// Phase 164: Test trim_trailing from JsonParserBox (Pattern3 with if-else PHI + break)
// Simulates: loop(end > start) { if is_whitespace(ch) { end-- } else { break } }

static box Main {
  main(args) {
    // Simulate trimming trailing whitespace
    local s = "hello world   \t\n"
    local start = 0
    local end = s.length()

    // Loop with if-else PHI: end is updated conditionally with break
    // Note: working backwards from end
    loop(end > start) {
      local ch = s.substring(end - 1, end)
      // Check if whitespace
      local is_ws = 0
      if ch == " " {
        is_ws = 1
      } else if ch == "\t" {
        is_ws = 1
      } else if ch == "\n" {
        is_ws = 1
      } else if ch == "\r" {
        is_ws = 1
      }

      if is_ws == 1 {
        end = end - 1
      } else {
        break
      }
    }

    // Output result
    local trimmed = s.substring(start, end)
    print("Trimmed trailing whitespace")
    print("End position: " + ("" + end))
    print("Trimmed string: " + trimmed)
    print("Expected end: 11")
    print("Expected string: hello world")
    return 0
  }
}