@startuml

title Objects found inside Ugarit vaults

!define ATAG << (t,#CCAAAA) abstract tag >> #DDBBBB
!define TAG << (T,#CCAAAA) tag >> #CCAAAA

!define ABLK << (b,#BBBBBB) abstract block >> #BBBBBB
!define BLK << (B,#BBBBBB) block >> #AAAAAA

!define ASXP << (s,#AACCAA) abstract sexpr >> #BBDDBB
!define SXP << (S,#AACCAA) sexpr >> #AACCAA

abstract class Tag ATAG {
         name
}

abstract class Block ABLK {
         key
}

note left of Block
     All blocks are identified by a key
     (which is a hash of their contents
     and type), a type, and the actual
     contents.
end note

class SnapshotTag TAG
class ArchiveTag TAG

class Vault << (V,Wheat) >>

Vault "1" o-- "*" Tag
Vault "1" o-- "*" Block

Tag <|-- SnapshotTag
Tag <|-- ArchiveTag

note right of Tag
     To provide roots into the
     DAG of blocks, tags are
     mutable (typed) pointers
     from a name to a block
end note

SnapshotTag o-- "1" snapshot
ArchiveTag o-- "1" archive

Block <|-- snapshot
snapshot o-- snapshot : previous
snapshot o-- FileSystem : contents
snapshot o-- "f/fi" : log

note on link
     Every snapshot block
     has a reference to a file
     containing a log of events
     that occurred during the snapshot.
end note

class snapshot BLK {
      properties
}

note left of snapshot
     A snapshot tag points
     to a chain of snapshots
     of a filesystem, forming
     a history.
end note

Block <|-- archive
archive o-- archive : previous
archive o-- "a/ai" : contents
archive o-- "f/fi" : log

note on link
     Every archive import block
     has a reference to a file
     containing a log of events
     that occurred during the snapshot.
end note

class archive BLK {
      properties
}

note left of "a/ai"
     Each archive import
     contains a series of
     ArchiveEntry sexprs,
     stored as a tree of
     direct (a) and indirect
     (ai) blocks.
end note

note right of archive
     An archive tag points
     to a chain of archive
     imports, preserving
     the history of the
     archive as it grows
     and changes.
end note

class "a/ai" BLK
Block <|-- "a/ai"

class ArchiveEntry SXP {
      metadata
}

note left of ArchiveEntry
     Each ArchiveEntry associates a FileSystem object
     in the vault (a file or a directory tree) with
     some metadata.
end note

"a/ai" *-- ArchiveEntry

ArchiveEntry o-- "1" FileSystem : archived object

Block <|-- FileSystem
abstract class FileSystem ABLK
class "d/di" BLK

note right of "d/di"
     A directory is represented as a
     series of DirectoryEntry sexprs,
     stored as a tree of direct (d)
     and indirect (di) blocks.
end note

class "f/fi"  BLK {
      data
}

note right of "f/fi" {
     Actual file data
     is stored in a tree of
     file data (f) and
     indirect (fi) blocks.
}

FileSystem <|-- "d/di"
FileSystem <|-- "f/fi"

"d/di" *-- DirectoryEntry

abstract class DirectoryEntry ASXP {
      name
      atime
      ctime
      mtime
      type
      mode
      uid
      gid
}

DirectoryEntry <|-- SubdirectoryEntry
SubdirectoryEntry o-- "1" "d/di" : contents
class SubdirectoryEntry SXP {
      total-files
      total-bytes
}

DirectoryEntry <|-- FileEntry
class FileEntry SXP {
      size
}
FileEntry o-- "1" "f/fi" : contents

DirectoryEntry <|-- BlockDeviceEntry
class BlockDeviceEntry SXP {
      number
}

DirectoryEntry <|-- CharacterDeviceEntry
class CharacterDeviceEntry SXP {
      number
}

DirectoryEntry <|-- SymlinkEntry
class SymlinkEntry SXP {
      target
}

DirectoryEntry <|-- FIFOEntry
class FIFOEntry SXP

@enduml