== Package Manager (ppman) == [ Piston ] The package manager is the part of the API responsible for managing different versions of different languages, managing their installation, uninstallation and their dependencies. The package manager talks over the piston api and is built directly into piston, although has parts which are not directly built into the API (i.e. the repositories and the cli utility). The package manager is a complex part of piston, and requires 2 different file specifications - the repository index file and the package file. == Repository Index File == The piston repository is the central place where packages are hosted and downloaded from. This repository can either be a webserver or a local file containing the right content - as long as its accessable by a URL, its considered a valid repository by piston. A repository URL is simply a URL pointing to a repository index file, as set out by the following information. A repository index file is a YAML file containing the keys: `schema`, `baseurl` and `packages`. The schema key simply should have a value of `ppman-repo-1`. This indicates the version and file format for the client to recieve. The baseurl key contains the base url that relative URLs should be based off, this doesn't need to be related to the url that the repository index is hosted at, only the downloadable files, which are possible to split over many domains by using absolute paths. The packages key contains a list of packages, which contain the keys: `author`, `language`, `version`, `checksums`, `dependencies`, `size`, `buildfile` and `download`. The author field is self explainatory, it is simply the authors name and email, formatted similar to git's default format: `Full Name `. If the repository index is automatically generated, it is best to use the commit author's name in here. The language and version fields define the version and name of the compiler or interpreter contained within. The language should not include a version at all. In the case of python, use the name python for both python 2 and 3, using the version field to differentiate between the 2. The checksums field is simply a map of hash types to hashes, hash types include md5, sha1, sha256, sha512. The digests should simply be written as lowercase hex characters. Only one checksum is required, but if more are supplied the most secure one is picked, with sha512 as the highest possible. The dependencies is simply a map of language names to versions, which should be installed for the package to run correctly. An example of this would be typescript requires node to run. The size field is the number of bytes the package file is in size, while uncompressed. This is used to determine if there is enough room, and thus should be accurate. The buildfile field is a URL pointing to the exact build script for this build. This should always point to a URL either containing steps, a script or other means of reproducing the build. This field is purely so people can understand how the image was built, and to make sure you aren't packing any mallicious code into it. The final field is download, this points to a URL of which the package file can be obtained from. If this is a relative url, the baseurl will be appended to it. This is particularly useful if everything is stored within 1 s3 bucket, or you have a repository in a folder. == Package File == TODO