1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146

//! Reference: https://www.sqlite.org/fileformat2.html

pub(self) mod db_filesize_in_pages;
pub(self) mod file_change_counter;
pub(self) mod file_format_version_numbers;
pub(self) mod magic_header_string;
pub(self) mod page_size;
pub(self) mod payload_fractions;
pub(self) mod reserved_bytes_per_page;

use self::{
  db_filesize_in_pages::DatabaseFileSizeInPages,
  file_change_counter::FileChangeCounter,
  file_format_version_numbers::FileFormatVersionNumbers,
  magic_header_string::MagicHeaderString, page_size::PageSize,
};
use crate::{
  header::{
    payload_fractions::PayloadFractions,
    reserved_bytes_per_page::ReservedBytesPerPage,
  },
  result::{SQLiteError, SQLiteResult},
};
use anyhow::bail;

/// # Database File Format
///
/// |Offset	| Size	| Description|
/// |-------|-------|------------|
/// |0	    | 16	  | The header string: "SQLite format 3\000" |
/// |16	    | 2	    | The database page size in bytes. Must be a power of two between 512 and 32768 inclusive, or the bytes 1 representing a page size of 65536. |
/// |18	    | 1	    | File format write version. 1 for legacy; 2 for WAL. |
/// |19	    | 1	    | File format read version. 1 for legacy; 2 for WAL. |
/// |20	    | 1	    | Bytes of unused "reserved" space at the end of each page. Usually 0. |
/// |21	    | 1	    | Maximum embedded payload fraction. Must be 64. |
/// |22	    | 1	    | Minimum embedded payload fraction. Must be 32. |
/// |23	    | 1	    | Leaf payload fraction. Must be 32. |
/// |24	    | 4	    | File change counter. |
/// |28	    | 4	    | Size of the database file in pages. The "in-header database size". |
/// |32	    | 4	    | Page number of the first freelist trunk page. |
/// |36	    | 4	    | Total number of freelist pages. |
/// |40	    | 4	    | The schema cookie. |
/// |44	    | 4	    | The schema format number. Supported schema formats are 1, 2, 3, and 4. |
/// |48	    | 4	    | Default page cache size. |
/// |52	    | 4	    | The page number of the largest root b-tree page when in auto-vacuum or incremental-vacuum modes, or zero otherwise. |
/// |56	    | 4	    | The database text encoding. A bytes of 1 means UTF-8. A bytes of 2 means UTF-16le. A bytes of 3 means UTF-16be. |
/// |60	    | 4	    | The "user version" as read and set by the user_version pragma. |
/// |64	    | 4	    | True (non-zero) for incremental-vacuum mode. False (zero) otherwise. |
/// |68	    | 4	    | The "Application ID" set by PRAGMA application_id. |
/// |72	    | 20	| Reserved for expansion. Must be zero. |
/// |92	    | 4	    | The version-valid-for number. |
/// |96	    | 4	    | SQLITE_VERSION_NUMBER |
#[derive(Debug)]
pub struct SqliteHeader {
  /// The header string: "`SQLite format 3\000`".
  magic_header_string: MagicHeaderString,
  /// The database page size in bytes.
  ///  Must be a power of two between 512 and 32768 inclusive,
  /// or the bytes 1 representing a page size of 65536.
  page_size: PageSize,
  /// File format version numbers.
  file_format_version_numbers: FileFormatVersionNumbers,
  /// Bytes of unused "reserved" space at the end of each page. Usually 0.
  reserved_bytes_per_page: ReservedBytesPerPage,
  /// Payload Fractions.
  payload_fractions: PayloadFractions,
  /// File change counter.
  file_change_counter: FileChangeCounter,
  // Size of the database file in pages. The "in-header database size".
  db_filesize_in_pages: DatabaseFileSizeInPages,
}

impl SqliteHeader {
  pub fn magic_header_string(&self) -> &MagicHeaderString {
    &self.magic_header_string
  }

  pub fn page_size(&self) -> &PageSize {
    &self.page_size
  }
}
impl TryFrom<&[u8; 100]> for SqliteHeader {
  type Error = SQLiteError;

  fn try_from(bytes: &[u8; 100]) -> Result<Self, Self::Error> {
    let bytes = bytes;

    println!("{:x?}", &bytes[0..=15]);
    println!("{:x?}", &bytes[16..=17]);
    println!("{:x?}", &bytes[18..=19]);
    println!("{:x?}", &bytes[20]);
    println!("{:x?}", &bytes[21..=23]);
    println!("{:x?}", &bytes[24..=27]);
    println!("{:x?}", &bytes[28..=31]);

    let magic_header_string = MagicHeaderString::parse_bytes(&bytes[0..=15])?;
    let page_size = PageSize::parse_bytes(&bytes[16..=17])?;
    let file_format_version_numbers =
      FileFormatVersionNumbers::parse_bytes(&bytes[18..=19])?;
    let reserved_bytes_per_page =
      ReservedBytesPerPage::parse_bytes(&[bytes[20]])?;
    let payload_fractions = PayloadFractions::parse_bytes(&bytes[21..=23])?;

    let file_change_counter = FileChangeCounter::parse_bytes(&bytes[24..=27])?;
    let db_filesize_in_pages =
      DatabaseFileSizeInPages::parse_bytes(&bytes[28..=31])?;
    Ok(Self {
      magic_header_string,
      page_size,
      file_format_version_numbers,
      reserved_bytes_per_page,
      payload_fractions,
      file_change_counter,
      db_filesize_in_pages,
    })
  }
}

trait ParseBytes<T>
where
  Self: Sized,
{
  fn struct_name() -> &'static str;
  fn bytes_length() -> usize;
  fn parsing_handler(bytes: &[u8]) -> SQLiteResult<Self>;

  fn check_payload_size(bytes: &[u8]) -> SQLiteResult<()> {
    if bytes.len() != Self::bytes_length() {
      bail!("Invalid size for {}", Self::struct_name());
    } else {
      Ok(())
    }
  }
  fn parse_bytes(bytes: &[u8]) -> SQLiteResult<Self> {
    Self::check_payload_size(bytes)?;
    Self::parsing_handler(bytes)
  }
}

// TODO
trait ValidateParsed<T>
where
  Self: Sized + ParseBytes<T>,
{
  fn validate_parsed(&self) -> SQLiteResult<()>;
}