//
// Created by rick on 22-04-20.
//

#include <types.h>
#include <mem/mem.h>
#include <libc/kprintf.h>

#define MEMMAP_ENTRIES 16

#define MMAP_TYPE_UNDEFINED         0
#define MMAP_TYPE_AVAILABLE         1
#define MMAP_TYPE_RESERVED          2
#define MMAP_TYPE_ACPI_RECLAIMABLE  3
#define MMAP_TYPE_NVS               4
#define MMAP_TYPE_BADRAM            5
#define MMAP_TYPE_KERNEL            6
#define MMAP_TYPE_MALLOC            7

#define MALLOC_TYPE_FREE 0
#define MALLOC_TYPE_USED 1

#define kilobyte (1024)
//#define kernel_start (one_meg)
#define kernel_size (32 * kilobyte)
#define kernel_end (kernel_start + kernel_size)
extern void *kernel_start;
//extern void *kernel_end;

typedef struct {
    void *address;
    u32 length;
    u32 type;
} __attribute((packed)) mmap_entry;

int malloc_entries = 0;
int malloc_used = 0;

int last_memmap_entry = 0;
mmap_entry memmap[MEMMAP_ENTRIES] = {
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
};

typedef struct malloc_map {
    struct malloc_map *next;
    struct malloc_map *pref;
    u32 size;
    int type;
} malloc_map;

void use_mmap_entry(struct multiboot_mmap_entry *entry) {
    mmap_entry *mm_entry = &memmap[last_memmap_entry++];
    mm_entry->address = (void *) entry->addr;
    mm_entry->length = entry->len;
    mm_entry->type = entry->type;
    if (last_memmap_entry == 1) {
        // not using first map entry for now
        return;
    }
    // check if the entry overlaps with the kernel address space
    if (kernel_start >= mm_entry->address && kernel_start <= mm_entry->address + mm_entry->length) {
        // todo make this something proper
        struct multiboot_mmap_entry extra_entry;
        extra_entry.size = entry->size;
        extra_entry.type = entry->type;
        extra_entry.addr = entry->addr + kernel_size;
        extra_entry.len = entry->size - kernel_size;
        use_mmap_entry(&extra_entry);

        mm_entry->length = kernel_size;
        mm_entry->type = MMAP_TYPE_KERNEL;
    }
    if (mm_entry->type == MMAP_TYPE_AVAILABLE && (unsigned int) mm_entry->length > sizeof(malloc_map)) {
        mm_entry->type = MMAP_TYPE_MALLOC;
        malloc_map *map = (malloc_map *) mm_entry->address;
        map->type = MALLOC_TYPE_FREE;
        map->size = mm_entry->length - sizeof(malloc_map);
        map->pref = map;
        map->next = map;
        malloc_entries++;
    }
}

void init_mmap_multiboot(struct multiboot_mmap_entry *entries, u32 count) {
    for (u32 i = 0; i < count; ++i) {
        use_mmap_entry(&entries[i]);
    }
}

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->pref = entry;
    new_entry->type = MALLOC_TYPE_FREE;
    entry->next->pref = new_entry;
    entry->next = new_entry;
    entry->size = size;
}

void *malloc(unsigned int size) {
    // todo replace this horrible mess!
    // this lacks any page alignment and what so ever
    for (int i = 0; i < MEMMAP_ENTRIES; ++i) {
        if (memmap[i].type != MMAP_TYPE_MALLOC) {
            continue;
        }
        // get first first_map of address
        malloc_map *first_map = (malloc_map *) memmap[i].address;
        malloc_map *current_map = first_map;
        // 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;
            return ((void *) current_map) + sizeof(malloc_map);

            malloc_find_next:
            current_map = current_map->next;
        } while (current_map != first_map);
    }
    return NULL;
}

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);
}


void print_mmap_info() {
    for (int i = 0; i < 16; ++i) {
        if (memmap[i].type == 0) {
            break;
        }
        printf("Idx: %d\n"
               "Address: %8x\n"
               "Length:  %8x\n"
               "Type: %d\n\n", i, memmap[i].address, memmap[i].length, memmap[i].type);
    }
}