//! Iter 20a snapshot tests.
//!
//! For each `examples/<name>.ail.json`, the renderer's output is
//! compared against the committed `examples/<name>.prose.txt`. The
//! snapshot files are part of the repo: changing the renderer requires
//! a deliberate snapshot update, which is the point of this test.
//!
//! Update protocol (manual): regenerate the file by running
//! `cargo run -p ail -- prose <fixture>.ail.json > <fixture>.prose.txt`
//! once the renderer change is agreed; commit alongside the change.
//! There is no `UPDATE_SNAPSHOTS=1` environment short-cut here on
//! purpose — Iter 20a is the seeding round, and we want every change
//! after this to be visible in a diff.

use std::path::PathBuf;

fn examples_dir() -> PathBuf {
    // tests/ runs with CARGO_MANIFEST_DIR == crates/ailang-prose.
    let mut p = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    p.pop();
    p.pop();
    p.push("examples");
    p
}

fn check_snapshot(stem: &str) {
    let dir = examples_dir();
    let json_path = dir.join(format!("{stem}.ail.json"));
    let prose_path = dir.join(format!("{stem}.prose.txt"));

    let module = ailang_core::load_module(&json_path)
        .unwrap_or_else(|e| panic!("failed to load {json_path:?}: {e}"));
    let actual = ailang_prose::module_to_prose(&module);

    let expected = std::fs::read_to_string(&prose_path)
        .unwrap_or_else(|e| panic!("failed to read snapshot {prose_path:?}: {e}"));

    if actual != expected {
        // Write `.actual` for inspection, then fail.
        let actual_path = dir.join(format!("{stem}.prose.txt.actual"));
        std::fs::write(&actual_path, &actual).expect("write .actual");
        panic!(
            "prose snapshot mismatch for {stem}.\n\
             Expected: {prose_path:?}\n\
             Actual:   {actual_path:?}\n\
             To accept the new output, replace the expected file with the .actual file."
        );
    }
}

#[test]
fn snapshot_rc_own_param_drop() {
    check_snapshot("rc_own_param_drop");
}

#[test]
fn snapshot_rc_match_arm_partial_drop_leak() {
    check_snapshot("rc_match_arm_partial_drop_leak");
}

#[test]
fn snapshot_rc_app_let_partial_drop_leak() {
    check_snapshot("rc_app_let_partial_drop_leak");
}

/// Iter 20b: this fixture exercises the infix renderer + paren elision.
/// Pre-20b, the body had `if ==(n, 0) { ... }` and `tail sum_acc(-(n,
/// 1), ICons(-(n, 1), acc))`; after 20b those collapse to `if n == 0`
/// and `n - 1`. If this regresses, the renderer is broken.
#[test]
fn snapshot_bench_list_sum() {
    check_snapshot("bench_list_sum");
}