sim-lib-stream-host 0.1.2

Host-device stream backend substrate for SIM streams.
Documentation 
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//! Deterministic cookbook builders for stream-host recipes.

use std::sync::Arc;

use sim_kernel::{Cx, DefaultFactory, EagerPolicy, Expr, NumberLiteral, Symbol};

use crate::{FakeBackend, HostBackend, HostBackendRegistry, stream_host_capability};

/// Build the modeled fake backend descriptor used by the cookbook recipe.
pub fn fake_backend_demo() -> Expr {
    let backend = FakeBackend::new();
    let inventory = backend.enumerate().expect("fake backend enumerates");
    let mut registry = HostBackendRegistry::new();
    registry.register(backend).expect("fake backend registers");
    let mut cx = authorized_demo_cx();
    let opened = registry
        .open_checked(
            &mut cx,
            FakeBackend::data_request(8).expect("valid fake data request"),
        )
        .expect("fake backend opens data stream");
    let config = opened.config();

    Expr::Map(vec![
        (field("kind"), sym("stream-host", "fake-backend")),
        (field("backend"), Expr::Symbol(config.backend().clone())),
        (field("device"), Expr::Symbol(config.device().clone())),
        (field("media"), Expr::Symbol(config.media().symbol())),
        (field("clock"), Expr::Symbol(config.clock().clock().clone())),
        (field("devices"), number(inventory.devices().len())),
        (field("ports"), number(inventory.ports().len())),
        (field("callback-queue"), sym("stream-host", "bounded")),
        (field("hardware-required"), Expr::Bool(false)),
    ])
}

fn field(name: &str) -> Expr {
    Expr::Symbol(Symbol::qualified("stream-host", name))
}

fn sym(namespace: &str, name: &str) -> Expr {
    Expr::Symbol(Symbol::qualified(namespace, name))
}

fn number(value: impl ToString) -> Expr {
    Expr::Number(NumberLiteral {
        domain: Symbol::qualified("numbers", "i64"),
        canonical: value.to_string(),
    })
}

#[allow(
    clippy::unit_arg,
    reason = "published sim-kernel grants return unit; workspace grants return Result"
)]
fn authorized_demo_cx() -> Cx {
    let (mut cx, seat) = Cx::new_seated(Arc::new(EagerPolicy), Arc::new(DefaultFactory));
    seat.grant(&mut cx, stream_host_capability())
        .assert_demo_granted();
    cx
}

trait DemoGrantResult {
    fn assert_demo_granted(self);
}

impl DemoGrantResult for () {
    fn assert_demo_granted(self) {}
}

impl<E: std::fmt::Display> DemoGrantResult for std::result::Result<(), E> {
    fn assert_demo_granted(self) {
        if let Err(err) = self {
            panic!("demo host grant is valid: {err}");
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use sim_codec::encode_with_codec;
    use sim_codec_lisp::LispCodecLib;
    use sim_lib_stream_core::StreamMedia;

    #[test]
    fn fake_backend_demo_opens_modeled_data_stream() {
        let Expr::Map(entries) = fake_backend_demo() else {
            panic!("fake backend demo is a map")
        };
        assert!(entries.iter().any(|(_, value)| {
            matches!(value, Expr::Symbol(symbol) if symbol.as_qualified_str() == "stream/media/data")
        }));
        assert!(entries.iter().any(|(_, value)| *value == Expr::Bool(false)));
        let mut registry = HostBackendRegistry::new();
        registry.register(FakeBackend::new()).expect("register");
        let mut cx = authorized_demo_cx();
        let opened = registry
            .open_checked(&mut cx, FakeBackend::data_request(4).expect("request"))
            .expect("open");
        assert_eq!(opened.config().media(), StreamMedia::Data);
    }

    #[test]
    fn fake_backend_recipe_expectation_matches_demo_output() {
        let mut cx = authorized_demo_cx();
        cx.load_lib(&sim_lib_numbers_i64::I64NumbersLib::new())
            .expect("load i64 numbers");
        let lisp = Symbol::qualified("codec", "lisp");
        let codec = LispCodecLib::new(cx.registry_mut().fresh_codec_id()).expect("lisp codec");
        cx.load_lib(&codec).expect("load lisp codec");

        let rendered = encode_with_codec(&mut cx, &lisp, &fake_backend_demo(), Default::default())
            .expect("encode fake backend demo")
            .into_text()
            .expect("lisp codec emits text");
        assert_eq!(recipe_expected_result(), rendered);
    }

    fn recipe_expected_result() -> String {
        let recipe = include_str!("../recipes/01-basics/fake-backend/recipe.toml");
        let result_line = recipe
            .lines()
            .find(|line| line.starts_with("result = "))
            .expect("recipe result line");
        result_line
            .strip_prefix("result = \"")
            .and_then(|line| line.strip_suffix('"'))
            .expect("quoted recipe result")
            .replace("\\\"", "\"")
    }
}