#include <stdint.h>

/**
 * media organization:
 * * boot record (1 sector, so could be called boot sector): BPB + Extended Boot Record
 * * File Allocation Table (FAT)
 * * data area
 */


struct ebr_fat16 { // Extended Boot Record for FAT16
    uint8_t drive_number;
    uint8_t flags;
    uint8_t signature; // Must be 0x29 for FAT16
    uint8_t vol_id[4];
    uint8_t vol_label[11];
    uint8_t sys_id[8]; // Do not trust this!
    uint8_t bootcode[448];
    uint16_t bootable_signature; // 0xAA55
} __attribute__((packed));

struct ebr_fat32 { // Extended Boot Record for FAT32
    uint32_t fat_size;
    uint16_t flags;
    uint16_t fat_version_number;
    uint32_t root_cluster_nb;
    uint8_t reserved[12];
    uint8_t drive_number;
    uint8_t flags_nt;
    uint8_t signature;
    uint8_t vol_id[4];
    uint8_t vol_label[11];
    uint8_t sys_id[8]; // Should be always "FAT32"
    uint8_t bootcode[420];
    uint16_t bootable_signature; // 0xAA55
} __attribute__((packed));

struct bpb { // Bios Param Block
    uint8_t jump_ins[3];
    uint8_t oem_id[3];
    uint16_t bytes_per_sector;
    uint8_t sector_per_cluster;
    uint16_t reserved_sectors; // boot sectors included
    uint8_t nb_fat;
    uint16_t nb_root_dirs;
    uint16_t nb_sectors;
    uint8_t media_description_type;
    uint16_t sectors_per_fat;
    uint16_t sectors_per_track;
    uint16_t number_of_heads;
    uint32_t hidden_sectors;
    uint32_t nb_large_sectors;
    union {
        struct ebr_fat32 fat32;
        struct ebr_fat16 fat16;
    };
} __attribute__((packed));

typedef enum {
    READ_ONLY = 0x01,
    HIDDEN    = 0x02,
    SYSTEM    = 0x04,
    VOLUME_ID = 0x08,
    DIRECTORY = 0x10,
    ARCHIVE   = 0x20,
    LFN       = READ_ONLY | HIDDEN | SYSTEM | VOLUME_ID,
} __attribute__((__packed__)) directory_entry_type_t;

struct directory_entry {
    uint8_t filename[11];
    directory_entry_type_t type;
    uint8_t reserved;
    uint8_t creation_time_hundredths_sec;
    uint16_t creation_time;    // hour[5] min[6] sec[5]
    uint16_t creation_date;    // year[7] month[4] day[5]
    uint16_t last_access_date; // year[7] month[4] day[5]
    uint16_t cluster_nb_high;
    uint16_t modification_time; // hour[5] min[6] sec[5]
    uint16_t modification_date; // year[7] month[4] day[5]
    uint16_t cluster_nb_low;
    uint32_t size; // in bytes
} __attribute__((packed));