// std.string (Ny) - Phase15 MVP
// Usage:
//   include "apps/std/string.hako"
//   StdStringNy.string_length("abc"), StdStringNy.string_concat("a","b"),
//   StdStringNy.string_slice("hello",1,4), StdStringNy.string_index_of("banana","na"), StdStringNy.string_equals("x","y")
// Notes:
//   - ASCII only; slice clamps [start,end)
//   - index_of returns -1 when not found
//   - Pure functions; no side effects

static box StdStringNy {
  // Return length of string s (Integer)
  string_length(s) {
    if s == null { return 0 }
    return s.length()
  }

  // Concatenate two strings
  string_concat(a, b) {
    return a.concat(b)
  }

  // Slice string in [start, end) with simple clamping
  string_slice(s, start, end) {
    if s == null { return "" }
    return s.substring(start, end)
  }

  // Return first index of substring (or -1)
  string_index_of(s, sub) {
    if s == null { return -1 }
    if sub == null { return 0 }
    local n, m, i
    n = s.length()
    m = sub.length()
    if m == 0 { return 0 }
    if n < m { return -1 }
    i = 0
    loop (i <= (n - m)) {
      // Compare window
      if s.substring(i, i + m) == sub { return i }
      i = i + 1
    }
    return -1
  }

  // Return 1 if equal else 0 (Integer)
  string_equals(a, b) {
    if a == b { return 1 }
    return 0
  }
}