chore: update readme (#103)

README.md

@@ -1,5 +1,114 @@
+# Marine Rust SDK
 [![crates.io version](https://img.shields.io/crates/v/marine-rs-sdk?color=green)](https://crates.io/crates/marine-rs-sdk)
 
-## Marine Rust SDK
+This SDK empowers developers to create general-purpose Wasm modules and combine them in a multi-module setup with the help of [interface-types](https://github.com/WebAssembly/interface-types) and a [shared-nothing linking](https://training.linuxfoundation.org/blog/how-and-why-to-link-webassembly-modules/) scheme. The SDK provides all necessary macros and other features to make Wasm developing process as close as possible to the one with the "vanilla" Rust. Compiled modules are intended to run with the [Marine](https://github.com/fluencelabs/marine) runtime.
+
+
+## Usage
+
+The core component of the SDK is the `#[marine]` macro that should be used with export functions, extern blocks, and structures. Let's consider a simple scenario with a module with one export function:
+```rust
+#[marine]
+use marine_rs_sdk::marine;
+use marine_rs_sdk::module_manifest;
+
+#[marine]
+pub fn greeting(name: String) -> String {
+    format!("Hi, {}", name)
+}
+```
+This code imports the Marine SDK and wraps the greeting function with the `#[marine]` macro. Every function wrapped in such way will be exported from a compiled Wasm module.
+
+To compile this code to Wasm, you need the Marine CLI tool. If you haven't installed the cli already, use `cargo install marine`:
+
+```bash
+marine build --release
+```
+
+Finally, you obtain a build manifest embedded into a Wasm binary and can interact with a module in the Marine REPL (mrepl). If you don't have it, install it with `cargo install mrepl`:
+
+```bash
+> marine info ./target/wasm32-wasi/release/greeting.wasm
+it version:  0.23.1
+sdk version: 0.7.0
+authors:     <user-name>
+version:     0.1.0
+description:
+repository:
+build time:  2023-02-15 18:52:37.865550 +00:00 UTC
+
+> mrepl --quiet
+1> load greeting ./target/wasm32-wasi/release/greeting.wasm
+module successfully loaded into App service
+elapsed time: 52.153308ms
+
+2> interface
+Application service interface:
+greeting:
+  fn greeting(name: String) -> String
+
+3> call greeting greeting "user"
+result: String("Hi, user")
+ elapsed time: 132.021µs
+```
+
+The complete guide of developing this simple module can be found [here](https://fluence.dev/docs/marine-book/quick-start/develop-a-single-module-service).
+
+
+## SDK components
+
+The SDK exports the following major components:
+- `#[marine]` procedure macro that can be applied to
+    - [function](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/export-functions) making it export from a module
+    - [external block](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/import-functions) making it imported from a module in a Marine-suitable way
+    - [structure](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/structures), making it usable as an argument of an export or an import function
+- [call parameters interface](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/call-parameters) intended to provide a set of module start parameters
+- [mounted binaries interface](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/mounted-binaries) that can be used to call a CLI tool
+- [module_manifest](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/module-manifest) macro intended to embed some info into a compiled Wasm
+- [logging stuff](https://fluence.dev/docs/marine-book/marine-rust-sdk/developing/logging) that allows adjusting a Marine logging mechanism
+
+
+## Supported Rust types
+
+At the moment, the `#[marine]` macro allows the following Rust types as an argument of export and import functions or the field of a structure:
+- one of the following Rust basic types: `bool`, `u8`, `u16`, `u32`, `u64`, `i8`, `i16`, `i32`, `i64`, `f32`, `f64`
+- strings `String`, `&str`
+- a vector of elements of the above types
+- a vector composed of vectors of the above type, where recursion is acceptable, e.g., the type `Vec<Vec<Vec<u8>>>` is permissible
+- a reference of all of the above types
+- a structure where all fields are of the basic Rust types
+- a structure where all fields are of the above types or other structures build with such a way
+
+
+## Documentation
+
+- [Marine Book](https://fluence.dev/docs/marine-book/introduction)
+- [Marine Examples](https://github.com/fluencelabs/examples/tree/main/marine-examples)
+- [Quickstart](https://fluence.dev/docs/marine-book/quick-start/)
+
+
+## Repository structure
+
+- **[crates](./crates)**
+    - [macro-testing-utils](./crates/macro-testing-utils) - internal testing utils
+    - [main](./crates/main) - contains export_allocator, logger and results modules
+    - [marine-macro](./crates/marine-macro) - proc-macro crate for the `#[marine]` macro
+    - [marine-macro-impl](./crates/marine-macro-impl) - the actual realization of the `#[marine]` macro
+    - [timestamp-macro](./crates/timestamp-macro) - a macro to support timestamp embedding into a compiled Wasm binary
+- **[src](./src)** - contains call_parameters and mounted_binary modules along with reexporting all necessary for a user stuff
+
+
+## Support
+
+Please, [file an issue](https://github.com/fluencelabs/marine-rs-sdk/issues) if you find a bug. You can also contact us at [Discord](https://discord.com/invite/5qSnPZKh7u) or [Telegram](https://t.me/fluence_project). We will do our best to resolve the issue ASAP.
+
+
+## Contributing
+
+Any interested person is welcome to contribute to the project. Please, make sure you read and follow some basic [rules](./CONTRIBUTING.md).
+
+
+## License
+
+All software code is copyright (c) Fluence Labs, Inc. under the [Apache-2.0](./LICENSE) license.
 
-This SDK is intended to run backend application on the Fluence network with [Marine](https://github.com/fluencelabs/marine) runtime. More information about usage and some internals could found in [docs](https://fluence.dev/docs/marine-book/marine-rust-sdk/).