use std::{
    ffi::OsStr,
    fs,
    path::{Path, PathBuf},
    process::{Command, Output},
    sync::atomic::{AtomicUsize, Ordering},
};

static NEXT_TEMP_ID: AtomicUsize = AtomicUsize::new(0);

const EXPECTED_TEST_OUTPUT: &str = concat!(
    "test \"stdlib composition reads parses and cleans\" ... ok\n",
    "test \"stdlib composition clamps and squares\" ... ok\n",
    "test \"stdlib composition main score\" ... ok\n",
    "3 test(s) passed\n",
);

#[test]
fn stdlib_composition_project_checks_tests_docs_and_runs() {
    let compiler_root = Path::new(env!("CARGO_MANIFEST_DIR"));
    let repo_root = compiler_root.parent().expect("compiler has repo parent");
    let project = repo_root.join("examples/projects/stdlib-composition");
    let source = read(&project.join("src/main.slo"));

    assert!(
        !project.join("src/fs.slo").exists()
            && !project.join("src/string.slo").exists()
            && !project.join("src/math.slo").exists()
            && !project.join("src/io.slo").exists(),
        "stdlib composition must use repo-root std imports, not local module copies"
    );
    assert!(
        source.contains(
            "(import std.fs (write_text_status read_text_result exists is_file remove_file_ok))"
        ) && source.contains("(import std.string (concat parse_i32_result))")
            && source.contains("(import std.math (clamp_i32 square_i32))")
            && source.contains("(import std.io (print_i32_zero))"),
        "stdlib composition fixture must compose several explicit std imports"
    );
    assert!(
        source.contains("(fn score_file_roundtrip_ok")
            && source.contains("(fn computed_score")
            && source.contains("(fn main_score")
            && source.contains("(fn cleanup_score_file"),
        "stdlib composition fixture must keep realistic read/parse/compute/cleanup flow visible"
    );

    let fmt = run_glagol([
        OsStr::new("fmt"),
        OsStr::new("--check"),
        project.as_os_str(),
    ]);
    assert_success("stdlib composition fmt --check", &fmt);

    let check = run_glagol([OsStr::new("check"), project.as_os_str()]);
    assert_success_stdout(check, "", "stdlib composition check");

    let test_cwd = temp_root("test");
    let test = run_glagol_in([OsStr::new("test"), project.as_os_str()], &test_cwd);
    assert_success_stdout(test, EXPECTED_TEST_OUTPUT, "stdlib composition test");
    assert!(
        !test_cwd.join("slovo-stdlib-composition-beta.txt").exists(),
        "stdlib composition tests must clean their file fixture"
    );

    let docs = temp_root("docs");
    let doc = run_glagol([
        OsStr::new("doc"),
        project.as_os_str(),
        OsStr::new("-o"),
        docs.as_os_str(),
    ]);
    assert_success("stdlib composition doc", &doc);
    let doc_index = read(&docs.join("index.md"));
    assert!(doc_index.contains("## Module main"));
    assert!(doc_index.contains("- `computed_score"));
    assert!(doc_index.contains("- `stdlib composition clamps and squares`"));

    let run_cwd = temp_root("run");
    let run = run_glagol_in([OsStr::new("run"), project.as_os_str()], &run_cwd);
    if run.status.success() {
        assert_eq!(String::from_utf8_lossy(&run.stdout), "100\n");
        assert!(
            run.stderr.is_empty(),
            "stdlib composition run wrote stderr:\n{}",
            String::from_utf8_lossy(&run.stderr)
        );
        assert!(
            !run_cwd.join("slovo-stdlib-composition-beta.txt").exists(),
            "stdlib composition run must clean its file fixture"
        );
    } else {
        assert_stderr_contains("stdlib composition run", &run, "ToolchainUnavailable");
    }
}

fn run_glagol<I, S>(args: I) -> Output
where
    I: IntoIterator<Item = S>,
    S: AsRef<std::ffi::OsStr>,
{
    run_glagol_in(args, Path::new(env!("CARGO_MANIFEST_DIR")))
}

fn run_glagol_in<I, S>(args: I, cwd: &Path) -> Output
where
    I: IntoIterator<Item = S>,
    S: AsRef<std::ffi::OsStr>,
{
    fs::create_dir_all(cwd).expect("create command cwd");
    Command::new(env!("CARGO_BIN_EXE_glagol"))
        .args(args)
        .current_dir(cwd)
        .output()
        .expect("run glagol")
}

fn temp_root(name: &str) -> PathBuf {
    let id = NEXT_TEMP_ID.fetch_add(1, Ordering::Relaxed);
    let nanos = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .expect("system clock before UNIX_EPOCH")
        .as_nanos();
    std::env::temp_dir().join(format!(
        "glagol-stdlib-composition-{}-{}-{}-{}",
        std::process::id(),
        nanos,
        id,
        name
    ))
}

fn read(path: &Path) -> String {
    fs::read_to_string(path).unwrap_or_else(|err| panic!("read `{}`: {}", path.display(), err))
}

fn assert_success(context: &str, output: &Output) {
    assert!(
        output.status.success(),
        "{} failed\nstatus: {:?}\nstdout:\n{}\nstderr:\n{}",
        context,
        output.status.code(),
        String::from_utf8_lossy(&output.stdout),
        String::from_utf8_lossy(&output.stderr)
    );
}

fn assert_success_stdout(output: Output, expected: &str, context: &str) {
    assert_success(context, &output);
    assert_eq!(
        String::from_utf8_lossy(&output.stdout),
        expected,
        "{}",
        context
    );
}

fn assert_stderr_contains(context: &str, output: &Output, needle: &str) {
    let stderr = String::from_utf8_lossy(&output.stderr);
    assert!(
        stderr.contains(needle),
        "{} stderr did not contain `{}`:\n{}",
        context,
        needle,
        stderr
    );
}