//! Integration tests — compile every `.rpg` sample and validate stdout
//! against the accompanying `.rpg.golden` file.
//!
//! Each test follows the same three-step pipeline:
//!   1. `rust-langrpg -o <tmp> <sample>.rpg`   — compile
//!   2. `<tmp>`                                  — execute
//!   3. compare stdout with `<sample>.rpg.golden`
//!
//! # Adding a new sample
//!
//! Drop the `.rpg` source and a `.rpg.golden` file into `samples/` and add a
//! one-line `#[test]` that calls `run_sample("your_file.rpg")`.

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

/// Path to the freshly-built compiler binary, injected by Cargo.
const BIN: &str = env!("CARGO_BIN_EXE_rust-langrpg");

/// Absolute path to the `samples/` directory, resolved at compile time.
const SAMPLES_DIR: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/samples");

// ─────────────────────────────────────────────────────────────────────────────
// Shared driver
// ─────────────────────────────────────────────────────────────────────────────

/// Compile `sample_name` from `samples/`, run the resulting binary, and assert
/// that its stdout matches `samples/<sample_name>.golden` line-for-line.
///
/// Temp binaries are written to the OS temp directory with a name derived from
/// the sample so parallel test execution doesn't cause collisions.
fn run_sample(sample_name: &str) {
    let src = PathBuf::from(SAMPLES_DIR).join(sample_name);
    let golden_path = PathBuf::from(SAMPLES_DIR).join(format!("{}.golden", sample_name));

    assert!(
        src.exists(),
        "source file not found: {}",
        src.display()
    );
    assert!(
        golden_path.exists(),
        "golden file not found: {}\n\
         Create it with the expected stdout to enable this test.",
        golden_path.display()
    );

    // ── 1. Compile ────────────────────────────────────────────────────────────

    // Sanitise the stem so it is safe to embed in a file name (e.g. "for.rpg"
    // → "for_rpg") and prefix with a fixed string to make it easy to identify.
    let safe_stem = sample_name.replace('.', "_").replace(std::path::MAIN_SEPARATOR, "_");
    let exe = std::env::temp_dir().join(format!("rpg_sample_test_{}.out", safe_stem));

    let compile_out = Command::new(BIN)
        .args(["-o", exe.to_str().unwrap(), src.to_str().unwrap()])
        .output()
        .unwrap_or_else(|e| panic!("failed to spawn compiler for '{}': {e}", sample_name));

    assert!(
        compile_out.status.success(),
        "compilation of '{}' failed (exit {})\nstderr:\n{}",
        sample_name,
        compile_out.status,
        String::from_utf8_lossy(&compile_out.stderr),
    );

    assert!(
        exe.exists(),
        "compiler exited 0 for '{}' but no executable was produced at '{}'",
        sample_name,
        exe.display(),
    );

    // ── 2. Execute ────────────────────────────────────────────────────────────

    let run_out = Command::new(&exe)
        .output()
        .unwrap_or_else(|e| panic!("failed to run compiled binary for '{}': {e}", sample_name));

    assert!(
        run_out.status.success(),
        "binary for '{}' exited non-zero ({})\nstdout:\n{}\nstderr:\n{}",
        sample_name,
        run_out.status,
        String::from_utf8_lossy(&run_out.stdout),
        String::from_utf8_lossy(&run_out.stderr),
    );

    // ── 3. Compare against golden ─────────────────────────────────────────────

    let actual_raw = String::from_utf8_lossy(&run_out.stdout);
    let expected_raw = fs::read_to_string(&golden_path).unwrap_or_else(|e| {
        panic!("could not read golden file '{}': {e}", golden_path.display())
    });

    // Normalise both sides: trim trailing whitespace from every line and ignore
    // a trailing blank line, so golden files don't need a precise final newline.
    let normalise = |s: &str| -> Vec<String> {
        s.lines().map(|l| l.trim_end().to_string()).collect()
    };

    let actual_lines = normalise(&actual_raw);
    let expected_lines = normalise(&expected_raw);

    if actual_lines != expected_lines {
        let mut msg = format!(
            "stdout mismatch for '{}'\n\n\
             ── expected ({} line{}) ──────────────────────\n",
            sample_name,
            expected_lines.len(),
            if expected_lines.len() == 1 { "" } else { "s" },
        );
        for line in &expected_lines {
            msg.push_str("  ");
            msg.push_str(line);
            msg.push('\n');
        }
        msg.push_str(&format!(
            "\n── actual ({} line{}) ────────────────────────\n",
            actual_lines.len(),
            if actual_lines.len() == 1 { "" } else { "s" },
        ));
        for line in &actual_lines {
            msg.push_str("  ");
            msg.push_str(line);
            msg.push('\n');
        }

        // Highlight the first diverging line to make failures easy to spot.
        for (i, (exp, act)) in expected_lines.iter().zip(actual_lines.iter()).enumerate() {
            if exp != act {
                msg.push_str(&format!(
                    "\nfirst difference at line {}:\n  expected: {:?}\n  actual:   {:?}\n",
                    i + 1,
                    exp,
                    act,
                ));
                break;
            }
        }
        if actual_lines.len() != expected_lines.len() {
            msg.push_str(&format!(
                "\nline count differs: expected {}, got {}\n",
                expected_lines.len(),
                actual_lines.len(),
            ));
        }

        panic!("{}", msg);
    }
}

// ─────────────────────────────────────────────────────────────────────────────
// One #[test] per sample
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn sample_hello() {
    run_sample("hello.rpg");
}

#[test]
fn sample_for() {
    run_sample("for.rpg");
}

#[test]
fn sample_fib() {
    run_sample("fib.rpg");
}