//! RED-pin for the instance-method-body unbound-var bug observed in
//! the 2026-05-13 fieldtest of milestone-24 (Form-A authoring).
//!
//! Property protected: `check_def` walks `Def::Instance` method bodies
//! through the same identifier-resolution path as `Def::Fn` bodies, so
//! an unbound identifier inside an instance-method lambda body fires
//! `[unbound-var]` at `ail check`, with exit code 1, BEFORE the
//! monomorphisation pass runs. Without this, an unbound identifier
//! inside an instance-method body slips past `ail check` (false-OK)
//! and surfaces later at `ail build` as a degraded internal-error
//! diagnostic ("monomorphise_workspace: unknown identifier: <name>"),
//! with no source location, no symbol kind, and no "did you mean ...?".
//!
//! Pre-fix observed behaviour (the bug):
//! - `ail check` exits 0 with `ok (23 symbols across 2 modules)`.
//! - `ail build` exits 1 with
//!   `Error: monomorphise_workspace: unknown identifier: \`format_label\``.
//!
//! Post-fix expected behaviour:
//! - `ail check` exits 1 with an `[unbound-var]` error naming
//!   `format_label`. The mono pass never runs because check fails first.
//!
//! Root cause (from debugger Phase 1-2):
//! `crates/ailang-check/src/lib.rs::check_def` early-returns `Ok(())`
//! for `Def::Class | Def::Instance` (the comment claims body
//! typechecking landed alongside the typeclass-typecheck arms, but
//! the body-walk was never wired). Only the workspace-load coherence
//! checks
//! (Orphan/Duplicate/MissingMethod) in `workspace::build_registry`
//! touch instance defs, and those only inspect the schema, not the
//! method-body identifier graph.
//!
//! Fixture: `examples/bug_unbound_in_instance_method.ail`. The fixture
//! uses `format_label` (NOT a builtin) inside an instance-method lambda;
//! `int_to_str` IS a builtin and is correctly resolved. The fixture
//! parses cleanly — the only error is the unbound `format_label` in the
//! method body.

use std::path::Path;
use std::process::Command;

fn ail_bin() -> &'static str {
    env!("CARGO_BIN_EXE_ail")
}

/// RED today: `ail check` on `bug_unbound_in_instance_method.ail`
/// must exit non-zero and emit `[unbound-var]` naming `format_label`,
/// matching the diagnostic shape produced at fn-body level.
///
/// Pre-fix, this test fails because `ail check` exits 0 and prints
/// `ok (23 symbols across 2 modules)`.
#[test]
fn check_fires_unbound_var_for_format_label_in_instance_method_body() {
    let manifest_dir = env!("CARGO_MANIFEST_DIR");
    let workspace = Path::new(manifest_dir).parent().unwrap().parent().unwrap();
    let src = workspace
        .join("examples")
        .join("bug_unbound_in_instance_method.ail");
    assert!(
        src.exists(),
        "fixture missing: {} — RED test requires the .ail fixture in working tree",
        src.display()
    );

    let output = Command::new(ail_bin())
        .args(["check", src.to_str().unwrap()])
        .output()
        .expect("ail check failed to spawn");
    let code = output.status.code().expect("process terminated by signal");
    let stdout = String::from_utf8_lossy(&output.stdout);
    let stderr = String::from_utf8_lossy(&output.stderr);
    let combined = format!("STDOUT:\n{stdout}\nSTDERR:\n{stderr}");

    assert_ne!(
        code, 0,
        "ail check must exit non-zero for an unbound identifier inside \
         an instance-method body; got exit 0. {combined}"
    );
    assert!(
        combined.contains("unbound-var"),
        "ail check must emit diagnostic code `unbound-var`; \
         got: {combined}"
    );
    assert!(
        combined.contains("format_label"),
        "diagnostic must name the unbound identifier `format_label`; \
         got: {combined}"
    );
    assert!(
        !combined.contains("monomorphise_workspace"),
        "the degraded mono-pass diagnostic must NOT surface — \
         `ail check` should reject the program before mono runs; \
         got: {combined}"
    );
}

/// Companion RED: also assert the `--json` shape. The fn-body level
/// already emits `{"severity":"error","code":"unbound-var"}` via
/// `check_json_unbound_var` in `e2e.rs`; the instance-method-body
/// path must produce the same structured shape.
#[test]
fn check_json_unbound_var_in_instance_method_body() {
    let manifest_dir = env!("CARGO_MANIFEST_DIR");
    let workspace = Path::new(manifest_dir).parent().unwrap().parent().unwrap();
    let src = workspace
        .join("examples")
        .join("bug_unbound_in_instance_method.ail");

    let output = Command::new(ail_bin())
        .args(["check", src.to_str().unwrap(), "--json"])
        .output()
        .expect("ail check --json failed to spawn");
    let code = output.status.code().expect("process terminated by signal");
    let stdout = String::from_utf8_lossy(&output.stdout).into_owned();
    let stderr = String::from_utf8_lossy(&output.stderr).into_owned();
    let combined = format!("STDOUT:\n{stdout}\nSTDERR:\n{stderr}");

    assert_eq!(
        code, 1,
        "ail check --json must exit 1; got {code}. {combined}"
    );

    // Stdout must be a JSON array containing at least one
    // unbound-var error diagnostic.
    let diags: serde_json::Value = serde_json::from_str(stdout.trim())
        .unwrap_or_else(|e| panic!("stdout must be JSON; parse error: {e}; got: {stdout}"));
    let arr = diags.as_array().expect("diagnostics must be a JSON array");
    assert!(
        arr.iter().any(|d| {
            d.get("severity").and_then(|v| v.as_str()) == Some("error")
                && d.get("code").and_then(|v| v.as_str()) == Some("unbound-var")
                && d.to_string().contains("format_label")
        }),
        "expected an error diagnostic with code `unbound-var` naming \
         `format_label`; got: {stdout}"
    );
}
