rust_browser/tests/js_tests.rs

use js::{CaptureSink, JsEngine, JsValue};

fn engine_with_capture() -> JsEngine {
    let sink = CaptureSink::new();
    let mut engine = JsEngine::with_output(Box::new(sink));
    engine.prime_runtime().unwrap();
    engine
}

fn engine() -> JsEngine {
    let mut engine = JsEngine::new();
    engine.prime_runtime().unwrap();
    engine
}

#[test]
fn determinism_100_runs() {
    let script = r#"
        var x = 0;
        function inc(n) { return n + 1; }
        x = inc(x);
        x = inc(x);
        x = inc(x);
        x;
    "#;

    let mut results = Vec::new();
    for _ in 0..100 {
        let mut eng = engine();
        let val = eng.execute(script).unwrap();
        results.push(format!("{val}"));
    }

    let first = &results[0];
    assert!(
        results.iter().all(|r| r == first),
        "non-deterministic: got different results across 100 runs"
    );
    assert_eq!(first, "3");
}

#[test]
fn multi_script_state_persistence() {
    let mut eng = engine();
    eng.execute("var counter = 0;").unwrap();
    eng.execute("counter = counter + 1;").unwrap();
    eng.execute("counter = counter + 1;").unwrap();
    let val = eng.execute("counter;").unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 2.0));
}

#[test]
fn error_recovery_after_failure() {
    let mut eng = engine();

    // First execution fails (undefined variable)
    let err = eng.execute("nonexistent;");
    assert!(err.is_err());
    assert!(err.unwrap_err().is_reference_error());

    // Re-prime and try again
    eng.prime_runtime().unwrap();
    let val = eng.execute("42;").unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 42.0));
}

#[test]
fn large_script_many_statements() {
    let mut eng = engine();
    let mut script = String::from("var total = 0;\n");
    for i in 1..=50 {
        script.push_str(&format!("total = total + {i};\n"));
    }
    script.push_str("total;\n");

    let val = eng.execute(&script).unwrap();
    // Sum of 1..=50 = 1275
    assert!(matches!(val, JsValue::Number(n) if n == 1275.0));
}

#[test]
fn parse_error_classification() {
    let mut eng = engine();
    let err = eng.execute("var ;").unwrap_err();
    assert!(err.is_parse_error());
    assert!(!err.is_reference_error());
    assert!(!err.is_type_error());
    assert!(!err.is_runtime_error());
}

#[test]
fn runtime_error_classification() {
    let mut eng = engine();
    let err = eng.execute("missing_var;").unwrap_err();
    assert!(err.is_reference_error());
    assert!(!err.is_parse_error());
}

#[test]
fn console_log_output_captured() {
    let mut eng = engine_with_capture();
    eng.execute("console.log(\"hello\");").unwrap();
    eng.execute("console.log(1 + 2);").unwrap();
    eng.execute("console.log(\"a\", \"b\", \"c\");").unwrap();

    // We can't directly inspect the sink from here without downcasting,
    // but the test verifies no panics/errors occur during console.log execution.
}

#[test]
fn function_hoisting_works() {
    let mut eng = engine();
    let val = eng
        .execute("var r = greet(); function greet() { return \"hi\"; } r;")
        .unwrap();
    assert!(matches!(val, JsValue::String(ref s) if s == "hi"));
}

#[test]
fn nested_function_calls() {
    let mut eng = engine();
    let val = eng
        .execute(
            r#"
            function add(a, b) { return a + b; }
            function mul(a, b) { return a * b; }
            mul(add(2, 3), add(4, 1));
        "#,
        )
        .unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 25.0));
}

#[test]
fn empty_and_comment_scripts() {
    let mut eng = engine();
    let val = eng.execute("").unwrap();
    assert!(matches!(val, JsValue::Undefined));

    let val = eng.execute("// just a comment").unwrap();
    assert!(matches!(val, JsValue::Undefined));

    let val = eng.execute("/* block comment */").unwrap();
    assert!(matches!(val, JsValue::Undefined));
}

// --- Recursive call hits statement limit, not stack overflow ---

#[test]
fn finite_recursion_executes_correctly() {
    // A bounded recursion that terminates well within the statement limit
    // must return the correct value.
    let script = r#"
        function countdown(n) {
            if (n === 0) { return 0; }
            return countdown(n - 1);
        }
        countdown(50);
    "#;
    let mut eng = engine();
    let val = eng.execute(script).unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 0.0));
}

#[test]
fn recursive_function_hits_statement_limit_not_stack_overflow() {
    // An infinitely recursive function should be stopped by the statement
    // counter (producing a RuntimeError::Generic), never by a Rust stack
    // overflow.  The unit test in js_vm::interpreter::tests covers the case
    // where the limit is small enough (50) to fire before the stack runs out.
    // With the default limit (100,000), debug-mode stack frames are large
    // enough to exhaust the default 8 MiB stack, so run on a bigger thread.
    std::thread::Builder::new()
        .stack_size(16 * 1024 * 1024)
        .spawn(|| {
            let mut eng = engine();
            let err = eng
                .execute("function inf(n) { return inf(n + 1); } inf(0);")
                .unwrap_err();
            assert!(
                err.is_runtime_error(),
                "expected RuntimeError (statement limit) for infinite recursion, got: {err}"
            );
        })
        .unwrap()
        .join()
        .unwrap();
}

// --- typeof on undeclared variable returns "undefined" (spec-correct) ---

#[test]
fn typeof_undeclared_returns_undefined() {
    let mut eng = engine();
    let val = eng.execute("typeof totallyMissingVariable;").unwrap();
    assert!(
        matches!(val, JsValue::String(ref s) if s == "undefined"),
        "expected \"undefined\" for typeof on undeclared var, got: {val}"
    );
}

// --- var hoisting across un-taken if branches (end-to-end) ---

#[test]
fn var_hoisting_in_untaken_if_branch() {
    let mut eng = engine();
    // var declared inside a never-executed if block must be hoisted to the
    // enclosing scope per the JS spec.
    let val = eng.execute("if (false) { var x = 1; } x;").unwrap();
    assert!(
        matches!(val, JsValue::Undefined),
        "expected undefined (hoisted var x), got: {val}"
    );
}

#[test]
fn var_hoisting_in_else_branch_when_if_taken() {
    let mut eng = engine();
    // The else branch is not taken, so `b` is hoisted but never initialised.
    let val = eng
        .execute("if (true) { var a = 1; } else { var b = 2; } b;")
        .unwrap();
    assert!(
        matches!(val, JsValue::Undefined),
        "expected undefined (b hoisted from else), got: {val}"
    );
}

// --- Non-ASCII string literals round-trip through parse → execute ---

#[test]
fn non_ascii_string_executes_correctly() {
    let mut eng = engine();
    let val = eng.execute("\"café\";").unwrap();
    assert!(
        matches!(val, JsValue::String(ref s) if s == "café"),
        "expected café, got: {val}"
    );
}

#[test]
fn cjk_string_executes_correctly() {
    let mut eng = engine();
    let val = eng.execute("\"日本語\";").unwrap();
    assert!(
        matches!(val, JsValue::String(ref s) if s == "日本語"),
        "expected 日本語, got: {val}"
    );
}

// --- Chained member access returns TypeError (not crash) ---

#[test]
fn chained_member_access_returns_type_error() {
    // a.b.c — accessing a non-console member should produce a TypeError, not panic.
    let mut eng = engine();
    let err = eng.execute("var a = 1; a.b;").unwrap_err();
    assert!(
        err.is_type_error(),
        "expected TypeError for member access on number, got: {err}"
    );
}

// --- Empty function body ---

#[test]
fn empty_function_returns_undefined() {
    let mut eng = engine();
    let val = eng.execute("function noop() {} noop();").unwrap();
    assert!(matches!(val, JsValue::Undefined));
}

// --- Function with fewer args than params ---

#[test]
fn fewer_args_than_params_extra_are_undefined() {
    let mut eng = engine();
    let val = eng
        .execute("function f(a, b, c) { return c; } f(1, 2);")
        .unwrap();
    assert!(
        matches!(val, JsValue::Undefined),
        "expected undefined for missing third arg, got: {val}"
    );
}

// --- Function with more args than params ---

#[test]
fn more_args_than_params_extras_ignored() {
    let mut eng = engine();
    let val = eng
        .execute("function f(a) { return a; } f(42, 99, 100);")
        .unwrap();
    assert!(
        matches!(val, JsValue::Number(n) if n == 42.0),
        "expected 42, got: {val}"
    );
}

// --- Multiple return paths ---

#[test]
fn multiple_return_paths_execute_correctly() {
    let script = r#"
        function classify(n) {
            if (n > 0) { return "positive"; }
            else { return "non-positive"; }
        }
        classify(5);
    "#;
    let mut eng = engine();
    let val = eng.execute(script).unwrap();
    assert!(matches!(val, JsValue::String(ref s) if s == "positive"));

    let val = eng.execute("classify(-1);").unwrap();
    assert!(matches!(val, JsValue::String(ref s) if s == "non-positive"));
}

// --- Assignment to undeclared variable ---

#[test]
fn assignment_to_undeclared_variable_is_reference_error() {
    let mut eng = engine();
    let err = eng.execute("undeclaredVar = 42;").unwrap_err();
    assert!(
        err.is_reference_error(),
        "expected ReferenceError for assignment to undeclared variable, got: {err}"
    );
}

// --- Nested blocks with mixed var/let scoping ---

#[test]
fn nested_var_let_mixed_scoping() {
    let script = r#"
        var outer = 1;
        {
            var inner_var = 2;
            let inner_let = 3;
            outer = outer + inner_var + inner_let;
        }
        outer;
    "#;
    let mut eng = engine();
    let val = eng.execute(script).unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 6.0));
}

#[test]
fn let_not_visible_outside_block_integration() {
    let mut eng = engine();
    let err = eng
        .execute("{ let block_only = 5; } block_only;")
        .unwrap_err();
    assert!(
        err.is_reference_error(),
        "expected ReferenceError for let outside its block, got: {err}"
    );
}

// --- Function defined in script 1, called in script 2 ---

#[test]
fn function_defined_in_script1_called_in_script2() {
    let mut eng = engine();
    eng.execute("function greetName(name) { return \"hello_\" + name; }")
        .unwrap();
    let val = eng.execute("greetName(\"world\");").unwrap();
    assert!(
        matches!(val, JsValue::String(ref s) if s == "hello_world"),
        "expected hello_world, got: {val}"
    );
}

// --- Parse error in script 1 doesn't prevent script 2 from running ---

#[test]
fn parse_error_does_not_block_subsequent_script() {
    let mut eng = engine();
    // First script has a parse error
    let err = eng.execute("var ;");
    assert!(err.is_err());
    // Second script should work (VM never entered Failed state for parse errors)
    let val = eng.execute("42;").unwrap();
    assert!(matches!(val, JsValue::Number(n) if n == 42.0));
}

// --- Deep function call nesting (10+ levels, under 64 limit) ---

#[test]
fn deep_call_nesting_under_limit() {
    let mut eng = engine();
    let val = eng
        .execute(
            r#"
            function a(n) { if (n === 0) { return "done"; } return b(n - 1); }
            function b(n) { return a(n); }
            a(20);
        "#,
        )
        .unwrap();
    assert!(
        matches!(val, JsValue::String(ref s) if s == "done"),
        "expected done, got: {val}"
    );
}

// --- typeof in binary expression comparison ---

#[test]
fn typeof_in_equality_comparison() {
    let mut eng = engine();
    let val = eng.execute("typeof 42 === \"number\";").unwrap();
    assert!(
        matches!(val, JsValue::Boolean(true)),
        "expected true for typeof 42 === \"number\", got: {val}"
    );

    let val = eng.execute("typeof \"hello\" === \"string\";").unwrap();
    assert!(
        matches!(val, JsValue::Boolean(true)),
        "expected true for typeof \"hello\" === \"string\", got: {val}"
    );
}

// --- Multiple console.log calls with varied types ---

#[test]
fn switch_basic_case_match() {
    let mut eng = engine();
    let val = eng
        .execute("var r; switch(2) { case 1: r = 'one'; break; case 2: r = 'two'; break; } r;")
        .unwrap();
    assert_eq!(val.to_string(), "two");
}

#[test]
fn switch_default_case() {
    let mut eng = engine();
    let val = eng
        .execute("var r; switch(99) { case 1: r = 'one'; break; default: r = 'other'; break; } r;")
        .unwrap();
    assert_eq!(val.to_string(), "other");
}

#[test]
fn switch_fall_through_behavior() {
    let mut eng = engine();
    let val = eng
        .execute("var r = ''; switch(1) { case 1: r = r + 'a'; case 2: r = r + 'b'; } r;")
        .unwrap();
    assert_eq!(val.to_string(), "ab");
}

#[test]
fn switch_return_from_function() {
    let mut eng = engine();
    let val = eng
        .execute(
            "function f(x) { switch(x) { case 1: return 'one'; default: return 'other'; } } f(1);",
        )
        .unwrap();
    assert_eq!(val.to_string(), "one");
}

#[test]
fn switch_no_match_no_default_is_noop() {
    let mut eng = engine();
    let val = eng
        .execute("var r = 'init'; switch(99) { case 1: r = 'one'; break; } r;")
        .unwrap();
    assert_eq!(val.to_string(), "init");
}

#[test]
fn console_log_varied_types_no_panic() {
    // Verify console.log does not panic or error on any JsValue type.
    let mut eng = engine();
    eng.execute("console.log(undefined);").unwrap();
    eng.execute("console.log(null);").unwrap();
    eng.execute("console.log(true);").unwrap();
    eng.execute("console.log(false);").unwrap();
    eng.execute("console.log(0);").unwrap();
    eng.execute("console.log(\"\");").unwrap();
    eng.execute("console.log(\"hello\", \"world\");").unwrap();
    eng.execute("console.log(1, 2, 3, 4, 5);").unwrap();
}

// --- Loop tests ---

#[test]
fn for_loop_accumulates_sum() {
    let mut eng = engine();
    let val = eng
        .execute("var sum = 0; for (var i = 1; i <= 5; i++) { sum += i; } sum;")
        .unwrap();
    assert_eq!(val.to_string(), "15");
}

#[test]
fn while_loop_counts_to_five() {
    let mut eng = engine();
    let val = eng.execute("var n = 0; while (n < 5) { n++; } n;").unwrap();
    assert_eq!(val.to_string(), "5");
}

#[test]
fn do_while_runs_at_least_once() {
    let mut eng = engine();
    let val = eng
        .execute("var x = 0; do { x++; } while (false); x;")
        .unwrap();
    assert_eq!(val.to_string(), "1");
}

#[test]
fn for_loop_with_break() {
    let mut eng = engine();
    let val = eng
        .execute("var r = 0; for (var i = 0; i < 100; i++) { if (i === 7) { break; } r = i; } i;")
        .unwrap();
    assert_eq!(val.to_string(), "7");
}

#[test]
fn for_loop_with_continue() {
    let mut eng = engine();
    let val = eng
        .execute("var sum = 0; for (var i = 0; i < 10; i++) { if (i % 2 === 0) { continue; } sum += i; } sum;")
        .unwrap();
    assert_eq!(val.to_string(), "25");
}

#[test]
fn while_loop_with_break() {
    let mut eng = engine();
    let val = eng
        .execute("var n = 0; while (true) { n++; if (n >= 4) { break; } } n;")
        .unwrap();
    assert_eq!(val.to_string(), "4");
}

#[test]
fn increment_decrement_pre_post() {
    let mut eng = engine();
    let val = eng
        .execute("var a = 1; var b = a++; var c = ++a; b;")
        .unwrap();
    assert_eq!(val.to_string(), "1");
    let val = eng.execute("a;").unwrap();
    assert_eq!(val.to_string(), "3");
    let val = eng.execute("c;").unwrap();
    assert_eq!(val.to_string(), "3");
}

#[test]
fn compound_assignment_operators() {
    let mut eng = engine();
    let val = eng.execute("var x = 10; x += 5; x;").unwrap();
    assert_eq!(val.to_string(), "15");
    let val = eng.execute("x -= 3; x;").unwrap();
    assert_eq!(val.to_string(), "12");
    let val = eng.execute("x *= 2; x;").unwrap();
    assert_eq!(val.to_string(), "24");
}

#[test]
fn nested_for_loops() {
    let mut eng = engine();
    let val = eng
        .execute("var total = 0; for (var i = 0; i < 3; i++) { for (var j = 0; j < 3; j++) { total++; } } total;")
        .unwrap();
    assert_eq!(val.to_string(), "9");
}

#[test]
fn do_while_with_continue_integration() {
    let mut eng = engine();
    let val = eng
        .execute("var sum = 0; var i = 0; do { i++; if (i === 3) { continue; } sum += i; } while (i < 5); sum;")
        .unwrap();
    assert_eq!(val.to_string(), "12");
}