// upper_string_macro.hako
// MacroBoxSpec.expand: uppercase string literal values that start with "UPPER:" in AST JSON v0
// Contract: expand(json: string) -> string (AST JSON v0)

static box MacroBoxSpec {
  expand(json) {
    local s, out, i, plen, pat
    s = json
    out = ""
    i = 0
    pat = "\"value\":\"UPPER:"
    plen = pat.length()

    loop(i < s.length()) {
      // Match pattern: "value":"UPPER:
      if i + plen <= s.length() && s.substring(i, i + plen) == pat {
        // Emit the JSON key and opening quote: "value":"
        out = out + "\"value\":\""
        // Skip the pattern (drop the literal prefix UPPER:)
        i = i + plen
        // Uppercase until the closing quote (handle escapes conservatively)
        local j, ch, up
        j = i
        loop(j < s.length()) {
          ch = s.substring(j, j + 1)
          if ch == "\\" { // copy escaped char as-is
            if j + 1 < s.length() {
              out = out + s.substring(j, j + 2)
              j = j + 2
              continue
            }
          }
          if ch == "\"" {
            break
          }
          up = ch.toUpperCase()
          out = out + up
          j = j + 1
        }
        // Append the closing quote and advance pointer past it
        out = out + "\""
        i = j + 1
      } else {
        // Copy-through
        out = out + s.substring(i, i + 1)
        i = i + 1
      }
    }
    return out
  }
}