//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:         Mapping and checking memory related functions               //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <kernel/mm.h>
#include <kernel/term.h>
#include <kernel/multiboot.h>


MemoryMap_t memoryMap = { 0 };


//
// Initilization of the memory map, and computation of the available ram size
//
error_t MmInitMemoryMap(void)
{
    multiboot_memory_map_t *currentEntry;
    multiboot_memory_map_t *mapEnd;
    uint i = 0;

    // sanity checks
    if (!BtGetBootInfo(memory).memValid && BtGetBootInfo(memory).mapValid)
        return ENXIO;

    if ((BtGetBootInfo(memory).upMemory / (MB/KB)) <= MINIMUM_RAM_SIZE)
        return ENOMEM;

// Ok then we can work ------------------------------------------------------ //

    // the memory map provided by GRUB via the BIOS
    currentEntry = (multiboot_memory_map_t*)BtGetBootInfo(memory).mapAddr;
    // End address of the map
    mapEnd = (multiboot_memory_map_t*)
             ((ullong)currentEntry +  (ullong)BtGetBootInfo(memory).mapLength);

    // fill the map
    while (currentEntry < mapEnd) {
        // memory zone address
        memoryMap.entry[i].addr = (void*)( (ullong)currentEntry->addr_low +
                                          (((ullong)currentEntry->addr_high) << 32 ));
        // memory zone size in bytes
        memoryMap.entry[i].length = (ullong)currentEntry->len_low +
                                          (((ullong)currentEntry->len_high) << 32);
        // memory availability
        memoryMap.entry[i].type = (uint)currentEntry->type;
        // Adding the size to the size (yup)
        memoryMap.length++;
        // moving up !
        currentEntry = (multiboot_memory_map_t*) ((ullong)currentEntry +
                                          currentEntry->size + sizeof(currentEntry->size));
        i++;
    }

    DebugLog("[InitMemoryMap] %d entries detected in the memory map\n",
             memoryMap.length);

    // compute the free ram size
    for (i = 0; i < memoryMap.length; i++) {
        if (memoryMap.entry[i].type == AVAILABLE_ZONE) {
            memoryMap.freeRamSize += memoryMap.entry[i].length;
        } else {
            memoryMap.nonfreeRamSize += memoryMap.entry[i].length;
        }
    }

    // Trully strange if it happens...
    if (memoryMap.freeRamSize < MINIMUM_RAM_SIZE)
        return ENOMEM;

    KernLog("[InitMemoryMap] Available Ram Size : %u Mio, Used Ram Size : %u Kio\n",
            memoryMap.freeRamSize / MB, memoryMap.nonfreeRamSize / KB);
    KernLog("[InitMemoryMap] Physical Ram Size : %d Mio\n\n",
            (memoryMap.freeRamSize + memoryMap.nonfreeRamSize) / MB);

    return EOK;
}

size_t MmGetAvailZoneSize(void *start) {
    uint i;

    // Because the kernel is the kernel
    if (start < BtGetBootInfo(btldr).kernelEndAddr)
        return 0;

    // Search the zone where the start address is
    for (i = 0; i < memoryMap.length; i++) {
        // if the address is in an available zone, we can return the length
        if (
                memoryMap.entry[i].type == AVAILABLE_ZONE &&
                (ullong)start >= (ullong)memoryMap.entry[i].addr &&
                (ullong)start <  ((ullong)memoryMap.entry[i].addr +
                           (ullong)memoryMap.entry[i].length)
            ) {
            return (size_t)((ullong)memoryMap.entry[i].length - (ullong)start);
        }
    }

    // If there is no zone, we return a 0 size
    return 0;
}

void *MmGetFirstAvailZone(void *start) {
    uint i;
    void *current = 0;

    // Because the kernel is the kernel
    if ((ullong)start < (ullong)BtGetBootInfo(btldr).kernelEndAddr) {
        return GetFirstAvailZone(BtGetBootInfo(btldr).kernelEndAddr);
    }

    // Search the zone where the start address is
    for (i = 0; i < memoryMap.length; i++) {
        // if the address is in an available zone, we can return the start address
        if (
                memoryMap.entry[i].type == AVAILABLE_ZONE &&
                (ullong)start >= (ullong)memoryMap.entry[i].addr &&
                (ullong)start <  ((ullong)memoryMap.entry[i].addr +
                           (ullong)memoryMap.entry[i].length)
           ) {
            current = start;
            break;
        }
    }

    if (current)
        return current;

    // Search the first zone from start
    for (i = 0; i < memoryMap.length; i++) {
        // Return the first zone that is after start
        if (
                memoryMap.entry[i].type == AVAILABLE_ZONE &&
                (ullong)start <= (ullong)memoryMap.entry[i].addr
           ) {
            current = memoryMap.entry[i].addr;
            break;
        }
    }

    return current;
}