// ============================================================================
// 018 — String Builder Pattern
// ============================================================================
// Demonstrates building strings with += (append) and concat.
//
// Run:   soma run 018_string_builder.cell run
// Expect:
//   CSV: name,age,city
//   Alice,30,Paris
//   Bob,25,London
//   Carol,35,Tokyo
//
//   Reversed: edcba
//   Repeated: *****

cell StringBuilder {

    on run() {
        // += appends to a string
        let csv = "name,age,city"
        csv += "\nAlice,30,Paris"
        csv += "\nBob,25,London"
        csv += "\nCarol,35,Tokyo"
        print("CSV: {csv}")

        print("")

        // Reversing a string character by character
        let original = "abcde"
        let reversed = ""
        let i = len(original) - 1
        while i >= 0 {
            let ch = substring(original, i, i + 1)
            reversed += ch
            i = i - 1
        }
        print("Reversed: {reversed}")

        // Repeating a character N times
        let star = ""
        let count = 0
        while count < 5 {
            star += "*"
            count = count + 1
        }
        print("Repeated: {star}")

        return "done"
    }
}