#define pr_fmt(fmt) "[alloc]: " fmt
//#define DEBUG
#include "alloc.h"
#include "errno.h"
#include "list.h"
#include "math.h"
#include "mem.h"
#include "vga.h"

// Slab will contains object from sizeof(void *) to PAGE_SIZE/2 by pow2
#define SLUB_SIZE (PAGE_SHIFT - 1)
struct slabDesc *slub;

int initSlabDesc(struct slabDesc **desc, size_t size);
static int formatPage(struct slabDesc *desc, size_t size);

int initSlab(void)
{
        uint start = log2(sizeof(void *));
        list_init(slub);
        for (uint i = start; i < SLUB_SIZE; i++) {
                struct slabDesc *slab;
                if (initSlabDesc(&slab, 1U << i))
                        return ENOMEM;
                list_add_tail(slub, slab);
        }
        return 0;
}

int initSlabDesc(struct slabDesc **desc, size_t size)
{
        if (size > PAGE_SIZE)
                return ENOENT;
        paddr_t alloc = allocPhyPage();
        if (alloc == (paddr_t)NULL)
                return ENOMEM;
        if (pageMap((vaddr_t)alloc, alloc, PAGING_MEM_WRITE)) {
                return ENOMEM;
        }
        *desc = (struct slabDesc *)alloc;
        list_singleton(*desc, *desc);
        (*desc)->page   = (vaddr_t)alloc;
        (*desc)->full   = 0;
        (*desc)->freeEl = (char *)(*desc) + sizeof(struct slabDesc);
        (*desc)->size   = size;
        pr_devel("got page %d for size %d first %d", alloc, size, (*desc)->freeEl);
        return formatPage((*desc), size);
}

static int formatPage(struct slabDesc *desc, size_t size)
{
        char *cur = (char *)desc + sizeof(struct slabDesc);
        ulong i;
        for (i = 0; i < ((PAGE_SIZE - sizeof(struct slabDesc)) / size - 1); i++) {
                *((vaddr_t *)cur) = (vaddr_t)cur + size;
                cur += size;
        }
        *((vaddr_t *)cur) = (vaddr_t)NULL;
        pr_devel("last at %d allocated %d\n", cur, i + 1);
        return 0;
}

static void *allocFromSlab(struct slabDesc *slab)
{
        vaddr_t *next = slab->freeEl;
        if (*next == (vaddr_t)NULL) {
                pr_devel("Slab %d full\n", slab);
                slab->full = 1;
        } else {
                slab->freeEl = (void *)(*next);
        }
        return (void *)next;
}

void *malloc(size_t size)
{
        if (size > (1U << SLUB_SIZE)) {
                printf("implement malloc for big size\n");
                return NULL;
        }
        struct slabDesc *slubEntry;
        uint slubIdx = 0;
        list_foreach(slub, slubEntry, slubIdx)
        {
                if(size <= slubEntry->size)
                        break;
        }
        struct slabDesc *slab;
        int slabIdx;
        list_foreach(slubEntry, slab, slabIdx)
        {
                if (!slab->full) {
                        pr_devel("found place in slub %d at idx %d \n", slubIdx, slabIdx);
                        return allocFromSlab(slab);
                }
        }
        if (!list_foreach_early_break(slubEntry, slab, slabIdx)) {
                struct slabDesc *newSlab;
                initSlabDesc(&newSlab, slab->size);
                list_add_head(slubEntry, newSlab);
                return allocFromSlab(newSlab);
        }
        return NULL;
}