const std = @import("std");

/// Materialize terminal control characters as visible glyphs for failure output.
/// This is test/debug support only: product rendering still writes real CR/LF/ESC.
pub fn visibleControlsAlloc(allocator: std.mem.Allocator, bytes: []const u8) ![]u8 {
    var out = std.ArrayList(u8).empty;
    errdefer out.deinit(allocator);
    for (bytes) |byte| switch (byte) {
        '\r' => try out.appendSlice(allocator, "␍"),
        '\n' => try out.appendSlice(allocator, "␊\n"),
        0x1b => try out.appendSlice(allocator, "␛"),
        '\t' => try out.appendSlice(allocator, "⇥"),
        else => if (byte < 0x20) {
            try out.appendSlice(allocator, "␀");
        } else try out.append(allocator, byte),
    };
    return out.toOwnedSlice(allocator);
}

pub fn hasBareLf(bytes: []const u8) bool {
    for (bytes, 0..) |byte, i| {
        if (byte == '\n' and (i == 0 or bytes[i - 1] != '\r')) return true;
    }
    return false;
}

test "regular: visible terminal controls expose newline and escape bytes" {
    const debug = try visibleControlsAlloc(std.testing.allocator, "a\nb\r\n\x1b[31m");
    defer std.testing.allocator.free(debug);
    try std.testing.expectEqualStrings("a␊\nb␍␊\n␛[31m", debug);
}

test "adversarial: bare LF detector catches raw-mode skew risk" {
    try std.testing.expect(hasBareLf("a\nb"));
    try std.testing.expect(!hasBareLf("a\r\nb"));
}