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https://github.com/propensive/surveillance

Representation-agnostic filewatching with streams in Scala
https://github.com/propensive/surveillance

file-watching filesystem-events filewatcher scala

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Representation-agnostic filewatching with streams in Scala

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# Surveillance



__Representation-agnostic filewatching with streams in Scala__



__Surveillance__ watches directories for changes, and provides a `LazyList` of streaming `WatchEvent`s. While it

works well with [Galilei](https://github.com/propensive/galilei/), it can work with any representation of

paths.



## Features



- simple API for most common filesystem operations

- read from and write to files on disk with a variety of different types

- simple streaming to and from disk with `LazyList`s

- employs `IArray[Byte]` for fast, random-access, immutable chunking of byte data

- encoding-aware operations involving `String`s



## Availability



## Getting Started



Surveillance watches directories for changes to their contents, through an extension method, `watch()`, on a

type representing a directory or a `Seq` of such types. For [Galilei](https://github.com/propensive/galilei)'s

`Directory` type, this works straight away. Other libraries which provide directory-like types can integrate with

Surveillance just by defining two simple [typeclass instances](#defining-typeclass-instances).



### Watching



A simple setup for watching a directory looks like this:

```scala

import galilei.*

import serpentine.*

import surveillance.*



val dir = (Unix / p"home" / p"work" / p"updates").directory()

val watcher = dir.watch()

```



Constructing a new `Watcher` on a directory will register that directory with the filesystem's filewatching service

and start a new thread to respond to updates.



The most important method of a `Watcher` is its `stream` method, which will return a `LazyList[WatchEvent]`



## Status



Surveillance is classified as __fledgling__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Surveillance is designed to be _small_. Its entire source code currently consists

of 138 lines of code.



## Building



Surveillance will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Surveillance?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Surveillance's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Surveillance and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `surveillance`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Surveillance's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Surveillance are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/surveillance/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Surveillance

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Surveillance was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



This library watches directories for changes, which is to say it keeps them under __surveillance__.



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows a glistening eye, watching or _surveilling_.



## License



Surveillance is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).