//
// Created by rick on 23-02-21.
//

#include <libc/kprintf.h>
#include <tasks/task.h>
#include "malloc.h"
#include "pmm.h"

#define MALLOC_TYPE_FREE 0
#define MALLOC_TYPE_USED 1

int malloc_entries = 0;
int malloc_used = 0;

typedef struct malloc_map {
    struct malloc_map *next;
    struct malloc_map *prev;
    uint32_t size;
    int type;
} malloc_map;

malloc_map *first_malloc_entry;

void malloc_init() {
    first_malloc_entry = pmm_get_pages(16);
    first_malloc_entry->next = first_malloc_entry;
    first_malloc_entry->prev = first_malloc_entry;
    first_malloc_entry->size = PAGE_SIZE * 16;
    first_malloc_entry->type = MALLOC_TYPE_FREE;
    malloc_entries++;
}

void split_malloc_map(malloc_map *entry, unsigned int size) {
    malloc_entries++;
    malloc_map *new_entry = entry + sizeof(malloc_map) + size;
    new_entry->size = entry->size - size - sizeof(malloc_map);
    new_entry->next = entry->next;
    new_entry->prev = entry;
    new_entry->type = MALLOC_TYPE_FREE;
    entry->next->prev = new_entry;
    entry->next = new_entry;
    entry->size = size;
}

void *malloc(size_t size) {
    // todo replace this horrible mess!
    // this lacks any page alignment and what so ever
    void* result = NULL;
    task_lock_acquire();
    malloc_map *current_map = first_malloc_entry;
    // iterate through maps
    do {
        if (current_map->type == MALLOC_TYPE_USED) {
            goto malloc_find_next;
        }
        if ((unsigned int) current_map->size < size) {
            goto malloc_find_next;
        }
        if ((unsigned int) current_map->size > (size + sizeof(malloc_map))) {
            // big enough to split
            split_malloc_map(current_map, size);
        }
        malloc_used++;
        current_map->type = MALLOC_TYPE_USED;
        result = ((void *) current_map) + sizeof(malloc_map);
        break;

        malloc_find_next:
        current_map = current_map->next;
    } while (current_map != first_malloc_entry);
    task_lock_free();
    return result;
}

void free(void *mem) {
    if (mem == NULL) {
        return;
    }
    malloc_used--;
    malloc_map *map = (mem - sizeof(malloc_map));
    map->type = MALLOC_TYPE_FREE;
};


void print_malloc_info() {
    printf("Malloc avail entries: %d\n"
           "Malloc used entries: %d\n", malloc_entries, malloc_used);
}