#ifndef LSFS_DISK_CONTROLLER_H
#define LSFS_DISK_CONTROLLER_H

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <time.h>
#include <unistd.h>

#include "lsfs_string.h"

typedef struct Directory_Table Directory_Table;
typedef struct struct_table_entry struct_table_entry;
typedef struct struct_partition_control partition_control;
typedef struct struct_partition_control partition_control;
typedef struct File_System_Control_Information FSCI;
typedef struct meta_information_format mif;
typedef struct tag_record tag_record;
typedef struct lsfs_file lsfs_file;
typedef enum Table_Entry_Kind Table_Entry_Kind;

typedef uint64_t lsfs_sector_offset;
typedef lsfs_sector_offset lsfs_file_id;

//typedef uint64_t sector_index;
static FILE* disk;
static partition_control p_control;

int create_file_system();
int lsfs_disk_create_entry(const char* path, Table_Entry_Kind entry_kind);
int lsfs_disk_getattr(lsfs_file* find_file, const char *path);
int lsfs_disk_delete_file(lsfs_file_id file_id);
int get_free_sectors_table();
int get_free_sectors(int num_sectors_needed, lsfs_sector_offset* output_array);
int lsfs_disk_read_data_from_file(lsfs_file* file, int buffer_size, void* buffer_for_data);
int lsfs_disk_write_data_to_file(lsfs_file* file, int data_length, char *data);
int lsfs_disk_rename_file(lsfs_file* file, const char* new_filename);
int lsfs_disk_load_disk();
int write_data_to_disk(lsfs_sector_offset at_sector, uint32_t file_block_size, void* data_to_write);
int read_data_from_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_buffer);
int write_data_to_disk_off(lsfs_sector_offset index, void* data_to_write, int offset);
int save_modified_file_information(lsfs_file* file);

#define SECTOR_SIZE 512
#define NUMBER_OF_MBR_PARTITIONS 4
#define DEFAULT_FILE_SIZE 4 // This is in sectors
#define DEFAULT_TABLE_SIZE 10 
#define NUM_DATA_POINTERS 28 

typedef enum Table_Entry_Kind
{
    // These are specific values since, is has to corrospond to the implementation in assembly
    ENTRY_EMPTY = 0,
    ENTRY_FILE = 1,
    ENTRY_DIRECTORY = 2,
} Table_Entry_Kind;

typedef struct Partition_Entry
{
    uint8_t  active_falg; // This has value 0x80 if it is a bootable partition / it is an active partition. 
    uint8_t  CHS_start_addr[3]; // [0] = H, [1] = S, [2] = C 
    uint8_t  partition_type; // This has a value such that one can idenfity which file system the partition is. 
    uint8_t  CHS_last_addr[3]; // [0] = H, [1] = S, [2] = C
    uint32_t LBA_abs_first_sector;
    uint32_t number_of_sectors;

} __attribute__((packed)) Partition_Entry;

typedef struct Master_Boot_record 
{
    uint8_t            offset_on_disk[446]; // The code for the bootloader 
    Partition_Entry    partitions[4];
    uint8_t    master_tag_records[2]; // Signature
} __attribute__((packed)) Master_Boot_record;

typedef struct struct_table_entry 
{
    char            filename[256]; 
    lsfs_file_id    file_id;
    uint64_t        file_size;
    mif*            ext_file_data;
    uint32_t        file_block_size;    // This tells how many block there are allocated for the specific file. eg. we read this amount of bloks for the file.    
    uint8_t         entry_kind;
    uint8_t         extra_control_bits1;
    uint8_t         extra_control_bits2;
    uint8_t         extra_control_bits3;
    lsfs_sector_offset data_pointer[NUM_DATA_POINTERS]; // if it is a directory, the first pointer will be to the next table. 
} __attribute__((packed)) table_entry; 

typedef struct Directory_Table 
{
    struct_table_entry entries[10];

} __attribute__((packed)) Directory_Table; 

typedef struct File_System_Control_Information 
{
    char        filesyste_information[256];
    uint64_t    master_table_index;
    uint64_t    this_partition_offset_on_disk;
    uint64_t    next_free_sector;
    uint64_t    next_uniqe_id; // both files and directories gets this. 
    uint64_t    next_sector_reuse_pointer;
    uint64_t    last_sector_index_on_partition;
    uint64_t    maximum_sectors_on_disk;
    uint64_t    sectors_size_on_disk;
    uint64_t    not_used[24];

} __attribute__((packed)) FSCI;

typedef struct struct_partition_control
{
    FSCI                 fsci;
    Directory_Table      master_table;
} __attribute__((packed)) partition_control;



typedef struct meta_information_format {
    char             filename[246]; // remeber that the 246 bytes has to be a /0 terminator.. 
    uint32_t         owner_id;
    lsfs_file_id     tags[32];
    uint64_t         file_size;
    uint32_t         control_bits;
    /* not pressent - Permission key table 64 bytes sha-265 pr. key*/ 
    uint64_t         creation_date;
    uint64_t         last_modification_data;
    uint64_t         last_access_date;
    /*
     *  256 first pointers in direct mapping to data
     *  94 next pointers is a pointer 
     *  94 next pointers to pointers to data
     */
    lsfs_sector_offset   one_level_pointer_data[NUM_DATA_POINTERS];
    lsfs_sector_offset   two_level_pointer_data[94];
    lsfs_sector_offset   three_level_pointer_data[94]; 

} __attribute__((packed)) mif;


typedef struct tag_record {
    /* SIZE 16 bytes */
    lsfs_file_id    mif_record;
    struct {
        uint64_t is_filename : 1;    
    } control_bits;

} __attribute__((packed)) tag_record;

typedef struct lsfs_file {
    lsfs_file_id file_id;
    lsfs_sector_offset table_entry_pointer;
    Table_Entry_Kind entry_kind;
    char* filename;
    uint32_t owner_id;
    uint64_t size;
    uint64_t creation_date; 
    uint64_t access_time;
    uint64_t modification_time;
    uint32_t file_block_size;
    lsfs_sector_offset *data;
} lsfs_file;


int lsfs_disk_getattr(lsfs_file* find_file, const char* path) {
    int i = 0;
    int found = 0;
    while((p_control.master_table.entries[i].filename[0]) != 0 && !found) {
        if(strcmp( (path + 1 ), p_control.master_table.entries[i].filename ) == 0) {
            time_t current_time;
            time ( &current_time );

            find_file->file_id = p_control.master_table.entries[i].file_id;
            find_file->entry_kind = p_control.master_table.entries[i].entry_kind;
            find_file->table_entry_pointer = i;
            find_file->filename = p_control.master_table.entries[i].filename;
            find_file->owner_id = getuid();
            find_file->size = p_control.master_table.entries[i].file_size; // p_control.master_table.entries[i].data_pointer[0]; //;
            find_file->creation_date = (uint64_t) current_time;
            find_file->access_time = (uint64_t) current_time;
            find_file->modification_time = (uint64_t) current_time;
            find_file->data = p_control.master_table.entries[i].data_pointer;
            find_file->file_block_size = 1; // TODO: should be loaded from disk.
            found = 1;
        }
        i++;
    }
    return found;
}



int lsfs_disk_read_data_from_file(lsfs_file *file, int buffer_size, void* buffer_for_data) {
    // TODO some offset, to tell where in the file we want to write

    int return_val = 0;

    for (int i = 0; i < NUM_DATA_POINTERS; ++i) {
        if(file->data[i] == 0) {
            break;
        }
        return_val += read_data_from_disk(file->data[i], file->file_block_size, buffer_for_data + (SECTOR_SIZE * i));
    }

    //time_t current_time;
    //time ( &current_time );

    //mif_record->last_access_date = (uint64_t) current_time;
    //write_data_to_disk(file_id, mif_record);
    //free(mif_record); 
    return return_val;
}

static inline time_t lsfs_disk_update_timestamps(lsfs_file *file) {
    return file->modification_time = file->access_time = time(NULL);
}

#define lsfs_num_sectors_for_size(x) (((x)+SECTOR_SIZE-1)&~(SECTOR_SIZE-1))

int lsfs_disk_write_data_to_file(lsfs_file *file, int data_length, char *data) {
    int written;
    int amount_written = data_length;

    lsfs_sector_offset current_sector = file->size / SECTOR_SIZE;
    unsigned int offset_in_sector = file->size % SECTOR_SIZE;

    char *tmp_buffer = calloc(file->file_block_size, SECTOR_SIZE);
    assert(tmp_buffer);

    read_data_from_disk(file->data[current_sector], file->file_block_size, tmp_buffer); 

    memcpy(tmp_buffer + offset_in_sector, data, SECTOR_SIZE-offset_in_sector);
    data_length -= SECTOR_SIZE-offset_in_sector;

    if (data_length < 0) {
        data_length = 0;
    }

    for (;;) {
        assert(current_sector <= NUM_DATA_POINTERS);
        written = written + write_data_to_disk(p_control.master_table.entries[file->file_id].data_pointer[current_sector], 4, tmp_buffer);
        if (data_length <= 0) break;

        data += SECTOR_SIZE;
        if (data_length >= SECTOR_SIZE) {
            memcpy(tmp_buffer, data, SECTOR_SIZE);
            data_length -= SECTOR_SIZE;
        }
        else {
            memset(tmp_buffer, 0, SECTOR_SIZE);
            memcpy(tmp_buffer, data, data_length);
            data_length = 0;
        }
    }

    amount_written -= data_length;

    free(tmp_buffer);
    
    //lsfs_disk_update_timestamps(&mif_record);
    file->size += amount_written; // update file size
    save_modified_file_information(file);
    //write_data_to_disk(file->file_id, 4, &p_control.master_table[file->file_id]);
    return amount_written;
}

time_t lsfs_disk_truncate_file(lsfs_file *file, off_t offset) {
    //mif file_mif;
    //read_data_from_disk(file_id, &file_mif);
    
    time_t result = lsfs_disk_update_timestamps(file);
    file->size = (int) offset; // p_control.master_table.entries[i].data_pointer[0]; //;

    save_modified_file_information(file);
    //write_data_to_disk(file->file_id, 4, NULL);
    return result;
}

int lsfs_disk_rename_file(lsfs_file* file, const char* new_filename) {

    memset(file->filename, 0, 256);
    sprintf(file->filename, "%s", new_filename); 

    time_t current_time;
    time ( &current_time );

    file->access_time = (uint64_t) current_time;
    file->modification_time = (uint64_t) current_time;

    save_modified_file_information(file);

    return 1;
}

int lsfs_disk_delete_file(lsfs_file_id file_id) {
    mif* mif_record = calloc(1, SECTOR_SIZE);
    read_data_from_disk(file_id, 1, mif_record);

  
    // TODO Delete/free all data sectors. 
    // Delete/free the mif record sector.  

    free(mif_record); 
    return 1;
}

int get_free_sectors_table() {
    // We need DEFAULT_TABLE_SIZE sectors straight contigious for a table
    // Otherwise the file system cannot make a new table. 
    // We return the offset where the table is starting. 
    // If we cannot assing DEFAULT_TABLE_SIZE sectors, we report errror. 
    
    int return_index = p_control.fsci.next_free_sector;

    if ((p_control.fsci.next_free_sector + DEFAULT_TABLE_SIZE) > p_control.fsci.last_sector_index_on_partition)
    {
        // We don't have space, report error 
        return -EINVAL;
    }
    p_control.fsci.next_free_sector += DEFAULT_TABLE_SIZE; 

    fseek ( disk , (p_control.fsci.this_partition_offset_on_disk) * SECTOR_SIZE, SEEK_SET );
    fwrite(&p_control.fsci, 1, SECTOR_SIZE, disk);

    return return_index;
}

int get_free_sectors(int num_sectors_needed, lsfs_sector_offset* output_array) {

    if ((p_control.fsci.next_free_sector + num_sectors_needed) > p_control.fsci.last_sector_index_on_partition ) 
    {
        // We cannot assign what we want. 
        return -EINVAL;
    }
    for (int i = 0; i < num_sectors_needed; ++i)
    {
        output_array[i] = p_control.fsci.next_free_sector;
        p_control.fsci.next_free_sector += DEFAULT_FILE_SIZE;
    }

    fseek ( disk , (p_control.fsci.this_partition_offset_on_disk) * SECTOR_SIZE, SEEK_SET );
    fwrite(&p_control.fsci, 1, SECTOR_SIZE, disk);
    
    return 0;
}

int create_file_system() {
    //char* sector_to_write;
    // make default File System Control information (FSCI)
    // first integer says how many pointers we got
    // to master tag tables 
    // Second and forward is the pointers to the master Tag Tables
    // we need the first number to allocate memory at one go. 
    int* zero_buffer;
    FSCI fsci;
    fsci.this_partition_offset_on_disk = 1;
    //fsci.maximum_sectors_on_partition = 1048576; // Max 4GiB
    fsci.next_free_sector = 257;
    
    fseek ( disk , 0, SEEK_SET );
    fwrite(&fsci, 1, sizeof(fsci), disk);
    zero_buffer = calloc(1, (4096 - sizeof(fsci)));
    fwrite(zero_buffer, 1, (4096 - sizeof(fsci)), disk);
    free(zero_buffer);
    /* MASTER TAG TABLE */

    table_entry master_table[DEFAULT_TABLE_SIZE];
    memset(master_table, 0, (DEFAULT_TABLE_SIZE * sizeof(table_entry)));

    fwrite(&master_table, 1, sizeof(master_table), disk);
    zero_buffer = calloc(1, 16);
    fwrite(zero_buffer, 1, 16, disk);
    free(zero_buffer);
    return 0;
}

int lsfs_disk_load_disk() {
    // Find the partition talbe: 
    // This makes is BIOS dependent. 
    // UEFI is not supported. 
    Master_Boot_record mbr;
    fseek( disk , 0 * SECTOR_SIZE, SEEK_SET );
    fread(&mbr, 1, sizeof(mbr), disk);

    for (int i = 0; i < NUMBER_OF_MBR_PARTITIONS; ++i)
    {
        // TODO (Jørn) We maybe wnat to optimize, such that we can detect if we have more than one partition opn the system. 
        if (mbr.partitions[i].partition_type == 0x18)
        {
            printf("%d\n", mbr.partitions[i].LBA_abs_first_sector);

            // First we find the File system control information. 
            fseek ( disk , mbr.partitions[i].LBA_abs_first_sector * SECTOR_SIZE, SEEK_SET );
            fread(&p_control.fsci, 1, SECTOR_SIZE , disk);
            //printf("next free sector: %d\n", p_control.fsci.next_free_sector);
            //printf("next free ID: %d\n", p_control.fsci.next_uniqe_id);

            // next we find the Mater Table. 
            fseek ( disk , (mbr.partitions[i].LBA_abs_first_sector + 1) * SECTOR_SIZE, SEEK_SET );
            fread(&p_control.master_table, 1, DEFAULT_TABLE_SIZE * SECTOR_SIZE , disk);

            return 1;
        }
    }
    return 0; 
}


int lsfs_disk_create_entry(const char* path, Table_Entry_Kind entry_kind) 
{

    lsfs_string_array split_path = lsfs_string_split_c(path, '/', false);
    lsfs_string filename = split_path.strings[split_path.length-1];    

    // Start from the master table
    int free_index = -1; // -1 is no index found. 
    Directory_Table *dir_table = &p_control.master_table;
    lsfs_sector_offset table_disk_position = p_control.fsci.master_table_index;
    for (int i = 0; i < split_path.length; ++i)
    {
        for (int j = 0; j < DEFAULT_TABLE_SIZE; ++j)
        {
            if (i == (split_path.length - 1))
            {
                // Find free index and be sure that there dosent exist a file with the same name.
                if (dir_table->entries[j].entry_kind == ENTRY_EMPTY)
                {
                    // Set the free index, continue to see if the filename exist. 
                    // if not -1, we have found a better index. 
                    if (free_index == -1) 
                    {
                        printf("Index found for file: %d\n", j);
                        free_index = j;
                    }
                }
                else if (strcmp(dir_table->entries[j].filename, split_path.strings[0].chars) == 0)
                {
                    // Abort mission, we have a file with the same name. 
                    return -EINVAL;
                }
            }
            else 
            {
                if (strcmp(dir_table->entries[j].filename, split_path.strings[0].chars) == 0)
                {
                    // We have found the next directory to traverse. 
                    ;
                }
            }
        }
    }

    if (free_index == -1)
    {
        // The table is full, and we cannot create an entry
        return -EINVAL;
    }

    // Find the entry for the file in the table structure: 
    dir_table->entries[free_index].file_id = p_control.fsci.next_uniqe_id;
    p_control.fsci.next_uniqe_id++; 

    sprintf(dir_table->entries[free_index].filename, "%s", filename.chars);  
    dir_table->entries[free_index].entry_kind = entry_kind;
    if (entry_kind == ENTRY_DIRECTORY) 
    {
        dir_table->entries[free_index].data_pointer[0] = get_free_sectors_table();
        dir_table->entries[free_index].file_size = 5120;
    }
    else if (entry_kind == ENTRY_FILE)
    {
        // We assign one data pointer consiting of DEFAULT_FILE_SIZE sectors
        get_free_sectors_table(1, dir_table->entries[free_index].data_pointer);
    }
    else
    {
        return -EINVAL;
    }

    /*
    find_file->creation_date = (uint64_t) current_time;
    find_file->access_time = (uint64_t) current_time;
    find_file->modification_time = (uint64_t) current_time;
    find_file->data = p_control.master_table.entries[i].data_pointer;
    find_file->owner_id = getuid();
    new_file_data.owner_id = getuid();
    time_t current_time;
    time ( &current_time );
    */

    fseek ( disk , (table_disk_position + free_index) * SECTOR_SIZE, SEEK_SET );
    fwrite(&dir_table->entries[free_index], 1, SECTOR_SIZE, disk);

    return 0;
}

int save_modified_file_information(lsfs_file* file) {
    // Write the file struct into the table_entry, such that we can save the data correct. 
    
    p_control.master_table.entries[file->table_entry_pointer].file_id = file->file_id;
    memcpy(p_control.master_table.entries[file->table_entry_pointer].filename, file->filename, 256);
    p_control.master_table.entries[file->table_entry_pointer].file_size = file->size; // p_control.master_table.entries[i].data_pointer[0]; //;
    //p_control.master_table.entries[i].data_pointer = find_file->data;

    write_data_to_disk(file->table_entry_pointer, file->file_block_size, &p_control.master_table.entries[file->table_entry_pointer]);
    return 0;
}


int write_data_to_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_to_write) {
    fseek ( disk, (index * SECTOR_SIZE), SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int written = fwrite(data_to_write, 1, (4 * SECTOR_SIZE), disk);
    return written;
}

int write_data_to_disk_off(lsfs_sector_offset index, void* data_to_write, int offset) {
    fseek ( disk, (index * SECTOR_SIZE) + offset, SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int written = fwrite(data_to_write, 1, (4 * SECTOR_SIZE), disk);
    return written;
}

int read_data_from_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_buffer) {
    fseek ( disk, (index * SECTOR_SIZE ), SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int read = fread(data_buffer, 1, (file_block_size * SECTOR_SIZE), disk);
    return read;
}

#endif