Update README.md

README.md

@@ -24,9 +24,66 @@ Future versions may bring:
 
 The long term vision is to offer something similar to Plex, but for comics!
 
+## What does it do?
+
+Komga will scan your library's root folder for directories containing supported files (at the moment `cbz`, `zip`, `cbr` and `rar`):
+
+- each folder containing comic books will be made as a `Serie`
+- each comic book file inside a `Serie` will be made as a `Book`
+
+It works with subfolders too, so if you have a structure like this:
+
+```
+-Parent
++--SubFolder
+| +file1.cbz
+| +file2.cbz
++direct1.cbz
+```
+
+Komga will generate:
+
+- a `Serie` called _Parent_, containing a `Book` called _direct1_
+- a `Serie` called _SubFolder_, containing two `Book`s called _file1_ and _file2_
+
+On rescans, Komga will update Series and Books, add new ones, and remove the ones for which files don't exist anymore.
+
+Then it will _parse_ each book, which consist of indexing pages (images in the archive), and generating a thumbnail.
+
+Komga offers a REST API, which you can browse using Swagger. It's available at `/swagger-ui.html`. The API offers __file download__ and __page streaming__.
+
+In order to access the API, you will need to authenticate using Basic Authentication, with one of the 2 built-in users (`admin` or `user`).
+
 ## Installation
 
-The easiest way to install Komga is to use Docker. You can have a look at the sample [docker-compose.yml](./doc/docker-compose.yml).
+The easiest way to install Komga is to use Docker. You can have a look at the sample [`docker-compose.yml`](./doc/docker-compose.yml).
+
+Alternatively you can run it from a `jar` file. I don't provide one at the moment, but I could if people are interested. You can also build it yourself by using `gradlew bootJar` to generate it.
+
+## Configuration
+
+Komga relies heavily on [Spring Boot's configuration](https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html), leveraging `profiles` and configuration `properties`.
+
+The easiest way to configure is either via environment variables (a good fit for `docker-compose`) or by using an `application.yml` file located in the same folder as the `jar` file. You can check the sample [`application.yml`](./doc/application.yml).
+
+Each configuration key can have a different format depending if it's from the environment variable, or from the `application.yml` file. In the following section I will provide both format in the form `ENVIRONMENT_VARIABLE` / `application-property`.
+
+### Mandatory configuration
+
+In order to make Komga run, you need to specify some mandatory configuration keys:
+
+- `SPRING_PROFILES_ACTIVE` / `spring.profiles.active`: `prod` - this will enable the database management and upgrades for new versions.
+- `SPRING_DATASOURCE_URL` / `spring.datasource.url`: the path of the database file. For Docker I use `jdbc:h2:/config/database.h2;DB_CLOSE_DELAY=-1`, where `/config/database.h2` is the actual file inside the docker container. You can customize this part if running without docker.
+- `KOMGA_ROOT_FOLDER` /  `komga.root-folder`: the root folder of your library, this is what Komga will scan.
+- `KOMGA_ROOT_FOLDER_SCAN_CRON` / `komga.root-folder-scan-cron`: a [Spring cron expression](https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/scheduling/support/CronSequenceGenerator.html) for root folder periodic rescans. `0 0 * * * ?` will rescan every hour. `0 */15 * * * ?` will rescan every 15 minutes.
+
+### Optional configuration
+
+You can also use some optional configuration keys:
+
+- `KOMGA_USER_PASSWORD` / `komga.user-password`: the password for the user `user`. Defaults to `user`.
+- `KOMGA_ADMIN_PASSWORD` / `komga.admin-password`: the password for the user `admin`. Defaults to `admin`.
+- `KOMGA_THREADS_PARSE` / `komga.threads.parse`: the number of worker threads used for book parsing. Defaults to `2`. You can experiment to get better performance.
 
 ## Credits