Adding README

Signed-off-by: Mark Rossett <[email protected]>

Author: marosset

Justfile

@@ -4,7 +4,7 @@ build-adder:
 init-subtractor:
   cd components/subtractor && npm install 
 
-build-subtractor:
+build-subtractor: init-subtractor
   cd components/subtractor && npm run build:component 
 
 build-calculator:
@@ -22,12 +22,12 @@ build-component: build-adder build-subtractor build-calculator
 compile-wit:
   wasm-tools component wit {{ justfile_directory() }}/example/calculator-composed.wit -w -o {{ justfile_directory() }}/example/calculator-composed-world.wasm
 
-build-example:
+build-example: compile-wit
    cd example && \
      HYPERLIGHT_WASM_WORLD={{ justfile_directory() }}/example/calculator-composed-world.wasm \
      cargo build
 
-run-example:
+run-example: compile-wit
    cd example && \
      HYPERLIGHT_WASM_WORLD={{ justfile_directory() }}/example/calculator-composed-world.wasm \
      cargo run

README.md

@@ -1,8 +1,35 @@
-## Required tools
-
-- Rust toolchain
-- Node.js
-- wasm-tools
-- wac
-- wasi-virt
-- hyperlight-wasm-aot (needed?)
+# `hyperlight-wasm` calculator example
+
+THis is an example of a hyperlight-wasm application that runs a wasm component inside a hyperlight-sandbox that implements a calculator (similar to the component model example [here](https://github.com/bytecodealliance/component-docs/tree/main/component-model/examples/tutorial)).
+
+The [calculator](./wit/calculator.wit) itself is comprised of three wasm components:
+  - `calculator` - the main component that implements the calculator interface (written in Rust)
+  - `adder` - a component that implements the addition operation (written in Rust)
+  - `subtractor` - a component that implements the subtraction operation (written in Javascript)
+
+The [example](./example/) program loads the composed calculator/wasm component into a hyperlight-sandbox along with a wasm runtime and invokes functions as hyperlight-guest calls.
+
+## Requirements
+
+To build and run this example, you need the following tools installed on your system:
+
+- [Rust toolchain](https://www.rust-lang.org/tools/install) including `x86_unknown-none` target
+  - https://www.rust-lang.org/tools/install
+- [Node.js](https://nodejs.org/en/download) (to build the [subtractor](./components/subtractor/) wasm component)
+- [wasm-tools](https://github.com/bytecodealliance/wasm-tools?tab=readme-ov-file#installation)
+- [wac](https://github.com/bytecodealliance/wac?tab=readme-ov-file#installation)
+- [cargo component](https://github.com/bytecodealliance/cargo-component?tab=readme-ov-file#installation)
+- hyperlight-wasm-aot
+  - cargo install --git https://github.com/hyperlight-dev/hyperlight-wasm hyperlight-wasm-aot
+- [Just](https://github.com/casey/just?tab=readme-ov-file#installation)
+
+## Running the example
+
+- Build the guest component
+  ```bash
+  just build-component
+  ```
+- Run the example program
+  ```bash
+  just run-example
+  ```