_t p) {
  tt_node_idx_t i = tt_ptr_idx(p);
  tt_tag_t t = tt_ptr_tag(p);
  if (t != TT_TAG_INVALID && t != TT_TAG_SPECIAL) {
    uint32_t oldcount = a->headers[i].inuse.refcount;
    if (oldcount < TT_REFCOUNT_LIMIT) {
      /* printf("++++++++++++++++++++++++++++++ dropping %d\n", i); */
      assert(oldcount != 0);
      if (--(a->headers[i].inuse.refcount) == 0) {
	recycle_node(a, p);
      }
    }
  }
}

tt_node_ptr_t tt_arena_cons(tt_arena_t *a,
			    tt_tag_t tag,
			    uint32_t nindex,
			    tt_node_ptr_t na,
			    tt_node_ptr_t nb)
{
  tt_hash_t h = hash(tag, nindex, na, nb);
  int i;

  for (i = 0; i < a->max_probe+1; i++) {
    unsigned int index = (h + i) % a->table_length;
    tt_node_ptr_t candidate = a->table[index].ptr;
    tt_node_idx_t candidate_i = tt_ptr_idx(candidate);

    /* printf("cons at %d candidate %d\n", i, candidate); */
    if (TT_NO_PTR_P(candidate)) {
      /* printf("cons empty cell\n"); */
      break;
    }

    {
      tt_hash_t candidate_h = a->table[index].hash;
      int distance = index - (candidate_h % a->table_length);
      if (distance < 0) distance += a->table_length;

      if (i > distance) {
	/* printf("early exit as we found a slot that would have been used instead\n"); */
	break;
      }
    }

    /* printf("tag %d %d\n", tt_ptr_tag(candidate), tag); */
    /* printf("index %d %d\n", a->headers[candidate].inuse.index, nindex); */
    /* printf("a %d %d\n", a->nodes[candidate].a, na); */
    /* printf("b %d %d\n", a->nodes[candidate].b, nb); */

    if (tt_ptr_tag(candidate) == tag &&
	a->headers[candidate_i].inuse.index == nindex &&
	a->nodes[candidate_i].a == na &&
	a->nodes[candidate_i].b == nb) {
      /* printf("cons located correct candidate\n"); */
      return candidate;
    }
  }

  /* Not found */
  /* printf("cons needs to alloc\n"); */

  if (a->free_count < (a->table_length >> 2)) {
    if (tt_grow(a) != 0) {
      return TT_NO_PTR;
    }
  }

  {
    tt_node_idx_t node = chain_pop(a, &a->free_chain);
    tt_node_ptr_t p = tt_mkptr(node, tag);

    tt_grab(a, na);
    switch (tag) {
      case TT_TAG_LEAF:
	a->atom_incref(a->atom_context, a, nb);
	break;
      case TT_TAG_DICT:
	break;
      default:
	tt_grab(a, nb);
    }

    tt_drop(a, a->nodes[node].a);
    tt_drop(a, a->nodes[node].b);
    a->free_count--;

    a->headers[node].inuse.refcount = 0;
    a->headers[node].inuse.index = nindex;
    a->nodes[node].a = na;
    a->nodes[node].b = nb;

    register_node(a, p, h);
    return p;
  }
}