// ============================================================================
// Padding & alignment — left/right pad to a fixed width
// ============================================================================
//
// Builds padding by appending a fill character until the target width is met.
// Used to right-align numbers and left-align labels into fixed columns.
// Demonstrates while-loop string growth and truncation via substring.
//
// Run: soma run pad_align.cell --signal pad_left "42" 5

cell PadAlign {
    face {
        signal pad_left(s: String, width: Int) -> String
        signal pad_right(s: String, width: Int) -> String
        signal zero_pad(n: Int, width: Int) -> String
    }

    on pad_left(s: String, width: Int) {
        let out = s
        while len(out) < width {
            out = " " + out
        }
        return out
    }

    on pad_right(s: String, width: Int) {
        let out = s
        while len(out) < width {
            out = out + " "
        }
        return out
    }

    on zero_pad(n: Int, width: Int) {
        let out = to_string(n)
        while len(out) < width {
            out = "0" + out
        }
        return out
    }
}

cell test PadAlignTest {
    rules {
        assert pad_left("42", 5) == "   42"
        assert pad_right("ab", 4) == "ab  "
        assert zero_pad(7, 3) == "007"
        assert zero_pad(123, 2) == "123"
        assert len(pad_left("x", 10)) == 10
    }
}