| 1 | # FileSystem
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| 2 |
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| 3 | Below is a brief overview of the different types used for the Fission FileSystem
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| 4 |
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| 5 | ## Interfaces
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| 6 |
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| 7 | ### Tree / File vs HeaderTree / HeaderFile
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| 8 | `Tree` / `File` describe the main interfaces for trees and files. `HeaderTree` / `HeaderFile` inherit from `Tree` / `File` but include extra methods for dealing with header options (metadata, pins, caching, etc).
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| 9 |
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| 10 | ## Classes
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| 11 |
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| 12 | ### BaseTree / BaseFile
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| 13 | These are abstract classes that implement methods that are common to all trees and files: `ls`, `mkdir`, `cat`, `add`, `rm`, `get`. These classes implement the `Tree` & `File` interfaces respectively.
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| 14 |
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| 15 | ### BareTree / BareFile
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| 16 | These are isomorphic to IPFS DAG objects, but contain a wrapper so that they share a common interface with our custom Tree nodes. These are all public, and implement the `Tree` interface.
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| 17 |
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| 18 | ### PublicTree / PublicFile
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| 19 | This is v1.0.0 of the Fission FileSystem. It uses a 2-layer approach where each directory actually points to a "header" directory which incldues all of the metadata and FFS features for folders & files as well as an `userland` link that points to the actual tree or file. Each directory contains a `skeleton` of the directory structure beneath it. This allows you to make one trip to the network and derive the entire skeleton of a file system
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| 20 |
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| 21 | ### PrivateTree / PrivateFile
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| 22 | These inherit from `PublicTree` / `PublicFile`, but each node has a `parentKey` and an `ownKey`. where the folder itself is encrypted with the `parentKey` and `userland` & it's decendents are encrypted with `ownKey`
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| 23 |
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| 24 | ### Inheritance structure
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| 25 | As additional versions of the FS are added, the inheritance structure will look like:
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| 26 | ```
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| 27 | publicV1.0.0 -> privateV1.0.0
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| 28 | |
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| 29 | v
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| 30 | publicV1.0.1 -> privateV1.0.1
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| 31 | |
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| 32 | v
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| 33 | publicV1.1.0 -> privateV1.1.0
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| 34 | ```
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| 35 |
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| 36 | ### Header
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| 37 | Most Fission FileSystem information is stored in the Header file. So most upgrades to the version of a FileSystem will include upgrades to the Header. This means we'll likely have a different `Header` type for each version of the FileSystem, and we can expect a simple lineage of inheritance (`HeaderV1.0.0 -> HeaderV1.0.1 -> HeaderV1.1.0`). Each version of the FileSystem will include an implementation of `PublicTree`, `PublicFile`, `PrivateTree`, `PrivateFile`, and a `Header` parser
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