#include "../includes/hashtable.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

//Reference https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
//FNV = Fowler–Noll–Vo
#define FNV_OFFSET 0xcbf29ce484222325 //Or 14695981039346656037 in decimal
#define FNV_PRIME 0x100000001b3 //Or 1099511628211 in decimal
#define DEFAULTHASHTABLESIZE 64

Bucket* CreateBucket();
void AddToBucket(char* key, char* text, Bucket* bucket);

HashTable* CreateHashTable(void) {
    HashTable* table = calloc(1, sizeof(HashTable));

    table->Values = calloc(DEFAULTHASHTABLESIZE, sizeof(Bucket*));
    table->Capacity = DEFAULTHASHTABLESIZE;
    
    return table;
}

void AddItemToHashTable(char* key, char* item, HashTable* table) {
    //FNV-1a hash
    unsigned long long hash = FNV_OFFSET;

    for(int i = 0; i < strlen(key); i ++) {
        hash ^= key[i];
        hash *= FNV_PRIME;
    }

    unsigned int index = hash % table->Capacity;

    Bucket* bucket = table->Values[index];

    if (!bucket) table->Values[index] = CreateBucket();

    AddToBucket(key, item, table->Values[index]);
}

char* HashTableBucketLinearScan(char* key, Bucket* bucket) {
    for(int i = 0; i < bucket->Size; i++) {
        BucketKeyPair* pair = bucket->KeyPairs[i];

        if (strcmp(key, pair->Key) == 0) return pair->Value;
    }

    return NULL;
}

char* GetHashTableItem(char* key, HashTable* table) {
    unsigned long long hash = FNV_OFFSET;

    for(int i = 0; i < strlen(key); i ++) {
        hash ^= key[i];
        hash *= FNV_PRIME;
    }

    unsigned int index = hash % table->Capacity;

    Bucket* bucket = table->Values[index];

    if (!bucket) return NULL;

    if (bucket->Size == 1) return bucket->KeyPairs[0]->Value;

    return HashTableBucketLinearScan(key, bucket);
}

Bucket* CreateBucket() {
    Bucket* bucket = calloc(1, sizeof(Bucket));

    bucket->KeyPairs = calloc(16, sizeof(BucketKeyPair*));
    bucket->Capacity = 16;

    return bucket;
}

void AddToBucket(char* key, char* text, Bucket* bucket) {
    BucketKeyPair* keyPair = calloc(1, sizeof(BucketKeyPair));
    keyPair->Key = key;
    keyPair->Value = text;

    bucket->KeyPairs[bucket->Size] = keyPair;

    bucket->Size++;
}

void PrintHashTable(HashTable* table) {
    printf("Capacity %d\nBuckets:\n", table->Capacity);

    for(int i = 0; i < table->Capacity; i++) {
        Bucket* bucket = table->Values[i];

        if (!bucket) continue;

        printf("Bucket %d: \n", i+1);

        for(int j = 0; j < bucket->Size; j++) {
            printf("(%s) '%s'\n", bucket->KeyPairs[j]->Key, bucket->KeyPairs[j]->Value);
        }

        printf("\n");
    }
}