#include "a_station.h"
#include <stdlib.h>
#include <string.h>

struct station* create_station(){
   struct station* station = (struct station*)calloc(1,sizeof(struct station));
   station->tracks = (struct car**)calloc(STATION_SIZE, sizeof(struct car*));
   station->track_count = STATION_SIZE;
   return station;
}


/* djb2 hash function by Dan Bernstein - deterministic and simple */
static unsigned long hash_str(const char *str) {
    unsigned long hash = 5381;
    int c;
    while ((c = (unsigned char)*str++))
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
    return hash;
}

void destroy_station(struct station* station){
    if(!station) return;
    if(station->tracks){
        for(int i = 0; i < station->track_count; ++i){
            struct car* cur = station->tracks[i];
            while(cur){
                struct car* next = cur->next;
                free(cur);
                cur = next;
            }
        }
        free(station->tracks);
    }
    free(station);
}

int select_track(struct station* station, const char* target){
    if(!station || !target) return 0;
    unsigned long h = hash_str(target);
    return (int)(h % (unsigned long)station->track_count);
}

void add_target_capacity(struct station* station,const char* target, int capacity){
    if(!station || !target || capacity == 0) return;
    int idx = select_track(station, target);
    struct car* cur = station->tracks[idx];
    struct car* prev = NULL;
    while(cur){
        if(strncmp(cur->value, target, TARGET_SIZE) == 0){
            cur->capacity += capacity;
            return;
        }
        prev = cur;
        cur = cur->next;
    }
    /* not found -> create new record and append at head for simplicity */
    struct car* node = (struct car*)calloc(1, sizeof(struct car));
    if(!node) return; /* allocation failed */
    strncpy(node->value, target, TARGET_SIZE - 1);
    node->value[TARGET_SIZE-1] = '\0';
    node->capacity = capacity;
    node->next = station->tracks[idx];
    station->tracks[idx] = node;
}

int get_target_capacity(struct station* station,const char* target){
    if(!station || !target) return 0;
    int idx = select_track(station, target);
    struct car* cur = station->tracks[idx];
    while(cur){
        if(strncmp(cur->value, target, TARGET_SIZE) == 0){
            return cur->capacity;
        }
        cur = cur->next;
    }
    return 0;
}

int count_targets(struct station* station){
    if(!station) return 0;
    int count = 0;
    for(int i = 0; i < station->track_count; ++i){
        struct car* cur = station->tracks[i];
        while(cur){
            count++;
            cur = cur->next;
        }
    }
    return count;
}

int count_capacity(struct station* station){
    if(!station) return 0;
    int total = 0;
    for(int i = 0; i < station->track_count; ++i){
        struct car* cur = station->tracks[i];
        while(cur){
            total += cur->capacity;
            cur = cur->next;
        }
    }
    return total;
}