/*                 _,.---._    .-._        .--.-. ,--.--------.
 *   _,..---._   ,-.' , -  `. /==/ \  .-._/==/  //==/,  -   , -\
 * /==/,   -  \ /==/_,  ,  - \|==|, \/ /, |==\ -\\==\.-.  - ,-./
 * |==|   _   _\==|   .=.     |==|-  \|  | \==\- \`--`\==\- \
 * |==|  .=.   |==|_ : ;=:  - |==| ,  | -|  `--`-'     \==\_ \
 * |==|,|   | -|==| , '='     |==| -   _ |             |==|- |
 * |==|  '='   /\==\ -    ,_ /|==|  /\ , |             |==|, |
 * |==|-,   _`/  '.='. -   .' /==/, | |- |             /==/ -/
 * `-.`.____.'     `--`--''   `--`./  `--`             `--`--`
 *                    _ __    ,---.      .-._         .=-.-.  _,.----.
 *                 .-`.' ,`..--.'  \    /==/ \  .-._ /==/_ /.' .' -   \
 *                /==/, -   \==\-/\ \   |==|, \/ /, /==|, |/==/  ,  ,-'
 *               |==| _ .=. /==/-|_\ |  |==|-  \|  ||==|  ||==|-   |  .
 *               |==| , '=',\==\,   - \ |==| ,  | -||==|- ||==|_   `-' \
 *               |==|-  '..'/==/ -   ,| |==| -   _ ||==| ,||==|   _  , |
 *               |==|,  |  /==/-  /\ - \|==|  /\ , ||==|- |\==\.       /
 *               /==/ - |  \==\ _.\=\.-'/==/, | |- |/==/. / `-.`.___.-'
 *               `--`---'   `--`        `--`./  `--``--`-`
 *
 *	@(#)Copyright (c) 2023, Nathan D. Fisher.
 *
 *      This is free software.  It comes with NO WARRANTY.
 *      Permission to use, modify and distribute this source code
 *      is granted subject to the following conditions.
 *      1/ that the above copyright notice and this notice
 *      are preserved in all copies and that due credit be given
 *      to the author.
 *      2/ that any changes to this code are clearly commented
 *      as such so that the author does not get blamed for bugs
 *      other than his own.
 */

#include "haggis_private.h"

#include <limits.h>        // PATH_MAX
#include <stdio.h>
#include <stdlib.h>        // calloc, free
#include <string.h>        // strndup

#define FNV64_OFFSET_BASIS 14695981039346656037u
#define FNV64_PRIME 1099511628211u

uint64_t hash_fnv1a_64(uint8_t *key, size_t len) {
    int i;
    uint64_t hash = FNV64_OFFSET_BASIS;

    for (i = 0; i < len; i++) {
        hash = hash ^ *key;
        hash = hash * FNV64_PRIME;
        key++;
    }
    return hash;
}

uint64_t hash_str_fnv1a_64(char * s) {
    uint64_t hash = FNV64_OFFSET_BASIS;

    while (*s != '\0') {
        hash = hash ^ *s;
        hash = hash * FNV64_PRIME;
        s++;
    }
    return hash;
}

haggis_bucket* haggis_bucket_init(ino_t inode, uint64_t hash, char * path) {
    haggis_bucket *bucket;

    bucket = calloc(1, sizeof(haggis_bucket));
    if (bucket == NULL) return NULL;
    bucket->key.val = inode;
    bucket->hash = hash;
    bucket->path = path;
    bucket->next = NULL;
    return bucket;
}

void haggis_bucket_deinit(haggis_bucket *nod) {
    if (nod->path != NULL)
        free(nod->path);
    free(nod);
}

char* haggis_bucket_search_append(haggis_bucket *head, haggis_bucket *tail) {
    char* target;

    while (head->next != NULL) {
        if (head->key.val == tail->key.val) {
            target = strndup(head->path, PATH_MAX - 1);
            return target;
        }
        head = head->next;
    }
    head->next = tail;
    return NULL;
}

haggis_linkmap* haggis_linkmap_init() {
    haggis_linkmap *map;

    map = calloc(1, sizeof(haggis_linkmap));
    if (map == NULL)
        return NULL;
    map->buckets = calloc(HAGGIS_BUCKETS_BASE, sizeof(size_t));
    if (map->buckets == NULL) {
        free(map);
        return NULL;
    }
    map->capacity = HAGGIS_BUCKETS_BASE;
    return map;
}

void haggis_linkmap_deinit(haggis_linkmap *map) {
    int i;

    for (i = 0; i < map->capacity; i++) {
        if (map->buckets[i].next != NULL) {
            haggis_bucket_deinit(map->buckets[i].next);
        }
    }
    free(map->buckets);
    free(map);
}

int haggis_linkmap_expand(haggis_linkmap *map) {
    haggis_bucket *buckets_new;
    haggis_bucket *buckets_old;
    size_t i, hash, idx;

    buckets_new = calloc(map->capacity + HAGGIS_BUCKETS_BASE, sizeof(haggis_bucket));
    if (buckets_new == NULL)
        return 2;
    for (i = 0; i < map->capacity; i++) {
        if (map->buckets[i].key.val != 0) {
            hash = hash_fnv1a_64(&map->buckets[i].key.bytes[0], sizeof(ino_t));
            map ->capacity += HAGGIS_BUCKETS_BASE;
            idx = map->capacity % hash;
            buckets_new[idx] = map->buckets[i];
        }
    }
    buckets_old = map->buckets;
    map->buckets = buckets_new;
    free(buckets_old);
    map->capacity += HAGGIS_BUCKETS_BASE;
    return 0;
}

char* haggis_linkmap_get_or_add(haggis_linkmap *map, ino_t inode, char * path) {
    union {
        ino_t val;
        u8 bytes[sizeof(ino_t)];
    } key;
    char * target = "";
    size_t idx, hash;
    haggis_bucket *b;

    pthread_mutex_lock(&map->mutex);
    if (map->len >= map->capacity)
        haggis_linkmap_expand(map);
    key.val = inode;
    hash = hash_fnv1a_64(key.bytes, sizeof(ino_t));
    idx = map->capacity % hash;
    if (map->buckets[idx].key.val == inode) {
        target = strndup(target, PATH_MAX - 1);
    } else if (map->buckets[idx].key.val == 0) {
        map->buckets[idx].key.val = inode;
        map->buckets[idx].hash = hash;
        map->buckets[idx].path = path;
        map->len++;
    } else {
        b = haggis_bucket_init(key.val, hash, path);
        if (b == NULL) return NULL;
        target = haggis_bucket_search_append(&map->buckets[idx], b);
    }
    pthread_mutex_unlock(&map->mutex);
    return target;
}