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

/*
 * FNV-1 hash implementation (32-bit aka FNV32_1).
 *
 * See http://isthe.com/chongo/tech/comp/fnv/
 */
uint32_t fnv32_1(uint8_t * data, size_t data_len) {
  uint32_t hash;

  /* Constants, for 32-bit only. */
  uint32_t offset_basis = (uint32_t) 2166136261UL;
  uint32_t FNV_prime = (uint32_t) 16777619UL;

  hash = offset_basis;
  for (size_t i = 0; i < data_len; i++) {
    hash = hash * FNV_prime;    /* implictly modulo 2^32 */
    hash = hash ^ data[i];      /* implictly only on lower octet. */
  }
  return hash;
}

/* Compute FNV-1 hash for the given string (without NUL byte). */
uint32_t fnv32_1_str(char *string) {
  return fnv32_1((uint8_t *) string, strlen(string));
}

/* Test FNV32_1 */
void test_fnv32_1() {
  assert(fnv32_1_str("03SB[") == 0x00000000UL);
  assert(fnv32_1_str("") == 0x811c9dc5UL);
  assert(fnv32_1_str("a") == 0x050c5d7eUL);
  assert(fnv32_1_str("b") == 0x050c5d7dUL);
  assert(fnv32_1_str("c") == 0x050c5d7cUL);
  assert(fnv32_1_str("d") == 0x050c5d7bUL);
  assert(fnv32_1_str("e") == 0x050c5d7aUL);
  assert(fnv32_1_str("f") == 0x050c5d79UL);
  assert(fnv32_1_str("fo") == 0x6b772514UL);
  assert(fnv32_1_str("foo") == 0x408f5e13UL);
  assert(fnv32_1_str("foob") == 0xb4b1178bUL);
  assert(fnv32_1_str("fooba") == 0xfdc80fb0UL);
  assert(fnv32_1_str("foobar") == 0x31f0b262UL);
}


/* Bloom filter data structure */
const size_t bloom_bits = 64;
typedef uint64_t bloom_filter_type;
bloom_filter_type bloom_filter[1] = { 0 }; // XXX should calculate the size here

/* Returns the bit in the bloom filter to set/check. */
size_t bloom_bit(char *string) {
  /* Note: a real bloom filter would use multiple bits and multiple hash fns. */
  return fnv32_1_str(string) % bloom_bits;
}

/* Add a value to the bloom filter. */
void bloom_add(char *string) {
  size_t i = bloom_bit(string) / sizeof(bloom_filter_type);
  size_t j = bloom_bit(string) % sizeof(bloom_filter_type);

  bloom_filter[i] |= (1 << j);
}

/* Check if a value might have been seen before. */
bool bloom_check(char *string) {
  size_t i = bloom_bit(string) / sizeof(bloom_filter_type);
  size_t j = bloom_bit(string) % sizeof(bloom_filter_type);

  return (bloom_filter[i] & (1 << j)) != 0;
}

/* Test filter */
void test_bloom_filter() {
  assert(bloom_check("foo") == false);
  bloom_add("foo");
  assert(bloom_check("foo") == true);

  assert(bloom_check("bar") == false); /* assuming foo's hash values != bar's */
  bloom_add("bar");
  assert(bloom_check("bar") == true);
}


int main(void) {
  test_fnv32_1();
  test_bloom_filter();
}