/*! @file       preboot.c
    Copyright 2007 VMware Inc.
    Author: David Elliott
 */
#include "libsaio.h"
#include "preboot.h"

static struct preboot_header *spPrebootHeader = NULL;

//==========================================================================
static int get_ramdisk_info(int biosdev, struct driveInfo *dip)
{
    if(spPrebootHeader == NULL || spPrebootHeader->p_initrd == 0)
        return -1;
    bzero(dip, sizeof(*dip));
    // Only 1 ramdisk for now
    if(biosdev != 0x100)
        return -1;
    if(spPrebootHeader->p_initrd == 0)
        return -1;
    
    dip->biosdev = biosdev;
    dip->uses_ebios = TRUE;
    // dip->no_emulation = FALSE;
    dip->di.params.phys_sectors = spPrebootHeader->initrd_sectors;

    dip->valid = TRUE;
    return 0;
}

//==========================================================================
static int ramdiskReadBytes( int biosdev, unsigned int blkno,
                      unsigned int byteoff,
                      unsigned int byteCount, void * buffer )
{
    if(spPrebootHeader == NULL || spPrebootHeader->p_initrd == 0)
        return -1;
    if(biosdev != 0x100)
        return -1;
    void *p_initrd = (void*)spPrebootHeader->p_initrd;
    bcopy(p_initrd + blkno*512 + byteoff, buffer, byteCount);
    return 0;
}

//==========================================================================
/*! @function findPrebootHeader
    Finds the PREBOOT structure and returns a pointer to it if it is valid.
    It is valid so long as it has the right signature and checksum.  It
    is not guaranteed to contain an initrd.
 */
static struct preboot_header *findPrebootHeader()
{
    struct preboot_header *pPrebootHeader = (void*)PREBOOT_DATA;
    if(memcmp(PREBOOT_SIGNATURE, pPrebootHeader->signature, 8) == 0)
    {
        uint8_t checksum = checksum8(pPrebootHeader, pPrebootHeader->length);
        if(checksum != 0)
        {
            printf("WARNING: Found bad PREBOOT structure\n");
            pPrebootHeader = NULL;
        }
    }
    else
        pPrebootHeader = NULL;
    return pPrebootHeader;
}

//==========================================================================
BVRef scanPrebootVolumes()
{
    struct preboot_header *pPrebootHeader = findPrebootHeader();
    if(pPrebootHeader == NULL)
        return NULL;

    if(pPrebootHeader->p_initrd == 0)
        return NULL;

    // We have a header with an initrd.. use it

    // Install hooks to disk.c code to make the ramdisk available
    p_get_ramdisk_info = get_ramdisk_info;
    p_ramdiskReadBytes = ramdiskReadBytes;
    spPrebootHeader = pPrebootHeader;

    // Scan the disk for the first volume (hopefully the only volume)
    // containing extra extensions.
    int partCount; // unused
    BVRef ramdiskChain = diskScanBootVolumes(0x100, &partCount);
    if(ramdiskChain == NULL)
    {
        printf("Found ramdisk but no partitions in it!");
        // TODO: Check for raw HFS+ image (e.g. no partition map)
        return NULL;
    }

    // We can now access the ramdisk

    return ramdiskChain;
}

//==========================================================================
BVRef selectPrebootVolume(BVRef ramdiskChain)
{
    if(ramdiskChain == NULL)
        return NULL;
    char *path = malloc(4096);
    BVRef curr;
    for(curr = ramdiskChain; curr; curr = curr->next)
    {
        strcpy(path, "rd(0,");
        char partnostr[10];
        // no way.
        if(curr->part_no >= 1000)
            continue;
        sprintf(partnostr, "%d",curr->part_no);
        strcat(path, partnostr);
        strcat(path, ")/Library/Application Support/DarwinBoot/Extra/");
        struct dirstuff *extradir = opendir(path);
        if(extradir == NULL)
            printf("Could not find extra dir which is the whole point of a ramdisk\n");
        else
        {
            // NOTE: Never free'd
            gPrebootExtraDir = malloc(strlen(path)+1);
            strcpy(gPrebootExtraDir, path);
            closedir(extradir);
            // We found a valid volume.. so stop walking the chain.
            break;
        }
    }
    free(path);
    return curr;
}