//! Multi-file input and `#[cfg]` evaluation.
//!
//! The differential runner drives one `.rs` per case, so the multi-file path
//! and the feature-gating that goes with it are checked here instead. A Rust
//! crate splits across files with `mod`; Nim has no equivalent inside a single
//! output file, so the items are flattened in argument order.

use std::fs;
use std::path::{Path, PathBuf};
use std::process::Command;

const RUSTNIM: &str = env!("CARGO_BIN_EXE_rustnim");

fn work(name: &str) -> PathBuf {
    let d = Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/.work").join(name);
    let _ = fs::remove_dir_all(&d);
    fs::create_dir_all(&d).unwrap();
    d
}

fn run(dir: &Path, args: &[&str]) -> (bool, String, String) {
    let out = Command::new(RUSTNIM)
        .args(args)
        .env("TMPDIR", dir)
        .output()
        .expect("spawn rustnim");
    (
        out.status.success(),
        String::from_utf8_lossy(&out.stdout).into_owned(),
        String::from_utf8_lossy(&out.stderr).into_owned(),
    )
}

#[test]
fn files_are_flattened_into_one_module() {
    let d = work("multifile");
    let a = d.join("a.rs");
    let b = d.join("b.rs");
    fs::write(&a, "pub fn double(x: i32) -> i32 { x * 2 }\n").unwrap();
    fs::write(
        &b,
        "fn main() { println!(\"{}\", double(21)); }\n",
    )
    .unwrap();

    // `double` is defined in a.rs and called from b.rs: it resolves only
    // because both were passed in.
    let (ok, out, err) = run(&d, &[a.to_str().unwrap(), b.to_str().unwrap()]);
    assert!(ok, "multi-file transpile failed: {err}");
    assert!(out.contains("proc double"), "missing `double`:\n{out}");
    assert!(out.contains("proc main"), "missing `main`:\n{out}");

    // b.rs alone must fail rather than emit a call to something undefined.
    let (ok, _, err) = run(&d, &[b.to_str().unwrap()]);
    assert!(!ok, "b.rs alone should not transpile");
    assert!(err.contains("unknown function `double`"), "unexpected: {err}");
}

#[test]
fn cfg_is_evaluated_against_the_feature_set() {
    let d = work("cfg");
    let f = d.join("c.rs");
    fs::write(
        &f,
        "#[cfg(feature = \"extra\")]\n\
         fn extra() -> i32 { 1 }\n\
         #[cfg(not(feature = \"extra\"))]\n\
         fn plain() -> i32 { 2 }\n\
         fn main() {}\n",
    )
    .unwrap();

    let (ok, out, err) = run(&d, &[f.to_str().unwrap()]);
    assert!(ok, "{err}");
    assert!(!out.contains("proc extra"), "gated-off item was emitted:\n{out}");
    assert!(out.contains("proc plain"), "gated-on item missing:\n{out}");

    let (ok, out, err) = run(&d, &[f.to_str().unwrap(), "--cfg", "feature=extra"]);
    assert!(ok, "{err}");
    assert!(out.contains("proc extra"), "feature item missing:\n{out}");
    assert!(!out.contains("proc plain"), "`not(feature)` item was emitted:\n{out}");
}

#[test]
fn an_unevaluable_cfg_predicate_is_reported_not_assumed() {
    let d = work("cfg-unknown");
    let f = d.join("d.rs");
    fs::write(
        &f,
        "#[cfg(target_os = \"linux\")]\nfn only_linux() -> i32 { 1 }\nfn main() {}\n",
    )
    .unwrap();
    let (ok, _, err) = run(&d, &[f.to_str().unwrap()]);
    assert!(!ok, "an unevaluable cfg must not be silently resolved");
    assert!(err.contains("not a predicate rustnim can evaluate"), "unexpected: {err}");
}