//#define LOG_LOCAL_LEVEL ESP_LOG_DEBUG

#include <rom/queue.h>
#include <malloc.h>
#include <assert.h>
#include <esp_log.h>
#include <esp_err.h>
#include <string.h>
#include "httpd_utils/session_kvmap.h"

static const char *TAG = "sess_kvmap";

// this struct is opaque, a stub like this is sufficient for the head pointer.
struct sess_kv_entry;

/** Session head structure, dynamically allocated */
SLIST_HEAD(sess_kv_map, sess_kv_entry);

struct sess_kv_entry {
    SLIST_ENTRY(sess_kv_entry) link;
    char key[SESS_KVMAP_KEY_LEN];
    void *value;
    sess_kv_free_func_t free_fn;
};

struct sess_kv_map *sess_kv_map_alloc(void)
{
    ESP_LOGD(TAG, "kv store alloc");
    struct sess_kv_map *map = malloc(sizeof(struct sess_kv_map));
    assert(map);
    SLIST_INIT(map);
    return map;
}

void sess_kv_map_free(void *head_v)
{
    struct sess_kv_map* head = head_v;

    ESP_LOGD(TAG, "kv store free");
    assert(head);
    struct sess_kv_entry *item, *tmp;
    SLIST_FOREACH_SAFE(item, head, link, tmp) {
        if (item->free_fn) {
            item->free_fn(item->value);
            free(item);
        }
    }
    free(head);
}


void * sess_kv_map_get(struct sess_kv_map *head, const char *key)
{
    assert(head);
    assert(key);
    ESP_LOGD(TAG, "kv store get %s", key);

    struct sess_kv_entry *item;
    SLIST_FOREACH(item, head, link) {
        if (0==strcmp(item->key, key)) {
            ESP_LOGD(TAG, "got ok");
            return item->value;
        }
    }

    ESP_LOGD(TAG, "not found in store");
    return NULL;
}

void * sess_kv_map_take(struct sess_kv_map *head, const char *key)
{
    assert(head);
    assert(key);
    ESP_LOGD(TAG, "kv store take %s", key);

    struct sess_kv_entry *item;
    SLIST_FOREACH(item, head, link) {
        if (0==strcmp(item->key, key)) {
            item->key[0] = 0;
            item->free_fn = NULL;
            ESP_LOGD(TAG, "taken ok");
            return item->value;
        }
    }

    ESP_LOGD(TAG, "not found in store");
    return NULL;
}

esp_err_t sess_kv_map_remove(struct sess_kv_map *head, const char *key)
{
    assert(head);
    assert(key);
    ESP_LOGD(TAG, "kv store remove %s", key);

    struct sess_kv_entry *item;
    SLIST_FOREACH(item, head, link) {
        if (0==strcmp(item->key, key)) {
            if (item->free_fn) {
                item->free_fn(item->value);
            }
            item->key[0] = 0;
            item->value = NULL;
            item->free_fn = NULL;
            return ESP_OK;
        }
    }

    ESP_LOGD(TAG, "couldn't remove, not found: %s", key);
    return ESP_ERR_NOT_FOUND;
}


esp_err_t sess_kv_map_set(struct sess_kv_map *head, const char *key, void *value, sess_kv_free_func_t free_fn)
{
    assert(head);
    assert(key);
    ESP_LOGD(TAG, "kv set value for key %s", key);

    size_t key_len = strlen(key);
    if (key_len > SESS_KVMAP_KEY_LEN-1) {
        ESP_LOGE(TAG, "Key too long: %s", key);
        // discard illegal key
        return ESP_FAIL;
    }

    if (key_len == 0) {
        ESP_LOGE(TAG, "Key too short: \"%s\"", key);
        // discard illegal key
        return ESP_FAIL;
    }

    struct sess_kv_entry *item = NULL;
    struct sess_kv_entry *empty_item = NULL; // found item with no content
    SLIST_FOREACH(item, head, link) {
        ESP_LOGD(TAG, "test item with key %s, ptr %p > %p", item->key, item, item->link.sle_next);
        if (0 == item->key[0]) {
            ESP_LOGD(TAG, "found an empty slot");
            empty_item = item;
        }
        else if (0==strcmp(item->key, key)) {
            ESP_LOGD(TAG, "old value replaced");
            if (item->free_fn) {
                item->free_fn(item->value);
            }
            item->value = value;
            item->free_fn = free_fn;
            return ESP_OK;
        } else {
            ESP_LOGD(TAG, "skip this one");
        }
    }

    struct sess_kv_entry *new_item = NULL;

    // insert new or reuse an empty item
    if (empty_item) {
        new_item = empty_item;
        ESP_LOGD(TAG, "empty item reused (%p)", new_item);
    } else {
        ESP_LOGD(TAG, "alloc new item");
        // key not found, add a new entry.
        new_item = malloc(sizeof(struct sess_kv_entry));
        if (!new_item) {
            ESP_LOGE(TAG, "New entry alloc failed");
            return ESP_ERR_NO_MEM;
        }
    }

    strcpy(new_item->key, key);
    new_item->free_fn = free_fn;
    new_item->value = value;

    if (!empty_item) {
        ESP_LOGD(TAG, "insert new item into list");
        // this item was malloc'd
        SLIST_INSERT_HEAD(head, new_item, link);
    }

    return ESP_OK;
}