mod wasi;

use cranelift_codegen::settings;
use cranelift_native;
use wasmtime_jit::Context;

pub fn instantiate<S: AsRef<str>>(
    data: &[u8],
    bin_name: S,
    workspace: Option<S>,
) -> Result<(), String> {
    // Prepare runtime
    let isa_builder =
        cranelift_native::builder().map_err(|_| "host machine is not a supported target")?;
    let flag_builder = settings::builder();
    let isa = isa_builder.finish(settings::Flags::new(flag_builder));
    let mut context = Context::with_isa(isa);
    let global_exports = context.get_global_exports();

    let get_preopens = |workspace: Option<S>| -> Result<Vec<_>, String> {
        if let Some(workspace) = workspace {
            let preopen_dir = wasi_common::preopen_dir(workspace.as_ref()).map_err(|e| {
                format!(
                    "error while preopening directory '{}': {}",
                    workspace.as_ref(),
                    e
                )
            })?;

            Ok(vec![(".".to_owned(), preopen_dir)])
        } else {
            Ok(vec![])
        }
    };

    context.name_instance(
        "wasi_unstable".to_owned(),
        wasi::instantiate_wasi(
            "",
            global_exports,
            &get_preopens(workspace)?,
            &[bin_name.as_ref().to_owned(), ".".to_owned()],
            &[],
        )
        .expect("instantiating wasi"),
    );

    // Compile and instantiating a wasm module.
    context
        .instantiate_module(None, &data)
        .map(|_| ())
        .map_err(|e| {
            format!(
                "error while processing main module '{}': {}",
                bin_name.as_ref(),
                e
            )
        })
}