//! Example of instantiating of the WebAssembly module and
//! invoking its exported function.

use anyhow::{format_err, Result};
use std::fs::read;
use wasmtime_api::*;

fn main() -> Result<()> {
    let wasm = read("examples/gcd.wasm")?;

    // Instantiate engine and store.
    let engine = HostRef::new(Engine::default());
    let store = HostRef::new(Store::new(&engine));

    // Load a module.
    let module = HostRef::new(Module::new(&store, &wasm)?);

    // Find index of the `gcd` export.
    let gcd_index = module
        .borrow()
        .exports()
        .iter()
        .enumerate()
        .find(|(_, export)| export.name().to_string() == "gcd")
        .unwrap()
        .0;

    // Instantiate the module.
    let instance = HostRef::new(Instance::new(&store, &module, &[])?);

    // Invoke `gcd` export
    let gcd = instance.borrow().exports()[gcd_index]
        .func()
        .expect("gcd")
        .clone();
    let result = gcd
        .borrow()
        .call(&[Val::from(6i32), Val::from(27i32)])
        .map_err(|e| format_err!("call error: {:?}", e))?;

    println!("{:?}", result);
    Ok(())
}