#+title: WikiMusic API
#+options: toc:nil

API and Persistence layer to PostgreSQL for WikiMusic, the invite-only private knowledge sharing of music community.

/WikiMusic/

#+begin_html
<div>
<img src="https://img.shields.io/badge/Haskell-5D4F85?logo=haskell&logoColor=fff&style=plastic" alt="Haskell"/>
<img src="https://img.shields.io/badge/PostgreSQL-4169E1?logo=postgresql&logoColor=fff&style=plastic" alt="PostgreSQL"/>
<img src="https://img.shields.io/badge/GNU%20Emacs-7F5AB6?logo=gnuemacs&logoColor=fff&style=plastic" alt="GNU Emacs"/>
<img src="https://img.shields.io/badge/NixOS-5277C3?logo=nixos&logoColor=fff&style=plastic" alt="NixOS"/>
<img src="https://img.shields.io/badge/Redis-DC382D?logo=redis&logoColor=fff&style=plastic" alt="Redis"/>
</div>
#+end_html


WikiMusic as a software means an ingenious combination of a backend, a REST API, a database, and a user-interface to create a Content Management System (CMS) and a Gallery for music of all kinds, with educational intents.

This is 100% free software, licensed under the GNU General Public License v3 or later.
[[https://www.gnu.org/licenses/gpl-3.0.en.html][Refer to the full license, on GNU's website]]

The WikiMusic project is an invite-only community, with the goal of knowledge sharing, and not for profit driven.

[[https://www.buymeacoffee.com/jjbigorra][Please donate by clicking here]]. This helps us keep the underlying cloud infrastructure and Joe's work hours going strong.

In this Git repository you will find the source code behind WikiMusic's backend.

To see the living API spec of WikiMusic, also known as API definition, go to [[file:src/WikiMusic/Servant/ApiSpec.hs]]

** Project structure

~src/WikiMusic/~ harbours the Haskell code that makes the API work. Inside there you will find:
- ~Console~ is a package with functionality related to logging to console / stdout.
- ~Free~ is a package with free monadic definitions of the possible interactions with the WikiMusic system.
- ~Interaction~ is a package with the implementation agnostic "business logic" of the WikiMusic system.
- ~Model~ is a package with common data models to the entire system.
- ~PostgreSQL~ is a package with the PostgreSQL implementation of several ~Command~ and ~Query~ interactions.
- ~SMTP~ is a package that contains SMTP Mail related implementations.
- ~Servant~ is a package that contains the API definition, routes and wiring of HTTP.
- ~Boot.hs~ is the entry point to start this REST API.
- ~Protolude.hs~ contains a custom tailor-made standard library (prelude) for WikiMusic, which helps developing.

** Implementation details

WikiMusic API is made using Haskell and free(er) monad techniques, along with great libraries made by the brilliant Haskell community. Some worthy mentions include servant, hasql, rio, free-alacarte, wai, keuringsdienst, optics.

Using free(er) monads means that we can describe the business logic of certain layers at a very high abstraction level, and we are free to interpret this logic as we see fit, depending on the use case. This helps testing, decoupling, and maintaining code.

** Installing and running

This Haskell project requires certain C / C++ libraries to run. Pay attention the the error messages at build time and install dependencies accordingly.

We recommend running WikiMusic API with the Nix package manager, and even better with NixOS, since this project has a close integrations for NixOS machines.

Otherwise, on systems like Void Linux :
#+begin_src
sudo xbps-install zlib zlib-devel libpqxx-devel postgresql-libs postgresql-libs-devel ncurses-libtinfo-devel
#+end_src

You will also need a PostgreSQL database and a Redis instance (to rate limit certain requests) to be accessible from WikiMusic API and running.

WikiMusic will take care of the database schema migrations for you.

There are also example docker compose files ready to be used at the ~resources~ folder for your convenience.

* User permission

In WikiMusic we have users of several kinds, with different privileges. See the table below for an understanding on what you can/cannot do depending on your rank.

Demo user:

| Resource | Create | Read | Update | Delete | Comment | Like/Dislike |
|----------+--------+------+--------+--------+---------+--------------|
| Song     | ❌     | ✅   | ❌     | ❌     | ✅      | ✅           |
| Artist   | ❌     | ✅   | ❌     | ❌     | ✅      | ✅           |
| Genre    | ❌     | ✅   | ❌     | ❌     | ✅      | ✅           |
| User     | ❌     | ❌   | ❌     | ❌     | N/A     | N/A          |

Low-rank user:

| Resource | Create | Read | Update | Delete | Comment | Like/Dislike |
|----------+--------+------+--------+--------+---------+--------------|
| Song     | ✅     | ✅   | ✅     | ❌     | ✅      | ✅           |
| Artist   | ✅     | ✅   | ✅     | ❌     | ✅      | ✅           |
| Genre    | ✅     | ✅   | ✅     | ❌     | ✅      | ✅           |
| User     | ❌     | ❌   | ❌     | ❌     | N/A     | N/A          |

Maintainer user:

| Resource | Create | Read | Update | Delete | Comment | Like/Dislike |
|----------+--------+------+--------+--------+---------+--------------|
| Song     | ✅     | ✅   | ✅     | ✅     | ✅      | ✅           |
| Artist   | ✅     | ✅   | ✅     | ✅     | ✅      | ✅           |
| Genre    | ✅     | ✅   | ✅     | ✅     | ✅      | ✅           |
| User     | ✅     | ✅   | ✅     | ❌     | N/A     | N/A          |

Super-user: can do everyting to the system!

* NixOS

Enter a nice shell provided by flakes, by doing ~nix develop~. You can also do ~nix build~ to build the project with Nix.

Run the API with for example: ~nix run . -- "./resources/config/run-local.toml"~ .


** Bare metal

It can be needed, if you want to run bare metal without direnv, to do things like this sometimes in the ~cabal.project~ (find by ~find /nix -name "zlib.h*"~):

#+begin_src nix
package postgresql-libpq
    extra-include-dirs: /nix/store/ahb6l0carh3yc6a5d4zdxsxf69sdhnhh-postgresql-15.4/include

package zlib
    extra-include-dirs: /nix/store/686lhcz4bwg3wk09pi1xxjgzbxv7ys5q-zlib-1.3-dev/include
    extra-lib-dirs: /nix/store/4rx3vkkd91wkbhpflsplfga603cp1l1c-zlib-1.3/lib
#+end_src

* API documentation

When running WikiMusic API, you can navigate to ~<url where you serve it>/swagger.json~ to get the OpenAPI spec for WikiMusic.


* Example config file

For local runs you can take a look at [[file:resources/config/run-local.toml]].

* Production environment diagram

#+begin_src dot :file resources/images/production-env-diagram.png :exports results :mkdirp yes
  digraph prodenv {
  subgraph clusterA {
  fontname="Inter,Helvetica,Arial,sans-serif"
  node [ shape="box", fontname="Inter,Helvetica,Arial,sans-serif" ]
  edge [ fontname="Inter,Helvetica,Arial,sans-serif", arrowhead="rnormal", arrowtail="dot" ]

  I1 [ label="api.wikimusic.jointhefreeworld.org via HTTPS" ]
  I2 [ label="AWS Cloudfront" ]
  I3 [ label="AWS EC2 t3.small instance\nrunning NixOS" ]
  I4 [ label="Haskell + Servant + PostgreSQL + Redis" ]
  I5 [ label="GitLab CI/CD" ]
  I6 [ label="AWS SQS queue" ]


  I1 -> I2;
  I2 -> I3;
  I3 -> I4;
  I5 -> I6;
  I3 -> I6;

  }
  }
#+end_src

#+RESULTS:
[[file:resources/images/production-env-diagram.png]]
