# Dependencies

## Electron

[Electron](https://www.electronjs.org) is a cross-platform (Linux, Windows,
macOS) way for creating desktop apps using TypeScript.

Electron embeds Chromium and Node.js in the generated app's binary. The
generated app thus consists of two separate processes - the _main_ process, and
a _renderer_ process.

-   The _main_ process is runs the embedded node. This process can deal with the
    host OS - it is conceptually like a `node` repl running on your machine. In
    our case, the TypeScript code (in the `src/` directory) gets transpiled by
    `tsc` into JavaScript in the `build/app/` directory, which gets bundled in
    the generated app's binary and is loaded by the node (main) process when the
    app starts.

-   The _renderer_ process is a regular web app that gets loaded into the
    embedded Chromium. When the main process starts, it creates a new "window"
    that shows this embedded Chromium. In our case, we build and bundle a static
    export of the [Photos web app](../web/README.md) in the generated app. This
    gets loaded by the embedded Chromium at runtime, acting as the app's UI.

There is also a third environment that gets temporarily created:

-   The [preload script](../src/preload.ts) acts as a gateway between the _main_
    and the _renderer_ process. It runs in its own isolated environment.

### electron-builder

[Electron Builder](https://www.electron.build) is used for packaging the app for
distribution.

During the build it uses
[electron-builder-notarize](https://github.com/karaggeorge/electron-builder-notarize)
to notarize the macOS binary.

[electron-updater](https://www.electron.build/auto-update#debugging), while a
separate package, is also a part of Electron Builder. It provides an alternative
to Electron's built in auto updater, with a more flexible API. It supports auto
updates for the DMG, AppImage, DEB, RPM and NSIS packages.

### electron-log

[electron-log](https://github.com/megahertz/electron-log) is used for logging.
Specifically, it allows us to log to a file (in addition to the console of the
Node.js process), and also handles log rotation and limiting the size of the log
files.

### next-electron-server

This spins up a server for serving files using a protocol handler inside our
Electron process. This allows us to directly use the output produced by
`next build` for loading into our renderer process.

## Dev

See [web/docs/dependencies#DX](../../web/docs/dependencies.md#dev) for the
general development experience related dependencies like TypeScript etc, which
are similar to that in the web code.

Some extra ones specific to the code here are:

* [concurrently](https://github.com/open-cli-tools/concurrently) for spawning
  parallel tasks when we do `yarn dev`.

* [shx](https://github.com/shelljs/shx) for providing a portable way to use Unix
  commands in our `package.json` scripts. This allows us to use the same
  commands (like `ln`) across different platforms like Linux and Windows.