/*
 * fatfs.c - FATFS file system API implementation.
 *
 * Author    Mohamed Lamine Karaoui (2014,2015)
 *           Alain Greiner (2016,2017)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH 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; version 2.0 of the License.
 *
 * ALMOS-MKH 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 ALMOS-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */


#include <hal_types.h>
#include <hal_special.h>
#include <printk.h>
#include <kmem.h>
#include <ppm.h>
#include <vfs.h>
#include <rpc.h>
#include <mapper.h>
#include <cluster.h>
#include <dev_ioc.h>
#include <fatfs.h>

//////////////////////////////////////////////////////////////////////////////////////////
//          Extern  variables         
//////////////////////////////////////////////////////////////////////////////////////////

extern vfs_ctx_t        fs_context[FS_TYPES_NR];   // allocated in vfs.c file

extern remote_barrier_t global_barrier;            // allocated dans kernel_init.c
 
//////////////////////////////////////////////////////////////////////////////////////////
// FATFS specific functions : these functions cannot be called by the VFS 
//////////////////////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////
inline uint32_t fatfs_lba_from_cluster( fatfs_ctx_t * ctx,
                                        uint32_t      cluster )
{
    return (ctx->cluster_begin_lba + ((cluster - 2) << 3));
}

/////////////////////////////////////////////
error_t fatfs_get_cluster( mapper_t * mapper,
                           uint32_t   first_cluster,
                           uint32_t   searched_page,
                           uint32_t * cluster )
{
    page_t   * current_page_desc;      // pointer on current page descriptor
    uint32_t * current_page_buffer;    // pointer on current page (array of uint32_t)
    uint32_t   current_page_index;     // index of current page in mapper 
    uint32_t   current_page_offset;    // offset of slot in current page
    uint32_t   page_count_in_file;     // index of page in file (index in linked list)
    uint32_t   current_cluster;        // content of current FAT slot

    // compute number of FAT slots per PPM page
    uint32_t slots_per_page = CONFIG_PPM_PAGE_SIZE >> 2;

    // initialize loop variable
    current_page_index  = first_cluster / slots_per_page;
    current_page_offset = first_cluster % slots_per_page;
    page_count_in_file  = 0;

    // scan FAT (i.e. traverse FAT linked list)
    while( page_count_in_file <= searched_page )
    {
        // get pointer on current page descriptor
        current_page_desc = mapper_get_page( mapper , current_page_index );

        if( current_page_desc == NULL ) return EIO;

        // get pointer on buffer for current page
        current_page_buffer = (uint32_t *)ppm_page2base( current_page_desc );

        // get FAT slot content 
        current_cluster = current_page_buffer[current_page_offset];

        // update loop variables
        current_page_index  = current_cluster / slots_per_page;
        current_page_offset = current_cluster % slots_per_page;
        page_count_in_file++;
    }
    
    // return success
    *cluster = current_cluster;
    return 0;

}  // end fatfs_get_cluster()

///////////////////////////////////////////////////////////////////////////////////////
// This static function return an integer record value (one, two, or four bytes) 
// from a memory buffer, taking into account endianness.
///////////////////////////////////////////////////////////////////////////////////////
// @ offset        : first byte of record in buffer.
// @ size          : record length in bytes (1/2/4).
// @ buffer        : pointer on buffer base.
// @ little endian : the most significant byte has the highest address when true.
// @ return the integer value in a 32 bits word.
///////////////////////////////////////////////////////////////////////////////////////
static uint32_t get_record_from_buffer( uint32_t    offset,
                                        uint32_t    size,
                                        uint8_t   * buffer,
                                        uint32_t    little_endian )
{
    uint32_t n;
    uint32_t res  = 0;

    if ( little_endian)
    {
        for( n = size ; n > 0 ; n-- ) res = (res<<8) | buffer[offset+n-1];
    }
    else
    {
        for( n = 0 ; n < size ; n++ ) res = (res<<8) | buffer[offset+n];
    }
    return res;

}  // end get_record_from_buffer()



////////////////////////////////////////////////////////////////////////////////////////
// This function returns the FATFS cluster index of a page identified by its page
// index in the file, using the FAT mapper. It scans the FAT mapper, starting from the
// FATFS cluster index allocated to the first page of the file, until it reaches the 
// searched page. The FAT mapper is automatically updated in case of miss. 
// This function can be called by any thread running in any cluster, as it uses the
// RPC_FATFS_GET_CLUSTER to access the remote FAT mapper if required.
// We use a RPC to scan the FAT because the RPC_FIFO will avoid contention
// in the cluster containing the FAT mapper, and the RPC latency is not critical
// compared to the device access latency.
////////////////////////////////////////////////////////////////////////////////////////
// @ ctx	       : pointer on local FATFS context.
// @ first_cluster : first cluster allocated to a file in FATFS.
// @ page_index    : index of searched page in file (one page occupies one cluster).
// @ cluster_index : [out] pointer on buffer for FATFS cluster index.
// @ return 0 if success / return EIO if a FAT cluster miss cannot be solved.
////////////////////////////////////////////////////////////////////////////////////////
static error_t fatfs_cluster_from_index( fatfs_ctx_t * ctx,
                                         uint32_t      first_cluster,
                                         uint32_t      page_index,
                                         uint32_t    * cluster_index )
{
    uint32_t searched_cluster;   // searched FATFS cluster index
    error_t  error;

    // get extended pointer on FAT mapper
    xptr_t fat_mapper_xp = ctx->fat_mapper_xp;

    // get cluster cxy and local pointer on FAT mapper
    cxy_t      fat_mapper_cxy = GET_CXY( fat_mapper_xp );
    mapper_t * fat_mapper_ptr = (mapper_t *)GET_PTR( fat_mapper_xp );

    if( fat_mapper_cxy == local_cxy )    // FAT mapper is local
    {
        error = fatfs_get_cluster( fat_mapper_ptr,
                                   first_cluster,
                                   page_index,
                                   &searched_cluster );
    }
    else                                 // FAT mapper is remote
    {
        rpc_fatfs_get_cluster_client( fat_mapper_cxy,
                                      fat_mapper_ptr,
                                      first_cluster,
                                      page_index,
                                      &searched_cluster,
                                      &error );
    }
    
    if( error )
    {
        printk("\n[ERROR] in %s : cannot access FAT\n", __FUNCTION__ );
        return error;
    }

    // return success
    *cluster_index = searched_cluster;
    return 0;

}  // end fatfs_cluster_from_index()




///////////////////////////////////////////////////////////////////////////////////////
//          The following functions are called by the VFS.
///////////////////////////////////////////////////////////////////////////////////////


///////////////////
xptr_t fatfs_init()
{
    kmem_req_t    req;
    fatfs_ctx_t * fatfs_ctx;       // local pointer on FATFS context 
    vfs_ctx_t   * vfs_ctx;         // local pointer on VFS context 
    xptr_t        root_inode_xp;   // extended pointer on root inode
    error_t       error;

    // get local pointer on VFS context for FATFS
    vfs_ctx = &fs_context[FS_TYPE_FATFS];

    // get number of kernel instances and extended pointer on global barrier 
    cluster_t * cluster     = LOCAL_CLUSTER;
    uint32_t    nb_clusters = cluster->x_size * cluster->y_size;
    xptr_t      barrier_xp  = XPTR( cluster->io_cxy , &global_barrier );

    ///// step 1 : all clusters allocate memory for FATFS context 

    // allocate memory for FATFS context extension
	req.type    = KMEM_FATFS_CTX;
	req.size    = sizeof(fatfs_ctx_t);
    req.flags   = AF_KERNEL | AF_ZERO;
	fatfs_ctx   = (fatfs_ctx_t *)kmem_alloc( &req );

    if( fatfs_ctx == NULL ) 
    {
        printk("\n[PANIC] in %s : no memory for FATFS context\n", __FUNCTION__ );
        hal_core_sleep();
    }
    
    ///// step 2 : only cluster_0 access device and creates root inode

    if( local_cxy == 0 )
    {
        // create VFS root inode
        error = vfs_inode_create( XPTR_NULL,        // no parent dentry
                                  FS_TYPE_FATFS,
                                  INODE_TYPE_DIR,
                                  0,                // attr
                                  0,                // rights
                                  0,                // uid
                                  0,                // gid
                                  &root_inode_xp );

        assert( (error == 0 ) , __FUNCTION__ , "cannot create VFS root inode" );

        // initialize VFS context / access device to initialize FATFS context
        error = fatfs_ctx_init( vfs_ctx,
                                fatfs_ctx,
                                root_inode_xp );

        // create FATFS root inode
        error = fatfs_inode_create( GET_PTR( root_inode_xp ) , 
                                    fatfs_ctx->root_dir_cluster );

        if( error )
        {
            printk("\n[PANIC] in %s : cannot create FATFS root inode\n", __FUNCTION__ );
            hal_core_sleep();
        }

    }

    //////////////// synchronize all clusters
    remote_barrier( barrier_xp , nb_clusters );

    ///// step 3 : all others clusters initialize both context and extension

    if( local_cxy != 0 )
    {
        // copy VFS context from remote cluster_0 to local cluster
        hal_remote_memcpy( XPTR( local_cxy , vfs_ctx ), 
                           XPTR( 0 , vfs_ctx ),
                           sizeof(vfs_ctx_t) );

        // copy FATFS context from remote cluster_0 to local cluster
        hal_remote_memcpy( XPTR( local_cxy , fatfs_ctx ), 
                           XPTR( 0 , vfs_ctx->extend ) ,
                           sizeof(fatfs_ctx_t) );

        // update extend field in local copy of VFS context
        vfs_ctx->extend = fatfs_ctx;
    }

    return root_inode_xp;

}  // end fatfs_init()

//////////////////////////////////////////////
error_t fatfs_ctx_init( vfs_ctx_t   * vfs_ctx,
                        fatfs_ctx_t * fatfs_ctx,
                        xptr_t        root_inode_xp )
{
    error_t  error;
    uint8_t  buffer[512];    // buffer for boot record

    // make a synchronous access to IOC device to read the boot record from device
    error = dev_ioc_sync_read( buffer , 0 , 1 );
    assert( (error == 0) , __FUNCTION__ , "cannot access FAT boot record" );

    // check sector size from boot record
    uint32_t sector_size = get_record_from_buffer( BPB_BYTSPERSEC , buffer , 1 );
    assert( (sector_size == 512) , __FUNCTION__ , "sector size must be 512 bytes" );

    // check cluster size from boot record
    uint32_t nb_sectors = get_record_from_buffer( BPB_SECPERCLUS , buffer , 1 );
    assert( (nb_sectors == 8) , __FUNCTION__ , "cluster size must be 8 sectors" );

    // check number of FAT copies from boot record
    uint32_t nb_fats = get_record_from_buffer( BPB_NUMFATS , buffer , 1 );
    assert( (nb_fats == 1) , __FUNCTION__ , "number of FAT copies must be 1" );

    // get & check number of sectors in FAT from boot record
    uint32_t fat_sectors = get_record_from_buffer( BPB_FAT32_FATSZ32 , buffer , 1 );
    assert( ((fat_sectors & 0xF) == 0) , __FUNCTION__ , "FAT not multiple of 16 sectors");

    // get and check root cluster from boot record
    uint32_t root_cluster = get_record_from_buffer( BPB_FAT32_ROOTCLUS , buffer , 1 );
    assert( (root_cluster == 2) , __FUNCTION__ , "Root cluster index must be  2");

    // get FAT lba from boot record
    uint32_t fat_lba = get_record_from_buffer( BPB_RSVDSECCNT , buffer , 1 );
    
    // allocate a mapper for the FAT itself
    mapper_t * fat_mapper = mapper_create();
    assert( (fat_mapper != NULL) , __FUNCTION__ , "no memory for FAT mapper" );

    // initialize the FATFS context
    fatfs_ctx->fat_begin_lba         = fat_lba;
    fatfs_ctx->fat_sectors_count     = fat_sectors; 
    fatfs_ctx->bytes_per_sector      = sector_size;
    fatfs_ctx->bytes_per_cluster     = sector_size * nb_sectors;
    fatfs_ctx->cluster_begin_lba     = fat_lba + fat_sectors;
    fatfs_ctx->root_dir_cluster      = 2;
    fatfs_ctx->last_allocated_sector = 0;    // TODO ???
    fatfs_ctx->last_allocated_index  = 0;    // TODO ???
    fatfs_ctx->fat_mapper_xp         = XPTR( local_cxy , fat_mapper );

    // initialize the VFS context
    vfs_ctx->type    = FS_TYPE_FATFS;
    vfs_ctx->attr    = 0;                    // not READ_ONLY / not SYNC
    vfs_ctx->count   = fat_sectors << 10;    // total number of sectors in data region
    vfs_ctx->blksize = 512;                  // number of bytes per sector
    vfs_ctx->root_xp = root_inode_xp;
    vfs_ctx->extend  = fatfs_ctx;

    spinlock_init( &vfs_ctx->lock );

    bitmap_init( vfs_ctx->bitmap , CONFIG_VFS_MAX_INODES );

    return 0;

}  // end fatfs_ctx_init()
 


////////////////////////////////////////////////////
void fatfs_ctx_destroy( struct vfs_ctx_s * vfs_ctx )
{
    kmem_req_t    req;
    fatfs_ctx_t * fatfs_ctx;

    // get pointer on FATFS context extension
    fatfs_ctx = (fatfs_ctx_t *)vfs_ctx->extend;

    req.type = KMEM_FATFS_INODE;
    req.ptr  = fatfs_ctx;
    kmem_free( &req );
}


////////////////////////////////////////////////////
error_t fatfs_inode_create( vfs_inode_t * vfs_inode,
                            uint32_t      first_cluster )
{
    kmem_req_t      req;
    fatfs_inode_t * fatfs_inode;

    // allocate memory for FATFS inode extension
	req.type    = KMEM_FATFS_INODE;
	req.size    = sizeof(fatfs_inode_t);
    req.flags   = AF_KERNEL | AF_ZERO;
	fatfs_inode = (fatfs_inode_t *)kmem_alloc( &req );

    if( fatfs_inode == NULL ) return ENOMEM;

    // link FATFS inode to VFS inode
    vfs_inode->extend = fatfs_inode;

    // initialise FATFS inode 
    fatfs_inode->first_cluster = first_cluster;
 
    return 0;
}

///////////////////////////////////////////////////
void fatfs_inode_destroy( vfs_inode_t * vfs_inode )
{
    kmem_req_t      req;
    fatfs_inode_t * fatfs_inode;

    // get pointer on FATFS inode 
    fatfs_inode = (fatfs_inode_t *)vfs_inode->extend;

    req.type = KMEM_FATFS_INODE;
    req.ptr  = fatfs_inode;
    kmem_free( &req );

	vfs_inode->extend = NULL;
}


////////////////////////////////////////////////
static error_t fatfs_access_page( page_t * page,
                                  bool_t   is_read )
{
    // get memory buffer base address
    uint8_t * buffer = (uint8_t *)ppm_page2base( page );
 
    // get pointer on source mapper and page index from page descriptor
    mapper_t * mapper      = page->mapper;
    uint32_t   page_index  = page->index;

    // get VFS inode pointer from mapper
    vfs_inode_t * vfs_inode = mapper->inode;

    // get FATFS inode pointer for VFS inode
    fatfs_inode_t * fatfs_inode = (fatfs_inode_t *)vfs_inode->extend;

    // get first cluster index from FATFS inode
    uint32_t  first_cluster = fatfs_inode->first_cluster;

    // get FATFS context pointer from FATFS inode
    fatfs_ctx_t * fatfs_ctx = (fatfs_ctx_t *)vfs_inode->ctx->extend;

    // get number of sectors 
    uint32_t count = fatfs_ctx->sectors_per_cluster;

    // compute FATFS_cluster index for the accessed page
    uint32_t cluster = 0;
    error_t  error = fatfs_cluster_from_index( fatfs_ctx,
                                               first_cluster,
                                               page_index,
                                               &cluster );
    if( error ) return EIO;

    // get lba from cluster
    uint32_t lba = fatfs_lba_from_cluster( fatfs_ctx , cluster );

    // access device
    if( is_read ) error = dev_ioc_read ( buffer , lba , count );
    else          error = dev_ioc_write( buffer , lba , count );     

    if( error )
    {
        printk("\n[ERROR] in %s : cannot access IOC device\n", __FUNCTION__ );
        return error;
    } 

    // successful access 
    return 0;
}

////////////////////////////////////////////////
error_t fatfs_write_page( struct page_s * page )
{
    bool_t is_read = false;
    return fatfs_access_page( page , is_read );
}

///////////////////////////////////////////////
error_t fatfs_read_page( struct page_s * page )
{
    bool_t is_read = true;
    return fatfs_access_page( page , is_read );
}

