feat: readme (prep for cargo publish)

README.md

@@ -1,2 +1,107 @@
 # rsnbs
-A simple rust library to read and write .nbs files from Note Block Studio.
+
+> A simple rust library to read and write [.nbs files](https://opennbs.org/nbs)
+> from [Open Note Block Studio](https://opennbs.org/).
+
+`rsnbs` has all the functionality `pynbs` has, like iterating over Note Block Studio songs
+```rust
+use rsnbs::read_nbs;
+
+let song = read_nbs("song.nbs");
+for note in song.notes {
+  println!("tick: {}, instrument: {}", note.tick.unwrap(), note.instrument.unwrap())
+}
+```
+
+or generating new songs programmatically
+```rust
+use rsnbs::{Song, Note};
+
+let song = Song::default();
+for i in 0..10 {
+  Song.notes.push(Note {
+    tick: Some(i), layer: None, instrument: None,
+    velocity: 30, panning: None, pitch: None, key: Some(i+35)
+  })
+}
+```
+the main difference is that every field is an option (for version differences sake) where None acts as 0/"".
+
+## Installation
+
+The package can be installed with `cargo`
+```bash
+$ cargo install rsnbs
+```
+
+## Reading / Writing
+You can use the read_nbs function to read an parse a specific NBS file of any version.
+```rust
+  let song = rsnbs::read_nbs("song.nbs");
+```
+This returns a rsnbs::Song object wich can then be written using Song::save
+```rust
+  song.save("song.nbs", version);
+```
+
+## Song struct
+Song implements the Default trait so you can instance a default with 1 layer and all None fields
+```rust
+  let song = Song::default();
+```
+### Fields
+#### Header
+the first field is `header`, the file header, of type struct `Header`
+Attribute                   | Type    | Details
+:---------------------------|:--------|:------------------------------------------------
+`header.version`            | `i8`   | The NBS version this file was saved on.
+`header.default_instruments`| `i8`   | The amount of instruments from vanilla Minecraft in the song.
+`header.song_length`        | `i16`   | The length of the song, measured in ticks.
+`header.song_layers`        | `i16`   | The ID of the last layer with at least one note block in it.
+`header.song_name`          | `String`   | The name of the song.
+`header.song_author`        | `String`   | The author of the song.
+`header.original_author`    | `String`   | The original song author of the song.
+`header.description`        | `String`   | The description of the song.
+`header.tempo`              | `i16` | The tempo of the song multiplied by 100.
+`header.auto_save`          | `bool`  | Whether auto-saving has been enabled.
+`header.auto_save_duration` | `i8`   | The amount of minutes between each auto-save.
+`header.time_signature`     | `i8`   | The time signature of the song.
+`header.minutes_spent`      | `i32`   | The amount of minutes spent on the project.
+`header.left_clicks`        | `i32`   | The amount of times the user has left-clicked.
+`header.right_clicks`       | `i32`   | The amount of times the user has right-clicked.
+`header.blocks_added`       | `i32`   | The amount of times the user has added a block.
+`header.blocks_removed`     | `i32`   | The amount of times the user has removed a block.
+`header.song_origin`        | `String`   | The file name of the original MIDI or schematic.
+`header.loop`               | `bool`  | Whether the song should loop back to the start after ending.
+`header.max_loop_count`     | `i8`   | The amount of times to loop. 0 = infinite.
+`header.loop_start`         | `i16`   | The tick the song will loop back to at the end of playback.
+
+#### Notes
+the `notes` field has all the notes of type struct `Note` stored in a vec in order
+Attribute         | Type  | Details
+:---------------- |:------|:------------------------------------------------
+`note.tick`       | `i32` | The tick at which the note plays.
+`note.layer`      | `i32` | The ID of the layer in which the note is placed.
+`note.instrument` | `i8` | The ID of the instrument.
+`note.key`        | `i8` | The key of the note. (between 0 and 87)
+`note.velocity`   | `i8` | The velocity of the note. (between 0 and 100)
+`note.panning`    | `u8` | The stereo panning of the note. (between -100 and 100)
+`note.pitch`      | `i16` | The detune of the note, in cents. (between -1200 and 1200)
+
+#### Layers 
+the `layers` field is a vec of all layers of type struct `Layer` in order
+Attribute         | Type  | Details
+:-----------------|:------|:------------------------
+`layer.name`      | `String` | The name of the layer.
+`layer.lock`      | `bool`| Whether the layer is locked.
+`layer.volume`    | `i8` | The volume of the layer.
+`layer.panning`   | `u8` | The stereo panning of the layer.
+
+#### Instruments
+the `instruments` field stores all the custom instruments of the song in order in a vec
+Attribute              | Type   | Details
+:----------------------|:-------|:----------------------------------------------------------
+`instrument.name`      | `String`  | The name of the instrument.
+`instrument.file`      | `String`  | The name of the sound file of the instrument.
+`instrument.pitch`     | `i8`  | The pitch of the instrument. (between 0 and 87)
+`instrument.press_key` | `bool` | Whether the piano should automatically press keys with the instrument when the marker passes them.